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Sample records for close circumstellar environment

  1. The close circumstellar environment of Betelgeuse - III. SPHERE/ZIMPOL visible polarimetry of the inner envelope and photosphere

    CERN Document Server

    Kervella, P; Montargès, M; Ridgway, S T; Chiavassa, A; Haubois, X; Schmid, H -M; Langlois, M; Gallenne, A; Perrin, G

    2016-01-01

    The physical mechanism through which the outgoing material of massive red supergiants is accelerated above the escape velocity is unclear. Thanks to the transparency of its circumstellar envelope, the nearby red supergiant Betelgeuse gives the opportunity to probe the innermost layers of the envelope of a typical red supergiant down to the photosphere, i.e. where the acceleration of the wind is expected to occur. We took advantage of the SPHERE/ZIMPOL adaptive optics imaging polarimeter to resolve the visible photosphere and close envelope of Betelgeuse. We detect an asymmetric gaseous envelope inside a radius of 2 to 3 times the near-infrared photospheric radius of the star (R*), and a significant Halpha emission mostly contained within 3 R*. From the polarimetric signal, we also identify the signature of dust scattering in an asymmetric and incomplete dust shell located at a similar radius. The presence of dust so close to the star may have a significant impact on the wind acceleration through radiative pre...

  2. The close circumstellar environment of Betelgeuse - Adaptive optics spectro-imaging in the near-IR with VLT/NACO

    CERN Document Server

    Kervella, Pierre; Ridgway, Stephen T; Perrin, Guy; Lacour, Sylvestre; Cami, Jan; Haubois, Xavier

    2009-01-01

    Context: Betelgeuse is one the largest stars in the sky in terms of angular diameter. Structures on the stellar photosphere have been detected in the visible and near-infrared as well as a compact molecular environment called the MOLsphere. Mid-infrared observations have revealed the nature of some of the molecules in the MOLsphere, some being the precursor of dust. Aims: Betelgeuse is an excellent candidate to understand the process of mass loss in red supergiants. Using diffraction-limited adaptive optics (AO) in the near-infrared, we probe the photosphere and close environment of Betelgeuse to study the wavelength dependence of its extension, and to search for asymmetries. Methods: We obtained AO images with the VLT/NACO instrument, taking advantage of the "cube" mode of the CONICA camera to record separately a large number of short-exposure frames. This allowed us to adopt a "lucky imaging" approach for the data reduction, and obtain diffraction-limited images over the spectral range 1.04-2.17 $\\mu$m in 1...

  3. The complex circumstellar environment of HD 142527

    NARCIS (Netherlands)

    Verhoeff, A.P.; Min, M.; Pantin, E.; Waters, L.B.F.M.; Tielens, A.G.G.M.; Honda, M.; Fujiwara, H.; Bouwman, J.; van Boekel, R.; Dougherty, S.M.; de Koter, A.; Dominik, C.; Mulders, G.D.

    2011-01-01

    Context. The recent findings of gas giant planets around young A-type stars suggest that disks surrounding Herbig Ae/Be stars will develop planetary systems. An interesting case is HD 142527, for which previous observations revealed a complex circumstellar environment and an unusually high ratio of

  4. The complex circumstellar environment of HD 142527

    NARCIS (Netherlands)

    Verhoeff, A. P.; Min, M.; Pantin, E.; Waters, L.B.F.M.; Tielens, A. G. G. M.; Honda, M.; Fujiwara, H.; Bouwman, J.; Van Boekel, R.; Dougherty, S.M.; de Koter, A.; Dominik, C.; Mulders, G. D.

    2011-01-01

    Context. The recent findings of gas giant planets around young A-type stars suggest that disks surrounding Herbig Ae/Be stars will develop planetary systems. An interesting case is HD142527, for which previous observations revealed a complex circumstellar environment and an unusually high ratio of i

  5. The complex circumstellar environment of HD142527

    NARCIS (Netherlands)

    Verhoeff, A. P.; Min, M.; Pantin, E.; Waters, L. B. F. M.; Tielens, A. G. G. M.; Honda, M.; Fujiwara, H.; Bouwman, J.; van Boekel, R.; Dougherty, S. M.; de Koter, A.; Dominik, C.; Mulders, G. D.

    2011-01-01

    Context. The recent findings of gas giant planets around young A-type stars suggest that disks surrounding Herbig Ae/Be stars will develop planetary systems. An interesting case is HD142527, for which previous observations revealed a complex circumstellar environment and an unusually high ratio of i

  6. Imaging polarimetry of circumstellar environments with the Extreme Polarimeter

    NARCIS (Netherlands)

    Rodenhuis, M.|info:eu-repo/dai/nl/325801843; Canovas, H.; Jeffers, S.V.|info:eu-repo/dai/nl/326052658; Min, M.|info:eu-repo/dai/nl/277318416; Keller, C.U.|info:eu-repo/dai/nl/304824550

    2010-01-01

    Three successful observation campaigns have been conducted with the Extreme Polarimeter, an imaging polarimeter for the study of circumstellar environments in scattered light at visible wavelengths. A contrast ratio between the central star and the circumstellar source of 10-5 can be achieved with p

  7. The EXoplanetary Circumstellar Environments and Disk Explorer (EXCEDE)

    CERN Document Server

    Guyon, Olivier; Belikov, Ruslan; Tenerelli, Domenick J

    2012-01-01

    We present an overview of the EXoplanetary Circumstellar Environments and Disk Explorer (EXCEDE), selected by NASA for technology development and maturation. EXCEDE will study the formation, evolution and architectures of exoplanetary systems, and characterize circumstellar environments into stellar habitable zones. EXCEDE provides contrast-limited scattered-light detection sensitivities ~ 1000x greater than HST or JWST coronagraphs at a much smaller effective inner working angle (IWA), thus enabling the exploration and characterization of exoplanetary circumstellar disks in currently inaccessible domains. EXCEDE will utilize a laboratory demonstrated high-performance Phase Induced Amplitude Apodized Coronagraph (PIAA-C) integrated with a 70 cm diameter unobscured aperture visible light telescope. The EXCEDE PIAA-C will deliver star-to-disk augmented image contrasts of < 10E-8 and a 1.2 L/D IWA or 140 mas with a wavefront control system utilizing a 2000-element MEMS DM and fast steering mirror. EXCEDE will...

  8. The Circumstellar Environments of Exoplanet Host Stars

    Science.gov (United States)

    Chen, Christine

    The WFIRST-AFTA mission currently includes the provision for a high contrast imaging instrument with a primary goal of discovering new, low mass exoplanets and characterizing their atmospheres. To date, eight exoplanetary systems have been discovered via direct imaging using the current generation of ground-based high-contrast facilities. Five of those systems, including the iconic beta Pictoris and HR 8799 systems, possess infrared excesses, indicative of the presence of circumstellar dust. Detailed studies of dust and gas morphology in the beta Pictoris disk provided the impetus for searching for, and eventually imaging the planet. These studies further suggest that additional planets orbit the star, but are below current detection thresholds. Such systems will be prime targets for WFIRST-AFTA, which will obtain visual spectroscopy of several spectral features from molecules in the exoplanet atmospheres including CH4, H2O, and CO2. We propose to: (1) model the dust in exoplanetary systems with well characterized planets and infrared excesses to better constrain the dust geometry and particle properties; (2) generate synthetic WFIRST-AFTA images of these disks with embedded known and putative planets using point-spread-functions generated by JPL, and run our simulations though a WFIRST-AFTA pipeline; and (3) evaluate the sensitivity of WFIRST-AFTA to known and putative planets that have a range of masses and distances from their host stars. The proposed simulations will also assist the community in understanding how WFIRST-AFTA will contribute to our knowledge of debris disks and the role that minor bodies play in the delivery of water into the terrestrial planet zone. The proposed project is complementary to the efforts currently being carried out by the Science Definition Team (SDT), which focus on simulating planets embedded in tenuous disks, analogous to the Zodiacal dust system in our Solar System, the Earth s resonant dust ring, and the HR 4796 dust ring

  9. Mean gas opacity for circumstellar environments and equilibrium temperature degeneracy

    CERN Document Server

    Malygin, M G; Klahr, H; Dullemond, C P; Henning, Th

    2014-01-01

    In a molecular cloud dust opacity typically dominates over gas opacity, yet in the vicinities of forming stars dust is depleted, and gas is the sole provider of opacity. In the optically thin circumstellar environments the radiation temperature cannot be assumed to be equal to the gas temperature, hence the two-temperature Planck means are necessary to calculate the radiative equilibrium. By using the two-temperature mean opacity one does obtain the proper equilibrium gas temperature in a circumstellar environment, which is in a chemical equilibrium. A careful consideration of a radiative transfer problem reveals that the equilibrium temperature solution can be degenerate in an optically thin gaseous environment. We compute mean gas opacities based on the publicly available code DFSYNTHE by Kurucz and Castelli. We performed the calculations assuming local thermodynamic equilibrium and an ideal gas equation of state. The values were derived by direct integration of the high-resolution opacity spectrum. We prod...

  10. The Three-Dimensional Circumstellar Environment of SN 1987A

    CERN Document Server

    Sugerman, B E K; Kunkel, W E; Heathcote, S R; Lawrence, S S; Sugerman, Ben E. K.; Crotts, Arlin P. S.; Kunkel, William E.; Heathcote, Stephen R.; Lawrence, Stephen S.

    2005-01-01

    We present the detailed construction and analysis of the most complete map to date of the circumstellar environment around SN 1987A, using ground and space-based imaging from the past 16 years. PSF-matched difference-imaging analyses of data from 1988 through 1997 reveal material between 1 and 28 ly from the SN. Careful analyses allows the reconstruction of the probable circumstellar environment, revealing a richly-structured bipolar nebula. An outer, double-lobed ``Peanut,'' which is believed to be the contact discontinuity between red supergiant and main sequence winds, is a prolate shell extending 28 ly along the poles and 11 ly near the equator. Napoleon's Hat, previously believed to be an independent structure, is the waist of this Peanut, which is pinched to a radius of 6 ly. Interior to this is a cylindrical hourglass, 1 ly in radius and 4 ly long, which connects to the Peanut by a thick equatorial disk. The nebulae are inclined 41\\degr south and 8\\degr east of the line of sight, slightly elliptical in...

  11. B[e] Supergiants' circumstellar environment: disks or rings?

    CERN Document Server

    Maravelias, G; Aret, A; Cidale, L; Arias, M L; Fernandes, M Borges

    2016-01-01

    B[e] Supergiants are a phase in the evolution of some massive stars for which we have observational evidence but no predictions by any stellar evolution model. The mass-loss during this phase creates a complex circumstellar environment with atomic, molecular, and dust regions usually found in rings or disk-like structures. However, the detailed structure and the formation of the circumstellar environment are not well-understood, requiring further investigation. To address that we initiated an observing campaign to obtain a homogeneous set of high-resolution spectra in both the optical and NIR (using MPG-ESO/FEROS, GEMINI/Phoenix and VLT/CRIRES, respectively). We monitor a number of Galactic B[e] Supergiants, for which we examined the [OI] and [CaII] emission lines and the bandheads of the CO and SiO molecules to probe the structure and the kinematics of their formation regions. We find that the emission from each tracer forms either in a single or in multiple equatorial rings.

  12. B[e] Supergiants' Circumstellar Environment: Disks or Rings?

    Science.gov (United States)

    Maravelias, G.; Kraus, M.; Aret, A.; Cidale, L.; Arias, M. L.; Borges Fernandes, M.

    2017-02-01

    B[e] supergiants are a phase in the evolution of some massive stars for which we have observational evidence but no predictions by any stellar evolution model. The mass-loss during this phase creates a complex circumstellar environment with atomic, molecular, and dust regions usually found in rings or disk-like structures. However, the detailed structure and the formation of the circumstellar environment are not well-understood, requiring further investigation. To address that we initiated an observing campaign to obtain a homogeneous set of high-resolution spectra in both the optical and NIR (using MPG-ESO/FEROS, GEMINI /Phoenix and VLT/CRIRES, respectively). We monitor a number of Galactic B[e] supergiants, for which we examined the [O I] and [Ca II] emission lines and the bandheads of the CO and SiO molecules to probe the structure and the kinematics of their formation regions. We find that the emission from each tracer forms either in a single or multiple equatorial rings.

  13. The Three-dimensional Circumstellar Environment of SN 1987A

    Science.gov (United States)

    Sugerman, Ben E. K.; Crotts, Arlin P. S.; Kunkel, William E.; Heathcote, Stephen R.; Lawrence, Stephen S.

    2005-07-01

    Surrounding SN 1987A is a three-ring nebula attributed to interacting stellar winds, yet no model has successfully reproduced this system. Fortunately, the progenitor's mass-loss history can be reconstructed using light echoes, in which scattered light from the supernova traces the three-dimensional morphology of its circumstellar dust. In this paper, we construct and analyze the most complete map to date of the progenitor's circumstellar environment, using ground- and space-based imaging from the past 16 years. PSF-matched difference-imaging analyses of data from 1988 through 1997 reveal material between 1 and 28 lt-yr from the SN. Previously known structures, such as an inner hourglass, Napoleon's Hat, and a contact discontinuity, are probed in greater spatial detail than before. Previously unknown features are also discovered, such as a southern counterpart to Napoleon's Hat. Careful analyses of these echoes allows the reconstruction of the probable circumstellar environment, revealing a richly structured bipolar nebula. An outer, double-lobed ``Peanut,'' which is believed to be the contact discontinuity between red supergiant and main-sequence winds, is a prolate shell extending 28 lt-yr along the poles and 11 lt-yr near the equator. Napoleon's Hat, previously believed to be an independent structure, is the waist of this Peanut, which is pinched to a radius of 6 lt-yr. Interior to this is a cylindrical hourglass, 1 lt-yr in radius and 4 lt-yr long, which connects to the Peanut by a thick equatorial disk. The nebulae are inclined 41° south and 8° east of the line of sight, slightly elliptical in cross section, and marginally offset west of the SN. From the hourglass to the large, bipolar lobes, echo fluxes suggest that the gas density drops from 1-3 to >~0.03 cm-3, while the maximum dust-grain size increases from ~0.2 to 2 μm, and the silicate:carbonaceous dust ratio decreases. The nebulae have a total mass of ~1.7 Msolar. The geometry of the three rings is

  14. The circumstellar environment of pre-SN Ia systems

    CERN Document Server

    Harvey, E; Boumis, P; Kopsacheili, M; Akras, S; Sabin, L; Jurkic, T

    2016-01-01

    Here we explore the possible preexisting circumstellar debris of supernova type Ia systems. Classical, symbiotic and recurrent novae all accrete onto roughly solar mass white dwarfs from main sequence or Mira type companions and result in thermonuclear runaways and expulsion of the accreted material at high velocity. The expelled material forms a fast moving shell that eventually slows to planetary nebula expansion velocities within several hundred years. All such systems are recurrent and thousands of shells (each of about 0.001 Mo) snow plough into the environment. As these systems involve common envelope binaries the material is distributed in a non-spherical shell. These systems could be progenitors of some SN Ia and thus explode into environments with large amounts of accumulated gas and dust distributed in thin non-spherical shells. Such shells should be observable around 100 years after a SN Ia event in a radio flash as the SN Ia debris meets that of the ejected material of the systems previous incarna...

  15. The formation of polycyclic aromatic hydrocarbons in evolved circumstellar environments

    CERN Document Server

    Cherchneff, Isabelle

    2010-01-01

    The formation of Polycyclic Aromatic Hydrocarbons in the circumstellar outflows of evolved stars is reviewed, with an emphasis on carbon stars on the Asymptotic Giant Branch. Evidence for PAHs present in their winds is provided by meteoritic studies and recent observations of the Unidentified Infrared bands. We detail the chemical processes leading to the closure of the first aromatic ring as well as the growth mechanisms leading to amorphous carbon grains. Existing studies on PAH formation in evolved stellar envelopes are reviewed and new results for the modelling of the inner wind of the archetype carbon star IRC+10216 are presented. Benzene, C6H6, forms close to the star, as well as water, H2O, as a result of non-equilibrium chemistry induced by the periodic passage of shocks. The growth process of aromatic rings may thus resemble that active in sooting flames due to the presence of radicals like hydroxyl, OH. Finally, we discuss possible formation processes for PAHs and aromatic compounds in the hydrogen-...

  16. A New View of the Circumstellar Environment of SN 1987A

    Science.gov (United States)

    Sugerman, Ben E. K.; Crotts, Arlin P. S.; Kunkel, William E.; Heathcote, Stephen R.; Lawrence, Stephen S.

    2005-07-01

    We summarize the analysis of a uniform set of both previously known and newly discovered scattered-light echoes, detected within 30" of SN 1987A in 10 years of optical imaging, and with which we have constructed the most complete three-dimensional model of the progenitor's circumstellar environment. Surrounding the SN is a richly structured bipolar nebula. An outer, double-lobed ``peanut,'' which we believe is the contact discontinuity between the red supergiant and main-sequence winds, is a prolate shell extending 28 lt-yr along the poles and 11 lt-yr near the equator. Napoleon's Hat, previously believed to be an independent structure, is the waist of this peanut, which is pinched to a radius of 6 lt-yr. Interior, the innermost circumstellar material lies along a cylindrical hourglass, 1 lt-yr in radius and 4 lt-yr long, which connects to the peanut by a thick equatorial disk. The nebulae are inclined 41° south and 8° east of the line of sight, slightly elliptical in cross section, and marginally offset west of the SN. The three-dimensional geometry of the three circumstellar rings is studied, suggesting the northern and southern rings are located 1.3 and 1.0 lt-yr from the SN, while the equatorial ring is elliptical (b/a~0.03 cm-3 the maximum dust-grain size increases from ~0.2 to 2 μm and the silicate:carbonaceous dust ratio decreases. The nebulae have a total mass of ~1.7 Msolar, yielding a red-supergiant mass loss around 5×10-6 Msolar yr-1. We compare these results to current formation models and find that no model has successfully reproduced this system. However, our results suggest a heuristic evolutionary sequence in which the progenitor evolves through two ``blue loops,'' perhaps accompanied by a close binary companion.

  17. The Circumstellar Environments of NML Cyg and the Cool Hypergiants

    CERN Document Server

    Schuster, M T; Marengo, M; Schuster, Michael T.; Humphreys, Roberta M.; Marengo, Massimo

    2005-01-01

    We present high-resolution HST WFPC2 images of compact nebulosity surrounding the cool M-type hypergiants NML Cyg, VX Sgr and S Per. The powerful OH/IR source NML Cyg exhibits a peculiar bean-shaped asymmetric nebula that is coincident with the distribution of its H2O vapor masers. We show that NML Cyg's circumstellar envelope is likely shaped by photo-dissociation from the powerful, nearby association Cyg OB2 inside the Cygnus X superbubble. The OH/IR sources VX Sgr and S Per have marginally resolved envelopes. S Per's circumstellar nebula appears elongated in a NE/SW orientation similar to that for its OH and H2O masers, while VX Sgr is embedded in a spheroidal envelope. We find no evidence for circumstellar nebulosity around the intermediate-type hypergiants rho Cas, HR 8752, HR 5171a, nor the normal M-type supergiant mu Cep. We conclude that there is no evidence for high mass loss events prior to 500-1000 yrs ago for these four stars.

  18. Circumstellar Environments of MYSOs Revealed by IFU Spectroscopy

    Science.gov (United States)

    Navarete, F.; Damineli, A.; Barbosa, C. L.; Blum, R. D.

    2015-01-01

    Formation of massive stars (M > 8 M ⊙) is still not well understood and lacks of observational constraints. We observed 7 MYSO candidates using the NIFS spectrometer at Gemini North Telescope to study the accretion process at high angular resolution (~ 50 mas) and very closer to the central star. Preliminary results for 2 sources have revealed circumstellar structures traced by Brackett-Gamma, CO lines and extended H2 emission. Both sources present kinematics in the CO absorption lines, suggesting rotating structures. The next step will derive the central mass of each source by applying a keplerian model for these CO features.

  19. The Complex Circumstellar and Circumbinary Environment of V356 Sgr

    Science.gov (United States)

    Fullard, Andrew; Lomax, Jamie R.; Malatesta, Michael A.; Babler, Brian L.; Bednarski, Daniel; Berdis, Jodi; Bjorkman, Karen S.; Bjorkman, Jon Eric; Carciofi, Alex C.; Davidson, James W.; Keil, Marcus; Meade, Marilyn; Nordsieck, Kenneth H.; Scheffler, Matt; Hoffman, Jennifer L.; Wisniewski, John P.

    2017-01-01

    The eclipsing, interacting binary star V356 Sgr is a particularly exciting object for analysis due to its probable nonconservative mass loss and the possible progenitor link between Roche-lobe overflow systems and core-collapse supernovae. We present the results of 45 spectropolarimetric observations of V356 Sgr taken over 21 years, which we used to characterize the geometry of the system's circumstellar material. We find that V356 Sgr exhibits a large intrinsic polarization signature arising from electron scattering. The lack of repeatable eclipses in the polarization phase curves indicates the presence of a substantial pool of scatterers not occulted by either star. We suggest that these scatterers form either a circumbinary disk coplanar with the gainer's accretion disk, or an elongated structure perpendicular to the orbital plane of V356 Sgr, possibly formed by bipolar outflows.We also observe small-scale, cycle-to-cycle variations in the magnitude of intrinsic polarization at individual phases. These may indicate a mass transfer or mass loss rate that varies on the time-scale of the system's orbital period. Finally, we present a comparison of V356 Sgr with the well studied beta Lyr system; the significant differences observed between the two systems suggests diversity in the basic circumstellar geometry of Roche-lobe overflow binaries.

  20. The Complex Circumstellar and Circumbinary Environment of V356 Sgr

    CERN Document Server

    Lomax, Jamie R; Malatesta, Michael A; Babler, Brian; Bednarski, Daniel; Berdis, Jodi R; Bjorkman, Karen S; Bjorkman, Jon E; Carciofi, Alex C; Davidson, James W; Keil, Marcus; Meade, Marilyn R; Nordsieck, Kenneth; Scheffler, Matt; Hoffman, Jennifer L; Wisniewski, John P

    2016-01-01

    We analyze 45 spectropolarimetric observations of the eclipsing, interacting binary star V356 Sgr, obtained over a period of 21 years, to characterize the geometry of the system's circumstellar material. After removing interstellar polarization from these data, we find the system exhibits a large intrinsic polarization signature arising from electron scattering. In addition, the lack of repeatable eclipses in the polarization phase curves indicates the presence of a substantial pool of scatterers not occulted by either star. We suggest that these scatterers form either a circumbinary disk coplanar with the gainer's accretion disk or an elongated structure perpendicular to the orbital plane of V356 Sgr, possibly formed by bipolar outflows. We also observe small-scale, cycle-to-cycle variations in the magnitude of intrinsic polarization at individual phases, which we interpret as evidence of variability in the amount of scattering material present within and around the system. This may indicate a mass transfer ...

  1. Exploring the multifaceted circumstellar environment of the luminous blue variable HR Carinae

    Science.gov (United States)

    Buemi, C. S.; Trigilio, C.; Leto, P.; Umana, G.; Ingallinera, A.; Cavallaro, F.; Cerrigone, L.; Agliozzo, C.; Bufano, F.; Riggi, S.; Molinari, S.; Schillirò, F.

    2017-03-01

    We present a multiwavelength study of the Galactic luminous blue variable HR Carinae, based on new high-resolution mid-infrared (IR) and radio images obtained with the Very Large Telescope (VLT) and the Australia Telescope Compact Array (ATCA), which have been complemented by far-infrared Herschel-Photodetector Array Camera and Spectrometer (PACS) observations and ATCA archive data. The Herschel images reveal the large-scale distribution of the dusty emitting nebula, which extends mainly to the north-east direction, up to 70 arcsec from the central star, and is oriented along the direction of the space motion of the star. In the mid-infrared images, the brightness distribution is characterized by two arc-shaped structures, tracing an inner envelope surrounding the central star more closely. At radio wavelengths, the ionized gas emission lies on the opposite side of the cold dust with respect to the position of the star, as if the ionized front were confined by the surrounding medium in the north-south direction. Comparison with previous data indicates significant changes in the radio nebula morphology and in the mass-loss rate from the central star, which has increased from 6.1 × 10-6 M⊙ yr-1 in 1994-1995 to 1.17 × 10-5 M⊙ yr-1 in 2014. We investigate possible scenarios that could have generated the complex circumstellar environment revealed by our multiwavelength data.

  2. Imaging the circumstellar environment of the young T Tauri star SU Aurigae

    CERN Document Server

    Jeffers, S V; Canovas, H; Rodenhuis, M; Keller, C U

    2013-01-01

    The circumstellar environments of classical T Tauri stars are challenging to directly image because of their high star-to-disk contrast ratio. One method to overcome this is by using imaging polarimetry where scattered and consequently polarised starlight from the star's circumstellar disk can be separated from the unpolarised light of the central star. We present images of the circumstellar environment of SU Aur, a classical T Tauri star at the transition of T Tauri to Herbig stars. The images directly show that the disk extends out to ~500 au with an inclination angle of $\\sim$ 50$^\\circ$. Using interpretive models, we derived very small grains in the surface layers of its disk, with a very steep size- and surface-density distribution. Additionally, we resolved a large and extended nebulosity in our images that is most likely a remnant of the prenatal molecular cloud. The position angle of the disk, determined directly from our images, rules out a polar outflow or jet as the cause of this large-scale nebulo...

  3. Archival Legacy Investigations of Circumstellar Environments (ALICE): Statistical assessment of point source detections

    CERN Document Server

    Choquet, É; Soummer, R; Perrin, M D; Hagan, J B; Gofas-Salas, E; Rajan, A; Aguilar, J

    2015-01-01

    The ALICE program, for Archival Legacy Investigation of Circumstellar Environment, is currently conducting a virtual survey of about 400 stars, by re-analyzing the HST-NICMOS coronagraphic archive with advanced post-processing techniques. We present here the strategy that we adopted to identify detections and potential candidates for follow-up observations, and we give a preliminary overview of our detections. We present a statistical analysis conducted to evaluate the confidence level on these detection and the completeness of our candidate search.

  4. HI and CO in the circumstellar environment of the oxygen-rich AGB star RX Lep

    CERN Document Server

    Libert, Y; Gérard, E; Winters, J M

    2008-01-01

    Circumstellar shells around AGB stars are built over long periods of time that may reach several million years. They may therefore be extended over large sizes (~1 pc, possibly more), and different complementary tracers are needed to describe their global properties. In the present work, we combined 21-cm HI and CO rotational line data obtained on an oxygen-rich semi-regular variable, RX Lep, to describe the global properties of its circumstellar environment. With the SEST, we detected the CO(2-1) rotational line from RX Lep. The line profile is parabolic and implies an expansion velocity of ~4.2 km/s and a mass-loss rate ~1.7 10^-7 Msun/yr (d = 137 pc). The HI line at 21 cm was detected with the Nancay Radiotelescope on the star position and at several offset positions. The linear shell size is relatively small, ~0.1 pc, but we detect a trail extending southward to ~0.5 pc. The line profiles are approximately Gaussian with an FWHM ~3.8 km/s and interpreted with a model developed for the detached shell around...

  5. A New View of the Circumstellar Environment of SN 1987A

    CERN Document Server

    Sugerman, B E K; Kunkel, W E; Heathcote, S R; Lawrence, S S; Sugerman, Ben E. K.; Crotts, Arlin P. S.; Kunkel, William E.; Heathcote, Stephen R.; Lawrence, Stephen S.

    2005-01-01

    We summarize the analysis of a uniform set of both previously-known and newly-discovered scattered-light echoes, detected within 30" of SN 1987A in ten years of optical imaging, and with which we have constructed the most complete three-dimensional model of the progenitor's circumstellar environment. Surrounding the SN is a richly-structured bipolar nebula. An outer, double-lobed ``peanut,'' which we believe is the contact discontinuity between the red supergiant and main sequence winds, is a prolate shell extending 28 ly along the poles and 11 ly near the equator. Napoleon's Hat, previously believed to be an independent structure, is the waist of this peanut, which is pinched to a radius of 6 ly. Interior, the innermost circumstellar material lies along a cylindrical hourglass, 1 ly in radius and 4 ly long, which connects to the peanut by a thick equatorial disk. The nebulae are inclined 41o south and 8o east of the line of sight, slightly elliptical in cross section, and marginally offset west of the SN. Th...

  6. ALMA view of the circumstellar environment of the post-common-envelope-evolution binary system HD101584

    CERN Document Server

    Olofsson, H; Maercker, M; Humphreys, E M L; Lindqvist, M; Nyman, L; Ramstedt, S

    2015-01-01

    We study the circumstellar evolution of the binary HD101584, consisting of a post-AGB star and a low-mass companion, which is most likely a post-common-envelope-evolution system. We used ALMA observations of the 12CO, 13CO, and C18O J=2-1 lines and the 1.3mm continuum to determine the morphology, kinematics, masses, and energetics of the circumstellar environment. The circumstellar medium has a bipolar hour-glass structure, seen almost pole-on, formed by an energetic jet, about 150 km/s. We conjecture that the circumstellar morphology is related to an event that took place about 500 year ago, possibly a capture event where the companion spiraled in towards the AGB star. However, the kinetic energy of the accelerated gas exceeds the released orbital energy, and, taking into account the expected energy transfer efficiency of the process, the observed phenomenon does not match current common-envelope scenarios. This suggests that another process must augment, or even dominate, the ejection process. A significant...

  7. ALMA Observations of Anisotropic Dust Mass-loss in the Inner Circumstellar Environment of the Red Supergiant VY CMa

    CERN Document Server

    O'Gorman, E; Richards, A M S; Baudry, A; De Beck, E; Decin, L; Harper, G M; Humphreys, E M; Kervella, P; Khouri, T; Muller, S

    2014-01-01

    The processes leading to dust formation and the subsequent role it plays in driving mass-loss in cool evolved stars is an area of intense study. Here, we present high resolution ALMA Science Verification data of the continuum emission around the highly evolved oxygen-rich red supergiant VY CMa. These data enable us to study the dust in its inner circumstellar environment at a spatial resolution of 129 mas at 321 GHz and 59 mas at 658 GHz, allowing us to trace dust on spatial scales down to 11 R$_{\\star}$ (71 AU). Two prominent dust components are detected and resolved. The brightest dust component, C, is located 334 mas (61 R$_{\\star}$) south-east of the star and has a dust mass of at least $2.5\\times 10^{-4} $M$_{\\odot}$. It has an emissivity spectral index of $\\beta =-0.1$ at its peak, implying that it is either optically thick at these frequencies with a cool core of $T_{d}\\lesssim 100$ K, and/or contains very large dust grains. Interestingly, not a single molecule in the ALMA data has emission close to th...

  8. Similarities in the structure of the circumstellar environments of B[e] supergiants and yellow hypergiants

    CERN Document Server

    Aret, Anna; Kraus, Michaela; Maravelias, Grigoris

    2016-01-01

    Yellow Hypergiants (YHGs) and B[e] supergiants (B[e]SGs), though in different phases in their evolution, display many features in common. This is partly due to the fact that both types of objects undergo strong, often asymmetric mass loss, and the ejected material accumulates in shells, rings, or disk-like structures, giving rise to emission from warm molecules and dust. We performed an optical spectroscopic survey of northern Galactic emission-line stars aimed at identifying tracers for the structure and kinematics of circumstellar environments. We identified two sets of lines, [O I] and [Ca II], which originate from the discs of B[e]SGs. The same set of lines is observed in V1302 Aql and V509 Cas, which are both hot YHGs. While V1302 Aql is known to have a disc-like structure, the kinematical broadening of the lines in V509 Cas suggest a Keplerian disk or ring around this star alike their hotter B[e]SG counterparts.

  9. Exploring the circumstellar environment of the young eruptive star V2492 Cyg

    CERN Document Server

    Kóspál, Á; Acosta-Pulido, J A; Morales, M J Arévalo; Balog, Z; Carnerero, M I; Szegedi-Elek, E; Farkas, A; Henning, Th; Kelemen, J; Kovács, T; Kun, M; Marton, G; Mészáros, Sz; Moór, A; Pál, A; Sárneczky, K; Szakáts, R; Szalai, N; Szing, A; Tóth, I; Turner, N J; Vida, K

    2013-01-01

    Context. V2492 Cyg is a young eruptive star that went into outburst in 2010. The near-infrared color changes observed since the outburst peak suggest that the source belongs to a newly defined sub-class of young eruptive stars where time-dependent accretion and variable line-of-sight extinction play a combined role in the flux changes. Aims. In order to learn about the origin of the light variations and to explore the circumstellar and interstellar environment of V2492 Cyg, we monitored the source at ten different wavelengths, between 0.55 \\mu m and 2.2 \\mu m from the ground, and between 3.6 \\mu m and 160 \\mu m from space. Methods. We analyze the light curves and study the color-color diagrams via comparison with the standard reddening path. We examine the structure of the molecular cloud hosting V2492 Cyg by computing temperature and optical depth maps from the far-infrared data. Results. We find that the shapes of the light curves at different wavelengths are strictly self-similar, and the observed variabil...

  10. Immediate dense circumstellar environment of supernova progenitors caused by wind acceleration: its effect on supernova light curves

    Science.gov (United States)

    Moriya, Takashi J.; Yoon, Sung-Chul; Gräfener, Götz; Blinnikov, Sergei I.

    2017-07-01

    Type IIP supernova progenitors are often surrounded by dense circumstellar media that may result from mass-loss enhancement of the progenitors shortly before their explosions. Previous light-curve studies suggest that the mass-loss rates are enhanced up to ∼0.1 M⊙ yr-1, assuming a constant wind velocity. However, the density of circumstellar media at the immediate stellar vicinity can be much higher than previously inferred for a given mass-loss rate if wind acceleration is taken into account. We show that the wind acceleration has a huge impact when we estimate mass-loss rates from early light curves of Type IIP supernovae by taking SN 2013fs as an example. We perform numerical calculations of the interaction between supernova ejecta and circumstellar media with a constant mass-loss rate but with a β-law wind velocity profile. We find that the mass-loss rate of the progenitor of SN 2013fs shortly before the explosion, which was inferred to be ∼0.1 M⊙ yr-1 with a constant wind velocity of 10 km s-1 by a previous light-curve modelling, can be as low as ∼10-3 M⊙ yr-1 with the same terminal wind velocity of 10 km s-1 but with a wind velocity profile with β ≃ 5. In both cases, the mass of the circumstellar medium is similar (≃0.5 M⊙). Therefore, the beginning of the progenitor's mass-loss enhancement in our interpretation is ∼100 yr before the explosion, not several years. Our result indicates that the immediate dense environment of Type II supernova progenitors may be significantly influenced by wind acceleration.

  11. The circumstellar environment of IRAS 16293-2422. ISO-LWS and SCUBA observations

    Science.gov (United States)

    Correia, J. C.; Griffin, M.; Saraceno, P.

    2004-05-01

    We present far-infrared (FIR) continuum observations of the deeply embedded source IRAS 16293-2422 performed with the Long Wavelength Spectrometer (LWS) on-board the Infrared Space Observatory (ISO). We also report 450 and 850 μm mapping observations done with the Submillimetre Common-User Bolometer Array (SCUBA) at the James Clerk Maxwell Telescope (JCMT). We combined these observations with IRAS and other JCMT data available in the literature to construct a complete spectral energy distribution (SED) of the source. A spherically symmetric dusty envelope model was used to reproduce the SED and to characterize the circumstellar matter around the object. We call attention to the fact that when using models such as the one presented here, one needs spatial information about the object to distinguish between different possible fits to the SED. A comparison between the intensity profiles at 450 and 850 μm obtained from the SCUBA observations and the profiles predicted by the model allowed us to constrain the size of the envelope and its density distribution. The SED and the 850 μm intensity profile of the source are consistent with a centrally peaked power law dust density distribution of the form ρ(r) ∝ r-p with p = 1.5-2, with a radius Renv = 3000-3250 AU, defining a very compact circumstellar envelope. We estimate a bolometric luminosity Lbol = 36 L⊙, an envelope mass Menv = 3.4 M⊙, and a submillimetre to bolometric luminosity ratio Lsubmm/Lbol = 1.9%, confirming that the source shows a submillimetre excess characteristic of Class 0 sources.

  12. Physiological Disorders in Closed, Controlled Environment Crops

    Science.gov (United States)

    Wheeler, Raymond M.; Morrow, Robert C.

    2010-01-01

    This slide presentation reviews some of the physiological disorders that affect crops grown in closed controlled environments. A physiological disorder is understood to be a problem resulting from the influence of environmental and horticultural factors on plan development other than a problem caused by a pathogen or some other abiotic cause. The topics that are addressed are: (1) Calcium-Related Disorders (2) Oedema (Intumescence) (3) Long-Photoperiod Injury (4) Light Spectral Quality Effects (5) Super-Elevated CO2 Injuries (6) Ethylene (7) Other Disorders (8) Considerations for Closed Space Environments. Views of plant with the disorders are shown.

  13. The polluted atmosphere of the white dwarf NLTT 25792 and the diversity of circumstellar environments

    CERN Document Server

    Vennes, S

    2013-01-01

    We present an analysis of X-Shooter spectra of the polluted, hydrogen-rich white dwarf NLTT 25792. The spectra show strong lines of calcium (Ca H&K, near-infrared calcium triplet, and Ca I 4226 and numerous lines of iron along with magnesium and aluminum lines from which we draw the abundance pattern. Moreover, the photospheric Ca H&K lines are possibly blended with a circumstellar component shifted by -20 km/s relative to the photosphere. A comparison with a sample of four white dwarfs with similar parameters show considerable variations in their abundance patterns, particularly in the calcium to magnesium abundance ratio that varies by a factor of five within this sample. The observed variations, even after accounting for diffusion effects, imply similar variations in the putative accretion source. Also, we find that silicon and sodium are significantly underabundant in the atmosphere of NLTT 25792, a fact that may offer some clues on the nature of the accretion source.

  14. Circumstellar Environments of Luminous Infrared Stellar Objects in the Magellanic Clouds

    Science.gov (United States)

    Azari, Abigail; Sahai, Raghvendra

    2011-01-01

    Young stars are formed out of the interstellar medium (ISM) which is replenished by mass loss rates from evolved stars. Circumstellar matter around young and evolved stellar objects usually emits energy in the infrared (IR) wavelength range as the matter is heated by the central star. Surveys of the Magellanic Clouds with the Spitzer Space Telescope in the 3.6-160 micron range have previously been completed. These surveys have led to catalogs of infrared sources: which include HII regions, young stars, super giants, asymptotic giant branch (AGB) stars, post-asymptotic giant branch (post-AGB) stars, and planetary nebulae. The utility of such surveys can be improved upon by using Hubble Space Telescope (HST) data. HST provides higher angular resolution than Spitzer and has allowed for more detailed investigation of these luminous IR objects. This project used previously obtained HST archival data to examine luminous IR objects at optical wavelengths. This allows for the reclassification of stellar objects previously thought as one type of object or in a particular stage of their stellar evolution. An overall objective of this project included looking for extended nebulosity around evolved stars to better understand the life cycle of such objects and classify these nebulae by shape.

  15. The close environment of Supermassive Black Holes

    Science.gov (United States)

    Matt, Giorgio

    2016-07-01

    There are two main scientific goals of the "Close environment of SMBH" Athena Topical Panel: the determination of the BH spin distribution in the local Universe, and of the geometry of the hot X-ray emitting corona via time lag measurements. The rationale behind these goals, and how they will be achieved with Athena, will be discussed in this talk.

  16. X-ray Emission from Supernovae in Dense Circumstellar Matter Environments: a Search for Collisionless Shocks

    Science.gov (United States)

    Ofek, E. O.; Fox, D.; Cenko, Stephen B.; Sullivan, M; Gnat, O.; Frail, D. A.; Horesh, A.; Corsi, A.; Quimby, R. M.; Gehrels, N.; Kulkarni, S. R.; Gal-Yam, A.; Nugent, P. E.; Yaron, O.; Fillippenko, A. V; Kasliwal, M. M.; Bildsten, L.; Bloom, J. S.; Poznanski, D.; Arcavi, I.; Laher, R. R.; Levitan, D.; Sesar, B.; Surace, J..

    2013-01-01

    The optical light curve of some supernovae (SNe) may be powered by the outward diffusion of the energy deposited by the explosion shock (the so-called shock breakout) in optically thick (Tau approx > 30) circumstellar matter (CSM). Recently, it was shown that the radiation-mediated and radiation-dominated shock in an optically thick wind must transform into a collisionless shock and can produce hard X-rays. The X-rays are expected to peak at late times, relative to maximum visible light. Here we report on a search, using Swift/XRT and Chandra, for X-ray emission from 28 SNe that belong to classes whose progenitors are suspected to be embedded in dense CSM. Our sample includes 19 Type IIn SNe, one Type Ibn SN, and eight hydrogen-poor superluminous SNe (SLSN-I such as SN 2005ap). Two SNe (SN 2006jc and SN 2010jl) have X-ray properties that are roughly consistent with the expectation for X-rays from a collisionless shock in optically thick CSM. However, the X-ray emission from SN 2006jc can also be explained as originating in an optically thin region. Thus, we propose that the optical light curve of SN 2010jl is powered by shock breakout in CSM. We suggest that two other events (SN 2010al and SN 2011ht) were too X-ray bright during the SN maximum optical light to be explained by the shock-breakout model.We conclude that the light curves of some, but not all, SNe IIn/Ibn are powered by shock breakout in CSM. For the rest of the SNe in our sample, including all of the SLSN-I events, our X-ray limits are not deep enough and were typically obtained too early (i.e., near the SN maximum light) for definitive conclusions about their nature. Late-time X-ray observations are required in order to further test whether these SNe are indeed embedded in dense CSM. We review the conditions required for a shock breakout in a wind profile. We argue that the timescale, relative to maximum light, for the SN to peak in X-rays is a probe of the column density and the density profile above

  17. The close circumstellar environment of Betelgeuse. IV. VLTI/PIONIER interferometric monitoring of the photosphere

    CERN Document Server

    Montargès, M; Perrin, G; Chiavassa, A; Bouquin, J B Le; Aurière, M; López-Ariste, A; Mathias, P; Ridgway, S T; Lacour, S; Haubois, X; Berger, J P

    2016-01-01

    Context. The mass-loss mechanism of cool massive evolved stars is poorly understood. The proximity of Betelgeuse makes it an appealing target to study its atmosphere, map the shape of its envelope, and follow the structure of its wind from the photosphere out to the interstellar medium. Aims. A link is suspected between the powerful convective motions in Betelgeuse and its mass loss. We aim to constrain the spatial structure and temporal evolution of the convective pattern on the photosphere and to search for evidence of this link. Methods. We report new interferometric observations in the infrared H band using the VLTI/PIONIER instrument. We monitored the photosphere of Betelgeuse between 2012 January and 2014 November to look for evolutions that may trigger the outflow. Results. Our interferometric observations at low spatial frequencies are compatible with the presence of a hot spot on the photosphere that has a characteristic width of one stellar radius. It appears to be superposed on the smaller scale co...

  18. A binary engine fuelling HD87643' s complex circumstellar environment, using AMBER/VLTI

    CERN Document Server

    Millour, Florentin; Borges-Fernandes, Marcelo; Meilland, Anthony; Mars, Gilbert; Benoist, C; Thiébaut, E; Stee, Philippe; Hofmann, K -H; Baron, Fabien; Young, John R; Bendjoya, Philippe; Carciofi, A C; De Souza, Armando Domiciano; Driebe, Thomas; Jankov, Slobodan; Kervella, Pierre; Petrov, R G; Robbe-Dubois, Sylvie; Vakili, Farrokh; Waters, L B F M; Weigelt, Gerd

    2009-01-01

    Context. The star HD 87643, exhibiting the ?B[e] phenomenon?, has one of the most extreme infrared excesses for this object class. It harbours a large amount of both hot and cold dust, and is surrounded by an extended re?ection nebula. Aims. One of our major goals was to investigate the presence of a companion in HD87643. In addition, the presence of close dusty material was tested through a combination of multi-wavelength high spatial resolution observations. Methods. We observed HD 87643 with high spatial resolution techniques, using the near-IR AMBER/VLTI interferometer with baselines ranging from 60 m to 130 m and the mid-IR MIDI/VLTI interferometer with baselines ranging from 25 m to 65 m. These observations are complemented by NACO/VLT adaptive-optics-corrected images in the K and L-bands, ESO-2.2m optical Wide-Field Imager large-scale images in the B, V and R-bands, Results. We report the direct detection of a companion to HD 87643 by means of image synthesis using the AMBER/VLTI instrument. The presen...

  19. Probing the circumstellar environments of very young low-mass stars using water masers

    Science.gov (United States)

    Terebey, S.; Vogel, S. N.; Myers, P. C.

    1992-01-01

    The VLA is used to search nearby very young low-mass stars for water maser emission. The sample consists of 26 low-luminosity IRAS sources embedded in dense molecular cores, a class of sources suspected to be newly forming low-mass stars on the order of a few hundred thousand years old. Three sources were detected. High spatial resolution maps show the region of maser emission is generally confined to an area smaller than about 0.5 arcsec near the star, and the velocities of individual components span intervals ranging from 20 to 40 km/s. It is inferred from the fact that the maser velocities are too large to be due to gravitational motions in at least two of the sources that the masers are associated with the winds from the young low-mass stars. A comparison of the high spatial resolution maser data to lower-resolution CO data shows no evidence for higher collimation close to the star; the stellar wind cavity appears to have similar collimation at 10 exp 15 cm as at 10 exp 7 to 10 exp 18 cm.

  20. Deconvolution of post-adaptive optics images of faint circumstellar environments by means of the inexact Bregman procedure

    Science.gov (United States)

    Benfenati, A.; La Camera, A.; Carbillet, M.

    2016-02-01

    Aims: High-dynamic range images of astrophysical objects present some difficulties in their restoration because of the presence of very bright point-wise sources surrounded by faint and smooth structures. We propose a method that enables the restoration of this kind of images by taking these kinds of sources into account and, at the same time, improving the contrast enhancement in the final image. Moreover, the proposed approach can help to detect the position of the bright sources. Methods: The classical variational scheme in the presence of Poisson noise aims to find the minimum of a functional compound of the generalized Kullback-Leibler function and a regularization functional: the latter function is employed to preserve some characteristic in the restored image. The inexact Bregman procedure substitutes the regularization function with its inexact Bregman distance. This proposed scheme allows us to take under control the level of inexactness arising in the computed solution and permits us to employ an overestimation of the regularization parameter (which balances the trade-off between the Kullback-Leibler and the Bregman distance). This aspect is fundamental, since the estimation of this kind of parameter is very difficult in the presence of Poisson noise. Results: The inexact Bregman procedure is tested on a bright unresolved binary star with a faint circumstellar environment. When the sources' position is exactly known, this scheme provides us with very satisfactory results. In case of inexact knowledge of the sources' position, it can in addition give some useful information on the true positions. Finally, the inexact Bregman scheme can be also used when information about the binary star's position concerns a connected region instead of isolated pixels.

  1. ISOCAM-CVF spectroscopy of the circumstellar environment of young stellar objects

    CERN Document Server

    Alexander, R D; André, P M; Persi, P; Eiroa, C

    2003-01-01

    We present the results of a mid-infrared imaging spectroscopy survey of Young Stellar Objects (YSOs) and their surrounding environment in four low-mass star formation regions: RCrA, Rho Ophiuchi, Serpens and Chamaeleon I. This survey was performed using ISOCAM and its Circular Variable Filters (CVF) and observed 42 YSO candidates. A number of spectral features were measured, most notably the 9.7um silicate feature, the bending modes of both water and CO2 ices at 6.0 and 15.2um respectively and the well-known unidentified feature at 6.8um. The strength of the unidentified feature was observed to correlate very well with that of the water ice bending mode and far less strongly with the CO2 ice bending mode. This suggests, in a manner consistent with previous observations, that the carrier of the unidentified feature is a strongly polar ice. Absorption profiles of the bending mode of CO2 ice are observed to show a significant long wavelength wing, which suggests that a significant fraction of the CO2 ice observe...

  2. Experimental and Observational Studies of Molecular Hydrogen in Interstellar and Circumstellar Environments

    Science.gov (United States)

    Hoadley, Keri

    2017-08-01

    estimates of the performance of an instrument like CHESS on LUVOIR to study planet-forming environments.

  3. Interstellar and circumstellar fullerenes

    CERN Document Server

    Bernard-Salas, J; Jones, A P; Peeters, E; Micelotta, E R; Otsuka, M; Sloan, G C; Kemper, F; Groenewegen, M

    2014-01-01

    Fullerenes are a particularly stable class of carbon molecules in the shape of a hollow sphere or ellipsoid that might be formed in the outflows of carbon stars. Once injected into the interstellar medium (ISM), these stable species survive and are thus likely to be widespread in the Galaxy where they contribute to interstellar extinction, heating processes, and complex chemical reactions. In recent years, the fullerene species C60 (and to a lesser extent C70) have been detected in a wide variety of circumstellar and interstellar environments showing that when conditions are favourable, fullerenes are formed efficiently. Fullerenes are the first and only large aromatics firmly identified in space. The detection of fullerenes is thus crucial to provide clues as to the key chemical pathways leading to the formation of large complex organic molecules in space, and offers a great diagnostic tool to describe the environment in which they reside. Since fullerenes share many physical properties with PAHs, understand...

  4. Fine Structure in the Circumstellar Environment of a Young, Solar-like Star the Unique Eclipses of KH 15D

    CERN Document Server

    Herbst, W; Vrba, F J; Ibrahimov, M A; Bailer-Jones, C A L; Mundt, R; Lamm, M J; Mazeh, T; Webster, Z T; Haisch, K E; Williams, E C; Rhodes, A H; Balonek, T J; Riffeser, A; Herbst, William; Hamilton, Catrina M.; Vrba, Frederick J.; Ibrahimov, Mansur A.; Bailer-Jones, Coryn A.L.; Mundt, Reinhard; Lamm, Markus; Mazeh, Tsevi; Webster, Zodiac T.; Haisch, Karl E.; Williams, Eric C.; Rhodes, Andrew H.; Balonek, Thomas J.; Riffeser, Alexander Scholz and Arno

    2002-01-01

    Results of an international campaign to photometrically monitor the unique pre-main sequence eclipsing object KH 15D are reported. An updated ephemeris for the eclipse is derived that incorporates a slightly revised period of 48.36 d. There is some evidence that the orbital period is actually twice that value, with two eclipses occurring per cycle. The extraordinary depth (~3.5 mag) and duration (~18 days) of the eclipse indicate that it is caused by circumstellar matter, presumably the inner portion of a disk. The eclipse has continued to lengthen with time and the central brightness reversals are not as extreme as they once were. V-R and V-I colors indicate that the system is slightly bluer near minimum light. Ingress and egress are remarkably well modeled by the passage of a knife-edge across a limb-darkened star. Possible models for the system are briefly discussed.

  5. A multi-wavelength investigation of the radio-loud supernova PTF11qcj and its circumstellar environment

    Energy Technology Data Exchange (ETDEWEB)

    Corsi, A. [Department of Physics, The George Washington University, 725 21st St, NW, Washington, DC 20052 (United States); Ofek, E. O.; Gal-Yam, A.; Xu, D. [Benoziyo Center for Astrophysics, Weizmann Institute of Science, 76100 Rehovot (Israel); Frail, D. A. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Kulkarni, S. R.; Horesh, A.; Carpenter, J.; Arcavi, I.; Cao, Y.; Mooley, K.; Sesar, B. [Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Fox, D. B. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Kasliwal, M. M. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Sullivan, M.; Maguire, K.; Pan, Y.-C. [Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Cenko, S. B. [NASA Goddard Space Flight Center, Code 685, Greenbelt, MD 20771 (United States); Sternberg, A. [Max-Planck-Institut fur Astrophysik, D-85741 Garching (Germany); Bersier, D., E-mail: corsi@gwu.edu [Astrophysics Research Institute, Liverpool John Moores University, Liverpool (United Kingdom); and others

    2014-02-10

    We present the discovery, classification, and extensive panchromatic (from radio to X-ray) follow-up observations of PTF11qcj, a supernova (SN) discovered by the Palomar Transient Factory (PTF). Our observations with the Karl G. Jansky Very Large Array show that this event is radio-loud: PTF11qcj reached a radio peak luminosity comparable to that of the famous gamma-ray-burst-associated SN 1998bw (L {sub 5} {sub GHz} ≈ 10{sup 29} erg s{sup –1} Hz{sup –1}). PTF11qcj is also detected in X-rays with the Chandra Observatory, and in the infrared band with Spitzer. Our multi-wavelength analysis probes the SN interaction with circumstellar material. The radio observations suggest a progenitor mass-loss rate of ∼10{sup –4} M {sub ☉} yr{sup –1} × (v{sub w} /1000 km s{sup –1}), and a velocity of ≈0.3-0.5 c for the fastest moving ejecta (at ≈10 days after explosion). However, these estimates are derived assuming the simplest model of SN ejecta interacting with a smooth circumstellar wind, and do not account for possible inhomogeneities in the medium and asphericity of the explosion. The radio data show deviations from such a simple model, as well as a late-time re-brightening. The X-ray flux from PTF11qcj is compatible with the high-frequency extrapolation of the radio synchrotron emission (within the large uncertainties). A light echo from pre-existing dust is in agreement with our infrared data. Our pre-explosion data from the PTF suggest that a precursor eruption of absolute magnitude M{sub r} ≈ –13 mag may have occurred ≈2.5 yr prior to the SN explosion. Overall, PTF11qcj fits the expectations from the explosion of a Wolf-Rayet star. Precursor eruptions may be a feature characterizing the final pre-explosion evolution of such stars.

  6. The geometry of the close environment of SV Psc as probed by VLTI/MIDI

    CERN Document Server

    Klotz, D; Kerschbaum, F; Paladini, C; Olofsson, H; Hron, J

    2012-01-01

    Context. SV Psc is an asymptotic giant branch (AGB) star surrounded by an oxygen-rich dust envelope. The mm-CO line profile of the object's outflow shows a clear double-component structure. Because of the high angular resolution, mid-IR interferometry may give strong constraints on the origin of this composite profile. Aims. The aim of this work is to investigate the morphology of the environment around SV Psc using high-angular resolution interferometry observations in the mid-IR with the Very Large Telescope MID-infrared Interferometric instrument (VLTI/MIDI). Methods. Interferometric data in the N-band taken at different baseline lengths (ranging from 32-64 m) and position angles (73- 142{\\deg}) allow a study of the morphology of the circumstellar environment close to the star. The data are interpreted on the basis of 2-dimensional, chromatic geometrical models using the fitting software tool GEM-FIND developed for this purpose. Results. The results favor two scenarios: (i) the presence of a highly incline...

  7. CONFIRMATION OF CIRCUMSTELLAR PHOSPHINE

    Energy Technology Data Exchange (ETDEWEB)

    Agúndez, M.; Cernicharo, J. [Instituto de Ciencia de Materiales de Madrid, CSIC, C/ Sor Juana Inés de la Cruz 3, E-28049 Cantoblanco (Spain); Decin, L. [Sterrenkundig Instituut Anton Pannekoek, University of Amsterdam, Science Park 904, NL-1098 Amsterdam (Netherlands); Encrenaz, P. [LERMA, Observatoire de Paris, 61 Av. de l' Observatoire, F-75014 Paris (France); Teyssier, D. [European Space Astronomy Centre, Urb. Villafranca del Castillo, P.O. Box 50727, E-28080 Madrid (Spain)

    2014-08-01

    Phosphine (PH{sub 3}) was tentatively identified a few years ago in the carbon star envelopes IRC +10216 and CRL 2688 from observations of an emission line at 266.9 GHz attributable to the J = 1-0 rotational transition. We report the detection of the J = 2-1 rotational transition of PH{sub 3} in IRC +10216 using the HIFI instrument on board Herschel, which definitively confirms the identification of PH{sub 3}. Radiative transfer calculations indicate that infrared pumping in excited vibrational states plays an important role in the excitation of PH{sub 3} in the envelope of IRC +10216, and that the observed lines are consistent with phosphine being formed anywhere between the star and 100 R {sub *} from the star, with an abundance of 10{sup –8} relative to H{sub 2}. The detection of PH{sub 3} challenges chemical models, none of which offer a satisfactory formation scenario. Although PH{sub 3} holds just 2% of the total available phosphorus in IRC +10216, it is, together with HCP, one of the major gas phase carriers of phosphorus in the inner circumstellar layers, suggesting that it could also be an important phosphorus species in other astronomical environments. This is the first unambiguous detection of PH{sub 3} outside the solar system, and is a further step toward a better understanding of the chemistry of phosphorus in space.

  8. A person in a closed environment as a psychological problem

    Directory of Open Access Journals (Sweden)

    YuliyaV. Klochko

    2013-12-01

    Full Text Available This article addresses an ethically weighted problem which is related to modern psychology: when a person lives in a closed environment. A new approach to solving this problem is being examined. It is based on the finding of substantial new functional aspects of the cognitive processes of making and losing meaning. The study of this sub-discipline started with O.K. Tikhomirov’s theory of thinking. The phenomenon of “adaptability to changes in lifestyle” is being analyzed. The substantial characteristics of the notion of a “closed environment” as well as the psychological manifestations which appear when one is forced to live in a closed environment or choses to live in one of his or her own volition are being revealed. According to the author, the new approach will allow us to come closer to understanding and being able to explain the psychological mechanisms of the mental upheaval which prisoners in solitary confinement experience.

  9. The coronagraphic Modal Wavefront Sensor: a hybrid focal-plane sensor for the high-contrast imaging of circumstellar environments

    CERN Document Server

    Wilby, Michael J; Snik, Frans; Korkiakoski, Visa; Pietrow, Alexander G M

    2016-01-01

    The raw coronagraphic performance of current high-contrast imaging instruments is limited by the presence of a quasi-static speckle (QSS) background, resulting from instrumental non-common path errors (NCPEs). Rapid development of efficient speckle subtraction techniques in data reduction has enabled final contrasts of up to 10-6 to be obtained, however it remains preferable to eliminate the underlying NCPEs at the source. In this work we introduce the coronagraphic Modal Wavefront Sensor (cMWS), a new wavefront sensor suitable for real-time NCPE correction. This pupil-plane optic combines the apodizing phase plate coronagraph with a holographic modal wavefront sensor, to provide simultaneous coronagraphic imaging and focal-plane wavefront sensing using the science point spread function. We first characterise the baseline performance of the cMWS via idealised closed-loop simulations, showing that the sensor successfully recovers diffraction-limited coronagraph performance over an effective dynamic range of +/...

  10. The coronagraphic Modal Wavefront Sensor: a hybrid focal-plane sensor for the high-contrast imaging of circumstellar environments

    Science.gov (United States)

    Wilby, M. J.; Keller, C. U.; Snik, F.; Korkiakoski, V.; Pietrow, A. G. M.

    2017-01-01

    The raw coronagraphic performance of current high-contrast imaging instruments is limited by the presence of a quasi-static speckle (QSS) background, resulting from instrumental Non-Common Path Errors (NCPEs). Rapid development of efficient speckle subtraction techniques in data reduction has enabled final contrasts of up to 10-6 to be obtained, however it remains preferable to eliminate the underlying NCPEs at the source. In this work we introduce the coronagraphic Modal Wavefront Sensor (cMWS), a new wavefront sensor suitable for real-time NCPE correction. This combines the Apodizing Phase Plate (APP) coronagraph with a holographic modal wavefront sensor to provide simultaneous coronagraphic imaging and focal-plane wavefront sensing with the science point-spread function. We first characterise the baseline performance of the cMWS via idealised closed-loop simulations, showing that the sensor is able to successfully recover diffraction-limited coronagraph performance over an effective dynamic range of ±2.5 radians root-mean-square (rms) wavefront error within 2-10 iterations, with performance independent of the specific choice of mode basis. We then present the results of initial on-sky testing at the William Herschel Telescope, which demonstrate that the sensor is capable of NCPE sensing under realistic seeing conditions via the recovery of known static aberrations to an accuracy of 10 nm (0.1 radians) rms error in the presence of a dominant atmospheric speckle foreground. We also find that the sensor is capable of real-time measurement of broadband atmospheric wavefront variance (50% bandwidth, 158 nm rms wavefront error) at a cadence of 50 Hz over an uncorrected telescope sub-aperture. When combined with a suitable closed-loop adaptive optics system, the cMWS holds the potential to deliver an improvement of up to two orders of magnitude over the uncorrected QSS floor. Such a sensor would be eminently suitable for the direct imaging and spectroscopy of

  11. An interferometric study of the post-AGB binary 89 Herculis I Spatially resolving the continuum circumstellar environment at optical and near-IR wavelengths with the VLTI, NPOI, IOTA, PTI, and the CHARA Array

    CERN Document Server

    Hillen, M; Van Winckel, H; Chesneau, O; Hummel, C A; Monnier, J D; Farrington, C; Tycner, C; Mourard, D; Brummelaar, T ten; Banerjee, D P K; Zavala, R T

    2013-01-01

    Binary post-AGB stars are interesting laboratories to study both the evolution of binaries as well as the structure of circumstellar disks. A multiwavelength high angular resolution study of the prototypical object 89 Herculis is performed with the aim of identifying and locating the different emission components seen in the SED. A large interferometric data set, collected over the past decade and covering optical and near-IR wavelengths, is analyzed with simple geometric models. Combining the interferometric constraints with the photometry and the optical spectra, we reassess the energy budget of the post-AGB star and its circumstellar environment. We report the first (direct) detection of a large (35-40%) optical circumstellar flux contribution and spatially resolve its emission region. Given this large amount of reprocessed and/or redistributed optical light, the fitted size of the emission region is rather compact and fits with(in) the inner rim of the circumbinary dust disk. This rim dominates our K band...

  12. Composite circumstellar dust grains

    Science.gov (United States)

    Gupta, Ranjan; Vaidya, Dipak B.; Dutta, Rajeshwari

    2016-10-01

    We calculate the absorption efficiencies of composite silicate grains with inclusions of graphite and silicon carbide in the spectral range 5-25 μm. We study the variation in absorption profiles with volume fractions of inclusions. In particular we study the variation in the wavelength of peak absorption at 10 and 18 μm. We also study the variation of the absorption of porous silicate grains. We use the absorption efficiencies to calculate the infrared flux at various dust temperatures and compare with the observed infrared emission flux from the circumstellar dust around some M-type and asymptotic giant branch stars obtained from IRAS and a few stars from Spitzer satellite. We interpret the observed data in terms of the circumstellar dust grain sizes, shape, composition and dust temperature.

  13. Composite Circumstellar Dust Grains

    CERN Document Server

    Gupta, Ranjan; Dutta, Rajeshwari

    2016-01-01

    We calculate the absorption efficiencies of composite silicate grains with inclusions of graphite and silicon carbide in the spectral range 5--25$\\rm \\mu m$. We study the variation in absorption profiles with volume fractions of inclusions. In particular we study the variation in the wavelength of peak absorption at 10 and 18$\\rm \\mu m$. We also study the variation of the absorption of porous silicate grains. We use the absorption efficiencies to calculate the infrared flux at various dust temperatures and compare with the observed infrared emission flux from the circumstellar dust around some M-Type \\& AGB stars obtained from IRAS and a few stars from Spitzer satellite. We interpret the observed data in terms of the circumstellar dust grain sizes; shape; composition and dust temperature.

  14. The ecology of micro-organisms in a closed environment

    Science.gov (United States)

    Fox, L.

    1971-01-01

    Microorganisms under closed environmental ecological conditions with reference to astronauts infectious diseases, discussing bacteria growth in Biosatellite 2 and earth based closed chamber experiments

  15. Cardiovascular disease occurrence in two close but different social environments

    Directory of Open Access Journals (Sweden)

    Honkasalo Marja-Liisa

    2011-01-01

    Full Text Available Abstract Background Cardiovascular diseases estimate to be the leading cause of death and loss of disability-adjusted life years globally. Conventional risk factors for cardiovascular diseases only partly account for the social gradient. The purpose of this study was to compare the occurrence of the most frequent cardiovascular diseases and cardiovascular mortality in two close cities, the Twin cities. Methods We focused on the total population in two neighbour and equally sized cities with a population of around 135 000 inhabitants each. These twin cities represent two different social environments in the same Swedish county. According to their social history they could be labelled a "blue-collar" and a "white-collar" city. Morbidity data for the two cities was derived from an administrative health care register based on medical records assigned by the physicians at both hospitals and primary care. The morbidity data presented are cumulative incidence rates and the data on mortality for ischemic heart diseases is based on official Swedish statistics. Results The cumulative incidence of different cardiovascular diagnoses for younger and also elderly men and women revealed significantly differences for studied cardiovascular diagnoses. The occurrence rates were in all aspects highest in the population of the "blue-collar" twin city for both sexes. Conclusions This study revealed that there are significant differences in risk for cardiovascular morbidity and mortality between the populations in the studied different social environments. These differences seem to be profound and stable over time and thereby give implication for public health policy to initiate a community intervention program in the "blue-collar" twin city.

  16. On the environment surrounding close-in exoplanets

    CERN Document Server

    Vidotto, A A; Jardine, M; Moutou, C; Donati, J -F

    2015-01-01

    Exoplanets in extremely close-in orbits are immersed in a local interplanetary medium (i.e., the stellar wind) much denser than the local conditions encountered around the solar system planets. The environment surrounding these exoplanets also differs in terms of dynamics (slower stellar winds, but higher Keplerian velocities) and ambient magnetic fields (likely higher for host stars more active than the Sun). Here, we quantitatively investigate the nature of the interplanetary media surrounding the hot Jupiters HD46375b, HD73256b, HD102195b, HD130322b, HD179949b. We simulate the three-dimensional winds of their host stars, in which we directly incorporate their observed surface magnetic fields. With that, we derive mass-loss rates (1.9 to 8.0 $\\times 10^{-13} M_{\\odot}$/yr) and the wind properties at the position of the hot-Jupiters' orbits (temperature, velocity, magnetic field intensity and pressure). We show that these exoplanets' orbits are super-magnetosonic, indicating that bow shocks are formed surrou...

  17. On the environment surrounding close-in exoplanets

    Science.gov (United States)

    Vidotto, A. A.; Fares, R.; Jardine, M.; Moutou, C.; Donati, J.-F.

    2015-06-01

    Exoplanets in extremely close-in orbits are immersed in a local interplanetary medium (i.e. the stellar wind) much denser than the local conditions encountered around the Solar system planets. The environment surrounding these exoplanets also differs in terms of dynamics (slower stellar winds, but higher Keplerian velocities) and ambient magnetic fields (likely higher for host stars more active than the Sun). Here, we quantitatively investigate the nature of the interplanetary media surrounding the hot Jupiters HD 46375b, HD 73256b, HD 102195b, HD 130322b and HD 179949b. We simulate the three-dimensional winds of their host stars, in which we directly incorporate their observed surface magnetic fields. With that, we derive mass-loss rates (1.9-8.0 × 10-13 M⊙ yr-1) and the wind properties at the position of the hot Jupiters' orbits (temperature, velocity, magnetic field intensity and pressure). We show that these exoplanets' orbits are supermagnetosonic, indicating that bow shocks are formed surrounding these planets. Assuming planetary magnetic fields similar to Jupiter's, we estimate planetary magnetospheric sizes of 4.1-5.6 planetary radii. We also derive the exoplanetary radio emission released in the dissipation of the stellar wind energy. We find radio fluxes ranging from 0.02 to 0.13 mJy, which are challenging to be observed with present-day technology, but could be detectable with future higher sensitivity arrays (e.g. Square Kilometre Array). Radio emission from systems having closer hot Jupiters, such as from τ Boo b or HD 189733b, or from nearby planetary systems orbiting young stars, are likely to have higher radio fluxes, presenting better prospects for detecting exoplanetary radio emission.

  18. Toward Comprehensive Physical/Chemical Understanding of the Circumstellar Environments - Simultaneous Probing of Each of the Ionized/Atomic/Molecular Gas and Dust Components

    Science.gov (United States)

    Ueta, Toshiya

    We propose to continue our successful investigations into simultaneous probing of each of the ionized/atomic/molecular gas and dust components in planetary nebulae using primarily far-IR broadband images and spatially-resolved spectroscopic data cubes obtained with the Herschel Space Observatory to enhance our understanding of the circumstellar environments. This research originally started as the Herschel Planetary Nebula Survey (HerPlaNS) - an open time 1 program of the Herschel Space Observatory - in which 11 high-excitation PNs were observed to study the nebular energetics that involves very hot X-ray emitting plasma to very cold dust grains, whose density ranges over 3 to 4 orders of magnitude and temperature ranges over 7 orders of magnitude. The HerPlaNS data include broadband maps, IFU spectral data cubes, and bolometer array spectral data cubes covering 50 to 670 microns. Because of the sheer volume and complexity of the data set, the original funding was exhausted almost exclusively to the initial data reduction and not much to the subsequent science analysis. However, we managed to perform a nearly full science analysis for one target, NGC 6781, for which the broadband maps confirm the nearly pole-on barrel structure of the amorphous carbonrich dust shell and the surrounding halo having temperatures of 26-40 K. We also demonstrated that spatially resolved far-IR line diagnostics would yield the (Te, ne) profiles, from which distributions of ionized, atomic, and molecular gases can be determined. Direct comparison of the dust and gas column mass maps constrained by the HerPlaNS data allowed to construct an empirical gas-to-dust mass ratio map, which shows a range of ratios with the median of 195 with a standard deviation of 110. The analysis also yielded estimates of the total mass of the shell to be 0.86 M_sun, consisting of 0.54 M_sun of ionized gas, 0.12 M_sun of atomic gas, 0.2 M_sun of molecular gas, and 0.004 M_sun of dust grains. These estimates

  19. Confirmation of circumstellar phosphine

    CERN Document Server

    Agundez, M; Decin, L; Encrenaz, P; Teyssier, D

    2014-01-01

    Phosphine (PH3) was tentatively identified a few years ago in the carbon star envelopes IRC+10216 and CRL2688 from observations of an emission line at 266.9 GHz attributable to the J=1-0 rotational transition. We report the detection of the J=2-1 rotational transition of PH3 in IRC+10216 using the HIFI instrument on board Herschel, which definitively confirms the identification of PH3. Radiative transfer calculations indicate that infrared pumping to excited vibrational states plays an important role in the excitation of PH3 in the envelope of IRC+10216, and that the observed lines are consistent with phosphine being formed anywhere between the star and 100 R* from the star, with an abundance of 1e-8 relative to H2. The detection of PH3 challenges chemical models, none of which offers a satisfactory formation scenario. Although PH3 locks just 2 % of the total available phosphorus in IRC+10216, it is together with HCP, one of the major gas phase carriers of phosphorus in the inner circumstellar layers, suggest...

  20. Multi-agent framework for negotiation in a closed environment

    Science.gov (United States)

    Cretan, Adina; Coutinho, Carlos; Bratu, Ben; Jardim-Goncalves, Ricardo

    2013-10-01

    The goal of this paper is to offer support for small and medium enterprises which cannot or do not want to fulfill a big contract alone. Each organization has limited resources and in order to better accomplish a higher external demand, the managers are forced to outsource parts of their contracts even to concurrent organizations. In this concurrent environment each enterprise wants to preserve its decision autonomy and to disclose as little as possible from its business information. To describe this interaction, our approach is to define a framework for managing parallel and concurrent negotiations among independent organizations acting in the same industrial market. The complexity of our negotiation framework is done by the dynamic environment in which multi-attribute and multi-participant negotiations are racing over the same set of resources. Moreover, the proposed framework helps the organizations within the collaborative networked environment to augment their efficiency and ability to react to unforeseen situations, thus improving their market competitiveness.

  1. Environment induced time arrow and the Closed Time Path method

    Science.gov (United States)

    Polonyi, Janos

    2013-06-01

    It is shown in the framework of a harmonic system that the thermodynamical time arrow is induced by the environmental initial conditions in a manner similar to spontaneous symmetry breaking. The Closed Time Path formalism is introduced in classical mechanics to handle Green functions for initial condition problems by the action principle, in a systematic manner. The application of this scheme for quantum systems shows the common dynamical origin of the thermodynamical and the quantum time arrows. It is furthermore conjectured that the quantum-classical transition is strongly coupled.

  2. EEG workload prediction in a closed-loop learning environment

    OpenAIRE

    2015-01-01

    The issues of developing an online EEG-based adaptive learning environment are examined in this thesis. The aim is to adapt instructional learning material in real-time, to support learners in their individual learning process and keep them in their optimal workload capacity range during learning. First, suitable learning material is designed, which does not cause artifacts and induces confounds in the EEG data. Second, the most suitable features for an online workload detection in EEG data a...

  3. Modeling and control for closed environment plant production systems

    Science.gov (United States)

    Fleisher, David H.; Ting, K. C.; Janes, H. W. (Principal Investigator)

    2002-01-01

    A computer program was developed to study multiple crop production and control in controlled environment plant production systems. The program simulates crop growth and development under nominal and off-nominal environments. Time-series crop models for wheat (Triticum aestivum), soybean (Glycine max), and white potato (Solanum tuberosum) are integrated with a model-based predictive controller. The controller evaluates and compensates for effects of environmental disturbances on crop production scheduling. The crop models consist of a set of nonlinear polynomial equations, six for each crop, developed using multivariate polynomial regression (MPR). Simulated data from DSSAT crop models, previously modified for crop production in controlled environments with hydroponics under elevated atmospheric carbon dioxide concentration, were used for the MPR fitting. The model-based predictive controller adjusts light intensity, air temperature, and carbon dioxide concentration set points in response to environmental perturbations. Control signals are determined from minimization of a cost function, which is based on the weighted control effort and squared-error between the system response and desired reference signal.

  4. Far-UV Spectroscopy of the Planet-hosting Star WASP-13: High-energy Irradiance, Distance, Age, Planetary Mass-loss Rate, and Circumstellar Environment

    Science.gov (United States)

    Fossati, L.; France, K.; Koskinen, T.; Juvan, I. G.; Haswell, C. A.; Lendl, M.

    2015-12-01

    Several transiting hot Jupiters orbit relatively inactive main-sequence stars. For some of those, the {log}{R}{HK}\\prime activity parameter lies below the basal level (-5.1). Two explanations have been proposed so far: (i) the planet affects the stellar dynamo, (ii) the {log}{R}{HK}\\prime measurements are biased by extrinsic absorption, either by the interstellar medium (ISM) or by material local to the system. We present here Hubble Space Telescope/COS far-UV spectra of WASP-13, which hosts an inflated hot Jupiter and has a measured {log}{R}{HK}\\prime value (-5.26), well below the basal level. From the star’s spectral energy distribution we obtain an extinction E(B - V) = 0.045 ± 0.025 mag and a distance d = 232 ± 8 pc. We detect at ≳4σ lines belonging to three different ionization states of carbon (C i, C ii, and C iv) and the Si iv doublet at ˜3σ. Using far-UV spectra of nearby early G-type stars of known age, we derive a C iv/C i flux ratio-age relation, from which we estimate WASP-13's age to be 5.1 ± 2.0 Gyr. We rescale the solar irradiance reference spectrum to match the flux of the C iv 1548 doublet. By integrating the rescaled solar spectrum, we obtain an XUV flux at 1 AU of 5.4 erg s-1 cm-2. We use a detailed model of the planet’s upper atmosphere, deriving a mass-loss rate of 1.5 × 1011 g s-1. Despite the low {log}{R}{HK}\\prime value, the star shows a far-UV spectrum typical of middle-aged solar-type stars, pointing toward the presence of significant extrinsic absorption. The analysis of a high-resolution spectrum of the Ca ii H&K lines indicates that the ISM absorption could be the origin of the low {log}{R}{HK}\\prime value. Nevertheless, the large uncertainty in the Ca ii ISM abundance does not allow us to firmly exclude the presence of circumstellar gas. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from MAST at the Space Telescope Science Institute, which is operated by the Association of Universities

  5. The Circumstellar Disk of the Butterfly Star in Taurus

    CERN Document Server

    Wolf, S; Stapelfeldt, K R; Wolf, Sebastian; Padgett, Deborah L.; Stapelfeldt, Karl R.

    2003-01-01

    We present a model of the circumstellar environment of the so-called ``Butterfly Star'' in Taurus (IRAS 04302+2247). The appearance of this young stellar object is dominated by a large circumstellar disk seen edge-on and the light scattering lobes above the disk. The model is based on multi-wavelength continuum observations: Millimeter maps and high-resolution near-infrared images obtained with HST/NICMOS. It was found that the disk and envelope parameters are comparable with those of the circumstellar environment of other young stellar objects. A main result is that the dust properties must be different in the circumstellar disk and in the envelope: While a grain size distribution with grain radii up to 100 micron is required to reproduce the millimeter observations of the disk, the envelope is dominated by smaller grains similar to those of the interstellar medium. Preprint with high figure quality available at: http://spider.ipac.caltech.edu/staff/swolf/homepage/public/preprints/i04302.ps

  6. Titanium carbide nanocrystals in circumstellar environments

    NARCIS (Netherlands)

    von Helden, G; Tielens, ACGM; van Heijnsbergen, D; Duncan, MA; Hony, S; Waters, LBFM; Meijer, G.

    2000-01-01

    Meteorites contain micrometer-sized graphite grains with embedded titanium carbide grains. Although isotopic analysis identifies asymptotic giant branch stars as the birth sites of these grains, there is no direct observational identification of these grains in astronomical sources. We report that i

  7. Titanium carbide nanocrystals in circumstellar environments.

    Science.gov (United States)

    von Helden, G; Tielens, A G; van Heijnsbergen, D; Duncan, M A; Hony, S; Waters, L B; Meijer, G

    2000-04-14

    Meteorites contain micrometer-sized graphite grains with embedded titanium carbide grains. Although isotopic analysis identifies asymptotic giant branch stars as the birth sites of these grains, there is no direct observational identification of these grains in astronomical sources. We report that infrared wavelength spectra of gas-phase titanium carbide nanocrystals derived in the laboratory show a prominent feature at a wavelength of 20.1 micrometers, which compares well to a similar feature in observed spectra of postasymptotic giant branch stars. It is concluded that titanium carbide forms during a short (approximately 100 years) phase of catastrophic mass loss (>0.001 solar masses per year) in dying, low-mass stars.

  8. Titanium carbide nanocrystals in circumstellar environments

    NARCIS (Netherlands)

    von Helden, G.; Tielens, Acgm; van Heijnsbergen, D.; Duncan, M. A.; Hony, S.; Waters, Lbfm; Meijer, G.

    2000-01-01

    Meteorites contain micrometer-sized graphite grains with embedded titanium carbide grains. Although isotopic analysis identifies asymptotic giant branch stars as the birth sites of these grains, there is no direct observational identification of these grains in astronomical sources. We report that i

  9. Technology Enhanced Learning Environments for Closing the Gap in Student Achievement between Regions: Does It Work?

    Science.gov (United States)

    Cakir, Hasan; Delialioglu, Omer; Dennis, Alan; Duffy, Thomas

    2009-01-01

    Student achievement gap between urban and suburban regions are a major issue in U.S. schools. Technology enhanced learning environments that support teaching and learning process with advanced technology may close this achievement gap. This paper examines the impact of student and school factors with an emphasis on schools' geographic location on…

  10. Investigating the Contextual Interference Effect Using Combination Sports Skills in Open and Closed Skill Environments

    Directory of Open Access Journals (Sweden)

    Jadeera P.G. Cheong, Brendan Lay, Rizal Razman

    2016-03-01

    Full Text Available This study attempted to present conditions that were closer to the real-world setting of team sports. The primary purpose was to examine the effects of blocked, random and game-based training practice schedules on the learning of the field hockey trap, close dribble and push pass that were practiced in combination. The secondary purpose was to investigate the effects of predictability of the environment on the learning of field hockey sport skills according to different practice schedules. A game-based training protocol represented a form of random practice in an unstable environment and was compared against a blocked and a traditional random practice schedule. In general, all groups improved dribble and push accuracy performance during the acquisition phase when assessed in a closed environment. In the retention phase, there were no differences between the three groups. When assessed in an open skills environment, all groups improved their percentage of successful executions for trapping and passing execution, and improved total number of attempts and total number of successful executions for both dribbling and shooting execution. Between-group differences were detected for dribbling execution with the game-based group scoring a higher number of dribbling successes. The CI effect did not emerge when practicing and assessing multiple sport skills in a closed skill environment, even when the skills were practiced in combination. However, when skill assessment was conducted in a real-world situation, there appeared to be some support for the CI effect.

  11. CIRCUMSTELLAR ABSORPTION IN DOUBLE DETONATION TYPE Ia SUPERNOVAE

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Ken J. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Guillochon, James [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Foley, Ryan J., E-mail: kenshen@astro.berkeley.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2013-06-20

    Upon formation, degenerate He core white dwarfs are surrounded by a radiative H-rich layer primarily supported by ideal gas pressure. In this Letter, we examine the effect of this H-rich layer on mass transfer in He+C/O double white dwarf binaries that will eventually merge and possibly yield a Type Ia supernova (SN Ia) in the double detonation scenario. Because its thermal profile and equation of state differ from the underlying He core, the H-rich layer is transferred stably onto the C/O white dwarf prior to the He core's tidal disruption. We find that this material is ejected from the binary system and sweeps up the surrounding interstellar medium hundreds to thousands of years before the SN Ia. The close match between the resulting circumstellar medium profiles and values inferred from recent observations of circumstellar absorption in SNe Ia gives further credence to the resurgent double detonation scenario.

  12. High Resolution Spectroscopy of Vega-like Stars: Abundances and Circumstellar Gas

    Science.gov (United States)

    Dunkin, S. K.; Barlow, M. J.; Ryan, Sean G.

    1996-01-01

    Vega-like stars are main-sequence stars exhibiting excess infrared emission. In an effort to improve the information available on this class of star, 13 stars have been analyzed which have been classed as Vega-like, or have an infra-red excess attributable to dust in their circumstellar environment. In a separate paper stellar properties such as effective temperature and log g have been derived and in this poster we highlight the results of the photospheric abundance analysis also carried out during this work. King recently drew attention to the possible link between Vega-like stars and the photospheric metal-depleted class of A-stars, the Lambda Bootis stars. Since Vega-like stars are thought to have disks of dust, it might be expected that accretion of depleted gas onto the surface of these stars may cause this same phenomenon. In the 6 stars studied for depletions, none showed the extreme underabundance patterns observed in Lambda Bootis stars. However, depletions of silicon and magnesium were found in two of the sample, suggesting that these elements are in silicate dust grains in the circumstellar environment of these stars. Absorption lines attributed to circumstellar gas have been positively identified in three stars in our sample. Individual cases show evidence either of high-velocity outflowing gas, variability in the circumstellar lines observed, or evidence of circumstellar gas in excited lines of Fe II. No previous identification of circumstellar material has been made for two of the stars in question.

  13. Activity Budgets of Impala (Aepyceros melampus in Closed Environments: The Mukuvisi Woodland Experience, Zimbabwe

    Directory of Open Access Journals (Sweden)

    Muposhi Victor Kurauwone

    2013-01-01

    Full Text Available Activity pattern plasticity in ungulates serves as an evolutionary adaptation to optimize fitness in inconsistent environments. Given that time is a limited and valuable resource for foraging wildlife species, provisioning and attraction may affect the activity pattern plasticity and reduce complexities of time partitioning for different activities by impala in closed environments. We assessed activity budgets of free-ranging impala social groups in a closed environment. Social group type had an influence on the activity budgets of impala except for foraging and moving activity states. Both the harem and bachelor groups spent more than 30% of their daily time foraging. Bachelor groups spent more time exhibiting vigilance tendencies than the harem groups. Season influenced the activity budgets of social groups other than vigilance and foraging activity states. Foraging time was highly correlated with vigilance, resting, and grooming. We concluded that provisioning and attraction may have reduced the influence of seasonality on the proportion of time spent on different activity states by impala social groups. There is a need to establish long-term socioecological, physiological, and reproductive consequences of provisioning and habituation on impala under closed environments.

  14. SMA Continuum Survey of Circumstellar Disks in Serpens

    Science.gov (United States)

    Law, Charles; Ricci, Luca; Andrews, Sean M.; Wilner, David J.; Qi, Chunhua

    2017-06-01

    The lifetime of disks surrounding pre-main-sequence stars is closely linked to planet formation and provides information on disk dispersal mechanisms and dissipation timescales. The potential for these optically thick, gas-rich disks to form planets is critically dependent on how much dust is available to be converted into terrestrial planets and rocky cores of giant planets. For this reason, an understanding of how dust mass varies with key properties such as stellar mass, age, and environment is critical for understanding planet formation. Millimeter wavelength observations, in which the dust emission is optically thin, are required to study the colder dust residing in the disk’s outer regions and to measure disk dust masses. Hence, we have obtained SMA 1.3 mm continuum observations of 62 Class II sources with suspected circumstellar disks in the Serpens star-forming region (SFR). Relative to the well-studied Taurus SFR, Serpens allows us to probe the distribution of dust masses for disks in a much denser and more clustered environment. Only 13 disks were detected in the continuum with the SMA. We calculate the total dust masses of these disks and compare their masses to those of disks in Taurus, Lupus, and Upper Scorpius. We do not find evidence of diminished dust masses in Serpens disks relative to those in Taurus despite the fact that disks in denser clusters may be expected to contain less dust mass due to stronger and more frequent tidal interactions that can disrupt the outer regions of disks. However, considering the low detection fraction, we likely detected only bright continuum sources and a more sensitive survey of Serpens would help clarify these results.

  15. External Shaping of Circumstellar Envelopes of Evolved Stars

    Science.gov (United States)

    Cox, N. L. J.

    2015-08-01

    The circumstellar envelopes of asymptotic giant branch (AGB) stars and red supergiants (RSGs) are complex chemical and physical environments, and the specifics of their mass-loss history are important for both stellar and galactic evolution. One key aspect in this is to understand how the circumstellar medium of these stars can be shaped and affected by both internal and external mechanisms. These influences can skew our view on the (dust) chemistry and mass-loss history of these stars, and hence their role in the chemical enrichment of galaxies. This contribution focuses on the external mechanism related to the interaction between the slow dusty stellar wind and the local ambient medium. I will discuss what recent observations and hydrodynamical simulations have revealed and how these can help us learn more about AGB stars and RSGs, as well as the interstellar medium (ISM).

  16. Circumstellar Shells in Absorption in Type Ia Supernovae

    CERN Document Server

    Borkowski, K J; Reynolds, S P

    2009-01-01

    Progenitors of Type Ia supernovae (SNe) have been predicted to modify their ambient circumstellar (CSM) and interstellar environments through the action of their powerful winds. While there is X-ray and optical evidence for circumstellar interaction in several remnants of Type Ia SNe, widespread evidence for such interaction in Type Ia SNe themselves has been lacking. We consider prospects for detection of CSM shells that have been predicted to be common around Type Ia SNe. Such shells are most easily detected in Na I absorption lines. Variable (declining) absorption is expected to occur soon after the explosion, primarily during the SN rise time, for shells located within 1 - 10 pc of a SN. The distance of the shell from the SN can be determined by measuring the time scale for line variability.

  17. Polarimetric microlensing of circumstellar disks

    CERN Document Server

    Sajadian, Sedighe

    2015-01-01

    We study the benefits of polarimetry observations of microlensing events to detect and characterize circumstellar disks around the microlensed stars located at the Galactic bulge. These disks which are unresolvable from their host stars make a net polarization effect due to their projected elliptical shapes. Gravitational microlensing can magnify these signals and make them be resolved. The main aim of this work is to determine what extra information about these disks can be extracted from polarimetry observations of microlensing events in addition to those given by photometry ones. Hot disks which are closer to their host stars are more likely to be detected by microlensing, owing to more contributions in the total flux. By considering this kind of disks, we show that although the polarimetric efficiency for detecting disks is similar to the photometric observation, but polarimetry observations can help to constraint the disk geometrical parameters e.g. the disk inner radius and the lens trajectory with resp...

  18. Closing the Loop: Integrating Body, Muscle and Environment with Locomotion Central Pattern Generators

    Science.gov (United States)

    2013-06-30

    simple closed-loop model in which a CPG produces a pattern of muscle activation which is modified by sensory feedback related to body curvature . (a...by a complex interaction of the neural circuits in the spinal cord and brain, the body, the muscles, sensory organs and the environment. With- out...feedback related to body curvature . 2.1 Computation of optimal feedback for the control of locomotion We have a developed a general method of computing

  19. Small carbon chains in circumstellar envelopes

    CERN Document Server

    Hargreaves, R J; Bernath, P F

    2014-01-01

    Observations were made for a number of carbon-rich circumstellar envelopes using the Phoenix spectrograph on the Gemini South telescope to determine the abundance of small carbon chain molecules. Vibration-rotation lines of the $\

  20. The Structure of Brown Dwarf Circumstellar Disks

    OpenAIRE

    Walker, Christina; Wood, Kenneth; Lada, C. J.; Robitaille, Thomas; Bjorkman, J. E.; Whitney, Barbara

    2004-01-01

    We present synthetic spectra for circumstellar disks that are heated by radiation from a central brown dwarf. Under the assumption of vertical hydrostatic equilibrium, our models yield scaleheights for brown dwarf disks in excess of three times those derived for classical T Tauri (CTTS) disks. If the near-IR excess emission observed from brown dwarfs is indeed due to circumstellar disks, then the large scaleheights we find could have a significant impact on the optical and near-IR detectabili...

  1. Circumstellar Molecular Spectra towards Evolved Stars

    CERN Document Server

    Bakker, E J

    1997-01-01

    In this paper we discuss the relevance of, and possible scientific gains which can be acquired from studying circumstellar molecular spectra toward evolved stars. Where can we expect circumstellar molecular spectra, why would we want to study these spectra, which molecules might be present, and what can we learn from these studies? We present an overview of reported detections, and discuss some of the results.

  2. Tracing Planets in Circumstellar Discs

    Directory of Open Access Journals (Sweden)

    Uribe Ana L.

    2013-04-01

    Full Text Available Planets are assumed to form in circumstellar discs around young stellar objects. The additional gravitational potential of a planet perturbs the disc and leads to characteristic structures, i.e. spiral waves and gaps, in the disc density profile. We perform a large-scale parameter study on the observability of these planet-induced structures in circumstellar discs in the (submm wavelength range for the Atacama Large (SubMillimeter Array (ALMA. On the basis of hydrodynamical and magneto-hydrodynamical simulations of star-disc-planet models we calculate the disc temperature structure and (submm images of these systems. These are used to derive simulated ALMA maps. Because appropriate objects are frequent in the Taurus-Auriga region, we focus on a distance of 140 pc and a declination of ≈ 20°. The explored range of star-disc-planet configurations consists of six hydrodynamical simulations (including magnetic fields and different planet masses, nine disc sizes with outer radii ranging from 9 AU to 225 AU, 15 total disc masses in the range between 2.67·10-7 M⊙ and 4.10·10-2 M⊙, six different central stars and two different grain size distributions, resulting in 10 000 disc models. At almost all scales and in particular down to a scale of a few AU, ALMA is able to trace disc structures induced by planet-disc interaction or the influence of magnetic fields in the wavelength range between 0.4...2.0 mm. In most cases, the optimum angular resolution is limited by the sensitivity of ALMA. However, within the range of typical masses of protoplane tary discs (0.1 M⊙...0.001 M⊙ the disc mass has a minor impact on the observability. At the distance of 140 pc it is possible to resolve discs down to 2.67·10-6 M⊙ and trace gaps in discs with 2.67·10-4 M⊙ with a signal-to-noise ratio greater than three. In general, it is more likely to trace planet-induced gaps in magneto-hydrodynamical disc models, because gaps are wider in the presence of

  3. Germination of white radish, buckwheat and qing-geng-cai under low pressure in closed environment.

    Science.gov (United States)

    Hinokuchi, Tsutomu; Oshima, Satoshi; Hashimoto, Hirofumi

    2004-11-01

    In order to cultivate plants under low pressure in closed environment, the germination rate of seeds of white radish was investigated under low pressure, low oxygen partial pressure and condition of pure oxygen. The result of these experiments showed that the germination rate was affected by the oxygen partial pressure. From this fact, it is possible to lower the total pressure by using only the pure oxygen in germination. Furthermore, the germination rates of seeds of buckwheat and qing-geng-cai were also investigated in pure oxygen for the comparison. Consequently, though tendency in germination rate of white radish was similar to qing-geng-cai, it was different from buckwheat.

  4. CLOSE RANGE CALIBRATION OF LONG FOCAL LENGTH LENSES IN A CHANGING ENVIRONMENT

    Directory of Open Access Journals (Sweden)

    S. Robson

    2016-06-01

    Full Text Available University College London is currently developing a large-scale multi-camera system for dimensional control tasks in manufacturing, including part machining, assembly and tracking, as part of the Light Controlled Factory project funded by the UK Engineering and Physical Science Research Council. In parallel, as part of the EU LUMINAR project funded by the European Association of National Metrology Institutes, refraction models of the atmosphere in factory environments are being developed with the intent of modelling and eliminating the effects of temperature and other variations. The accuracy requirements for both projects are extremely demanding, so accordingly improvements in the modelling of both camera imaging and the measurement environment are essential. At the junction of these two projects lies close range camera calibration. The accurate and reliable calibration of cameras across a realistic range of atmospheric conditions in the factory environment is vital in order to eliminate systematic errors. This paper demonstrates the challenge of experimentally isolating environmental effects at the level of a few tens of microns. Longer lines of sight promote the use and calibration of a near perfect perspective projection from a Kern 75mm lens with maximum radial distortion of the order of 0.5m. Coordination of a reference target array, representing a manufactured part, is achieved to better than 0.1mm at a standoff of 8m. More widely, results contribute to better sensor understanding, improved mathematical modelling of factory environments and more reliable coordination of targets to 0.1mm and better over large volumes.

  5. Close Range Calibration of Long Focal Length Lenses in a Changing Environment

    Science.gov (United States)

    Robson, Stuart; MacDonald, Lindsay; Kyle, Stephen; Shortis, Mark R.

    2016-06-01

    University College London is currently developing a large-scale multi-camera system for dimensional control tasks in manufacturing, including part machining, assembly and tracking, as part of the Light Controlled Factory project funded by the UK Engineering and Physical Science Research Council. In parallel, as part of the EU LUMINAR project funded by the European Association of National Metrology Institutes, refraction models of the atmosphere in factory environments are being developed with the intent of modelling and eliminating the effects of temperature and other variations. The accuracy requirements for both projects are extremely demanding, so accordingly improvements in the modelling of both camera imaging and the measurement environment are essential. At the junction of these two projects lies close range camera calibration. The accurate and reliable calibration of cameras across a realistic range of atmospheric conditions in the factory environment is vital in order to eliminate systematic errors. This paper demonstrates the challenge of experimentally isolating environmental effects at the level of a few tens of microns. Longer lines of sight promote the use and calibration of a near perfect perspective projection from a Kern 75mm lens with maximum radial distortion of the order of 0.5m. Coordination of a reference target array, representing a manufactured part, is achieved to better than 0.1mm at a standoff of 8m. More widely, results contribute to better sensor understanding, improved mathematical modelling of factory environments and more reliable coordination of targets to 0.1mm and better over large volumes.

  6. The close environment of 24 micron galaxies at 0.6

    CERN Document Server

    Caputi, K I; Bolzonella, M; Lilly, S J; Zamorani, G; Aussel, H; Sanders, D; Bardelli, S; Bongiorno, A; Contini, T; Coppa, G; Cucciati, O; De la Torre, S; de Ravel, L; Franzetti, P; Frayer, D; Garilli, B; Iovino, A; Kampczyk, P; Kneib, J -P; Knobel, C; Lamareille, F; Le Borgne, J F; Le Brun, V; Le Fèvre, O; Le Floc'h, E; Leauthaud, A; Maier, C; Mainieri, V; Mignoli, M; Pellò, R; Peng, Y; Pérez-Montero, E; Ricciardelli, E; Salvato, M; Scodeggio, M; Scoville, N; Silverman, Joseph; Surace, J; Tanaka, M; Tasca, L; Tresse, L; Vergani, D; Zucca, E; Abbas, U; Bottini, D; Capak, P; Cappi, A; Carollo, C M; Cassata, P; Cimatti, A; Fumana, M; Ilbert, O; Kartaltepe, J; MacCagni, D; Marinoni, C; McCracken, H; Memeo, P; Meneux, B; Oesch, P; Porciani, C; Pozzetti, L; Renzini, A; Scaramella, R; Scarlata, C

    2008-01-01

    We investigate the close environment of 203 Spitzer 24 micron-selected sources at 0.61.4. We find that LIRGs at 0.61.4 within 1 Mpc and +/- 500 km/s). The contrast between the activities of the close environments of LIRGs and ULIRGs appears especially enhanced in the COSMOS field density peak at z~0.67, because LIRGs on this peak have a larger fraction of passive neighbours, while ULIRGs have as active close environments as those outside the large-scale structure. The differential environmental activity is related to the differences in the distributions of stellar mass ratios between LIRGs/ULIRGs and their close neighbours, as well as in the general local density fields. At 0.8environment densities of ULIRGs and other similarly massive galaxies, in spite of the differential activities. We discuss a possible scenario to explain these findings.

  7. The photodissociation of CO in circumstellar envelopes

    Science.gov (United States)

    Mamon, G. A.; Glassgold, A. E.; Huggins, P. J.

    1988-01-01

    The CO photodissociation rate for the unshielded ISM is calculated using recent laboratory results which confirm that photodissociation occurs by way of line absorption. A value of 2.0 x 10 to the -10th/s, an order of magnitude higher than the rate used in the past, is obtained. The new rate and a treatment of the radiative transfer and shielding are used to develop a theory for the CO abundance in the circumstellar envelopes of cool, evolved stars, and results are presented on the spatial variation of CO, C, and C(+). It is shown that these distributions play important roles in determining the observational properties of circumstellar envelopes.

  8. Dynamics of Circumstellar Disks. III. The Case of GG Tau A

    Science.gov (United States)

    Nelson, Andrew F.; Marzari, F.

    2016-08-01

    occurs at a steady rate of a few ×10-8 M ⊙ yr-1, with the net result that, without replenishment, the disk lifetimes would be shorter than ˜104 yr. Our simulations show that only wide orbit configurations are able to retain circumstellar disks, by virtue of accretion driven from the robust material streams generated in wide configurations, which are very weak in close configurations. In wide, eccentric orbit configurations, accretion is episodic and occurs preferentially onto the secondary, with rates strongly peaked near the binary periapse. Based on our results, we conclude that the GG Tau A torus is strongly self gravitating and that a major contribution to its thermal energy input is the shock dissipation associated with spiral structures generated both by self gravitating disturbances and by the stirring action of the binary. We interpret the sharply defined features observed in the torus as manifestations of such spiral structures. We interpret the low density disk surrounding it as an excretion disk created by the outward mass flux generated by the spiral arms as they propagate outwards. Typical eccentricities calculated for the shape of the tori modeled in our simulations are large enough to account for the supposed ˜20° mutual inclination between the stellar orbit plane of GG Tau A and its surrounding torus through a degeneracy between the interpretation of inclination of the torus and its eccentricity. We therefore interpret the observations in favor of a coplanar system with an eccentric torus. Because accretion onto the disks occurs at rates sufficient to sustain them only in wide orbit configurations, we conclude that the gas currently resident in the circumstellar disks of the GG Tau A system has been accreted from the torus within the past few thousand years. Although circumstellar disks will persist over time spans long enough to permit planet formation, the overall environment remains unfavorable due to high temperatures and other conditions. Given

  9. Low redshift quasars in the SDSS Stripe 82. Host galaxy colors and close environment

    CERN Document Server

    Bettoni, D; Kotilainen, J K; Karhunen, K; Uslenghi, M

    2015-01-01

    We present a photometrical and morphological multicolor study of the properties of low redshift (z<0.3) quasar hosts based on a large and homogeneous dataset of quasars derived from the Sloan Digital Sky Survey (DR7). We used quasars that were imaged in the SDSS Stripe82 that is up to 2 mag deeper than standard Sloan images. This sample is part of a larger dataset of ~400 quasars at z<0.5 for which both the host galaxies and their galaxy environments were studied (Falomo et al. 2014,Karhunen et al. 2014). For 52 quasars we undertake a study of the color of the host galaxies and of their close environments in u,g,r,i and z bands. We are able to resolve almost all the quasars in the sample in the filters g,r,i and z and also in $u$ for about 50% of the targets. We found that the mean colors of the QSO host galaxy (g-i=0.82+-0.26; r-i=0.26+-0.16 and u-g=1.32+-0.25) are very similar to the values of a sample of inactive galaxies matched in terms of redshift and galaxy luminosity with the quasar sample. Ther...

  10. The detection of heavy metals in the circumstellar envelopes of post-AGB stars

    CERN Document Server

    Klochkova, V G

    2015-01-01

    A new type of peculiarity -- a splitting or asymmetry of strong absorption lines, is found in the optical spectra of selected post-AGB stars with C-rich circumstellar envelopes. The effect is maximal in BaII lines whose profile is split into two-three components. The particular components of the split absorption lines are shown to be formed in a structured circumstellar envelope, suggesting an efficient dredge-up of the heavy metals produced during the preceding evolution of this star into the envelope. We suspect that the splitting (or asymmetry) of the profiles of strongest absorptions with low excitation potential of the low level can be associated with the kinematic and chemical properties of the circumstellar environment and with type of its morphology.

  11. Isothermal Circumstellar Dust Shell Model for Teaching

    Science.gov (United States)

    Robinson, G.; Towers, I. N.; Jovanoski, Z.

    2009-01-01

    We introduce a model of radiative transfer in circumstellar dust shells. By assuming that the shell is both isothermal and its thickness is small compared to its radius, the model is simple enough for students to grasp and yet still provides a quantitative description of the relevant physical features. The isothermal model can be used in a…

  12. The composition of circumstellar and interstellar dust

    NARCIS (Netherlands)

    Tielens, AGGM; Woodward, CE; Biscay, MD; Shull, JM

    2001-01-01

    A large number of solid dust components have been identified through analysis of stardust recovered from meteorites, and analysis of IR observations of circumstellar shells and the interstellar medium. These include graphite, hydrogenated amorphous carbon, diamond, PAHs, silicon-, iron-, and titanin

  13. The composition of circumstellar and interstellar dust

    NARCIS (Netherlands)

    Tielens, AGGM; Woodward, CE; Biscay, MD; Shull, JM

    2001-01-01

    A large number of solid dust components have been identified through analysis of stardust recovered from meteorites, and analysis of IR observations of circumstellar shells and the interstellar medium. These include graphite, hydrogenated amorphous carbon, diamond, PAHs, silicon-, iron-, and titanin

  14. The first Infrared study of the close environment of a long Gamma-Ray Burst

    CERN Document Server

    Floc'h, E Le; Gordon, K; Forrest, W J; Brandl, B; Schaerer, D; Dessauges-Zavadsky, M; Armus, L

    2011-01-01

    We present a characterization of the close environment of GRB980425 based on 5-160mic spectro-imaging obtained with Spitzer. The Gamma-Ray Burst GRB980425 occurred in a nearby (z=0.0085) SBc-type dwarf galaxy, at a projected distance of 900pc from an HII region with strong signatures of Wolf-Rayet (WR) stars. While this "WR region" produces less than 5% of the B-band emission of the host, we find that it is responsible for 45+/-10% of the total infrared luminosity, with a maximum contribution reaching 75% at 25-30mic. This atypical property is rarely observed among morphologically-relaxed dwarves, suggesting a strong causal link with the GRB event. The luminosity of the WR region (L_8-1000mic=4.6x10^8 Lsol), the peak of its spectral energy distribution at <~100mic and the presence of highly-ionized emission lines (e.g., [NeIII]) also reveal extremely young (<5Myr) star-forming activity, with a typical time-scale of only 47Myr to double the stellar mass already built. Finally, the mid-IR over B-band lumi...

  15. Laboratory Studies Of Circumstellar Carbonaceous Grain Formation

    Science.gov (United States)

    Contreras, Cesar; Sciamma-O'Brien, Ella; Salama, Farid

    2014-06-01

    The study of the formation processes of dust is essential to understand the budget of extraterrestrial organic molecules. Although dust with all its components plays an important role in the evolution of interstellar (IS) chemistry and in the formation of organic molecules, little is known on the formation processes of carbonaceous dust. We report the progress that was recently achieved in this domain using NASA Ames’ COSmIC facility (Contreras & Salama 2013, ApJS, 208, 6). PAHs are important chemical building blocks of IS dust. They are detected in IDPs and in meteoritic samples. Additionally, observational, laboratory, and theoretical studies have shown that PAHs are an important, ubiquitous component of the ISM. The formation of PAHs from smaller molecules has not been extensively studied. Therefore, we have performed laboratory experiments to study the dynamic processes of carbon grain formation, starting from the smallest hydrocarbon molecules into the formation of larger PAH and further into nanograins. Studies of IS dust analogs formed from a variety of PAH and hydrocarbon precursors as well as species that include the atoms O, N, and S, have recently been performed in our laboratory using the COSmIC facility to provide conditions that simulate IS and circumstellar environments. The species formed in the COSmiC chamber through a pulsed discharge nozzle plasma source are detected and characterized with a cavity ringdown spectrometer coupled to a time-of-flight mass spectrometer, thus providing both spectroscopic and ion mass information in-situ. Analysis of solid soot particles was also conducted using scanning electron microscopy at the UCSC/NASA Ames’ MACS facility. The SEM analysis of the deposition of soot from methane and acetylene precursors seeded in argon plasmas provide examples on the types of nanoparticles and micrograins that are produced in these gas mixtures under our experimental conditions. From these measurements, we derive information on

  16. Discovery of a Circumstellar Disk in the Lagoon Nebula

    Science.gov (United States)

    1997-04-01

    Circumstellar disks of gas and dust play a crucial role in the formation of stars and planets. Until now, high-resolution images of such disks around young stars within the Orion Nebula obtained with the Hubble Space Telescope (HST) constituted the most direct proof of their existence. Now, another circumstellar disk has been detected around a star in the Lagoon Nebula - also known as Messier 8 (M8) , a giant complex of interstellar gas and dust with many young stars in the southern constellation of Sagittarius and four times more distant than the Orion Nebula. The observations were carried out by an international team of scientists led by Bringfried Stecklum (Thüringer Landessternwarte, Tautenburg, Germany) [1] who used telescopes located at the ESO La Silla observatory and also observations from the HST archive. These new results are paving the road towards exciting research programmes on star formation which will become possible with the ESO Very Large Telescope. The harsh environment of circumstellar disks The existence of circumstellar disks has been inferred from indirect measurements of young stellar objects, such as the spectral energy distribution, the analysis of the profiles of individual spectral lines and measurements of the polarisation of the emitted light [2]. Impressive images of such disks in the Orion Nebula, known as proplyds (PROto-PLanetarY DiskS), have been obtained by the HST during the recent years. They have confirmed the interpretation of previous ground-based emission-line observations and mapping by radio telescopes. Moreover, they demonstrated that those disks which are located close to hot and massive stars are subject to heating caused by the intense radiation from these stars. Subsequently, the disks evaporate releasing neutral gas which streams off. During this process, shock fronts (regions with increased density) with tails of ionised gas result at a certain distance between the disk and the hot star. These objects appear on

  17. Circumstellar Debris and Pollution at White Dwarf Stars

    CERN Document Server

    Farihi, J

    2016-01-01

    Circumstellar disks of planetary debris are now known or suspected to closely orbit hundreds of white dwarf stars. To date, both data and theory support disks that are entirely contained within the preceding giant stellar radii, and hence must have been produced during the white dwarf phase. This picture is strengthened by the signature of material falling onto the pristine stellar surfaces; disks are always detected together with atmospheric heavy elements. The physical link between this debris and the white dwarf host abundances enables unique insight into the bulk chemistry of extrasolar planetary systems via their remnants. This review summarizes the body of evidence supporting dynamically active planetary systems at a large fraction of all white dwarfs, the remnants of first generation, main-sequence planetary systems, and hence provide insight into initial conditions as well as long-term dynamics and evolution.

  18. Six White Dwarfs with Circumstellar Silicates

    CERN Document Server

    Jura, M; Zuckerman, B

    2008-01-01

    Spitzer Space Telescope spectra reveal 10 micron silicate emission from circumstellar dust orbiting six externally-polluted white dwarfs. Micron-size glasses with an olivine stoichiometry can account for the distinctively broad wings that extend to 12 microns; these particles likely are produced by tidal-disruption of asteroids. The absence of infrared PAH features is consistent with a scenario where extrasolar rocky planets are assembled from carbon-poor solids.

  19. A role of Bradyrhizobium elkanii and closely related strains in the degradation of methoxychlor in soil and surface water environments.

    Science.gov (United States)

    Satsuma, Koji; Masuda, Minoru; Sato, Kiyoshi

    2013-01-01

    We have reported that a leguminous bacterial strain, Bradyrhizobium sp. strain 17-4, isolated from river sediment, phylogenetically very close to Bradyrhizobium elkanii, degraded methoxychlor through O-demethylation and oxidative dechlorination. In the present investigation, we found that B. elkanii (USDA94), a standard species deposited in the Culture Collection, degraded methoxychlor. Furthermore, Bradyrhizobium sp. strain 4-1, also very close to B. elkanii, isolated from Japanese paddy field soil, degraded methoxychlor. These B. elkanii and closely related strains degraded methoxychlor through almost identical metabolic pathways, and cleaved the phenyl ring and mineralized. In contrast, another representative Bradyrhizobium species, B. japonicum (USDA110), did not degrade methoxychlor at all. Based on these findings, B. elkanii and closely related strains are likely to play an important role not only in providing the readily biodegradable substrates but also in completely degrading (mineralizing) methoxychlor by themselves in the soil and surface water environment.

  20. Kinematic Dynamo In Turbulent Circumstellar Disks

    Science.gov (United States)

    Stepinski, T.

    1993-01-01

    Many circumstellar disks associated with objects ranging from protoplanetary nebulae, to accretion disks around compact stars allow for the generation of magnetic fields by an (alpha)omega dynamo. We have applied kinematic dynamo formalism to geometrically thin accretion disks. We calculate, in the framework of an adiabatic approximation, the normal mode solutions for dynamos operating in disks around compact stars. We then describe the criteria for a viable dynamo in protoplanetary nebulae, and discuss the particular features that make accretion disk dynamos different from planetary, stellar, and galactic dynamos.

  1. Could gastrointestinal disorders differ in two close but divergent social environments?

    Directory of Open Access Journals (Sweden)

    Grodzinsky Ewa

    2012-02-01

    Full Text Available Abstract Background Many public health problems in modern society affect the gastrointestinal area. Knowledge of the disease occurrence in populations is better understood if viewed in a psychosocial context including indicators of the social environment where people spend their lives. The general aim of this study was to estimate the occurrence in the population and between sexes of common gastrointestinal conditions in two neighborhood cities representing two different social environments defined as a "white-collar" and a "blue-collar" city. Methods We conducted a retrospective register study using data of diagnosed gastrointestinal disorders (cumulative incidence rates derived from an administrative health care register based on medical records assigned by the physicians at hospitals and primary care. Results Functional gastrointestinal diseases and peptic ulcers were more frequent in the white-collar city, while diagnoses in the gallbladder area were significantly more frequent in the blue-collar city. Functional dyspepsia, irritable bowel syndrome, and unspecified functional bowel diseases, and celiac disease, were more frequent among women while esophageal reflux, peptic ulcers, gastric and rectal cancers were more frequent among men regardless of social environment. Conclusions Knowledge of the occurrence of gastrointestinal problems in populations is better understood if viewed in a context were the social environment is included. Indicators of the social environment should therefore also be considered in future studies of the occurrence of gastrointestinal problems.

  2. The Circumstellar Environment of Evolved Stars as Revealed by Studies of Circumstellar Water Masers

    Science.gov (United States)

    Marvel, K.

    1997-11-01

    This dissertation presents the results of a multi-epoch very long baseline interferometric (VLBI) study of water masers located in the extended atmospheres of seven evolved stars. The research was performed using the Very Long Baseline Array and Very Large Array of the National Radio Astronomy Observatory. Water masers are found to exist in the atmospheres of evolved, oxygen-rich stars where a population inversion of the rotational transition at 22 GHz can be maintained by collisional pumping. The masers are identified as individual pockets or filaments of gas, which have good velocity coherence and may be imaged using radio interferometry. Stellar winds are initiated in these sources by dust formation and acceleration of the gas through momentum coupling. The typical wind speeds in the region of the water masers are 10 to 20 \\kms. The water masers in several evolved stars (VY CMa, VX Sgr, S Per, U Her, IK Tau, RX Boo and NML Cyg) have been observed at three epochs and exhibit proper motions consistent with the assumed source distances and the measured outflow velocity in the water maser region. Estimates of the distance to the sources using statistical approximation are in agreement with the currently accepted distances to the stars. The following stars had reliable distances determined using proper motion data: S Per (2.3 +/- 0.5 kpc), VY CMa (1.4 +/- 0.2 kpc), VX Sgr (1.4 +/- 0.3 kpc). An upper limit for the distance of NML Cyg was obtained ( 3.5 kpc). The remaining stars had too few maser detections (RX BOO, IK Tau) or were not strong enough at all epochs (U Her) to self-calibrate using the VLBA. A detailed kinematic model was used to describe the flow motions of the gas in the maser region. The regions are found to be complex and not well modeled by uniform radial outflow, radial outflow with rotation, or radial outflow with acceleration. The reasons for this are explored and include the probable presence of anisotropic velocity fields induced through non-uniform dust formation near the star. (SECTION: Dissertation Summaries) [1]The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

  3. Sub-Keplerian accretion onto circumstellar disks

    CERN Document Server

    Visser, R

    2010-01-01

    Models of the formation, evolution and photoevaporation of circumstellar disks are an essential ingredient in many theories of the formation of planetary systems. The ratio of disk mass over stellar mass in the circumstellar phase of a disk is largely determined by the angular momentum of the original cloud core from which the system was formed. While full 3D or 2D axisymmetric hydrodynamical models of accretion onto the disk automatically treat all aspects of angular momentum, this is not so trivial for 1D and semi-2D viscous disk models. Since 1D and semi-2D disk models are still very useful for long-term evolutionary modelling of disks with relatively little numerical effort, we investigate how the 2D nature of accretion affects the formation and evolution of the disk in such models. A proper treatment of this problem requires a correction for the sub-Keplerian velocity at which accretion takes place. We develop an update of our semi-2D time-dependent disk evolution model to properly treat the effects of s...

  4. Passive acoustic detection of closed-circuit underwater breathing apparatus in an operational port environment

    NARCIS (Netherlands)

    Fillinger, L.; Hunter, A.J.; Zampolli, M.; Clarijs, M.C.

    2012-01-01

    Divers constitute a potential threat to waterside infrastructures. Active diver detection sonars are available commercially but present some shortcomings, particularly in highly reverberant environments. This has led to research on passive sonar for diver detection. Passive detection of open-circuit

  5. Close-range photogrammetry enables documentation of environment-induced deformation of architectural heritage

    OpenAIRE

    Suziedelyte-Visockiene, J; Bagdziunaite, R; Malys, N.; Maliene, V

    2015-01-01

    Deformation, damage and permanent loss of heritage assets due to various physical and environmental factors has always been a major problem. As the availability of funds for conservation and restoration is limited, the digital documentation of heritage objects and monitoring of environment-induced deformations are increasingly important for cultural heritage preservation. Our study elucidates developments in the digital image capturing and processing for recording architectural heritage objec...

  6. ON THE LIKELIHOOD OF PLANET FORMATION IN CLOSE BINARIES

    Energy Technology Data Exchange (ETDEWEB)

    Jang-Condell, Hannah, E-mail: hjangcon@uwyo.edu [Department of Physics and Astronomy, University of Wyoming, 1000 East University, Department 3905, Laramie, WY 82071 (United States)

    2015-02-01

    To date, several exoplanets have been discovered orbiting stars with close binary companions (a ≲ 30 AU). The fact that planets can form in these dynamically challenging environments implies that planet formation must be a robust process. The initial protoplanetary disks in these systems from which planets must form should be tidally truncated to radii of a few AU, which indicates that the efficiency of planet formation must be high. Here, we examine the truncation of circumstellar protoplanetary disks in close binary systems, studying how the likelihood of planet formation is affected over a range of disk parameters. If the semimajor axis of the binary is too small or its eccentricity is too high, the disk will have too little mass for planet formation to occur. However, we find that the stars in the binary systems known to have planets should have once hosted circumstellar disks that were capable of supporting planet formation despite their truncation. We present a way to characterize the feasibility of planet formation based on binary orbital parameters such as stellar mass, companion mass, eccentricity, and semimajor axis. Using this measure, we can quantify the robustness of planet formation in close binaries and better understand the overall efficiency of planet formation in general.

  7. Wind Dynamics and Circumstellar Extinction Variations in the T Tauri Star RY Tau

    CERN Document Server

    Babina, Elena V; Petrov, Peter P

    2016-01-01

    The wind interaction with the dusty environment of the classical T Tauri star RY Tau has been investigated. During two seasons of 2013-2015 we carried out a spectroscopic and photometric (BVR) monitoring of the star. A correlation between the stellar brightness and the radial velocity of the wind determined from the H-alpha and Na D line profiles has been found for the first time. The irregular stellar brightness variations are shown to be caused by extinction in a dusty disk wind at a distance of about 0.2 AU from the star. We suppose, that variations of the circumstellar extinction results from cyclic rearrangements of the stellar magnetosphere and coronal mass ejections, which affect the dusty disk wind near the inner boundary of the circumstellar disk.

  8. The circumstellar material around SN IIn 1997eg Another detection of Very Narrow P Cygni profile

    CERN Document Server

    Salamanca, I M; Tenorio-Tagle, G

    2002-01-01

    We report the detection of a very narrow P Cygni profile on top of the broad emission Ha and Hb lines of the Type IIn Supernova 1997eg. A similar feature has been detected in SN 1997ab (Salamanca et al. 1998), SN 1998S (Meikle & Geballe 1998, Fassia et al. 2001) and SN 1995G (Filippenko & Schlegel 1995). The detection of the narrow P Cygni profile indicates the existence of a dense circumstellar material (CSM) into which the ejecta of the supernova is expanding. From the analysis of the spectra of SN 1997eg we deduce (a) that such CSM is very dense (n ~ 5x10^7 cm^-3), (b) that has a low expanding velocity of about 160 \\kms. The origin of such dense CSM can be either a very dense progenitor wind (dotM ~ 10^-2 solar masses per year) or a circumstellar shell product of the progenitor wind expanding into a high pressure environment.

  9. From Protoplanetary Disks to Extrasolar Planets: Understanding the Life Cycle of Circumstellar Gas with Ultraviolet Spectroscopy

    CERN Document Server

    France, Kevin; Ardila, David R; Bergin, Edwin A; Brown, Alexander; Burgh, Eric B; Calvet, Nuria; Chiang, Eugene; Cook, Timothy A; Désert, Jean-Michel; Ebbets, Dennis; Froning, Cynthia S; Green, James C; Hillenbrand, Lynne A; Johns-Krull, Christopher M; Koskinen, Tommi T; Linsky, Jeffrey L; Redfield, Seth; Roberge, Aki; Schindhelm, Eric R; Scowen, Paul A; Stapelfeldt, Karl R; Tumlinson, Jason

    2012-01-01

    Few scientific discoveries have captured the public imagination like the explosion of exoplanetary science during the past two decades. This work has fundamentally changed our picture of Earth's place in the Universe and led NASA to make significant investments towards understanding the demographics of exoplanetary systems and the conditions that lead to their formation. The story of the formation and evolution of exoplanetary systems is essentially the story of the circumstellar gas and dust that are initially present in the protostellar environment; in order to understand the variety of planetary systems observed, we need to understand the life cycle of circumstellar gas from its initial conditions in protoplanetary disks to its endpoint as planets and their atmospheres. In this white paper response to NASA's Request for Information "Science Objectives and Requirements for the Next NASA UV/Visible Astrophysics Mission Concepts (NNH12ZDA008L)", we describe scientific programs that would use the unique capabi...

  10. Hydrogen sulfide in a circumstellar envelope

    Science.gov (United States)

    Ukita, N.; Morris, M.

    1983-01-01

    A search for hydrogen sulfide in the cool circumstellar envelopes of 25 stars was made using the 1(10)-1(01) rotational line at 1.8 mm. It was detected in the bipolar nebula/OH maser OH231.8+4.2, an object having a high rate of mass loss. An approximate analysis indicates that 1/60 of the sulfur in this outflowing envelope is in the form of H2S, a fraction which may be similar to that in the atmosphere of the central star. In addition, the shape of the observed line profile is discussed in terms of a possible variation of the outflow velocity with latitude above the system's equatorial plane.

  11. Composite grains: Application to circumstellar dust

    Directory of Open Access Journals (Sweden)

    D. B. Vaidya

    2011-09-01

    Full Text Available Using the discrete dipole approximation (DDA we calculate the absorption efficiency of the composite grain, made up of a host silicate spheroid and inclusions of graphite, in the spectral region 5.0-25.0μm. We study the absorption as a function of the voulume fraction of the inclusions. In particular, we study the variation in the 10.0μm and 18.0μm emission features with the volume fraction of the inclusions. Using the extinction efficiencies, of the composite grains we calculate the infrared fluxes at several dust temperatures and compare the model curves with the observed infrared emission curves (IRAS-LRS, obtained for circumstellar dust shells around oxygen rich M-type stars.

  12. Dust Stratification in Young Circumstellar Disks

    CERN Document Server

    Rettig, T; Simon, T; Gibb, E; Balsara, D S; Tilley, D A; Kulesa, C; Simon, Theodore

    2006-01-01

    We present high-resolution infrared spectra of four YSOs (T Tau N, T Tau S, RNO 91, and HL Tau). The spectra exhibit narrow absorption lines of 12CO, 13CO, and C18O as well as broad emission lines of gas phase12CO. The narrow absorption lines of CO are shown to originate from the colder circumstellar gas. We find that the line of sight gas column densities resulting from the CO absorption lines are much higher than expected for the measured extinction for each source and suggest the gas to dust ratio is measuring the dust settling and/or grain coagulation in these extended disks. We provide a model of turbulence, dust settling and grain growth to explain the results. The techniques presented here allow us to provide some observationally-motivated bounds on accretion disk alpha in protostellar systems.

  13. Rapid planetesimal formation in turbulent circumstellar discs

    CERN Document Server

    Johansen, Anders; Mac Low, Mordecai-Mark; Klahr, Hubert; Henning, Thomas; Youdin, Andrew

    2007-01-01

    The initial stages of planet formation in circumstellar gas discs proceed via dust grains that collide and build up larger and larger bodies (Safronov 1969). How this process continues from metre-sized boulders to kilometre-scale planetesimals is a major unsolved problem (Dominik et al. 2007): boulders stick together poorly (Benz 2000), and spiral into the protostar in a few hundred orbits due to a head wind from the slower rotating gas (Weidenschilling 1977). Gravitational collapse of the solid component has been suggested to overcome this barrier (Safronov 1969, Goldreich & Ward 1973, Youdin & Shu 2002). Even low levels of turbulence, however, inhibit sedimentation of solids to a sufficiently dense midplane layer (Weidenschilling & Cuzzi 1993, Dominik et al. 2007), but turbulence must be present to explain observed gas accretion in protostellar discs (Hartmann 1998). Here we report the discovery of efficient gravitational collapse of boulders in locally overdense regions in the midplane. The bou...

  14. The infrared spectral features of circumstellar envelope of evolved low-and intermediate-mass stars

    Institute of Scientific and Technical Information of China (English)

    ZHANG Ke; JIANG BiWei

    2008-01-01

    The circumstellar envelope of evolved stars of low-and intermediate-mass is an important site for dust formation. In comparison with the interstellar medium, they have more types of organics and different types of inorganics. Various infrared features in the circumstellar envelope can reveal the composition and abundance of dust, as well as the chemical and physical conditions of the circumstellar shell. Infrared features and their carriers are different in the C-rich or O-rich environment, and the mixed-environment where the C-rich and O-rich circumstellar materials co-exist. The C-rich sources exhibit a series of spectral features which are attrib-uted to organic molecules. They also show two prominent features at 21 μm and 30 μm which emit a large portion of infrared radiation. The O-rich sources exhibit the strong 9.7 μm and 18 μm features attributed to the Si-O bending and O-Si-O stretching modes of amorphous silicate dust. With the ISO/SWS spectrometer, about 50 narrow bands are identified with the crystalline silicate grains, mainly forsterite and enstatite. In addition, a series of features, at 13 μm, 16.8 μm, 19.5 μm and 31.8 μm, appearing to be correlated with each other, are attributed to oxides. Some objects simultaneously show the C-rich and O-rich features, e.g. some C-rich sources have silicate features. There is no well-accepted interpretation for such mixed appearance, though a binary model is suggested.

  15. The infrared spectral features of circumstellar envelope of evolved low- and intermediate-mass stars

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The circumstellar envelope of evolved stars of low- and intermediate-mass is an important site for dust formation. In comparison with the interstellar medium, they have more types of organics and different types of inorganics. Various infrared features in the circumstellar envelope can reveal the composition and abundance of dust, as well as the chemical and physical conditions of the circumstellar shell. Infrared features and their carriers are different in the C-rich or O-rich environment, and the mixed-environment where the C-rich and O-rich circumstellar materials co-exist. The C-rich sources exhibit a series of spectral features which are attrib- uted to organic molecules. They also show two prominent features at 21 μm and 30 μm which emit a large portion of infrared radiation. The O-rich sources exhibit the strong 9.7 μm and 18 μm features attributed to the Si-O bending and O-Si-O stretching modes of amorphous silicate dust. With the ISO/SWS spectrometer, about 50 narrow bands are identified with the crystalline silicate grains, mainly forsterite and enstatite. In addition, a series of features, at 13 μm, 16.8 μm, 19.5 μm and 31.8 μm, appearing to be correlated with each other, are attributed to oxides. Some objects simultaneously show the C-rich and O-rich features, e.g. some C-rich sources have silicate features. There is no well-accepted interpretation for such mixed appearance, though a binary model is suggested.

  16. Indoors forensic entomology: colonization of human remains in closed environments by specific species of sarcosaprophagous flies.

    Science.gov (United States)

    Pohjoismäki, Jaakko L O; Karhunen, Pekka J; Goebeler, Sirkka; Saukko, Pekka; Sääksjärvi, Ilari E

    2010-06-15

    Fly species that are commonly recovered on human corpses concealed in houses or other dwellings are often dependent on human created environments and might have special features in their biology that allow them to colonize indoor cadavers. In this study we describe nine typical cases involving forensically relevant flies on human remains found indoors in southern Finland. Eggs, larvae and puparia were reared to adult stage and determined to species. Of the five species found the most common were Lucilia sericata Meigen, Calliphora vicina Robineau-Desvoidy and Protophormia terraenovae Robineau-Desvoidy. The flesh fly Sarcophaga caerulescens Zetterstedt is reported for the first time to colonize human cadavers inside houses and a COI gene sequence based DNA barcode is provided for it to help facilitate identification in the future. Fly biology, colonization speed and the significance of indoors forensic entomological evidence are discussed.

  17. Close to me: the effect of asymmetrical environments on spatial attention.

    Science.gov (United States)

    Nicholls, Michael E R; Roden, Sally; Thomas, Nicole A; Loetscher, Tobias; Spence, Charles J; Forte, Jason D

    2014-01-01

    Attention can be captured by distractors and can affect performance. To examine whether asymmetrical distractors, such as a wall, affect spatial attention, Experiment 1 required participants (n = 20) to determine the relative length of pre-bisected lines when a temporary barrier was placed close to the left or right sides of the display. Post-hoc tests showed that attention was drawn towards left, but not right, walls. Experiment 2 (n = 18) sought to increase this effect using a solid brick wall rather than a temporary barrier. Instead of strengthening the result, no effect of barrier was observed. A non-effect was also observed in Experiment 3 (n = 18) when participants moved a cursor to the line's middle. Finally, Experiment 4 (n = 26) showed that asymmetrical barriers had no effect on visual search. While the data showed some evidence that attention is distracted by walls placed to the left, this effect is weak and task-specific. The ability to monitor critical information on displays can be affected by asymmetrical distractors. In many workplaces, a display may be placed alongside a wall. This study explored whether a wall placed to the left/right affects spatial attention. A weak, task-specific, attraction effect was observed for walls on the left.

  18. Growth and gas exchange by lettuce stands in a closed, controlled environment.

    Science.gov (United States)

    Wheeler, R M; Mackowiak, C L; Sager, J C; Yorio, N C; Knott, W M; Berry, W L

    1994-05-01

    Two studies were conducted in which 'Waldmann's Green' lettuce (Lactuca sativa L.) was grown hydroponically from seed to harvest in a large (20-m2), atmospherically closed growth chamber for the National Aeronautics and Space Administration's controlled ecological life support system (CELSS) program. The first study used metal-halide (MH) lamps [280 micromoles m-2 s-1 photosynthetic photon flux (PPF)], whereas the second used high-pressure sodium (HPS) lamps (293 micromoles m-2 s-1). Both studies used a 16-hour photoperiod, a constant air temperature (22 to 23C), and 1000 micromoles mol-1 CO2 during the light period. In each study, canopy photosynthesis and evapotranspiration (ET) rates were highly correlated to canopy cover, with absolute rates peaking at harvest (28 days after planting ) at 17 micromoles CO2/m2 per sec and 4 liters m-2 day-1, respectively. When normalized for actual canopy cover, photosynthesis and ET rates per unit canopy area decreased with age (between 15 and 28 days after planting). Canopy cover increased earlier during the study with HPS lamps, and final shoot yields averaged 183 g fresh mass (FM)/plant 8.8 g dry mass (DM)/plant. Shoot yields in the first study with MH lamps averaged 129 g FM/plant and 6.8 g DM/plant. Analysis of leaf tissue showed that ash levels from both studies averaged 22% and K levels ranged from 15% to 17% of tissue DM. Results suggest that lettuce should be easily adaptable to a CELSS with moderate lighting and that plant spacing or transplant schemes are needed to maximize canopy light interception and sustained efficient CO2 removal and water production.

  19. Sulphur molecules in the circumstellar envelopes of M-type AGB stars

    CERN Document Server

    Danilovich, Taissa; Black, J H; Olofsson, H; Justtanont, K

    2016-01-01

    The sulphur compounds SO and SO$_2$ have not been widely studied in the circumstellar envelopes of asymptotic giant branch (AGB) stars. By presenting and modelling a large number of SO and SO$_2$ lines in the low mass-loss rate M-type AGB star R Dor, and modelling the available lines of those molecules in a further four M-type AGB stars, we aim to determine their circumstellar abundances and distributions. We use a detailed radiative transfer analysis based on the accelerated lambda iteration method to model circumstellar SO and SO$_2$ line emission and molecular data files for both SO and SO$_2$ that are more extensive than those previously available. Using 17 SO lines and 98 SO2 lines to constrain our models for R Dor, we find an SO abundance of 6.7x10$^{-6}$ and an SO$_2$ abundance of 5x10$^{-6}$ with both species having high abundances close to the star. We also modelled $^{34}$SO and found an abundance of 3.1x10$^{-7}$, giving an $^{32}$SO/$^{34}$SO ratio of 21.6. We derive similar results for the circum...

  20. The magnetic field around late-type stars revealed by the circumstellar H2O masers

    CERN Document Server

    Vlemmings, W H T; Diamond, P J

    2005-01-01

    Through polarization observations, circumstellar masers are excellent probes of the magnetic field in the envelopes of late-type stars. Whereas observations of the polarization of the SiO masers close to the star and on the OH masers much further out were fairly commonplace, observations of the magnetic field strength in the intermediate density and temperature region where the 22 GHz water masers occur have only recently become possible. Here we present the analysis of the circular polarization, due to Zeeman splitting, of the water masers around the Mira variable stars U Her and U Ori and the supergiant VX Sgr. We present an upper limit of the field around U Her that is lower but consistent with previous measurements, reflecting possible changes in the circumstellar envelope. The field strengths around U Ori and VX Sgr are shown to be of the order of several Gauss. Moreover, we show for the first time that large scale magnetic fields permeate the circumstellar envelopes of an evolved star; the polarization ...

  1. Case series of mercury toxicity among children in a hot, closed environment.

    Science.gov (United States)

    Akyildiz, Basak Nur; Kondolot, Meda; Kurtoğlu, Selim; Konuşkan, Bahadir

    2012-03-01

    Mercury poisoning is much more prevalent in the general population than possibly many physicians realize. We present data on 26 pediatric cases with mercury intoxication from exposure to mercury by inhalation or skin contact as a result of a broken thermometer in a school laboratory. This is the largest pediatric series in Turkey. During a 3-month period, the study team observed the children for clinical symptoms, physical findings, and blood and mercury levels. Of all patients, 21 inhaled, 3 inhaled and touched the element, and 2 took the mercury home. Sixteen children were symptomatic at admission, although blood mercury levels in the symptomatic children were higher than those in asymptomatic children (P = 0.003). The urine mercury levels were not statistically different between the groups at the admission (P > 0.05). The exposure times were 3.5 and 2 hours for symptomatic and asymptomatic children, respectively (P = 0.003). The 2 children who took the mercury home had the highest blood mercury levels and the most prolonged exposure time. N-acetylcysteine and chelation treatments were started in 21 children who had symptoms of mercury intoxication and high mercury levels in their blood or urine. No adverse effects were observed during chelation therapy. Prompt removal of children from contaminated environments and proper decontamination or elimination of devices containing large amounts of mercury from schools are necessary to prevent serious complications caused by exposure to mercury.

  2. Automation of closed environments in space for human comfort and safety

    Science.gov (United States)

    1990-01-01

    The Environmental Control and Life Support System (ECLSS) for the Space Station Freedom and future colonization of the Moon and Mars presents new challenges for present technologies. Current plans call for a crew of 8 to live in a safe, shirt-sleeve environment for 90 days without ground support. Because of these requirements, all life support systems must be self-sufficient and reliable. The ECLSS is composed of six subsystems. The temperature and humidity control (THC) subsystem maintains the cabin temperature and humidity at a comfortable level. The atmosphere control and supply (ACS) subsystem insures proper cabin pressure and partial pressures of oxygen and nitrogen. To protect the space station from fire damage, the fire detection and suppression (FDS) subsystem provides fire sensing alarms and extinguishers. The waste management (WM) subsystem compacts solid wastes for return to Earth, and collects urine for water recovery. Because it is impractical, if not impossible, to supply the station with enough fresh air and water for the duration of the space station's extended mission, these elements are recycled. The atmosphere revitalization (AR) subsystem removes CO2 and other dangerous contaminants from the air. The water recovery and management (WRM) subsystem collects and filters condensate from the cabin to replenish potable water supplies, and processes urine and other waste waters to replenish hygiene water supplies. These subsystems are not fully automated at this time. Furthermore, the control of these subsystems is not presently integrated; they are largely independent of one another. A fully integrated and automated ECLSS would increase astronauts' productivity and contribute to their safety and comfort. The Kansas State University Advanced Design Team is in the process of researching and designing controls for the automation of the ECLSS for Space Station Freedom and beyond. The approach chosen to solve this problem is to divide the design into three

  3. Optical Signatures of Circumstellar Interaction in Type IIP Supernovae

    CERN Document Server

    Chugai, N N; Utrobin, V P; Chugai, Nikolai N.; Chevalier, Roger A.; Utrobin, Victor P.

    2007-01-01

    We propose new diagnostics for circumstellar interaction in Type IIP supernovae by the detection of high velocity (HV) absorption features in Halpha and He I 10830 A lines during the photospheric stage. To demonstrate the method, we compute the ionization and excitation of H and He in supernova ejecta taking into account time-dependent effects and X-ray irradiation. We find that the interaction with a typical red supergiant wind should result in the enhanced excitation of the outer layers of unshocked ejecta and the emergence of corresponding HV absorption, i.e. a depression in the blue absorption wing of Halpha and a pronounced absorption of He I 10830 A at a radial velocity of about -10,000 km/s. We identify HV absorption in Halpha and He I 10830 A lines of SN 1999em and in Halpha of SN 2004dj as being due to this effect. The derived mass loss rate is close to 10^{-6} Msun/yr for both supernovae, assuming a wind velocity 10 km/s. We argue that, in addition to the HV absorption formed in the unshocked ejecta...

  4. Numerical models for the circumstellar medium around Betelgeuse

    CERN Document Server

    Mackey, Jonathan; Neilson, Hilding R; Langer, Norbert; Meyer, Dominique M -A

    2013-01-01

    The nearby red supergiant (RSG) Betelgeuse has a complex circumstellar medium out to at least 0.5 parsecs from its surface, shaped by its mass-loss history within the past 0.1 Myr, its environment, and its motion through the interstellar medium (ISM). In principle its mass-loss history can be constrained by comparing hydrodynamic models with observations. Observations and numerical simulations indicate that Betelgeuse has a very young bow shock, hence the star may have only recently become a RSG. To test this possibility we calculated a stellar evolution model for a single star with properties consistent with Betelgeuse. We incorporated the resulting evolving stellar wind into 2D hydrodynamic simulations to model a runaway blue supergiant (BSG) undergoing the transition to a RSG near the end of its life. The collapsing BSG wind bubble induces a bow shock-shaped inner shell which at least superficially resembles Betelgeuse's bow shock, and has a similar mass. Surrounding this is the larger-scale retreating bow...

  5. A dynamical study of the circumstellar gas in UX Orionis

    CERN Document Server

    Mora, A; Eiroa, C; Grady, C A; De Winter, D; Davies, J K; Ferlet, R; Harris, A W; Montesinos, B; Oudmaijer, R D; Palacios, J; Quirrenbach, Andreas G; Rauer, H; Alberdi, A; Cameron, A; Deeg, H J; Garzón, F; Horne, K; Merin, B; Penny, A; Schneider, J; Solano, E; Tsapras, Y; Wesselius, P R

    2002-01-01

    We present the results of a high spectral resolution study of the circumstellar (CS) gas around the intermediate mass, pre-main sequence star UX Ori. The results are based on a set of 10 echelle spectra, monitoring the star on time scales of months, days and hours. A large number of transient blueshifted and redshifted absorption features are detected in the Balmer and in many metallic lines. A multigaussian fit is applied to determine for each transient absorption the velocity, v, dispersion velocity, Delta v, and the parameter R, which provides a measure of the absorption strength of the CS gas. The time evolution of those parameters is presented and discussed. A comparison of intensity ratios among the transient absorptions suggests a solar-like composition of the CS gas. This confirms previous results and excludes a very metal-rich environment as the cause of the transient features in UX Ori. The features can be grouped by their similar velocities into 24 groups, of which 17 are redshifted and 7 blueshift...

  6. Circumstellar Debris Disks: Diagnosing the Unseen Perturber

    CERN Document Server

    Nesvold, Erika R; Vican, Laura; Farr, Will M

    2016-01-01

    The first indication of the presence of a circumstellar debris disk is usually the detection of excess infrared emission from the population of small dust grains orbiting the star. This dust is short-lived, requiring continual replenishment, and indicating that the disk must be excited by an unseen perturber. Previous theoretical studies have demonstrated that an eccentric planet orbiting interior to the disk will stir the larger bodies in the belt and produce dust via interparticle collisions. However, motivated by recent observations, we explore another possible mechanism for heating a debris disk: a stellar-mass perturber orbiting exterior to and inclined to the disk and exciting the disk particles' eccentricities and inclinations via the Kozai-Lidov mechanism. We explore the consequences of an exterior perturber on the evolution of a debris disk using secular analysis and collisional N-body simulations. We demonstrate that a Kozai-Lidov excited disk can generate a dust disk via collisions and we compare t...

  7. An MCMC Circumstellar Disks Modeling Tool

    Science.gov (United States)

    Wolff, Schuyler; Perrin, Marshall D.; Mazoyer, Johan; Choquet, Elodie; Soummer, Remi; Ren, Bin; Pueyo, Laurent; Debes, John H.; Duchene, Gaspard; Pinte, Christophe; Menard, Francois

    2016-01-01

    We present an enhanced software framework for the Monte Carlo Markov Chain modeling of circumstellar disk observations, including spectral energy distributions and multi wavelength images from a variety of instruments (e.g. GPI, NICI, HST, WFIRST). The goal is to self-consistently and simultaneously fit a wide variety of observables in order to place constraints on the physical properties of a given disk, while also rigorously assessing the uncertainties in the derived properties. This modular code is designed to work with a collection of existing modeling tools, ranging from simple scripts to define the geometry for optically thin debris disks, to full radiative transfer modeling of complex grain structures in protoplanetary disks (using the MCFOST radiative transfer modeling code). The MCMC chain relies on direct chi squared comparison of model images/spectra to observations. We will include a discussion of how best to weight different observations in the modeling of a single disk and how to incorporate forward modeling from PCA PSF subtraction techniques. The code is open source, python, and available from github. Results for several disks at various evolutionary stages will be discussed.

  8. Circumstellar disks around Herbig Be stars

    CERN Document Server

    Alonso-Albi, T; Bachiller, R; Neri, R; Planesas, P; Testi, L; Berne, O; Joblin, C

    2008-01-01

    We have carried out a search for circumstellar disks around Herbig Be stars using the NRAO Very Large Array (VLA) and the IRAM Plateau de Bure (PdB) interferometers. In this Paper, we present our new VLA and PdBI data on the three objects MWC 297, Z CMa and LKHa 215. We have constructed the SED from near-IR to centimeter wavelengths by adding our millimeter and centimeter data to the available data at other wavelengths, mainly Spitzer images. The whole SED has been fitted using a disk+envelope model. In addition, we have compiled all the disk millimeter observations in the literature and made some statistics. We show that the disk mass is usually only a small percentage (less than 10%) of the mass of the whole envelope in HBe stars. Concerning the disks, there are large source to source variations. Two disks of our sample, R Mon and Z CMa, have similar sizes and masses to those found in T Tauri and Herbig Ae stars. The disks around MWC 1080 and MWC 297 are, however, smaller (rout<100 AU). We have not detec...

  9. USING PHOTOMETRY TO PROBE THE CIRCUMSTELLAR ENVIRONMENT OF {delta} SCORPII

    Energy Technology Data Exchange (ETDEWEB)

    Jones, C. E.; Wiegert, P. A.; Cyr, R. P.; Halonen, R. J. [Department of Physics and Astronomy, Western University, London, ON N6A 3K7 (Canada); Tycner, C. [Department of Physics, Central Michigan University, Mt. Pleasant, MI 48859 (United States); Henry, G. W.; Muterspaugh, M. W. [Center of Excellence in Information Systems, Tennessee State University, 3500 John A. Merritt Blvd., Box No 9501, Nashville, TN 37209 (United States)

    2013-05-15

    We acquired Johnson BV photometry of the binary Be disk system {delta} Scorpii during its 2009, 2010, 2011, and 2012 observing seasons and used it to probe the innermost regions of the disk. We found that several disk building events have occurred during this time, resulting in an overall brightening in the V band and reddening of the system. In addition to these long-term trends, we found cyclical variability in each observing season on timescales between 60 and 100 days. We were able to reproduce the changes in the magnitude and color of {delta} Sco using our theoretical models and found that variable mass-loss rates in the range 2.5-7.0 Multiplication-Sign 10{sup -9} M{sub Sun} yr{sup -1} over {approx}35 days can reproduce the observed increase in brightness.

  10. Plutonium, americium and radiocaesium in the marine environment close to the Vandellos I nuclear power plant before decommissioning

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Cabeza, J.A. E-mail: joanalbert.sanchez@uab.es; Molero, J

    2000-11-01

    The Vandellos nuclear power plant (NPP), releasing low-level radioactive liquid waste to the Mediterranean Sea, is the first to be decommissioned in Spain, after an incident which occurred in 1989. The presence, distribution and uptake of various artificial radionuclides (radiocaesium, plutonium and americium) in the environment close to the plant were studied in seawater, bottom sediments and biota, including Posidonia oceanica, fish, crustaceans and molluscs. Seawater, sediments and Posidonia oceanica showed enhanced levels in the close vicinity of the NPP, although the effect was restricted to its near environment. Maximum concentrations in seawater were 11.6{+-}0.5 Bq m{sup -3} and 16.9{+-}1.2 mBq m{sup -3} for {sup 137}Cs and {sup 239,240}Pu, respectively. When sediment concentrations were normalized to excess {sup 210}Pb, they showed both the short-distance transport of artificial radionuclides from the Vandellos plant and the long-distance transport of {sup 137}Cs from the Asco NPP. Posidonia oceanica showed the presence of various gamma-emitters attributed to the impact of the Chernobyl accident, on which the effect of the NPP was superimposed. Seawater, sediment and Posidonia oceanica collected near the plant also showed an enhancement of the plutonium isotopic ratio above the fallout value. The uptake of these radionuclides by marine organisms was detectable but limited. Pelagic fish showed relatively higher {sup 137}Cs concentrations and only in the case of demersal fish was the plutonium isotopic ratio increased. The reported levels constitute a set of baseline values against which the impact of the decommissioning operations of the Vandellos I NPP can be studied.

  11. MICROMETEOROLOGICAL ENVIRONMENTS AND BIODIVERSITY IN A CLOSED FOREST AND AT A TREE-FALL GAP IN CENTRAL AMAZONIA

    Directory of Open Access Journals (Sweden)

    Akio Tsuchiya

    2009-09-01

    Full Text Available Micrometeorological parameters were measured in a closed forest (CF and at a tree-fall gap (LG near Novo Aripuanã, AM, along the Madeira River in dry season (August to September 2003 and rainy season (March 2004, and were compared to the number of species per family and the number of seedlings obtained from forest inventory. The daily averages of net radiation (W/m2 between CF and LG were 9.5:168.0 during dry season and 3.6:125.9 during rainy season, and these averages were influenced by the difference in shortwave radiation between the sites (CFenvironments at gaps, were found, such as Pourouma, Parkia, Tachigalia, and Orbignya, meanwhile genera peculiar to closed forests (Protium, Chrysophyllum, Micropholis were also found.

  12. MICROMETEOROLOGICAL ENVIRONMENTS AND BIODIVERSITY IN A CLOSED FOREST AND AT A TREE-FALL GAP IN CENTRAL AMAZONIA

    Directory of Open Access Journals (Sweden)

    Akio Tsuchiya

    2008-01-01

    Full Text Available Micrometeorological parameters were measured in a closed forest (CF and at a tree-fall gap (LG near Novo Aripuanã, AM, along the Madeira River in dry season (August to September 2003 and rainy season (March 2004, and were compared to the number of species per family and the number of seedlings obtained from forest inventory. The daily averages of net radiation (W/m2 between CF and LG were 9.5:168.0 during dry season and 3.6:125.9 during rainy season, and these averages were influenced by the difference in shortwave radiation between the sites (CFenvironments at gaps, were found, such as Pourouma, Parkia, Tachigalia, and Orbignya, meanwhile genera peculiar to closed forests (Protium, Chrysophyllum, Micropholis were also found.

  13. Monte Carlo simulations of the electric field close to the body in realistic environments for application in personal radiofrequency dosimetry.

    Science.gov (United States)

    Iskra, S; McKenzie, R; Cosic, I

    2011-11-01

    Personal dosemeters can play an important role in epidemiological studies and in radiofrequency safety programmes. In this study, a Monte Carlo approach is used in conjunction with the finite difference time domain method to obtain distributions of the electric field strength close to a human body model in simulated realistic environments. The field is a proxy for the response of an ideal body-worn electric field dosemeter. A set of eight environments were modelled based on the statistics of Rayleigh, Rice and log-normal fading to simulate outdoor and indoor multipath exposures at 450, 900 and 2100 MHz. Results indicate that a dosemeter mounted randomly within 10-50 mm of the adult or child body model (torso region) will on average underestimate the spatially averaged value of the incident electric field strength by a factor of 0.52 to 0.74 over the frequencies of 450, 900 and 2100 MHz. The uncertainty in results, assessed at the 95 % confidence level (between the 2.5th and 97.5th percentiles) was largest at 2100 MHz and smallest at 450 MHz.

  14. The Dynamics of Genetic Interactions between Vibrio metoecus and Vibrio cholerae, Two Close Relatives Co-Occurring in the Environment.

    Science.gov (United States)

    Orata, Fabini D; Kirchberger, Paul C; Méheust, Raphaël; Barlow, E Jed; Tarr, Cheryl L; Boucher, Yan

    2015-10-09

    Vibrio metoecus is the closest relative of Vibrio cholerae, the causative agent of the potent diarrheal disease cholera. Although the pathogenic potential of this new species is yet to be studied in depth, it has been co-isolated with V. cholerae in coastal waters and found in clinical specimens in the United States. We used these two organisms to investigate the genetic interaction between closely related species in their natural environment. The genomes of 20 V. cholerae and 4 V. metoecus strains isolated from a brackish coastal pond on the US east coast, as well as 4 clinical V. metoecus strains were sequenced and compared with reference strains. Whole genome comparison shows 86-87% average nucleotide identity (ANI) in their core genes between the two species. On the other hand, the chromosomal integron, which occupies approximately 3% of their genomes, shows higher conservation in ANI between species than any other region of their genomes. The ANI of 93-94% observed in this region is not significantly greater within than between species, meaning that it does not follow species boundaries. Vibrio metoecus does not encode toxigenic V. cholerae major virulence factors, the cholera toxin and toxin-coregulated pilus. However, some of the pathogenicity islands found in pandemic V. cholerae were either present in the common ancestor it shares with V. metoecus, or acquired by clinical and environmental V. metoecus in partial fragments. The virulence factors of V. cholerae are therefore both more ancient and more widespread than previously believed. There is high interspecies recombination in the core genome, which has been detected in 24% of the single-copy core genes, including genes involved in pathogenicity. Vibrio metoecus was six times more often the recipient of DNA from V. cholerae as it was the donor, indicating a strong bias in the direction of gene transfer in the environment. © The Author(s) 2015. Published by Oxford University Press on behalf of the

  15. The Origin and Formation of the Circumstellar Disk

    CERN Document Server

    Machida, Masahiro N

    2010-01-01

    The formation and evolution of the circumstellar disk in the collapsing molecular cloud is investigated from the prestellar stage resolving both the molecular cloud core and the protostar itself. In the collapsing cloud, the first adiabatic core appears prior to the protostar formation. Reflecting the thermodynamics of the collapsing gas, the first core is much more massive than the protostar. When the molecular cloud has no angular momentum, the first core falls onto the protostar and disappears a few years after the protostar formation. On the other hand, when the molecular cloud has an angular momentum, the first core does not disappear even after the protostar formation, and directly evolves into the circumstellar disk with a Keplerian rotation. There are two paths for the formation of the circumstellar disk. When the initial cloud has a considerably small rotational energy, two nested disks appear just after the protostar formation. During the early main accretion phase, the inner disk increases its size...

  16. The Circumstellar Medium of Massive Stars in Motion

    CERN Document Server

    Mackey, Jonathan; Meyer, Dominique M -A; Gvaramadze, Vasilii V; Mohamed, Shazrene; Neilson, Hilding R; Mignone, Andrea

    2014-01-01

    The circumstellar medium around massive stars is strongly impacted by stellar winds, radiation, and explosions. We use numerical simulations of these interactions to constrain the current properties and evolutionary history of various stars by comparison with observed circumstellar structures. Two- and three-dimensional simulations of bow shocks around red supergiant stars have shown that Betelgeuse has probably only recently evolved from a blue supergiant to a red supergiant, and hence its bow shock is very young and has not yet reached a steady state. We have also for the first time investigated the magnetohydrodynamics of the photoionised H II region around the nearby runaway O star Zeta Oph. Finally, we have calculated a grid of models of bow shocks around main sequence and evolved massive stars that has general application to many observed bow shocks, and which forms the basis of future work to model the explosions of these stars into their pre-shaped circumstellar medium.

  17. Photochemistry and molecular ions in carbon-rich circumstellar envelopes

    Science.gov (United States)

    Glassgold, A. E.; Mamon, G. A.; Omont, A.; Lucas, R.

    1987-01-01

    An earlier theory of ionization of C-rich circumstellar envelopes based on the photochemical model is extended to include the temperature dependence of ion-molecule reactions with polar molecules, particularly HCN, and line self-shielding of CO dissociating radiation. The results are applied to the abundances of HCO(+) and HNC in C-rich circumstellar envelopes. With standard parameters for IRC + 10216, the model is found to be consistent with the new upper limit to the antenna temperature of the J = 1-0 line of HCO(+) obtained with the IRAM 30-m telescope. The photochemical model provides a natural explanation of the relatively large ratio of HCN to HNC observed for C-rich circumstellar envelopes, and good agreement is obtained for the H(C-13)N/HNC antenna temperature ratio measured for IRC + 10216.

  18. ON THE RADIO AND NEAR-INFRARED JET OF PKS 2155-304 AND ITS CLOSE ENVIRONMENT

    Energy Technology Data Exchange (ETDEWEB)

    Liuzzo, E. [Istituto di Radioastronomia, INAF, Via Gobetti 101, I-40129 Bologna (Italy); Falomo, R.; Farinato, J.; Moretti, A.; Ragazzoni, R. [Osservatorio Astronomico di Padova, INAF, vicolo dell' Osservatorio 5, I-35122 Padova (Italy); Treves, A. [INAF and INFN, Universita dell' Insubria (Como), via Valleggio 11, I-22100 Como (Italy); Arcidiacono, C.; Diolaiti, E.; Lombini, M. [Osservatorio Astronomico di Bologna, INAF, Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Torresi, E. [INAF/IASF Bologna, Via Gobetti 101, I-40129 Bologna (Italy); Uslenghi, M. [INAF/IASF Milano, Via E. Bassini 15, I-20133 Milano (Italy); Brast, R. [Dipartimento di Astronomia, Universita di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Donaldson, R.; Kolb, J.; Marchetti, E.; Tordo, S., E-mail: liuzzo@ira.inaf.it [European Southern Observatory, Karl-Schwarschild-Str 2, D-85748 Garching bei Muenchen (Germany)

    2013-03-15

    PKS 2155-304 is one of the brightest BL Lac objects in the sky and a very well-studied target from radio to TeV bands. We report on high-resolution ({approx}0.''12) direct imaging of the field of PKS 2155-304 using adaptive optics near-IR (NIR) observations in the J and Ks bands obtained with the ESO Multi-Conjugate Adaptive Optics Demonstrator on the Very Large Telescope. These data are complemented with archival Very Large Array images at various frequencies to investigate the properties of the close environment of the source. We characterize the faint galaxies that form the poor group associated with the target. No radio emission is present for these galaxies, while an old radio jet at {approx}20 kpc from the nucleus of PKS 2155-304 and a jet-like structure of {approx}2 kpc ({approx}1'') in the eastern direction are revealed. No counterparts of these radio jets are found in the NIR or in archival Chandra observations.

  19. Hubble and Spitzer Observations of an Edge-on Circumstellar Disk around a Brown Dwarf

    CERN Document Server

    Luhman, K L; D'Alessio, Paola; Calvet, Nuria; McLeod, Kim K; Bohac, J; Forrest, William J; Hartmann, Lee; Sargent, B; Watson, Dan M

    2007-01-01

    We present observations of a circumstellar disk that is inclined close to edge-on around a young brown dwarf in the Taurus star-forming region. Using data obtained with SpeX at the NASA Infrared Telescope Facility, we find that the slope of the 0.8-2.5 um spectrum of the brown dwarf 2MASS J04381486+2611399 cannot be reproduced with a photosphere reddened by normal extinction. Instead, the slope is consistent with scattered light, indicating that circumstellar material is occulting the brown dwarf. By combining the SpeX data with mid-IR photometry and spectroscopy from the Spitzer Space Telescope and previously published millimeter data from Scholz and coworkers, we construct the spectral energy distribution for 2MASS J04381486+2611399 and model it in terms of a young brown dwarf surrounded by an irradiated accretion disk. The presence of both silicate absorption at 10 um and silicate emission at 11 um constrains the inclination of the disk to be ~70 deg, i.e. ~20 deg from edge-on. Additional evidence of the h...

  20. The PDS 66 Circumstellar Disk as seen in Polarized Light with the Gemini Planet Imager

    CERN Document Server

    Wolff, Schuyler G; Millar-Blanchaer, Maxwell A; Nielsen, Eric L; Wang, Jason; Cardwell, Andrew; Chilcote, Jeffrey; Dong, Ruobing; Draper, Zachary H; Duchene, Gaspard; Fitzgerald, Michael P; Goodsell, Stephen J; Grady, Carol A; Graham, James R; Greenbaum, Alexandra Z; Hartung, Markus; Hibon, Pascale; Hines, Dean C; Hung, Li-Wei; Kalas, Paul; Macintosh, Bruce; Marchis, Franck; Marois, Christian; Pueyo, Laurent; Rantakyro, Fredrik T; Schneider, Glenn; Sivaramakrishnan, Anand; Wiktorowicz, Sloane J

    2016-01-01

    We present H and K band imaging polarimetry for the PDS 66 circumstellar disk obtained during the commissioning of the Gemini Planet Imager (GPI). Polarization images reveal a clear detection of the disk in to the 0.12'' inner working angle (IWA) in H band, almost 3 times as close to the star as the previous HST observations with NICMOS and STIS (0.35'' effective IWA). The centro-symmetric polarization vectors confirm that the bright inner disk detection is due to circumstellar scattered light. A more diffuse disk extends to a bright outer ring centered at 80 AU. We discuss several physical mechanisms capable of producing the observed ring + gap structure. GPI data confirm enhanced scattering on the East side of the disk which is inferred to be nearer to us. We also detect a lateral asymmetry in the South possibly due to shadowing from material within the inner working angle. This likely corresponds to a temporally variable azimuthal asymmetry observed in HST/STIS coronagraphic imaging.

  1. Gas phase chemical kinetics at high temperature of carbonaceous molecules: application to circumstellar envelopes

    Science.gov (United States)

    Biennier, L.; Gardez, A.; Saidani, G.; Georges, R.; Rowe, B.; Reddy, K. P. J.

    2011-05-01

    Circumstellar shells of evolved stars are a theater of extremely rich physical and chemical processes. More than seventy molecules of varied nature have been identified in the envelopes through their spectral fingerprints in the microwave or far infrared regions. Many of them are carbon chain molecules and radicals and a significant number are unique to the circumstellar medium. However, observational data remain scarce and more than half of the detected species have been observed in only one object, the nearby carbon star IRC + 10216. Chemical kinetic models are needed to describe the formation of molecules in evolved circumstellar outflows. Upcoming terrestrial telescopes such as ALMA will increase the spatial resolution by several orders of magnitude and provide a wealth of data. The determination of relevant laboratory kinetics data is critical to keep up with the development of the observations and of the refinement of chemical models. Today, the majority of reactions studied in the laboratory are the ones involved in combustion and concerning light hydrocarbons. Our objective is to provide the scientific community with rate coefficients of reactions between abundant species in these warm environments. Cyanopolyynes from HC_2N to HC_9N have all been detected in carbon rich circumstellar envelopes in up to 10 sources for HC_3N. Neutral-neutral reactions of the CN radical with unsaturated hydrocarbons could be a dominant route in the formation of cyanopolyynes, even at low temperatures. Our approach aims to bridge the temperature gap between resistively heated flow tubes and shock tubes. The present kinetic measurements are obtained using a new reactor combining a high enthalpy source (Moudens et al. 2011) with a flow tube and a pulsed laser photolysis and laser induced fluorescence system to probe the undergoing chemical reactions. The high enthalpy flow tube has been used to measure the rate constant of the reaction of the CN radical with propane, propene

  2. A search of diffuse bands in fullerene planetary nebulae: evidence for diffuse circumstellar bands

    CERN Document Server

    Diaz-Luis, J J; Rao, N Kameswara; Manchado, A; Cataldo, F

    2014-01-01

    Large fullerenes and fullerene-based molecules have been proposed as carriers of diffuse interstellar bands (DIBs). The recent detection of the most common fullerenes (C60 and C70) around some Planetary Nebulae (PNe) now enable us to study the DIBs towards fullerene-rich space environments. We search DIBs in the optical spectra towards three fullerene-containing PNe (Tc 1, M 1-20, and IC 418). Special attention is given to DIBs which are found to be unusually intense towards these fullerene sources. In particular, an unusually strong 4428A absorption feature is a common charateristic to fullerene PNe. Similarly to Tc 1, the strongest optical bands of neutral C60 are not detected towards IC 418. Our high-quality (S/N > 300) spectra for PN Tc 1 together with its large radial velocity permits us to search for the presence of diffuse bands of circumstellar origin which we refer to as diffuse circumstellar bands (DCBs). We report the first tentative detection of two DCBs at 4428 and 5780 A in the fullerene-rich ci...

  3. Optical Evidence for Circumstellar Interaction Around SN 1993J

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-Feng; ZHANG Tian-Meng; ZHOU Xu; LI Zong-Wei

    2004-01-01

    We study the circumstellar interaction around SN 1993J by its intermediate-band light curves obtained by the 60/90 cm Schmidt telescope at Xinglong station. The optical emission showed a slow decay of 0.05±0.02 mag/100 d in the period from 1995 to 2003, invoking a main energy contribution from SN-circumstellar interaction at late times. The relatively flat power law SN density model fits better with the observations. In particular, the line ratio of [O Ⅲ]λλ4959, 5007 and Na I D relative to Hα are well reproduced by the model. Moreover, the Hα light curve displayed obvious bump structures at some epochs, which is probably attributed to the density fluctuations in the ambient material that surrounds the reverse shockwave.

  4. Spectroscopic diagnostics for circumstellar disks of B[e] supergiants

    CERN Document Server

    Kraus, Michaela

    2016-01-01

    B[e] supergiants (B[e]SGs) are emission-line objects, presumably in a short-lived phase in the post-main sequence evolution of massive stars. Their intense infrared excess emission indicates large amounts of warm circumstellar dust, and the stars were longtime assumed to possess an aspherical wind consisting of a classical line-driven wind in polar direction and a dense, slow equatorial wind dubbed outflowing disk. The general properties obtained for these disks are in line with this scenario, although current theories have considerable difficulties reproducing the observed quantities. Therefore, more sophisticated observational constraints are needed. These follow from combined optical and infrared spectroscopic studies, which delivered the surprising result that the circumstellar material of B[e]SGs is concentrated in multiple rings revolving the stars on stable Keplerian orbits. Such a scenario requires new ideas for the formation mechanism, in which pulsations might play an important role.

  5. Proper Motions of Water Masers in Circumstellar Shells

    Science.gov (United States)

    Marvel, K. B.; Diamond, P. J.; Kemball, A. J.

    We present proper motion measurements of circumstellar water masers obtained with the VLBA. The objects observed include S Persei, VX Sagittarii, U Herculis, VY Canis Majoris, NML Cygni, IK Tauri and RX Bootis. Results of the observations and modeling indicate that the water masers exist in a kinematically complex region of the circumstellar envelope, which is not well fit by the standard model of a uniformly expanding spherical wind. Attempts at fitting an ellipsoidal geometric distribution with a variety of kinematic models are presented. Estimates for the distances of the stars are also discussed. A change in position of the maser spots as a function of velocity has been measured. This effect may be used to place limits on accelerations in the masing gas.

  6. Prospecting for planets in circumstellar dust - Sifting the evidence from Beta Pictoris

    Science.gov (United States)

    Diner, D. J.; Appleby, J. F.

    1986-01-01

    IRAS and near-IR coronographic data for the A5V star Beta Pic are analyzed for evidence of planetary formation. The light scattered from the central star in the system is integrated along the distance to the star to determine the disk magnitude at various distances from the star. A modified gamma distribution is applied to evaluate the scattering coefficient to test a hypothesis that the inner 30 AU of the disk has been swept out by planets. The scattering from the region around Beta Pic is compared with scattering around other A5V stars. Finally, the IR data at 0.89 micron is compared with scattering at the coronograph wavelengths. No evidence is found to support the hypothesis of clearing in the inner disk, although large particle densities can be found very close to Beta Pic. The study illustrates the effectiveness of using scattered light and IR data to discover and characterize matter distributions circumstellar disks.

  7. X-ray Emission from Strongly Asymmetric Circumstellar Material in the Remnant of Kepler's Supernova

    CERN Document Server

    Burkey, Mary T; Borkowski, Kazimierz J; Blondin, John M

    2012-01-01

    Kepler's supernova remnant resulted from a thermonuclear explosion, but is interacting with circumstellar material (CSM) lost from the progenitor system. We describe a statistical technique for isolating X-ray emission due to CSM from that due to shocked ejecta. Shocked CSM coincides well in position with 24 $\\mu$m emission seen by {\\sl Spitzer}. We find most CSM to be distributed along the bright north rim, but substantial concentrations are also found projected against the center of the remnant, roughly along a diameter with position angle $\\sim 100^\\circ$. We interpret this as evidence for a disk distribution of CSM before the SN, with the line of sight to the observer roughly in the disk plane. We present 2-D hydrodynamic simulations of this scenario, in qualitative agreement with the observed CSM morphology. Our observations require Kepler to have originated in a close binary system with an AGB star companion.

  8. A Hidden Population of Massive Stars with Circumstellar Shells Discovered with the Spitzer Space Telescope

    CERN Document Server

    Wachter, S; Van Dyk, S D; Hoard, D W; Kafka, S; Morris, P W

    2010-01-01

    We have discovered a large number of circular and elliptical shells at 24 microns around luminous central sources with the MIPS instrument on-board the Spitzer Space Telescope. Our archival follow-up effort has revealed 90% of these circumstellar shells to be previously unknown. The majority of the shells is only visible at 24 microns, but many of the central stars are detected at multiple wavelengths from the mid- to the near-IR regime. The general lack of optical counterparts, however, indicates that these sources represent a population of highly obscured objects. We obtained optical and near-IR spectroscopic observations of the central stars and find most of these objects to be massive stars. In particular, we identify a large population of sources that we argue represents a narrow evolutionary phase, closely related or identical to the LBV stage of massive stellar evolution.

  9. Observations of Circumstellar Thermochemical Equilibrium: The Case of Phosphorus

    Science.gov (United States)

    Milam, Stefanie N.; Charnley, Steven B.

    2011-01-01

    We will present observations of phosphorus-bearing species in circumstellar envelopes, including carbon- and oxygen-rich shells 1. New models of thermochemical equilibrium chemistry have been developed to interpret, and constrained by these data. These calculations will also be presented and compared to the numerous P-bearing species already observed in evolved stars. Predictions for other viable species will be made for observations with Herschel and ALMA.

  10. Dispersal of Gaseous Circumstellar Discs around High-Mass Stars

    CERN Document Server

    Shen, Y; Shen, Yue; Lou, Yu-Qing

    2006-01-01

    We study the dispersal of a gaseous disc surrounding a central high-mass stellar core once this circumstellar disc becomes fully ionized. If the stellar and surrounding EUV and X-ray radiations are so strong as to rapidly heat up and ionize the entire circumstellar disc as further facilitated by disc magnetohydrodynamic (MHD) turbulence, a shock can be driven to travel outward in the fully ionized disc, behind which the disc expands and thins. For an extremely massive and powerful stellar core, the ionized gas pressure overwhelms the centrifugal and gravitational forces in the disc. In this limit, we construct self-similar shock solutions for such an expansion and depletion phase. As a significant amount of circumstellar gas being removed, the relic disc becomes vulnerable to strong stellar winds and fragments into clumps. We speculate that disc disappearance happens rapidly, perhaps on a timescale of $\\sim 10^3-10^4\\hbox{yr}$ once the disc becomes entirely ionized sometime after the onset of thermal nuclear ...

  11. Grand Design Spiral Arms in A Young Forming Circumstellar Disk

    CERN Document Server

    Tomida, Kengo; Hosokawa, Takashi; Sakurai, Yuya; Lin, Chia Hui

    2016-01-01

    We study formation and long-term evolution of a circumstellar disk in a collapsing molecular cloud core using a resistive magnetohydrodynamic simulation. While the formed circumstellar disk is initially small, it grows as accretion continues and its radius becomes as large as 200 AUs toward the end of the Class-I phase. A pair of grand-design spiral arms form due to gravitational instability in the disk, and they transfer angular momentum in the highly resistive disk. Although the spiral arms disappear in a few rotations as expected in a classical theory, new spiral arms form recurrently as the disk soon becomes unstable again by gas accretion. Such recurrent spiral arms persist throughout the Class-0 and I phase. We then perform synthetic observations and compare our model with a recent high-resolution observation of a young stellar object Elias 2-27, whose circumstellar disk has grand design spiral arms. We find an excellent agreement between our theoretical model and the observation. Our model suggests tha...

  12. Molecular content of the circumstellar disk in AB Aur: First detection of SO in a circumstellar disk

    CERN Document Server

    Fuente, A; Agundez, M; Berne, O; Goicoechea, J R; Alonso-Albi, T; Marcelino, N

    2010-01-01

    Very few molecular species have been detected in circumstellar disks surrounding young stellar objects. We are carrying out an observational study of the chemistry of circumstellar disks surrounding T Tauri and Herbig Ae stars. First results of this study are presented in this note. We used the EMIR receivers recently installed at the IRAM 30m telescope to carry a sensitive search for molecular lines in the disks surrounding AB Aur, DM Tau, and LkCa 15. We detected lines of the molecules HCO+, CN, H2CO, SO, CS, and HCN toward AB Aur. In addition, we tentatively detected DCO+ and H2S lines. The line profiles suggest that the CN, HCN, H2CO, CS and SO lines arise in the disk. This makes it the first detection of SO in a circumstellar disk. We have unsuccessfully searched for SO toward DM Tau and LkCa 15, and for c-C3H2 toward AB Aur, DM Tau, and LkCa 15. Our upper limits show that contrary to all the molecular species observed so far, SO is not as abundant in DM Tau as it is in AB Aur. Our results demonstrate th...

  13. Connecting the evolution of thermally pulsing asymptotic giant branch stars to the chemistry in their circumstellar envelopes - I. Hydrogen cyanide

    Science.gov (United States)

    Marigo, Paola; Ripamonti, Emanuele; Nanni, Ambra; Bressan, Alessandro; Girardi, Léo

    2016-02-01

    We investigate the formation of hydrogen cyanide (HCN) in the inner circumstellar envelopes of thermally pulsing asymptotic giant branch (TP-AGB) stars. A dynamic model for periodically shocked atmospheres, which includes an extended chemo-kinetic network, is for the first time coupled to detailed evolutionary tracks for the TP-AGB phase computed with the COLIBRI code. We carried out a calibration of the main shock parameters (the shock formation radius rs,0 and the effective adiabatic index γ _ad^eff) using the circumstellar HCN abundances recently measured for a populous sample of pulsating TP-AGB stars. Our models recover the range of the observed HCN concentrations as a function of the mass-loss rates, and successfully reproduce the systematic increase of HCN moving along the M-S-C chemical sequence of TP-AGB stars, which traces the increase of the surface C/O ratio. The chemical calibration brings along two important implications for the physical properties of the pulsation-induced shocks: (i) the first shock should emerge very close to the photosphere (rs,0 ≃ 1R), and (ii) shocks are expected to have a dominant isothermal character (γ _ad^eff˜eq 1) in the denser region close to the star (within ˜3-4R), implying that radiative processes should be quite efficient. Our analysis also suggests that the HCN concentrations in the inner circumstellar envelopes are critically affected by the H-H2 chemistry during the post-shock relaxation stages. Given the notable sensitiveness of the results to stellar parameters, this paper shows that such chemo-dynamic analyses may indeed provide a significant contribution to the broader goal of attaining a comprehensive calibration of the TP-AGB evolutionary phase.

  14. Where do Wet, Dry, and Mixed Galaxy Mergers Occur? A Study of the Environments of Close Galaxy Pairs in the DEEP2 Galaxy Redshift Survey

    CERN Document Server

    Lin, Lihwai; Jian, Hung-Yu; Koo, David C; Patton, David R; Yan, Renbin; Willmer, Christopher N A; Coil, Alison L; Chiueh, Tzihong; Croton, Darren J; Gerke, Brian F; Lotz, Jennifer; Guhathakurta, Puragra; Newman, Jeffrey A

    2010-01-01

    We study the environment of wet, dry, and mixed galaxy mergers at 0.75 < z < 1.2 using close pairs in the DEEP2 Galaxy Redshift Survey. We find that the typical environment of mixed and dry merger candidates is denser than that of wet mergers, mostly due to the color-density relation. While the galaxy companion rate (Nc) is observed to increase with overdensity, using N-body simulations we find that the fraction of pairs that will eventually merge decreases with the local density, predominantly because interlopers are more common in dense environments. After taking into account the merger probability of pairs as a function of local density, we find only marginal environment dependence of the fractional merger rate for wet mergers over the redshift range we have probed. On the other hand, the fractional dry merger rate increases rapidly with local density due to the increased population of red galaxies in dense environments. We also find that the environment distribution of K+A galaxies is similar to tha...

  15. Evolution of hydraulic traits in closely related species pairs from Mediterranean and nonMediterranean environments of North America.

    Science.gov (United States)

    Bhaskar, Radika; Valiente-Banuet, Alfonso; Ackerly, David D

    2007-01-01

    Chaparral shrubs in California experience cool, wet winters and hot, dry summers characteristic of mediterranean-type climates; by contrast, morphologically similar close relatives in central Mexico experience summer rainfall. A comparison of closely related species pairs was conducted to examine whether evolutionary divergences in plant hydraulic conductivity were associated with contrasting seasonality of precipitation. Six species pairs in Santa Barbara, California and Tehuacan, Mexico were chosen to test for repeated directional divergences across the habitat contrast. Additionally, evolutionary correlations were examined using phylogenetically independent contrasts (PICs) among a suite of hydraulic traits, including stem- and leaf-specific conductivity, resistance to embolism, wood density, inverse Huber value, and minimum seasonal water potential. Leaf-specific conductivity was generally higher in California, but for most hydraulic traits the species pairs exhibited varied evolutionary trajectories across the climate contrast. A significant correlation was found between divergences in xylem resistance to embolism and minimum seasonal water potential, but no evolutionary trade-off was found between resistance and stem conductivity. Higher leaf-specific conductivity may be adaptive in California, where soil and atmospheric droughts coincide during summer months. This response is consistent with a hydraulic strategy of high leaf water supply under high evaporative demand to prevent excessive drops in water potential.

  16. A HOT MOLECULAR CIRCUMSTELLAR DISK AROUND THE MASSIVE PROTOSTAR ORION SOURCE I

    Energy Technology Data Exchange (ETDEWEB)

    Hirota, Tomoya; Honma, Mareki [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Kim, Mi Kyoung [Korea Astronomy and Space Science Institute, Hwaam-dong 61-1, Yuseong-gu, Daejeon, 305-348 (Korea, Republic of); Kurono, Yasutaka, E-mail: tomoya.hirota@nao.ac.jp [Chile Observatory, National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588 (Japan)

    2014-02-20

    We report new Atacama Large Millimeter/Submillimeter Array (ALMA) observations of a circumstellar disk around Source I in Orion KL, an archetype of massive protostar candidates. We detected two ortho-H{sub 2}O lines at 321 GHz (10{sub 2,} {sub 9}-9{sub 3,} {sub 6}) and 336 GHz (ν{sub 2} = 1, 5{sub 2,} {sub 3}-6{sub 1,} {sub 6}) for the first time in Source I. The latter one is in a vibrationally excited state at the lower state energy of 2939 K, suggesting evidence of hot molecular gas close to Source I. The integrated intensity map of the 321 GHz line is elongated along the bipolar outflow while the 336 GHz line map is unresolved with a beam size of 0.''4. Both of these maps show velocity gradients perpendicular to the bipolar outflow. The velocity centroid map of the 321 GHz line implies a spatial and velocity structure similar to that of vibrationally excited SiO masers tracing the root of the outflow emanating from the disk surface. In contrast, the 336 GHz line is most likely emitting from the disk midplane with a diameter of 0.''2 (84 AU) as traced by radio continuum emission and a dark lane devoid of the vibrationally excited SiO maser emission. The observed velocity gradient and the spectral profile of the 336 GHz H{sub 2}O line can be reconciled with a model of an edge-on ring-like structure with an enclosed mass of >7 M{sub ☉} and an excitation temperature of >3000 K. The present results provide further evidence of a hot and neutral circumstellar disk rotating around Source I with a diameter of ∼100 AU scale.

  17. Study of some CVD intensifying lipids over a period of aerobic exercise in the open and closed environment

    Directory of Open Access Journals (Sweden)

    Hassan darvakh

    2016-08-01

    Full Text Available Regarding the importance of physical activity in preventing lipids disorders, this study was done with the goal of comparing one type of aerobic exercise in open and closed place on some lipids intensify CVD disorders, In this study, 45 healthy middle aged postmenopausal women were randomly divided into 3 groups of 15, tow earobic exercise and control. First, the heart rate was measured (04/15 ± 47/80, then maximal oxygen consumption (22.65 ± 1.46 and the body dimensions, including height ( 156.7 ± 6.72 weight (68.87 ± 9.22 and body mass i ndex (28.74 ± 1.78, then, cholesterol, VLDL and triglycerides values were studied in Laboratory. Time and intensity of exercise were identical for two groups. Increasing intensity of 50-70% of maximum heart rate was in 12 weeks, 30 to 90 minutes, and 5 times a week (30 minutes at 50% MHR intensity for the first week and 90 minutes of 70 percent MHR in the last week. After the training period, cholesterol, VLDL and triglycerides values were measured again and the data were analyzed with the dependent T-test, MANOVA and TUKY follow-up test. The results indicate that differences between exercise groups and control group were significant. Accordingly, the results of exercise group in open place had significant effects on reducing mean cholesterol, VLDL and triglycerides (P≤0.05. And aerobic exercise in closed place had significant effects on reducing mean cholesterol, VLDL but had not significant effects on reducing mean triglycerides and there was significant difference in VLDL values between two groups after 12 weeks (P≤0.05 as the open place group showed higher mean. As the exercise group in open place showed higher mean, this study showed that aerobic exercise, either exercise group in open place or in the exercise group in closed place causes decrease in the mean of some blood lipids like cholesterol, VLDL and triglycerides in postmenopausal women, among which exercise group in open place maby

  18. The Velocity Structure of SN 1987A's Outer Circumstellar Envelope

    Science.gov (United States)

    Crotts, A. P. S.; Heathcote, S. R.

    1997-12-01

    We present high-resolution optical spectroscopy, (obtained with the CTIO 4-meter/echelle spectrograph over many epochs between 1989 and 1997) of the circumstellar nebula of SN 1987A, including the outer rings (within 3 arcsec of the SN), the inner (equatorial) ring, and fainter features at larger radii never studied before spectroscopically. We report velocity displacements for portions of the outer rings, up to 26 km s(-1) with respect the SN centroid velocity, with blueshifted components in the location of the southern outer ring and the redshifted portions of the northern outer ring. The largest shifts are near the SN, as predicted by a model in which the outer rings are the crowns of an expanding, bipolar nebula with the inner ring at its waist. We also confirm that the inner ring shows a velocity full-width of about 13 km s(-1) , which, along with the geometry of the rings and our outer ring velocity measurements, allows us to estimate a characteristic timescale of about 20,000 y for each of the three rings, implying that all are coeval. This contrasts with measurements by others of compositional ratios in the inner versus outer rings indicating that they were, perhaps, ejected at different times from the progenitor's star's outer envelope. Additionally, we measure the velocity of low surface brightness features at larger radii indicating that circumstellar material even farther from the SN was ejected up to 400,000 y before the explosion. Finally, we note the presence of transient emission features within the circumstellar nebula and describe their behaviour, and consider what implications our observations may have for the coming transformation of this nebula into Supernova Remnant 1987A.

  19. The circumstellar medium of the peculiar supernova SN1997ab

    CERN Document Server

    Salamanca, I M; Tenorio-Tagle, G; Telles, E; Terlevich, R J; Muñoz-Tunón, C; Salamanca, Isabel; Cid-Fernandes, Roberto; Tenorio-Tagle, Guillermo; Telles, Eduardo; Terlevich, Roberto J.; Munoz-Tunon, Casiana

    1998-01-01

    We report the detection of the slow moving wind into which the compact supernova remnant SN 1997ab is expanding. Echelle spectroscopy provides clear evidence for a well resolved narrow (Full Width at Zero Intensity, FWZI ~ 180 km/s) P-Cygni profile, both in Ha and Hb, superimposed on the broad emission lines of this compact supernova remnant. From theoretical arguments we know that the broad and strong emission lines imply a circumstellar density (n ~ 10^7 cm^-3). This, together with our detection, implies a massive and slow stellar wind experienced by the progenitor star shortly prior to the explosion.

  20. Protonated acetylene - An important circumstellar and interstellar ion

    Science.gov (United States)

    Glassgold, A. E.; Omont, A.; Guelin, M.

    1992-01-01

    In a circumstellar envelope, a substantial amount of acetylene is transported in a wind to the outer envelope, where it can be photoionized by interstellar radiation and then converted into C2H3(+) by a low-temperature reaction with H2. New chemical modeling calculations indicate that sufficient C2H3(+) may be produced in the outer envelope of IRC + 10216 to be observable. Similar considerations suggest that C2H3(+) should also be detectable in interstellar clouds, provided its rotational spectrum has been measured accurately in the laboratory.

  1. BF Orionis - Evidence for an infalling circumstellar envelope

    Science.gov (United States)

    Welty, Alan D.; Barden, Samuel C.; Huenemoerder, David P.; Ramsey, Lawrence W.

    1992-01-01

    Analysis of the optical magnitudes and Balmer lines of the Herbig Ae/Be star BF Orionis confirm that the object is an early to mid A-type star, but appears to be below the zero-age main sequence. Enhanced metal-line strengths (once thought to link BF Ori with the Am stars), line asymmetries, and radial velocities are shown to be signatures of an infalling circumstellar envelope. The possibility that BF Ori has a late-type companion is examined, and it is concluded that it does not.

  2. The effect of surfaces type on vibration behavior of piezoelectric micro-cantilever close to sample surface in a humid environment based on MCS theory

    Science.gov (United States)

    Korayem, M. H.; Korayem, A. H.

    2016-08-01

    Atomic force microscopy (AFM) has been known as an innovative tool in the fields of surface topography, determination of different mechanical properties and manipulation of particles at the micro- and nanoscales. This paper has been concerned with advanced modeling and dynamic simulation of AFM micro-cantilever (MC) in the amplitude mode in the air environment. To increase the accuracy of the governing equations, modified couple stress theory appropriate in micro- and nanoscales has been utilized based on Timoshenko beam theory in the air environment near the sample surface. Also, to discretize the equations, differential quadrature method has been recommended. In modeling, geometric discontinuities due to the presence of a piezoelectric layer enclosed between two electrode layers and the change in MC cross section when connected to the MC have been considered. In addition to the effect of MC modeling on the accuracy of modeling and vibration amplitude during surface topography, understanding and modeling the environmental forces in the air environment, including van der Waals, capillary and contact forces, are important. This paper has been provided more accurate environmental forces modeling and has been investigated the vibration behavior of piezoelectric MC in the humid environment. Moreover, this paper has been examined the maximum and minimum MC amplitude in the air environment close to the surface with different kinds of topography. The results illustrate that kind of surfaces has effect on the maximum and minimum amplitude due to the decrease or increase in equilibrium MC distance.

  3. Environment

    DEFF Research Database (Denmark)

    Valentini, Chiara

    2017-01-01

    The term environment refers to the internal and external context in which organizations operate. For some scholars, environment is defined as an arrangement of political, economic, social and cultural factors existing in a given context that have an impact on organizational processes and structures....... For others, environment is a generic term describing a large variety of stakeholders and how these interact and act upon organizations. Organizations and their environment are mutually interdependent and organizational communications are highly affected by the environment. This entry examines the origin...... and development of organization-environment interdependence, the nature of the concept of environment and its relevance for communication scholarships and activities....

  4. Effects of a Closed Space Environment on Gene Expression in Hair Follicles of Astronauts in the International Space Station.

    Directory of Open Access Journals (Sweden)

    Masahiro Terada

    Full Text Available Adaptation to the space environment can sometimes pose physiological problems to International Space Station (ISS astronauts after their return to earth. Therefore, it is important to develop healthcare technologies for astronauts. In this study, we examined the feasibility of using hair follicles, a readily obtained sample, to assess gene expression changes in response to spaceflight adaptation. In order to investigate the gene expression changes in human hair follicles during spaceflight, hair follicles of 10 astronauts were analyzed by microarray and real time qPCR analyses. We found that spaceflight alters human hair follicle gene expression. The degree of changes in gene expression was found to vary among individuals. In some astronauts, genes related to hair growth such as FGF18, ANGPTL7 and COMP were upregulated during flight, suggesting that spaceflight inhibits cell proliferation in hair follicles.

  5. Effects of a Closed Space Environment on Gene Expression in Hair Follicles of Astronauts in the International Space Station.

    Science.gov (United States)

    Terada, Masahiro; Seki, Masaya; Takahashi, Rika; Yamada, Shin; Higashibata, Akira; Majima, Hideyuki J; Sudoh, Masamichi; Mukai, Chiaki; Ishioka, Noriaki

    2016-01-01

    Adaptation to the space environment can sometimes pose physiological problems to International Space Station (ISS) astronauts after their return to earth. Therefore, it is important to develop healthcare technologies for astronauts. In this study, we examined the feasibility of using hair follicles, a readily obtained sample, to assess gene expression changes in response to spaceflight adaptation. In order to investigate the gene expression changes in human hair follicles during spaceflight, hair follicles of 10 astronauts were analyzed by microarray and real time qPCR analyses. We found that spaceflight alters human hair follicle gene expression. The degree of changes in gene expression was found to vary among individuals. In some astronauts, genes related to hair growth such as FGF18, ANGPTL7 and COMP were upregulated during flight, suggesting that spaceflight inhibits cell proliferation in hair follicles.

  6. The Government’s Environment Policy Index Impact on Recycler Behavior in Electronic Products Closed-Loop Supply Chain

    Directory of Open Access Journals (Sweden)

    Suchao He

    2016-01-01

    Full Text Available We establish the model of multilevel closed-loop supply chain (CLSC which included raw material supplier, manufacturer, distributor, retailer, and third-party recycler based on system dynamics (SD. Considering factors which influence recycler behavior-environmental policy index and recovery delay, we apply SD software—Vensim—to simulate CLSC model and study recycler behavior’s influence on the entire CLSC through calculating the bullwhip effect of all levels members order rate. Research shows that (1 the larger the environmental policy index, the greater the recycle proportion and the better the effect of weakening retailer’s order rate in forward supply chain, which however, increasingly, strengthen the reverse supply chain bullwhip effect, (2 the shorter the recovery delay, the better the effect of weakening the forward supply chain bullwhip effect and the longer the recovery delay, which increasingly weakens the reverse supply chain bullwhip effect, and (3 the effect of environmental policy index on the bullwhip effect of all levels members order rate is more significant than recovery delay.

  7. Revealing the inclined circumstellar disk in the UX Ori system KK Ophiuchi

    Science.gov (United States)

    Kreplin, A.; Weigelt, G.; Kraus, S.; Grinin, V.; Hofmann, K.-H.; Kishimoto, M.; Schertl, D.; Tambovtseva, L.; Clausse, J.-M.; Massi, F.; Perraut, K.; Stee, Ph.

    2013-07-01

    We study the inner sub-AU region of the circumstellar environment of the UX Ori type star KK Oph with near-infrared VLTI/AMBER interferometry. We are particularly interested in the inclination of the star-disk system, and we will use this information to test the current standard picture for UX Ori stars. We recorded spectrally dispersed (R˜35) interferograms in the near-infrared H and K bands with the VLTI/AMBER instrument. The derived visibilities, closure phases and the SED of KK Oph were compared with two-dimensional geometric and radiative transfer models (RADMC). We obtained visibilities at four different position angles. Using two-dimensional geometric models, we derive an axis ratio ˜3.0 corresponding to an inclination of ˜70 degree. A fitted inclined ring model leads to a ring radius of 2.8 ± 0.2 mas, corresponding to 0.44 ± 0.03 AU at a distance of 160 pc, which is larger than the dust sublimation radius of ˜0.1 AU predicted for a dust sublimation temperature of 1500 K. Our derived two-dimensional RADMC model consists of a circumstellar disk with an inclination angle of ˜70 degree and an additional dust envelope. The finding of an ˜70 degree inclined disk around KK Oph is consistent with the prediction that UX Ori objects are seen under large inclination angles, and orbiting clouds in the line of sight cause the observed variability. Furthermore, our results suggest that the orbit of the companion KK Oph B and the disk plane are coplanar.

  8. Revealing the inclined circumstellar disk in the UX Orionis system KK Ophiuchi

    Science.gov (United States)

    Kreplin, A.; Weigelt, G.; Kraus, S.; Grinin, V.; Hofmann, K.-H.; Kishimoto, M.; Schertl, D.; Tambovtseva, L.; Clausse, J.-M.; Massi, F.; Perraut, K.; Stee, Ph.

    2013-03-01

    Aims: We study the inner sub-AU region of the circumstellar environment of the UX Ori-type star KK Oph with near-infrared VLTI/AMBER interferometry. We are particularly interested in the inclination of the star-disk system, and we use this information to test the current standard picture for UX Ori stars. Methods: We recorded spectrally dispersed (R ~ 35) interferograms in the near-infrared H and K bands with the VLTI/AMBER instrument. The derived visibilities, closure phases, and the spectral energy distribution of KK Oph were compared with two-dimensional geometric and radiative transfer models (RADMC). Results: We obtained visibilities at four different position angles. Using two-dimensional geometric models, we derive an axis ratio ~3.0 corresponding to an inclination of ~70°. A fitted inclined ring model leads to a ring radius of 2.8 ± 0.2 mas, corresponding to 0.44 ± 0.03 AU at a distance of 160 pc, which is larger than the dust sublimation radius of ~0.1 AU predicted for a dust sublimation temperature of 1500 K. Our derived two-dimensional RADMC model consists of a circumstellar disk with an inclination angle of ~70° and an additional dust envelope. Conclusions: The finding of an ~70° inclined disk around KK Oph is consistent with the prediction that UX Ori objects are seen under large inclination angles, and orbiting clouds in the line of sight cause the observed variability. Furthermore, our results suggest that the orbit of the companion KK Oph B and the disk plane are coplanar. Based on observations made with ESO telescopes at Paranal Observatory under program ID: 083.D-0224(C) and 088.C-0575(A).

  9. The circumstellar envelope of the C-rich post-AGB star HD 56126

    NARCIS (Netherlands)

    Hony, S; Tielens, AGGM; Waters, LBFM; de Koter, A

    2003-01-01

    We present a detailed study of the circumstellar envelope of the post-asymptotic giant branch "21 mum object" HD 56126. We build a detailed dust radiative transfer model of the circumstellar envelope in order to derive the dust composition and mass, and the mass-loss history of the star. To model th

  10. On the gas temperature in circumstellar disks around A stars

    CERN Document Server

    Kamp, I; Kamp, Inga; Zadelhoff, Gerd-Jan van

    2001-01-01

    In circumstellar disks or shells it is often assumed that gas and dust temperatures are equal where the latter is determined by radiative equilibrium. This paper deals with the question whether this assumption is applicable for tenous circumstellar disks around young A stars. In this paper the thin hydrostatic equilibrium models described by Kamp & Bertoldi (2000) are combined with a detailed heating/cooling balance for the gas. The most important heating and cooling processes are heating through infrared pumping, heating due to the drift velocity of dust grains, and fine structure and molecular line cooling. Throughout the whole disk gas and dust are not efficiently coupled by collisions and hence their temperatures are quite different. Most of the gas in the disk models considered here stays well below 300 K. In the temperature range below 300 K the gas chemistry is not much affected by T_gas and therefore the simplifying approximation T_gas = T_dust can be used for calculating the chemical structure of...

  11. Circumstellar Material on and off the Main Sequence

    Science.gov (United States)

    Steele, Amy; Debes, John H.; Deming, Drake

    2017-06-01

    There is evidence of circumstellar material around main sequence, giant, and white dwarf stars that originates from the small-body population of planetary systems. These bodies tell us something about the chemistry and evolution of protoplanetary disks and the planetary systems they form. What happens to this material as its host star evolves off the main sequence, and how does that inform our understanding of the typical chemistry of rocky bodies in planetary systems? In this talk, I will discuss the composition(s) of circumstellar material on and off the main sequence to begin to answer the question, “Is Earth normal?” In particular, I look at three types of debris disks to understand the typical chemistry of planetary systems—young debris disks, debris disks around giant stars, and dust around white dwarfs. I will review the current understanding on how to infer dust composition for each class of disk, and present new work on constraining dust composition from infrared excesses around main sequence and giant stars. Finally, dusty and polluted white dwarfs hold a unique key to our understanding of the composition of rocky bodies around other stars. In particular, I will discuss WD1145+017, which has a transiting, disintegrating planetesimal. I will review what we know about this system through high speed photometry and spectroscopy and present new work on understanding the complex interplay of physics that creates white dwarf pollution from the disintegration of rocky bodies.

  12. The Circumstellar Disk of the Be Star $o$~Aquarii

    CERN Document Server

    Sigut, T A A; Jansen, B; Zavala, R T

    2015-01-01

    Omicron Aquarii is late-type, Be shell star with a stable and nearly symmetric H$\\alpha$ emission line. We combine H$\\alpha$ interferometric observations obtained with the Navy Precision Optical Interferometer (NPOI) covering 2007 through 2014 with H$\\alpha$ spectroscopic observations over the same period and a 2008 observation of the system's near-infrared spectral energy distribution to constrain the properties of $o$~Aqr's circumstellar disk. All observations are consistent with a circumstellar disk seen at an inclination of $75\\pm\\,3^{\\circ}$ with a position angle on the sky of $110\\pm\\,8^{\\circ}$ measured E from N. From the best-fit disk density model, we find that 90\\% of the H$\\alpha$ emission arises from within $9.5$ stellar radii, and the mass associated with this H$\\alpha$ disk is $\\sim 1.8\\times10^{-10}$ of the stellar mass and the associated angular momentum, assuming Keplerian rotation for the disk, is $\\sim 1.6\\times10^{-8}$ of the total stellar angular momentum. The occurrence of a central quas...

  13. First Evidence of Circumstellar Disks around Blue Straggler Stars

    CERN Document Server

    De Marco, O; Ouellette, J A; Zurek, D R; Shara, M M; Marco, Orsola De; Lanz, Thierry; Ouellette, John A.; Zurek, David; Shara, Michael M.

    2004-01-01

    We present an analysis of optical HST/STIS and HST/FOS spectroscopy of 6 blue stragglers found in the globular clusters M3, NGC6752 and NGC6397. These stars are a subsample of a set of ~50 blue stragglers and stars above the main sequence turn-off in four globular clusters which will be presented in an forthcoming paper. All but the 6 stars presented here can be well fitted with non-LTE model atmospheres. The 6 misfits, on the other hand, possess Balmer jumps which are too large for the effective temperatures implied by their Paschen continua. We find that our data for these stars are consistent with models only if we account for extra absorption of stellar Balmer photons by an ionized circumstellar disk. Column densities of HI and CaII are derived as are the the disks' thicknesses. This is the first time that a circumstellar disk is detected around blue stragglers. The presence of magnetically-locked disks attached to the stars has been suggested as a mechanism to lose the large angular momentum imparted by ...

  14. An energetic stellar outburst accompanied by circumstellar light echoes

    CERN Document Server

    Bond, H E; Levay, Z G; Panagia, N; Sparks, W B; Starrfield, S; Wagner, R M; Corradi, R L M; Munari, U; Bond, Howard E.; Henden, Arne; Levay, Zoltan G.; Panagia, Nino; Sparks, William B.; Starrfield, Sumner

    2003-01-01

    Some classes of stars, including supernovae and novae, undergo explosive outbursts that eject stellar material into space. In 2002, the previously unknown variable star V838 Monocerotis brightened suddenly by a factor of about 10^4. Unlike a supernova or nova, V838 Mon did not explosively eject its outer layers; rather, it simply expanded to become a cool supergiant with a moderate-velocity stellar wind. Superluminal light echoes were discovered as light from the outburst propagated into surrounding, pre-existing circumstellar dust. Here we report high-resolution imaging and polarimetry of the light echoes, which allow us to set direct geometric distance limits to the object. At a distance of >6 kpc, V838 Mon at its maximum brightness was temporarily the brightest star in the Milky Way. The presence of the circumstellar dust implies that previous eruptions have occurred, and spectra show it to be a binary system. When combined with the high luminosity and unusual outburst behavior, these characteristics indic...

  15. Transit probability of precessing circumstellar planets in binaries and exomoons

    Science.gov (United States)

    Martin, David. V.

    2017-05-01

    Over two decades of exoplanetology has yielded thousands of discoveries, yet some types of systems are still to be observed. Circumstellar planets around one star in a binary have been found, but not for tight binaries (≲5 au). Additionally, extra-solar moons are yet to be found. This paper motivates finding both types of three-body system by calculating analytic and numerical probabilities for all transit configurations, accounting for any mutual inclination and orbital precession. The precession and relative three-body motion can increase the transit probability to as high as tens of per cent, and make it inherently time-dependent over a precession period as short as 5-10 yr. Circumstellar planets in such tight binaries present a tempting observational challenge: enhanced transit probabilities but with a quasi-periodic signature that may be difficult to identify. This may help explain their present non-detection, or maybe they simply do not exist. Whilst this paper considers binaries of all orientations, it is demonstrated how eclipsing binaries favourably bias the transit probabilities, sometimes to the point of being guaranteed. Transits of exomoons exhibit a similar behaviour under precession, but unfortunately only have one star to transit rather than two.

  16. Photoevaporation and close encounters: how the environment around Cygnus OB2 affects the evolution of protoplanetary disks

    CERN Document Server

    Guarcello, M G; Wright, N J; Albacete-Colombo, J F; Clarke, C; Ercolano, B; Flaccomio, E; Kashyap, V; Micela, G; Naylor, T; Schneider, N; Sciortino, S; Vink, J S

    2016-01-01

    In our Galaxy, star formation occurs in a variety of environments, with a large fraction of stars formed in clusters hosting massive stars. OB stars have an important feedback on the evolution of protoplanetary disks around nearby young stars and likely on the process of planet formation occurring in them. The nearby massive association Cygnus OB2 is an outstanding laboratory to study this feedback. It is the closest massive association to our Sun, and hosts hundreds of massive stars and thousands of low mass members. In this paper, we analyze the spatial variation of the disk fraction in Cygnus OB2 and we study its correlation with the local values of Far and Extreme ultraviolet radiation fields and the local stellar surface density. We present definitive evidence that disks are more rapidly dissipated in the regions of the association characterized by intense local UV field and large stellar density. In particular, the FUV radiation dominates disks dissipation timescales in the proximity (i.e. within 0.5 pc...

  17. Modular neuronal assemblies embodied in a closed-loop environment: towards future integration of brains and machines

    Directory of Open Access Journals (Sweden)

    Jacopo eTessadori

    2012-12-01

    Full Text Available Behaviors, from simple to most complex, require a two-way interaction with the environment and the contribution of different brain areas depending on the orchestrated activation of neuronal assemblies. In this work we present a new hybrid neuro-robotic architecture based on a neural controller bi-directionally connected to a virtual robot implementing a Braitenberg vehicle aimed at avoiding obstacles. The robot is characterized by proximity sensors and wheels, allowing it to navigate into a circular arena with obstacles of different sizes. As neural controller, we used hippocampal cultures dissociated from embryonic rats and kept alive over Micro Electrode Arrays (MEAs for 3-8 weeks. The developed software architecture guarantees a bi-directional exchange of information between the natural and the artificial part by means of simple linear coding/decoding schemes. We used two different kinds of experimental preparation: ‘random’ and ‘modular’ populations. In the second case, the confinement was assured by a PDMS (polydimethylsiloxane mask placed over the surface of the MEA device, thus defining two populations interconnected via specific microchannels. The main results of our study are: (i neuronal cultures can be successfully interfaced to an artificial agent; (ii modular networks show a different dynamics with respect to random culture, both in terms of spontaneous and evoked electrophysiological patterns; (iii the robot performs better if a reinforcement learning paradigm (i.e. a tetanic stimulation delivered to the network following each collision is activated, regardless of the modularity of the culture; (iv the robot controlled by the modular network further enhances its capabilities in avoiding obstacles during the short-term plasticity trial. The developed paradigm offers a new framework for studying, in simplified model systems, neuro-artificial bi-directional interfaces for the development of new strategies for brain

  18. Modular neuronal assemblies embodied in a closed-loop environment: toward future integration of brains and machines.

    Science.gov (United States)

    Tessadori, Jacopo; Bisio, Marta; Martinoia, Sergio; Chiappalone, Michela

    2012-01-01

    Behaviors, from simple to most complex, require a two-way interaction with the environment and the contribution of different brain areas depending on the orchestrated activation of neuronal assemblies. In this work we present a new hybrid neuro-robotic architecture based on a neural controller bi-directionally connected to a virtual robot implementing a Braitenberg vehicle aimed at avoiding obstacles. The robot is characterized by proximity sensors and wheels, allowing it to navigate into a circular arena with obstacles of different sizes. As neural controller, we used hippocampal cultures dissociated from embryonic rats and kept alive over Micro Electrode Arrays (MEAs) for 3-8 weeks. The developed software architecture guarantees a bi-directional exchange of information between the natural and the artificial part by means of simple linear coding/decoding schemes. We used two different kinds of experimental preparation: "random" and "modular" populations. In the second case, the confinement was assured by a polydimethylsiloxane (PDMS) mask placed over the surface of the MEA device, thus defining two populations interconnected via specific microchannels. The main results of our study are: (i) neuronal cultures can be successfully interfaced to an artificial agent; (ii) modular networks show a different dynamics with respect to random culture, both in terms of spontaneous and evoked electrophysiological patterns; (iii) the robot performs better if a reinforcement learning paradigm (i.e., a tetanic stimulation delivered to the network following each collision) is activated, regardless of the modularity of the culture; (iv) the robot controlled by the modular network further enhances its capabilities in avoiding obstacles during the short-term plasticity trial. The developed paradigm offers a new framework for studying, in simplified model systems, neuro-artificial bi-directional interfaces for the development of new strategies for brain-machine interaction.

  19. The effects of circumstellar gas on terrestrial planet formation: Theory and observation

    Science.gov (United States)

    Mandell, Avram M.

    Our understanding of the evolution of circumstellar material from dust and gas to fully-formed planets has taken dramatic steps forward in the last decade, driven by rapid improvements in our ability to study gas- and dust-rich disks around young stars and the discovery of more than 200 extra-solar planetary systems around other stars. In addition, our ability to model the formation of both terrestrial and giant planets has improved significantly due to new computing techniques and the continued exponential increase in computing power. In this dissertation I expand on existing theories of terrestrial planet formation to include systems similar to those currently being detected around nearby stars, and I develop new observational techniques to probe the chemistry of gas-rich circumstellar disks where such planetary systems may be forming. One of the most significant characteristics of observed extrasolar planetary systems is the presence of giant planets located much closer to their parent star than was thought to be possible. The presence of "Hot Jupiters", Jovian-mass planets with very short orbital periods detected around nearby main sequence stars, has been proposed to be primarily due to the inward migration of planets formed in orbits initially much further from the parent star. Close-in giant planets are thought to have formed in the cold outer regions of planetary systems and migrated inward, passing through the orbital parameter space occupied by the terrestrial planets in our own Solar System; the migration of these planets would have profound effects on the evolution of inner terrestrial planets in these systems. I first explore this scenario with numerical simulations showing that a significant fraction of terrestrial planets could survive the migration process; damping forces could then eventually re-circularize the orbits at distances relatively close to their original positions. Calculations suggest that the final orbits of a significant fraction of

  20. Why all stars should possess circumstellar temperature inversions

    Science.gov (United States)

    Scudder, Jack D.

    1992-01-01

    The paper shows that the circumstellar temperature inversions possessed by all stars are the consequence of the 'velocity filtration' process described by Scudder (1992), according to which a stellar envelope is hotter than its underlying layers. The filtration scenario relies on the theoretically predicted and experimentally determined non-Maxwellian velocity distributions of ions and/or electrons in other sampled astrophysical plasmas and the transition region. The most immediate consequence is that the temperature and quasi-neutral plasma density become anticorrelated with increasing radius in a thin transition region, leaving the temperature profile inverted in excess of 10 exp 6 K up into a corona, without depositing a wave of magnetic field energy into the gas above the base of the transition region.

  1. The photochemistry of carbon-rich circumstellar shells

    Science.gov (United States)

    Huggins, P. J.; Glassgold, A. E.

    1982-01-01

    The effect of ambient ultraviolet photons on the chemical structure of carbon-rich, circumstellar envelopes is investigated with a simple formulation of the time-dependent, photochemical rate equations valid for optically thick shells. Molecules injected into the shielded inner envelope are broken down when they reach the outer regions where ambient ultraviolet photons can penetrate. A quantitative description of the abundance variations is obtained for the case of uniform expansion by detailed consideration of the shielding of the radiation by the dust and molecules of the envelope. Representative results are presented to illustrate the role of shielding in defining the extent of molecular envelopes, the formation of C I and C II shells by photodestruction of carbon-bearing molecules, and the development of layered chemical structures from the photobreakup of polyatomic molecules. Photochemistry makes the outer parts of thick, carbon-rich envelopes into complex regions containing radicals, ions, and atoms which are of considerable observational and theoretical interest.

  2. Variable Circumstellar Disks: Prevalence, Timescales, and Physical Mechanisms

    Science.gov (United States)

    Burrow, Anthony; Wisniewski, John P.; Lomax, Jamie R.; Bjorkman, Karen S.; Bjorkman, Jon Eric; Covey, Kevin R.; Gerhartz, Cody; Richardson, Noel; Thao, Pa

    2017-01-01

    Rapidly rotating B-type stars often experience mass ejection that leads to the formation of a circumstellar gas disk, as diagnosed by distinct emission lines present in their spectra. The mass ejection from these stars, known as classical Be stars, sometimes slows or stops, leading to the mass falling back onto the central star and the disk dissipating. The prevalence and time-scale of such disk-loss and disk-replenishment episodes, as well as the underlying physical processes that cause the underlying mass ejection, remain unknown. We are using multi-epoch broad- and narrow-band photometric observations of 12 young open clusters to characterize the prevalence and time-scale of disk-loss and disk-replenishment episodes. We use our observations to gauge which cluster objects exhibit H-alpha emission, which is a primary indicator of Be stars in our clusters. This program is supported by NSF-AST 1411563, 1412110, and 1412135.

  3. Polarization and SEDs from Microlensing of Circumstellar Envelopes

    CERN Document Server

    Ignace, R; Bunker, C

    2008-01-01

    Microlensing surveys have proven to be tremendously fruitful in providing valuable data products for many fields of astrophysics, from eclipse lightcurves for substellar candidates to limb darkening in stellar atmospheres. We report on a program of modeling observables from microlensing of circumstellar envelopes, particularly those of red giant stars that are the most likely to show finite source effects. We will summarize work for how polarization light curves can be used to infer envelope properties and will describe recent modeling of the time dependent spectral energy distributions (SEDs) for microlensing of dusty winds. One of the most exciting developments is the possibility of measuring variable polarization from microlensing in a suitable source using the RINGO polarimeter at La Palma. Also quite interesting is the possibility of probing a dusty wind using IRAC data for a suitable source in the event that Spitzer has a ``warm'' cycle.

  4. Infrared observations of circumstellar ammonia in OH/IR supergiants

    Science.gov (United States)

    Mclaren, R. A.; Betz, A. L.

    1980-01-01

    Ammonia has been detected in the circumstellar envelopes of VY Canis Majoris, VX Sagittarii, and IRC +10420 by means of several absorption lines in the nu-2 vibration-rotation band near 950 kaysers. The line profiles are well resolved (0.2 km/sec resolution) and show the gas being accelerated to terminal expansion velocities near 30 km/sec. The observations reveal a method for determining the position of the central star on VLBI maps of OH maser emission to an accuracy of approximately 0.2 arcsec. A firm lower limit of 2 x 10 to the 15th/sq cm is obtained for the NH3 column density in VY Canis Majoris.

  5. Magnetic field and early evolution of circumstellar disks

    CERN Document Server

    Tsukamoto, Yusuke

    2016-01-01

    The magnetic field plays a central role in the formation and evolution of circumstellar disks. The magnetic field connects the rapidly rotating central region with the outer envelope and extracts angular momentum from the central region during gravitational collapse of the cloud core. This process is known as magnetic braking. Both analytical and multidimensional simulations have shown that disk formation is strongly suppressed by magnetic braking in moderately magnetized cloud cores in the ideal magnetohydrodynamic limit. On the other hand, recent observations have provided growing evidence of a relatively large disk several tens of astronomical units in size existing in some Class 0 young stellar objects. This introduces a serious discrepancy between the theoretical study and observations. Various physical mechanisms have been proposed to solve the problem of catastrophic magnetic braking, such as misalignment between the magnetic field and the rotation axis, turbulence, and non-ideal effect. In this paper,...

  6. The progenitor of SN 2011ja: Clues from circumstellar interaction

    CERN Document Server

    Chakraborti, Sayan; Smith, Randall; Ryder, Stuart; Yadav, Naveen; Sutaria, Firoza; Dwarkadas, Vikram V; Chandra, Poonam; Pooley, David; Roy, Rupak

    2013-01-01

    Massive stars, possibly red supergiants, which retain extended hydrogen envelopes until the time of core collapse produce Type IIP (Plateau) supernovae. The ejecta from these explosions shock the circumstellar matter originating from the mass loss of the progenitor during the final phases of its life. This interaction accelerates particles to relativistic energies which then lose energy via synchrotron radiation in the shock-amplified magnetic fields and inverse Compton scattering against optical photons from the supernova. These processes produce different signatures in the radio and X-ray part of the electromagnetic spectrum. Observed together, they allow us to break the degeneracy between shock acceleration and magnetic field amplification. In this work we use X-rays observations from the Chandra and radio observations from the ATCA to study the relative importance of particle acceleration and magnetic fields in producing the non-thermal radiation from SN 2011ja. We use radio observations to constrain the ...

  7. Extinction Laws toward Stellar Sources within a Dusty Circumstellar Medium and Implications for Type Ia Supernovae

    Science.gov (United States)

    Nagao, Takashi; Maeda, Keiichi; Nozawa, Takaya

    2016-06-01

    Many astronomical objects are surrounded by dusty environments. In such dusty objects, multiple scattering processes of photons by circumstellar (CS) dust grains can effectively alter extinction properties. In this paper, we systematically investigate the effects of multiple scattering on extinction laws for steady-emission sources surrounded by the dusty CS medium using a radiation transfer simulation based on the Monte Carlo technique. In particular, we focus on whether and how the extinction properties are affected by properties of CS dust grains by adopting various dust grain models. We confirm that behaviors of the (effective) extinction laws are highly dependent on the properties of CS grains, especially the total-to-selective extinction ratio R V , which characterizes the extinction law and can be either increased or decreased and compared with the case without multiple scattering. We find that the criterion for this behavior is given by a ratio of albedos in the B and V bands. We also find that either small silicate grains or polycyclic aromatic hydrocarbons are necessary for realizing a low value of R V as often measured toward SNe Ia if the multiple scattering by CS dust is responsible for their non-standard extinction laws. Using the derived relations between the properties of dust grains and the resulting effective extinction laws, we propose that the extinction laws toward dusty objects could be used to constrain the properties of dust grains in CS environments.

  8. Stellar and circumstellar properties of visual binaries in the Orion Nebula Cluster

    CERN Document Server

    Correia, S; Reipurth, B; Zinnecker, H; Daemgen, S; Petr-Gotzens, M G; Koehler, R; Ratzka, Th; Aspin, C; Konopacky, Q M; Ghez, A M

    2013-01-01

    Our general understanding of multiple star and planet formation is primarily based on observations of young multiple systems in low density regions like Tau-Aur and Oph. Since many, if not most, of the stars are born in clusters, observational constraints from young binaries in those environments are fundamental for understanding both the formation of multiple systems and planets in multiple systems throughout the Galaxy. We build upon the largest survey for young binaries in the Orion Nebula Cluster (ONC) which is based on Hubble Space Telescope observations to derive both stellar and circumstellar properties of newborn binary systems in this cluster environment. We present Adaptive Optics spatially-resolved JHKL'-band photometry and K-band R$\\sim$\\,5000 spectra for a sample of 8 ONC binary systems from this database. We characterize the stellar properties of binary components and obtain a census of protoplanetary disks through K-L' color excess. For a combined sample of ONC binaries including 7 additional s...

  9. Observational constraints for the circumstellar disk of the B[e] star CPD-52 9243

    Science.gov (United States)

    Cidale, L. S.; Borges Fernandes, M.; Andruchow, I.; Arias, M. L.; Kraus, M.; Chesneau, O.; Kanaan, S.; Curé, M.; de Wit, W. J.; Muratore, M. F.

    2012-12-01

    Context. The formation and evolution of gas and dust environments around B[e] supergiants are still open issues. Aims: We intend to study the geometry, kinematics and physical structure of the circumstellar environment (CE) of the B[e] supergiant CPD-52 9243 to provide further insights into the underlying mechanism causing the B[e] phenomenon. Methods: The influence of the different physical mechanisms acting on the CE (radiation pressure, rotation, bi-stability or tidal forces) is somehow reflected in the shape and kinematic properties of the gas and dust regions (flaring, Keplerian, accretion or outflowing disks). To investigate these processes we mainly used quasi-simultaneous observations taken with high spatial resolution optical long-baseline interferometry (VLTI/MIDI), near-IR spectroscopy of CO bandhead features (Gemini/Phoenix and VLT/CRIRES) and optical spectra (CASLEO/REOSC). Results: High angular resolution interferometric measurements obtained with VLTI/MIDI provide strong support for the presence of a dusty disk(ring)-like structure around CPD-52 9243, with an upper limit for its inner edge of ~8 mas (~27.5 AU, considering a distance of 3.44 kpc to the star). The disk has an inclination angle with respect to the line of sight of 46 ± 7°. The study of CO first overtone bandhead evidences a disk structure in Keplerian rotation. The optical spectrum indicates a rapid outflow in the polar direction. Conclusions: The IR emission (CO and warm dust) indicates Keplerian rotation in a circumstellar disk while the optical line transitions of various species are consistent with a polar wind. Both structures appear simultaneously and provide further evidence for the proposed paradigms of the mass-loss in supergiant B[e] stars. The presence of a detached cold CO ring around CPD-52 9243 could be due to a truncation of the inner disk caused by a companion, located possibly interior to the disk rim, clearing the center of the system. More spectroscopic and

  10. Vertical settling and radial segregation of large dust grains in the circumstellar disk of the Butterfly Star

    CERN Document Server

    Gräfe, Christian; Guilloteau, Stephane; Dutrey, Anne; Stapelfeldt, Karl; Pontoppidan, Klaus; Sauter, Jürgen

    2013-01-01

    Context: Circumstellar disks are considered to be the environment for the formation of planets. The growth of dust grains in these disks is the first step in the core accretion-gas capture planet formation scenario. Indicators and evidence of disk evolution can be traced in spatially resolved images and the spectral energy distribution (SED) of these objects. Aims: We develop a model for the dust phase of the edge-on oriented circumstellar disk of the Butterfly Star which allows one to fit observed multi-wavelength images and the SED simultaneously. Methods: Our model is based on spatially resolved high angular resolution observations at 1.3 mm, 894 micron, 2.07 micron, 1.87 micron, 1.60 micron, and 1.13 micron and an extensively covered SED ranging from 12 micron to 2.7 mm, including a detailed spectrum obtained with the Spitzer Space Telescope in the range from 12 micron to 38 micron. A parameter study based on a grid search method involving the detailed analysis of every parameter was performed to constrai...

  11. The impact of secular resonances on habitable zones in circumstellar planetary systems of known binary stars

    CERN Document Server

    Bazsó, Ákos; Eggl, Siegfried; Funk, Barbara; Bancelin, David

    2016-01-01

    We present a survey on binary star systems with stellar separations less than 100 astronomical units. For a selection of 11 binaries with a detected (giant) planet in circumstellar motion we determine the conditions that would allow additional planets to be present inside or nearby the habitable zone (HZ) of the host star. First we calculate the three-body HZ for these systems, in order to investigate the dynamics of bodies in those regions. After adding the giant planet's influence the final HZ is considerably modified in particular by mean motion and secular resonances. We apply a semi-analytical method to determine the locations of linear secular resonances, which is based on finding the apsidal precession frequencies of the massive bodies. For very close-in giant planets we also take the general relativistic precession of the pericenter into account. Our results demonstrate that there is a qualitative difference in the dynamics whether the giant planet is located exterior or interior to the HZ. An exterio...

  12. Dynamics of Circumstellar Disks III: The case of GG Tau A

    CERN Document Server

    Nelson, Andrew F

    2016-01-01

    (abridged) We present 2-dimensional hydrodynamic simulations using the Smoothed Particle Hydrodynamic (SPH) code, VINE, to model a self-gravitating binary system similar to the GG Tau A system. We simulate systems configured with semi-major axes of either $a=62$~AU (`wide') or $a=32$~AU (`close'), and with eccentricity of either $e=0$ or $e=0.3$. Strong spiral structures are generated with large material streams extending inwards. A small fraction accretes onto the circumstellar disks, with most returning to the torus. Structures also propagate outwards, generating net outwards mass flow and eventually losing coherence at large distances. The torus becomes significantly eccentric in shape. Accretion onto the stars occurs at a rate of a few $\\times10^{-8}$\\msun/yr implying disk lifetimes shorter than $\\sim10^4$~yr, without replenishment. Only wide configurations retain disks by virtue of robust accretion. In eccentric configurations, accretion is episodic, occurs preferentially onto the secondary at wrates pea...

  13. The Nature of Transition Circumstellar Disks I. The Ophiuchus Molecular Cloud

    CERN Document Server

    Cieza, Lucas A; Romero, Gisela A; Mora, Marcelo D; Merin, Bruno; Swift, Jonathan J; Orellana, Mariana; Williams, Jonathan P; Harvey, Paul M; Evans, Neal J

    2010-01-01

    We have obtained millimeter wavelength photometry, high-resolution optical spectroscopy and adaptive optics near-infrared imaging for a sample of 26 Spitzer-selected transition circumstellar disks. All of our targets are located in the Ophiuchus molecular cloud (d ~125 pc) and have Spectral Energy Distributions (SEDs) suggesting the presence of inner opacity holes. We use these ground-based data to estimate the disk mass, multiplicity, and accretion rate for each object in our sample in order to investigate the mechanisms potentially responsible for their inner holes. We find that transition disks are a heterogeneous group of objects, with disk masses ranging from < 0.6 to 40 M_JUP and accretion rates ranging from <1E-11 1E-7 M_solar/yr, but most tend to have much lower masses and accretion rates than "full disks" (i.e., disks without opacity holes). Eight of our targets have stellar companions: 6 of them are binaries and the other 2 are triple systems. In four cases, the stellar companions are close en...

  14. TW Hya Association Membership and New WISE-detected Circumstellar Disks

    CERN Document Server

    Schneider, Adam; Song, Inseok

    2012-01-01

    We assess the current membership of the nearby, young TW Hydrae Association and examine newly proposed members with the Wide-field Infrared Survey Explorer (WISE) to search for infrared excess indicative of circumstellar disks. Newly proposed members TWA 30A, TWA 30B, TWA 31, and TWA 32 all show excess emission at 12 and 22 \\mum providing clear evidence for substantial dusty circumstellar disks around these low-mass, ~8 Myr old stars that were previously shown to likely be accreting from circumstellar material. TWA 30B shows large amounts of self-extinction, likely due to an edge-on disk geometry. We also confirm previously reported circumstellar disks with WISE, and determine a 22 \\mum excess fraction of 42+/- 9% based on our results.

  15. X-RAY EMISSION FROM STRONGLY ASYMMETRIC CIRCUMSTELLAR MATERIAL IN THE REMNANT OF KEPLER'S SUPERNOVA

    Energy Technology Data Exchange (ETDEWEB)

    Burkey, Mary T.; Reynolds, Stephen P.; Borkowski, Kazimierz J.; Blondin, John M., E-mail: reynolds@ncsu.edu [Department of Physics, North Carolina State University, Raleigh NC 27695-8202 (United States)

    2013-02-10

    Kepler's supernova remnant resulted from a thermonuclear explosion, but is interacting with circumstellar material (CSM) lost from the progenitor system. We describe a statistical technique for isolating X-ray emission due to CSM from that due to shocked ejecta. Shocked CSM coincides well in position with 24 {mu}m emission seen by Spitzer. We find most CSM to be distributed along the bright north rim, but substantial concentrations are also found projected against the center of the remnant, roughly along a diameter with position angle {approx}100 Degree-Sign . We interpret this as evidence for a disk distribution of CSM before the supernova, with the line of sight to the observer roughly in the disk plane. We present two-dimensional hydrodynamic simulations of this scenario in qualitative agreement with the observed CSM morphology. Our observations require Kepler to have originated in a close binary system with an asymptotic giant branch star companion.

  16. EVIDENCE FOR ASYMMETRIC DISTRIBUTION OF CIRCUMSTELLAR MATERIAL AROUND TYPE Ia SUPERNOVAE

    Energy Technology Data Exchange (ETDEWEB)

    Foerster, Francisco; Gonzalez-Gaitan, Santiago; Anderson, Joseph; Marchi, Sebastian; Gutierrez, Claudia; Hamuy, Mario; Cartier, Regis [Departamento de Astronomia, Universidad de Chile, Casilla 36-D, Santiago (Chile); Pignata, Giuliano [Departamento Ciencias Fisicas, Universidad Andres Bello, Av. Republica 252, Santiago (Chile)

    2012-08-01

    We study the properties of low-velocity material in the line of sight toward nearby Type Ia supernovae (SNe Ia) that have measured late phase nebular velocity shifts (v{sub neb}), thought to be an environment-independent observable. We have found that the distribution of equivalent widths of narrow blended Na I D1 and D2 and Ca II H and K absorption lines differs significantly between those SNe Ia with negative and positive v{sub neb}, with generally stronger absorption for SNe Ia with v{sub neb} {>=} 0. A similar result had been found previously for the distribution of colors of SNe Ia, which was interpreted as a dependence of the temperature of the ejecta with viewing angle. Our work suggests that (1) a significant part of these differences in color should be attributed to extinction, (2) this extinction is caused by an asymmetric distribution of circumstellar material (CSM), and (3) the CSM absorption is generally stronger on the side of the ejecta opposite to where the ignition occurs. Since it is difficult to explain (3) via any known physical processes that occur before explosion, we argue that the asymmetry of the CSM is originated after explosion by a stronger ionizing flux on the side of the ejecta where ignition occurs, probably due to a stronger shock breakout and/or more exposed radioactive material on one side of the ejecta. This result has important implications for both progenitor and explosion models.

  17. Synthetic Spectra and Light Curves of Interacting Binaries and Exoplanets with Circumstellar Material: SHELLSPEC

    CERN Document Server

    Budaj, Jan

    2011-01-01

    Program SHELLSPEC is designed to calculate light-curves, spectra and images of interacting binaries and extrasolar planets immersed in a moving circumstellar environment which is optically thin. It solves simple radiative transfer along the line of sight in moving media. The assumptions include LTE and optional known state quantities and velocity fields in 3D. Optional (non)transparent objects such as a spot, disc, stream, jet, ufo, shell or stars may be defined (embedded) in 3D and their composite synthetic spectrum calculated. Roche model can be used as a boundary condition for the radiative transfer. Recently a new model of the reflection effect, dust and Mie scattering were incorporated into the code. $\\epsilon$ Aurigae is one of the most mysterious objects on the sky. Prior modeling of its light-curve assumed dark, inclined, disk of dust with the central hole to explain the light-curve with a sharp mid-eclipse brightening. Our model consists of two geometrically thick flared disks. Internal optically thi...

  18. Circumstellar Habitable Zones of Binary Star Systems in the Solar Neighborhood

    CERN Document Server

    Eggl, Siegfried; Funk, Barbara; Georgakarakos, Nikolaos; Haghighipour, Nader

    2012-01-01

    Binary and multiple systems constitute more than half of the total stellar population in the Solar neighborhood (Kiseleva-Eggleton and Eggleton 2001). Their frequent occurrence as well as the fact that more than 70 (Schneider et al. 2011) planets have already been discovered in such configurations - most noteably the telluric companion of alpha Centauri B (Dumusque et al. 2012) - make them interesting targets in the search for habitable worlds. Recent studies (Eggl et al. 2012b, Forgan 2012) have shown, that despite the variations in gravitational and radiative environment, there are indeed circumstellar regions where planets can stay within habitable insolation limits on secular dynamical timescales. In this article we provide habitable zones for 19 near S-Type binary systems from the Hipparchos and WDS catalogues with semimajor axes between 1 and 100 AU. Hereby, we accounted for the combined dynamical and radiative influence of the second star on the Earth-like planet. Out of the 19 systems presented, 17 of...

  19. The inner circumstellar disk of the UX Ori star V1026 Sco

    CERN Document Server

    Vural, J; Kishimoto, M; Weigelt, G; Hofmann, K -H; Kraus, S; Schertl, D; Dugué, M; Duvert, G; Lagarde, S; Massi, F

    2014-01-01

    The UX Ori type variables (named after the prototype of their class) are intermediate-mass pre-main sequence objects. One of the most likely causes of their variability is the obscuration of the central star by orbiting dust clouds. We investigate the structure of the circumstellar environment of the UX~Ori star V1026 Sco (HD 142666) and test whether the disk inclination is large enough to explain the UX Ori variability. We observed the object in the low-resolution mode of the near-infrared interferometric VLTI/AMBER instrument and derived H- and K-band visibilities and closure phases. We modeled our AMBER observations, published Keck Interferometer observations, archival MIDI/VLTI visibilities, and the spectral energy distribution using geometric and temperature-gradient models. Employing a geometric inclined-ring disk model, we find a ring radius of 0.15 +- 0.06 AU in the H band and 0.18 +- 0.06 AU in the K band. The best-fit temperature-gradient model consists of a star and two concentric, ring-shaped disk...

  20. LABORATORY INVESTIGATIONS OF POLYCYCLIC AROMATIC HYDROCARBON FORMATION AND DESTRUCTION IN THE CIRCUMSTELLAR OUTFLOWS OF CARBON STARS

    Energy Technology Data Exchange (ETDEWEB)

    Contreras, Cesar S.; Salama, Farid, E-mail: cesar.contreras@nasa.gov, E-mail: Farid.Salama@nasa.gov [Space Science and Astrobiology Division, NASA-Ames Research Center, Moffett Field, CA 94035 (United States)

    2013-09-15

    The formation and destruction mechanisms of interstellar dust analogs formed from a variety of polycyclic aromatic hydrocarbon (PAH) and hydrocarbon molecular precursors are studied in the laboratory. We used the newly developed facility COSmIC, which simulates interstellar and circumstellar environments, to investigate both PAHs and species that include the cosmically abundant atoms O, N, and S. The species generated in a discharge plasma are detected, monitored, and characterized in situ using highly sensitive techniques that provide both spectral and ion mass information. We report here the first series of measurements obtained in these experiments which focus on the characterization of the most efficient molecular precursors in the chemical pathways that eventually lead to the formation of carbonaceous grains in the stellar envelopes of carbon stars. We compare and discuss the relative efficiencies of the various molecular precursors that lead to the formation of the building blocks of carbon grains. We discuss the most probable molecular precursors in terms of size and structure and the implications for the expected growth and destruction processes of interstellar carbonaceous dust.

  1. Chemical composition of the circumstellar disk around AB Aurigae

    CERN Document Server

    Pacheco-Vázquez, S; Agúndez, M; Pinte, C; Alonso-Albi, T; Neri, R; Cernicharo, J; Goicoechea, J R; Berné, O; Wiesenfeld, L; Bachiller, R; Lefloch, B

    2015-01-01

    Aims. Our goal is to determine the molecular composition of the circumstellar disk around AB Aurigae (hereafter, AB Aur). AB Aur is a prototypical Herbig Ae star and the understanding of its disk chemistry is of paramount importance to understand the chemical evolution of the gas in warm disks. Methods. We used the IRAM 30-m telescope to perform a sensitive search for molecular lines in AB Aur as part of the IRAM Large program ASAI (A Chemical Survey of Sun-like Star-forming Regions). These data were complemented with interferometric observations of the HCO+ 1-0 and C17O 1-0 lines using the IRAM Plateau de Bure Interferometer (PdBI). Single-dish and interferometric data were used to constrain chemical models. Results. Throughout the survey, several lines of CO and its isotopologues, HCO+, H2CO, HCN, CN and CS, were detected. In addition, we detected the SO 54-33 and 56-45 lines, confirming the previous tentative detection. Comparing to other T Tauri's and Herbig Ae disks, AB Aur presents low HCN 3-2/HCO+ 3-2 ...

  2. Observation of Circumstellar Gas in the Neighborhood of RZ Psc

    Science.gov (United States)

    Potravnov, I. S.; Grinin, V. P.; Ilyin, I. V.

    2013-12-01

    The first evidence is found of the existence of circumstellar gas in the nearest surroundings of the UX Ori star RZ Psc. Spectra obtained at the Terskol Observatory, Special Astrophysical Observatory (SAO), and the Nordic Optical Telescope (NOT) reveal a strong variability in the sodium doublet lines that is indicative of a sporadic outflow of matter. Weak variability was also observed in the core of the Hα line. One nontrivial feature of this discovery is that RZ Psc is of spectral class K0 IV. This means that the star has no intrinsic energy resources for creating the observed outflow of matter. There are no emission lines in the star's spectrum which might indicate that matter is falling into the star so that the observed outflow could be related to an accretion process. We suggest, nevertheless, that the ejection of gas is related to residual (slow) accretion and is driven by a propeller mechanism. The latter is possible if the star has a sufficiently high (on the order of 103 G) magnetic field.

  3. Unifying Type II Supernova Light Curves with Dense Circumstellar Material

    CERN Document Server

    Morozova, Viktoriya; Valenti, Stefano

    2016-01-01

    A longstanding problem in the study of supernovae (SNe) has been the relationship between the Type IIP and Type IIL subclasses. Whether they come from distinct progenitors or they are from similar stars with some property that smoothly transitions from one class to another has been the subject of much debate. Here we show using one-dimensional radiation-hydrodynamic SN models that the multi-band light curves of SNe IIL are well fit by ordinary red supergiants surrounded by dense circumstellar material (CSM). The inferred extent of this material, coupled with a typical wind velocity of ~10-100 km/s, suggests enhanced activity by these stars during the last ~months to ~years of their lives, which may be connected with advanced stages of nuclear burning. Furthermore, we find that even for more plateau-like SNe that dense CSM provides a better fit to the first ~20 days of their light curves, indicating that the presence of such material may be more widespread than previously appreciated. Here we choose to model t...

  4. Cepheids at high angular resolution: circumstellar envelope and pulsation

    CERN Document Server

    Gallenne, Alexandre

    2011-01-01

    In 2005, interferometric observations with VLTI/VINCI and CHARA/FLUOR revealed the existence of a circumstellar envelope (CSE) around some Cepheids. This surrounding material is particularly interesting for two reasons: it could have an impact on the distance estimates and could be linked to a past or on-going mass loss. The use of Baade-Wesselink methods for independent distance determinations could be significantly biased by the presence of these envelopes. Although their observations are difficult because of the high contrast between the photosphere of the star and the CSE, several observation techniques have the potential to improve our knowledge about their physical properties. In this thesis, I discuss in particular high angular resolution techniques that I applied to the study of several bright Galactic Cepheids. First, I used adaptive optic observations with NACO of the Cepheid RS Puppis, in order to deduce the flux ratio between the CSE and the photosphere of the star. In addition, I could carry out ...

  5. The ionization structure of the circumstellar envelope of Alpha Orionis

    Science.gov (United States)

    Glassgold, A. E.; Huggins, P. J.

    1986-01-01

    The physical processes which affect the ionization of the outer circumstellar envelope of Alpha Ori are analyzed and evaluated. The ultraviolet radiation fields of the chromosphere and the interstellar medium dominate the envelope, and the most common forms of all species are neutral atoms and first ions. Hydrogen recombines just outside the chromosphere, where atoms with smaller ionization potential are essentially fully ionized. The heavier ions gradually recombine with increasing distance from the star, until the interstellar radiation field reverses this trend. The electron fraction in the outer envelope is approximately equal to the abundance of all such heavy atoms, i.e., of the order of 0.0001. The analysis is applied to the case of neutral K, whose density in the envelope has been determined by scattering experiments. The theory predicts that the slope of the K I density distribution should decrease from -1.5 to -3.5 in the outer envelope. The mass loss rate of Alpha Ori implied by the K I scattering experiments is 4 x 10 to the -6th solar mass/yr.

  6. Evolution of Gas and Dust in Circumstellar Disks

    CERN Document Server

    Körner, D W

    1999-01-01

    A clear understanding of the chemical processing of matter, as it is transferred from a molecular cloud to a planetary system, depends heavily on knowledge of the physical conditions endured by gas and dust as these accrete onto a disk and are incorporated into planetary bodies. Reviewed here are astrophysical observations of circumstellar disks which trace their evolving properties. Accretion disks that are massive enough to produce a solar system like our own are typically larger than 100 AU. This suggests that the chemistry of a large fraction of the infalling material is not radically altered upon contact with a vigorous accretion shock. The mechanisms of accretion onto the star and eventual dispersal are not yet well understood, but timescales for the removal of gas and optically thick dust appear to be a few times 10$^6$ yrs. At later times, tenuous ``debris disks'' of dust remain around stars as old as a few times 10$^8$ yrs. Features in the morphology of the latter, such as inner holes, warps, and azi...

  7. ALMA Observations of HD141569's Circumstellar Disk

    CERN Document Server

    White, J A; Hughes, A M; Flaherty, K M; Ford, E; Wilner, D; Corder, S; Payne, M

    2016-01-01

    We present ALMA band 7 (345 GHz) continuum and $^{12}$CO(J = 3-2) observations of the circumstellar disk surrounding HD141569. At an age of about 5 Myr, the disk has a complex morphology that may be best interpreted as a nascent debris system with gas. Our $870\\rm~\\mu m$ ALMA continuum observations resolve a dust disk out to approximately $ 56 ~\\rm au$ from the star (assuming a distance of 116 pc) with $0."38$ resolution and $0.07 ~ \\rm mJy~beam^{-1}$ sensitivity. We measure a continuum flux density for this inner material of $3.8 \\pm 0.4 ~ \\rm mJy$ (including calibration uncertainties). The $^{12}$CO(3-2) gas is resolved kinematically and spatially from about 30 to 210 au. The integrated $^{12}$CO(3-2) line flux density is $15.7 \\pm 1.6~\\rm Jy~km~s^{-1}$. We estimate the mass of the millimeter debris and $^{12}$CO(3-2) gas to be $\\gtrsim0.04~\\rm M_{\\oplus}$ and $\\sim2\\times 10^{-3}~\\rm M_{\\oplus}$, respectively. If the millimeter grains are part of a collisional cascade, then we infer that the inner disk ($&...

  8. The Structure of the DoAr 25 Circumstellar Disk

    CERN Document Server

    Andrews, Sean M; Wilner, D J; Qi, Chunhua

    2008-01-01

    We present high spatial resolution (< 0.3" = 40$ AU) Submillimeter Array observations of the 865 micron continuum emission from the circumstellar disk around the young star DoAr 25. Despite its bright millimeter emission, this source exhibits only a comparatively small infrared excess and low accretion rate, suggesting that the material and structural properties of the inner disk may be in an advanced state of evolution. A simple model of the physical conditions in the disk is derived from the submillimeter visibilities and the complete spectral energy distribution using a Monte Carlo radiative transfer code. For the standard assumption of a homogeneous grain size distribution at all disk radii, the results indicate a shallow surface density profile, $\\Sigma \\propto r^{-p}$ with p = 0.34, significantly less steep than a steady-state accretion disk (p = 1) or the often adopted minimum mass solar nebula (p = 1.5). Even though the total mass of material is large (M_d = 0.10 M_sun), the densities inferred in t...

  9. Circumstellar Dust Created by Terrestrial Planet Formation in HD 113766

    CERN Document Server

    Lisse, C M; Wyatt, M C; Morlok, A

    2007-01-01

    We present an analysis of the gas-poor circumstellar material in the HD 113766 binary system (F3/F5, 10 - 16 Myr), recently observed by the Spitzer Space Telescope. For our study we have used the infrared mineralogical model derived from observations of the Deep Impact experiment. We find the dust dominated by warm, fine (~1 um) particles, abundant in Mg-rich olivine, crystalline pyroxenes, amorphous silicates, Fe-rich sulfides, amorphous carbon, and colder water-ice. The warm dust material mix is akin to an inner main belt asteroid of S-type composition. The ~440 K effective temperature of the warm dust implies that the bulk of the observed material is in a narrow belt ~1.8 AU from the 4.4 L_solar central source, in the terrestrial planet-forming region and habitable zone of the system (equivalent to 0.9 AU in the solar system). The icy dust lies in 2 belts, located at 4-9 AU and at 30 - 80 AU. The lower bound of warm dust mass in 0.1 - 20 um, dn/da ~ a^-3.5 particles is very large, at least 3 x 10^20 kg, eq...

  10. Type Ia Supernovae Strongly Interacting with Their Circumstellar Medium

    CERN Document Server

    Silverman, Jeffrey M; Gal-Yam, Avishay; Sullivan, Mark; Howell, D Andrew; Filippenko, Alexei V; Arcavi, Iair; Ben-Ami, Sagi; Bloom, Joshua S; Cenko, S Bradley; Cao, Yi; Chornock, Ryan; Clubb, Kelsey I; Coil, Alison L; Foley, Ryan J; Graham, Melissa L; Griffith, Christopher V; Horesh, Assaf; Kasliwal, Mansi M; Kulkarni, Shrinivas R; Leonard, Douglas C; Li, Weidong; Matheson, Thomas; Miller, Adam A; Modjaz, Maryam; Ofek, Eran O; Pan, Yen-Chen; Perley, Daniel A; Poznanski, Dovi; Quimby, Robert M; Steele, Thea N; Sternberg, Assaf; Xu, Dong; Yaron, Ofer

    2013-01-01

    Owing to their utility for measurements of cosmic acceleration, Type Ia supernovae (SNe) are perhaps the best-studied class of SNe, yet the progenitor systems of these explosions largely remain a mystery. A rare subclass of SNe Ia show evidence of strong interaction with their circumstellar medium (CSM), and in particular, a hydrogen-rich CSM; we refer to them as SNe Ia-CSM. In the first systematic search for such systems, we have identified 16 SNe Ia-CSM, and here we present new spectra of 13 of them. Six SNe Ia-CSM have been well-studied previously, three were previously known but are analyzed in-depth for the first time here, and seven are new discoveries from the Palomar Transient Factory. The spectra of all SNe Ia-CSM are dominated by H{\\alpha} emission (with widths of ~2000 km/s) and exhibit large H{\\alpha}/H{\\beta} intensity ratios (perhaps due to collisional excitation of hydrogen via the SN ejecta overtaking slower-moving CSM shells); moreover, they have an almost complete lack of He I emission. They...

  11. A WISE survey of circumstellar disks in Taurus

    Energy Technology Data Exchange (ETDEWEB)

    Esplin, T. L.; Luhman, K. L. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Mamajek, E. E., E-mail: taran.esplin@psu.edu [Department of Physics and Astronomy, The University of Rochester, Rochester, NY 14627 (United States)

    2014-04-01

    We have compiled photometry at 3.4, 4.6, 12, and 22 μm from the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) for all known members of the Taurus complex of dark clouds. Using these data and photometry from the Spitzer Space Telescope, we have identified members with infrared excess emission from circumstellar disks and have estimated the evolutionary stages of the detected disks, which include 31 new full disks and 16 new candidate transitional, evolved, evolved transitional, and debris disks. We have also used the WISE All-Sky Source Catalog to search for new disk-bearing members of Taurus based on their red infrared colors. Through optical and near-infrared spectroscopy, we have confirmed 26 new members with spectral types of M1-M7. The census of disk-bearing stars in Taurus should now be largely complete for spectral types earlier than ∼M8 (M ≳ 0.03 M {sub ☉}).

  12. Dust Migration and Morphology in Optically Thin Circumstellar Gas Disks

    CERN Document Server

    Takeuchi, T; Takeuchi, Taku; Artymowicz, Pawel

    2001-01-01

    We analyze the dynamics of gas-dust coupling in the presence of stellar radiation pressure in circumstellar gas disks, which are in a transitional stage between the gas-dominated, optically thick, primordial nebulae, and the dust-dominated, optically thin Vega-type disks. Dust undergo radial migration, seeking a stable equilibrium orbit in corotation with gas. The migration of dust gives rise to radial fractionation of dust and creates a variety of possible observed disk morphologies, which we compute by considering the equilibrium between the dust production and the dust-dust collisions removing particles from their equilibrium orbits. Sand-sized and larger grains are distributed throughout most of the gas disk, with concentration near the gas pressure maximum in the inner disk. Smaller grains (typically in the range of 10 to 200 micron) concentrate in a prominent ring structure in the outer region of the gas disk (presumably at radius 100 AU), where gas density is rapidly declining with radius. The width an...

  13. Rapid disappearance of a warm, dusty circumstellar disk

    CERN Document Server

    Melis, Carl; Rhee, Joseph H; Song, Inseok; Murphy, Simon J; Bessell, Michael S

    2012-01-01

    Stars form with gaseous and dusty circumstellar envelopes, which rapidly settle into disks that eventually give rise to planetary systems. Understanding the process by which these disks evolve is paramount in developing an accurate theory of planet formation that can account for the variety of planetary systems discovered so far. The formation of Earth-like planets through collisional accumulation of rocky objects within a disk has mainly been explored in theoretical and computational work in which post-collision ejecta evolution is typically ignored, although recent work has considered the fate of such material. Here we report observations of a young, Sun-like star (TYC 8241 2652 1) where infrared flux from post-collisional ejecta has decreased drastically, by a factor of about 30, over a period of less than two years. The star seems to have gone from hosting substantial quantities of dusty ejecta, in a region analogous to where the rocky planets orbit in the Solar System, to retaining at most a meagre amoun...

  14. Rapid disappearance of a warm, dusty circumstellar disk

    Science.gov (United States)

    Melis, Carl; Zuckerman, B.; Rhee, Joseph H.; Song, Inseok; Murphy, Simon J.; Bessell, Michael S.

    2012-07-01

    Stars form with gaseous and dusty circumstellar envelopes, which rapidly settle into disks that eventually give rise to planetary systems. Understanding the process by which these disks evolve is paramount in developing an accurate theory of planet formation that can account for the variety of planetary systems discovered so far. The formation of Earth-like planets through collisional accumulation of rocky objects within a disk has mainly been explored in theoretical and computational work in which post-collision ejecta evolution typically is ignored, although recent work has considered the fate of such material. Here we report observations of a young, Sun-like star (TYC 8241 2652 1) where infrared flux from post-collisional ejecta has decreased drastically, by a factor of about 30, over a period of less than two years. The star seems to have gone from hosting substantial quantities of dusty ejecta, in a region analogous to where the rocky planets orbit in the Solar System, to retaining at most a meagre amount of cooler dust. Such a phase of rapid ejecta evolution has not been previously predicted or observed, and no currently available physical model satisfactorily explains the observations.

  15. Evolution of Cold Circumstellar Dust Around Solar-Type Stars

    CERN Document Server

    Carpenter, J M; Schreyer, K; Launhardt, R; Henning, T; Carpenter, John M.; Wolf, Sebastian; Schreyer, Katharina; Launhardt, Ralf; Henning, Th.

    2004-01-01

    We present submillimeter (CSO 350um) and millimeter (SEST 1.2 mm, OVRO 3 mm) photometry for 125 solar-type stars from the FEPS Spitzer Legacy program that have masses between ~0.5 and 2.0 Msun and ages from 3 Myr to 3 Gyr. Continuum emission was detected toward four stars with a signal to noise ratio >= 3$: the classical T Tauri stars RX J1842.9-3532, RX J1852.3-3700, and PDS 66 with SEST, and the debris disk system HD 107146 with OVRO. RXJ1842.9-3532 and RXJ1852.3-3700 are located in projection nearby the R CrA molecular cloud with estimated ages of ~10 Myr, while PDS66 is a probable member of the 20 Myr old Lower Centaurus-Crux subgroup of the Sco-Cen OB association. The continuum emission toward these three sources is unresolved at the 24'' SEST resolution and likely originates from circumstellar accretion disks, each with estimated dust masses of ~5x10**-5 Msun. Analysis of the visibility data toward HD107146 (age 80-200 Myr) indicates that the 3 mm continuum emission is centered on the star within the as...

  16. Supplementary Information for ``Rapid planetesimal formation in turbulent circumstellar discs''

    CERN Document Server

    Johansen, Anders; Mac Low, Mordecai-Mark; Klahr, Hubert; Henning, Thomas; Youdin, Andrew

    2007-01-01

    This document contains refereed supplementary information for the paper ``Rapid planetesimal formation in turbulent circumstellar discs''. It contains 15 sections (\\S1.1 -- \\S1.15) that address a number of subjects related to the main paper. We describe in detail the Poisson solver used to find the self-potential of the solid particles, including a linear and a non-linear test problem (\\S1.3). Dissipative collisions remove energy from the motion of the particles by collisional cooling (\\S1.4), an effect that allows gravitational collapse to occur in somewhat less massive discs (\\S1.7). A resolution study of the gravitational collapse of the boulders is presented in \\S1.6. We find that gravitational collapse can occur in progressively less massive discs as the grid resolution is increased, likely due to the decreased smoothing of the particle-mesh self-gravity solver with increasing resolution. In \\S1.10 we show that it is in good agreement with the Goldreich & Ward (1973) stability analysis to form severa...

  17. A multi-objective model for closed-loop supply chain optimization and efficient supplier selection in a competitive environment considering quantity discount policy

    Science.gov (United States)

    Jahangoshai Rezaee, Mustafa; Yousefi, Samuel; Hayati, Jamileh

    2016-11-01

    Supplier selection and allocation of optimal order quantity are two of the most important processes in closed-loop supply chain (CLSC) and reverse logistic (RL). So that providing high quality raw material is considered as a basic requirement for a manufacturer to produce popular products, as well as achieve more market shares. On the other hand, considering the existence of competitive environment, suppliers have to offer customers incentives like discounts and enhance the quality of their products in a competition with other manufacturers. Therefore, in this study, a model is presented for CLSC optimization, efficient supplier selection, as well as orders allocation considering quantity discount policy. It is modeled using multi-objective programming based on the integrated simultaneous data envelopment analysis-Nash bargaining game. In this study, maximizing profit and efficiency and minimizing defective and functions of delivery delay rate are taken into accounts. Beside supplier selection, the suggested model selects refurbishing sites, as well as determining the number of products and parts in each network's sector. The suggested model's solution is carried out using global criteria method. Furthermore, based on related studies, a numerical example is examined to validate it.

  18. Direct thermal imaging of circumstellar discs and exo-planets

    Science.gov (United States)

    Pantin, Eric; Siebenmorgen, Ralf; Cavarroc, Celine; Sterzik, Michael F.

    2008-07-01

    The phase A study of a mid infrared imager and spectrograph for the European Extremely Large Telescope (E-ELT), called METIS, was endorsed in May 2008. Two key science drivers of METIS are: a) direct thermal imaging of exo-planets and b) characterization of circumstellar discs from the early proto-planetary to the late debris phase. Observations in the 10μm atmospheric window (N band) require a contrast ratio between stellar light and emitted photons from the exo-planet or the disc of ~ 105. At shorter wavelengths the contrast between star and reflected light from the planet-disc system exceeds >~ 107 posing technical challenges. By means of end-to-end detailed simulations we demonstrate that the superb spatial resolution of a 42m telescope in combination with stellar light rejection methods such as coronagraphic or differential imaging will allow detections at 10μm for a solar type system down to a star-planet separation of 0.1" and a mass limit for irradiated planets of 1 Jupiter (MJ) mass. In case of self-luminous planets observations are possible further out e.g. at the separation limit of JWST of ~ 0.7", METIS will detect planets >~5MJ. This allows to derive a census of all such exo-planets by means of thermal imaging in a volume limited sample of up to 6pc. In addition, METIS will provide the possibility to study the chemical composition of atmospheres of exo-planets using spectroscopy at moderate spectral resolution (λ/Δλ ~ 100) for the brightest targets. Based on detailed performance and sensitivity estimates, we demonstrate that a mid-infrared instrument on an ELT is perfectly suited to observe gravitationally created structures such as gaps in proto- and post- planetary discs, in a complementary way to space missions (e.g. JWST, SOFIA) and ALMA which can only probe the cold dust emission further out.

  19. Spread of the dust temperature distribution in circumstellar disks

    Science.gov (United States)

    Heese, S.; Wolf, S.; Dutrey, A.; Guilloteau, S.

    2017-07-01

    Context. Accurate temperature calculations for circumstellar disks are particularly important for their chemical evolution. Their temperature distribution is determined by the optical properties of the dust grains, which, among other parameters, depend on their radius. However, in most disk studies, only average optical properties and thus an average temperature is assumed to account for an ensemble of grains with different radii. Aims: We investigate the impact of subdividing the grain radius distribution into multiple sub-intervals on the resulting dust temperature distribution and spectral energy distribution (SED). Methods: The temperature distribution, the relative grain surface below a certain temperature, the freeze-out radius, and the SED were computed for two different scenarios: (1) Radius distribution represented by 16 logarithmically distributed radius intervals, and (2) radius distribution represented by a single grain species with averaged optical properties (reference). Results: Within the considered parameter range, i.e., of grain radii between 5 nm and 1 mm and an optically thin and thick disk with a parameterized density distribution, we obtain the following results: in optically thin disk regions, the temperature spread can be as large as 63% and the relative grain surface below a certain temperature is lower than in the reference disk. With increasing optical depth, the difference in the midplane temperature and the relative grain surface below a certain temperature decreases. Furthermore, below 20 K, this fraction is higher for the reference disk than for the case of multiple grain radii, while it shows the opposite behavior for temperatures above this threshold. The thermal emission in the case of multiple grain radii at short wavelengths is stronger than for the reference disk. The freeze-out radius (snowline) is a function of grain radius, spanning a radial range between the coldest and warmest grain species of 30 AU.

  20. Radionuclide characterization and associated dose from long-lived radionuclides in close-in fallout delivered to the marine environment at Bikini and Enewetak Atoll

    Energy Technology Data Exchange (ETDEWEB)

    Noshkin, V. E.; Robison, W. L.

    1998-09-01

    Between June 1946 and October 1958, Enewetak and Bikini Atolls were used by the United States as testing grounds for 66 nuclear devices. The combined explosive yield from these tests was 107 Mt (Mt TNT equivalents). This testing produced close-in fallout debris that was contaminated with quantities of radioactive fission and particle activated products, and unspent radioactive nuclear fuel that entered the aquatic environment of the atolls. Today, the sediments in the lagoons are reservoirs for 10's of TBq of the transuranics and some long-lived fission and activation products. The larger amounts of contamination are associated with fine and coarse sediment material adjacent to the locations of the high yield explosions. Radionuclides are also distributed vertically in the sediment column to various depths in all regions of the lagoons. Concentrations greater than fallout background levels are found in filtered water sampled over several decades from all locations and depths in the lagoons. This is a direct indication that the radionuclides are continuously mobilized to solution from the solid phases. Of particular importance is the fact that the long-lived radionuclides are accumulated to different levels by indigenous aquatic plants and organisms that are used as food by resident people. One might anticipate finding continuous high contamination levels in many of the edible marine organisms from the lagoons, since the radionuclides associated with the sediments are not contained and are available to the different organisms in a relatively shallow water environment. This is not the case. We estimate that the radiological dose from consumption of the edible parts of marine foods at Enewetak and Bikini is presently about 0.05% of the total 50-year integral effective dose from all other exposure pathways that include ingestion of terrestrial foods and drinking water, external exposure and inhalation. The total radiological dose from the marine pathway is

  1. Radionuclide characterization and associated dose from long-lived radionuclides in close-in fallout delivered to the marine environment at Bikini and Enewetak Atoll

    Energy Technology Data Exchange (ETDEWEB)

    Noshkin, V. E.; Robison, W. L.

    1998-09-01

    Between June 1946 and October 1958, Enewetak and Bikini Atolls were used by the United States as testing grounds for 66 nuclear devices. The combined explosive yield from these tests was 107 Mt (Mt TNT equivalents). This testing produced close-in fallout debris that was contaminated with quantities of radioactive fission and particle activated products, and unspent radioactive nuclear fuel that entered the aquatic environment of the atolls. Today, the sediments in the lagoons are reservoirs for 10's of TBq of the transuranics and some long-lived fission and activation products. The larger amounts of contamination are associated with fine and coarse sediment material adjacent to the locations of the high yield explosions. Radionuclides are also distributed vertically in the sediment column to various depths in all regions of the lagoons. Concentrations greater than fallout background levels are found in filtered water sampled over several decades from all locations and depths in the lagoons. This is a direct indication that the radionuclides are continuously mobilized to solution from the solid phases. Of particular importance is the fact that the long-lived radionuclides are accumulated to different levels by indigenous aquatic plants and organisms that are used as food by resident people. One might anticipate finding continuous high contamination levels in many of the edible marine organisms from the lagoons, since the radionuclides associated with the sediments are not contained and are available to the different organisms in a relatively shallow water environment. This is not the case. We estimate that the radiological dose from consumption of the edible parts of marine foods at Enewetak and Bikini is presently about 0.05% of the total 50-year integral effective dose from all other exposure pathways that include ingestion of terrestrial foods and drinking water, external exposure and inhalation. The total radiological dose from the marine pathway is

  2. ULTRAVIOLET SPECTROSCOPY OF TYPE IIB SUPERNOVAE: DIVERSITY AND THE IMPACT OF CIRCUMSTELLAR MATERIAL

    Energy Technology Data Exchange (ETDEWEB)

    Ben-Ami, Sagi [Smithsonian Astrophysical Observatory, Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Hachinger, Stephan; Mazzali, Paolo A. [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching (Germany); Gal-Yam, Avishay; Horesh, Assaf; Yaron, Ofer [Department of Particle Physics and Astrophysics, The Weizmann Institute of Science, Rehovot 76100 (Israel); Filippenko, Alexei V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Matheson, Thomas [National Optical Astronomy Observatory, 950 N. Cherry Avenue, Tucson, AZ 85719 (United States); Modjaz, Maryam [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, Room 529, New York, NY 10003 (United States); Sauer, Daniel N. [Department of Astronomy, Stockholm University, Albanova University Center, SE-106 91 Stockholm (Sweden); Silverman, Jeffrey M. [Department of Astronomy, University of Texas, Austin, TX 78712 (United States); Smith, Nathan, E-mail: sbenami@cfa.harvard.edu [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States)

    2015-04-10

    We present new Hubble Space Telescope (HST) multi-epoch ultraviolet (UV) spectra of the bright Type IIb SN 2013df, and undertake a comprehensive analysis of the set of four SNe IIb for which HST UV spectra are available (SN 1993J, SN 2001ig, SN 2011dh, and SN 2013df). We find strong diversity in both continuum levels and line features among these objects. We use radiative-transfer models that fit the optical part of the spectrum well, and find that in three of these four events we see a UV continuum flux excess, apparently unaffected by line absorption. We hypothesize that this emission originates above the photosphere, and is related to interaction with circumstellar material (CSM) located in close proximity to the SN progenitor. In contrast, the spectra of SN 2001ig are well fit by single-temperature models, display weak continuum and strong reverse-fluorescence features, and are similar to spectra of radioactive {sup 56}Ni-dominated SNe Ia. A comparison of the early shock-cooling components in the observed light curves with the UV continuum levels which we assume trace the strength of CSM interaction suggests that events with slower cooling have stronger CSM emission. The radio emission from events having a prominent UV excess is perhaps consistent with slower blast-wave velocities, as expected if the explosion shock was slowed down by the CSM that is also responsible for the strong UV, but this connection is currently speculative as it is based on only a few events.

  3. Herschel/HIFI⋆ observations of the circumstellar ammonia lines in IRC+10216

    Science.gov (United States)

    Schmidt, M. R.; He, J. H.; Szczerba, R.; Bujarrabal, V.; Alcolea, J.; Cernicharo, J.; Decin, L.; Justtanont, K.; Teyssier, D.; Menten, K. M.; Neufeld, D. A.; Olofsson, H.; Planesas, P.; Marston, A. P.; Sobolev, A. M.; de Koter, A.; Schöier, F. L.

    2016-01-01

    Context A discrepancy exists between the abundance of ammonia (NH3) derived previously for the circumstellar envelope (CSE) of IRC+10216 from far-IR submillimeter rotational lines and that inferred from radio inversion or mid-infrared (MIR) absorption transitions. Aims To address the discrepancy described above, new high-resolution far-infrared (FIR) observations of both ortho- and para-NH3 transitions toward IRC+10216 were obtained with Herschel, with the goal of determining the ammonia abundance and constraining the distribution of NH3 in the envelope of IRC+10216. Methods We used the Heterodyne Instrument for the Far Infrared (HIFI) on board Herschel to observe all rotational transitions up to the J = 3 level (three ortho- and six para-NH3 lines). We conducted non-LTE multilevel radiative transfer modelling, including the effects of near-infrared (NIR) radiative pumping through vibrational transitions. The computed emission line profiles are compared with the new HIFI data, the radio inversion transitions, and the MIR absorption lines in the ν2 band taken from the literature. Results We found that NIR pumping is of key importance for understanding the excitation of rotational levels of NH3. The derived NH3 abundances relative to molecular hydrogen were (2.8 ± 0.5) × 10−8 for ortho-NH3 and (3.2−0.6+0.7)×10−8 for para-NH3, consistent with an ortho/para ratio of 1. These values are in a rough agreement with abundances derived from the inversion transitions, as well as with the total abundance of NH3 inferred from the MIR absorption lines. To explain the observed rotational transitions, ammonia must be formed near to the central star at a radius close to the end of the wind acceleration region, but no larger than about 20 stellar radii (1σ confidence level). PMID:28065983

  4. Water isotopologues in the circumstellar envelopes of M-type AGB stars

    Science.gov (United States)

    Danilovich, T.; Lombaert, R.; Decin, L.; Karakas, A.; Maercker, M.; Olofsson, H.

    2017-06-01

    Aims: In this study we intend to examine rotational emission lines of two isotopologues of water: H217O and H218O. By determining the abundances of these molecules, we aim to use the derived isotopologue - and hence oxygen isotope - ratios to put constraints on the masses of a sample of M-type AGB stars that have not been classified as OH/IR stars. Methods: We have used detailed radiative transfer analysis based on the accelerated lambda iteration method to model the circumstellar molecular line emission of H217O and H218O for IK Tau, R Dor, W Hya, and R Cas. The emission lines used to constrain our models came from Herschel/HIFI and Herschel/PACS observations and are all optically thick, meaning that full radiative transfer analysis is the only viable method of estimating molecular abundance ratios. Results: We find generally low values of the 17O/18O ratio for our sample, ranging from 0.15 to 0.69. This correlates with relatively low initial masses, in the range 1.0 to 1.5 M⊙ for each source, based on stellar evolutionary models. We also find ortho-to-para ratios close to 3, which are expected from warm formation predictions. Conclusions: The 17O/18O ratios found for this sample are at the lower end of the range predicted by stellar evolutionary models, indicating that the sample chosen had relatively low initial masses. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  5. Tidal Truncation of Inclined Circumstellar and Circumbinary Discs in Young Stellar Binaries

    CERN Document Server

    Miranda, Ryan

    2015-01-01

    Recent observations have shown that circumstellar and circumbinary discs in young stellar binaries are often misaligned with respect to the binary orbital plane. We analyze the tidal truncation of such misaligned discs due to torques applied to the disc at the Lindblad resonances from the tidal forcings of the binary. We consider eccentric binaries with arbitrary binary-disc inclination angles. We determine the dependence of the tidal forcing strengths on the binary parameters and show that they are complicated non-monotonic functions of eccentricity and inclination. We adopt a truncation criterion determined by the balance between resonant torque and viscous torque, and use it to calculate the outer radii of circumstellar discs and the inner radii of circumbinary discs. Misaligned circumstellar discs have systematically larger outer radii than aligned discs, and are likely to fill their Roche lobes if inclined by more than $45^\\circ - 90^\\circ$, depending on the binary mass ratio and disc viscosity parameter...

  6. METAMORPHOSIS OF SN 2014C: DELAYED INTERACTION BETWEEN A HYDROGEN POOR CORE-COLLAPSE SUPERNOVA AND A NEARBY CIRCUMSTELLAR SHELL

    Energy Technology Data Exchange (ETDEWEB)

    Milisavljevic, D.; Margutti, R.; Kamble, A.; Patnaude, D. J.; Raymond, J. C.; Challis, P.; Drout, M. R.; Grindlay, J. E.; Kirshner, R. P.; Lunnan, R.; Miller, G. F.; Parrent, J. T.; Sanders, N. E. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, 02138 (United States); Eldridge, J. J. [Department of Physics, University of Auckland, Private Bag 92019, Auckland (New Zealand); Fong, W. [Steward Observatory, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States); Bietenholz, M. [Hartebeesthoek Radio Observatory, P.O. Box 443, Krugersdorp 1740 (South Africa); Chornock, R. [Astrophysical Institute, Department of Physics and Astronomy, 251B Clippinger Lab, Ohio University, Athens, OH 45701 (United States); Fransson, C. [Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, SE106 91 Stockholm (Sweden); Fesen, R. A. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Lab, Hanover, NH 03755 (United States); Mackey, J., E-mail: dmilisav@cfa.harvard.edu [Argelander-Institut für Astronomie, Auf dem Hgel 71, D-53121 Bonn (Germany); and others

    2015-12-20

    We present optical observations of supernova SN 2014C, which underwent an unprecedented slow metamorphosis from H-poor type Ib to H-rich type IIn over the course of one year. The observed spectroscopic evolution is consistent with the supernova having exploded in a cavity before encountering a massive shell of the progenitor star’s stripped hydrogen envelope. Possible origins for the circumstellar shell include a brief Wolf–Rayet fast wind phase that overtook a slower red supergiant wind, eruptive ejection, or confinement of circumstellar material by external influences of neighboring stars. An extended high velocity Hα absorption feature seen in near-maximum light spectra implies that the progenitor star was not completely stripped of hydrogen at the time of core collapse. Archival pre-explosion Subaru Telescope Suprime-Cam and Hubble Space Telescope Wide Field Planetary Camera 2 images of the region obtained in 2009 show a coincident source that is most likely a compact massive star cluster in NGC 7331 that hosted the progenitor system. By comparing the emission properties of the source with stellar population models that incorporate interacting binary stars we estimate the age of the host cluster to be 30–300 Myr, and favor ages closer to 30 Myr in light of relatively strong Hα emission. SN 2014C is the best observed member of a class of core-collapse supernovae that fill the gap between events that interact strongly with dense, nearby environments immediately after explosion and those that never show signs of interaction. Better understanding of the frequency and nature of this intermediate population can contribute valuable information about the poorly understood final stages of stellar evolution.

  7. Chemical composition of the circumstellar disk around AB Aurigae

    Science.gov (United States)

    Pacheco-Vázquez, S.; Fuente, A.; Agúndez, M.; Pinte, C.; Alonso-Albi, T.; Neri, R.; Cernicharo, J.; Goicoechea, J. R.; Berné, O.; Wiesenfeld, L.; Bachiller, R.; Lefloch, B.

    2015-06-01

    Aims: Our goal is to determine the molecular composition of the circumstellar disk around AB Aurigae (hereafter, AB Aur). AB Aur is a prototypical Herbig Ae star and the understanding of its disk chemistry is paramount for understanding the chemical evolution of the gas in warm disks. Methods: We used the IRAM 30-m telescope to perform a sensitive search for molecular lines in AB Aur as part of the IRAM Large program ASAI (a chemical survey of Sun-like star-forming regions). These data were complemented with interferometric observations of the HCO+ 1→0 and C17O 1→0 lines using the IRAM Plateau de Bure Interferometer (PdBI). Single-dish and interferometric data were used to constrain chemical models. Results: Throughout the survey, several lines of CO and its isotopologues, HCO+, H2CO, HCN, CN, and CS, were detected. In addition, we detected the SO 54→33 and 56→45 lines, confirming the previously tentative detection. Compared to other T Tauri and Herbig Ae disks, AB Aur presents low HCN 3→2/HCO+ 3→2 and CN 2→1/HCN 3→2 line intensity ratios, similar to other transition disks. AB Aur is the only protoplanetary disk detected in SO thus far, and its detection is consistent with interpretation of this disk being younger than those associated with T Tauri stars. Conclusions: We modeled the line profiles using a chemical model and a radiative transfer 3D code. Our model assumes a flared disk in hydrostatic equilibrium. The best agreement with observations was obtained for a disk with a mass of 0.01 M⊙, Rin = 110 AU, Rout = 550 AU, a surface density radial index of 1.5, and an inclination of 27°. The intensities and line profiles were reproduced within a factor of ˜2 for most lines. This agreement is reasonable considering the simplicity of our model that neglects any structure within the disk. However, the HCN 3→2 and CN 2→1 line intensities were predicted to be more intense by a factor of >10. We discuss several scenarios to explain this

  8. TYPE Ia SUPERNOVAE STRONGLY INTERACTING WITH THEIR CIRCUMSTELLAR MEDIUM

    Energy Technology Data Exchange (ETDEWEB)

    Silverman, Jeffrey M. [Department of Astronomy, University of Texas, Austin, TX 78712-0259 (United States); Nugent, Peter E. [Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States); Gal-Yam, Avishay; Arcavi, Iair; Ben-Ami, Sagi [Benoziyo Center for Astrophysics, Weizmann Institute of Science, Rehovot 76100 (Israel); Sullivan, Mark [School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom); Howell, D. Andrew; Graham, Melissa L. [Las Cumbres Observatory Global Telescope Network, Goleta, CA 93117 (United States); Filippenko, Alexei V.; Bloom, Joshua S.; Cenko, S. Bradley; Clubb, Kelsey I. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Cao, Yi; Horesh, Assaf; Kulkarni, Shrinivas R. [Cahill Center for Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Chornock, Ryan; Foley, Ryan J. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Coil, Alison L. [Department of Physics, University of California, San Diego, La Jolla, CA 92093 (United States); Griffith, Christopher V. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Kasliwal, Mansi M., E-mail: jsilverman@astro.as.utexas.edu [Observatories of the Carnegie Institution of Science, Pasadena, CA 91101 (United States); and others

    2013-07-01

    Owing to their utility for measurements of cosmic acceleration, Type Ia supernovae (SNe Ia) are perhaps the best-studied class of SNe, yet the progenitor systems of these explosions largely remain a mystery. A rare subclass of SNe Ia shows evidence of strong interaction with their circumstellar medium (CSM), and in particular, a hydrogen-rich CSM; we refer to them as SNe Ia-CSM. In the first systematic search for such systems, we have identified 16 SNe Ia-CSM, and here we present new spectra of 13 of them. Six SNe Ia-CSM have been well studied previously, three were previously known but are analyzed in depth for the first time here, and seven are new discoveries from the Palomar Transient Factory. The spectra of all SNe Ia-CSM are dominated by H{alpha} emission (with widths of {approx}2000 km s{sup -1}) and exhibit large H{alpha}/H{beta} intensity ratios (perhaps due to collisional excitation of hydrogen via the SN ejecta overtaking slower-moving CSM shells); moreover, they have an almost complete lack of He I emission. They also show possible evidence of dust formation through a decrease in the red wing of H{alpha} 75-100 days past maximum brightness, and nearly all SNe Ia-CSM exhibit strong Na I D absorption from the host galaxy. The absolute magnitudes (uncorrected for host-galaxy extinction) of SNe Ia-CSM are found to be -21.3 mag {<=} M{sub R} {<=} -19 mag, and they also seem to show ultraviolet emission at early times and strong infrared emission at late times (but no detected radio or X-ray emission). Finally, the host galaxies of SNe Ia-CSM are all late-type spirals similar to the Milky Way, or dwarf irregulars like the Large Magellanic Cloud, which implies that these objects come from a relatively young stellar population. This work represents the most detailed analysis of the SN Ia-CSM class to date.

  9. Illuminating the Role of Spiral Waves in Circumstellar Disks

    Science.gov (United States)

    Bae, Jaehan; Hartmann, Lee W.

    2017-01-01

    The transport of angular momentum and mass, and the generation of turbulence, play a crucial role in the evolution of a variety of astrophysical disks. Spiral waves, driven for instance by companion bodies or instabilities, have long been recognized as an important means for the aforementioned two processes. In this dissertation talk, I will discuss an instability of spiral waves that I have recently come across. I will begin by presenting the results from a three-dimensional global hydrodynamic simulation which described the growth and saturation of the instability. The spiral wave instability (SWI) arises as inertial modes, natural oscillations in rotating systems, amplify when they resonantly couple to and extract energy from the background spiral waves. This leads to break down of the spiral waves into turbulence when the velocity perturbations caused by unstable inertial modes reach a similar magnitude to those induced by the spiral waves. As an implication of the instability, I will present numerical results and discuss the consequence of the SWI when it acts on the spiral waves driven by a Jupiter-mass planet in a protoplanetary disk. I find that the planet-driven spiral arms are destabilized via the SWI, generating hydrodynamic turbulence and sustained vertical flows that are associated with long wavelength inertial modes. The associated vertical diffusion rate measured from the simulations is such that solid particles with sizes up to a few centimeters are vertically mixed within the first scale height in a protosolar nebula-like disk. Since circumstellar disks are believed to remain laminar, and thus to induce no or very little particle stirring as suggested by recent magnetocentrifugal wind models, the results imply that the SWI can be the mechanism controlling the degree of vertical settling of solid particles in planet-hosting disks. In particular, if accretion of mm- to cm-sized pebbles dominates the growth of terrestrial bodies, the stirring of solid

  10. Trace Contaminant Control: An In-Depth Study of a Silica-Titania Composite for Photocatalytic Remediation of Closed-Environment Habitat Air

    Science.gov (United States)

    Coutts, Janelle L.

    2013-01-01

    This collection of studies focuses on a PCO system for the oxidation of a model compound, ethanol, using an adsorption-enhanced silica-TiO2 composite (STC) as the photocatalyst; studies are aimed at addressing the optimization of various parameters including light source, humidity, temperature, and possible poisoning events for use as part of a system for gaseous trace-contaminant control system in closed-environment habitats. The first goal focused on distinguishing the effect of photon flux (i.e., photons per unit time reaching a surface) from that of photon energy (i.e., wavelength) of a photon source on the PCO of ethanol. Experiments were conducted in a bench-scale annular reactor packed with STC pellets and irradiated with either a UV-A fluorescent black light blue lamp O max=365 nm) at its maximum light intensity or a UV-C germicidal lamp O. max=254 nm) at three levels of light intensity. The STC-catalyzed oxidation of ethanol was found to follow zero-order kinetics with respect to CO2 production, regardless of the photon source. Increased photon flux led to increased EtOH removal, mineralization, and oxidation rate accompanied by lower intermediate concentration in the effluent. The oxidation rate was higher in the reactor irradiated by UV-C than by UV-A (38.4 vs. 31.9 nM s-1 ) at the same photon flux, with similar trends for mineralization (53.9 vs. 43.4%) and reaction quantum efficiency (i.e., photonic efficiency, 63.3 vs. 50.1 nmol C02 mol photons-1 ). UV-C irradiation also led to decreased intermediate concentration in the effluent compared to UV -A irradiation. These results demonstrated that STC-catalyzed oxidation is enhanced by both increased photon flux and photon energy. The effect of temperature and relative humidity on the STC-catalyzed degradation of ethanol was also determined using the UV-A light source at its maximum intensity.

  11. Radio Supernovae: Circum-Stellar Investigation (C.S.I.) of Supernova Progenitor Stars

    Science.gov (United States)

    2009-02-24

    ar X iv :0 90 2. 40 59 v1 [ as tr o- ph .H E ] 2 4 Fe b 20 09 Radio Supernovae : Circum-Stellar Investigation (C.S.I.) of Supernova Progenitor...FEB 2009 2. REPORT TYPE 3. DATES COVERED 00-00-2009 to 00-00-2009 4. TITLE AND SUBTITLE Radio Supernovae : Circum-Stellar Investigation (C.S.I...of Supernova Progenitor Stars 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f

  12. Synthetic Spectra and Light Curves of Interacting Binaries and Exoplanets with Circumstellar Material: SHELLSPEC

    Science.gov (United States)

    Budaj, Ján

    2012-04-01

    Program SHELLSPEC is designed to calculate light-curves, spectra and images of interacting binaries and extrasolar planets immersed in a moving circumstellar environment which is optically thin. It solves simple radiative transfer along the line of sight in moving media. The assumptions include LTE and optional known state quantities and velocity fields in 3D. Optional (non)transparent objects such as a spot, disc, stream, jet, shell or stars may be defined (embedded) in 3D and their composite synthetic spectrum calculated. The Roche model can be used as a boundary condition for the radiative transfer. Recently, a new model of the reflection effect, dust and Mie scattering were incorporated into the code. ɛ Aurigae is one of the most mysterious objects on the sky. Prior modeling of its light-curve assumed a dark, inclined, disk of dust with a central hole to explain the light-curve with a sharp mid-eclipse brightening. Our model consists of two geometrically thick flared disks: an internal optically thick disk and an external optically thin disk which absorbs and scatters radiation. Shallow mid-eclipse brightening may result from eclipses by nearly edge-on flared (dusty or gaseous) disks. Mid-eclipse brightening may also be due to strong forward scattering and optical properties of the dust which can have an important effect on the light-curves. There are many similarities between interacting binary stars and transiting extrasolar planets. The reflection effect which is briefly reviewed is one of them. The exact Roche shape and temperature distributions over the surface of all currently known transiting extrasolar planets have been determined. In some cases (HAT-P-32b, WASP-12b, WASP-19b), departures from the spherical shape can reach 7-15%.

  13. Stellar Emission Inhibiting the Study of ``Exo-Chondrules'' in Circumstellar Debris

    Science.gov (United States)

    White, J. A.; Boley, A. C.

    2017-05-01

    The host stars in circumstellar disks can be a confounding parameter in recovering the disc's properties. I'll present examples where we can't study the small grains due to stellar effects and discuss a project designed to solve the issue.

  14. Daughter Fragmentation is Unlikely To Occur in Self-Gravitating Circumstellar Discs

    CERN Document Server

    Forgan, Duncan

    2016-01-01

    Circumstellar discs are thought to be self-gravitating at very early times. If the disc is relatively cool, extended and accreting sufficiently rapidly, it can fragment into bound objects of order a few Jupiter masses and upwards. Given that the fragment's initial angular momentum is non-zero, and it will continue to accrete angular momentum from the surrounding circumstellar disc, we should expect that the fragment will also possess a relatively massive disc at early times. Therefore, we can ask: is disc fragmentation a hierarchical process? Or, can a disc fragment go on to produce its own self-gravitating circumfragmentary disc that produces daughter fragments? We investigate this using a set of nested 1D self-gravitating disc models. We calculate the radial structure of a marginally stable, self-gravitating circumstellar disc, and compute its propensity to fragmentation. We use this data to construct the local fragment properties at this radius. For each circumstellar disc model that results in fragmentati...

  15. Circumstellar CO Emission in S Stars I. Mass-Loss with Little or No Dust

    Science.gov (United States)

    Sahai, R.; Liechti, S.

    1994-01-01

    47 S stars have been searched for circumstellar CO (J=1-0 and/or 2-1) emission, and 29 have been detected, including 4 which show no evidence of dust in their IRAS LRS spectra and one with possibly no Tc (and therefore not an AGB star).

  16. Detectability of Circumstellar SiO Maser Emission on VSOP-2 Baselines

    Science.gov (United States)

    Colomer, F.; Bujarrabal, V.; Ruiz, R. S.; Dodson, R.; Alcolea, J.; Desmurs, J.-F.

    2009-08-01

    We have studied compact circumstellar SiO maser emission at 86 GHz with the Global Millimeter VLBI Array (GMVA), which provides the same spatial resolution as the VSOP-2 to ground baselines at 43 GHz. We present preliminary maps of the emission, estimate the flux and size of the maser spots, and discuss their detectability on baselines from VSOP-2 to ground telescopes.

  17. Attenuation of super-soft X-ray sources by circumstellar material

    DEFF Research Database (Denmark)

    Nielsen, Mikkel; Gilfanov, Marat

    2015-01-01

    of the circumbinary material photo-ionised by the radiation of the central source. Our results show that the circumstellar mass-loss rates required for obcuration of super-soft X-ray sources is about an order of magnitude larger than those reported in earlier studies, for comparable model parameters. While this does...

  18. Circumstellar Dust Around AGB Stars and Implications for Infrared Emission from Galaxies

    CERN Document Server

    Villaume, Alexa; Johnson, Benjamin

    2015-01-01

    Stellar population synthesis (SPS) models are used to infer many galactic properties including star formation histories, metallicities, and stellar and dust masses. However, most SPS models neglect the effect of circumstellar dust shells around evolved stars and it is unclear to what extent they impact the analysis of SEDs. To overcome this shortcoming we have created a new set of circumstellar dust models, using the radiative transfer code DUSTY Ivezic et al. 1999, for asymptotic giant branch (AGB) stars and incorporated them into the Flexible Stellar Population Synthesis code. The circumstellar dust models provide a good fit to individual AGB stars as well as the IR color-magnitude diagrams of the Large and Small Magellanic Clouds. IR luminosity functions from the Large and Small Magellanic Clouds are not well-fit by the 2008 Padova isochrones when coupled to our circumstellar dust models, and so we adjusted the lifetimes of AGB stars in the models to provide a match to the data. We show, in agreement with ...

  19. [Closing diastemas].

    Science.gov (United States)

    Vieira, L C; Pereira, J C; Coradazzi, J L; Francischone, C E

    1990-01-01

    The authors describe a clinical case of closing upper central incisives diastema, reconstructiva of a conoid upper lateral and the rechaping of an upper canine to a lateral incisive. The material used was composite resin.

  20. Connecting the evolution of thermally pulsing asymptotic giant branch stars to the chemistry in their circumstellar envelopes -- I. The case of hydrogen cyanide

    CERN Document Server

    Marigo, Paola; Nanni, Ambra; Bressan, Alessandro; Girardi, Leo

    2015-01-01

    We investigate the formation of hydrogen cyanide (HCN) in the inner circumstellar envelopes of thermally pulsing asymptotic giant branch (TP-AGB) stars. A dynamic model for periodically shocked atmospheres, which includes an extended chemo-kinetic network, is for the first time coupled to detailed evolutionary tracks for the TP-AGB phase computed with the COLIBRI code. We carried out a calibration of the main shock parameters (the shock formation radius and the effective adiabatic index) using the circumstellar HCN abundances recently measured for a populous sample of pulsating TP-AGB stars. Our models recover the range of the observed HCN concentrations as a function of the mass-loss rates, and successfully reproduce the systematic increase of HCN moving along the M-S-C chemical sequence of TP-AGB stars, that traces the increase of the surface C/O ratio. The chemical calibration brings along two important implications: i) the first shock should emerge very close to the photosphere, and ii) shocks are expecte...

  1. Mapping the Circumstellar Environment of T Tauri with Fluorescent H_2 Emission

    CERN Document Server

    Walter, F M; Brown, A; Ardila, D R; Gahm, G F; Johns-Krull, C M; Lissauer, J J; Simon, M; Valenti, J A; Walter, Frederick M.; Herczeg, Gregory; Brown, Alexander; Ardila, David R.; Gahm, Goesta F.; Johns-Krull, Christopher M.; Lissauer, Jack J.; Simon, Michal; Valenti, Jeff A.

    2003-01-01

    We have obtained three long-slit, far UV spectra of the pre-main sequence system T Tauri. These HST/STIS spectra show a strong and variable on-source spectrum composed of both fluoresced H_2 and stellar chromospheric lines. Extended H_2 emission is seen up to 10" from the T Tau system. The on-source and extended H_2 are both pumped by H I Lyman alpha. The on-source H_2 is pumped by the red wing of a broad, self-absorbed Ly-alpha line, while the progressions seen in the extended gas are pumped from near line center. This suggests that the extended H_2 is pumped locally, and not by the stellar Ly-alpha line. The H_2 to the north and west coincides with the evacuated cavity bounded by the optical reflection nebulosity; to the south the extended H_2 coincides with the HH 255 outflow from the embedded infrared companion T Tau S. The spatial profile of the extended gas shows a prominent dip coincident with the position of T Tau S. This may be absorption by a disk associated with T Tau S. There is no evidence for ab...

  2. The relationship between gamma Cassiopeiae's X-ray emission and its circumstellar environment

    CERN Document Server

    Smith, M A; Motch, C; Henry, G W; Richardson, N D; Bjorkman, K S; Stee, Ph; Mourard, D; Monnier, J D; Che, X; Buecke, R; Pollmann, E; Gies, D R; Schaefer, G H; Brummelaar, T ten; McAlister, H A; Turner, N H; Sturmann, J; Sturmann, L; Ridgway, S T

    2012-01-01

    \\gamma Cas is the prototypical classical Be star and is best known for its variable hard X-ray emission. To elucidate the reasons for this emission, we mounted a multiwavelength campaign in 2010 centered around 4 XMM observations. The observational techniques included long baseline optical interferometry (LBOI), monitoring by an Automated Photometric Telescope and Halpha observations. Because gamma Cas is also known to be in a binary, we measured Halpha radial velocities and redetermined its period as 203.55+/-0.2 days and an eccentricity near zero. The LBOI observations suggest that the star's decretion disk was axisymmetric in 2010, has an inclination angle near 45^o, and a larger radius than previously reported. The Be star began an "outburst" at the beginning of our campaign, made visible by a disk brightening and reddening during our campaign. Our analyses of the new high resolution spectra disclosed many attributes found from spectra obtained in 2001 (Chandra) and 2004 (XMM). As well as a dominant hot 1...

  3. Single and Double Photoionization and Photodissociation of Toluene by Soft X-rays in Circumstellar Environment

    CERN Document Server

    Monfredini, T; Nascimento, M A C; Wolff, W; Boechat-Roberty, H M

    2016-01-01

    The formation of polycyclic aromatic hydrocarbons (PAHs) and their methyl derivatives occurs mainly in the dust shells of asymptotic giant branch (AGB) stars. The bands at 3.3 and 3.4 $\\mu$m, observed in infrared emission spectra of several objects, are attributed C-H vibrational modes in aromatic and aliphatic structures, respectively. In general, the feature at 3.3 $\\mu$m is more intense than the 3.4 $\\mu$m. Photoionization and photodissociation processes of toluene, the precursor of methylated PAHs, were studied using synchrotron radiation at soft X-ray energies around the carbon K edge with time-of-flight mass spectrometry. Partial ion yields of a large number of ionic fragments were extracted from single and 2D-spectra, where electron-ion coincidences have revealed the doubly charged parent-molecule and several doubly charged fragments containing seven carbon atoms with considerable abundance. \\textit{Ab initio} calculations based on density functional theory were performed to elucidate the chemical stru...

  4. THE CIRCUMSTELLAR ENVIRONMENT OF R CORONAE BOREALIS: WHITE DWARF MERGER OR FINAL-HELIUM-SHELL FLASH?

    Energy Technology Data Exchange (ETDEWEB)

    Clayton, Geoffrey C.; Andrews, J. E. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Sugerman, Ben E. K. [Department of Physics and Astronomy, Goucher College, 1021 Dulaney Valley Rd., Baltimore, MD 21204 (United States); Adam Stanford, S. [IGPP, Lawrence Livermore National Laboratory, Livermore, CA 94551 (United States); Whitney, B. A. [Space Science Institute, 4750 Walnut St. Suite 205, Boulder, CO 80301 (United States); Honor, J.; Babler, B. [Department of Astronomy, 475 North Charter St., University of Wisconsin, Madison, WI 53706 (United States); Barlow, M. J. [Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom); Gordon, K. D.; Bond, Howard E.; Matsuura, M. [STScI, 3700 San Martin Dr., Baltimore, MD 21218 (United States); Geballe, T. R. [Gemini Observatory, 670 N. A' ohoku Place, Hilo, HI 96720 (United States); De Marco, O. [Department of Physics, Macquarie University, Sydney, NSW 2109 (Australia); Lawson, W. A. [School of PEMS, University of New South Wales, ADFA, P.O. Box 7916, Canberra, ACT 2610 (Australia); Sibthorpe, B. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Olofsson, G. [Department of Astronomy, Stockholm University, AlbaNova University Center, Roslagstullsbacken 21, SE-10691 Stockholm (Sweden); Polehampton, E. [Space Science and Technology Department, Rutherford Appleton Laboratory, Didcot OX11 0QX (United Kingdom); Gomez, H. L.; Hargrave, P. C. [School of Physics and Astronomy, Cardiff University, 5 The Parade, Cardiff, Wales CF24 3YB (United Kingdom); Ivison, R. J., E-mail: gclayton@phys.lsu.edu, E-mail: jandrews@phys.lsu.edu, E-mail: ben.sugerman@goucher.edu, E-mail: stanford@physics.ucdavis.edu, E-mail: bwhitney@spacescience.org, E-mail: jhonor@astro.wisc.edu, E-mail: brian@astro.wisc.edu, E-mail: mjb@star.ucl.ac.uk [UK Astronomy Technology Centre, ROE, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); and others

    2011-12-10

    In 2007, R Coronae Borealis (R CrB) went into a historically deep and long decline. In this state, the dust acts like a natural coronagraph at visible wavelengths, allowing faint nebulosity around the star to be seen. Imaging has been obtained from 0.5 to 500 {mu}m with Gemini/GMOS, Hubble Space Telescope/WFPC2, Spitzer/MIPS, and Herschel/SPIRE. Several of the structures around R CrB are cometary globules caused by wind from the star streaming past dense blobs. The estimated dust mass of the knots is consistent with their being responsible for the R CrB declines if they form along the line of sight to the star. In addition, there is a large diffuse shell extending up to 4 pc away from the star containing cool 25 K dust that is detected all the way out to 500 {mu}m. The spectral energy distribution of R CrB can be well fitted by a 150 AU disk surrounded by a very large diffuse envelope which corresponds to the size of the observed nebulosity. The total masses of the disk and envelope are 10{sup -4} and 2 M{sub Sun }, respectively, assuming a gas-to-dust ratio of 100. The evidence pointing toward a white dwarf merger or a final-helium-shell flash origin for R CrB is contradictory. The shell and the cometary knots are consistent with a fossil planetary nebula. Along with the fact that R CrB shows significant lithium in its atmosphere, this supports the final-helium-shell flash. However, the relatively high inferred mass of R CrB and its high fluorine abundance support a white dwarf merger.

  5. Herschel/HIFI observations of the circumstellar ammonia lines in IRC+10216

    Science.gov (United States)

    Schmidt, M. R.; He, J. H.; Szczerba, R.; Bujarrabal, V.; Alcolea, J.; Cernicharo, J.; Decin, L.; Justtanont, K.; Teyssier, D.; Menten, K. M.; Neufeld, D. A.; Olofsson, H.; Planesas, P.; Marston, A. P.; Sobolev, A. M.; de Koter, A.; Schöier, F. L.

    2016-08-01

    Context. A discrepancy exists between the abundance of ammonia (NH3) derived previously for the circumstellar envelope (CSE) of IRC+10216 from far-IR submillimeter rotational lines and that inferred from radio inversion or mid-infrared (MIR) absorption transitions. Aims: To address the discrepancy described above, new high-resolution far-infrared (FIR) observations of both ortho- and para-NH3 transitions toward IRC+10216 were obtained with Herschel, with the goal of determining the ammonia abundance and constraining the distribution of NH3 in the envelope of IRC+10216. Methods: We used the Heterodyne Instrument for the Far Infrared (HIFI) on board Herschel to observe all rotational transitions up to the J = 3 level (three ortho- and six para-NH3 lines). We conducted non-LTE multilevel radiative transfer modelling, including the effects of near-infrared (NIR) radiative pumping through vibrational transitions. The computed emission line profiles are compared with the new HIFI data, the radio inversion transitions, and the MIR absorption lines in the ν2 band taken from the literature. Results: We found that NIR pumping is of key importance for understanding the excitation of rotational levels of NH3. The derived NH3 abundances relative to molecular hydrogen were (2.8 ± 0.5) × 10-8 for ortho-NH3 and for para-NH3, consistent with an ortho/para ratio of 1. These values are in a rough agreement with abundances derived from the inversion transitions, as well as with the total abundance of NH3 inferred from the MIR absorption lines. To explain the observed rotational transitions, ammonia must be formed near to the central star at a radius close to the end of the wind acceleration region, but no larger than about 20 stellar radii (1σ confidence level). Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. HIFI is the Herschel Heterodyne Instrument for the Far

  6. Close Relationship between the Frangibility of Mountain Eco-Environment and Mountain Disasters: A Case Study of Dong-chuan, Kunming in Yunnan Province

    Institute of Scientific and Technical Information of China (English)

    WANG Yuyi; TIAN Bing; LIU Shuzhen

    2007-01-01

    Anatomical details are given in this article, which is performed by investigating the relationship between through the frangibility of mountain eco-environment and the status of irrational land-use in typical region of debris flow in Dongchuan district, Kunming city, yun-nan Province. This analysis is extended to the relationship between vicissitude of mountain disasters and the frangibility of mountain environment. The relatively coupling action of a vicious circle is a evolving characteristic by debris flow sand-gravel there. The eco-security is being faced with serious challenge. The tactics of eco-security has been constructed since 1980s. Thus, the eco-environment can gradually be repaired and optimized to achieve a fine circle.

  7. The inner circumstellar disk of the UX Orionis star V1026 Scorpii

    Science.gov (United States)

    Vural, J.; Kreplin, A.; Kishimoto, M.; Weigelt, G.; Hofmann, K.-H.; Kraus, S.; Schertl, D.; Dugué, M.; Duvert, G.; Lagarde, S.; Massi, F.

    2014-04-01

    Context. The UX Ori type variables (named after the prototype of their class) are intermediate-mass pre-main sequence objects. One of the most likely causes of their variability is the obscuration of the central star by orbiting dust clouds. Aims: We investigate the structure of the circumstellar environment of the UX Ori star V1026 Sco (HD 142666) and test whether the disk inclination is large enough to explain the UX Ori variability. Methods: We observed the object in the low-resolution mode of the near-infrared interferometric VLTI/AMBER instrument and derived H- and K-band visibilities and closure phases. We modeled our AMBER observations, published Keck Interferometer observations, archival MIDI/VLTI visibilities, and the spectral energy distribution using geometric and temperature-gradient models. Results: Employing a geometric inclined-ring disk model, we find a ring radius of 0.15 ± 0.06 AU in the H band and 0.18 ± 0.06 AU in the K band. The best-fit temperature-gradient model consists of a star and two concentric, ring-shaped disks. The inner disk has a temperature of 1257+133-53 K at the inner rim and extends from 0.19 ± 0.01 AU to 0.23 ± 0.02 AU. The outer disk begins at 1.35+0.19-0.20 AU and has an inner temperature of 334+35-17 K. The derived inclination of 48.6+2.9-3.6° approximately agrees with the inclination derived with the geometric model (49 ± 5° in the K band and 50 ± 11° in the H band). The position angle of the fitted geometric and temperature-gradient models are 163 ± 9° (K band; 179 ± 17° in the H band) and 169.3+4.2-6.7°, respectively. Conclusions: The narrow width of the inner ring-shaped model disk and the disk gap might be an indication for a puffed-up inner rim shadowing outer parts of the disk. The intermediate inclination of ~50° is consistent with models of UX Ori objects where dust clouds in the inclined disk obscure the central star. Based on observations made with ESO telescopes at the La Silla Paranal Observatory

  8. Thin shell morphology in the circumstellar medium of massive binaries

    NARCIS (Netherlands)

    van Marle, A. -J; Keppens, R.; Meliani, Z.

    2011-01-01

    Context. In massive binaries, the powerful stellar winds of the two stars collide, leading to the formation of shock-dominated environments that can be modeled only in 3D. Aims. We investigate the morphology of the collision-front shell between the stellar winds of binary components in two long-peri

  9. Functional Comparison of Bacteria from the Human Gut and Closely Related Non-Gut Bacteria Reveals the Importance of Conjugation and a Paucity of Motility and Chemotaxis Functions in the Gut Environment.

    Directory of Open Access Journals (Sweden)

    Dragana Dobrijevic

    Full Text Available The human GI tract is a complex and still poorly understood environment, inhabited by one of the densest microbial communities on earth. The gut microbiota is shaped by millennia of evolution to co-exist with the host in commensal or symbiotic relationships. Members of the gut microbiota perform specific molecular functions important in the human gut environment. This can be illustrated by the presence of a highly expanded repertoire of proteins involved in carbohydrate metabolism, in phase with the large diversity of polysaccharides originating from the diet or from the host itself that can be encountered in this environment. In order to identify other bacterial functions that are important in the human gut environment, we investigated the distribution of functional groups of proteins in a group of human gut bacteria and their close non-gut relatives. Complementary to earlier global comparisons between different ecosystems, this approach should allow a closer focus on a group of functions directly related to the gut environment while avoiding functions related to taxonomically divergent microbiota composition, which may or may not be relevant for gut homeostasis. We identified several functions that are overrepresented in the human gut bacteria which had not been recognized in a global approach. The observed under-representation of certain other functions may be equally important for gut homeostasis. Together, these analyses provide us with new information about this environment so critical to our health and well-being.

  10. CIRCUMSTELLAR MAGNETITE FROM THE LAP 031117 CO3.0 CHONDRITE

    Energy Technology Data Exchange (ETDEWEB)

    Zega, Thomas J. [Lunar and Planetary Laboratory, University of Arizona, 1629 E. University Blvd, Tucson, AZ 85721-0092 (United States); Haenecour, Pierre; Floss, Christine [Laboratory for Space Sciences and Physics Department, Washington University, One Brookings Drive, Campus Box 1105, St. Louis, MO 63130 (United States); Stroud, Rhonda M., E-mail: tzega@lpl.arizona.edu [Materials Science and Technology Division, Code 6366, Naval Research Laboratory, 4555 Overlook Ave, SW Washington, DC 20375 (United States)

    2015-07-20

    We report the first microstructural confirmation of circumstellar magnetite, identified in a petrographic thin section of the LaPaz Icefield 031117 CO3.0 chondrite. The O-isotopic composition of the grain indicates an origin in a low-mass (∼2.2 M{sub ⊙}), approximately solar metallicity red/asymptotic giant branch (RGB/AGB) star undergoing first dredge-up. The magnetite is a single crystal measuring 750 × 670 nm, is free of defects, and is stoichiometric Fe{sub 3}O{sub 4}. We hypothesize that the magnetite formed via oxidation of previously condensed Fe dust within the circumstellar envelope of its progenitor star. Using an empirically derived rate constant for this reaction, we calculate that such oxidation could have occurred over timescales ranging from approximately ∼9000–500,000 years. This timescale is within the lifetime of estimates for dust condensation within RGB/AGB stars.

  11. Differential interferometric phases at high spectral resolution as a sensitive physical diagnostic of circumstellar disks

    CERN Document Server

    Faes, D M; Rivinius, Th; Štefl, S; Baade, D; de Souza, A Domiciano

    2013-01-01

    Context. The circumstellar disks ejected by many rapidly rotating B stars (so-called Be stars) offer the rare opportunity of studying the structure and dynamics of gaseous disks at high spectral as well as angular resolution. Aims. This paper explores a newly identified effect in spectro-interferometric phase that can be used for probing the inner regions of gaseous edge-on disks on a scale of a few stellar radii. Methods. The origin of this effect (dubbed central quasi-emission phase signature, CQE-PS) lies in the velocity-dependent line absorption of photospheric radiation by the circumstellar disk. At high spectral and marginal interferometric resolution, photocenter displacements between star and isovelocity regions in the Keplerian disk reveal themselves through small interferometric phase shifts. To investigate the diagnostic potential of this effect, a series of models are presented, based on detailed radiative transfer calculations in a viscous decretion disk. Results. Amplitude and detailed shape of ...

  12. Circumstellar Habitable Zones to Ecodynamic Domains: A Preliminary Review and Suggested Future Directions

    CERN Document Server

    Heath, Martin J

    2009-01-01

    The concept of the Circumstellar Habitable Zone has served the scientific community well for some decades. It slips easily off the tongue, and it would be hard to replace. Recently, however, several workers have postulated types of habitable bodies which might exist outside the classic circumstellar habitable zone (HZ). These include not only bodies which orbit at substantial distances from their parent stars, but also snowball worlds with geothermally-maintained internal oceans and even densely-atmosphered worlds with geothermally-maintained surface oceans, which have been ejected from unstable planetary systems into interstellar space. If habitability is not a unique and diagnostic property of the HZ, then the value of the term has been compromised in a fundamental way. At the same time, it has become evident that multiple environmental states, differing in important ways in their habitability, are possible even for geophysically similar planets subject to similar levels of insolation, within the classic HZ...

  13. Radiative transfer modeling of three T Tauri stars: selecting candidates for studying circumstellar disk evolution

    Institute of Scientific and Technical Information of China (English)

    Yao Liu; Hong-Chi Wang; Sebastian Wolf; David Madlener

    2013-01-01

    We present modeling work on three young stellar objects that are promising targets for future high-resolution observations to investigate circumstellar disk evolution.The currently available data comprise the spectral energy distribution from optical to millimeter wavelengths which allow constraining the structure of the circumstellar disk using self-consistent radiative transfer models.The results suggest that the assumption of well-mixed dust and gas leads to overestimation of flux in the far-infrared.Observational and theoretical arguments suggest that an overall decrease in far-infrared excess can be explained by dust settling towards the midplane.A new disk model is hence employed to take the effect of dust sedimentation into account.The extended model satisfactorily reproduces all existing observations.The three targets studied here therefore deserve follow-up observations to reveal the evolutionary state of their protoplanetary disks.

  14. Synthetic photometry for carbon-rich giants II. The effects of pulsation and circumstellar dust

    CERN Document Server

    Nowotny, Walter; Höfner, Susanne; Lederer, Michael T

    2011-01-01

    By using self-consistent dynamic model atmospheres which simulate pulsation-enhanced dust-driven winds of AGB stars we studied in detail the influence of (i) pulsations of the stellar interiors, and (ii) the development of dusty stellar winds on the spectral appearance of long period variables with carbon-rich atmospheric chemistry. While the pulsations lead to large-amplitude photometric variability, the dusty envelopes cause pronounced circumstellar reddening. Based on one selected dynamical model which is representative of C-type Mira variables with intermediate mass loss rates, we calculated synthetic spectra and photometry for standard broad-band filters from the visual to the near-infrared. Our modelling allows to investigate in detail the substantial effect of circumstellar dust on the resultant photometry. The pronounced absorption of amorphous carbon dust grains leads to colour indices which are significantly redder than the corresponding ones based on hydrostatic dust-free models. Only if we account...

  15. VizieR Online Data Catalog: Database of circumstellar OH masers (Engels+, 2015)

    Science.gov (United States)

    Engels, D.; Bunzel, F.

    2015-08-01

    We present a new database of circumstellar OH masers at 1612, 1665, and 1667MHz in the Milky Way galaxy in tabular form. The database (version 2.4) contains 13655 observations and 2341 different stars detected in at least one transition and includes published data until end of 2014. Interferometric follow-up observations and monitor programs are stored in two auxiliary tables. (3 data files).

  16. Efficacy of potential phage cocktails against Vibrio harveyi and closely related Vibrio species isolated from shrimp aquaculture environment in the south east coast of India.

    Science.gov (United States)

    Stalin, Nattan; Srinivasan, Pappu

    2017-08-01

    A diverse set of novel phages infecting the marine pathogenic Vibrio harveyi was isolated from shrimp aquaculture environments in the south east coast of India. Based on initial screening, three phages with a broad host range revealed that the growth inhibition of phage is relatively specific to V. harveyi. They were also able to infect V. alginolyticus and V. parahemolyticus that belonged to the Harveyi clade species from shrimp pond and sea coast environment samples. However, the impact of these phages on their host bacterium are well understood; a one-step growth curve experiment and transmission electron microscope (TEM) revealed three phages grouped under the Myoviridae (VHM1 and VHM2); Siphoviridae (VHS1) family. These phages were further molecular characterized with respect to phage genomic DNA isolates. The randomly amplified polymorphic DNA (RAPD), restriction fragment length polymorphism (RFLP) digestion with HindIII, and major structural proteins were distinguished by sodium-dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE) clearly indicated that all the phage isolates were different, even when they came from the same source, giving an insight into the diversity of phages. Evaluation of microcosm studies of Penaeus monodon larvae infected with V. harveyi (105 CFU mL-1) showed that larvae survival after 96 h in the presence of phage treatment at 109 PFU mL-1 was enhanced when compared with the control. The resolution in over survival highly recommended that this study provides the phage-based therapy which could be an innovative and eco-friendly solution against Vibrio disease in shrimp aquaculture and in the natural environment. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Oxygen Chemistry in the Circumstellar Envelope of the Carbon-Rich Star IRC+10216

    CERN Document Server

    Agundez, M; Agundez, Marcelino; Cernicharo, Jose

    2006-01-01

    In this paper we study the oxygen chemistry in the C-rich circumstellar shells of IRC+10216. The recent discoveries of oxygen bearing species (water, hydroxyl radical and formaldehyde) toward this source challenge our current understanding of the chemistry in C-rich circumstellar envelopes. The presence of icy comets surrounding the star or catalysis on iron grain surfaces have been invoked to explain the presence of such unexpected species. This detailed study aims at evaluating the chances of producing O-bearing species in the C-rich circumstellar envelope only by gas phase chemical reactions. For the inner hot envelope, it is shown that although most of the oxygen is locked in CO near the photosphere (as expected for a C/O ratio greater than 1), some stellar radii far away species such as H2O and CO2 have large abundances under the assumption of thermochemical equilibrium. It is also shown how non-LTE chemistry makes very difficult the CO-->H2O,CO2 transformation predicted in LTE. Concerning the chemistry ...

  18. Observational Possibility of the "Snow Line" on the Surface of Circumstellar Disks with the Scattered Light

    CERN Document Server

    Inoue, Akio K; Nakamoto, Taishi; Oka, Akinori

    2008-01-01

    We discuss how we obtain the spatial distribution of ice on the surface of the circumstellar disk around young stars. Ice in the disks plays a very important role in various issues, for instance, on the disk structure, on the planet formation, on the isotopic anomaly in meteorites, and on the origin of the sea on the Earth. Therefore, the spatially resolved observation of the condensation/sublimation front of ice, so-called ``snow line'' is strongly required. Here, we propose a new method for obtaining the spatially resolved ``snow line'' on the circumstellar disks by observing 3 \\micron H$_2$O ice feature in the scattered light. Based on radiative transfer considerations, we show that the feature is clearly imprinted in the spectrum of the scattered light from both optically thick and thin circumstellar disks. We also show that the scattered light and the H$_2$O ice feature from protoplanetary disks are detectable and spatially resolvable with the current instruments through a $H_2O$ narrowband filter around...

  19. High-Resolution Near-Infrared Polarimetry of a Circumstellar Disk around UX Tau A

    Science.gov (United States)

    Tanii, Ryoko; Itoh, Yoichi; Kudo, Tomoyuki; Hioki, Tomonori; Oasa, Yumiko; Gupta, Ranjan; Sen, Asoke K.; Wisniewski, John P.; Muto, Takayuki; Grady, Carol A.; Hashimoto, Jun; Fukagawa, Misato; Mayama, Satoshi; Hornbeck, Jeremy; Sitko, Michael L.; Russell, Ray W.; Werren, Chelsea; Curé, Michel; Currie, Thayne; Ohashi, Nagayoshi; Okamoto, Yoshiko; Momose, Munetake; Honda, Mitsuhiko; Inutsuka, Shu-ichi; Takeuchi, Taku; Dong, Ruobing; Abe, Lyu; Brandner, Wolfgang; Brandt, Timothy D.; Carson, Joseph; Egner, Sebastian E.; Feldt, Markus; Fukue, Tsubasa; Goto, Miwa; Guyon, Olivier; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko S.; Henning, Thomas; Hodapp, Klaus W.; Ishii, Miki; Iye, Masanori; Janson, Markus; Kandori, Ryo; Knapp, Gillian R.; Kusakabe, Nobuhiko; Kuzuhara, Masayuki; Matsuo, Taro; McElwain, Michael W.; Miyama, Shoken; Morino, Jun-ichi; Moro-Martín, Amaya; Nishimura, Tetsuro; Pyo, Tae-Soo; Serabyn, Eugene; Suto, Hiroshi; Suzuki, Ryuji; Takami, Michihiro; Takato, Naruhisa; Terada, Hiroshi; Thalmann, Christian; Tomono, Daigo; Turner, Edwin L.; Watanabe, Makoto; Yamada, Toru; Takami, Hideki; Usuda, Tomonori; Tamura, Motohide

    2012-12-01

    We present H-band polarimetric imagery of UX Tau A taken with HiCIAO/AO188 on the Subaru Telescope. UX Tau A has been classified as a pre-transitional disk object, with a gap structure separating its inner and outer disks. Our imagery taken with the 0.''15 (21 AU) radius coronagraphic mask has revealed a strongly polarized circumstellar disk surrounding UX Tau A, which extends to 120 AU, at a spatial resolution of 0.''1 (14 AU). It is inclined by 46° ± 2°, since the west side is nearest. Although SED modeling and sub-millimeter imagery have suggested the presence of a gap in the disk, with the inner edge of the outer disk estimated to be located at 25-30 AU, we detect no evidence of a gap at the limit of our inner working angle (23 AU) at the near-infrared wavelength. We attribute the observed strong polarization (up to 66%) to light scattering by dust grains in the disk. However, neither polarization models of the circumstellar disk based on Rayleigh-scattering nor Mie-scattering approximations were consistent with the observed azimuthal profile of the polarization degrees of the disk. Instead, a geometric optics model of the disk with nonspherical grains with radii of 30μm is consistent with the observed profile. We suggest that the dust grains have experienced frequent collisional coagulations, and have grown in the circumstellar disk of UX Tau A.

  20. Circumstellar Dust, PAHs, and Stellar Populations in Early-Type Galaxies: Insights from GALEX and WISE

    CERN Document Server

    Simonian, Gregory V

    2016-01-01

    A majority of early-type galaxies contain interstellar dust, yet the origin of this dust, and why the dust sometimes exhibits unusual PAH ratios, remains a mystery. If the dust is internally produced, the most likely origin is the large number of AGB stars associated with the old stellar population. We present GALEX and WISE elliptical aperture photometry of $\\sim350$ early-type galaxies with Spitzer mid-infrared spectroscopy and/or ancillary data from ATLAS3D, to characterize their circumstellar dust and the shape of the radiation field that illuminates the interstellar PAHs. We find that circumstellar dust is ubiquitous in early-type galaxies, which indicates some tension between stellar population age estimates and models for circumstellar dust production in very old stellar populations. We also use dynamical masses from ATLAS3D to show that WISE W1 (3.4 $\\mu$m) mass-to-light ratios are inconsistent with model predictions for a single IMF, as found by previous work. While the stellar population differences...

  1. High-Resolution Near-Infrared Polarimetry of a Circumstellar Disk around UX Tau A

    Science.gov (United States)

    Serabyn, G.; Grady, C. A.; Currie, T.

    2012-01-01

    We present H-band polarimetric imagery of UX Tau A taken with HiCIAO/AO188 on the Subaru Telescope. UX Tau A has been classified as a pre-transitional disk object, with a gap structure separating its inner and outer disks. Our imagery taken with the 0.15" (21 AU) radius coronagraphic mask has revealed a strongly polarized circumstellar disk surrounding UX Tau A which extends to 120 AU, at a spatial resolution of 0.1" (14 AU). It is inclined by 46 degrees plus or minus 2 degrees as the west side is nearest. Although SED modeling and sub-millimeter imagery suggested the presence of a gap in the disk, with the inner edge of the outer disk estimated to be located at 25 - 30 AU, we detect no evidence of a gap at the limit of our inner working angle (23AU) at the near-infrared wavelength. We attribute the observed strong polarization (up to 66 %) to light scattering by dust grains in the disk. However, neither polarization models of the circumstellar disk based on Rayleigh scattering nor Mie scattering approximations were consistent with the observed azimuthal profile of the polarization degrees of the disk. Instead, a geometric optics model of the disk with nonspherical grains with the radii of 30 micrometers is consistent with the observed profile. We suggest that the dust grains have experienced frequent collisional coagulations and have grown in the circumstellar disk of UX Tau A.

  2. The US Green Building Council`s initiatives to improve the energy and environmental efficiency of the {open_quotes}whole building environment{close_quotes}

    Energy Technology Data Exchange (ETDEWEB)

    Italiano, M.

    1994-12-31

    Today, there is a strong public demand for environmental and energy efficiency in the built environment. According to EPA for at least the past three or four years, there has been one hundred twenty billion dollars annually spent on the environment. This is being done because there are some 30 federal statutes relating to environmental protection. On average there are about 10 separate statutes at every state level. This legislation has taken since the 1970`s to accumulate. They have been enacted because of strong public demand for environmental protection. Public opinion polls have shown for the last five years that support for environmental protections exceeds 90%. It is a very popular national commitment. There are no more debates over whether we need to stop pollution. Those have long gone, and this is being recognized by the building community. We need to recognize that there is a public demand for these issues to be evaluated, discussed and resolved. Buildings, productivity, energy and environmental efficiency are a huge investment in the country, and it is thought that a deliberative debate with decisions on a consensus basis in an expedited manner, is going to be very effective.

  3. Surveillance of Avian H7N9 Virus in Various Environments of Zhejiang Province, China before and after Live Poultry Markets Were Closed in 2013-2014.

    Directory of Open Access Journals (Sweden)

    Xiaoxiao Wang

    Full Text Available To date, there have been a total of 637 laboratory-confirmed cases of human infection with avian influenza A (H7N9 virus across mainland China, with 28% (179/637 of these reported in Zhejiang Province. Surveillance of avian H7N9 virus was conducted to investigate environmental contamination during H7N9 outbreaks. We sought to evaluate the prevalence of H7N9 in the environment, and the effects of poultry market closures on the incidence of human H7N9 cases.We collected 6740 environmental samples from 751 sampling sites across 11 cities of Zhejiang Province (China between January 2013 and March 2014. The presence of H7N9 was determined by reverse transcription polymerase chain reaction, with prevalence compared between sites and over time. The relationship between environmental contamination and human cases of H7N9 infection were analyzed using Spearman's ranked correlation coefficient.Of the 6740 samples, 10.09% (680/6740 were H7N9-positive. The virus was found to circulate seasonally, and peaked during the spring and winter of 2013-2014. The prevalence of the virus decreased from the north to the southeast of the province, coinciding with the geographical distribution of human H7N9 cases. Compared with other sampling sites, live poultry markets (LPMs had the highest prevalence of H7N9 virus at 13.94% (667/4784. Of the various sample types analyzed, virus prevalence was highest for chopping board swabs at 15.49% (110/710. The prevalence of the virus in the environment positively correlated with the incidence of human H7N9 cases (r2 = 0.498; P < 0.01. Cities with a higher incidence of human H7N9 cases also had a higher prevalence of H7N9 among samples and at sampling sites. Following the closure of LPMs at the end of January 2014, the prevalence of H7N9 decreased from 19.18% (487/2539 to 6.92% (79/1141. This corresponded with a decrease in the number of human H7N9 cases reported.The prevalence of H7N9 virus in environmental samples oscillated

  4. Surveillance of Avian H7N9 Virus in Various Environments of Zhejiang Province, China before and after Live Poultry Markets Were Closed in 2013–2014

    Science.gov (United States)

    Wang, Xiaoxiao; Liu, Shelan; Mao, Haiyan; Yu, Zhao; Chen, Enfu; Chai, Chengliang

    2015-01-01

    Background To date, there have been a total of 637 laboratory-confirmed cases of human infection with avian influenza A (H7N9) virus across mainland China, with 28% (179/637) of these reported in Zhejiang Province. Surveillance of avian H7N9 virus was conducted to investigate environmental contamination during H7N9 outbreaks. We sought to evaluate the prevalence of H7N9 in the environment, and the effects of poultry market closures on the incidence of human H7N9 cases. Methods We collected 6740 environmental samples from 751 sampling sites across 11 cities of Zhejiang Province (China) between January 2013 and March 2014. The presence of H7N9 was determined by reverse transcription polymerase chain reaction, with prevalence compared between sites and over time. The relationship between environmental contamination and human cases of H7N9 infection were analyzed using Spearman’s ranked correlation coefficient. Results Of the 6740 samples, 10.09% (680/6740) were H7N9-positive. The virus was found to circulate seasonally, and peaked during the spring and winter of 2013–2014. The prevalence of the virus decreased from the north to the southeast of the province, coinciding with the geographical distribution of human H7N9 cases. Compared with other sampling sites, live poultry markets (LPMs) had the highest prevalence of H7N9 virus at 13.94% (667/4784). Of the various sample types analyzed, virus prevalence was highest for chopping board swabs at 15.49% (110/710). The prevalence of the virus in the environment positively correlated with the incidence of human H7N9 cases (r2 = 0.498; P H7N9 cases also had a higher prevalence of H7N9 among samples and at sampling sites. Following the closure of LPMs at the end of January 2014, the prevalence of H7N9 decreased from 19.18% (487/2539) to 6.92% (79/1141). This corresponded with a decrease in the number of human H7N9 cases reported. Conclusions The prevalence of H7N9 virus in environmental samples oscillated seasonally

  5. The solution properties of mefenamic acid and a closely related analogue are indistinguishable in polar solvents but significantly different in nonpolar environments.

    Science.gov (United States)

    Lee, Eun Hee; Byrn, Stephen R; Pinal, Rodolfo

    2012-12-01

    This study investigates the cosolute effects of mefenamic acid (XA) and flufenamic acid (FA). These compounds serve as model of a drug discovery lead compound and a structural analogue. The activity coefficients of XA and FA in different solvents were obtained from solubility measurements at 25°C. The effect of varying concentrations of FA on the solubility of XA in four different solvents, including toluene, cyclohexane, ethanol, and an ethanol-water mixture (80:20, v/v), was investigated. The magnitude of change in the activity coefficient of XA in the presence of FA in different solvents was used to elucidate the thermodynamic effect of FA on the solubility of XA. Nuclear magnetic resonance and Fourier-transform infrared spectroscopy were used to obtain molecular level information about the interactions of the compounds in solution. The presence of FA increases XA solubility in toluene and in cyclohexane as much as seven-fold. Conversely, in ethanol and the ethanol-water mixture, similar levels of FA have essentially no effect on the solubility of XA. The solution properties investigated show that despite the close structural similarity between XA and FA, the two compounds are strongly distinguishable in nonpolar solvents. Conversely, the solution properties of the same two solutes are indistinguishable in polar solvents. A solubilization model based on solute-cosolute interactions is presented.

  6. Improving the thin-disk models of circumstellar disk evolution. The 2+1-dimensional model

    Science.gov (United States)

    Vorobyov, Eduard I.; Pavlyuchenkov, Yaroslav N.

    2017-09-01

    Context. Circumstellar disks of gas and dust are naturally formed from contracting pre-stellar molecular cores during the star formation process. To study various dynamical and chemical processes that take place in circumstellar disks prior to their dissipation and transition to debris disks, the appropriate numerical models capable of studying the long-term disk chemodynamical evolution are required. Aims: We improve the frequently used 2D hydrodynamical model for disk evolution in the thin-disk limit by employing a better calculation of the disk thermal balance and adding a reconstruction of the disk vertical structure. Together with the hydrodynamical processes, the thermal evolution is of great importance since it influences the strength of gravitational instability and the chemical evolution of the disk. Methods: We present a new 2+1-dimensional numerical hydrodynamics model of circumstellar disk evolution, where the thin-disk model is complemented with the procedure for calculating the vertical distributions of gas volume density and temperature in the disk. The reconstruction of the disk vertical structure is performed at every time step via the solution of the time-dependent radiative transfer equations coupled to the equation of the vertical hydrostatic equilibrium. Results: We perform a detailed comparison between circumstellar disks produced with our previous 2D model and with the improved 2+1D approach. The structure and evolution of resulting disks, including the differences in temperatures, densities, disk masses, and protostellar accretion rates, are discussed in detail. Conclusions: The new 2+1D model yields systematically colder disks, while the in-falling parental clouds are warmer. Both effects act to increase the strength of disk gravitational instability and, as a result, the number of gravitationally bound fragments that form in the disk via gravitational fragmentation as compared to the purely 2D thin-disk simulations with a simplified

  7. Identification of phase-independent spectral lines in close binary V455 CYG: I. Telluric lines

    Directory of Open Access Journals (Sweden)

    Cséki A.

    2007-01-01

    Full Text Available Spectroscopic observations of close binary star V455 Cygni reveal many lines that originate in interstellar and circumstellar medium and the atmo­sphere of the Earth; we found over two hundred such spectral features, and in this paper we present the list of telluric lines we identified through comparison with HITRAN database of molecular lines. The lines that remain unidentified or show peculiar behavior will be discussed in the second part of the paper. .

  8. Detailed modelling of the circumstellar molecular line emission of the S-type AGB star W Aquilae

    CERN Document Server

    Danilovich, T; Justtanont, K; Lombaert, R; Maercker, M; Olofsson, H; Ramstedt, S; Royer, P

    2014-01-01

    S-type AGB stars have a C/O ratio which suggests that they are transition objects between oxygen-rich M-type stars and carbon-rich C-type stars. As such, their circumstellar compositions of gas and dust are thought to be sensitive to their precise C/O ratio, and it is therefore of particular interest to examine their circumstellar properties. We present new Herschel HIFI and PACS sub-millimetre and far-infrared line observations of several molecular species towards the S-type AGB star W Aql. We use these observations, which probe a wide range of gas temperatures, to constrain the circumstellar properties of W Aql, including mass-loss rate and molecular abundances. We used radiative transfer codes to model the circumstellar dust and molecular line emission to determine circumstellar properties and molecular abundances. We assumed a spherically symmetric envelope formed by a constant mass-loss rate driven by an accelerating wind. Our model includes fully integrated H2O line cooling as part of the solution of th...

  9. Circumstellar dust, PAHs and stellar populations in early-type galaxies: insights from GALEX and WISE

    Science.gov (United States)

    Simonian, Gregory V.; Martini, Paul

    2017-02-01

    A majority of early-type galaxies contain interstellar dust, yet the origin of this dust, and why the dust sometimes exhibits unusual polycyclic aromatic hydrocarbon (PAH) ratios, remains a mystery. If the dust is internally produced, it likely originates from the large number of asymptotic giant branch stars associated with the old stellar population. We present GALEX and WISE elliptical aperture photometry of ˜310 early-type galaxies with Spitzer mid-infrared spectroscopy and/or ancillary data from ATLAS3D, to characterize their circumstellar dust and the shape of the radiation field that illuminates the interstellar PAHs. We find that circumstellar dust is ubiquitous in early-type galaxies, which indicates some tension between stellar population age estimates and models for circumstellar dust production in very old stellar populations. We also use dynamical masses from ATLAS3D to show that WISE W1 (3.4 μm) mass-to-light ratios are consistent with the initial mass function variation found by previous work. While the stellar population differences in early-type galaxies correspond to a range of radiation field shapes incident upon the diffuse dust, the ratio of the ionization-sensitive 7.7 μm/11.3 μm PAH feature does not correlate with the shape of the radiation field, nor to variations with the size-sensitive 11.3 μm/17 μm ratio. The 7.7 μm/11.3 μm PAH ratio does tend to be smaller in galaxies with proportionally greater H2 emission, which is evidence that processing of primarily smaller grains by shocks is responsible for the unusual ratios, rather than substantial differences in the overall PAH size or ionization distribution.

  10. Evidence of Dissipation of Circumstellar Disks from L-band Spectra of Bright Galactic Be Stars

    Science.gov (United States)

    Sabogal, B. E.; Ubaque, K. Y.; García-Varela, A.; Álvarez, M.; Salas, L.

    2017-01-01

    We present L-band spectra of the Be stars γ Cas, ϕ Per, 28 Tau, θ CrB, 66 Oph, o Her, and 28 Cyg, obtained through use of the CID-InSb spectrograph with the 2.1-m telescope at OAN/UNAM San Pedro Martir Observatory. This is the first report of L-band spectra of o Her and θ CrB, and of the data obtained with this spectrograph. We obtain flux ratios of hydrogen lines for these stars, finding that they have optically thin envelopes, except by 66 Oph and θ CrB, which do not show evidence of a circumstellar disk. γ Cas and ϕ Per have flux ratio values of hydrogen lines closer to the optically thick case than the other stars. We use the line flux ratio diagram and optical spectra reported in the literature to study the life cycles of the disks. We find clear evidence of the dissipating process of the envelopes of 66 Oph and 28 Cyg, i.e., they are decaying stars. 28 Tau seems to have passed by a similar process. γ Cas and ϕ Per are stable stars because their circumstellar disks do not show notorious changes for many years. Finally, the stars in a build-up phase, whose envelopes are generated after a decaying phase or for the first time, have not yet been observed in the L-band. It would be useful to monitor more Be stars to observe this class of stars that probably change from a very tenuous envelope to an optically thick circumstellar disk. The line flux ratio diagram seems to confirm that late Be stars have more tenuous disks than early-type Be stars, as they tend to be separated at the left bottom and the top right parts of the diagram, respectively. Larger samples of Be stars are needed to confirm this hypothesis through a statistical analysis.

  11. Simulation of compact circumstellar shells around Type Ia supernovae and the resulting high-velocity features

    Science.gov (United States)

    Mulligan, Brian W.; Wheeler, J. Craig

    2017-01-01

    For Type Ia supernovae that are observed prior to B-band maximum (approximately 18-20 days after the explosion) Ca absorption features are observed at velocities of order 10,000 km/s faster than the typical photospheric features. These high velocity features weaken in the first couple of weeks, disappearing entirely by a week after B-band maximum. The source of this high velocity material is uncertain: it may be the result of interaction between the supernova and circumstellar material or may be the result of plumes or bullets of material ejected during the course of the explosion. We simulate interaction between a supernova and several compact circumstellar shells, located within 0.03 solar radii of the progenitor white dwarf and having masses of 0.02 solar masses or less. We use FLASH to perform hydrodynamic simulations of the system to determine the structure of the ejecta and shell components after the interaction, then use these results to generate synthetic spectra with 1 day cadence for the first 25 days after the explosion. We compare the evolution of the velocity and pseudo-equivalent width of the Ca near-infrared triplet features in the synthetic spectra to observed values, demonstrating that these models are consistent with observations. Additionally, we fit the observed spectra of SN 2011fe (Parrent 2012, Pereira 2013) prior to B-band maximum using these models and synthetic spectra and provide an estimate for Ca abundance within the circumstellar material with implications for the mechanism by which the white dwarf explodes.

  12. Indicator of Exo-Solar Planet(s) in the Circumstellar Disk Around Beta Pictoris

    CERN Document Server

    Gorkavyi, N; Ozernoy, L M; Taidakova, T; Mather, J; Gorkavyi, Nick; Heap, Sara; Ozernoy, Leonid; Taidakova, Tanya; Mather, John

    2000-01-01

    Our efficient numerical approach has been applied to modeling the asymmetric circumstellar dust disk around Beta Pictoris as observed with the HST/STIS. We present a new model on the origin of the warping of the Beta Pic disk. We suggest that the observed warp is formed by the gravitational influence of a planet with a mass of about 10 masses of Earth, at a distance of 70 AU, and a small inclination ($\\sim 2.5^\\circ$) of the planetary orbit to the main dust disk. Results of our modeling are compared with the STIS observations.

  13. HST Spectroscopy of Spot 1 on the Circumstellar Ring of SN 1987A

    CERN Document Server

    Michael, E; Pun, C S J; Garnavich, P M; Challis, P M; Kirshner, R P; Raymond, J; Borkowski, K J; Chevalier, R A; Filippenko, A V; Fransson, C; Lundqvist, P; Panagia, N; Phillips, M M; Sonneborn, G; Suntzeff, N B; Wang, L; Wheeler, J C; Michael, Eli; Cray, Richard Mc; Garnavich, Peter; Challis, Peter; Kirshner, Robert P.; Raymond, John; Borkowski, Kazimierz; Chevalier, Roger; Filippenko, Alexei V.; Fransson, Claes; Lundqvist, Peter; Panagia, Nino; Sonneborn, George; Suntzeff, Nicholas B.; Wang, Lifan

    2000-01-01

    We present ultraviolet and optical spectra of the first bright spot (PA = 29 degrees) on Supernova 1987A's equatorial circumstellar ring taken with the Space Telescope Imaging Spectrograph. We interpret this spot as the emission produced by radiative shocks that occur where the supernova blast wave strikes an inward protrusion of the ring. The observed line widths and intensity ratios indicate the presence of radiative shocks with velocities ranging from 100 to 250 km s^-1 entering dense (> 10^4 cm^-3) gas. These observations, and future observations of the development of the spectra and line profiles, provide a unique opportunity to study the hydrodynamics of radiative shocks.

  14. Circumstellar disks and planets. Science cases for next-generation optical/infrared long-baseline interferometers

    CERN Document Server

    Wolf, Sebastian; Alexander, Richard; Berger, Jean-Philippe; Creech-Eakman, Michelle; Duchene, Gaspard; Dutrey, Anne; Mordasini, Christophe; Pantin, Eric; Pont, Frederic; Pott, Joerg-Uwe; Tatulli, Eric; Testi, Leonardo

    2012-01-01

    We present a review of the interplay between the evolution of circumstellar disks and the formation of planets, both from the perspective of theoretical models and dedicated observations. Based on this, we identify and discuss fundamental questions concerning the formation and evolution of circumstellar disks and planets which can be addressed in the near future with optical and infrared long-baseline interferometers. Furthermore, the importance of complementary observations with long-baseline (sub)millimeter interferometers and high-sensitivity infrared observatories is outlined.

  15. On the central symmetry of the circumstellar envelope of RS Cnc

    CERN Document Server

    Nhung, Pham Tuyet; Winters, Jan Martin; Darriulat, Pierre; Gérard, Eric; Bertre, Thibaut Le

    2014-01-01

    We present a phenomenological study of CO(1-0) and CO(2-1) emission from the circumstellar envelope (CSE) of the Asymptotic Giant Branch (AGB) star RS\\,Cnc. It reveals departures from central symmetry that turn out to be efficient tools for the exploration of some of the CSE properties. We use a wind model including a bipolar flow with a typical wind velocity of $\\sim$8 km\\,s$^{-1}$ decreasing to $\\sim$2 km\\,s$^{-1}$ near the equator to describe Doppler velocity spectral maps obtained by merging data collected at the IRAM Plateau de Bure Interferometer and Pico Veleta single dish radio telescope. Parameters describing the wind morphology and kinematics are obtained, together with the radial dependence of the gas temperature in the domain of the circumstellar envelope probed by the CO observations. Significant north-south central asymmetries are revealed by the analysis, which we quantify using a simple phenomenological description. The origin of such asymmetries is unclear.

  16. Tracing planet-induced structures in circumstellar disks using molecular lines

    CERN Document Server

    Ober, F; Uribe, A L; Klahr, H H

    2015-01-01

    Circumstellar disks are considered to be the birthplace of planets. Specific structures like spiral arms, gaps, and cavities are characteristic indicators of planet-disk interaction. Investigating these structures can provide insights into the growth of protoplanets and the physical properties of the disk. We investigate the feasibility of using molecular lines to trace planet-induced structures in circumstellar disks. Based on 3D hydrodynamic simulations of planet-disk interactions, we perform self-consistent temperature calculations and produce N-LTE molecular line velocity-channel maps and spectra of these disks using our new N-LTE line radiative transfer code Mol3D. Subsequently, we simulate ALMA observations using the CASA simulator. We consider two nearly face-on inclinations, 5 disk masses, 7 disk radii, and 2 different typical pre-main-sequence host stars (T Tauri, Herbig Ae). We calculate up to 141 individual velocity-channel maps for five molecules/isotopoloques in a total of 32 rotational transitio...

  17. VLA Observations of HI in the Circumstellar Envelopes of Asymptotic Giant Branch Stars

    CERN Document Server

    Matthews, Lynn D; 10.1086/512613

    2008-01-01

    (Abridged) We have used the VLA to search for neutral atomic hydrogen in the circumstellar envelopes of five AGB stars. We have detected HI 21-cm emission coincident in both position and velocity with the semi-regular variable RS Cnc. The emission comprises a compact, slightly elongated feature centered on the star with a mean diameter ~82'' (1.5e17 cm), plus an additional filament extending ~6' to the NW. This filament suggests that a portion of the mass loss is highly asymmetric. We estimate MHI=1.5e-3 Msun and M_dot~1.7e-7 Msun/yr. Toward R Cas, we detect weak emission that peaks at the stellar systemic velocity and overlaps with the location of its circumstellar dust shell and thus is probably related to the star. In the case of IRC+10216, we were unable to confirm the detection of HI in absorption against the cosmic background previously reported by Le Bertre & Gerard. However, we detect arcs of emission at projected distances of r~14'-18' (~2e18 cm) to the NW. A large separation of the emission from...

  18. V409 Tau As Another AA Tau: Photometric Observations of Stellar Occultations by the Circumstellar Disk

    CERN Document Server

    Rodriguez, Joseph E; Stassun, Keivan G; Siverd, Robert J; Cargile, Phillip; Weintraub, David A; Beatty, Thomas G; Gaudi, B Scott; Mamajek, Eric E; Sanchez, Nicole

    2015-01-01

    AA Tau is a well studied young stellar object that presents many of the photometric characteristics of a Classical T Tauri star (CTTS), including short-timescale stochastic variability attributed to spots and/or accretion as well as long duration dimming events attributed to occultations by vertical features (e.g., warps) in its circumstellar disk. We present new photometric observations of AA Tau from the Kilodegree Extremely Little Telescope North (KELT-North) which reveal a deep, extended dimming event in 2011, which we show supports the interpretation by Bouvier et al. (2013) of an occultation by a high-density feature in the circumstellar disk located >8 AU from the star. We also present KELT-North observations of V409 Tau, a relatively unstudied young stellar object also in Taurus-Auriga, showing short timescale erratic variability, along with two separate long and deep dimming events, one from January 2009 through late October 2010, and the other from March 2012 until at least September 2013. We interp...

  19. Mass loss from OH/IR stars - Models for the infrared emission of circumstellar dust shells

    Science.gov (United States)

    Justtanont, K.; Tielens, A. G. G. M.

    1992-01-01

    The IR emission of a sample of 24 OH/IR stars is modeled, and the properties of circumstellar dust and mass-loss rate of the central star are derived. It is shown that for some sources the observations of the far-IR emission is well fitted with a lambda exp -1 law, while some have a steeper index of 1.5. For a few sources, the presence of circumstellar ice grains is inferred from detailed studies of the observed 10-micron feature. Dust mass-loss rates are determined from detailed studies for all the stars in this sample. They range from 6.0 x 10 exp -10 solar mass/yr for an optically visible Mira to 2.2 x 10 exp -6 solar mass/yr for a heavily obscured OH/IR star. These dust mass-loss rates are compared to those calculated from IRAS photometry using 12-, 25-, and 60-micron fluxes. The dust mass-loss rates are also compared to gas mass-loss rates determined from OH and CO observations. For stars with tenuous shells, a dust-to-gas ratio of 0.001 is obtained.

  20. The circumstellar envelope of the C-rich post-AGB star HD 56126

    CERN Document Server

    Hony, S; Waters, L B F M; De Koter, A

    2003-01-01

    We present a detailed study of the circumstellar envelope of the post-asymptotic giant branch ``21 micron object'' HD 56126. We build a detailed dust radiative transfer model of the circumstellar envelope in order to derive the dust composition and mass, and the mass-loss history of the star. To model the emission of the dust we use amorphous carbon, hydrogenated amorphous carbon, magnesium sulfide and titanium carbide. We present a detailed parametrisation of the optical properties of hydrogenated amorphous carbon as a function of H/C content. The mid-infrared imaging and spectroscopy is best reproduced by a single dust shell from 1.2 to 2.6 arcsec radius around the central star. This shell originates from a short period during which the mass-loss rate exceeded 10^(-4) M_sun/yr. We find that the strength of the ``21'' micron feature poses a problem for the TiC identification. The low abundance of Ti requires very high absorption cross-sections in the ultraviolet and visible wavelength range to explain the st...

  1. Effects of stellar flybys on planetary systems: 3D modeling of the circumstellar disks damping effects

    CERN Document Server

    Picogna, Giovanni

    2014-01-01

    Stellar flybys in star clusters are suspected to affect the orbital architecture of planetary systems causing eccentricity excitation and orbital misalignment between the planet orbit and the equatorial plane of the star. We explore whether the impulsive changes in the orbital elements of planets, caused by an hyperbolic stellar flyby, can be fully damped by the circumstellar disk surrounding the star. The time required to disperse stellar clusters is in fact comparable to circumstellar disk's lifetime. We have modelled in 3D a system made of a solar type star surrounded by a low density disk with a giant planet embedded in it approached on a hyperbolic encounter trajectory by a second star, of similar mass and with its own disk. We focus on extreme configurations where a very deep stellar flyby perturbs a Jovian planet on an external orbit. This allows to test in full the ability of the disk to erase the effects of the stellar encounter. We find that the amount of mass lost by the disk during the stellar fly...

  2. Atomic and molecular hydrogen in the circumstellar envelopes of late-type stars

    Science.gov (United States)

    Glassgold, A. E.; Huggins, P. J.

    1983-01-01

    The distribution of atomic and molecular hydrogen in the expanding circumstellar envelopes of cool evolved stars is discussed. The main concern is to evaluate the effects of photodestruction of H2 by galactic UV radiation, including shielding of the radiation by H2 itself and by dust in the envelope. One of the most important parameters is the H/H2 ratio which is frozen out in the upper atmosphere of the star. For stars with photospheric temperatures greater than about 2500 K, atmospheric models suggest that the outflowing hydrogen is mainly atomic, whereas cooler stars should be substantially molecular. In the latter case, photodissociation of H2 and heavy molecules contribute to the atomic hydrogen content of the outer envelope. The presented estimates indicate that atomic hydrogen is almost at the limit of detection in the C-rich star IRC + 10216, and may be detectable in warmer stars. Failure to detect it would have important implications for the general understanding of circumstellar envelopes.

  3. Testing circumstellar disk lifetimes in young embedded clusters associated with the Vela Molecular Ridge

    CERN Document Server

    Massi, Fabrizio; Codella, Claudio; Testi, Leonardo; Vanzi, Leonardo; Gomes, Joana

    2010-01-01

    Context. The Vela Molecular Ridge hosts a number of young embedded star clusters in the same evolutionary stage. Aims. The main aim of the present work is testing whether the fraction of members with a circumstellar disk in a sample of clusters in the cloud D of the Vela Molecular Ridge, is consistent with relations derived for larger samples of star clusters with an age spread. Besides, we want to constrain the age of the young embedded star clusters associated with cloud D. Methods. We carried out L (3.78 microns) photometry on images of six young embedded star clusters associated with cloud D of the Vela Molecular Ridge, taken with ISAAC at the VLT. These data are complemented with the available HKs photometry. The 6 clusters are roughly of the same size and appear to be in the same evolutionary stage. The fraction of stars with a circumstellar disk was measured in each cluster by counting the fraction of sources displaying a NIR excess in colour-colour (HKsL) diagrams. Results. The L photometry allowed us...

  4. Circumstellar C2, CN, and CH+ in the optical spectra of post-AGB stars

    CERN Document Server

    Bakker, E J; Waters, L B F M; Schoenmaker, T; Bakker, Eric J.; Dishoeck, Ewine F. van; Schoenmaker, Ton

    1996-01-01

    We present optical high-resolution spectra of a sample of sixteen post-AGB stars and IRC +10216. Of the post-AGB stars, ten show C2 Phillips and Swan and CN Red System absorption, one CH+ emission, one CH+ absorption, and four without any molecules. We find typically Trot=43-399, 155-202, and 18-50 K, log N = 14.90-15.57, 14.35, and 15.03-16.47 cm-2 for C2, CH+, and CN respectively, and 0.620. The presence of C2 and CN absorption is correlated with cold dust (Tdust300K). All objects with the unidentified 21mum emission feature exhibit C2 and CN absorption, but not all objects with C2 and CN detections exhibit a 21mum feature. The derived expansion velocity, ranging from 5 to 44 km/s, is the same as that derived from CO millimeter line emission. This unambiguously proves that these lines are of circumstellar origin and are formed in the AGB ejecta (circumstellar shell expelled during the preceding AGB phase). Furthermore there seems to be a relation between the C2 molecular column density and the expansion vel...

  5. A Correlation Between Circumstellar Disks and Rotation in the Upper Scorpius OB Association

    CERN Document Server

    Dahm, S E; White, R J

    2011-01-01

    We present projected rotational velocities for 20 early-type (B8-A9) and 74 late-type (F2-M8) members of the ~5 Myr old Upper Scorpius OB Association derived from high dispersion optical spectra obtained with the High Resolution Echelle Spectrometer (HIRES) on Keck I and the Magellan Inamori Kyocera Echelle (MIKE) on the Magellan Clay telescope. The spectroscopic sample is composed of stars and brown dwarfs with infrared signatures of circumstellar disks, both primordial and debris, and non-excess sources of comparable spectral type. We merge projected rotational velocities, accretion diagnostics, and Spitzer Space Telescope Infrared Array Camera (IRAC) and Multiband Imaging Photometer for Spitzer (MIPS) 24 micron photometry to examine the relationship between rotation and circumstellar disks. The rotational velocities are strongly correlated with spectral type, a proxy for mass, such that the median vsini for B8-A9 type stars is: 195(+/-)70 km/s, F2-K4: 37.8(+/-)7.4 km/s, K5-K9: 13.8(+21.3/-8.2) km/s, M0-M5:...

  6. AGB stars in the LMC: evolution of dust in circumstellar envelopes

    CERN Document Server

    Dell'Agli, F; Schneider, R; Di Criscienzo, M; García-Hernández, D A; Rossi, C; Brocato, E

    2014-01-01

    We calculated theoretical evolutionary sequences of asymptotic giant branch (AGB) stars, including formation and evolution of dust grains in their circumstellar envelope. By considering stellar populations of the Large Magellanic Cloud (LMC), we calculate synthetic colour-colour and colour-magnitude diagrams, which are compared with those obtained by the Spitzer Space Telescope. The comparison between observations and theoretical predictions outlines that extremely obscured carbon-stars and oxygen-rich sources experiencing hot bottom burning (HBB) occupy well defined, distinct regions in the colour-colour ($[3.6]-[4.5]$, $[5.8]-[8.0]$) diagram. The C-rich stars are distributed along a diagonal strip that we interpret as an evolutionary sequence, becoming progressively more obscured as the stellar surface layers enrich in carbon. Their circumstellar envelopes host solid carbon dust grains with size in the range $0.05 2$, are the descendants of stars with initial mass $M_{in} \\sim 2.5 - 3 M_{\\odot}$ in the ver...

  7. Conditions for circumstellar disc formation - II. Effects of initial cloud stability and mass accretion rate

    Science.gov (United States)

    Machida, Masahiro N.; Matsumoto, Tomoaki; Inutsuka, Shu-ichiro

    2016-12-01

    Disc formation in strongly magnetized cloud cores is investigated using a three-dimensional magnetohydrodynamic simulation with a focus on the effects of the initial cloud stability and the mass accretion rate. The initial cloud stability greatly alters the disc formation process even for prestellar clouds with the same mass-to-flux ratio. A high mass accretion rate on to the disc-forming region is realized in initially unstable clouds, and a large angular momentum is introduced into the circumstellar region in a short time. The region around the protostar has both a thin infalling envelope and a weak magnetic field, which both weaken the effect of magnetic braking. The growth of the rotation-supported disc is promoted in such unstable clouds. Conversely, clouds in an initially near-equilibrium state show lower accretion rates of mass and angular momentum. The angular momentum is transported to the outer envelope before protostar formation. After protostar formation, the circumstellar region has a thick infalling envelope and a strong magnetic field that effectively brakes the disc. As a result, disc formation is suppressed when the initial cloud is in a nearly stable state. The density distribution of the initial cloud also affects the disc formation process. Disc growth strongly depends on the initial conditions when the prestellar cloud has a uniform density, whereas there is no significant difference in the disc formation process in prestellar clouds with non-uniform densities.

  8. A Deep Chandra Observation of Kepler's Supernova Remnant: A Type Ia Event with Circumstellar Interaction

    CERN Document Server

    Reynolds, S P; Hwang, U; Hughes, J P; Badenes, C; Laming, J M; Blondin, J M

    2007-01-01

    We present initial results of a 750 ks Chandra observation of the remnant of Kepler's supernova of AD 1604. The strength and prominence of iron emission, together with the absence of O-rich ejecta, demonstrate that Kepler resulted from a thermonuclear supernova, even though evidence for circumstellar interaction is also strong. We have analyzed spectra of over 100 small regions, and find that they fall into three classes. (1) The vast majority show Fe L emission between 0.7 and 1 keV and Si and S K alpha emission; we associate these with shocked ejecta. A few of these are found at or beyond the mean blast wave radius. (2) A very few regions show solar O/Fe abundance rations; these we associate with shocked circumstellar medium (CSM). Otherwise O is scarce. (3) A few regions are dominated by continuum, probably synchrotron radiation. Finally, we find no central point source, with a limit about 100 times fainter than the central object in Cas A. The evidence that the blast wave is interacting with CSM may indic...

  9. The Evolutionary State of Anemic Circumstellar Disks and the Primordial-to-Debris Disk Transition

    CERN Document Server

    Currie, Thayne

    2008-01-01

    We investigate the evolution of $\\sim$ 3 Myr-old MIPS-detected circumstellar disks in IC 348 that may be in an intermediate stage between primordial, optically-thick disks of gas/dust and debris disks characteristic of the final stages of planet formation. We demonstrate that these \\textit{anemic} disks are not a homogenous class of objects corresponding to a unique evolutionary state. Rather, such disks around early (B/A) spectral type stars are most likely warm, terrestrial zone debris disks; MIPS-detected anemic disks around later (M) stars are likely \\textit{evolved primordial disks} such as transition disks in their mid-IR colors, accretion signatures, and disk luminosities. Anemic disks surrounding G and K stars contain both populations. The difference in evolutionary states between anemic disks surrounding early type vs. late-type stars is consistent with a mass-dependent evolution of circumstellar disks from the primordial disk phase through the debris disk phase. Specifically, disks characteristicall...

  10. The frequency and infrared brightness of circumstellar discs at white dwarfs

    CERN Document Server

    Rocchetto, M; Gaensicke, B T; Bergfors, C

    2014-01-01

    White dwarfs whose atmospheres are polluted by terrestrial-like planetary debris have become a powerful and unique tool to study evolved planetary systems. This paper presents results for an unbiased Spitzer IRAC search for circumstellar dust orbiting a homogeneous and well-defined sample of 134 single white dwarfs. The stars were selected without regard to atmospheric metal content but were chosen to have 1) hydrogen rich atmospheres, 2) 17 000 K < T_eff < 25 000 K and correspondingly young post main-sequence ages of 15-270Myr, and 3) sufficient far-ultraviolet brightness for a corresponding Hubble Space Telescope COS Snapshot. Five white dwarfs were found to host an infrared bright dust disc, three previously known, and two reported here for the first time, yielding a nominal 3.7% of white dwarfs in this post-main sequence age range with detectable circumstellar dust. Remarkably, complementary HST observations indicate that a fraction of 27% show metals in their photosphere that can only be explained ...

  11. Mass loss from OH/IR stars - Models for the infrared emission of circumstellar dust shells

    Science.gov (United States)

    Justtanont, K.; Tielens, A. G. G. M.

    1992-01-01

    The IR emission of a sample of 24 OH/IR stars is modeled, and the properties of circumstellar dust and mass-loss rate of the central star are derived. It is shown that for some sources the observations of the far-IR emission is well fitted with a lambda exp -1 law, while some have a steeper index of 1.5. For a few sources, the presence of circumstellar ice grains is inferred from detailed studies of the observed 10-micron feature. Dust mass-loss rates are determined from detailed studies for all the stars in this sample. They range from 6.0 x 10 exp -10 solar mass/yr for an optically visible Mira to 2.2 x 10 exp -6 solar mass/yr for a heavily obscured OH/IR star. These dust mass-loss rates are compared to those calculated from IRAS photometry using 12-, 25-, and 60-micron fluxes. The dust mass-loss rates are also compared to gas mass-loss rates determined from OH and CO observations. For stars with tenuous shells, a dust-to-gas ratio of 0.001 is obtained.

  12. Recurring Occultations of RW Aurigae by Coagulated Dust in the Tidally Disrupted Circumstellar Disk

    CERN Document Server

    Rodriguez, Joseph E; Siverd, Robert J; Pepper, Joshua; Stassun, Keivan G; Gaudi, B Scott; Weintraub, David A; Beatty, Thomas G; Lund, Michael B; Stevens, Daniel J

    2015-01-01

    We present photometric observations of RW Aurigae, a Classical T Tauri system, that reveal two remarkable dimming events. These events are similar to that which we observed in 2010-2011, which was the first such deep dimming observed in RW Aur in a century's worth of photometric monitoring. We suggested the 2010-2011 dimming was the result of an occultation of the star by its tidally disrupted circumstellar disk. In 2012-2013, the RW Aur system dimmed by ~0.7 mag for ~40 days and in 2014/2015 the system dimmed by ~2 mag for >250 days. The ingress/egress duration measurements of the more recent events agree well with those from the 2010-2011 event, providing strong evidence that the new dimmings are kinematically associated with the same occulting source. Therefore, we suggest that both the 2012-2013 and 2014-2015 dimming events, measured using data from the Kilodegree Extremely Little Telescope and the Kutztown University Observatory, are also occultations of RW Aur A by tidally disrupted circumstellar materi...

  13. THE PDS 66 CIRCUMSTELLAR DISK AS SEEN IN POLARIZED LIGHT WITH THE GEMINI PLANET IMAGER

    Energy Technology Data Exchange (ETDEWEB)

    Wolff, Schuyler G.; Greenbaum, Alexandra Z. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Perrin, Marshall; Hines, Dean C. [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Millar-Blanchaer, Maxwell A. [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada); Nielsen, Eric L. [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305 (United States); Wang, Jason; Dong, Ruobing; Duchêne, Gaspard; Graham, James R.; Kalas, Paul [Astronomy Department, University of California, Berkeley, Berkeley, CA 94720 (United States); Cardwell, Andrew [LBT Observatory, University of Arizona, 933 N. Cherry Avenue, Room 552, Tucson, AZ 85721 (United States); Chilcote, Jeffrey [Dunlap Institute for Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada); Draper, Zachary H. [University of Victoria, 3800 Finnerty Road, Victoria, BC V8P 5C2 (Canada); Fitzgerald, Michael P.; Hung, Li-Wei [Department of Physics and Astronomy, University of California, Los Angeles, 430 Portola Plaza, Los Angeles, CA 90095 (United States); Goodsell, Stephen J. [Gemini Observatory, 670 N. A’ohoku Place, Hilo, HI 96720 (United States); Grady, Carol A. [Eureka Scientific, 2452 Delmer, Suite 100, Oakland, CA 96002 (United States); Hartung, Markus; Hibon, Pascale, E-mail: swolff9@jh.edu [Gemini Observatory, Casilla 603, La Serena (Chile); and others

    2016-02-10

    We present H- and K-band imaging polarimetry for the PDS 66 circumstellar disk obtained during the commissioning of the Gemini Planet Imager (GPI). Polarization images reveal a clear detection of the disk in to the 0.″12 inner working angle (IWA) in the H band, almost three times closer to the star than the previous Hubble Space Telescope (HST) observations with NICMOS and STIS (0.″35 effective IWA). The centro-symmetric polarization vectors confirm that the bright inner disk detection is due to circumstellar scattered light. A more diffuse disk extends to a bright outer ring centered at 80 AU. We discuss several physical mechanisms capable of producing the observed ring + gap structure. GPI data confirm enhanced scattering on the east side of the disk that is inferred to be nearer to us. We also detect a lateral asymmetry in the south possibly due to shadowing from material within the IWA. This likely corresponds to a temporally variable azimuthal asymmetry observed in HST/STIS coronagraphic imaging.

  14. Detection of circumstellar CH2CHCN, CH2CN, CH3CCH and H2CS

    CERN Document Server

    Agundez, M; Cernicharo, J; Pardo, J R; Guélin, M

    2007-01-01

    We report on the detection of vinyl cyanide (CH2CHCN), cyanomethyl radical (CH2CN), methylacetylene (CH3CCH) and thioformaldehyde (H2CS) in the C-rich star IRC +10216. These species, which are all known to exist in dark clouds, are detected for the first time in the circumstellar envelope around an AGB star. The four molecules have been detected trough pure rotational transitions in the course of a 3 mm line survey carried out with the IRAM 30-m telescope. The molecular column densities are derived by constructing rotational temperature diagrams. A detailed chemical model of the circumstellar envelope is used to analyze the formation of these molecular species. We have found column densities in the range 5 x 10^(12)- 2 x 10^(13) cm^(-2), which translates to abundances relative to H2 of several 10^(-9). The chemical model is reasonably successful in explaining the derived abundances through gas phase synthesis in the cold outer envelope. We also find that some of these molecules, CH2CHCN and CH2CN, are most pr...

  15. BANYAN. VIII. New Low-Mass Stars and Brown Dwarfs with Candidate Circumstellar Disks

    CERN Document Server

    Boucher, Anne; Gagné, Jonathan; Malo, Lison; Faherty, Jacqueline K; Doyon, René; Chen, Christine H

    2016-01-01

    We present the results of a search for new circumstellar disks around low-mass stars and brown dwarfs with spectral types >K5 that are confirmed or candidate members of nearby young moving groups. Our search input sample was drawn from the BANYAN surveys of Malo et al. and Gagn\\'e et al. Two-Micron All-Sky Survey and Wide-field Infrared Survey Explorer data were used to detect near- to mid-infrared excesses that would reveal the presence of circumstellar disks. A total of 13 targets with convincing excesses were identified: four are new and nine were already known in the literature. The new candidates are 2MASS J05010082$-$4337102 (M4.5), J08561384$-$1342242 (M8$\\,\\gamma$), J12474428$-$3816464 (M9$\\,\\gamma$) and J02265658$-$5327032 (L0$\\,\\delta$), and are candidate members of the TW Hya ($\\sim10\\pm 3\\,$Myr), Columba ($\\sim 42^{+6}_{-4}\\,$Myr) and Tucana-Horologium ($\\sim 45\\pm 4\\,$Myr) associations, with masses of $120$ and $13-18\\,M_{\\mathrm{Jup}}$. The M8$-$L0 objects in Columba and Tucana-Horologium are po...

  16. HST/STIS results on circumstellar disks and jets, future coronography and technology for IR multi-object spectroscopy

    Science.gov (United States)

    Woodgate, Bruce E.

    2002-01-01

    Results of studies of circumstellar disks and jets obtained by HST/STIS visible coronagraphy and UV spectroscopy, and by ground-based Fabry-Perot coronagraphy will be presented. Future improvements in coronagraphy will be discussed. The development of microshutter arrays as programmable multi-object selectors for the NGST near IR spectrograph will be described.

  17. Discovery of multiple dust shells beyond 1 arcmin in the circumstellar envelope of IRC +10216 using Herschel/PACS

    NARCIS (Netherlands)

    Decin, L.; Royer, P.; Cox, N.L.J.; Vandenbussche, B.; Ottensamer, R.; Blommaert, J.A.D.L.; Groenewegen, M.A.T.; Barlow, M.J.; Lim, T.; Kerschbaum, F.; Posch, T.; Waelkens, C.

    2011-01-01

    We present new Herschel/PACS images at 70, 100, and 160 μm of the well-known, nearby, carbon-rich asymptotic giant branch star IRC+10216 revealing multiple dust shells in its circumstellar envelope. For the first time, dust shells (or arcs) are detected until 320''. The almost spherical shells are n

  18. Chemistry and distribution of daughter species in the circumstellar envelopes of O-rich AGB stars

    Science.gov (United States)

    Li, Xiaohu; Millar, Tom J.; Heays, Alan N.; Walsh, Catherine; van Dishoeck, Ewine F.; Cherchneff, Isabelle

    2016-03-01

    Context. Thanks to the advent of Herschel and ALMA, new high-quality observations of molecules present in the circumstellar envelopes of asymptotic giant branch (AGB) stars are being reported that reveal large differences from the existing chemical models. New molecular data and more comprehensive models of the chemistry in circumstellar envelopes are now available. Aims: The aims are to determine and study the important formation and destruction pathways in the envelopes of O-rich AGB stars and to provide more reliable predictions of abundances, column densities, and radial distributions for potentially detectable species with physical conditions applicable to the envelope surrounding IK Tau. Methods: We use a large gas-phase chemical model of an AGB envelope including the effects of CO and N2 self-shielding in a spherical geometry and a newly compiled list of inner-circumstellar envelope parent species derived from detailed modeling and observations. We trace the dominant chemistry in the expanding envelope and investigate the chemistry as a probe for the physics of the AGB phase by studying variations of abundances with mass-loss rates and expansion velocities. Results: We find a pattern of daughter molecules forming from the photodissociation products of parent species with contributions from ion-neutral abstraction and dissociative recombination. The chemistry in the outer zones differs from that in traditional PDRs in that photoionization of daughter species plays a significant role. With the proper treatment of self-shielding, the N → N2 and C+→ CO transitions are shifted outward by factors of 7 and 2, respectively, compared with earlier models. An upper limit on the abundance of CH4 as a parent species of (≲2.5 × 10-6 with respect to H2) is found for IK Tau, and several potentially observable molecules with relatively simple chemical links to other parent species are determined. The assumed stellar mass-loss rate, in particular, has an impact on the

  19. Effects of stellar flybys on planetary systems: 3D modeling of the circumstellar disk's damping effects

    Science.gov (United States)

    Picogna, G.; Marzari, F.

    2014-04-01

    Context. Stellar flybys in star clusters are suspected of affecting the orbital architecture of planetary systems causing eccentricity excitation and orbital misalignment between the planet orbit and the equatorial plane of the star. Aims: We explore whether the impulsive changes in the orbital elements of planets, caused by a hyperbolic stellar flyby, can be fully damped by the circumstellar disk surrounding the star. The time required to disperse stellar clusters is comparable to the circumstellar disk's lifetime. Since we perform 3D simulations, we can also test the inclination, excitation, and damping. Methods: We have modeled in 3D with the SPH code VINE, a system made of a solar-type star surrounded by a low density disk with a giant planet embedded in it approached on a hyperbolic encounter trajectory by a second star of similar mass and with its own disk. Different inclinations between the disks, planet orbit, and star trajectory have been considered to explore various encounter geometries. We focus on an extreme configuration where a very deep stellar flyby perturbs a Jovian planet on an external orbit. This allows us to test in full the ability of the disk to erase the effects of the stellar encounter. Results: We find that the amount of mass lost by the disk during the stellar flyby is less than in 2D models where a single disk was considered. This is mostly related to the mass exchange between the two disks at the encounter. The damping in eccentricity is slightly faster than in 2D models and it occurs on timescales on the order of a few kyr. During the flyby both the disks are warped owing to the mutual interaction and to the stellar gravitational perturbations, but they quickly relax to a new orbital plane. The planet is quickly dragged back within the disk by the tidal interaction with the gas. The only trace of the flyby left in the planet system, after about 104 yr, is a small misalignment, lower than 9°, between the star equatorial plane and the

  20. Temporomandibular Joint, Closed

    Science.gov (United States)

    ... Gallery > Oral Health > The Temporomandibular Joint, Closed The Temporomandibular Joint, Closed Main Content Title: The Temporomandibular Joint, Closed Description: The temporomandibular joint connects the lower ...

  1. Early-time signatures of {\\gamma}-ray emission from supernovae in dense circumstellar media

    CERN Document Server

    Kantzas, Dimitrios; Mastichiadis, Apostolos

    2016-01-01

    We present our results on the {\\gamma}-ray emission from interaction-powered supernovae (SNe), a recently discovered SN type that is suggested to be surrounded by a circumstellar medium (CSM) with densities 10^7-10^12~ cm^-3. Such high densities favor inelastic collisions between relativistic protons accelerated in the SN blast wave and CSM protons and the production of {\\gamma}-ray photons through neutral pion decays. Using a numerical code that includes synchrotron radiation, adiabatic losses due to the expansion of the source, photon-photon interactions, proton-proton collisions and proton-photon interactions, we calculate the multi-wavelength non-thermal photon emission soon after the shock breakout and follow its temporal evolution until 100-1000 days. Focusing on the {\\gamma}-ray emission at >100 MeV, we show that this could be detectable by the Fermi-LAT telescope for nearby (10^11 cm^-3).

  2. CO and HI emission from the circumstellar envelopes of some evolved stars

    CERN Document Server

    Diep, P N; Nhung, P T; Tuan-Anh, P; Bertre, T Le; Winters, J M; Matthews, L D; Phuong, N T; Thao, N T; Darriulat, P

    2015-01-01

    Studies of the CO and HI radio emission of some evolved stars are presented using data collected by the IRAM Plateau de Bure interferometer and Pico Veleta telescope, the Nan\\c{c}ay Radio Telescope and the JVLA and ALMA arrays. Approximate axial symmetry of the physical and kinematic properties of the circumstellar envelope (CSE) are observed in CO emission, in particular, from RS Cnc, EP Aqr and the Red Rectangle. A common feature is the presence of a bipolar outflow causing an enhanced wind velocity in the polar directions. HI emission extends to larger radial distances than probed by CO emission and displays features related to the interaction between the stellar outflow and interstellar matter. With its unprecedented sensitivity, FAST will open a new window on such studies. Its potential in this domain is briefly illustrated.

  3. Photodissociation and chemistry of N$_2$ in the circumstellar envelope of carbon-rich AGB stars

    CERN Document Server

    Li, Xiaohu; Walsh, Catherine; Heays, Alan N; van Dishoeck, Ewine F

    2014-01-01

    The envelopes of AGB stars are irradiated externally by ultraviolet photons; hence, the chemistry is sensitive to the photodissociation of N$_2$ and CO, which are major reservoirs of nitrogen and carbon, respectively. The photodissociation of N$_2$ has recently been quantified by laboratory and theoretical studies. Improvements have also been made for CO photodissociation. For the first time, we use accurate N$_2$ and CO photodissociation rates and shielding functions in a model of the circumstellar envelope of the carbon-rich AGB star, IRC +10216. We use a state-of-the-art chemical model of an AGB envelope, the latest CO and N$_2$ photodissociation data, and a new method for implementing molecular shielding functions in full spherical geometry with isotropic incident radiation. We compare computed column densities and radial distributions of molecules with observations. The transition of N$_2$ $\\to$ N (also, CO $\\to$ C $\\to$ C$^+$) is shifted towards the outer envelope relative to previous models. This leads...

  4. Circumstellar discs in X/gamma-ray binaries: first results from the Echelle spectrograph

    CERN Document Server

    Zamanov, R; Martí, J

    2015-01-01

    Here we report our first spectral observations of Be/X-ray and gamma-ray binaries obtained with the new Echelle spectrograph of the National Astronomical Observatory Rozhen. For four objects (LSI+61303, gamma Cas, MWC 148, 4U 2206+54), we report the parameters and estimate the sizes of their circumstellar discs using different emission lines (H-alpha, H-beta, H-gamma, HeI and FeII). For MWC 148, we find that the compact object goes deeply through the disc. The flank inflections of H-alpha can be connected with inner ring formed at the periastron passage or radiation transfer effects. We point out an intriguing similarity between the optical emission lines of the $\\gamma$-ray binary MWC 148 and the well known Be star $\\gamma$ Cas.

  5. First correlation between compact object and circumstellar disk in the Be/X-ray binaries

    CERN Document Server

    Zamanov, R K

    2000-01-01

    A remarkable correlation between the H-alpha emission line and the radio behaviour of LSI+61 303 (V615 Cas, GT 0236+610) over its 4 yr modulation is discovered. The radio outburst peak is shifted by a quarter of the 4 yr modulation period (about 400 days) with respect to the equivalent width of the H-alpha emission line variability. The onset of the LSI+61 303 radio outbursts varies in phase with the changes of the H-alpha emission line, at least during the increase of H-alpha equivalent width. This is the first clear correlation between the emission associated to the compact object and the Be circumstellar disk in a Be/X-ray binary system.

  6. Radiative Transfer Modeling of Passive Circumstellar Disks: Application to HR4796A

    CERN Document Server

    Currie, T; Henning, T; Furlan, E; Herter, T; Henning, Th.

    2003-01-01

    We present a radiative transfer model which computes the spectral energy distribution of a passive, irradiated, circumstellar disk, assuming the grains are in radiative equilibrium. Dependence on radial density profile, grain temperature estimation, and optical depth profiles on the output SED are discussed. The bist fit model for HR4796A has a minimum and maximum spherical grain size of 2.2 and 1000 \\mu$m respectively, a size distribution slightly steeper than the "classical" -3.5 MRN power law, grains composed of silicates, trolite, ice, and organics and a peak radial density of 1.0 x 10^-17 g cm^-2 at 70 AU, yielding a disk mass of roughly 2 M_{oplus}$.

  7. The effect of magnetic fields on the formation of circumstellar discs around young stars

    CERN Document Server

    Price, Daniel J

    2007-01-01

    We present first results of our simulations of magnetic fields in the formation of single and binary stars using a recently developed method for incorporating Magnetohydrodynamics (MHD) into the Smoothed Particle Hydrodynamics (SPH) method. An overview of the method is presented before discussing the effect of magnetic fields on the formation of circumstellar discs around young stars. We find that the presence of magnetic fields during the disc formation process can lead to significantly smaller and less massive discs which are much less prone to gravitational instability. Similarly in the case of binary star formation we find that magnetic fields, overall, suppress fragmentation. However these effects are found to be largely driven by magnetic pressure. The relative importance of magnetic tension is dependent on the orientation of the field with respect to the rotation axis, but can, with the right orientation, lead to a dilution of the magnetic pressure-driven suppression of fragmentation.

  8. An efficient algorithm for two-dimensional radiative transfer in axisymmetric circumstellar envelopes and disks

    CERN Document Server

    Dullemond, C P

    2000-01-01

    We present an algorithm for two-dimensional radiative transfer in axisymmetric, circumstellar media. The formal integration of the transfer equation is performed by a generalization of the short characteristics (SC) method to spherical coordinates. Accelerated Lambda Iteration (ALI) and Ng's algorithm are used to converge towards a solution. By taking a logarithmically spaced radial coordinate grid, the method has the natural capability of treating problems that span several decades in radius, in the most extreme case from the stellar radius up to parsec scale. Flux conservation is guaranteed in spherical coordinates by a particular choice of discrete photon directions and a special treatment of nearly-radially outward propagating radiation. The algorithm works well from zero up to very high optical depth, and can be used for a wide variety of transfer problems, including non-LTE line formation, dust continuum transfer and high temperature processes such as compton scattering. In this paper we focus on multip...

  9. Stellar occultation of polarized light from circumstellar electrons. I - Flat envelopes viewed edge on

    Science.gov (United States)

    Brown, John C.; Fox, Geoffrey K.

    1989-01-01

    The depolarizing and occultation effects of a finite spherical light source on the polarization of light Thomson-scattered from a flat circumstellar envelope seen edge-on are analyzed. The analysis shows that neglect of the finite size of the light source leads to a gross overestimate of the polarization for a given disk geometry. By including occultation and depolarization, it is found that B-star envelopes are necessarily highly flattened disk-type structures. For a disk viewed edge-on, the effect of occultation reduces the polarization more than the inclusion of the depolarization factor alone. Analysis of a one-dimensional plume leads to a powerful technique that permits the electron density distribution to be explicitly obtained from the polarimetric data.

  10. H12CN and H13CN excitation analysis in the circumstellar outflow of R Sculptoris

    Science.gov (United States)

    Saberi, M.; Maercker, M.; De Beck, E.; Vlemmings, W. H. T.; Olofsson, H.; Danilovich, T.

    2017-03-01

    Context. The 12CO/13CO isotopologue ratio in the circumstellar envelope (CSE) of asymptotic giant branch (AGB) stars has been extensively used as the tracer of the photospheric 12C/13C ratio. However, spatially-resolved ALMA observations of R Scl, a carbon rich AGB star, have shown that the 12CO/13CO ratio is not consistent over the entire CSE. Hence, it can not necessarily be used as a tracer of the 12C/13C ratio. The most likely hypothesis to explain the observed discrepancy between the 12CO/13CO and 12C/13C ratios is CO isotopologue selective photodissociation by UV radiation. Unlike the CO isotopologue ratio, the HCN isotopologue ratio is not affected by UV radiation. Therefore, HCN isotopologue ratios can be used as the tracer of the atomic C ratio in UV irradiated regions. Aims: We aim to present ALMA observations of H13CN(4-3) and APEX observations of H12CN(2-1), H13CN(2-1, 3-2) towards R Scl. These new data, combined with previously published observations, are used to determine abundances, ratio, and the sizes of line-emitting regions of the aforementioned HCN isotopologues. Methods: We have performed a detailed non-LTE excitation analysis of circumstellar H12CN(J = 1-0, 2-1, 3-2, 4-3) and H13CN(J = 2-1, 3-2, 4-3) line emission around R Scl using a radiative transfer code based on the accelerated lambda iteration (ALI) method. The spatial extent of the molecular distribution for both isotopologues is constrained based on the spatially resolved H13CN(4-3) ALMA observations. Results: We find fractional abundances of H12CN/H2 = (5.0 ± 2.0) × 10-5 and H13CN/H2 = (1.9 ± 0.4) × 10-6 in the inner wind (r ≤ (2.0 ± 0.25) ×1015 cm) of R Scl. The derived circumstellar isotopologue ratio of H12CN/H13CN = 26.3 ± 11.9 is consistent with the photospheric ratio of 12C/13C 19 ± 6. Conclusions: We show that the circumstellar H12CN/H13CN ratio traces the photospheric 12C/13C ratio. Hence, contrary to the 12CO/13CO ratio, the H12CN/H13CN ratio is not affected by UV

  11. AKARI observations of circumstellar dust in the globular clusters NGC104 and NGC362

    CERN Document Server

    Ita, Yoshifusa; Matsunaga, Noriyuki; Nakada, Yoshikazu; Matsuura, Mikako; Onaka, Takashi; Matsuhara, Hideo; Wada, Takehiko; Fujishiro, Naofumi; Ishihara, Daisuke; Kataza, Hirokazu; Kim, Woojung; Matsumoto, Toshio; Murakami, Hiroshi; Ohyama, Youichi; Usui, Fumihiko; Oyabu, Shinki; Sakon, Itsuki; Takagi, Toshinobu; Uemizu, Kazunori; Ueno, Munetaka; Watarai, Hidenori

    2007-01-01

    We report preliminary results of AKARI observations of two globular clusters, NGC104 and NGC362. Imaging data covering areas of about 10x10 arcmin^2 centered on the two clusters have been obtained with InfraRed Camera (IRC) at 2.4, 3.2, 4.1, 7.0, 9.0, 11.0, 15.0, 18.0 and 24.0 mu. We used F11/F2 and F24/F7 flux ratios as diagnostics of circumstellar dust emission. Dust emissions are mainly detected from variable stars obviously on the asymptotic giant branch, but some variable stars that reside below the tip of the first-ascending giant branch also show dust emissions. We found eight red sources with F24/F7 ratio greater than unity in NGC362. Six out of the eight have no 2MASS counterparts. However, we found no such source in NGC104.

  12. A Compact Circumstellar Shell as the Source of High--velocity Features in SN 2011fe

    CERN Document Server

    Mulligan, Brian W

    2015-01-01

    High--velocity features (HVF), especially of Ca II, are frequently seen in Type Ia supernovae observed prior to B-band maximum (Bmax). These HVF start at more than 25,000 km/s in the days after first light, and slow to about 18,000 km/s near Bmax. To recreate the Ca II near-infrared triplet (CaNIR) HVF in SN 2011fe, we consider the interaction between a Type Ia supernova and a compact circumstellar shell, employing a hydrodynamic 1-D simulation using FLASH. We generate synthetic spectra from the hydrodynamic results using syn++. We show that the CaNIR HVF and its velocity evolution is better explained by a supernova model interacting with a shell than a model without a shell, and briefly discuss the implications for progenitor models.

  13. Ground-based near-infrared imaging of the HD141569 circumstellar disk

    CERN Document Server

    Boccaletti, A; Marchis, F; Hanh, J

    2003-01-01

    We present the first ground-based near-infrared image of the circumstellar disk around the post-Herbig Ae/Be star HD141569A initially detected with the HST. Observations were carried out in the near-IR (2.2 $\\mu$m) at the Palomar 200-inch telescope using the adaptive optics system PALAO. The main large scale asymmetric features of the disk are detected on our ground-based data. In addition, we measured that the surface brightness of the disk is slightly different than that derived by HST observations (at 1.1 $\\mu$m and 1.6 $\\mu$m). We interpret this possible color-effect in terms of dust properties and derive a minimal

  14. THE GAS/DUST RATIO OF CIRCUMSTELLAR DISKS: TESTING MODELS OF PLANETESIMAL FORMATION

    Energy Technology Data Exchange (ETDEWEB)

    Horne, David [New York Center for Astrobiology, Rensselaer Polytechnic Institute, 110 Eighth Street, Troy, NY 12180-3590 (United States); Gibb, Erika [Department of Physics and Astronomy, University of Missouri-St. Louis, 8001 Natural Bridge Road, St. Louis, MO 63121 (United States); Rettig, Terrence W.; Tilley, David; Balsara, Dinshaw [Center for Astrophysics, University of Notre Dame, Notre Dame, IN 46556 (United States); Brittain, Sean [Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-0978 (United States)

    2012-07-20

    We present high-resolution, near-infrared NIRSPEC observations of CO absorption toward six class II T Tauri stars: AA Tau, DG Tau, IQ Tau, RY Tau, CW Tau, and Haro 6-5b. {sup 12}CO overtone absorption lines originating from the circumstellar disk of each object were used to calculate line-of-sight gas column densities toward each source. We measured the gas/dust ratio as a function of disk inclination, utilizing measured visual extinctions and inclinations for each star. The majority of our sources show further evidence for a correlation between the gas/dust column density ratio and disk inclination similar to that found by Rettig et al.

  15. Circular Polarization of Water Masers in the Circumstellar Envelopes of Late Type Stars

    CERN Document Server

    Vlemmings, W H T; Van Langevelde, H J

    2002-01-01

    We present circular polarization measurements of circumstellar H_2O masers. The circular polarization detected in the (6_{16}-5_{23}) rotational transition of the H_{2}O maser can be attributed to Zeeman splitting in the intermediate temperature and density regime. The magnetic fields are derived using a general, LTE Zeeman analysis as well as a full radiative transfer method (non-LTE), which includes a treatment of all hyperfine components simultaneously as well as the effects of saturation and unequal populations of the magnetic substates. The differences and relevances of these interpretations are discussed extensively. The field strengths are compared with previous detections of the magnetic field on the SiO and OH masers. We show that the magnetic pressure dominates the thermal pressure by a factor of 20 or more.

  16. A SYMMETRIC INNER CAVITY IN THE HD 141569A CIRCUMSTELLAR DISK

    Energy Technology Data Exchange (ETDEWEB)

    Mazoyer, J.; Choquet, É.; Perrin, M. D.; Pueyo, L.; Debes, J. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore MD 21218 (United States); Boccaletti, A. [LESIA, Observatoire de Paris, CNRS, UPMC and Univ. Paris Diderot, 5 place Jules Janssen, F-92190 Meudon (France); Augereau, J.-C.; Lagrange, A.-M. [Univ. Grenoble Alpes, Institut de Planétologie et d´Astrophysique (IPAG) F-38000 Grenoble (France); Wolff, S. G., E-mail: jmazoyer@stsci.edu [Johns Hopkins University, 3400 North Charles Street, Baltimore, MD (United States)

    2016-02-20

    Some circumstellar disks, called transitional or hybrid disks, present characteristics of both protoplanetary disks (significant amount of gas) and debris disks (evolved structures around young main-sequence stars, composed of second generation dust, from collisions between planetesimals). Therefore, they are ideal astrophysical laboratories to witness the last stages of planet formation. The circumstellar disk around HD 141569A was intensively observed and resolved in the past from space, but also from the ground. However, the recent implementation of high contrast imaging systems has opened up new opportunities to re-analyze this object. We analyzed Gemini archival data from the Near-infrared Coronagraphic Imager obtained in 2011 in the H band, using several angular differential imaging techniques (classical ADI, LOCI, KLIP). These images reveal the complex structures of this disk with an unprecedented resolution. We also include archival Hubble Space Telescope images as an independent data set to confirm these findings. Using an analysis of the inner edge of the disk, we show that the inner disk is almost axisymmetrical. The measurement of an offset toward the east observed by previous authors is likely due to the fact that the eastern part of this disk is wider and more complex in substructure. Our precise reanalysis of the eastern side shows several structures, including a splitting of the disk and a small finger detached from the inner edge to the southeast. Finally, we find that the arc at 250 AU is unlikely to be a spiral, at least not at the inclination derived from the first ring, but instead could be interpreted as a third belt at a different inclination. If the very symmetrical inner disk edge is carved by a companion, the data presented here put additional constraints on its position. The observed very complex structures will be confirmed by the new generation of coronagraphic instrument (GPI, SPHERE). However, a full understanding of this system will

  17. Modelling the circumstellar medium in RS Ophiuchi and its link to Type Ia supernovae

    Science.gov (United States)

    Booth, R. A.; Mohamed, S.; Podsiadlowski, Ph.

    2016-03-01

    Recent interpretations of narrow, variable absorption lines detected in some Type Ia supernovae suggest that their progenitors are surrounded by dense, circumstellar material. Similar variations detected in the symbiotic recurrent nova system RS Oph, which undergoes thermonuclear outbursts every 20 years, making it an ideal candidate to investigate the origin of these lines. To this end, we present simulations of multiple mass transfer-nova cycles in RS Oph. We find that the quiescent mass transfer produces a dense, equatorial outflow, i.e. concentrated towards the binary orbital plane, and an accretion disc forms around the white dwarf. The interaction of a spherical nova outburst with these aspherical circumstellar structures produces a bipolar outflow, similar to that seen in Hubble Space Telescope imaging of the 2006 outburst. In order to produce an ionization structure that is consistent with observations, a mass-loss rate of 5 × 10-7 M⊙ yr-1 from the red giant is required. The simulations also produce a polar accretion flow, which may explain the broad wings of the quiescent H line and hard X-rays. By comparing simulated absorption line profiles to observations of the 2006 outburst, we are able to determine which components arise in the wind and which are due to the novae. We explore the possible behaviour of absorption line profiles as they may appear should a supernova occur in a system like RS Oph. Our models show similarities to supernovae like SN 2006X, but require a high mass-loss rate, dot{M} ˜ 10^{-6}-10-5 M⊙ yr-1, to explain the variability in SN 2006X.

  18. The chemical composition of the circumstellar envelopes around yellow hypergiant stars

    Science.gov (United States)

    Quintana-Lacaci, G.; Bujarrabal, V.; Castro-Carrizo, A.; Alcolea, J.

    2007-08-01

    Context: The yellow hypergiant stars (YHGs) are extremely luminous and massive objects whose general properties are poorly known. Only two of this kind of star show massive circumstellar envelopes, IRC +10420 and AFGL 2343. Aims: We aim to study the chemistry of the circumstellar envelopes around these two sources, by comparison with well known AGB stars and protoplanetary nebulae. We also estimate the abundances of the observed molecular species. Methods: We have performed single-dish observations of different transitions for twelve molecular species. We have compared the ratio of the intensities of the molecular transitions and of the estimated abundances in AFGL 2343 and IRC +10420 with those in O-rich and C-rich AGB stars and protoplanetary nebulae. Results: Both YHGs, AFGL 2343, and IRC +10420, have been found to have an O-rich chemistry similar to that in O-rich AGB stars, though for AFGL 2343 the emission of most molecules compared with 13CO lines is relatively weak. Clear differences with the other evolved sources appear when we compare the line intensity corrected for distance and the profile widths which are, respectively, very intense and very wide in YHGs. The abundances obtained for IRC +10420 agree with those found in AGB stars, but in general those found in AFGL 2343, except for 13CO, are too low. This apparently low molecular abundance in AFGL 2343 could be due to the fact that these molecules are present only in an inner region of the shell where the mass is relatively low. Based on observations carried out with the IRAM Pico Veleta 30 m telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). Appendix A is only available in electronic form at http://www.aanda.org

  19. Nearby Supernova Factory Observations of SN 2005gj: Another TypeIa Supernova in a Massive Circumstellar Envelope

    Energy Technology Data Exchange (ETDEWEB)

    Aldering, G.; Antilogus, P.; Bailey, S.; Baltay, C.; Bauer, A.; Blanc, N.; Bongard, S.; Copin, Y.; Gangler, E.; Gilles, S.; Kessler, R.; Kocevski, D.; Lee, B.C.; Loken, S.; Nugent, P.; Pain, R.; Pecontal, E.; Pereira, R.; Perlmutter, S.; Rabinowitz, D.; Rigaudier, G.; Scalzo, R.; Smadja, G.; Thomas, R.C.; Wang, L.; Weaver, B.A.; Rabinowitz, D.; Bauer, A.

    2006-06-01

    We report the independent discovery and follow-up observations of supernova 2005gj by the Nearby Supernova Factory. This is the second confirmed case of a ''hybrid'' Type Ia/IIn supernova, which like the prototype SN 2002ic, we interpret as the explosion of a white dwarf interacting with a circumstellar medium. Our early-phase photometry of SN 2005gj shows that the strength of the interaction between the supernova ejecta and circumstellar material is much stronger than for SN 2002ic. Our .rst spectrum shows a hot continuum with broad and narrow H{alpha} emission. Later spectra, spanning over 4 months from outburst, show clear Type Ia features combined with broad and narrow H{gamma}, H{beta},H{alpha} and He I {lambda}{lambda}5876,7065 in emission. At higher resolution, P Cygni profiles are apparent. Surprisingly, we also observe an inverted P Cygni profile for [O III] {lambda}5007. We find that the lightcurve and measured velocity of the unshocked circumstellar material imply mass loss as recently as 8 years ago. This is in contrast to SN 2002ic, for which an inner cavity in the circumstellar material was inferred. Within the context of the thin-shell approximation, the early lightcurve is well-described by a flat radial density profile for the circumstellar material. However, our decomposition of the spectra into Type Ia and shock emission components allows for little obscuration of the supernova, suggesting an aspherical or clumpy distribution for the circumstellar material. We suggest that the emission line velocity profiles arise from electron scattering rather than the kinematics of the shock. This is supported by the inferred high densities, and the lack of evidence for evolution in the line widths. Ground- and space-based photometry, and Keck spectroscopy, of the host galaxy are used to ascertain that the host galaxy has low metallicity (Z/Z{sub {circle_dot}} < 0.3; 95% confidence) and that this galaxy is undergoing a significant star

  20. Polarimetry with the Gemini Planet Imager: Methods, Performance at First Light, and the Circumstellar Ring around HR 4796A

    CERN Document Server

    Perrin, Marshall D; Millar-Blanchaer, Max; Fitzgerald, Michael P; Graham, James R; Wiktorowicz, Sloane J; Kalas, Paul G; Macintosh, Bruce; Bauman, Brian; Cardwell, Andrew; Chilcote, Jeffrey; De Rosa, Robert J; Dillon, Daren; Doyon, René; Dunn, Jennifer; Gavel, Donald; Goodsell, Stephen; Hartung, Markus; Hibon, Pascale; Ingraham, Patrick; Kerley, Daniel; Konapacky, Quinn; Larkin, James E; Maire, Jérôme; Marchis, Franck; Marois, Christian; Mittal, Tushar; Morzinski, Katie M; Oppenheimer, B R; Palmer, David W; Patience, Jennifer; Poyneer, Lisa; Pueyo, Laurent; Rantakyrö, Fredrik T; Sadakuni, Naru; Saddlemyer, Leslie; Savransky, Dmitry; Soummer, Rémi; Sivaramakrishnan, Anand; Song, Inseok; Thomas, Sandrine; Wallace, J Kent; Wang, Jason J; Wolff, Schuyler G

    2014-01-01

    We present the first results from the polarimetry mode of the Gemini Planet Imager (GPI), which uses a new integral field polarimetry architecture to provide high contrast linear polarimetry with minimal systematic biases between the orthogonal polarizations. We describe the design, data reduction methods, and performance of polarimetry with GPI. Point spread function subtraction via differential polarimetry suppresses unpolarized starlight by a factor of over 100, and provides sensitivity to circumstellar dust reaching the photon noise limit for these observations. In the case of the circumstellar disk around HR 4796A, GPI's advanced adaptive optics system reveals the disk clearly even prior to PSF subtraction. In polarized light, the disk is seen all the way in to its semi-minor axis for the first time. The disk exhibits surprisingly strong asymmetry in polarized intensity, with the west side >9 times brighter than the east side despite the fact that the east side is slightly brighter in total intensity. Ba...

  1. An Infrared Diffuse Circumstellar Band? The Unusual 1.5272 Micron DIB In the Red Square Nebula

    CERN Document Server

    Zasowski, G; Whelan, D G; Miroshnichenko, A S; Hernández, D A García; Majewski, S R

    2015-01-01

    The molecular carriers of the ubiquitous absorption features called the diffuse interstellar bands (DIBs) have eluded identification for many decades, in part because of the enormous parameter space spanned by the candidates and the limited set of empirical constraints afforded by observations in the diffuse interstellar medium. Detection of these features in circumstellar regions, where the environmental properties are more easily measured, is thus a promising approach to understanding the chemical nature of the carriers themselves. Here, using high resolution spectra from the APOGEE survey, we present an analysis of the unusually asymmetric 1.5272 micron DIB feature along the sightline to the Red Square Nebula and demonstrate the likely circumstellar origin of about half of the DIB absorption in this line of sight. This interpretation is supported both by the velocities of the feature components and by the ratio of foreground to total reddening along the line of sight. The Red Square Nebula sightline offers...

  2. Lines of Circumstellar C2, CN, and CH$^+$ in the Optical Spectra of Post-Agb Stars

    CERN Document Server

    Bakker, E J; Van Dishoeck, E F; Bakker, Eric J.; Lambert, David L.; Dishoeck, Ewine F. van

    1996-01-01

    Recent optical spectra of post-AGB stars show the presence of C2, CN, and CH+ originating in the circumstellar shell. We present here new, higher resolution spectra which provide constraints on the physical parameters and information on the line profiles. An empirical curve of growth for the C2 Phillips and CN Red system lines in the spectrum of HD 56126 yields b = 0.50 (+0.59, -0.23) km/s. CH+ (0,0) emission lines in the spectrum of the Red Rectangle have been resolved with a FWHM approx 8.5 pm 0.8 km/s. The circumstellar CN lines of IRAS 08005--2356 are resolved into two separate components with a velocity separation of Delta v = 5.7 pm 2.0 km/s. The line profiles of CN of HD 235858 have not been resolved.

  3. SO and SO2 in mass-loss envelopes of red giants - Probes of nonequilibrium circumstellar chemistry and mass-loss rates

    Science.gov (United States)

    Sahai, Raghvendra; Wannier, Peter G.

    1992-01-01

    SO emission was searched for in one or more of four transitions toward 23 oxygen-rich red giant or supergiant stars and one S star, selected primarily on the basis of their nonmaser SiO emission. SO was detected in a total of 14 circumstellar envelopes, 13 of which are new detections. The circumstellar abundance of SO (and SO2) is significantly enhanced over the equilibrium value achieved in the photospheres of these stars. In general, the SO abundances are significantly larger than predicted by nonequilibrium circumstellar chemistry models. Sulfur cannot be significantly depleted onto circumstellar grains, and probably exists as H2S (and/or SH) in the inner regions of the envelopes. The SO rotational-level population in most circumstellar envelopes observed is characterized by excitation temperatures less than or approximately equal to 50 K. The circumstellar abundance of SO2 is comparable to, or larger than, that of SO, ruling out the 'large' value adopted for the unshielded photodissociation rate for SO2 in recent models.

  4. Resolving the inner regions of the HD97048 circumstellar disk with VLT/NACO polarimetric differential imaging

    CERN Document Server

    Quanz, Sascha P; Apai, Daniel; Wolf, Sebastian; Henning, Thomas

    2011-01-01

    Circumstellar disks are the cradles of planetary systems and their physical and chemical properties directly influence the planet formation process. As most planets supposedly form in the inner disk regions, i.e., within a few tens of AU, it is crucial to study circumstellar disk on these scales to constrain the conditions for planet formation. Our aims are to characterize the inner regions of the circumstellar disk around the young Herbig Ae/Be star HD97048 in polarized light. We use VLT/NACO to observe HD97048 in polarimetric differential imaging (PDI) mode in the H and Ks band. We spatially resolve the disk around HD97048 in polarized flux in both filters on scales between ~0.1"-1.0" corresponding to the inner ~16-160 AU. Fitting isophots to the flux calibrated H-band image between 13 - 14 mag/arcsec^2 and 14 - 15 mag/arcsec^2 we derive a apparent disk inclination angle of 34+-5 deg and 47+-2 deg, respectively. The disk position angle in both brightness regimes is almost identical and roughly 80 deg. Along...

  5. Spectroscopic Evolution of Disintegrating Planetesimals: Minutes to Months Variability in the Circumstellar Gas Associated with WD 1145+017

    CERN Document Server

    Redfield, Seth; Cauley, P Wilson; Parsons, Steven G; Gaensicke, Boris T; Duvvuri, Girish

    2016-01-01

    With the recent discovery of transiting planetary material around WD 1145+017, a critical target has been identified that links the evolution of planetary systems with debris disks and their accretion onto the star. We present a series of observations, five epochs over a year, taken with Keck and the VLT, which for the first time show variability of circumstellar absorption in the gas disk surrounding WD 1145+017 on timescales of minutes to months. Circumstellar absorption is measured in more than 250 lines of 14 ions among ten different elements associated with planetary composition, e.g., O, Mg, Ca, Ti, Cr, Mn, Fe, Ni. Broad circumstellar gas absorption with a velocity spread of 225 km/s is detected, but over the course of a year blue shifted absorption disappears while redshifted absorption systematically increases. A correlation of equivalent width and oscillator strength indicates that the gas is not highly optically thick (median tau approximately 2). We discuss simple models of an eccentric disk couple...

  6. Bursting SN 1996cr's Bubble: Hydrodynamic and X-ray Modeling of its Circumstellar Medium

    CERN Document Server

    Dwarkadas, Vikram V; Bauer, Franz

    2010-01-01

    SN1996cr is one of the five closest SNe to explode in the past 30 years. Due to its fortuitous location in the Circinus Galaxy at ~ 3.7 Mpc, there is a wealth of recently acquired and serendipitous archival data available to piece together its evolution over the past decade, including a recent 485 ks Chandra HETG spectrum. In order to interpret this data, we have explored hydrodynamic simulations, followed by computations of simulated spectra and light curves under non-equilibrium ionization conditions, and directly compared them to the observations. Our simulated spectra manage to fit both the X-ray continuum and lines at 4 epochs satisfactorily, while our computed light curves are in good agreement with additional flux-monitoring data sets. These calculations allow us to infer the nature and structure of the circumstellar medium, the evolution of the SN shock wave, and the abundances of the ejecta and surrounding medium. The data imply that SN 1996cr exploded in a low-density medium before interacting with ...

  7. Detection of warm molecular hydrogen in the circumstellar disk around the Herbig Ae star HD97048

    CERN Document Server

    Martin-Zaidi, C; Pantin, E; Habart, E

    2007-01-01

    We present high resolution spectroscopic mid-infrared observations of the circumstellar disk around the Herbig Ae star HD97048 with the VLT Imager and Spectrometer for the mid-InfraRed (VISIR). We detect the S(1) pure rotational line of molecular hydrogen (H2) at 17.035 microns arising from the disk around the star. This detection reinforces the claim that HD97048 is a young object surrounded by a flared disk at an early stage of evolution. The emitting warm gas is located within the inner 35 AU of the disk. The line-to-continuum flux ratio is much higher than expected from models of disks at local thermodynamics equilibrium. We investigate the possible physical conditions, such as a gas-to-dust mass ratio higher than 100 and different excitation mechanisms of molecular hydrogen (X-ray heating, shocks, ...) in order to explain the detection. We tentatively estimate the mass of warm gas to be in the range from 0.01 to nearly 1 Jupiter Mass. Further observations are needed to better constrain the excitation mec...

  8. Circumstellar HI and CO around the carbon stars V1942 Sgr and V CrB

    CERN Document Server

    Libert, Y; Thum, C; Winters, J M; Matthews, L D; Bertre, T Le

    2009-01-01

    Context. The majority of stars that leave the main sequence are undergoing extensive mass loss, in particular during the asymptotic giant branch (AGB) phase of evolution. Observations show that the rate at which this phenomenon develops differs highly from source to source, so that the time-integrated mass loss as a function of the initial conditions (mass, metallicity, etc.) and of the stage of evolution is presently not well understood. Aims. We are investigating the mass loss history of AGB stars by observing the molecular and atomic emissions of their circumstellar envelopes. Methods. In this work we have selected two stars that are on the thermally pulsing phase of the AGB (TP-AGB) and for which high quality data in the CO rotation lines and in the atomic hydrogen line at 21 cm could be obained. Results. V1942 Sgr, a carbon star of the Irregular variability type, shows a complex CO line profile that may originate from a long-lived wind at a rate of ~ 10^-7 Msol/yr, and from a young (< 10^4 years) fast...

  9. A Low-Mass H2 Component to the AU Microscopii Circumstellar Disk

    CERN Document Server

    France, Kevin; Lupu, Roxana E; Redfield, Seth; Feldman, Paul D

    2007-01-01

    We present a determination of the molecular gas mass in the AU Microscopii circumstellar disk. Direct detection of a gas component to the AU Mic disk has proven elusive, with upper limits derived from ultraviolet absorption line and submillimeter CO emission studies. Fluorescent emission lines of H2, pumped by the OVI 1032 resonance line through the C-X (1 -- 1) Q(3) 1031.87 \\AA\\ transition, are detected by the Far Ultraviolet Spectroscopic Explorer. These lines are used to derive the H2 column density associated with the AU Mic system. The derived column density is in the range N(H2) = 1.9 x 10^{17} - 2.8 x 10^{15} cm^{-2}, roughly two orders of magnitude lower than the upper limit inferred from absorption line studies. This range of column densities reflects the range of H2 excitation temperature consistent with the observations, T(H2) = 800 -- 2000 K, derived from the presence of emission lines excited by OVI in the absence of those excited by LyA. Within the observational uncertainties, the data are consi...

  10. Radiation-Hydrodynamic Models of the evolving Circumstellar Medium around Massive Stars

    CERN Document Server

    Toalá, J A

    2011-01-01

    We study the evolution of the interstellar and circumstellar media around massive stars (M > 40M_{\\odot}) from the main sequence through to the Wolf-Rayet stage by means of radiationhydrodynamic simulations. We use publicly available stellar evolution models to investigate the different possible structures that can form in the stellar wind bubbles around Wolf-Rayet stars. We find significant differences between models with and without stellar rotation, and between models from different authors. More specifically, we find that the main ingredients in the formation of structures in the Wolf-Rayet wind bubbles are the duration of the Red Supergiant (or Luminous Blue Variable) phase, the amount of mass lost, and the wind velocity during this phase, in agreement with previous authors. Thermal conduction is also included in our models. We find that main-sequence bubbles with thermal conduction are slightly smaller, due to extra cooling which reduces the pressure in the hot, shocked bubble, but that thermal conducti...

  11. Hubble imaging of V1331 Cygni: Proper motion study of its circumstellar structures

    CERN Document Server

    Choudhary, Arpita; Linz, Hendrik

    2016-01-01

    The young star V1331 Cyg received previous attention because it is surrounded by an optical, arc-like reflection nebula. V1331 Cyg is commonly considered to be a candidate for an object that has undergone an FU-Ori (FUOR) the outbreak in the past. This in turn could lead to a time-varying appearance of the dusty arcs that may be revealed by multi-epoch imaging. In particular, a radial colour analysis of the dust arcs can then be attempted to check whether radial grain size distribution was modified by a previous FUOR wind. Second-epoch imaging of V1331 Cyg was obtained by us in 2009 using the Hubble Space Telescope (HST). By comparing this to archival HST data from 2000, we studied the time evolution of the circumstellar nebulae. After a point spread function subtraction using model point spread functions, we used customised routines to perform a proper motion analysis. The nebula expansion was first derived by deconvolving and correlating the two-epoch radial brightness profiles. Additional data from other f...

  12. ALMA Observations of Circumstellar Disks in the Upper Scorpius OB Association

    CERN Document Server

    Barenfeld, Scott A; Ricci, Luca; Isella, Andrea

    2016-01-01

    We present ALMA observations of 106 G-, K-, and M-type stars in the Upper Scorpius OB Association hosting circumstellar disks. With these data, we measure the 0.88 mm continuum and $^{12}$CO $J = 3-2$ line fluxes of disks around low mass ($0.14-1.66$ $M_{\\odot}$) stars at an age of 5-11 Myr. Of the 75 primordial disks in the sample, 53 are detected in the dust continuum and 26 in CO. Of the 31 disks classified as debris/evolved transitional disks, 5 are detected in the continuum and none in CO. The lack of CO emission in approximately half of the disks with detected continuum emission can be explained if CO is optically thick but has a compact emitting area ($\\lesssim 40$ AU), or if the CO is heavily depleted by a factor of at least $\\sim1000$ relative to interstellar medium abundances and is optically thin. The continuum measurements are used to estimate the dust mass of the disks. We find a correlation between disk dust mass and stellar host mass consistent with a power-law relation of $M_{dust}\\propto M_*^...

  13. Structure and Composition of Two Transitional Circumstellar Disks in Corona Australis

    CERN Document Server

    Hughes, A M; Wilner, D J; Meyer, M R; Carpenter, J M; Qi, C; Hales, A S; Casassus, S; Hogerheijde, M R; Mamajek, E E; Wolf, S; Henning, T; Silverstone, M D

    2010-01-01

    The late stages of evolution of the primordial circumstellar disks surrounding young stars are poorly understood, yet vital to constrain theories of planet formation. We consider basic structural models for the disks around two ~10 Myr-old members of the nearby RCrA association, RX J1842.9-3532 and RX J1852.3-3700. We present new arcsecond-resolution maps of their 230 GHz continuum emission from the Submillimeter Array and unresolved CO(3-2) spectra from the Atacama Submillimeter Telescope Experiment. By combining these data with broadband fluxes from the literature and infrared fluxes and spectra from the catalog of the Formation and Evolution of Planetary Systems (FEPS) Legacy program on the Spitzer Space Telescope, we assemble a multiwavelength data set probing the gas and dust disks. Using the Monte Carlo radiative transfer code RADMC to model simultaneously the SED and millimeter continuum visibilities, we derive basic dust disk properties and identify an inner cavity of radius 16 AU in the disk around R...

  14. Physical properties of the supernova remnant expanding in a clumpy circumstellar medium

    Institute of Scientific and Technical Information of China (English)

    陈阳; 刘宁; 汪珍如

    1996-01-01

    Physical properties of the supernova remnant expanding in a dumpy circumstellar medium are studied. Taking into account the effect of cloud evaporation in the clumpy medium, it is found that the evolution and internal structure of supernova remnant in a clumpy medium of a power-law density distribution in the radius are generally serf-similar as long as the minus power-law index is in the range of about 0-3. In the case where the index equals -2, namely, the medium is composed of the inhomogeneous free stellar wind, based on the detailed hydrodynamic solution, the formulae, figures, and tables for describing the observable properties, such as the relative distribution of the remnant’s surface brightness, X-ray luminosity, the mass of X-ray-emitting gas, emission-measure-weighted mean temperature, infrared luminosity, and Ha luminosity, are provided. It is indicated that the evaporated matter may pile up near the center and the X-ray emission there is brighter than that near the limb when some parameters

  15. CARMA CO(J = 2 - 1) Observations of the Circumstellar Envelope of Betelgeuse

    CERN Document Server

    O'Gorman, Eamon; Brown, Joanna M; Brown, Alexander; Redfield, Seth; Richter, Matthew J; Requena-Torres, Miguel A

    2012-01-01

    We report radio interferometric observations of the 12C16O 1.3 mm J = 2-1 emission line in the circumstellar envelope of the M supergiant Alpha Ori and have detected and separated both the S1 and S2 flow components for the first time. Observations were made with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) interferometer in the C, D, and E antenna configurations. We obtain good u-v coverage (5-280 klambda) by combining data from all three configurations allowing us to trace spatial scales as small as 0.9\\arcsec over a 32\\arcsec field of view. The high spectral and spatial resolution C configuration line profile shows that the inner S1 flow has slightly asymmetric outflow velocities ranging from -9.0 km s-1 to +10.6 km s-1 with respect to the stellar rest frame. We find little evidence for the outer S2 flow in this configuration because the majority of this emission has been spatially-filtered (resolved out) by the array. We also report a SOFIA-GREAT CO(J= 12-11) emission line profile w...

  16. The circumstellar disc around the Herbig AeBe star HD169142

    CERN Document Server

    Dent, W R F; Osorio, M; Calvet, N; Anglada, G

    2006-01-01

    We present 7 mm and 3.5 cm wavelength continuum observations toward the Herbig AeBe star HD169142 performed with the Very Large Array (VLA) with an angular resolution of ~1". We find that this object exhibits strong (~4.4 mJy), unresolved (~1") 7 mm continuum emission, being one of the brightest isolated Herbig AeBe stars ever detected with the VLA at this wavelength. No emission is detected at 3.5 cm continuum, with a 3 sigma upper limit of ~0.08 mJy. From these values, we obtain a spectral index of ~2.5 in the 3.5 cm to 7 mm wavelength range, indicating that the observed flux density at 7mm is most likely dominated by thermal dust emission coming from a circumstellar disc. We use available photometric data from the literature to model the spectral energy distribution (SED) of this object from radio to near-ultraviolet frequencies. The observed SED can be understood in terms of an irradiated accretion disc with low mass accretion rate, 10^{-8} solar masses per year, surrounding a star with an age of ~10 Myr....

  17. High spatial resolution infrared imaging of L1551-IRS 5 - Direct observations of its circumstellar envelope

    Science.gov (United States)

    Moneti, Andrea; Forrest, William J.; Pipher, Judith L.; Woodward, Charles E.

    1988-01-01

    Images of L1551-IRS 5 were obtained at 1.65, 2.2, and 3.8 microns using the University of Rochester's Infrared Array Camera. It is found that IRS 5 is spatially resolved, and that it is elongated: the observed FWHM size of IRS 5 is 4.1 x 2.8 arcsec-squared at 2.2 microns. These observations are interpreted in terms of a flattened circumstellar envelope that is viewed from about 18 deg above its equatorial plane, a configuration that has been treated theoretically by Lefevre et al. In this model the central star is not seen directly, but only light scattered toward the observer from the visible polar region, where the envelope is thinnest, is observed. It is deduced that the envelope has a diameter of 1000 AU, a molecular hydrogen density of greater than or approximately equal to 4 x 10 to the 6th/cu cm, and a mass of greater than or approximately equal to 0.02 M solar mass, which results in an extinction of Av greater than about 33 mag to the central source.

  18. The circumstellar structure of the Be shell star phi Per. I. Data analysis

    Science.gov (United States)

    Štefl, S.; Hummel, W.; Rivinius, Th.

    2000-06-01

    We present new phase resolved observations of emission lines of the Be binary phi Per. Analyzing the orbital phase variations in the He I emission features we find strong arguments that the feature as a whole originates in the outer parts of the disk around the primary star. In addition to the He I 6678 and 5876 lines, the emission features with orbital phase variations were detected in three more He I lines. The observations are in agreement with the scenario of Poeckert and others, in which the outer parts of an axisymmetric disk are illuminated by the radiation of the secondary. The observations after 1996 are consistent with a growing global density inhomogeneity in the circumprimary disk as it occurs in disks of single Be stars. The combination of the illumination effect and the increasing density inhomogeneity make phi Per an ideal laboratory to study density perturbations of circumstellar disks of Be stars in more detail. Based on observations collected at the Ond\\v{r}ejov Observatory (of the Academy of Sciences of the Czech Republic), Heidelberg Observatory, German-Spanish Astronomical Center (DSAZ) - Calar Alto (operated by the Max-Plank-Institut für Astronomie Heidelberg jointly with the Spanish National Commission for Astronomy) and Observatoire de Haute-Provence (OHP; CNRS, France)}

  19. Line formation in Be star circumstellar disks Shear broadening, shell absorption, stellar obscuration and rotational parameter

    Science.gov (United States)

    Hummel, W.; Vrancken, M.

    2000-07-01

    We improve the theory of Horne & Marsh on shear broadening in accretion disks of CVs and adapt it to Be star circumstellar disks. Stellar obscuration and shell absorption are taken into account in detail. It is shown that shell absorption is already present in those emission lines where the central depression does not drop below the stellar continuum. The model profiles are fitted to observed symmetric Hα net emission lines with low equivalent width. The derived disk radii range from Rd = 5.3 R_* to Rd = 18 R_* and the surface emissivity varies as ~ R-m with 1.6 (1)/(2) with the optically thick Hα profile of HR 5440 rules out the range of j>(1)/(2). This can be understood by the lack of velocity shear in the outer disk regions. We conclude that Keplerian rotation (j=(1)/(2)) is a valid approximation. Based on observations collected at the German-Spanish Astronomical Center (DSAZ), Calar Alto, operated by the Max-Plank-Institut für Astronomie Heidelberg jointly with the Spanish National Commission for Astronomy. Based on observations collected at the Observatoire de Haute-Provence (OHP), CNRS, France.

  20. Circum-stellar medium around rotating massive stars at solar metallicity

    CERN Document Server

    Georgy, Cyril; Folini, Doris; Bykov, Andrei; Marcowith, Alexandre; Favre, Jean M

    2013-01-01

    Aims. Observations show nebulae around some massive stars but not around others. If observed, their chemical composition is far from homogeneous. Our goal is to put these observational features into the context of the evolution of massive stars and their circumstellar medium (CSM) and, more generally, to quantify the role of massive stars for the chemical and dynamical evolution of the ISM. Methods. Using the A-MAZE code, we perform 2d-axisymmetric hydrodynamical simulations of the evolution of the CSM, shaped by stellar winds, for a whole grid of massive stellar models from 15 to 120 Msun and following the stellar evolution from the zero-age main-sequence to the time of supernova explosion. In addition to the usual quantities, we also follow five chemical species: H, He, C, N, and O. Results. We show how various quantities evolve as a function of time: size of the bubble, position of the wind termination shock, chemical composition of the bubble, etc. The chemical composition of the bubble changes considerab...

  1. Supernova PTF 09UJ: A Possible Shock Breakout from a Dense Circumstellar Wind

    Science.gov (United States)

    Ofek, E. O.; Rabinak, I.; Neill, J. D.; Arcavi, I.; Cenko, S. B.; Waxman, E.; Kulkarni, S. R.; Gal-Yam, A.; Nugent, P. E.; Bildsten, L.; Bloom, J. S.; Filippenko, A. V.; Forster, K.; Howell, D. A.; Jacobsen, J.; Kasliwal, M. M.; Law, N.; Martin, C.; Poznanski, D.; Quimby, R. M.; Shen, K. J.; Sullivan, M.; Dekany, R.; Rahmer, G.; Hale, D.; Smith, R.; Zolkower, J.; Velur, V.; Walters, R.; Henning, J.; Bui, K.; McKenna, D.

    2010-12-01

    Type-IIn supernovae (SNe IIn), which are characterized by strong interaction of their ejecta with the surrounding circumstellar matter (CSM), provide a unique opportunity to study the mass-loss history of massive stars shortly before their explosive death. We present the discovery and follow-up observations of an SN IIn, PTF 09uj, detected by the Palomar Transient Factory (PTF). Serendipitous observations by Galaxy Evolution Explorer (GALEX) at ultraviolet (UV) wavelengths detected the rise of the SN light curve prior to the PTF discovery. The UV light curve of the SN rose fast, with a timescale of a few days, to a UV absolute AB magnitude of about -19.5. Modeling our observations, we suggest that the fast rise of the UV light curve is due to the breakout of the SN shock through the dense CSM (n ≈ 1010 cm-3). Furthermore, we find that prior to the explosion the progenitor went through a phase of high mass-loss rate (~0.1 M sun yr-1) that lasted for a few years. The decay rate of this SN was fast relative to that of other SNe IIn.

  2. Models of the circumstellar medium of evolving, massive runaway stars moving through the Galactic plane

    CERN Document Server

    Meyer, D M -A; Langer, N; Gvaramadze, V V; Mignone, A; Izzard, R G; Kaper, L

    2014-01-01

    At least 5 per cent of the massive stars are moving supersonically through the interstellar medium (ISM) and are expected to produce a stellar wind bow shock. We explore how the mass loss and space velocity of massive runaway stars affect the morphology of their bow shocks. We run two-dimensional axisymmetric hydrodynamical simulations following the evolution of the circumstellar medium of these stars in the Galactic plane from the main sequence to the red supergiant phase. We find that thermal conduction is an important process governing the shape, size and structure of the bow shocks around hot stars, and that they have an optical luminosity mainly produced by forbidden lines, e.g. [OIII]. The Ha emission of the bow shocks around hot stars originates from near their contact discontinuity. The H$\\alpha$ emission of bow shocks around cool stars originates from their forward shock, and is too faint to be observed for the bow shocks that we simulate. The emission of optically-thin radiation mainly comes from th...

  3. Disk Detective: Discovery of New Circumstellar Disk Candidates through Citizen Science

    CERN Document Server

    Kuchner, Marc J; Bans, Alissa S; Bhattacharjee, Shambo; Kenyon, Scott J; Debes, John H; Currie, Thayne; Garcia, Luciano; Jung, Dawoon; Lintott, Chris; McElwain, Michael; Padgett, Deborah L; Rebull, Luisa M; Wisniewski, John P; Nesvold, Erika; Schawinski, Kevin; Thaller, Michelle L; Grady, Carol A; Biggs, Joseph; Bosch, Milton; Cernohous, Tadeás; Luca, Hugo A Durantini; Hyogo, Michiharu; Wah, Lily Lau Wan; Piipuu, Art; Piñeiro, Fernanda

    2016-01-01

    The Disk Detective citizen science project aims to find new stars with 22 micron excess emission from circumstellar dust using data from NASA's WISE mission. Initial cuts on the AllWISE catalog provide an input catalog of 277,686 sources. Volunteers then view images of each source online in 10 different bands to identify false-positives (galaxies, background stars, interstellar matter, image artifacts, etc.). Sources that survive this online vetting are followed up with spectroscopy on the FLWO Tillinghast telescope. This approach should allow us to unleash the full potential of WISE for finding new debris disks and protoplanetary disks. We announce a first list of 37 new disk candidates discovered by the project, and we describe our vetting and follow-up process. One of these systems appears to contain the first debris disk discovered around a star with a white dwarf companion: HD 74389. We also report four newly discovered classical Be stars (HD 6612, HD 7406, HD 164137, and HD 218546) and a new detection o...

  4. COMPUTING THE CONTINUUM POLARIZATION FROM THOMSON SCATTERING IN GASEOUS CIRCUMSTELLAR DISKS

    Energy Technology Data Exchange (ETDEWEB)

    Halonen, R. J.; Mackay, F. E.; Jones, C. E., E-mail: rhalonen@uwo.ca [Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7 (Canada)

    2013-01-15

    We investigate the computation of the intrinsic continuum linear polarization from electron scattering in optically thin and thick circumstellar disks of gas. We present the use of a non-LTE radiative transfer code, along with two different computational methods for obtaining the Stokes parameters, to reproduce the polarization levels that arise from disks of classical Be stars. Since the pioneering work of Poeckert and Marlborough, numerous improvements and refinements have been incorporated into computational radiative transfer models of classical Be stars. We present an assessment of the effect of several improvements on Poeckert and Marlborough's technique for calculating the polarization levels of the classical Be star {gamma} Cas. We find that improvements to the sampling of the disk density and the inclusion of a non-isothermal structure for the gas in the disk yield polarization levels that differ from the levels expected by Poeckert and Marlborough. Principally, the inclusion of the self-consistent calculation of the thermal structure of the disk has a significant impact on the resulting polarization. In addition, we assess the importance of the inclusion of multiple scattering calculations in predicting the continuum polarization in classical Be stars. We confirm that multiple scattering calculations are necessary for studying the linear polarization levels from optically thick gaseous disks around classical Be stars.

  5. Disk Detective: Discovery of New Circumstellar Disk Candidates through Citizen Science

    Science.gov (United States)

    Kuchner, Marc J.; Silverberg, Steven M.; Bans, Alissa S.; Bhattacharjee, Shambo; Kenyon, Scott J.; Debes, John H.; Currie, Thayne; García, Luciano; Jung, Dawoon; Lintott, Chris; McElwain, Michael; Padgett, Deborah L.; Rebull, Luisa M.; Wisniewski, John P.; Nesvold, Erika; Schawinski, Kevin; Thaller, Michelle L.; Grady, Carol A.; Biggs, Joseph; Bosch, Milton; C̆ernohous, Tadeás̆; Durantini Luca, Hugo A.; Hyogo, Michiharu; Wah, Lily Lau Wan; Piipuu, Art; Piñeiro, Fernanda; Disk Detective Collaboration

    2016-10-01

    The Disk Detective citizen science project aims to find new stars with 22 μm excess emission from circumstellar dust using data from NASA’s Wide-field Infrared Survey Explorer (WISE) mission. Initial cuts on the AllWISE catalog provide an input catalog of 277,686 sources. Volunteers then view images of each source online in 10 different bands to identify false positives (galaxies, interstellar matter, image artifacts, etc.). Sources that survive this online vetting are followed up with spectroscopy on the FLWO Tillinghast telescope. This approach should allow us to unleash the full potential of WISE for finding new debris disks and protoplanetary disks. We announce a first list of 37 new disk candidates discovered by the project, and we describe our vetting and follow-up process. One of these systems appears to contain the first debris disk discovered around a star with a white dwarf companion: HD 74389. We also report four newly discovered classical Be stars (HD 6612, HD 7406, HD 164137, and HD 218546) and a new detection of 22 μm excess around the previously known debris disk host star HD 22128.

  6. A CHARA Array Survey of Circumstellar Disks around Nearby Be-type Stars

    CERN Document Server

    Touhami, Y; Schaefer, G H; McAlister, H A; Ridgway, S T; Richardson, N D; Matson, R; Grundstrom, E D; Brummelaar, T A ten; Goldfinger, P J; Sturmann, L; Sturmann, J; Turner, N H; Farrington, C

    2013-01-01

    We report on a high angular resolution survey of circumstellar disks around 24 northern sky Be stars. The K-band continuum survey was made using the CHARA Array long baseline interferometer (baselines of 30 to 331 m). The interferometric visibilities were corrected for the flux contribution of stellar companions in those cases where the Be star is a member of a known binary or multiple system. For those targets with good uv coverage, we used a four parameter Gaussian elliptical disk model to fit the visibilities and to determine the axial ratio, position angle, K-band photospheric flux contribution, and angular diameter of the disk major axis. For the other targets with relatively limited uv coverage, we constrained the axial ratio, inclination angle, and or disk position angle where necessary in order to resolve the degeneracy between possible model solutions. We also made fits of the ultraviolet and infrared spectral energy distributions to estimate the stellar angular diameter and infrared flux excess of e...

  7. High spatial resolution infrared imaging of L1551-IRS 5 - Direct observations of its circumstellar envelope

    Science.gov (United States)

    Moneti, Andrea; Forrest, William J.; Pipher, Judith L.; Woodward, Charles E.

    1988-01-01

    Images of L1551-IRS 5 were obtained at 1.65, 2.2, and 3.8 microns using the University of Rochester's Infrared Array Camera. It is found that IRS 5 is spatially resolved, and that it is elongated: the observed FWHM size of IRS 5 is 4.1 x 2.8 arcsec-squared at 2.2 microns. These observations are interpreted in terms of a flattened circumstellar envelope that is viewed from about 18 deg above its equatorial plane, a configuration that has been treated theoretically by Lefevre et al. In this model the central star is not seen directly, but only light scattered toward the observer from the visible polar region, where the envelope is thinnest, is observed. It is deduced that the envelope has a diameter of 1000 AU, a molecular hydrogen density of greater than or approximately equal to 4 x 10 to the 6th/cu cm, and a mass of greater than or approximately equal to 0.02 M solar mass, which results in an extinction of Av greater than about 33 mag to the central source.

  8. THE FIRST DETERMINATION OF THE VISCOSITY PARAMETER IN THE CIRCUMSTELLAR DISK OF A Be STAR

    Energy Technology Data Exchange (ETDEWEB)

    Carciofi, Alex C.; Bjorkman, Jon E.; Haubois, Xavier [Instituto de Astronomia, Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, Rua do Matao 1226, Cidade Universitaria, 05508-900, Sao Paulo, SP (Brazil); Otero, Sebastian A. [American Association of Variable Star Observers, 49 Bay State Road, Cambridge, MA 02138 (United States); Okazaki, Atsuo T. [Faculty of Engineering, Hokkai-Gakuen University, Toyohira-ku, Sapporo 062-8605 (Japan); Stefl, Stanislav; Rivinius, Thomas [European Organisation for Astronomical Research in the Southern Hemisphere, Casilla 19001, Santiago 19 (Chile); Baade, Dietrich, E-mail: carciofi@usp.br, E-mail: jon@physics.utoledo.edu [European Organisation for Astronomical Research in the Southern Hemisphere, Karl-Schwarzschild-Str. 2, 85748 Garching bei Muenchen (Germany)

    2012-01-15

    Be stars possess gaseous circumstellar decretion disks, which are well described using standard {alpha}-disk theory. The Be star 28 CMa recently underwent a long outburst followed by a long period of quiescence, during which the disk dissipated. Here we present the first time-dependent models of the dissipation of a viscous decretion disk. By modeling the rate of decline of the V-band excess, we determine that the viscosity parameter {alpha} = 1.0 {+-} 0.2, corresponding to a mass injection rate M-dot =(3.5{+-}1.3) Multiplication-Sign 10{sup -8} M{sub Sun} yr{sup -1}. Such a large value of {alpha} suggests that the origin of the turbulent viscosity is an instability in the disk whose growth is limited by shock dissipation. The mass injection rate is more than an order of magnitude larger than the wind mass-loss rate inferred from UV observations, implying that the mass injection mechanism most likely is not the stellar wind, but some other mechanism.

  9. Diagnostics of circumstellar grains in geometric models I: structure and composition

    Science.gov (United States)

    Dawes, J. H. P.; Greaves, J. S.

    2017-01-01

    The spectral energy distribution (SED) of circumstellar dust has been extensively used to diagnose the sizes and compositions of dust grains. We show that variations of SED slope in the long wavelength (submillimetre to radio) regime can be used to diagnose the gross physical nature (and hence origins) of the dust, using simple geometric models that complement the use of detailed simulations. We consider two dust grain types: (i) clustered aggregates of smaller particles (monomers), and (ii) composite grains comprising ferrous inclusions within a silicate matrix. These types are intended to be analogous to fluffy cometary particles and fragments of compacted asteroids, respectively. Our results indicate that clusters of silicate grains produce a smooth SED, while composite grains with FeS inclusions produce an SED that has a pronounced drop at a wavelength an order of magnitude larger than the grain size, and is flatter at long wavelengths. As a test case, we compare the model predictions to flux measurements of the TW Hydrae disc. This SED shows a drop that only occurs in our models of compacted grains with inclusions. Since the TW Hya discs spans approximately 10-40 AU in radius, fluffy particles from comets were perhaps expected, as in the Sun's Kuiper belt.

  10. A SCUBA-2 850-$\\mu$m survey of circumstellar disks in the $\\lambda$ Orionis cluster

    CERN Document Server

    Ansdell, Megan; Cieza, Lucas A

    2015-01-01

    We present results from an 850-$\\mu$m survey of the $\\sim$ 5 Myr old $\\lambda$ Orionis star-forming region. We used the SCUBA-2 camera on the James Clerk Maxwell Telescope to survey a $\\sim$0.5-diameter circular region containing 36 (out of 59) cluster members with infrared excesses indicative of circumstellar disks. We detected only one object at $>3\\sigma$ significance, the Herbig Ae star HD 245185, with a flux density of $\\sim74$ mJy beam$^{-1}$ corresponding to a dust mass of $\\sim150$ M$_{\\oplus}$. Stacking the individually undetected sources did not produce a significant mean signal but gives an upper limit on the average dust mass for $\\lambda$ Orionis disks of $\\sim3$ M$_{\\oplus}$. Our follow-up observations of HD 245185 with the Submillimeter Array found weak CO 2--1 line emission with an integrated flux of $\\sim170$ mJy km s$^{-1}$ but no $^{13}$CO or C$^{18}$O isotopologue emission at 30 mJy km s$^{-1}$ sensitivity, suggesting a gas mass of $\\lesssim1$ M$_{\\rm Jup}$. The implied gas-to-dust ratio i...

  11. Disk Detective: Discovery of New Circumstellar Disk Candidates Through Citizen Science

    Science.gov (United States)

    Kuchner, Marc J.; Silverberg, Steven M.; Bans, Alissa S.; Bhattacharjee, Shambo; Kenyon, Scott J.; Debes, John H.; Currie, Thayne; Garcia, Luciano; Jung, Dawoon; Lintott, Chris; hide

    2016-01-01

    The Disk Detective citizen science project aims to find new stars with 22 micron excess emission from circumstellar dust using data from NASAs Wide-field Infrared Survey Explorer (WISE) mission. Initial cuts on the AllWISE catalog provide an input catalog of 277,686 sources. Volunteers then view images of each source online in 10different bands to identify false positives (galaxies, interstellar matter, image artifacts, etc.). Sources that survive this online vetting are followed up with spectroscopy on the FLWO Tillinghast telescope. This approach should allow us to unleash the full potential of WISE for finding new debris disks and proto planetary disks. We announce a first list of 37 new disk candidates discovered by the project, and we describe our vetting and follow-up process. One of these systems appears to contain the first debris disk discovered around a star with a white dwarf companion: HD 74389. We also report four newly discovered classical Be stars (HD 6612, HD 7406, HD 164137,and HD 218546) and a new detection of 22 micron excess around the previously known debris disk host star HD 22128.

  12. The nearby population of M dwarfs with WISE: A search for warm circumstellar dust

    CERN Document Server

    Avenhaus, Henning; Meyer, Michael R

    2012-01-01

    Circumstellar debris disks are important for their connection to planetary systems. An efficient way to identify such systems is through their infrared excess. Most studies so far concentrated on early-type or solar-type stars, but less effort has gone into M dwarfs. We characterize the mid-infrared photometric behavior of M dwarfs and search for infrared excess in nearby M dwarfs taken from the volume-limited RECONS sample using data from the WISE satellite and the 2MASS catalog. Our sample consists of 85 sources encompassing 103 M dwarfs. We derive empirical infrared colors from these data and discuss their errors. From this, we check the stars for infrared excess and discuss the minimum excess we would be able to detect. Other than the M8.5 dwarf SCR 1845-6357 A, where the excess is produced by a known T6 companion, we detect no excesses in any of our sample stars. The limits we derive for the 22um excess are slightly larger than the usual detection limit of 10-15% for Spitzer studies, but the inclusion of...

  13. Supernova PTF 09uj: A possible shock breakout from a dense circumstellar wind

    CERN Document Server

    Ofek, E O; Neill, J D; Arcavi, I; Cenko, S B; Waxman, E; Kulkarni, S R; Yam, A Gal; Nugent, P E; Bildsten, L; Bloom, J S; Filippenko, A V; Forster, K; Howell, D A; Jacobsen, J; Kasliwal, M M; Law, N; Martin, C; Poznanski, D; Quimby, R M; Shen, K J; Sullivan, M; Dekany, R; Rahmer, G; Hale, D; Smith, R; Zolkower, J; Velur, V; Walters, R; Henning, J; Bui, K; McKenna, D

    2010-01-01

    Type-IIn supernovae (SNe), which are characterized by strong interaction of their ejecta with the surrounding circumstellar matter (CSM), provide a unique opportunity to study the mass-loss history of massive stars shortly before their explosive death. We present the discovery and follow-up observations of a Type IIn SN, PTF 09uj, detected by the Palomar Transient Factory (PTF). Serendipitous observations by GALEX at ultraviolet (UV) wavelengths detected the rise of the SN light curve prior to the PTF discovery. The UV light curve of the SN rose fast, with a time scale of a few days, to a UV absolute AB magnitude of about -19.5. Modeling our observations, we suggest that the fast rise of the UV light curve is due to the breakout of the SN shock through the dense CSM (n~10^10 cm^-3). Furthermore, we find that prior to the explosion the progenitor went through a phase of high mass-loss rate (~0.1 solar mass per year) that lasted for a few years. The decay rate of this SN was fast relative to that of other SNe I...

  14. Do water fountain jets really indicate the onset of the morphological metamorphosis of circumstellar envelopes?

    Science.gov (United States)

    Yung, Bosco H. K.; Nakashima, Jun-ichi; Hsia, Chih-Hao; Imai, Hiroshi

    2017-03-01

    Small-scale bipolar jets with short dynamical ages from 'water-fountain' (WF) sources are regarded as an indication of the onset of circumstellar envelope morphological metamorphosis of intermediate-mass stars. Such a process usually happens at the end of the asymptotic giant branch (AGB) phase. However, recent studies found that WFs could be AGB stars or even early planetary nebulae. This fact prompted the idea that WFs may not necessarily be objects at the beginning of the morphological transition process. In the present work, we show that WFs could have different envelope morphologies by studying their spectral energy distribution profiles. Some WFs have spherical envelopes that resemble usual AGB stars, while others have aspherical envelopes, which are more common to post-AGB stars. The results imply that WFs may not represent the earliest stage of morphological metamorphosis. We argue further that the dynamical age of a WF jet, which can be calculated from maser proper motions, may not be the real age of the jet. The dynamical age cannot be used to justify the moment when the envelope begins to become aspherical, nor to tell the concrete evolutionary status of the object. A WF jet could be the innermost part of a larger well-developed jet, which is not necessarily a young jet.

  15. First Detection of Near-Infrared Line Emission from Organics in Young Circumstellar Disks

    CERN Document Server

    Mandell, A M; van Dishoeck, E F; Blake, G A; Salyk, C; Mumma, M J; Villanueva, G

    2012-01-01

    We present an analysis of high-resolution spectroscopy of several bright T Tauri stars using the VLT/CRIRES and Keck/NIRSPEC spectrographs, revealing the first detections of emission from HCN and C2H2 in circumstellar disks at near-infrared wavelengths. Using advanced data reduction techniques we achieve a dynamic range with respect to the disk continuum of ~500 at 3 microns, revealing multiple emission features of H2O, OH, HCN, and C2H2. We also present stringent upper limits for two other molecules thought to be abundant in the inner disk, CH4 and NH3. Line profiles for the different detected molecules are broad but centrally peaked in most cases, even for disks with previously determined inclinations of greater than 20 degrees, suggesting that the emission has both a Keplerian and non-Keplerian component as observed previously for CO emission. We apply two different modeling strategies to constrain the molecular abundances and temperatures: we use a simplified single-temperature LTE slab model with a Gauss...

  16. On the Origin of the Spiral Morphology in the Elias 2-27 Circumstellar Disk

    Science.gov (United States)

    Meru, Farzana; Juhász, Attila; Ilee, John D.; Clarke, Cathie J.; Rosotti, Giovanni P.; Booth, Richard A.

    2017-04-01

    The young star Elias 2-27 has recently been observed to posses a massive circumstellar disk with two prominent large-scale spiral arms. In this Letter, we perform three-dimensional Smoothed Particle Hydrodynamics simulations, radiative transfer modeling, synthetic ALMA imaging, and an unsharped masking technique to explore three possibilities for the origin of the observed structures—an undetected companion either internal or external to the spirals, and a self-gravitating disk. We find that a gravitationally unstable disk and a disk with an external companion can produce morphology that is consistent with the observations. In addition, for the latter, we find that the companion could be a relatively massive planetary-mass companion (≲10-13 M Jup) and located at large radial distances (between ≈300-700 au). We therefore suggest that Elias 2-27 may be one of the first detections of a disk undergoing gravitational instabilities, or a disk that has recently undergone fragmentation to produce a massive companion.

  17. The circumstellar disc of AB Aurigae: evidence for envelope accretion at late stages of star formation?

    CERN Document Server

    Tang, Ya-Wen; Pietu, Vincent; Dutrey, Anne; Ohashi, Nagayoshi; Ho, Paul T P

    2012-01-01

    The circumstellar disc of AB Aurigae has garnered great attentions due to the apparent existence of spirals at a relatively young stage and also the asymmetric disc traced in thermal dust emission. However, the physical conditions of the spirals are still not well understood. The origin of the asymmetric thermal emission is unclear. We observe the disc at 230 GHz (1.3 mm) in both continuum and the spectral line ^12 CO 2-1 with IRAM 30 m, the PdBI and the SMA to sample all spatial scales from 0.37" to about 50". To combine the data obtained from these telescopes, several methods and calibration issues have been checked and discussed. The 1.3 mm continuum (dust) emission is resolved into inner disc and outer ring. The emission from the dust ring is highly asymmetric in azimuth, with intensity variations by a factor 3. Molecular gas at high velocities traced by the CO line is detected aside the stellar location. The inclination angle of the disc is found to decrease toward the center. At larger scale, based on t...

  18. Modeling Transiting Circumstellar Disks: Characterizing the Newly Discovered Eclipsing Disk System OGLE LMC-ECL-11893

    CERN Document Server

    Scott, Erin L; Pecaut, Mark J; Quillen, Alice C; Moolekamp, Fred; Bell, Cameron P M

    2014-01-01

    We investigate the nature of the unusual eclipsing star OGLE LMC-ECL-11893 (OGLE J05172127-6900558) in the Large Magellanic Cloud recently reported by Dong et al. 2014. The eclipse period for this star is 468 days, and the eclipses exhibit a minimum of ~1.4 mag, preceded by a plateau of ~0.8 mag. Spectra and optical/IR photometry are consistent with the eclipsed star being a lightly reddened B9III star of inferred age ~150 Myr and mass of ~4 solar masses. The disk appears to have an outer radius of ~0.2 AU with predicted temperatures of ~1100-1400 K. We model the eclipses as being due to either a transiting geometrically thin dust disk or gaseous accretion disk around a secondary object; the debris disk produces a better fit. We speculate on the origin of such a dense circumstellar dust disk structure orbiting a relatively old low-mass companion, and on the similarities of this system to the previously discovered EE Cep.

  19. Far-infrared and sub-millimetre imaging of HD~76582's circumstellar disk

    CERN Document Server

    Marshall, J P; Holland, W S; Matthews, B C; Greaves, J S; Zuckerman, B

    2016-01-01

    Debris disks, the tenuous rocky and icy remnants of planet formation, are believed to be evidence for planetary systems around other stars. The JCMT/SCUBA-2 debris disk legacy survey 'SCUBA-2 Observations of Nearby Stars' (SONS) observed 100 nearby stars, amongst them HD~76582, for evidence of such material. Here we present imaging observations by JCMT/SCUBA-2 and \\textit{Herschel}/PACS at sub-millimetre and far-infrared wavelengths, respectively. We simultaneously model the ensemble of photometric and imaging data, spanning optical to sub-millimetre wavelengths, in a self-consistent manner. At far-infrared wavelengths, we find extended emission from the circumstellar disk providing a strong constraint on the dust spatial location in the outer system, although the angular resolution is too poor to constrain the interior of the system. In the sub-millimetre, photometry at 450 and 850~$\\mu$m reveal a steep fall-off that we interpret as a disk dominated by moderately-sized dust grains ($a_{\\rm min}~=~36~\\mu$m), ...

  20. Do Water Fountain Jets Really Indicate the Onset of the Morphological Metamorphosis of Circumstellar Envelopes?

    CERN Document Server

    Yung, Bosco H K; Hsia, Chih-Hao; Imai, Hiroshi

    2016-01-01

    The small-scale bipolar jets having short dynamical ages from "water fountain (WF)" sources are regarded as an indication of the onset of circumstellar envelope morphological metamorphosis of intermediate-mass stars. Such process usually happens at the end of the asymptotic giant branch (AGB) phase. However, recent studies found that WFs could be AGB stars or even early planetary nebulae. This fact prompted the idea that WFs may not necessarily be objects at the beginning of the morphological transition process. In the present work, we show that WFs could have different envelope morphologies by studying their spectral energy distribution profiles. Some WFs have spherical envelopes that resembles usual AGB stars, while others have aspherical envelopes which are more common to post-AGB stars. The results imply that WFs may not represent the earliest stage of the morphological metamorphosis. We further argue that the dynamical age of a WF jet, which can be calculated from maser proper motions, may not be the rea...

  1. The circumstellar matter of supernova 2014J and the core-degenerate scenario

    CERN Document Server

    Soker, Noam

    2015-01-01

    I show that the circumstellar matter (CSM) of the type Ia supernova 2014J is too massive and its momentum too large to be accounted for by any but the core-degenerate (CD) scenario for type Ia supernovae. Assuming the absorbing gas is of CSM origin, the several shells responsible of the absorption potassium lines are accounted for by a mass loss episode from a massive asymptotic giant branch star during a common envelope phase with a white dwarf companion. The time-varying potassium lines can be accounted for by ionization of neutral potassium and the Na-from-dust absorption (NaDA) model. Before explosion some of the potassium resides in the gas phase and some in dust. Weakening in absorption strength is caused by potassium-ionizing radiation of the supernova, while release of atomic potassium from dust increases the absorption. I conclude that if the absorbing gas originated from the progenitor of SN 2014J, then a common envelope phase took place about 15,000 years ago, leading to the merging of the core wit...

  2. A hydrodynamical model of the circumstellar bubble created by two massive stars

    CERN Document Server

    van Marle, Allard Jan; Marcowith, Alexandre

    2012-01-01

    Numerical models of the wind-blown bubble of massive stars usually account only for the wind of a single star. However, since massive stars are usually formed in clusters, it would be more realistic to follow the evolution of a bubble created by several stars. We make a 2D model of the circumstellar bubble created by two massive stars: a 40 solar mass star and a 25 solar mass star and follow its evolution. The stars have a separation of approx. 16 pc and surrounded by a cold medium with a density of 20 particles per cubic cm. We use the MPI-AMRVAC hydrodynamics code to solve the conservation equations of hydrodynamics on a 2D cylindrical grid using time-dependent models for the parameters of the wind of the two stars. At the end of the stellar evolution (4.5 and 7.0 million years for the 40 and 25 solar mass stars respectively) we simulate the supernova explosion of each star. Initially, each star creates its own bubble. However, as the bubbles expand they merge, creating a combined, a-spherical bubble. The c...

  3. CO and H2 Absorption in the AA Tauri Circumstellar Disk

    CERN Document Server

    France, Kevin; Herczeg, Gregory J; Schindhelm, Eric; Yang, Hao; Abgrall, Herve; Roueff, Evelyne; Brown, Alexander; Brown, Joanna; Linsky, Jeffrey L

    2011-01-01

    The direct study of molecular gas in inner protoplanetary disks is complicated by uncertainties in the spatial distribution of the gas, the time-variability of the source, and the comparison of observations across a wide range of wavelengths. Some of these challenges can be mitigated with far-ultraviolet spectroscopy. Using new observations obtained with the HST-Cosmic Origins Spectrograph, we measure column densities and rovibrational temperatures for CO and H2 observed on the line-of-sight through the AA Tauri circumstellar disk. CO A-X absorption bands are observed against the far-UV continuum. The CO absorption is characterized by log(N(^{12}CO)) = 17.5 +/- 0.5 cm^{-2} and T_rot(CO) = 500$^{+500}_{-200} K, although this rotational temperature may underestimate the local kinetic temperature of the CO-bearing gas. We also detect ^{13}CO in absorption with an isotopic ratio of ~20. We do not observe H2 absorption against the continuum; however, hot H2 (v > 0) is detected in absorption against the LyA emissio...

  4. The Origin of the Near-infrared Excess in SN Ia 2012dn: Circumstellar Dust around the Super-Chandrasekhar Supernova Candidate

    Science.gov (United States)

    Nagao, Takashi; Maeda, Keiichi; Yamanaka, Masayuki

    2017-02-01

    The nature of progenitors of the so-called super-Chandrasekhar candidate Type Ia supernovae (SC-SNe Ia) has been actively debated. Recently, Yamanaka et al. reported a near-infrared (NIR) excess for SN 2012dn and proposed that the excess originates from an echo by circumstellar (CS) dust. In this paper, we examine a detailed distribution of the CS dust around SN 2012dn and investigate implications of the CS dust echo scenario for general cases of SC-SNe Ia. We find that a disk/bipolar CS medium configuration reproduces the NIR excess fairly well, where the radial density distribution is given by a stationary mass loss. The inner radius of the CS dust is 0.04 pc. The mass-loss rate of the progenitor system is estimated to be 1.2× {10}-5 and 3.2× {10}-6 M⊙ yr‑1 for the disk and bipolar CS medium configurations, respectively, which adds further support for the single-degenerate scenario. Our models limit SN 2009dc, another SC-SN Ia, to have a dust mass less than 0.16 times that of SN 2012dn. While this may merely indicate some variation on the CS environment among SC-SNe Ia, this could raise another interesting possibility. There could be two classes among SC-SNe Ia: the brighter SC-SNe Ia in a clean environment (SN 2009dc) and the fainter SC-SNe Ia in a dusty environment (SN 2012dn).

  5. Infrared emission features: probing the interstellar PAH population and circumstellar environment of Herbig Ae/Be stars

    Science.gov (United States)

    Boersma, Christiaan

    2009-12-01

    AKs zijn alom vertegenwoordigd en bieden een uitstekend middel om de veelheid aan objecten verspreid over het heelal te bestuderen. Met name in gebieden waar zich sterren en planeten vormen, helpen ze bij het ontwarren van de grootschalige structuur. PAKs staat voor polycyclische aromatische koolwaterstoffen en ze vormen een familie van grote kippengaasvormige moleculen opgebouwd uit koolstof en waterstof. Op aarde worden ze onderander aangetroffen in de verbrandingsproducten van fossiele brandstoffen. PAKs vormen het overgangsgebied van stofdeeltjes ter grote van een micron naar moleculair "gas". PAKs zijn uniek op twee manieren. Allereerst, PAKs fluoresceren na de absorptie van een enkel ultraviolet foton, waardoor ze te zien zijn in zeer koude gebieden, ver weg van de aanstralende bron. In de tweede plaats, gegeven de complexiteit van deze moleculen, kunnen ze een belangrijke rol hebben gespeeld in het ontstaan van leven. Met behulp van topklasse ruimte- en grond gestationeerde observatoria, zoals bijvoorbeeld Spitzer en de 10-meter klasse telescopen in Chili, is de PAK-emissie afkomstig van middelzware, zich vormende, sterren onderzocht. Door gebruik van zowel beeldvorming als spectroscopie, zijn morfologische en evolutionaire aspecten van de PAK-emissie vastgesteld. De NASA Ames PAK IR Spectroscopische Database is een verzameling van meer dan 600 berekend en ongeveer 200 experimenteel bepaalde spectra. Deze unieke database gaat eind 2009 publiek. Gebruikmakend van deze database is een systematische zoektocht gedaan naar kandidaten die verantwoordelijk kunnen worden gehouden voor de emissie in twee, tot op heden, niet goed bestudeerde regio's van het PAKs-spectra.

  6. AG Carinae III. The 1990 hot phase of the star and the physical structure of the circumstellar environment

    CERN Document Server

    Viotti, R; Rossi, C

    1993-01-01

    Long slit spectra of the region around the Luminous Blue Variable AG Car obtained in June 1990, just before the onset of its new brightening phase, indicate that AG Car was in the hottest phase so far recorded. The spectrum shows strong broad emissions of He II 468.6 nm, and [Fe III] 465.8-470.1 nm, and He I, N II, Si III, Al III and Fe III with a P Cygni profile. We have also identified weak lines of C II and O II. A faint continuum emission has been detected within the whole ring nebula. We also find that the spectrum of some regions is partially due to scattered star's light. This provides evidence of the presence of dust grains, and indicates that even in present times dust is condensing from AG Car wind. The sharp outer edge of the ring suggest the presence of a shock front. We have also identified an extended low density H II $halo$, which should be associated with the residual of the stellar wind of a previous cooler evolutionary phase of AG Car. In the halo the H$\\alpha$/[N II] ratio is strengthened w...

  7. SINGLE AND DOUBLE PHOTOIONIZATION AND PHOTODISSOCIATION OF TOLUENE BY SOFT X-RAYS IN A CIRCUMSTELLAR ENVIRONMENT

    Energy Technology Data Exchange (ETDEWEB)

    Monfredini, T.; Boechat-Roberty, H. M. [Observatório do Valongo, Universidade Federal do Rio de Janeiro, Ladeira Pedro Antonio, 43, Rio de Janeiro (Brazil); Fantuzzi, F.; Nascimento, M. A. C. [Instituto de Química, Universidade Federal do Rio de Janeiro, Av. Athos da Silveira Ramos, 149, Rio de Janeiro (Brazil); Wolff, W., E-mail: heloisa@astro.ufrj.br [Instituto de Física, Universidade Federal do Rio de Janeiro, Av. Athos da Silveira Ramos, 149, Rio de Janeiro (Brazil)

    2016-04-10

    The formation of polycyclic aromatic hydrocarbons (PAHs) and their methyl derivatives mainly occurs in the dust shells of asymptotic giant branch (AGB) stars. The bands at 3.3 and 3.4 μm, observed in infrared emission spectra of several objects, are attributed C–H vibrational modes in aromatic and aliphatic structures, respectively. In general, the feature at 3.3 μm is more intense than that at 3.4 μm. Photoionization and photodissociation processes of toluene, the precursor of methylated PAHs, were studied using synchrotron radiation at soft X-ray energies around the carbon K edge using time-of-flight mass spectrometry. Partial ion yields of a large number of ionic fragments were extracted from single and 2D-spectra, where electron-ion coincidences have revealed the doubly charged parent molecule and several doubly charged fragments containing seven carbon atoms with considerable abundance. Ab initio calculations based on density functional theory were performed in order to elucidate the chemical structure of these stable dicationic species. The survival of the dications subjected to hard inner shell ionization suggests that they could be observed in the interstellar medium, especially in regions where PAHs are detected. The ionization and destruction of toluene induced by X-rays were examined in the T Dra conditions, a carbon-rich AGB star. In this context, a minimum photodissociation radius and the half-life of toluene subjected to the incidence of the soft X-ray flux emitted from a companion white dwarf star were determined.

  8. Interstellar-medium Mapping in M82 and Circumstellar Environment Constraints through Light Echoes Around Supernova 2014J

    Science.gov (United States)

    Yang, Yi; Wang, Lifan

    2017-01-01

    We present multiple-epoch measurements of the size and surface brightness of the light echoes from supernova (SN) 2014J in the nearby starburst galaxy M82. Hubble Space Telescope (HST) ACS/WFC images were taken ˜277 and ˜416 days after B-band maximum in the filters F475W, F606W, and F775W. Linear polarimetry of the SN 2014J has also been acquired. The images reveal the temporal evolution of at least two major light-echo components. The first one exhibits a filled ring structure with position-angle-dependent intensity. This radially extended, diffuse echo indicates the presence of an inhomogeneous interstellar dust cloud ranging from ˜100 pc to ˜500 pc in the foreground of the SN. The second echo component appears as an unresolved luminous quarter-circle arc centered on the SN. The wavelength dependence of scattering measured in different dust components suggests that the dust producing the luminous arc favors smaller grain sizes, while that causing the diffuse light echo may have sizes similar to those of the Milky Way dust. Smaller grains can produce an optical depth consistent with that along the supernova-Earth line of sight measured by previous studies around maximum light. Therefore, it is possible that the dust slab, from which the luminous arc arises, is also responsible for most of the extinction towards SN 2014J. The optical depths produced by the diffuse Milky Way-like dust in the scattering matters are lower than that produced by the dust slab. Apart from the resolved light echoes, the polarization of the SN 2014J point source measured at day 277 shows conspicuous deviations from other epochs and this can be identified as due to at least 10-6 Msun of dust located at a distance of ~5×1017 cm away from the SN. The presence of this CS dust may set strong constraints on the progenitor system that led to the explosion of SN 2014J.

  9. ALMA observations of anisotropic dust mass loss in the inner circumstellar environment of the red supergiant VY Canis Majoris

    NARCIS (Netherlands)

    O'Gorman, E.; Vlemmings, W.; Richards, A.M.S.; Baudry, A.; De Beck, E.; Decin, L.; Harper, G.M.; Humphreys, E.M.; Kervella, P.; Khouri, T.; Muller, S.

    2015-01-01

    The processes leading to dust formation and the subsequent role it plays in driving mass loss in cool evolved stars is an area of intense study. Here we present high resolution ALMA Science Verification data of the continuum emission around the highly evolved oxygen-rich red supergiant VY CMa. These

  10. ALMA observations of anisotropic dust mass loss in the inner circumstellar environment of the red supergiant VY Canis Majoris

    NARCIS (Netherlands)

    O'Gorman, E.; Vlemmings, W.; Richards, A.M.S.; Baudry, A.; De Beck, E.; Decin, L.; Harper, G.M.; Humphreys, E.M.; Kervella, P.; Khouri, T.; Muller, S.

    2015-01-01

    The processes leading to dust formation and the subsequent role it plays in driving mass loss in cool evolved stars is an area of intense study. Here we present high resolution ALMA Science Verification data of the continuum emission around the highly evolved oxygen-rich red supergiant VY CMa. These

  11. Circumstellar Dust Shells: Clues to the Evolution of R Coronae Borealis Stars

    Science.gov (United States)

    Montiel, Edward J.; Clayton, Geoffrey C.

    2016-06-01

    R Coronae Borealis (RCB) stars are an exotic group of extremely hydrogen- deficient, carbon-rich supergiants that are known for their spectacular declines in brightness (up to 8 mags) at irregular intervals. Two scenarios are currently competing to explain the origins of these stars. One suggests that RCB stars are the products after a binary white dwarf (WD) system merges. The other takes a single, evolved star and has it undergo a final, helium-shell flash (FF) and becoming a cool giant. Recently, observations of elemental abundances in RCB stars have strongly swung the argument in favor of the WD merger model. The FF scenario has maintained its relevancy by seemingly being the only model able to offer a suitable explanation for one RCB feature that merger model has historically struggled with explaining: the presence of cold, circumstellar dust envelopes which might be fossil planetary nebulae (PNe). In reality, the shells could actually be fossil PNe, material left over from the WD merger, or mass lost during the RCB phase, itself. I will present the results of my dissertation, which is to try and discern the nature and history of the far-IR dust shells around RCB stars to help understand the origin of these enigmatic stars. I will discuss our efforts to determine the mass, size, temperature, and morphology of these diffuse structures surrounding a sample of RCB stars using multi-wavelength observations ranging from the ultraviolet to the submillimeter. These observations have provided unprecedented wavelength coverage for both the central stars and their CSM. They have been examined by eye for morphology and have been used in the construction of maximum-light spectral energy distributions (SEDs). I will present the results of our Monte Carlo radiative transfer of the maximum-light SEDs. Finally, I will highlight our work investigating the HI abundance of the envelope of R Coronae Borealis, itself, using archival 21—cm observations from the Arecibo

  12. The First 40 Million Years of Circumstellar Disk Evolution: The Signature of Terrestrial Planet Formation

    Science.gov (United States)

    Meng, Huan Y. A.; Rieke, George H.; Su, Kate Y. L.; Gáspár, András

    2017-02-01

    We characterize the first 40 Myr of evolution of circumstellar disks through a unified study of the infrared properties of members of young clusters and associations with ages from 2 Myr up to ˜40 Myr: NGC 1333, NGC 1960, NGC 2232, NGC 2244, NGC 2362, NGC 2547, IC 348, IC 2395, IC 4665, Chamaeleon I, Orion OB1a and OB1b, Taurus, the β Pictoris Moving Group, ρ Ophiuchi, and the associations of Argus, Carina, Columba, Scorpius-Centaurus, and Tucana-Horologium. Our work features: (1) a filtering technique to flag noisy backgrounds; (2) a method based on the probability distribution of deflections, P(D), to obtain statistically valid photometry for faint sources; and (3) use of the evolutionary trend of transitional disks to constrain the overall behavior of bright disks. We find that the fraction of disks three or more times brighter than the stellar photospheres at 24 μm decays relatively slowly initially and then much more rapidly by ˜10 Myr. However, there is a continuing component until ˜35 Myr, probably due primarily to massive clouds of debris generated in giant impacts during the oligarchic/chaotic growth phases of terrestrial planets. If the contribution from primordial disks is excluded, the evolution of the incidence of these oligarchic/chaotic debris disks can be described empirically by a log-normal function with the peak at 12-20 Myr, including ˜13% of the original population, and with a post-peak mean duration of 10-20 Myr.

  13. A Novel Approach to Constraining the Lifetime of Primordial Gas in Circumstellar Disks

    Science.gov (United States)

    Anderson, Dana; Bergin, Edwin A.; Blake, Geoffrey A.; Zhang, Ke; Carpenter, John M.; Schwarz, Kamber R.

    2016-10-01

    The lifetime of primordial gas in circumstellar disks limits the timescale for gas-giant planet formation, determines the impact of gas-particle dynamics throughout disk evolution, and therefore influences the composition and architecture of planetary systems forming from these disks. Current estimates of the gas lifetime are based mainly on indirect tracers of the primordial gas, predominately IR through sub-mm dust and CO emission, in systems of different ages. However, these conventional gas tracers may be less reliable in older systems where the gas-to-dust ratio is highly uncertain and observations suggest that carbon may be severely depleted from the gas relative to interstellar abundances. Here we investigate the evolution of primordial disk gas using a novel approach based on evidence from our own solar system. The enhanced carbon-to-nitrogen (C/N) ratios in meteorites and comets relative to the solar value suggest that N is less likely than C to be sequestered into the solid phase as the disk evolves. Therefore, observable N-bearing volatile species such as N2H+ may be more accurate tracers of the gas than CO in older disks. N2H+ was detected in two mature, ˜5-11 Myr old, disks in the Upper Scorpious OB Association using ALMA. Comparison with previous CO measurements of these sources by Barenfeld et al. (2016) result in high N2H+/CO flux ratios relative to estimates of comparable measurements for younger, gas-rich disks based on a survey by Öberg et al. (2010, 2011). These preliminary results demonstrate that the mature disks retain primordial gas and may suggest a greater depletion of C relative to N from the gas as the disk evolves. Chemical modeling of these systems will aid in determining molecular column densities and relating the observed emission to the total molecular hydrogen mass.

  14. A deep Spitzer survey of circumstellar disks in the young double cluster, h and χ Persei

    Energy Technology Data Exchange (ETDEWEB)

    Cloutier, Ryan; Currie, Thayne; Jayawardhana, Ray [University of Toronto, 50 St. George Street, Toronto, ON, M5S 2J7 (Canada); Rieke, George H. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Kenyon, Scott J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02140 (United States); Balog, Zoltan, E-mail: cloutier@cita.utoronto.ca, E-mail: currie@astro.utoronto.ca, E-mail: grieke@as.arizona.edu, E-mail: skenyon@cfa.harvard.edu [Max Planck Institute for Astrophysics, Königstuhl 17, D-69117 Heidelberg (Germany)

    2014-12-01

    We analyze very deep Infrared Array Camera and Multiband Imaging Photometer for Spitzer (MIPS) photometry of ∼12, 500 members of the 14 Myr old Double Cluster, h and χ Persei, building upon our earlier, shallower Spitzer Cycle 1 studies. Numerous likely members show infrared (IR) excesses at 8 μm and 24 μm, indicative of circumstellar dust. The frequency of stars with 8 μm excess is at least 2% for our entire sample, slightly lower (higher) for B/A stars (later type, lower mass stars). Optical spectroscopy also identifies gas in about 2% of systems, but with no clear trend between the presence of dust and gas. Spectral energy distribution modeling of 18 sources with detections at optical wavelengths through MIPS 24 μm reveals a diverse set of disk evolutionary states, including a high fraction of transitional disks, though similar data for all disk-bearing members would provide constraints. Using Monte Carlo simulations, we combine our results with those for other young clusters to study the global evolution of dust/gas disks. For nominal cluster ages, the e-folding times (τ{sub 0}) for the frequency of warm dust and gas are 2.75 Myr and 1.75 Myr, respectively. Assuming a revised set of ages for some clusters, these timescales increase to 5.75 and 3.75 Myr, respectively, implying a significantly longer typical protoplanetary disk lifetime than previously thought. In both cases, the transitional disk duration, averaged over multiple evolutionary pathways, is ≈1 Myr. Finally, 24 μm excess frequencies for 4-6 M {sub ☉} stars appear lower than for 1-2.5 M {sub ☉} stars in other 10-30 Myr old clusters.

  15. The Abundance of C2H4 in the Circumstellar Envelope of IRC+10216

    Science.gov (United States)

    Fonfría, J. P.; Hinkle, K. H.; Cernicharo, J.; Richter, M. J.; Agúndez, M.; Wallace, L.

    2017-02-01

    High spectral resolution mid-IR observations of ethylene ({{{C}}}2{{{H}}}4) toward the AGB star IRC+10216 were obtained using the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope Facility (IRTF). 80 ro-vibrational lines from the 10.5 μm vibrational mode {ν }7 with J ≲ 30 were detected in absorption. The observed lines are divided into two groups with rotational temperatures of 105 and 400 K (warm and hot lines). The warm lines peak at ≃ ‑14 km s‑1 with respect to the systemic velocity, suggesting that they are mostly formed outwards from ≃ 20{R}\\star . The hot lines are centered at ‑10 km s‑1 indicating that they come from a shell between 10 and 20{\\text{}}{R}\\star . 35% of the observed lines are unblended and can be fitted with a code developed to model the emission of a spherically symmetric circumstellar envelope. The analysis of several scenarios reveals that the {{{C}}}2{{{H}}}4 abundance relative to H2 in the range 5‑20R⋆ is 6.9× {10}-8 on average and it could be as high as 1.1 × 10‑7. Beyond 20{\\text{}}{R}\\star , it is 8.2 × 10‑8. The total column density is (6.5 ± 3.0) × 1015 cm‑2. {{{C}}}2{{{H}}}4 is found to be rotationally under local thermodynamical equilibrium (LTE) and vibrationally out of LTE. One of the scenarios that best reproduce the observations suggests that up to 25% of the {{{C}}}2{{{H}}}4 molecules at 20{\\text{}}{R}\\star could condense onto dust grains. This possible depletion would not significantly influence the gas acceleration although it could play a role in the surface chemistry on the dust grains.

  16. Circumbinary ring, circumstellar disks, and accretion in the binary system UY Aurigae

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Ya-Wen; Ho, Paul T. P. [Academia Sinica, Institute of Astronomy and Astrophysics, Taipei, Taiwan (China); Dutrey, Anne; Guilloteau, Stéphane; Di Folco, Emmanuel [Université de Bordeaux, Observatoire Aquitain des Sciences de l' Univers, CNRS, UMR 5804, Laboratoire d' Astrophysique de Bordeaux, 2 rue de l' Observatoire, BP 89, F-33271 Floirac Cedex (France); Piétu, Vincent; Gueth, Fréderic [IRAM, 300 rue de la piscine, F-38406 Saint Martin d' Hères Cedex (France); Beck, Tracy [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Boehler, Yann [Centro de Radioastronomìa y Astrofìsica, UNAM, Apartado Postal 3-72, 58089 Morelia, Michoacàn (Mexico); Bary, Jeff [Department of Physics and Astronomy, Colgate University, 13 Oak Drive, Hamilton, NY 13346 (United States); Simon, Michal, E-mail: ywtang@asiaa.sinica.edu.tw [Stony Brook University, Stony Brook, NY 11794-3800 (United States)

    2014-09-20

    Recent exo-planetary surveys reveal that planets can orbit and survive around binary stars. This suggests that some fraction of young binary systems which possess massive circumbinary (CB) disks may be in the midst of planet formation. However, there are very few CB disks detected. We revisit one of the known CB disks, the UY Aurigae system, and probe {sup 13}CO 2-1, C{sup 18}O 2-1, SO 5(6)-4(5) and {sup 12}CO 3-2 line emission and the thermal dust continuum. Our new results confirm the existence of the CB disk. In addition, the circumstellar (CS) disks are clearly resolved in dust continuum at 1.4 mm. The spectral indices between the wavelengths of 0.85 mm and 6 cm are found to be surprisingly low, being 1.6 for both CS disks. The deprojected separation of the binary is 1.''26 based on our 1.4 mm continuum data. This is 0.''07 (10 AU) larger than in earlier studies. Combining the fact of the variation of UY Aur B in R band, we propose that the CS disk of an undetected companion UY Aur Bb obscures UY Aur Ba. A very complex kinematical pattern inside the CB disk is observed due to a mixing of Keplerian rotation of the CB disk, the infall and outflow gas. The streaming gas accreting from the CB ring toward the CS disks and possible outflows are also identified and resolved. The SO emission is found to be at the bases of the streaming shocks. Our results suggest that the UY Aur system is undergoing an active accretion phase from the CB disk to the CS disks. The UY Aur B might also be a binary system, making the UY Aur a triple system.

  17. Mid-Infrared Signatures from Type Ia Supernovae Strongly Interacting with a Circumstellar Medium

    Science.gov (United States)

    Fox, Ori

    2016-08-01

    Type Ia supernovae (SNe Ia) are well-known for their use as precise cosmological distance indicators due to a standardizable peak luminosity resulting from a thermonuclear explosion. A growing subset of SNe Ia, however, show evidence for interaction with a dense circumstellar medium during the first year post-explosion, and sometimes longer (SNe Ia-CSM). The origin of this dense CSM is unknown and suggests either a) the less typical single-degenerate progenitor scenario must be considered or b) the exploding star was not a thermonuclear explosion of a white dwarf at all (i.e., core-collapse). Mid-infrared (IR) observations, in particular, are critical for tracing the density profile of dust (and hence gas) in the surrounding CSM. Yet no Spitzer light curve exists for this subclass within the first year post-expolosion. Here we propose a 'low-impact' (>8 weeks) ToO to obtain 3 epochs of Spitzer imaging of a SN Ia-CSM within 100 Mpc over 1 year post-explosion. The strength of this program is that it will be in conjunction with pre-approved multi-wavelength programs on HST/STIS/UV (GO 13649), Chandra/ASIS-S (17500672), the Keck/LRIS optical spectrograph (U037LA), and the RATIR visible/infrared robotic imager. Requiring only 2.1 hours of observation total, this program will not only distinguish between the SN explosion mechanisms, but also trace CSM interaction, constrain the progenitor mass loss history, and identify late-time heating mechanisms of warm dust.

  18. The Abundance of C2H4 in the Circumstellar Envelope of IRC+10216

    Science.gov (United States)

    Fonfría, J. P.; Hinkle, K. H.; Cernicharo, J.; Richter, M. J.; Agúndez, M.

    2017-01-01

    High spectral resolution mid-IR observations of ethylene (C2H4) towards the AGB star IRC+10216 were obtained using the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope Facility (IRTF). Eighty ro-vibrational lines from the 10.5 µm vibrational mode ν7 with J ≲ 30 were detected in absorption. The observed lines are divided into two groups with rotational temperatures of 105 and 400 K (warm and hot lines). The warm lines peak at ≃ −14 km s−1 with respect to the systemic velocity, suggesting that they are mostly formed outwards from ≃ 20R⋆. The hot lines are centered at −10 km s−1 indicating that they come from a shell between 10 and 20R⋆. 35% of the observed lines are unblended and can be fitted with a code developed to model the emission of a spherically symmetric circumstellar envelope. The analysis of several scenarios reveal that the C2H4 abundance relative to H2 in the range 5 − 20R⋆ is 6.9 × 10−8 in average and it could be as high as 1.1 × 10−7. Beyond 20R⋆, it is 8.2 × 10−8. The total column density is (6.5 ± 3.0) × 1015 cm−2. C2H4 is found to be rotationally under local thermodynamical equilibrium (LTE) and vibrationally out of LTE. One of the scenarios that best reproduce the observations suggests that up to 25% of the C2H4 molecules at 20R⋆ could condense onto dust grains. This possible depletion would not influence significantly the gas acceleration although it could play a role in the surface chemistry on the dust grains. PMID:28184097

  19. FIRST DETECTION OF NEAR-INFRARED LINE EMISSION FROM ORGANICS IN YOUNG CIRCUMSTELLAR DISKS

    Energy Technology Data Exchange (ETDEWEB)

    Mandell, Avi M.; Mumma, Michael J.; Villanueva, Geronimo [Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bast, Jeanette; Van Dishoeck, Ewine F. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Blake, Geoffrey A. [California Institute of Technology, Division of Geological and Planetary Sciences, MS 150-21, Pasadena, CA 91125 (United States); Salyk, Colette, E-mail: Avi.Mandell@nasa.gov [Department of Astronomy, University of Texas, Austin, TX 78712 (United States)

    2012-03-10

    We present an analysis of high-resolution spectroscopy of several bright T Tauri stars using the CRIRES spectrograph on the Very Large Telescope and NIRSPEC spectrograph on the Keck Telescope, revealing the first detections of emission from HCN and C{sub 2}H{sub 2} in circumstellar disks at near-infrared wavelengths. Using advanced data reduction techniques, we achieve a dynamic range with respect to the disk continuum of {approx}500 at 3 {mu}m, revealing multiple emission features of H{sub 2}O, OH, HCN, and C{sub 2}H{sub 2}. We also present stringent upper limits for two other molecules thought to be abundant in the inner disk, CH{sub 4} and NH{sub 3}. Line profiles for the different detected molecules are broad but centrally peaked in most cases, even for disks with previously determined inclinations of greater than 20 Degree-Sign , suggesting that the emission has both a Keplerian and non-Keplerian component as observed previously for CO emission. We apply two different modeling strategies to constrain the molecular abundances and temperatures: we use a simplified single-temperature local thermal equilibrium (LTE) slab model with a Gaussian line profile to make line identifications and determine a best-fit temperature and initial abundance ratios, and we compare these values with constraints derived from a detailed disk radiative transfer model assuming LTE excitation but utilizing a realistic temperature and density structure. Abundance ratios from both sets of models are consistent with each other and consistent with expected values from theoretical chemical models, and analysis of the line shapes suggests that the molecular emission originates from within a narrow region in the inner disk (R < 1 AU).

  20. ALMA Observations of Circumstellar Disks in the Upper Scorpius OB Association

    Science.gov (United States)

    Barenfeld, Scott A.; Carpenter, John M.; Ricci, Luca; Isella, Andrea

    2016-08-01

    We present ALMA observations of 106 G-, K-, and M-type stars in the Upper Scorpius OB Association hosting circumstellar disks. With these data, we measure the 0.88 mm continuum and 12CO J = 3-2 line fluxes of disks around low-mass (0.14-1.66 M ⊙) stars at an age of 5-11 Myr. Of the 75 primordial disks in the sample, 53 are detected in the dust continuum and 26 in CO. Of the 31 disks classified as debris/evolved transitional disks, five are detected in the continuum and none in CO. The lack of CO emission in approximately half of the disks with detected continuum emission can be explained if CO is optically thick but has a compact emitting area (≲40 au), or if the CO is heavily depleted by a factor of at least ˜1000 relative to interstellar medium abundances and is optically thin. The continuum measurements are used to estimate the dust mass of the disks. We find a correlation between disk dust mass and stellar host mass consistent with a power-law relation of {M}{dust}\\propto {M}* 1.67+/- 0.37. Disk dust masses in Upper Sco are compared to those measured in the younger Taurus star-forming region to constrain the evolution of disk dust mass. We find that the difference in the mean of {log}({M}{dust}/{M}* ) between Taurus and Upper Sco is 0.64 ± 0.09, such that M dust/M * is lower in Upper Sco by a factor of ˜4.5.

  1. Heating the Primordial Soup: X-raying the Circumstellar Disk of T Cha

    Science.gov (United States)

    Principe, David; Huenemoerder, D.; Kastner, J. H.; Bessell, M. S.; Sacco, G.

    2014-01-01

    The classical T Tauri Star (cTTS) T Chamaeleontis (T Cha) presents a unique opportunity to probe pre-main sequence star-disk interactions and late-stage circumstellar disk evolution. T Cha is the only known example of a nearly edge-on, actively accreting star/disk system within ~110 pc, and furthermore may be orbited by a low-mass companion or massive planet that has cleared an inner hole in its disk. The star is characterized by strong variability in the optical 3 magnitudes in the V band) as well as large and variable extinction (AV in the range of 1-5). Like most cTTS, T Cha is also a luminous X-ray source. We present preliminary results of two observations (totaling 150 ks) of T Cha with Chandra’s HETGS. Our motivations are to (a) determine the intrinsic X-ray spectrum of T Cha, so as to establish whether its X-ray emission can be attributed to accretion shocks, coronal emission, or a combination; (b) investigate whether its X-ray flux exhibits modulation that may be related to the stellar rotational period 3.3 days); and (c) take advantage of the nearly-edge-on disk viewing geometry to model the spectrum of X-rays absorbed by the gaseous disk orbiting T Cha. These results will serve as much-needed input to models of magnetospheric accretion and irradiated, planet-forming disks. This research is supported via award number GO3-14022X to RIT issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS803060. Additional support is provided by National Science Foundation grant AST-1108950 to RIT.

  2. Circumstellar Light Echo as a Possible Origin of the Polarization of Type IIP Supernovae

    Science.gov (United States)

    Nagao, Takashi; Maeda, Keiichi; Tanaka, Masaomi

    2017-10-01

    Type IIP supernovae (SNe IIP) are the most common class of core-collapse SNe. They often show a rapid increase of polarization degree in the late phase. This time evolution is generally believed to originate from the emergence of an inner aspherical core, while the effect of polarized-scattered echoes by circumstellar (CS) dust around the SN may also substantially contribute to this polarization feature. In this study, we examine the effects of the scattered echoes on the SN polarization through radiative transfer simulations for various geometries and amounts of CS dust. It is found that asymmetrically distributed CS dust, which is generally inferred for red supergiants, can reproduce the observed polarization features. We have applied our results to SNe 2004dj and 2006ov, deriving the geometry and amount of CS dust to explain their observed polarization features in this scenario. For both SNe, the blob-like or bipolar distribution of CS dust rather than the disk-like distribution is favored. The derived dust masses {M}{dust} in the blob model (the bipolar CS dust model) for SNe 2004dj and 2006ov are ∼ 7.5× {10}-4 {M}ȯ (∼ 8.5× {10}-4 {M}ȯ ) and ∼ 5.2× {10}-4 {M}ȯ (∼ 1.3× {10}-3 {M}ȯ ), respectively. Even in the case where this process would not play a dominant role in the observed polarization signals, this effect should in principle contribute to it, the strength of which depends on the nature of the CS dust. Therefore, this effect must be taken into account in discussing the multi-dimensional structure of an SN explosion through polarimetric observations.

  3. Circumstellar Dust Composition of M-type Mira Variables observed with phase with Spitzer

    Science.gov (United States)

    Güth, Tina; Creech-Eakman, Michelle J.

    2017-01-01

    Our research concerns the detailed dust composition surrounding Mira variables. These regular pulsators are easily observed in the optical and infrared due to their changes in brightness. Data on 25 galactic Miras were obtained with the Spitzer Infrared Spectrograph (IRS) instrument in 2008-09 under a GO program led by Creech-Eakman. The stars were observed approximately once per month to track changes in their brightness and spectral features. This dataset is unique for both the number of observations of each star and the high SNR due to their intrinsic brightness.The stars in this study span the range of oxygen- to carbon-rich, with each type exhibiting certain known solid state components (i.e dust). The current focus is on trying to reproduce dust spectral features in the short, high (SH) and long, high (LH) resolution wavelength range (~9.7 - 40 microns) of the oxygen-rich Miras (C/O features that provide insight into the stellar atmospheres and circumstellar dust composition with phase.Using the 1-D radiative transfer modeling code, DUSTY, we are attempting to identify several broad, and some sharp, dust features by including recently derived laboratory spectral indices for dust opacities. Prominent features seen in oxygen-rich Mira variables include potential identifications of water ice emission, as well as amorphous and crystalline silicates. We implement a greybody continuum obtained from MARCS, a 1-D hydrostatic spherical LTE model grid code, as the stellar continuum input for DUSTY. Using a greybody rather than a blackbody curve allows us to obtain a better agreement between the DUSTY spectrum and the Spitzer data. We will show these amended model fits that will improve the identification of the dust and other features in the spectra.

  4. THE REINCARNATION OF INTERSTELLAR DUST: THE IMPORTANCE OF ORGANIC REFRACTORY MATERIAL IN INFRARED SPECTRA OF COMETARY COMAE AND CIRCUMSTELLAR DISKS

    Energy Technology Data Exchange (ETDEWEB)

    Kimura, Hiroshi, E-mail: hiroshi_kimura@cps-jp.org [Graduate School of Science, Kobe University, c/o CPS (Center for Planetary Science), Chuo-ku Minatojima Minamimachi 7-1-48, Kobe 650-0047 (Japan)

    2013-09-20

    We consider the reincarnation of interstellar dust to be reborn in protoplanetary disks as aggregates consisting of submicron-sized grains with a crystalline or amorphous silicate core and an organic-rich carbonaceous mantle. We find that infrared spectra of reincarnated interstellar dust reproduce emission peaks at correct wavelengths where the peaks were observed in cometary comae, debris disks, and protoplanetary disks if the volume fraction of organic refractory meets the constraints on elemental abundances. We discuss what we can learn from the infrared spectra of reincarnated interstellar dust in cometary comae and circumstellar disks.

  5. The Reincarnation of Interstellar Dust: The Importance of Organic Refractory Material in Infrared Spectra of Cometary Comae and Circumstellar Disks

    Science.gov (United States)

    Kimura, Hiroshi

    2013-09-01

    We consider the reincarnation of interstellar dust to be reborn in protoplanetary disks as aggregates consisting of submicron-sized grains with a crystalline or amorphous silicate core and an organic-rich carbonaceous mantle. We find that infrared spectra of reincarnated interstellar dust reproduce emission peaks at correct wavelengths where the peaks were observed in cometary comae, debris disks, and protoplanetary disks if the volume fraction of organic refractory meets the constraints on elemental abundances. We discuss what we can learn from the infrared spectra of reincarnated interstellar dust in cometary comae and circumstellar disks.

  6. 闭环供应链环境下纺织服装业组织运作模式%Study on Organization and Operation Mode of Textile and Garment Industry under Closed-loop Supply Chain Environment

    Institute of Scientific and Technical Information of China (English)

    郑飞

    2015-01-01

    In this paper,through analyzing the definition and structure of the closed-loop supply chain of the textile and garment industry and comparing it with that of the traditional supply chain,we discussed the advantage of the enterprises on the closed-supply chains in terms of waste recycling,development mode,corporate pursuit,and social benefit,etc.,introduced,for the first time,the closed-loop supply chain structure into the textile and garment industry,and at the end,designed the three operational modes of the closed-loop supply chain of the textile and garment industry.%通过纺织服装业闭环供应链内涵界定、结构分析及与传统供应链的对比分析,发掘出纺织服装业闭环供应链企业的回收再利用效率、企业发展模式、企业追求目标、社会效益等方面的优势,首次将闭环供应链的思想引入纺织服装业中,设计了基于循环使用、再利用、再循环的纺织服装业闭环供应链的三种运作模式.

  7. What limits the application of wastewater and/or closed cycle in horticulture? (VIII International Symposium on Protected Cultivation in Mild Winter Climates: Advances in Soil and Soilless Cultivation under Protected Environment (Aug 2007)

    NARCIS (Netherlands)

    Stanghellini, C.; Pardossi, A.; Sigrimis, N.

    2007-01-01

    We determine the ¿optimal¿ management of a closed growing system with multiple sources of water, of price decreasing with quality. The management that balances marginal costs of water and fertilizers with marginal yield loss is determined. By using a number of yield response curves, in a couple of d

  8. Location and origin of dust in circumstellar debris disks: A mid-infrared imaging study

    Science.gov (United States)

    Moerchen, Margaret Marie

    Approximately one third of A-type stars host dusty disks beyond the expected timescales for dissipation of the primordial disk material. The primordial dust particles may either be blown out by radiation pressure from the star or they may experience destructive collisions that generate smaller particles that are then blown out of the system. We infer from the sustained presence of the dust that it must be resupplied through collisions of already-formed planets and planetesimals or through the sublimation of cometary bodies, and systems with such dust are called debris disks. Since the 1984 discovery of the debris disk Vega, observations of circumstellar debris disks have revealed the presence planetary systems that would otherwise have remained unknown. In this work, we set out to find asymmetric structures in debris disks that would indicate a physical process sculpting the disk, such as a catastrophic planetesimal collision that generates a bright region of newly-formed dust, or a clumpy pattern comprised of dust that is trapped in an orbital resonance with a giant planet. We obtained high spatial resolution ([Special characters omitted.] 0.5") images of the thermally emitting dust in 21 debris disk candidates (some of which are now known not to be debris disks), and in most cases we did not detect any brightness asymmetry nor was the source even spatially resolved. However, among the resolved disks, we have discovered several structures that may be analogous to those in our own solar system, such as a potential asteroid belts (in z Lep) and a snow line (in HD 32297). One brightness asymmetry is seen, in the disk of 16 HR 4796A, and we have determined that the bright side of the disk is also hotter than the opposite side. We review the possible origins of such a temperature asymmetry in the dust disk, such as pericenter glow and resonant trapping, and this investigation is ongoing. More generally, two disk archetypes are observed among all of the disks in this

  9. The HD 163296 Circumstellar Disk in Scattered Light: Evidence of Time-Variable Self-Shadowing

    Science.gov (United States)

    Wisniewski, John P.; Clampin, Mark; Grady, Carol A.; Ardila, David R.; Ford, Holland C.; Golimowski, David A.; Illingworth, Garth D.; Krist, John E.

    2008-01-01

    We present the first multi-color view of the scattered light disk of the Herbig Ae star HD 163296, based on coronagraphic observations from the Hubble Space Telescope Advanced Camera for Surveys (ACS). Radial profile fits of the surface brightness along the disk's semi-major axis indicates that the disk is not continuously flared, and extends to approx.540 AU. The disk's color (V-I)=1.1 at a radial distance of 3.5" is redder than the observed stellar color (V-I)=0.15. This red disk color might be indicative of either an evolution in the grain size distribution (i.e. grain growth) and/or composition, both of which would be consistent with the observed non-flared geometry of the outer disk. We also identify a single ansa morphological structure in our F435W ACS data, which is absent from earlier epoch F606W and F814W ACS data, but corresponds to one of the two ansa observed in archival HST STIS coronagraphic data. Following transformation to similar band-passes, we find that the scattered light disk of HD 163296 is 1 mag arcsec(sup -2) fainter at 3.5" in the STIS data than in the ACS data. Moreover, variations are seen in (i) the visibility of the ansa(e) structures, in (ii) the relative surface brightness of the ansa(e) structures, and in (iii) the (known) intrinsic polarization of the system. These results indicate that the scattered light from the HD 163296 disk is variable. We speculate that the inner disk wall, which Sitko et al. suggests has a variable scale height as diagnosed by near-IR SED variability, induces variable self-shadowing of the outer disk. We further speculate that the observed surface brightness variability of the ansa(e) structures may indicate that the inner disk wall is azimuthally asymmetric. Subject headings: circumstellar matter - stars: individual (HD 163296) - planetary systems: formation - planetary systems: protoplanetary disks

  10. CARMA CO(J = 2 - 1) OBSERVATIONS OF THE CIRCUMSTELLAR ENVELOPE OF BETELGEUSE

    Energy Technology Data Exchange (ETDEWEB)

    O' Gorman, Eamon; Harper, Graham M. [School of Physics, Trinity College Dublin, Dublin 2 (Ireland); Brown, Joanna M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS-78, Cambridge, MA 02138 (United States); Brown, Alexander [Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309-0389 (United States); Redfield, Seth [Astronomy Department, Van Vleck Observatory, Wesleyan University, Middletown, CT 06459 (United States); Richter, Matthew J. [Physics Department, UC Davis, 1 Shields Avenue, Davis, CA 95616 (United States); Requena-Torres, Miguel A. [Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn (Germany)

    2012-08-15

    We report radio interferometric observations of the {sup 12}C{sup 16}O 1.3 mm J = 2 - 1 emission line in the circumstellar envelope of the M supergiant {alpha} Ori and have detected and separated both the S1 and S2 flow components for the first time. Observations were made with the Combined Array for Research in Millimeter-wave Astronomy (CARMA) interferometer in the C, D, and E antenna configurations. We obtain good u - v coverage (5-280 k{lambda}) by combining data from all three configurations allowing us to trace spatial scales as small as 0.''9 over a 32'' field of view. The high spectral and spatial resolution C configuration line profile shows that the inner S1 flow has slightly asymmetric outflow velocities ranging from -9.0 km s{sup -1} to +10.6 km s{sup -1} with respect to the stellar rest frame. We find little evidence for the outer S2 flow in this configuration because the majority of this emission has been spatially filtered (resolved out) by the array. We also report a SOFIA-GREAT CO(J = 12 - 11) emission line profile, which we associate with this inner higher excitation S1 flow. The outer S2 flow appears in the D and E configuration maps and its outflow velocity is found to be in good agreement with high-resolution optical spectroscopy of K I obtained at the McDonald Observatory. We image both S1 and S2 in the multi-configuration maps and see a gradual change in the angular size of the emission in the high absolute velocity maps. We assign an outer radius of 4'' to S1 and propose that S2 extends beyond CARMA's field of view (32'' at 1.3 mm) out to a radius of 17'', which is larger than recent single-dish observations have indicated. When azimuthally averaged, the intensity falloff for both flows is found to be proportional to R{sup -1}, where R is the projected radius, indicating optically thin winds with {rho}{proportional_to}R{sup -2}.

  11. Ecological Challenges for Closed Systems

    Science.gov (United States)

    Nelson, Mark; Dempster, William; Allen, John P.

    2012-07-01

    Closed ecological systems are desirable for a number of purposes. In space life support systems, material closure allows precious life-supporting resources to be kept inside and recycled. Closure in small biospheric systems facilitates detailed measurement of global ecological processes and biogeochemical cycles. Closed testbeds facilitate research topics which require isolation from the outside (e.g. genetically modified organisms; radioisotopes) so their ecological interactions and fluxes can be studied separate from interactions with the outside environment. But to achieve and maintain closure entails solving complex ecological challenges. These challenges include being able to handle faster cycling rates and accentuated daily and seasonal fluxes of critical life elements such as carbon dioxide, oxygen, water, macro- and mico-nutrients. The problems of achieving sustainability in closed systems for life support include how to handle atmospheric dynamics including trace gases, producing a complete human diet and recycling nutrients and maintaining soil fertility, the sustaining of healthy air and water and preventing the loss of crucial elements from active circulation. In biospheric facilities the challenge is also to produce analogues to natural biomes and ecosystems, studying processes of self-organization and adaptation in systems that allow specification or determination of state variables and cycles which may be followed through all interactions from atmosphere to soils. Other challenges include the dynamics and genetics of small populations, the psychological challenges for small isolated human groups and measures and options which may be necessary to ensure long-term operation of closed ecological systems.

  12. POLARIMETRY WITH THE GEMINI PLANET IMAGER: METHODS, PERFORMANCE AT FIRST LIGHT, AND THE CIRCUMSTELLAR RING AROUND HR 4796A

    Energy Technology Data Exchange (ETDEWEB)

    Perrin, Marshall D. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Duchene, Gaspard; Graham, James R.; Kalas, Paul G. [Astronomy Department, University of California, Berkeley, Hearst Field Annex B-20, Berkeley, CA 94720-3411 (United States); Millar-Blanchaer, Max [Department of Astronomy and Astrophysics, University of Toronto, Toronto ON M5S 3H4 (Canada); Fitzgerald, Michael P.; Chilcote, Jeffrey [Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095 (United States); Wiktorowicz, Sloane J.; Dillon, Daren; Gavel, Donald [Department of Astronomy, UC Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Macintosh, Bruce; Bauman, Brian [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94040 (United States); Cardwell, Andrew; Goodsell, Stephen; Hartung, Markus; Hibon, Pascale [Gemini Observatory, Casilla 603 La Serena (Chile); De Rosa, Robert J. [School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287 (United States); Doyon, René [Department de Physique, Université de Montréal, Montréal QC H3C 3J7 (Canada); Dunn, Jennifer; Erikson, Darren [National Research Council of Canada Herzberg, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); and others

    2015-02-01

    We present the first results from the polarimetry mode of the Gemini Planet Imager (GPI), which uses a new integral field polarimetry architecture to provide high contrast linear polarimetry with minimal systematic biases between the orthogonal polarizations. We describe the design, data reduction methods, and performance of polarimetry with GPI. Point-spread function (PSF) subtraction via differential polarimetry suppresses unpolarized starlight by a factor of over 100, and provides sensitivity to circumstellar dust reaching the photon noise limit for these observations. In the case of the circumstellar disk around HR 4796A, GPI's advanced adaptive optics system reveals the disk clearly even prior to PSF subtraction. In polarized light, the disk is seen all the way in to its semi-minor axis for the first time. The disk exhibits surprisingly strong asymmetry in polarized intensity, with the west side ≳ 9 times brighter than the east side despite the fact that the east side is slightly brighter in total intensity. Based on a synthesis of the total and polarized intensities, we now believe that the west side is closer to us, contrary to most prior interpretations. Forward scattering by relatively large silicate dust particles leads to the strong polarized intensity on the west side, and the ring must be slightly optically thick in order to explain the lower brightness in total intensity there. These findings suggest that the ring is geometrically narrow and dynamically cold, perhaps shepherded by larger bodies in the same manner as Saturn's F ring.

  13. Nearby Supernova Factory Observations of SN 2005gj: Another Type Ia Supernova in a Massive Circumstellar Envelope

    CERN Document Server

    Aldering, G; Bailey, S; Baltay, C; Bauer, A; Blanc, N; Bongard, S; Copin, Y; Gangler, E; Gilles, S; Kessler, R; Kocevski, D; Lee, B C; Loken, S; Nugent, P; Pain, R; Pécontal, E; Pereira, R; Perlmutter, S; Rabinowitz, D; Rigaudier, G; Scalzo, R; Smadja, G; Thomas, R C; Wang, L; Weaver, B A

    2006-01-01

    We report Nearby Supernova Factory observations of SN 2005gj, the second confirmed case of a "hybrid" Type Ia/IIn supernova. Our early-phase photometry of SN 2005gj shows that the interaction is much stronger than for the prototype, SN 2002ic. Our first spectrum shows a hot continuum with broad and narrow H-alpha emission. Later spectra, spanning over 4 months from outburst, show clear Type Ia features combined with broad and narrow H-gamma, H-beta, H-alpha and HeI 5876,7065 in emission. At higher resolution, P Cygni profiles are apparent. Surprisingly, we also observe an inverted P Cygni profile for [OIII] 5007. We find that the lightcurve and measured velocity of the unshocked circumstellar material imply mass loss as recently as 8 years ago. The early lightcurve is well-described by a flat radial density profile for the circumstellar material. However, our decomposition of the spectra into Type Ia and shock emission components allows for little obscuration of the supernova, suggesting an aspherical or clum...

  14. Rapid Circumstellar Disk Evolution and an Accelerating Star Formation Rate in the Infrared Dark Cloud M17 SWex

    CERN Document Server

    Povich, Matthew S; Robitaille, Thomas P; Broos, Patrick S; Orbin, Wesley T; King, Robert R; Naylor, Tim; Whitney, Barbara A

    2016-01-01

    We present a catalog of 840 X-ray sources and first results from a 100 ks Chandra X-ray Observatory imaging study of the filamentary infrared dark cloud G014.225$-$00.506, which forms the central regions of a larger cloud complex known as the M17 southwest extension (M17 SWex). In addition to the rich population of protostars and young stellar objects with dusty circumstellar disks revealed by Spitzer Space Telescope archival data, we discover a population of X-ray-emitting, intermediate-mass pre--main-sequence stars (IMPS) that lack infrared excess emission from circumstellar disks. We model the infrared spectral energy distributions of this source population to measure its mass function and place new constraints on the inner dust disk destruction timescales for 2-8 $M_{\\odot}$ stars. We also place a lower limit on the star formation rate (SFR) and find that it is quite high ($\\dot{M}\\ge 0.007~M_{\\odot}$ yr$^{-1}$), equivalent to several Orion Nebula Clusters in G14.225$-$0.506 alone, and likely accelerating...

  15. SEARCH FOR CIRCUMSTELLAR DISKS AND RADIO JETS IN THE MASSIVE STAR-FORMATION REGION IRAS 23033+5951

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez, T.; Trinidad, M. A. [Departamento de Astronomia, Universidad de Guanajuato, Apdo. Postal 144, Guanajuato, Gto. 36240 (Mexico); Migenes, V., E-mail: tatiana@iga.cu, E-mail: trinidad@astro.ugto.mx, E-mail: vmigenes@byu.edu [Brigham Young University, Department of Physics and Astronomy, ESC-N145, Provo, UT 84602 (United States)

    2012-08-20

    We present radio continuum (1.3 and 3.6 cm) and H{sub 2}O maser observations toward the high-mass star-forming region IRAS 23033+5951 carried out with the VLA-EVLA (in transition phase) in the A configuration. Three radio continuum sources are detected at 3.6 cm, which are aligned in the east-west direction. However, no continuum emission is detected in the region at 1.3 cm. Based on the continuum information, we find that the two continuum sources detected in the region could be consistent with ultracompact H II regions harboring ZAMS B2 and B2.5 stars; however, we do not rule out that they could be associated with a radio jet. In addition, nine water maser spots are detected toward IRAS 23033+5951, which are clustered in two groups and located about 2'' to the south of the continuum sources. The spatio-kinematical distribution of the water masers suggests that they are tracing a circumstellar disk associated with a central star ZAMS B0, which could be the least evolved source in the region and has not developed an H II region yet. Moreover, as the circumstellar disk seems to be associated with the CO molecular outflow observed in the region, this conforms to a disk-YSO-outflow system, similar to that found in low-mass stars.

  16. The circumstellar shell of the post-AGB star HD 56126 the $^{12}CN\\/^{13}CN$ isotope ratio and fractionation

    CERN Document Server

    Bakker, E J; Bakker, Eric J.; Lambert, David L.

    1997-01-01

    We have detected circumstellar absorption lines of the $^{12}$CN and $^{13}$CN Violet and Red System in the spectrum of the post-AGB star HD~56126. From a synthetic spectrum analysis, we derive a Doppler broadening parameter of $b=0.51\\pm0.04$ km~s$^{-1}$, $^{12}$CN/$^{13}$CN$=38\\pm2$, and a lower limit of $2000$ on $^{12}$CN/$^{14}$CN and $^{12}$C$^{14}$N/$^{12}$C$^{15}$N. A simple chemical model has been computed of the circumstellar shell surrounding HD~56126 that takes into account the gas-phase ion-molecule reaction between CN and C$^{+}$. From this we infer that this reaction leads to isotopic fractionation of CN. Taking into account the isotopic exchange reaction and the observed $^{12}$CN/$^{13}$CN we find $^{12}$C/$^{13}$C$\\sim 67$ (for $T_{\\rm kin}=25$ K). Our analysis suggests that $^{12}$CN has a somewhat higher rotational temperature than $^{13}$CN: $T_{\\rm rot}=11.5\\pm0.6$ and $8.0\\pm0.6$ K respectively. We identify possible causes for this difference in excitation temperature, among which the $...

  17. Growth of a Protostar and a Young Circumstellar Disk with High Mass Accretion Rate onto the Disk

    CERN Document Server

    Ohtani, Takuya

    2013-01-01

    The growing process of both a young protostar and a circumstellar disk is investigated. Viscous evolution of a disk around a single star is considered with a model where a disk increases its mass by dynamically accreting envelope and simultaneously loses its mass via viscous accretion onto the central star. We focus on the circumstellar disk with high mass accretion rate onto the disk $\\dot{M}=8.512c_{\\rm s}^3/G$ as a result of dynamical collapse of rotating molecular cloud core. We study the origin of the surface density distribution and the origin of the disk-to-star mass ratio by means of numerical calculations of unsteady viscous accretion disk in one-dimensional axisymmetric model. It is shown that the radial profiles of the surface density $\\Sigma$, azimuthal velocity $v_{\\phi}$, and mass accretion rate $\\dot{M}$ in the inner region approach to the quasi-steady state. Profile of the surface density distribution in the quasi-steady state is determined as a result of angular momentum transport rather than...

  18. A search for precursors of Ultracompact HII Regions in a sample of luminous IRAS sources; 3, Circumstellar Dust Properties

    CERN Document Server

    Molinari, S; Cesaroni, R; Palla, Fabrizio; Molinari, Sergio; Brand, Jan; Cesaroni, Riccardo; Palla, Francesco

    2000-01-01

    The James Clerk Maxwell Telescope has been used to obtain submillimeter and millimeter continuum photometry of a sample of 30 IRAS sources previously studied in molecular lines and centimeter radio continuum. All the sources have IRAS colours typical of very young stellar objects (YSOs) and are associated with dense gas. In spite of their high luminosities (L>10000 solar units), only ten of these sources are also associated with a radio counterpart. In 17 cases we could identify a clear peak of millimeter emission associated with the IRAS source, while in 9 sources the millimeter emission was extended or faint and a clear peak could not be identified; upper limits were found in 4 cases only. Using simple greybody fitting model to the observed SED, we derive global properties of the circumstellar dust. The dust temperature varies from 24 K to 45 K, while the exponent of the dust emissivity vs frequency power-law spans a range 1.56circumstellar masses ran...

  19. Polarimetry with the Gemini Planet Imager: methods, performance at first light, and the circumstellar ring around HR 4796A

    Energy Technology Data Exchange (ETDEWEB)

    Perrin, Marshall D.; Duchene, Gaspard; Millar-Blanchaer, Max; Fitzgerald, Michael P.; Graham, James R.; Wiktorowicz, Sloane J.; Kalas, Paul G.; Macintosh, Bruce; Bauman, Brian; Cardwell, Andrew; Chilcote, Jeffrey; De Rosa, Robert J.; Dillon, Daren; Doyon, René; Dunn, Jennifer; Erikson, Darren; Gavel, Donald; Goodsell, Stephen; Hartung, Markus; Hibon, Pascale; Ingraham, Patrick; Kerley, Daniel; Konapacky, Quinn; Larkin, James E.; Maire, Jérôme; Marchis, Franck; Marois, Christian; Mittal, Tushar; Morzinski, Katie M.; Oppenheimer, B. R.; Palmer, David W.; Patience, Jennifer; Poyneer, Lisa; Pueyo, Laurent; Rantakyrö, Fredrik T.; Sadakuni, Naru; Saddlemyer, Leslie; Savransky, Dmitry; Soummer, Rémi; Sivaramakrishnan, Anand; Song, Inseok; Thomas, Sandrine; Wallace, J. Kent; Wang, Jason J.; Wolff, Schuyler G.

    2015-01-28

    We present the first results from the polarimetry mode of the Gemini Planet Imager (GPI), which uses a new integral field polarimetry architecture to provide high contrast linear polarimetry with minimal systematic biases between the orthogonal polarizations. We describe the design, data reduction methods, and performance of polarimetry with GPI. Point spread function subtraction via di erential polarimetry suppresses unpolarized starlight by a factor of over 100, and provides sensitivity to circumstellar dust reaching the photon noise limit for these observations. In the case of the circumstellar disk around HR 4796A, GPI's advanced adaptive optics system reveals the disk clearly even prior to PSF subtraction. In polarized light, the disk is seen all the way in to its semi-minor axis for the first time. The disk exhibits surprisingly strong asymmetry in polarized intensity, with the west side ≳ 9 times brighter than the east side despite the fact that the east side is slightly brighter in total intensity. Based on a synthesis of the total and polarized intensities, we now believe that the west side is closer to us, contrary to most prior interpretations. Forward scattering by relatively large silicate dust particles leads to the strong polarized intensity on the west side, and the ring must be slightly optically thick in order to explain the lower brightness in total intensity there. These findings suggest that the ring is geometrically narrow and dynamically cold, perhaps shepherded by larger bodies in the same manner as Saturn's F ring.

  20. Metamorphosis of SN 2014C: Delayed Interaction Between a Hydrogen Poor Core-collapse Supernova and a Nearby Circumstellar Shell

    CERN Document Server

    Milisavljevic, D; Kamble, A; Patnaude, D; Raymond, J; Eldridge, J; Fong, W; Bietenholz, M; Challis, P; Chornock, R; Drout, M; Fransson, C; Fesen, R; Grindlay, J; Kirshner, R; Lunnan, R; Mackey, J; Miller, G; Parrent, J; Sanders, N; Soderberg, A; Zauderer, B

    2015-01-01

    We present optical observations of supernova SN 2014C, which underwent an unprecedented slow metamorphosis from H-poor type Ib to H-rich type IIn over the course of one year. The observed spectroscopic evolution is consistent with the supernova having exploded in a cavity before encountering a massive shell of the progenitor star's stripped hydrogen envelope. Possible origins for the circumstellar shell include a brief Wolf-Rayet fast wind phase that overtook a slower red supergiant wind, eruptive ejection, or confinement of circumstellar material by external influences of neighboring stars. An extended high velocity Halpha absorption feature seen in near-maximum light spectra implies that the progenitor star was not completely stripped of hydrogen at the time of core collapse. Archival pre-explosion Subaru Telescope Suprime-Cam and Hubble Space Telescope Wide Field Planetary Camera 2 images of the region obtained in 2009 show a coincident source that is most likely a compact massive star cluster in NGC 7331 ...

  1. The T Tauri star RY Tau as a case study of the inner regions of circumstellar dust disks

    CERN Document Server

    Schegerer, A A; Ratzka, Th; Leinert, Ch

    2007-01-01

    We study the inner region of the circumstellar disk around the TTauri star RY Tau. Our aim is to find a physical description satisfying the available interferometric data, obtained with the mid-infrared interferometric instrument at the Very Large Telescope Interferometer, as well as the spectral energy distribution. We also compare the findings with the results of similar studies, including those of intermediate-mass stars. Our analysis is done within the framework of a passive circumstellar disk, which is optionally supplemented by the effects of accretion and an added envelope. To achieve a more consistent and realistic model, we used our continuum transfer code MC3D. In addition, we studied the shape of the 10um silicate emission feature in terms of the underlying dust population, both for single-dish and for interferometric measurements. We show that a modestly flaring disk model with accretion can explain both the observed spectral energy distribution and the mid-infrared visibilities obtained with the ...

  2. Resolving the inner regions of the HD 97048 circumstellar disk with VLT/NACO polarimetric differential imaging

    Science.gov (United States)

    Quanz, S. P.; Birkmann, S. M.; Apai, D.; Wolf, S.; Henning, T.

    2012-02-01

    Context. Circumstellar disks are the cradles of planetary systems and their physical and chemical properties directly influence the planet formation process. Because most planets supposedly form in the inner disk regions, i.e., within a few tens of AU, it is crucial to study circumstellar disks on these scales to constrain the conditions for planet formation. Aims: Our aims are to characterize the inner regions of the circumstellar disk around the young Herbig Ae/Be star HD 97048 in polarized light. Methods: We used VLT/NACO to observe HD 97048 in polarimetric differential imaging (PDI) mode in the H and Ks band. This technique offers high-contrast capabilities at very small inner working angles and probes the dust grains on the surface layer of the disk that act as the scattering surface. Results: We spatially resolve the disk around HD 97048 in polarized flux in both filters on scales between ~0.1″-1.0″ corresponding to the inner ~16-160 AU. Fitting isophots to the flux calibrated H-band image between 13-14 mag/arcsec2 and 14-15 mag/arcsec2, we derive an apparent disk inclination angle of 34° ± 5° and 47° ± 2°, respectively. The disk position angle in both brightness regimes is almost identical and roughly 80°. Along the disk major axis the surface brightness of the polarized flux drops from ~11 mag/arcsec2 at ~0.1″ (~16 AU) to ~15.3 mag/arcsec2 at ~ 1.0″ (~160 AU). The brightness profiles along the major axis are fitted with power-laws falling off as ∝ r - 1.78 ± 0.02 in H and ∝ r - 2.34 ± 0.04 in Ks. Because the surface brightness decreases more rapidly in Ks compared to H, the disks becomes relatively bluer at larger separations, possibly indicating changing dust grain properties as a function of radius. Conclusions: We imaged for the first time the inner ~0.1″-1.0″ (~16-160 AU) of the surface layer of the HD 97048 circumstellar disk in scattered light, which demonstrates the power of ground-based imaging polarimetry. Our data fill an

  3. Close-ups

    DEFF Research Database (Denmark)

    Fausing, Bent

    2013-01-01

    Investigations in the close-up and its meaning regarding nearness, abstraction and transparency. Face, facelike and animism are also major key-words in thsi article... . I have always been fascinated with the close-up, not as an end, but a filter of opportunities to open up for and nearness of tr...

  4. Surviving a School Closing

    Science.gov (United States)

    De Witt, Peter M.; Moccia, Josephine

    2011-01-01

    When a beloved school closes, community emotions run high. De Witt and Moccia, administrators in the Averill Park School District in upstate New York, describe how their district navigated through parents' anger and practical matters in closing a small neighborhood elementary school and transferring all its students to another school. With a group…

  5. Close to the Sky

    Science.gov (United States)

    2007-11-01

    Today, a new ALMA outreach and educational book was publicly presented to city officials of San Pedro de Atacama in Chile, as part of the celebrations of the anniversary of the Andean village. ESO PR Photo 50a/07 ESO PR Photo 50a/07 A Useful Tool for Schools Entitled "Close to the sky: Biological heritage in the ALMA area", and edited in English and Spanish by ESO in Chile, the book collects unique on-site observations of the flora and fauna of the ALMA region performed by experts commissioned to investigate it and to provide key initiatives to protect it. "I thank the ALMA project for providing us a book that will surely be a good support for the education of children and youngsters of San Pedro de Atacama. Thanks to this publication, we expect our rich flora and fauna to be better known. I invite teachers and students to take advantage of this educational resource, which will be available in our schools", commented Ms. Sandra Berna, the Mayor of San Pedro de Atacama, who was given the book by representatives of the ALMA global collaboration project. Copies of the book 'Close to the sky' will be donated to all schools in the area, as a contribution to the education of students and young people in northern Chile. "From the very beginning of the project, ALMA construction has had a firm commitment to environment and local culture, protecting unique flora and fauna species and preserving old estancias belonging to the Likan Antai culture," said Jacques Lassalle, who represented ALMA at the hand-over. "Animals like the llama, the fox or the condor do not only live in the region where ALMA is now being built, but they are also key elements of the ancient Andean constellations. In this sense they are part of the same sky that will be explored by ALMA in the near future." ESO PR Photo 50c/07 ESO PR Photo 50c/07 Presentation of the ALMA book The ALMA Project is a giant, international observatory currently under construction on the high-altitude Chajnantor site in Chile

  6. Synthetic environments

    Science.gov (United States)

    Lukes, George E.; Cain, Joel M.

    1996-02-01

    The Advanced Distributed Simulation (ADS) Synthetic Environments Program seeks to create robust virtual worlds from operational terrain and environmental data sources of sufficient fidelity and currency to interact with the real world. While some applications can be met by direct exploitation of standard digital terrain data, more demanding applications -- particularly those support operations 'close to the ground' -- are well-served by emerging capabilities for 'value-adding' by the user working with controlled imagery. For users to rigorously refine and exploit controlled imagery within functionally different workstations they must have a shared framework to allow interoperability within and between these environments in terms of passing image and object coordinates and other information using a variety of validated sensor models. The Synthetic Environments Program is now being expanded to address rapid construction of virtual worlds with research initiatives in digital mapping, softcopy workstations, and cartographic image understanding. The Synthetic Environments Program is also participating in a joint initiative for a sensor model applications programer's interface (API) to ensure that a common controlled imagery exploitation framework is available to all researchers, developers and users. This presentation provides an introduction to ADS and the associated requirements for synthetic environments to support synthetic theaters of war. It provides a technical rationale for exploring applications of image understanding technology to automated cartography in support of ADS and related programs benefitting from automated analysis of mapping, earth resources and reconnaissance imagery. And it provides an overview and status of the joint initiative for a sensor model API.

  7. Skew-closed categories

    CERN Document Server

    Street, Ross

    2012-01-01

    Spurred by the new examples found by Kornel Szlach\\'anyi of a form of lax monoidal category, the author felt the time ripe to publish a reworking of Eilenberg-Kelly's original paper on closed categories appropriate to the laxer context. The new examples are connected with bialgebroids. With Stephen Lack, we have also used the concept to give an alternative definition of quantum category and quantum groupoid. Szlach\\'anyi has called the lax notion {\\em skew monoidal}. This paper defines {\\em skew closed category}, proves Yoneda lemmas for categories enriched over such, and looks at closed cocompletion.

  8. Closed Claim Query File

    Data.gov (United States)

    Social Security Administration — This file is used to hold information about disability claims that have been closed and have been selected for sampling.Sampling is the process whereby OQR reviews...

  9. Mitigation : Closed Basin Project

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The upcoming meeting on waterfowl mitigation for the Closed Basin Project will have several people talk about possible changes to the waterfowl mitigation program. A...

  10. Geology and health:closing the gap

    Institute of Scientific and Technical Information of China (English)

    A.B.Kampunzu

    2004-01-01

    It was discovered several decades ago that the natural geo-environment could substantially impact on the health of animals and humans. However, despite the growth of evidence supporting this discovery, there has not been a close interaction between geoscientists and health scientists in assessing the need to study the various facets of the relationships between human and animal health and air, water, soils and rocks. This book is timely in closing that gap as stated in its title.

  11. DIGIT, GASPS, DEBRIS and DUNES: four HERSCHEL Open Time Key Programs to survey the dust cycle in circumstellar disks

    Science.gov (United States)

    Augereau, J.-C.; Absil, O.; Bouvier, J.; Duchêne, G.; Lestrade, J.-F.; Maret, S.; Martin-Zaïdi, C.; Ménard, F.; Morbidelli, A.; Olofsson, J.; Pantin, E.; Pinte, C.; Thébault, P.

    2008-11-01

    Four accepted HERSCHEL open time key programs, DIGIT, GASPS, DEBRIS and DUNES, will study the evolution of the dust grains in circumstellar disks around young and Main Sequence stars. There is a strong implication of the french community in these four projects which represent a total of 930 hours (>38 days) of her\\ observing time. The DIGIT and GASPS projects will focus on the first stages of planet formation, while the DEBRIS and DUNES projects will search for extra-solar Kuiper Belt analogs around nearby Main Sequence stars. In this paper, we give an overview of the scientific goals of the four projects and of the numerical tools that we will be providing to the teams to model and interpret the her\\ observations from these programs.

  12. SN 2010mb: Direct evidence for a supernova interacting with a large amount of hydrogen-free circumstellar material

    Energy Technology Data Exchange (ETDEWEB)

    Ben-Ami, Sagi; Gal-Yam, Avishay; Rabinak, Itay; Yaron, Ofer; Arcavi, Iair; Ofek, Eran O. [Department of Particle Physics and Astrophysics, The Weizmann Institute of Science, Rehovot 76100 (Israel); Mazzali, Paolo A. [Astrophysics Research Institute, Liverpool John Moores University. Liverpool L3 5RF (United Kingdom); Gnat, Orly [Racah Institute of Physics, The Hebrew University, 91904 Jerusalem (Israel); Modjaz, Maryam [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, room 529, New York, NY 10003 (United States); Sullivan, Mark [Department of Physics (Astrophysics), University of Oxford, DWB, Keble Road, Oxford, OX1 3RH (United Kingdom); Bildsten, Lars [Kavli Institute for Theoretical Physics and Department of Physics Kohn Hall, University of California, Santa Barbara, CA 93106 (United States); Poznanski, Dovi [School of Physics and Astronomy, Tel-Aviv University, Tel Aviv 69978 Israel (Israel); Bloom, Joshua S.; Nugent, Peter E. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Horesh, Assaf; Kulkarni, Shrinivas R.; Perley, Daniel [Cahill Center for Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Kasliwal, Mansi M. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Quimby, Robert [Kavli IPMU, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8583 (Japan); Xu, Dong, E-mail: sagi.ben-ami@weizmann.ac.il [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark)

    2014-04-10

    We present our observations of SN 2010mb, a Type Ic supernova (SN) lacking spectroscopic signatures of H and He. SN 2010mb has a slowly declining light curve (LC) (∼600 days) that cannot be powered by {sup 56}Ni/{sup 56}Co radioactivity, the common energy source for Type Ic SNe. We detect signatures of interaction with hydrogen-free circumstellar material including a blue quasi-continuum and, uniquely, narrow oxygen emission lines that require high densities (∼10{sup 9} cm{sup –3}). From the observed spectra and LC, we estimate that the amount of material involved in the interaction was ∼3 M {sub ☉}. Our observations are in agreement with models of pulsational pair-instability SNe described in the literature.

  13. How to Detect the Signatures of Self-Gravitating Circumstellar Discs with the Atacama Large Millimetre/sub-millimetre Array

    CERN Document Server

    Dipierro, Giovanni; Testi, Leonardo; Monsalvo, Itziar de Gregorio

    2014-01-01

    In this paper we present simulated Atacama Large Millimetre/sub-millimetre Array (ALMA) observations of self-gravitating circumstellar discs with different properties in size, mass and inclination, located in four of the most extensively studied and surveyed star-forming regions. Starting from a Smoothed Particle Hydrodynamics (SPH) simulation and representative dust opacities, we have initially constructed maps of the expected emission at sub-mm wavelengths of a large sample of discs with different properties. We have then simulated realistic observations of discs as they may appear with ALMA using the Common Astronomy Software Application ALMA simulator. We find that, with a proper combination of antenna configuration and integration time, the spiral structure characteristic of self-gravitating discs is readily detectable by ALMA over a wide range of wavelengths at distances comparable to TW Hydrae ($\\sim 50 \\,$pc), Taurus - Auriga and Ophiucus ($\\sim 140 \\,$pc) star-forming regions. However, for discs loca...

  14. Carbon stars with oxygen-rich circumstellar dust shells Observational evidence for the onset of the carbon star phase

    Energy Technology Data Exchange (ETDEWEB)

    Willems, F.J.; De jong, T.

    1986-10-01

    Results from the IRAS Low Resolution Spectrograph (LRS) are presented which show that some carbon stars are surrounded by circumstellar shells containing oxygen-rich silicate-type dust rather than carbon-rich dust. This observation suggests that these stars have quite recently become carbon stars because they are still surrounded by the last remnant of the oxygen-rich M-type phase. It also suggests a direct transition from M-type to C-type rather than through an intermediate S phase. The transition takes place in about 100 years. Using a simple statistical argument, the typical duration of the carbon star phase is estimated to be from 1000 to 10,000 years. 37 references.

  15. OGLE-LMC-ECL-11893: The discovery of a long-period eclipsing binary with a circumstellar disk

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Subo [Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Road 5, Hai Dian District, Beijing 100871 (China); Katz, Boaz [Institute for Advanced Study, 1 Einstein Drive, Princeton, NJ 08544 (United States); Prieto, Jose L. [Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Peyton Hall, Princeton, NJ 08544 (United States); Udalski, Andrzej; Kozlowski, Szymon [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Street, R. A.; Tsapras, Y. [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, suite 102, Goleta, CA 93117 (United States); Bramich, D. M. [Qatar Environment and Energy Research Institute, Qatar Foundation, Tornado Tower, Floor 19, P.O. Box 5825, Doha (Qatar); Hundertmark, M.; Horne, K.; Dominik, M.; Jaimes, R. Figuera [SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS (United Kingdom); Snodgrass, C. [Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany)

    2014-06-10

    We report the serendipitous discovery of a disk-eclipse system OGLE-LMC-ECL-11893. The eclipse occurs with a period of 468 days, a duration of about 15 days, and a deep (up to Δm{sub I} ≈ 1.5), peculiar, and asymmetric profile. A possible origin of such an eclipse profile involves a circumstellar disk. The presence of the disk is confirmed by the H-α line profile from the follow-up spectroscopic observations, and the star is identified as Be/Ae type. Unlike the previously known disk-eclipse candidates, the eclipses of OGLE-LMC-ECL-11893 retain the same shape throughout the span of ∼17 yr (13 orbital periods), indicating no measurable orbital precession of the disk.

  16. Dynamics of the circumstellar gas in the Herbig Ae stars BF Orionis, SV Cephei, WW Vulpeculae and XY Persei

    CERN Document Server

    Mora, A; Natta, A; Grady, C A; De Winter, D; Davies, J K; Ferlet, R; Harris, A W; Miranda, L F; Montesinos, B; Oudmaijer, R D; Palacios, J; Quirrenbach, Andreas G; Rauer, H; Alberdi, A; Cameron, A; Deeg, H J; Garzón, F; Horne, K; Merin, B; Penny, A; Schneider, J; Solano, E; Tsapras, Y; Wesselius, P R

    2004-01-01

    We present high resolution (lambda / Delta_lambda = 49000) echelle spectra of the intermediate mass, pre-main sequence stars BF Ori, SV Cep, WW Wul and XY Per. The spectra cover the range 3800-5900 angstroms and monitor the stars on time scales of months and days. All spectra show a large number of Balmer and metallic lines with variable blueshifted and redshifted absorption features superimposed to the photospheric stellar spectra. Synthetic Kurucz models are used to estimate rotational velocities, effective temperatures and gravities of the stars. The best photospheric models are subtracted from each observed spectrum to determine the variable absorption features due to the circumstellar gas; those features are characterized in terms of their velocity, v, dispersion velocity, Delta v, and residual absorption, R_max. The absorption components detected in each spectrum can be grouped by their similar radial velocities and are interpreted as the signature of the dynamical evolution of gaseous clumps with, in m...

  17. Tracing Physical Conditions of the Circumstellar Medium in the Supernova Remnant G292.0+1.8

    Science.gov (United States)

    Wilcomb, Kielan; Ghavamian, Parviz; Hughes, John Patrick

    2016-06-01

    Recent X-ray and infrared studies of the oxygen-rich supernova remnant G292.0+1.8 have shown that it is likely interacting with the circumstellar wind from the massive progenitor star (≥20 Solar Masses). Some of this material lies in a moderately dense equatorial belt stretching across the middle of G292.0+1.8. Here we present analysis of ground based optical spectra of the equatorial belt. We use forbidden line diagnostics to probe the abundances, density and temperature in the belt, where non-radiative shocks are beginning to transition to the radiative stage. We interpret our results in conjunction with existing X-ray and infrared data to improve our understanding of how a supernova remnant interacts with the outermost part of its relic red giant wind.

  18. 40 CFR 1517.5 - Procedure for closing meetings.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Procedure for closing meetings. 1517.5 Section 1517.5 Protection of Environment COUNCIL ON ENVIRONMENTAL QUALITY PUBLIC MEETING PROCEDURES OF THE COUNCIL ON ENVIRONMENTAL QUALITY § 1517.5 Procedure for closing meetings. (a) A majority of the...

  19. 40 CFR 1517.7 - Records of closed meetings.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 32 2010-07-01 2010-07-01 false Records of closed meetings. 1517.7 Section 1517.7 Protection of Environment COUNCIL ON ENVIRONMENTAL QUALITY PUBLIC MEETING PROCEDURES OF THE COUNCIL ON ENVIRONMENTAL QUALITY § 1517.7 Records of closed meetings. (a) A record of each meeting...

  20. An alternative model for the origin of gaps in circumstellar disks

    CERN Document Server

    Vorobyov, Eduard I; Guedel, Manuel; Lin, D N C

    2016-01-01

    Motivated by recent observational and numerical studies suggesting that collapsing protostellar cores may be replenished from the local environment, we explore the evolution of protostellar cores submerged in the external counter-rotating environment. These models predict the formation of counter-rotating disks with a deep gap in the gas surface density separating the inner disk (corotating with the star) and the outer counter-rotating disk. The properties of these gaps are compared to those of planet-bearing gaps that form in disks hosting giant planets. We employ numerical hydrodynamics simulations of collapsing cores that are replenished from the local counter-rotating environment, as well as numerical hydrodynamic simulations of isolated disks hosting giant planets, to derive the properties of the gaps that form in both cases. Our numerical simulations demonstrate that counter-rotating disks can form for a wide range of mass and angular momentum available in the local environment. The gap that separates b...

  1. 电子商务环境下双渠道闭环供应链协调定价模型%Collaborative Pricing Model of Bi-channel Closed-loop Supply Chains in E-commerce Environment

    Institute of Scientific and Technical Information of China (English)

    马文波; 唐飞

    2014-01-01

    在电子商务环境下运用博弈理论研究了具有零售渠道和直销渠道的闭环供应链的定价与协调问题。分析和比较了分散决策与集中决策对双渠道闭环供应链节点企业定价决策和利润的影响,发现分散决策将导致一定的效率损失。为弥补这种效率损失,设计了一个两部收费制契约,以实现双渠道闭环供应链的协调。%In this paper, we studied the pricing and collaboration problem of the closed-loop supply chains with retailing and direct-sales channels using the game theory, compared the influence of the distributive decision-making mode and the centralized mode on the price and profit of the nodal enterprises of the supply chain and at the end, designed accordingly a two-part charging contract to coordinate the supply chain.

  2. 40 CFR 63.983 - Closed vent systems.

    Science.gov (United States)

    2010-07-01

    ... inspections for visible, audible, or olfactory indications of leaks. (ii) If the closed vent system is... 40 Protection of Environment 10 2010-07-01 2010-07-01 false Closed vent systems. 63.983 Section 63... Emission Standards for Closed Vent Systems, Control Devices, Recovery Devices and Routing to a Fuel...

  3. Closed Loop Subspace Identification

    Directory of Open Access Journals (Sweden)

    Geir W. Nilsen

    2005-07-01

    Full Text Available A new three step closed loop subspace identifications algorithm based on an already existing algorithm and the Kalman filter properties is presented. The Kalman filter contains noise free states which implies that the states and innovation are uneorre lated. The idea is that a Kalman filter found by a good subspace identification algorithm will give an output which is sufficiently uncorrelated with the noise on the output of the actual process. Using feedback from the output of the estimated Kalman filter in the closed loop system a subspace identification algorithm can be used to estimate an unbiased model.

  4. Far-infrared and sub-millimetre surveys of circumstellar discs

    Science.gov (United States)

    Phillips, N. M.

    2011-06-01

    near-infrared photometry. Debris discs were detected around 46 systems, 12 of which - including the system with the largest dust mass - are new discoveries. This survey adds to the results of previous studies which show that debris disc incidence is not correlated with host star metallicity, despite the well known giant planet - metallicity correlation. This is in accordance with what is predicted from the core accretion theory of planet formation. The most significant result from this survey is that, contrary to results reported in a previous work, debris discs are overall less common around binary stars. Further investigation shows that systems with separations of ˜3-150 AU are especially deficient of debris, whilst closer binaries and the primaries of wider binaries show debris detection rates consistent with those for single stars. A sample of circumstellar discs around 29 young stellar systems with ages of 5-30 Myr were observed with the LABOCA sub-millimetre instrument on the APEX telescope at 870 μm, to provide disc masses or mass upper limits in support of a large Herschel programme. These targets included the η Chamaeleontis cluster and four bright Herbig Ae/Be stars which have not previously been observed at this wavelength. All but the Herbig Ae/Be stars were not detected, and 3σ dust mass upper limits of ˜0.1-3M_⊙ are determined, with corresponding total disc masses of ˜0.03-1M_{Jup}. These mass limits indicate that there is insufficient remaining material in these discs to form gas giant planets, and add to the prevailing view that protoplanetary discs typically disperse within 10 Myr and that gas giant planet formation must be completed before this time. A search for cold dust emission from two of the Solar System's nearest neighbours - α Centauri AB and ɛ Indi - was also performed with LABOCA. In both cases no debris disc emission was detected. A bright resolved feature was detected near α Centauri AB, however, follow-up observations at a

  5. Pd Close Coupled Catalyst

    Institute of Scientific and Technical Information of China (English)

    Zhong Hua SHI; Mao Chu GONG; Yao Qiang CHEN

    2006-01-01

    A catalyst comprised novel high surface area alumina support was prepared to control emission of automobiles. The results showed that prepared catalyst could satisfy the requirements of a high performance close coupled catalyst for its good catalytic activity at low temperature and good stability at high temperature.

  6. AGN environments: is the viewing angle sufficient to explain the difference between broad-line and narrow-line AGN? -- A low-redshift study of close AGN neighbours. Paper I

    CERN Document Server

    Villarroel, Beatriz; Matsuoka, Yoshiki

    2012-01-01

    The unification of active galactic nuclei (AGN) is a model that has been difficult to test due to the lack of knowledge on the intrinsic luminosities of the objects. We present a test were we probe the model by statistical investigation of the neighbours to AGN at redshifts 0.03 < z < 0.2 within a projected distance of 350 kpc and |\\Delta z|<0.001, 0.006, 0.012 and 0.03 between AGN and neighbour. 1658 Type-1 (broad-line) AGN-galaxy pairs and 5698 Type-2 AGN-galaxy pairs with spectroscopic redshifts from the Data Release 7 of Sloan Digital Sky Survey were used together with a complementary set of pairs with photometric redshifts on the neighbour galaxies (13519 Type-1 AGN-galaxy and 58743 Type-2 AGN-galaxy pairs). Morphologies for the AGN host galaxies were derived from the Galaxy Zoo project. Our results suggest that broad-line AGN and narrow-line AGN reside in widely different environments where the neighbours to Type-2 AGN are more star-forming and bluer than those of Type-1 AGN. There is a colour-...

  7. On closed weak supplemented modules

    Institute of Scientific and Technical Information of China (English)

    ZENG Qing-yi; SHI Mei-hua

    2006-01-01

    A module M is called closed weak supplemented if for any closed submodule N of M, there is a submodule K of M such that M=K+N and K(c)N<<M. Any direct summand of closed weak supplemented module is also closed weak supplemented.Any nonsingular image of closed weak supplemented module is closed weak supplemented. Nonsingular V-rings in which all nonsingular modules are closed weak supplemented are characterized in Section 4.

  8. Gamma-Ray Bursts in Circumstellar Shells: A Possible Explanation for Flares

    CERN Document Server

    Mesler, Robert A; Lloyd-Ronning, Nicole M; Fryer, Chris L; Pihlström, Ylva M

    2012-01-01

    It is now generally accepted that long-duration gamma-ray bursts (GRBs) are due to the collapse of massive rotating stars. The precise collapse process itself, however, is not yet fully understood. Strong winds, outbursts, and intense ionizing UV radiation from single stars or strongly interacting binaries are expected to destroy the molecular cloud cores that give birth to them and create highly complex circumburst environments for the explosion. Such environments might imprint features on GRB light curves that uniquely identify the nature of the progenitor and its collapse. We have performed numerical simulations of realistic environments for a variety of long-duration GRB progenitors with ZEUS-MP and have developed an analytical method for calculating detailed GRB light curves in these profiles. We find that, in the context of the standard afterglow model, massive shells around GRBs produce strong signatures in their light curves, and that this clearly distinguishes them from those occurring in uniform med...

  9. Thermal Interaction of Closely Spaced Persons

    DEFF Research Database (Denmark)

    Brohus, Henrik; Nielsen, Peter V.; Tøgersen, Michael

    2011-01-01

    This paper presents results from a pilot study on the thermal interaction of closely spaced persons in a large enclosure. The surface temperature at different densities of persons is evaluated using a high resolution thermo vision camera in a controlled thermal environment. The corresponding ther...

  10. El entrenador de alto nivel en triatlón: entorno próximo y cualidades fundamentales para el rendimiento. (High level triathlon coach: close environment and basic performance qualities.

    Directory of Open Access Journals (Sweden)

    Germán Ruiz Tendero

    2011-05-01

    Full Text Available ResumenLa figura del entrenador de alto nivel (E.A.N. en triatlón y su entorno apenas ha sido estudiada, y sin embargo puede estar ejerciendo una gran influencia sobre el microsistema deportivo. Estudiar este microsistema es el objetivo del presente estudio en función de los siguientes factores: interacción con sus deportistas, objetivos deportivos, grado de satisfacción con diferentes agentes del entorno (triatletas, otros entrenadores, federaciones y club, ámbito laboral, nivel académico y entorno familiar. Además, se pretende conocer qué cualidades atribuibles a un buen entrenador de alto nivel en triatlón son las mejores valoradas por los propios entrenadores. En este estudio participan 14 entrenadores españoles de alto nivel en activo (uno menos que el universo de la muestra objeto. Todos ellos hombres (edad media= 37,43 años ±7,27. El diseño de investigación descriptivo-cuantitativo utiliza el cuestionario como instrumento. El cuestionario fue pasado en periodo no competitivo por el mismo investigador mediante entrevistas personales mayoritariamente, o de forma telemática en su defecto. Los resultados muestran que el triatlón de alto nivel español se rige por un sistema centralizado en centros de rendimiento. La presencia del entrenador en las competiciones (sólo uno acudía a todas no supone un factor determinante del rendimiento. El ratio número de atletas de alto nivel por entrenador es de 3,71(+3,04 y el ratio total contando con otros triatletas de diferente nivel es de 8 (±4,78, adecuado para las condiciones actuales pero mejorable en el alto nivel. El nivel académico de los E.A.N. es muy bueno y específico a su labor deportiva. La cualidad confianza para el diálogo personal (4,69 sobre 5 resulta ser la más valorada por parte de los propios entrenadores, anteponiendo el plano personal al deportivo.AbstractNot much attention has been paid to the high level coach (H.L.C. in triathlon and his environment; however

  11. Palomar/triplespec observations of Spitzer/MIPSGAL 24 μm circumstellar shells: Unveiling the natures of their central sources

    Energy Technology Data Exchange (ETDEWEB)

    Flagey, N. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Noriega-Crespo, A. [Infrared Processing and Analysis Center, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Petric, A. [California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Geballe, T. R., E-mail: nflagey@jpl.nasa.gov [Gemini North Observatory, 670 North A' ohoku Place, Hilo, HI 96720 (United States)

    2014-08-01

    We present near-IR spectroscopic observations of the central sources in 17 circumstellar shells from a sample of more than 400 'bubbles' discovered in the Spitzer/MIPSGAL 24 μm survey of the Galactic plane and in the Cygnus-X region. To identify the natures of these shells, we have obtained J, H, and K band spectra with a resolution of ∼2600 of the stars at their centers. We observed 14 MIPSGAL bubbles (MBs), WR149, and 2 objects in the Cygnus-X region (WR138a and BD+43 3710), our sample being about 2.5 mag fainter in the K band than previous studies of the central sources of MBs. We use spectroscopic diagnostics and spectral libraries of late- and early-type stars to constrain the natures of our targets. We find five late-type giants. The equivalent widths of their CO 2.29 μm features allow us to determine the spectral types of the stars and hence derive the extinction along the line of sight, distance, and physical size of the shells. We also find 12 early-type stars: in 9 MBs and the 3 comparison objects. We find that the subtype inferred from the near-IR for WR138a (WN9h) and WR149 (WN5h) agrees with that derived from optical observations. A careful analysis of the literature and the environment of BD+43 3710 allows us to rule out the carbon star interpretation previously suggested. Our near-IR spectrum suggests that it is a B5 supergiant. At the centers of the nine MBs, we find a WC5-6 star possibly of low mass, a candidate O5-6 V star, a B0 supergiant, a B/A-type giant, and five luminous blue variable (LBV) candidates. We also report the detections of emission lines arising from at least two shells with typical extents (∼10''), in agreement with those in the mid-IR. We summarize the findings on the natures of the MBs since their discovery, with 30% of them now known. Most MBs with central sources detected in the near- to mid-IR have been identified and are red and blue giants, supergiants, or stars evolving toward these phases

  12. Closing global material loops

    DEFF Research Database (Denmark)

    Prosman, Ernst-Jan; Wæhrens, Brian Vejrum; Liotta, Giacomo

    2017-01-01

    Replacing virgin materials with waste materials, a practice known as Industrial Symbiosis (IS), has been identified as a key strategy for closing material loops. This article adopts a critical view on geographic proximity and external coordinators – two key enablers of IS. By ‘uncovering’ a case...... where both enablers are absent, this study seeks to explore firm-level challenges of IS. We adopt an exploratory case study approach at a cement manufacturer who engages in cross-border IS without the support of external coordinators. Our research presents insights into two key areas of IS: 1) setting...... for geographic proximity and external coordinators. In doing so, our insights into firm-level challenges of long-distance IS exchanges contribute to closing global material loops by increasing the number of potential circular pathways....

  13. GAMMA-RAY BURSTS IN CIRCUMSTELLAR SHELLS: A POSSIBLE EXPLANATION FOR FLARES

    Energy Technology Data Exchange (ETDEWEB)

    Mesler, Robert A.; Pihlstroem, Ylva M. [Department of Physics and Astronomy, University of New Mexico, MSC07 4220, Albuquerque, NM 87131 (United States); Whalen, Daniel J. [MS B227, T-2 Los Alamos National Laboratory, Los Alamos NM, 87545 (United States); Lloyd-Ronning, Nicole M.; Fryer, Chris L., E-mail: meslerra@unm.edu [MS-B227, T-6 Los Alamos National Laboratory, Los Alamos NM, 87545 (United States)

    2012-10-01

    It is now generally accepted that long-duration gamma-ray bursts (GRBs) are due to the collapse of massive rotating stars. The precise collapse process itself, however, is not yet fully understood. Strong winds, outbursts, and intense ionizing UV radiation from single stars or strongly interacting binaries are expected to destroy the molecular cloud cores that give birth to them and create highly complex circumburst environments for the explosion. Such environments might imprint features on GRB light curves that uniquely identify the nature of the progenitor and its collapse. We have performed numerical simulations of realistic environments for a variety of long-duration GRB progenitors with ZEUS-MP and have developed an analytical method for calculating GRB light curves in these profiles. Though a full, three-dimensional, relativistic magnetohydrodynamical computational model is required to precisely describe the light curve from a GRB in complex environments, our method can provide a qualitative understanding of these phenomena. We find that, in the context of the standard afterglow model, massive shells around GRBs produce strong signatures in their light curves, and that this can distinguish them from those occurring in uniform media or steady winds. These features can constrain the mass of the shell and the properties of the wind before and after the ejection. Moreover, the interaction of the GRB with the circumburst shell is seen to produce features that are consistent with observed X-ray flares that are often attributed to delayed energy injection by the central engine. Our algorithm for computing light curves is also applicable to GRBs in a variety of environments such as those in high-redshift cosmological halos or protogalaxies, both of which will soon be targets of future surveys such as the Joint Astrophysics Nascent Satellite or Lobster.

  14. Close partner relationships

    Directory of Open Access Journals (Sweden)

    Stefanović-Stanojević Tatjana Z.

    2002-01-01

    Full Text Available According to the theory of emotional attachment, specific emotional relationships are being established at an early age between a child and its parents. On the basis of the quality of these relationships the child creates the so-called internal working model ie the image of itself as well as others. The working model persists throughout one's lifetime, shaping in part the quality of adult relationships. Thus, a dominant adult relationship is a close, partner or love one. Within the indicated theoretical context, we were interested in finding out whether there is a statistically significant link between the emotional ties of parents and their children formed in early childhood. The investigation included 180 grown-ups of the same sex and age. For investigating close partner relationships the test Experience in Close Relationship by the American authors (Brenan K.A., Clark C.L., & Shaver P.R. 1998. was used, while the early emotional relationships were investigated using a test which has been the only one so far to measure this quality in adults - Adult Attachment Interview, (Main M., Casidy J., & Kaplan N., 1985. The results show there is a statistically significant link between the observed variables.

  15. The circumstellar envelope around the S-type AGB star W Aql. Effects of an eccentric binary orbit

    Science.gov (United States)

    Ramstedt, S.; Mohamed, S.; Vlemmings, W. H. T.; Danilovich, T.; Brunner, M.; De Beck, E.; Humphreys, E. M. L.; Lindqvist, M.; Maercker, M.; Olofsson, H.; Kerschbaum, F.; Quintana-Lacaci, G.

    2017-09-01

    Context. Recent observations at subarcsecond resolution, now possible also at submillimeter wavelengths, have shown intricate circumstellar structures around asymptotic giant branch (AGB) stars, mostly attributed to binary interaction. The results presented here are part of a larger project aimed at investigating the effects of a binary companion on the morphology of circumstellar envelopes (CSEs) of AGB stars. Aims: AGB stars are characterized by intense stellar winds that build CSEs around the stars. Here, the CO(J = 3 → 2) emission from the CSE of the binary S-type AGB star W Aql has been observed at subarcsecond resolution using ALMA. The aim of this paper is to investigate the wind properties of the AGB star and to analyse how the known companion has shaped the CSE. Methods: The average mass-loss rate during the creation of the detected CSE is estimated through modelling, using the ALMA brightness distribution and previously published single-dish measurements as observational constraints. The ALMA observations are presented and compared to the results from a 3D smoothed particle hydrodynamics (SPH) binary interaction model with the same properties as the W Aql system and with two different orbital eccentricities. Three-dimensional radiative transfer modelling is performed and the response of the interferometer is modelled and discussed. Results: The estimated average mass-loss rate of W Aql is Ṁ = 3.0 × 10-6M⊙ yr-1 and agrees with previous results based on single-dish CO line emission observations. The size of the emitting region is consistent with photodissociation models. The inner 10'' of the CSE is asymmetric with arc-like structures at separations of 2-3'' scattered across the denser sections. Further out, weaker spiral structures at greater separations are found, but this is at the limit of the sensitivity and field of view of the ALMA observations. Conclusions: The CO(J = 3 → 2) emission is dominated by a smooth component overlayed with two

  16. The circumstellar shell of the post-ABB star HD 56126: the 12C12C/12C13C isotope ratio and12C16O column density

    NARCIS (Netherlands)

    Barker, E.J.; Lambert, D.L.

    1998-01-01

    We have made the first detection of circumstellar absorption lines of the 12C13C A 1Πu-X 1∑g+ (Phillips) system 1-0 band and the 12C16O X 1∑+ first-overtone 2-0 band in the spectrum of the post-AGB star HD 56126 (IRAS 07134+1005). All current detections of circumstellar molecular absorption lines to

  17. Molecular anions in circumstellar envelopes, interstellar clouds and planetary atmospheres: quantum dynamics of formation and evolution

    CERN Document Server

    Carelli, Fabio

    2012-01-01

    For decades astronomers and astrophysicists believed that only positively charged ions were worthy of relevance in drawing the networks for possible chemical reactions in the interstellar medium, as well as in modeling the physical conditions in most of astrophysical environments. Thus, molecular negative ions received minor attention until their possible existence was observationally confirmed (discovery of the first interstellar anion, C6H-), about thirty years after the first physically reasonable proposal on their actual detection was theoretically surmised by E.Herbst. In an astrophysical context, their role should be then found in their involvement in the charge balance as well as in the chemical evolution of the considered environment: depending on their amount and on the global gas density, in fact, the possible evolutive scenario could be susceptible of marked variations on the estimated time needed for reaching the steady state, their presence having thus also important repercussions on the final ch...

  18. Molecular anions in circumstellar envelopes, interstellar clouds and planetary atmospheres: quantum dynamics of formation and evolution

    OpenAIRE

    Carelli, Fabio

    2011-01-01

    Nowadays, it is a well known fact that most of the matter in our Solar System, in our Galaxy and, probably, within the whole Universe, exists in the form of ionized particles. For decades astronomers and astrophysicists believed that only positively charged ions were worthy of relevance in drawing the networks for possible chemical reactions in the interstellar medium, as well as in modeling the physical conditions in most of astrophysical environments. Thus, negative ions (and especially mol...

  19. THE CIRCUMSTELLAR DISK OF THE Be STAR o AQUARII AS CONSTRAINED BY SIMULTANEOUS SPECTROSCOPY AND OPTICAL INTERFEROMETRY

    Energy Technology Data Exchange (ETDEWEB)

    Sigut, T. A. A. [Department of Physics and Astronomy, The University of Western Ontario, London, Ontario, N6A 3K7 (Canada); Tycner, C.; Jansen, B. [Department of Physics, Central Michigan University, Mount Pleasant, MI 48859 (United States); Zavala, R. T. [US Naval Observatory, Flagstaff Station, 10391 W. Naval Observatory Rd, Flagstaff, AZ 86001 (United States)

    2015-12-01

    Omicron Aquarii is a late-type, Be shell star with a stable and nearly symmetric Hα emission line. We combine Hα interferometric observations obtained with the Navy Precision Optical Interferometer covering 2007 through 2014 with Hα spectroscopic observations over the same period and a 2008 observation of the system's near-infrared spectral energy distribution to constrain the properties of o Aqr's circumstellar disk. All observations are consistent with a circumstellar disk seen at an inclination of 75° ±  3° with a position angle on the sky of 110° ±  8° measured East from North. From the best-fit disk density model, we find that 90% of the Hα emission arises from within 9.5 stellar radii, and the mass associated with this Hα disk is ∼1.8 × 10{sup −10} of the stellar mass, and that the associated angular momentum, assuming Keplerian rotation for the disk, is ∼1.6 × 10{sup −8} of the total stellar angular momentum. The occurrence of a central quasi-emission feature in Mg ii λ4481 is also predicted by this best-fit disk model and the computed profile compares successfully with observations from 1999. To obtain consistency between the Hα line profile modeling and the other constraints, it was necessary in the profile fitting to weight the line core (emission peaks and central depression) more heavily than the line wings, which were not well reproduced by our models. This may reflect the limitation of assuming a single power law for the disk's variation in equatorial density. The best-fit disk density model for o Aqr predicts that Hα is near its maximum strength as a function of disk density, and hence the Hα equivalent width and line profile change only weakly in response to large (factor of ∼5) changes in the disk density. This may in part explain the remarkable observed stability of o Aqr's Hα emission line profile.

  20. Rings from Close Encounters

    Science.gov (United States)

    Kohler, Susanna

    2016-09-01

    Weve recently discovered narrow sets of rings around two minor planets orbiting in our solar system. How did these rings form? A new study shows that they could be a result of close encounters between the minor planets and giants like Jupiter or Neptune.Unexpected Ring SystemsPositions of the centaurs in our solar system (green). Giant planets (red), Jupiter trojans (grey), scattered disk objects (tan) and Kuiper belt objects (blue) are also shown. [WilyD]Centaurs are minor planets in our solar system that orbit between Jupiter and Neptune. These bodies of which there are roughly 44,000 with diameters larger than 1 km have dynamically unstable orbits that cross paths with those of one or more giant planets.Recent occultation observations of two centaurs, 10199 Chariklo and 2060 Chiron, revealed that these bodies both host narrow ring systems. Besides our four giant planets, Chariklo and Chiron are the only other bodies in the solar system known to have rings. But how did these rings form?Scientists have proposed several models, implicating collisions, disruption of a primordial satellite, or dusty outgassing. But a team of scientists led by Ryuki Hyodo (Paris Institute of Earth Physics, Kobe University) has recently proposed an alternative scenario: what if the rings were formed from partial disruption of the centaur itself, after it crossed just a little too close to a giant planet?Tidal Forces from a GiantHyodo and collaborators first used past studies of centaur orbits to estimate that roughly 10% of centaurs experience close encounters (passing within a distance of ~2x the planetary radius) with a giant planet during their million-year lifetime. The team then performed a series of simulations of close encounters between a giant planet and a differentiated centaur a body in which the rocky material has sunk to form a dense silicate core, surrounded by an icy mantle.Some snapshots of simulation outcomes (click for a closer look!) for different initial states of

  1. Mapping the 12CO J = 1-0 and J = 2-1 emission in AGB and early post-AGB circumstellar envelopes. I. The COSAS program, first sample

    Science.gov (United States)

    Castro-Carrizo, A.; Quintana-Lacaci, G.; Neri, R.; Bujarrabal, V.; Schöier, F. L.; Winters, J. M.; Olofsson, H.; Lindqvist, M.; Alcolea, J.; Lucas, R.; Grewing, M.

    2010-11-01

    We present COSAS (CO Survey of late AGB Stars), a project to map and analyze the 12CO J = 1-0 and J = 2-1 line emission in a representative sample of circumstellar envelopes around AGB and post-AGB stars. The survey was undertaken with the aim of investigating small- and large-scale morphological and kinematical properties of the molecular environment surrounding stars in the late AGB and early post-AGB phases. For this, COSAS combines the high sensitivity and spatial resolving power of the IRAM Plateau de Bure interferometer with the better capability of the IRAM 30 m telescope to map extended emission. The global sample encompasses 45 stars selected to span a range in chemical type, variability type, evolutionary state, and initial mass. COSAS provides means to quantify variations in the mass-loss rates, assess morphological and kinematical features, and to investigate the appearance of fast aspherical winds in the early post-AGB phase. This paper, which is the first of a series of COSAS papers, presents the results from the analyses of a first sample of 16 selected sources. The envelopes around late AGB stars are found to be mostly spherical, often mingled with features such as concentric arcs (R Cas and TX Cam), a broken spiral density pattern (TX Cam), molecular patches testifying to aspherical mass-loss (WX Psc, IK Tau, V Cyg, and S Cep), and also with well-defined axisymmetric morphologies and kinematical patterns (X Her and RX Boo). The sources span a wide range of angular sizes, from relatively compact (CRL 2362, OH 104.9+2.4 and CRL 2477) to very large (χ Cyg and TX Cam) envelopes, sometimes partially obscured by self-absorption features, which particularly for IK Tau and χ Cyg testifies to the emergence of aspherical winds in the innermost circumstellar regions. Strong axial structures with more or less complex morphologies are detected in four early post-AGB stars (IRAS 20028+3910, IRAS 23321+6545, IRAS 19475+3119 and IRAS 21282+5050) of the sub

  2. Closed lung trauma.

    Science.gov (United States)

    Feden, Jeffrey P

    2013-04-01

    Pulmonary injuries from blunt thoracic trauma are seen regularly with high-energy mechanisms but described less frequently in association with sports. Pneumothorax, hemothorax, pneumomediastinum, and pulmonary contusion are uncommon with athletic participation and often follow a benign clinical course. Life-threatening complications may arise, and athletes with chest trauma deserve close attention. Appropriate diagnosis is suggested by history and physical examination; conventional chest radiography is preferred as the initial imaging study but has limitations. Use of CT for trauma has improved diagnostic sensitivity for occult injury, although this may not alter management or outcomes. Return to play is guided by resolution of symptoms and radiographic findings.

  3. Can X-rays clear a circumstellar disk in 2 years?

    Science.gov (United States)

    Guenther, Hans

    2013-09-01

    Young stars are born surrounded by primordial disks. Eventually, these proto-planetary disks vanish. Some systems later form a debris disk with small dust grains. Up until May 2008 our target TYC 8241 2652 1 showed strong IR emission from such a disk. Between 2008 and 2010 the IR emission dropped by two orders of magnitude, which means that the dust mass in the inner disk decreased by 90-99%. The cause is unknown, but several hypotheses require high X-ray activity. We propose to observe this target for 10 ks with ACIS-S. This pointing will verify the association of a close-by ROSAT and XMM-Newton slew survey source with TYC 8241 2652 1, confirm the X-ray flux and look for signatures of high X-ray activity such as high plasma temperatures and Ne/Fe abundance ratios.

  4. Flash Spectroscopy: Emission Lines from the Ionized Circumstellar Material around $<10$-Day-Old Type II Supernovae

    CERN Document Server

    Khazov, D; Gal-Yam, A; Manulis, I; Rubin, A; Kulkarni, S R; Arcavi, I; Kasliwal, M M; Ofek, E O; Cao, Y; Perley, D; Sollerman, J; Horesh, A; Sullivan, M; Filippenko, A V; Nugent, P E; Howell, D A; Cenko, S B; Silverman, J M; Ebeling, H; Taddia, F; Johansson, J; Laher, R R; Surace, J; Rebbapragada, U D; Wozniak, P R; Matheson, T

    2015-01-01

    Supernovae (SNe) embedded in dense circumstellar material (CSM) may show prominent emission lines in their early-time spectra ($\\leq 10$ days after the explosion), owing to recombination of the CSM ionized by the shock-breakout flash. From such spectra ("flash spectroscopy"), we can measure various physical properties of the CSM, as well as the mass-loss rate of the progenitor during the year prior to its explosion. Searching through the Palomar Transient Factory (PTF and iPTF) SN spectroscopy databases from 2009 through 2014, we found 12 Type II SNe showing flash-ionized (FI) signatures in their first spectra. All are younger than 10 days. These events constitute 14\\% of all 84 SNe in our sample having a spectrum within 10 days from explosion, and 18\\% of SNe~II observed at ages $<5$ days, thereby setting lower limits on the fraction of FI events. We classified as "blue/featureless" (BF) those events having a first spectrum which is similar to that of a black body, without any emission or absorption signa...

  5. The First Circumstellar Disk Imaged in Silhouette with Adaptive Optics: MagAO Imaging of Orion 218-354

    CERN Document Server

    Follette, Katherine B; Males, Jared R; Kopon, Derek; Wu, Ya-Lin; Morzinski, Katie M; Hinz, Philip; Rodigas, Timothy J; Puglisi, Alfio; Esposito, Simone; Riccardi, Armando; Pinna, Enrico; Xompero, Marco; Briguglio, Runa

    2013-01-01

    We present high resolution adaptive optics (AO) corrected images of the silhouette disk Orion 218-354 taken with Magellan AO (MagAO) and its visible light camera, VisAO, in simultaneous differential imaging (SDI) mode at H-alpha. This is the first image of a circumstellar disk seen in silhouette with adaptive optics and is among the first visible light adaptive optics results in the literature. We derive the disk extent, geometry, intensity and extinction profiles and find, in contrast with previous work, that the disk is likely optically-thin at H-alpha. Our data provide an estimate of the column density in primitive, ISM-like grains as a function of radius in the disk. We estimate that only ~10% of the total sub-mm derived disk mass lies in primitive, unprocessed grains. We use our data, Monte Carlo radiative transfer modeling and previous results from the literature to make the first self-consistent multiwavelength model of Orion 218-354. We find that we are able to reproduce the 1-1000micron SED with a ~2...

  6. The young low-mass star ISO-Oph-50: Extreme variability induced by a clumpy, evolving circumstellar disk

    CERN Document Server

    Scholz, Aleks; Geers, Vincent

    2015-01-01

    ISO-Oph-50 is a young low-mass object in the ~Myr old Ophiuchus star forming region undergoing dramatic changes in its optical/near/mid-infrared brightness by 2-4 mag. We present new multi-band photometry and near-infrared spectra, combined with a synopsis of the existing literature data. Based on the spectroscopy, the source is confirmed as a mid M dwarf, with evidence for ongoing accretion. The near-infrared lightcurves show large-scale variations, with 2-4 mag amplitude in the bands IJHK, with the object generally being bluer when faint. Near its brightest state, the object shows colour changes consistent with variable extinction of dAV~7 mag. High-cadence monitoring at 3.6mu reveals quasi-periodic variations with a typical timescale of 1-2 weeks. The best explanation for these characteristics is a low-mass star seen through circumstellar matter, whose complex variability is caused by changing inhomogeneities in the inner parts of the disk. When faint, the direct stellar emission is blocked; the near-infra...

  7. Studies of circumstellar shells in AGB stars by multifrequency (sub)mm-VLBI observations of maser emission

    Science.gov (United States)

    Colomer, F.; Desmurs, J. F.; Bujarrabal, V.; Baudry, A.; de Vicente, P.; Soria-Ruiz, R.; Alcolea, J.; Diaz-Pulido, A.; Gómez, M.

    2017-03-01

    VLBI observations of maser emission are a basic tool to study the circumstellar envelopes (CSEs) around evolved stars, mainly around AGB and post-AGB stars. The maser lines of water and silicon monoxide are particularly intense. They provide us with high spatial resolution data on the very inner CSEs around AGB stars, including the pulsating layers previous to grain formation and outer regions where the fast expansion characteristic of such envelopes is already present. The analysis of the pumping mechanism of SiO masers and of the physical conditions in the emitting clumps requires accurate maps of the various lines, which show different excitation requirements. A large observational effort is being done to obtain (quasi-)simultaneous multiline data at the highest spatial resolution, using VLBI techniques, which makes possible to compare the relative distribution of the maser lines. We present the state-of-the-art in the field, and discuss preliminary results of SiO masers observed with the Global Millimeter VLBI Array (GMVA) which provide a new view into the physics of these AGB envelopes. The participation of ALMA in these VLBI arrays will boost the study of these masers, at higher frequencies.

  8. Search for Early Gamma-ray Production in Supernovae Located in a Dense Circumstellar Medium with the Fermi LAT

    CERN Document Server

    ,

    2015-01-01

    Supernovae (SNe) exploding in a dense circumstellar medium (CSM) are hypothesized to accelerate cosmic rays in collisionless shocks and emit GeV gamma rays and TeV neutrinos on a time scale of several months. We perform the first systematic search for gamma-ray emission in Fermi LAT data in the energy range from 100 MeV to 300 GeV from the ensemble of 147 SNe Type IIn exploding in dense CSM. We search for a gamma-ray excess at each SNe location in a one year time window. In order to enhance a possible weak signal, we simultaneously study the closest and optically brightest sources of our sample in a joint-likelihood analysis in three different time windows (1 year, 6 months and 3 months). For the most promising source of the sample, SN 2010jl (PTF10aaxf), we repeat the analysis with an extended time window lasting 4.5 years. We do not find a significant excess in gamma rays for any individual source nor for the combined sources and provide model-independent flux upper limits for both cases. In addition, we de...

  9. FIRST SCIENCE OBSERVATIONS WITH SOFIA/FORCAST: PROPERTIES OF INTERMEDIATE-LUMINOSITY PROTOSTARS AND CIRCUMSTELLAR DISKS IN OMC-2

    Energy Technology Data Exchange (ETDEWEB)

    Adams, Joseph D.; Herter, Terry L.; Gull, George E.; Henderson, Charles P.; Schoenwald, Justin; Stacey, Gordon [Department of Astronomy, Cornell University, Space Sciences Bldg., Ithaca, NY 14853 (United States); Osorio, Mayra; Macias, Enrique [Instituto de Astrofisica de Andalucia, CSIC, Camino Bajo de Huetor 50, E-18008 Granada (Spain); Thomas Megeath, S.; Fischer, William J. [Department of Physics and Astronomy, University of Toledo, Mailstop 111, 2801 West Bancroft Street, Toledo, OH 43606 (United States); Ali, Babar [NHSC/IPAC/Caltech, 770 South Wilson Avenue, Pasadena, CA 91125 (United States); Calvet, Nuria [Department of Astronomy, University of Michigan, 825 Dennison Building, 500 Church St, Ann Arbor, MI 48109 (United States); D' Alessio, Paola [Centro de Radioastronomia y Astrofisica, Universidad Nacional Autonoma de Mexico, 58089 Morelia, Michoacan (Mexico); De Buizer, James M.; Shuping, Ralph Y. [SOFIA-University Space Research Association, NASA Ames Research Center, Mail Stop N211-3, Moffett Field, CA 94035 (United States); Keller, Luke D. [Ithaca College, Physics Department, 264 Ctr for Natural Sciences, Ithaca, NY 14850 (United States); Morris, Mark R. [Department of Physics and Astronomy, University of California, Los Angeles, 405 Hilgard Ave., Los Angeles, CA 90095-1547 (United States); Remming, Ian S. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Stanke, Thomas [ESO, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Muenchen (Germany); Stutz, Amelia [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); and others

    2012-04-20

    We examine eight young stellar objects in the OMC-2 star-forming region based on observations from the SOFIA/FORCAST early science phase, the Spitzer Space Telescope, the Herschel Space Observatory, Two Micron All Sky Survey, Atacama Pathfinder Experiment, and other results in the literature. We show the spectral energy distributions (SED) of these objects from near-infrared to millimeter wavelengths, and compare the SEDs with those of sheet collapse models of protostars and circumstellar disks. Four of the objects can be modeled as protostars with infalling envelopes, two as young stars surrounded by disks, and the remaining two objects have double-peaked SEDs. We model the double-peaked sources as binaries containing a young star with a disk and a protostar. The six most luminous sources are found in a dense group within a 0.15 Multiplication-Sign 0.25 pc region; these sources have luminosities ranging from 300 L{sub Sun} to 20 L{sub Sun }. The most embedded source (OMC-2 FIR 4) can be fit by a class 0 protostar model having a luminosity of {approx}50 L{sub Sun} and mass infall rate of {approx}10{sup -4} M{sub Sun} yr{sup -1}.

  10. Revealing the inner circumstellar disk of the T Tauri star S CrA N using the VLTI

    CERN Document Server

    Vural, J; Kraus, S; Weigelt, G; Driebe, T; Benisty, M; Dugué, M; Massi, F; Monin, J -L; Vannier, M

    2012-01-01

    Aims: We investigate the structure of the circumstellar disk of the T Tauri star S CrA N and test whether the observations agree with the standard picture proposed for Herbig Ae stars. Methods: Our observations were carried out with the VLTI/AMBER instrument in the H and K bands with the low spectral resolution mode. For the interpretation of our near-infrared AMBER and archival mid-infrared MIDI visibilities, we employed both geometric and temperature-gradient models. Results: To characterize the disk size, we first fitted geometric models consisting of a stellar point source, a ring-shaped disk, and a halo structure to the visibilities. In the H and K bands, we measured ring-fit radii of 0.73 +- 0.03 mas (corresponding to 0.095 +- 0.018 AU for a distance of 130 pc) and 0.85 +- 0.07 mas (0.111 +- 0.026 AU), respectively. This K-band radius is approximately two times larger than the dust sublimation radius of ~0.05 AU expected for a dust sublimation temperature of 1500 K and gray dust opacities, but approxima...

  11. Detection of a large Be circumstellar disk during X-ray quiescence of XTE J1946+274

    CERN Document Server

    Arabaci, M Ozbey; Gutierrez-Soto, J; Zurita, C; Nespoli, E; Suso, J; Kiaeerad, F; Garcia-Rojas, J; Kiziloglu, U

    2014-01-01

    We present a multiwavelength study of the Be/X-ray binary system XTE J1946+274 with the main goal of better characterizing its behavior during X-ray quiescence. We aim to shed light on the mechanism which triggers the X-ray activity for this source. XTE J1946+274 was observed by Chandra-ACIS during quiescence in 2013 March 12. In addition, this source has been monitored from the ground-based astronomical observatories of El Teide (Tenerife, Spain), Roque de los Muchachos (La Palma, Spain) and Sierra Nevada (Granada, Spain) since 2011 September, and from the TUBITAK National Observatory (Antalya, Turkey) since 2005 April. We have performed spectral and photometric temporal analyses in order to investigate the quiescent state and transient behavior of this binary system. In 2006, a long mass ejection event took place from the Be star, lasting for about seven years. We also found that a large Be circumstellar disk was present during quiescence, although major X-ray activity was not observed. We made an attempt t...

  12. Against the Wind: Radio Light Curves of Type Ia Supernovae Interacting with Low-Density Circumstellar Shells

    CERN Document Server

    Harris, Chelsea E; Kasen, Daniel N

    2016-01-01

    For decades, a wide variety of observations spanning the radio through optical and on to the x-ray have attempted to uncover signs of type Ia supernovae (SNe Ia) interacting with a circumstellar medium (CSM). The goal of these studies is to constrain the nature of the hypothesized SN Ia mass-donor companion. A continuous CSM is typically assumed when interpreting observations of interaction. However, while such models have been successfully applied to core-collapse SNe, the assumption of continuity may not be accurate for SNe Ia, as shells of CSM could be formed by pre-supernova eruptions (novae). In this work, we model the interaction of SNe with a spherical, low density, finite-extent CSM and create a suite of synthetic radio synchrotron light curves. We find that CSM shells produce sharply peaked light curves, and identify a fiducial set of models that all obey a common evolution and can be used to generate radio light curves for interaction with an arbitrary shell. The relations obeyed by the fiducial mod...

  13. Two Distinct-Absorption X-Ray Components from Type IIn Supernovae: Evidence for Asphericity in the Circumstellar Medium

    CERN Document Server

    Katsuda, Satoru; Bamba, Aya; Terada, Yukikatsu; Fukazawa, Yasushi; Kawabata, Koji; Ohno, Masanori; Sugawara, Yasuharu; Tsuboi, Yohko; Immler, Stefan

    2016-01-01

    We present multi-epoch X-ray spectral observations of three Type IIn supernovae (SNe) 2005kd, 2006jd, and 2010jl, acquired with Chandra, XMM-Newton, Suzaku, and Swift. Previous extensive X-ray studies of SN 2010jl have revealed that X-ray spectra are dominated by thermal emission, which likely arises from a hot plasma heated by a forward shock propagating into a massive circumstellar medium (CSM). Interestingly, an additional soft X-ray component was required to reproduce the spectra at a period of ~1-2 yr after the SN explosion. Although this component is likely associated with the SN, its origin remained an open question. We find a similar, additional soft X-ray component from the other two SNe IIn as well. Given this finding, we present a new interpretation for the origin of this component; it is thermal emission from a forward shock essentially identical to the hard X-ray component, but directly reaches us from a void of the dense CSM. Namely, the hard and soft components are responsible for the heavily- ...

  14. First Science Observations with SOFIA/FORCAST: Properties of Intermediate-Luminosity Protostars and Circumstellar Disks in OMC-2

    CERN Document Server

    Adams, Joseph D; Osorio, Mayra; Macias, Enrique; Megeath, S Thomas; Fischer, William J; Ali, Babar; Calvet, Nuria; D'Alessio, Paola; De Buizer, James M; Gull, George E; Henderson, Charles P; Keller, Luke D; Morris, Mark R; Remming, Ian S; Schoenwald, Justin; Shuping, Ralph Y; Stacey, Gordon; Stanke, Thomas; Stutz, Amelia; Vacca, William

    2012-01-01

    We examine eight young stellar objects in the OMC-2 star forming region based on observations from the SOFIA/FORCAST early science phase, the Spitzer Space Telescope, the Herschel Space Observatory, 2MASS, APEX, and other results in the literature. We show the spectral energy distributions of these objects from near-infrared to millimeter wavelengths, and compare the SEDs with those of sheet collapse models of protostars and circumstellar disks. Four of the objects can be modelled as protostars with infalling envelopes, two as young stars surrounded by disks, and the remaining two objects have double-peaked SEDs. We model the double-peaked sources as binaries containing a young star with a disk and a protostar. The six most luminous sources are found in a dense group within a 0.15 x 0.25 pc region; these sources have luminosities ranging from 300 L_sun to 20 L_sun. The most embedded source (OMC-2 FIR 4) can be fit by a class 0 protostar model having a luminosity of ~50 L_sun and mass infall rate of ~10^-4 sol...

  15. Kepler's Supernova: An Overluminous Type Ia Event Interacting with a Massive Circumstellar Medium at a Very Late Phase

    CERN Document Server

    Katsuda, Satoru; Maeda, Keiichi; Tanaka, Masaomi; Koyama, Katsuji; Tsunemi, Hiroshi; Nakajima, Hiroshi; Maeda, Yoshitomo; Ozaki, Masanobu; Petre, Robert

    2015-01-01

    We have analyzed XMM-Newton, Chandra, and Suzaku observations of Kepler's supernova remnant (SNR) to investigate the properties of both the SN ejecta and the circumstellar medium (CSM). For comparison, we have also analyzed two similarly-aged, ejecta-dominated SNRs: Tycho's SNR, thought to be the remnant of a typical Type Ia SN, and SNR 0509-67.5 in the Large Magellanic Cloud, thought to be the remnant of an overluminous Type Ia SN. By simply comparing the X-ray spectra, we find that line intensity ratios of iron-group elements (IGE) to intermediate-mass elements (IME) for Kepler's SNR and SNR 0509-67.5 are much higher than those for Tycho's SNR. We therefore argue that Kepler is the product of an overluminous Type Ia SN. This inference is supported by our spectral modeling, which reveals the IGE and IME masses respectively to be ~0.95 M_sun and ~0.12 M_sun (Kepler's SNR), ~0.75 M_sun and ~0.34 M_sun (SNR 0509-67.5), and ~0.35 M_sun and ~0.70 M_sun (Tycho's SNR). We find that the CSM component in Kepler's SNR...

  16. WR 120bb and WR 120bc: a pair of WN9h stars with possibly interacting circumstellar shells

    CERN Document Server

    Burgemeister, Sonja; Stringfellow, Guy S; Kniazev, Alexei Y; Todt, Helge; Hamann, Wolf-Rainer; 10.1093/mnras/sts588

    2012-01-01

    Two optically obscured Wolf-Rayet (WR) stars have been recently discovered by means of their infrared (IR) circumstellar shells, which show signatures of interaction with each other. Following the systematics of the WR star catalogues, these stars obtain the names WR\\,120bb and WR\\,120bc. In this paper, we present and analyse new near-IR, $J$, $H$, and $K$-band, spectra using the Potsdam Wolf-Rayet (PoWR) model atmosphere code. For that purpose, the atomic data base of the code has been extended in order to include all significant lines in the near-IR bands. The spectra of both stars are classified as WN9h. As their spectra are very similar the parameters that we obtained by the spectral analyses hardly differ. Despite their late spectral subtype, we found relatively high stellar temperatures of 63 kK. The wind composition is dominated by helium, while hydrogen is depleted to 25 per cent by mass. Because of their location in the Scutum-Centaurus arm, WR\\,120bb and WR\\,120bc appear highly reddened, $A_{K_{\\rm ...

  17. Infrared and X-Ray Evidence for Circumstellar Grain Destruction by the Blast Wave of Supernova 1987A

    CERN Document Server

    Dwek, E; Bouchet, P; Burrows, D N; Challis, P; Danziger, I J; De Buizer, J M; Gehrz, R D; Kirshner, R P; McCray, R; Park, S; Polomski, E F; Woodward, C E

    2007-01-01

    Multiwavelength observations of supernova remnant (SNR) 1987A show that its morphology and luminosity are rapidly changing at X-ray, optical, infrared, and radio wavelengths as the blast wave from the explosion expands into the circumstellar equatorial ring, produced by mass loss from the progenitor star. The observed infrared (IR) radiation arises from the interaction of dust grains that formed in mass outflow with the soft X-ray emitting plasma component of the shocked gas. Spitzer IRS spectra at 5 - 30 microns taken on day 6190 since the explosion show that the emission arises from ~ 1.1E-6 Msun of silicate grains radiating at a temperature of ~180+20-15 K. Subsequent observations on day 7137 show that the IR flux had increased by a factor of 2 while maintaining an almost identical spectral shape. The observed IR-to-X-ray flux ratio (IRX) is consistent with that of a dusty plasma with standard Large Magellanic Cloud dust abundances. IRX has decreased by a factor of ~ 2 between days 6190 and 7137, providing...

  18. The Magellanic zoo: Mid-infrared Spitzer spectroscopy of evolved stars and circumstellar dust in the Magellanic Clouds

    CERN Document Server

    Sloan, G C; Wood, P R; Zijlstra, A A; Bernard-Salas, J; Devost, D; Houck, J R

    2008-01-01

    We observed a sample of evolved stars in the Large and Small Magellanic Clouds (LMC and SMC) with the Infrared Spectrograph on the Spitzer Space Telescope. Comparing samples from the SMC, LMC, and the Galaxy reveals that the dust-production rate depends on metallicity for oxygen-rich stars, but carbon stars with similar pulsation properties produce similar quantities of dust, regardless of their initial metallicity. Other properties of the oxygen-rich stars also depend on metallicity. As the metallicity decreases, the fraction of naked (i.e. dust-free) stars increases, and among the naked stars, the strength of the 8 um absorption band from SiO decreases. Our sample includes several massive stars in the LMC with long pulsation periods which produce significant amounts of dust, probably because they are young and relatively metal rich. Little alumina dust is seen in circumstellar shells in the SMC and LMC, unlike in Galactic samples. Three oxygen-rich sources also show emission from magnesium-rich crystalline ...

  19. AKARI Infrared Observations of the Supernova Remnant G292.0+1.8: Unveiling Circumstellar Medium and Supernova Ejecta

    CERN Document Server

    Lee, Ho-Gyu; Moon, Dae-Sik; Sakon, Itsuki; Onaka, Takashi; Jeong, Woong-Seob; Kaneda, Hidehiro; Nozawa, Takaya; Kozasa, Takashi

    2009-01-01

    We present the results of AKARI observations of the O-rich supernova remnant G292.0+1.8 using six IRC and four FIS bands covering 2.7-26.5 um and 50-180 um, respectively. The AKARI images show two prominent structures; a bright equatorial ring structure and an outer elliptical shell structure. The equatorial ring structure is clumpy and incomplete with its western end opened. The outer shell is almost complete and slightly squeezed along the north-south direction. The central position of the outer shell is ~ 1' northwest from the embedded pulsar and coincides with the center of the equatorial ring structure. The equatorial ring and the elliptical shell structures were partly visible in optical and/or X-rays, but they are much more clearly revealed in our AKARI images. There is no evident difference in infrared colors of the two prominent structures, which is consistent with the previous proposition that both structures are of circumstellar origin. However, we have detected faint infrared emission of a conside...

  20. Line-driven ablation of circumstellar disks: I. Optically thin decretion disks of classical Oe/Be stars

    CERN Document Server

    Kee, N D; Sundqvist, J O

    2016-01-01

    The extreme luminosities of hot, massive stars drive strong stellar winds through UV line-scattering. For OB stars with an orbiting circumstellar disk, we explore the effect of such line-scattering in ablating disk material, initially focusing on the marginally optically thin decretion disks of classical Oe and Be stars. For this we apply a multi-dimensional radiation-hydrodynamics code, assuming optically thin ray tracing for the stellar continuum and a multi-ray Sobolev treatment of the line transfer. This accounts for desaturation of line-absorption by Keplerian shear in the disk, and associated driving by non-radial photons. Results show dense, intermediate-speed surface ablation, consistent with the strong, blue-shifted absorption seen in UV wind lines of Be shell stars. The asymptotic ablation rate is typically an order-unity factor times the stellar wind mass loss rate, leading to disk destruction times of order months to years for Be disks, consistent with observations. The much stronger radiative for...

  1. Closing the loop.

    Science.gov (United States)

    Dassau, E; Atlas, E; Phillip, M

    2011-02-01

    Closed-loop algorithms can be found in every aspect of everyday modern life. Automation and control are used constantly to provide safety and to improve quality of life. Closed-loop systems and algorithms can be found in home appliances, automobiles, aviation and more. Can one imagine nowadays driving a car without ABS, cruise control or even anti-sliding control? Similar principles of automation and control can be used in the management of diabetes mellitus (DM). The idea of an algorithmic/technological way to control glycaemia is not new and has been researched for more than four decades. However, recent improvements in both glucose-sensing technology and insulin delivery together with advanced control and systems engineering made this dream of an artificial pancreas possible. The artificial pancreas may be the next big step in the treatment of DM since the use of insulin analogues. An artificial pancreas can be described as internal or external devices that use continuous glucose measurements to automatically manage exogenous insulin delivery with or without other hormones in an attempt to restore glucose regulation in individuals with DM using a control algorithm. This device as described can be internal or external; can use different types of control algorithms with bi-hormonal or uni-hormonal design; and can utilise different ways to administer them. The different designs and implementations have transitioned recently from in silico simulations to clinical evaluation stage with practical applications in mind. This may mark the beginning of a new era in diabetes management with the introduction of semi-closed-loop systems that can prevent or minimise nocturnal hypoglycaemia, to hybrid systems that will manage blood glucose (BG) levels with minimal user intervention to finally fully automated systems that will take the user out of the loop. More and more clinical trials will be needed for the artificial pancreas to become a reality but initial encouraging

  2. Do closed universes recollapse?

    Science.gov (United States)

    Tipler, Frank J.

    The conditions for recollapse in universes with compact maximal hypersurfaces are investigated theoretically, reviewing the results of recent investigations. The importance of recollapse for observational astrophysics is briefly discussed, and particular attention is given to the implications of maximal hypersurfaces and to recollapse in S3 Friedmann universes. It is conjectured that all globally hyperbolic C2 maximally extended spatially homogeneous closed universes with S3 or S2 x S1 topology and with stress-energy tensors obeying the strong-energy, positive-pressure, dominant-energy, and matter-regularity conditions do expand from an all-encompassing initial singularity to a maximal hypersurface and then recollapse to an all-encompassing final singularity.

  3. Science policy up close

    CERN Document Server

    Marburger, John H

    2015-01-01

    In a career that included tenures as president of Stony Brook University, director of Brookhaven National Laboratory, and science advisor to President George W. Bush, John Marburger (1941 2011) found himself on the front line of battles that pulled science ever deeper into the political arena. From nuclear power to global warming and stem cell research, science controversies, he discovered, are never just about science. Science Policy Up Close" presents Marburger s reflections on the challenges science administrators face in the twenty-first century. In each phase of public service Marburger came into contact with a new dimension of science policy. The Shoreham Commission exposed him to the problem of handling a volatile public controversy over nuclear power. The Superconducting Super Collider episode gave him insights into the collision between government requirements and scientists expectations and feelings of entitlement. The Directorship of Brookhaven taught him how to talk to the public about the risks ...

  4. Jealousy and Relationship Closeness

    Directory of Open Access Journals (Sweden)

    Mark Attridge

    2013-02-01

    Full Text Available This study confirmed a hypothesis from the Emotion-in-Relationships conceptual model, which predicts that greater interdependence between relationship partners—or closeness—creates the potential for jealousy. The study also sought to better define the positive side of romantic jealousy in addition to its more negative attributes. College students in premarital relationships (N = 229 completed a questionnaire, including 27 different measures and the Multidimensional Jealousy Scale. Select data were obtained from 122 cases at 3-month follow-up. Each jealousy scale was tested for associations with demographic (age, sex, and race, person (life satisfaction, loneliness, romantic attachment styles, love styles, and romantic beliefs, and relationship (affective, closeness, and social exchange theory constructs. Results clearly distinguished emotional/reactive jealousy as mostly “good” and cognitive/suspicious jealousy as “bad.” Behavioral jealousy was associated with few measures. Implications are discussed for the interdependence model of relationships and the transactional model of jealousy.

  5. Circumstellar material in the Vega inner system revealed by CHARA/FLUOR

    CERN Document Server

    Absil, O; Augereau, J C; Berger, D H; Brummelaar, T A; Folco, E; Foresto, V C; Kervella, P; McAlister, H A; Merand, A; Ridgway, S T; Sturmann, J; Sturmann, L; Turner, N H

    2006-01-01

    Only a handful of debris disks have been imaged up to now. Due to the need for high dynamic range and high angular resolution, very little is known about the inner planetary region, where small amounts of warm dust are expected to be found. We investigate the close neighbourhood of Vega with the help of infrared stellar interferometry and estimate the integrated K-band flux originating from the central 8 AU of the debris disk. We performed precise visibility measurements at both short (~30 m) and long (~150 m) baselines with the FLUOR beam-combiner installed at the CHARA Array (Mt Wilson, California) in order to separately resolve the emissions from the extended debris disk (short baselines) and from the stellar photosphere (long baselines). After revising Vega's K-band angular diameter (3.202+/-0.005 mas), we show that a significant deficit in squared visibility (1.88+/-0.34%) is detected at short baselines with respect to the best-fit uniform disk stellar model. This deficit can be either attributed to the ...

  6. Ultraviolet Spectroscopy of Type IIb Supernovae: Diversity and the Impact of Circumstellar Material

    CERN Document Server

    Ben-Ami, Sagi; Gal-Yam, Avishay; Mazzali, Paolo A; Filippenko, Alexei V; Horesh, Assaf; Matheson, Thomas; Modjaz, Maryam; Sauer, Daniel N; Silverman, Jeffrey M; Smith, Nathan; Yaron, Ofer

    2014-01-01

    We present new Hubble Space Telescope (HST) multi-epoch ultraviolet (UV) spectra of the bright Type IIb SN 2013df, and undertake a comprehensive anal- ysis of the set of four Type IIb supernovae for which HST UV spectra are available (SN 1993J, SN 2001ig, SN 2011dh, and SN 2013df). We find strong diversity in both continuum levels and line features among these objects. We use radiative-transfer models that fit the optical part of the spectrum well, and find that in three of these four events we see a UV continuum flux excess, apparently unaffected by line absorption. We hypothesize that this emission originates above the photosphere, and is related to interaction with circumstel- lar material (CSM) located in close proximity to the SN progenitor. In contrast, the spectra of SN 2001ig are well fit by single-temperature models, display weak continuum and strong reverse-fluorescence features, and are similar to spectra of radioactive 56Ni-dominated Type Ia supernovae. A comparison of the early shock-cooling comp...

  7. Searching for signatures of planet formation in stars with circumstellar debris discs

    CERN Document Server

    Maldonado, J; Villaver, E; Montesinos, B; Mora, A

    2015-01-01

    (Abridged) Tentative correlations between the presence of dusty debris discs and low-mass planets have been presented. In parallel, detailed chemical abundance studies have reported different trends between samples of planet and non-planet hosts. We determine in a homogeneous way the metallicity, and abundances of a sample of 251 stars including stars with known debris discs, with debris discs and planets, and only with planets. Stars with debris discs and planets have the same [Fe/H] behaviour as stars hosting planets, and they also show a similar -Tc trend. Different behaviour in the -Tc trend is found between the samples of stars without planets and the samples of planet hosts. In particular, when considering only refractory elements, negative slopes are shown in cool giant planet hosts, whilst positive ones are shown in stars hosting low-mass planets. Stars hosting exclusively close-in giant planets show higher metallicities and positive -Tc slope. A search for correlations between the -Tc slopes and the ...

  8. A HST study of the environment of the Herbig Ae/Be star LkHa 233 and its bipolar jet

    CERN Document Server

    Melnikov, Stanislav Yu; Eislöffel, Jochen; Bacciotti, Francesca; Locatelli, Ugo; Ray, Thomas P

    2008-01-01

    We present the results of HST/STIS and WFPC2 observations of LkHa 233 and its environment. LkHa233 is a Herbig Ae/Be star with a collimated bipolar jet. We investigate optical forbidden lines along the LkHa 233 jet to determine physical parameters of this jet (electron density n_e, hydrogen ionisation fraction x_e, electron temperature T_e, and mass density n_H). The knowledge of these parameters allows us a direct comparison of a jet from a Herbig star with those from T Tauri stars. The WFPC2 images in broad-band filters clearly show a dark lane caused either by a circumstellar disk or a dust torus. In the blueshifted lobe, n_e is close to or above the critical density for [SII] lines (2.5x10^4 cm^-3) in the first arcsecond and decreases with distance from the source. The ionisation x_e~0.2-0.6 gently rises for the first 500 AU of the flow and shows two re-ionisation events further away from the origin. The T_e varies along the flow between 10^4 K and 3x10^4 K. The (radial) outflow velocities are ~ 80-160 km...

  9. Closing the Knowledge Gap in Foreign Markets

    DEFF Research Database (Denmark)

    Lyles, Marjorie A.; Pedersen, Torben; Petersen, Bent

    The study explores how firms close their knowledge gaps in relation to business environments of foreign markets. Potential determinants are derived from traditional internationalization process theory as well as more recent literature on organizational learning processes, including the concept...... of absorptive capacity. Building on these two literature streams a conceptual model is developed and tested on a set of primary data of Danish firms and their foreign market operations. The empirical study suggests that factors considered essential in traditional internationalization process theory...

  10. On the properties of dust and gas in the environs of V838 Monocerotis

    Science.gov (United States)

    Exter, K. M.; Cox, N. L. J.; Swinyard, B. M.; Matsuura, M.; Mayer, A.; De Beck, E.; Decin, L.

    2016-12-01

    Aims: We aim to probe the close and distant circumstellar environments of the stellar outburst object V838 Mon. Methods: Herschel far-infrared imaging and spectroscopy were taken at several epochs to probe the central point source and the extended environment of V838 Mon. PACS and SPIRE maps were used to obtain photometry of the dust immediately around V838 Mon, and in the surrounding infrared-bright region. These maps were fitted in 1d and 2d to measure the temperature, mass, and β of the two dust sources. PACS and SPIRE spectra were used to detect emission lines from the extended atmosphere of the star, which were then modelled to study the physical conditions in the emitting material. HIFI spectra were taken to measure the kinematics of the extended atmosphere but unfortunately yielded no detections. Results: Fitting of the far-infrared imaging of V838 Mon reveals 0.5-0.6 M⊙ of ≈19 K dust in the environs (≈2.7 pc) surrounding V838 Mon. The surface-integrated infrared flux (signifying the thermal light echo), and derived dust properties do not vary significantly between the different epochs. We measured the photometry of the point source. As the peak of the SED (Spectral Energy Distribution) lies outside the Herschel spectral range, it is only by incorporating data from other observatories and previous epochs that we can usefully fit the SED; with this we explicitly assume no evolution of the point source between the epochs. We find that warm dust with a temperature 300 K distributed over a radius of 150-200 AU. We fit the far-infrared lines of CO arising from the point source, from an extended environment around V838 Mon. Assuming a model of a spherical shell for this gas, we find that the CO appears to arise from two temperature zones: a cold zone (Tkin ≈ 18 K) that could be associated with the ISM or possibly with a cold layer in the outermost part of the shell, and a warm (Tkin ≈ 400 K) zone that is associated with the extended environment of V838

  11. High-Velocity Features in Type Ia Supernovae from a Compact Circumstellar Shell

    Science.gov (United States)

    Mulligan, Brian W.; Wheeler, J. Craig

    2017-05-01

    High-velocity features (HVF) of Ca prior to B-band maximum light are a ubiquitous property of Type Ia supernovae (SN Ia), but the origin of this high-velocity material is unknown. It may result from ejection of material during the explosion, detonation of material on the surface prior to the supernova or interaction with a companion or material in the nearby environment. Here, we introduce the methods we use to simulate the interaction of SN Ia ejecta with a shell of material surrounding the progenitor at a distance of less than 1 R⊙. Assuming free expansion, constant ion state and excitation temperature, we generate synthetic spectra from the data showing the effect of equation of state, explosion model, and the width, initial density profile and mass of the shell on the appearance and temporal evolution of the Ca ii near-infrared triplet (CaNIR). The Ca abundance of the shell is taken to be a free parameter. We compare the evolution of the pseudo-equivalent width (pEW) of the CaNIR feature resulting from these models to observational results from Silverman et al. We find that the mass of the shell must be less than 0.012 ± 0.004 M⊙. We discuss potential ambiguities in observational methods of determining the pEW of the HVF.

  12. High-Velocity Features in Type Ia Supernovae from a Compact Circumstellar Shell

    Science.gov (United States)

    Mulligan, Brian W.; Wheeler, J. Craig

    2017-01-01

    High-velocity features (HVF) of Ca prior to B-band maximum light are a ubiquitous property of Type Ia supernovae (SN Ia), but the origin of this high-velocity material is unknown. It may result from ejection of material during the explosion, detonation of material on the surface prior to the supernova, or interaction with a companion or material in the nearby environment. Here we introduce the methods we use to simulate the interaction of SN Ia ejecta with a shell of material surrounding the progenitor at a distance of less than 1 R⊙. Assuming free expansion, constant ion state and excitation temperature, we generate synthetic spectra from the data showing the effect of equation of state, explosion model, and the width, initial density profile, and mass of the shell on the appearance and temporal evolution of the Ca II near-infrared triplet (CaNIR). The Ca abundance of the shell is taken to be a free parameter. We compare the evolution of the pseudo-equivalent width (pEW) of the CaNIR feature resulting from these models to observational results. We find that the mass of the shell must be less than 0.012 ± 0.004 M⊙. We discuss potential ambiguities in observational methods of determining the pEW of the HVF.

  13. Closed cycle propulsion for small unmanned aircraft

    Science.gov (United States)

    Hays, Thomas Chadwick

    This study evaluates the merit of closed cycle propulsion systems for use in unmanned systems. The complexity and added weight of closed cycle engines is offset by benefits in high altitude performance, operation in polluted air environments, multi-fuel operation, and potential for flight in low oxygen environments using generic thermal heat sources. Although most closed thermal cycles cannot match the efficiency and power density potential of internal combustion engines (ICE) and turbomachines in aircraft propulsion applications, the addition of design requirements regarding noise output, and operation at high altitude results in IC and CC engine's performance becoming much more comparable. Muffling devices increase backpressure on internal combustion engines thereby reducing power output and efficiency. Multi stage turbo supercharging for operation at high altitude can in some cases increase efficiency of ICE's, but at the result of significant additional complexity and cost that also reduces practical reliability because of the often intricate mechanisms involved. It is in these scenarios that closed cycle engines offer a comparable performance alternative that may prove to be simpler, cheaper, and more reliable than high altitude or low noise internal combustion or turbomachine propulsion systems.

  14. Closing open SDL-systems for model checking with DTSpin

    NARCIS (Netherlands)

    Ioustinova, N.; Sidorova, N.; Steffen, M.

    2002-01-01

    Model checkers like Spin can handle closed reactive systems, only. Thus to handle open systems, in particular when using assume-guarantee reasoning, we need to be able to close (sub-)systems, which is commonly done by adding an environment process. For models with asynchronous message-passing commun

  15. HIGH-DENSITY CIRCUMSTELLAR INTERACTION IN THE LUMINOUS TYPE IIn SN 2010jl: THE FIRST 1100 DAYS

    Energy Technology Data Exchange (ETDEWEB)

    Fransson, Claes; Ergon, Mattias; Sollerman, Jesper [Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, SE-106 91 Stockholm (Sweden); Challis, Peter J.; Kirshner, Robert P.; Marion, G. H.; Milisavljevic, Dan; Friedman, Andrew S.; Chornock, Ryan; Czekala, Ian; Soderberg, Alicia [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Chevalier, Roger A. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904 (United States); France, Kevin [CASA, University of Colorado, 593UCB Boulder, CO 80309-0593 (United States); Smith, Nathan [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Bufano, Filomena [Departamento de Ciencias Fisicas, Universidad Andres Bello, Avda. Republica 252, Santiago (Chile); Kangas, Tuomas [Tuorla Observatory, University of Turku, Väisäläntie 20 FI-21500 Piikkiö (Finland); Larsson, Josefin [KTH, Department of Physics, and the Oskar Klein Centre, AlbaNova, SE-106 91 Stockholm (Sweden); Mattila, Seppo [Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Väisäläntie 20 FI-21500 Piikkiö (Finland); Benetti, Stefano [INAF-Osservatorio Astronomico di Padova, Vicolo dellOsservatorio 5, I-35122 Padova (Italy)

    2014-12-20

    Hubble Space Telescope and ground-based observations of the Type IIn supernova (SN) 2010jl are analyzed, including photometry and spectroscopy in the ultraviolet, optical, and near-IR bands, 26-1128 days after first detection. At maximum, the bolometric luminosity was ∼3 × 10{sup 43} erg s{sup –1} and even at 850 days exceeds 10{sup 42} erg s{sup –1}. A near-IR excess, dominating after 400 days, probably originates in dust in the circumstellar medium (CSM). The total radiated energy is ≳ 6.5 × 10{sup 50} erg, excluding the dust component. The spectral lines can be separated into one broad component that is due to electron scattering and one narrow with expansion velocity ∼100 km s{sup –1} from the CSM. The broad component is initially symmetric around zero velocity but becomes blueshifted after ∼50 days, while remaining symmetric about a shifted centroid velocity. Dust absorption in the ejecta is unlikely to explain the line shifts, and we attribute the shift instead to acceleration by the SN radiation. From the optical lines and the X-ray and dust properties, there is strong evidence for large-scale asymmetries in the CSM. The ultraviolet lines indicate CNO processing in the progenitor, while the optical shows a number of narrow coronal lines excited by the X-rays. The bolometric light curve is consistent with a radiative shock in an r {sup –2} CSM with a mass-loss rate of M-dot ∼0.1  M{sub ⊙} yr{sup −1}. The total mass lost is ≳ 3 M {sub ☉}. These properties are consistent with the SN expanding into a CSM characteristic of a luminous blue variable progenitor with a bipolar geometry. The apparent absence of nuclear processing is attributed to a CSM that is still opaque to electron scattering.

  16. FLASH SPECTROSCOPY: EMISSION LINES FROM THE IONIZED CIRCUMSTELLAR MATERIAL AROUND <10-DAY-OLD TYPE II SUPERNOVAE

    Energy Technology Data Exchange (ETDEWEB)

    Khazov, D.; Yaron, O.; Gal-Yam, A.; Manulis, I.; Rubin, A.; Ofek, E. O.; Horesh, A. [Benoziyo Center for Astrophysics, Faculty of Physics, The Weizmann Institute for Science, Rehovot 76100 (Israel); Kulkarni, S. R.; Kasliwal, M. M.; Cao, Y.; Perley, D. [Astronomy Department, California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA 91125 (United States); Arcavi, I.; Howell, D. A. [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Goleta, CA 93111 (United States); Sollerman, J. [The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, SE-10691 Stockholm (Sweden); Sullivan, M. [School of Physics and Astronomy, University of Southampton, Southampton, SO17 1BJ (United Kingdom); Filippenko, A. V.; Nugent, P. E. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Cenko, S. B. [Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MD 20771 (United States); Silverman, J. M. [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States); Ebeling, H. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); and others

    2016-02-10

    Supernovae (SNe) embedded in dense circumstellar material (CSM) may show prominent emission lines in their early-time spectra (≤10 days after the explosion), owing to recombination of the CSM ionized by the shock-breakout flash. From such spectra (“flash spectroscopy”), we can measure various physical properties of the CSM, as well as the mass-loss rate of the progenitor during the year prior to its explosion. Searching through the Palomar Transient Factory (PTF and iPTF) SN spectroscopy databases from 2009 through 2014, we found 12 SNe II showing flash-ionized (FI) signatures in their first spectra. All are younger than 10 days. These events constitute 14% of all 84 SNe in our sample having a spectrum within 10 days from explosion, and 18% of SNe II observed at ages <5 days, thereby setting lower limits on the fraction of FI events. We classified as “blue/featureless” (BF) those events having a first spectrum that is similar to that of a blackbody, without any emission or absorption signatures. It is possible that some BF events had FI signatures at an earlier phase than observed, or that they lack dense CSM around the progenitor. Within 2 days after explosion, 8 out of 11 SNe in our sample are either BF events or show FI signatures. Interestingly, we found that 19 out of 21 SNe brighter than an absolute magnitude M{sub R} = −18.2 belong to the FI or BF groups, and that all FI events peaked above M{sub R} = −17.6 mag, significantly brighter than average SNe II.

  17. A SELF-CONSISTENT MODEL OF THE CIRCUMSTELLAR DEBRIS CREATED BY A GIANT HYPERVELOCITY IMPACT IN THE HD 172555 SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, B. C.; Melosh, H. J. [Department of Physics, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907 (United States); Lisse, C. M. [JHU-APL, 11100 Johns Hopkins Road, Laurel, MD 20723 (United States); Chen, C. H. [STScI, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Wyatt, M. C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Thebault, P. [LESIA, Observatoire de Paris, F-92195 Meudon Principal Cedex (France); Henning, W. G. [NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States); Gaidos, E. [Department of Geology and Geophysics, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); Elkins-Tanton, L. T. [Department of Terrestrial Magnetism, Carnegie Institution for Science, Washington, DC 20015 (United States); Bridges, J. C. [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); Morlok, A., E-mail: johns477@purdue.edu [Department of Physical Sciences, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom)

    2012-12-10

    Spectral modeling of the large infrared excess in the Spitzer IRS spectra of HD 172555 suggests that there is more than 10{sup 19} kg of submicron dust in the system. Using physical arguments and constraints from observations, we rule out the possibility of the infrared excess being created by a magma ocean planet or a circumplanetary disk or torus. We show that the infrared excess is consistent with a circumstellar debris disk or torus, located at {approx}6 AU, that was created by a planetary scale hypervelocity impact. We find that radiation pressure should remove submicron dust from the debris disk in less than one year. However, the system's mid-infrared photometric flux, dominated by submicron grains, has been stable within 4% over the last 27 years, from the Infrared Astronomical Satellite (1983) to WISE (2010). Our new spectral modeling work and calculations of the radiation pressure on fine dust in HD 172555 provide a self-consistent explanation for this apparent contradiction. We also explore the unconfirmed claim that {approx}10{sup 47} molecules of SiO vapor are needed to explain an emission feature at {approx}8 {mu}m in the Spitzer IRS spectrum of HD 172555. We find that unless there are {approx}10{sup 48} atoms or 0.05 M{sub Circled-Plus} of atomic Si and O vapor in the system, SiO vapor should be destroyed by photo-dissociation in less than 0.2 years. We argue that a second plausible explanation for the {approx}8 {mu}m feature can be emission from solid SiO, which naturally occurs in submicron silicate ''smokes'' created by quickly condensing vaporized silicate.

  18. Two Distinct-absorption X-Ray Components from Type IIn Supernovae: Evidence for Asphericity in the Circumstellar Medium

    Science.gov (United States)

    Katsuda, Satoru; Maeda, Keiichi; Bamba, Aya; Terada, Yukikatsu; Fukazawa, Yasushi; Kawabata, Koji; Ohno, Masanori; Sugawara, Yasuharu; Tsuboi, Yohko; Immler, Stefan

    2016-12-01

    We present multi-epoch X-ray spectral observations of three Type IIn supernovae (SNe), SN 2005kd, SN 2006jd, and SN 2010jl, acquired with Chandra, XMM-Newton, Suzaku, and Swift. Previous extensive X-ray studies of SN 2010jl have revealed that X-ray spectra are dominated by thermal emission, which likely arises from a hot plasma heated by a forward shock propagating into a massive circumstellar medium (CSM). Interestingly, an additional soft X-ray component was required to reproduce the spectra at a period of ˜1-2 years after the SN explosion. Although this component is likely associated with the SN, its origin remained an open question. We find a similar, additional soft X-ray component from the other two SNe IIn as well. Given this finding, we present a new interpretation for the origin of this component; it is thermal emission from a forward shock essentially identical to the hard X-ray component, but directly reaches us from a void of the dense CSM. Namely, the hard and soft components are responsible for the heavily and moderately absorbed components, respectively. The co-existence of the two components with distinct absorptions as well as the delayed emergence of the moderately absorbed X-ray component could be evidence for asphericity of the CSM. We show that the X-ray spectral evolution can be qualitatively explained by considering a torus-like geometry for the dense CSM. Based on our X-ray spectral analyses, we estimate the radius of the torus-like CSM to be on the order of ˜5 × 1016 cm.

  19. Closed suction drain with bulb

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/patientinstructions/000039.htm Closed suction drain with bulb To use the sharing features on this page, please enable JavaScript. A closed suction drain is used to remove fluids that build ...

  20. Closing photoconductive semiconductor switches

    Energy Technology Data Exchange (ETDEWEB)

    Loubriel, G.M.; Zutavern, F.J.; Hjalmarson, H.P.; O' Malley, M.W.

    1989-01-01

    One of the most important limitations of Photoconductive Semiconductor Switches (PCSS) for pulsed power applications is the high laser powers required to activate the switches. In this paper, we discuss recent developments on two different aspects of GaAs PCSS that result in reductions in laser power by a factor of nearly 1000. The advantages of using GaAs over Si are many. First of all, the resistivity of GaAs can be orders of magnitude higher than that of the highest resistivity Si material, thus allowing GaAs switches to withstand dc voltages without thermal runaway. Secondly, GaAs has a higher carrier mobility than Si and, thus, is more efficient (per carrier). Finally, GaAs switches can have naturally fast (ns) opening times at room temperature and low fields, microsecond opening times at liquid nitrogen temperature of 77 K, or, on demand, closing and opening at high fields and room temperature by a mechanism called lock-on (see Ref. 1). By contrast, Si switches typically opening times of milliseconds. The amount of laser light required to trigger GaAs for lock-on, or at 77 K, is about three orders of magnitude lower than at room temperature. In this paper we describe the study of lock-on in GaAs and InP, as well as switching of GaAs at 77 K. We shall show that when GaAs is switched at 77 K, the carrier lifetime is about three orders of magnitude longer than it is at room temperature. We shall explain the change in lifetime in terms of the change in electron capture cross section of the deep levels in GaAs (these are defect or impurity levels in the band gap). In the second section, we describe the lock-on effect, now seen in GaAs and InP, and at fields as high as 70 kV/cm. We show how lock-on can be tailored by changing the GaAs temperature or by neutron bombardment. In the third section, we discuss possible lock-on mechanisms. 5 refs., 5 figs.

  1. 手足口病患者家庭密切接触者肠道病毒感染及环境污染状况调查%Study on enterovirus infection in family close contacts of patients with hand, foot and mouth disease and the contamination of environment

    Institute of Scientific and Technical Information of China (English)

    孙立梅; 林锦炎; 曾汉日; 康敏; 郑焕英; 邓爱萍; 何剑峰; 柯昌文; 张永慧

    2012-01-01

    Objective To understand the enterovirus infection in family close contacts of patients with hand,foot and mouth disease (HFMD) and the contamination of environment.Methods Forty-one HFMD cases confirmed by laboratory from web-based surveillance system during July to August 2010 in Guangdong Province were selected.All members of the cases′ family were investigated by collecting their information on demography,habit of domestic hygiene and hygiene status in household.The stool samples of all members and the smear samples from the surface of family belongings from 16 families were collected and the enterovirus was detected by real time quantitative polymerase chain reaction.The data were analyzed by chi square teat and t test.Results Forty-one HFMD cases′ families and 135 close contacts were included in this survey.The infection rate of the enterovirus was 39.2% (53/135) in all close contacts.Of all the investigated families,the infectionrate was 58.5% (24/41) in family with one or more close contacts and 9.8% (4/41) in family with all close contacts.The differences of infection rates of enterovirus among the members of parents (32.5%,25/77),grandparents/aunts/ uncles (43.3%,13/30) and cousins (53.6%,15/28) didn′t show statistical significance (χ2 =4.07,P=0.131).The infection rate of enterovirus in close contacts from family with more than 5 members was higher than that from family with 4 or less members (OR=1.4,95%CI 1.1-1.9).Among 135 close contacts,27.4% (37/135) were infected with the same types of entervirus as that of HFMD case in the family and 11.9% (16/135) were infected with the different virus types.In 33 family belongings samples from 16 families,the positive rate of enterovirus detection was 6.1% (2/33).Between 17 families with enterovirus testing negative and 23 families with enterovirus testing positive in close contacts,there were no statistical differences of the family hygiene status,hand-washing of babysitter

  2. 40 CFR 63.172 - Standards: Closed-vent systems and control devices.

    Science.gov (United States)

    2010-07-01

    ... olfactory indications of leaks. (2) If the vapor collection system or closed-vent system is constructed of... 40 Protection of Environment 9 2010-07-01 2010-07-01 false Standards: Closed-vent systems and... Standards: Closed-vent systems and control devices. (a) Owners or operators of closed-vent systems...

  3. Nanotechnology and the Environment

    Directory of Open Access Journals (Sweden)

    Elena Serrano

    2010-05-01

    Full Text Available This book intends to present a comprehensive overview of recent progress with regard to different aspects of nanomaterials research and development that are closely related to their manufacture process, through to their release to the environment, identifying the critical areas undergoing further research.

  4. Line-driven ablation of circumstellar discs - I. Optically thin decretion discs of classical Oe/Be stars

    Science.gov (United States)

    Kee, Nathaniel Dylan; Owocki, Stanley; Sundqvist, J. O.

    2016-05-01

    The extreme luminosities of massive, hot OB stars drive strong stellar winds through line-scattering of the star's UV continuum radiation. For OB stars with an orbiting circumstellar disc, we explore here the effect of such line-scattering in driving an ablation of material from the disc's surface layers, with initial focus on the marginally optically thin decretion discs of classical Oe and Be stars. For this we apply a multidimensional radiation-hydrodynamics code that assumes simple optically thin ray tracing for the stellar continuum, but uses a multiray Sobolev treatment of the line transfer; this fully accounts for the efficient driving by non-radial rays, due to desaturation of line-absorption by velocity gradients associated with the Keplerian shear in the disc. Results show a dense, intermediate-speed surface ablation, consistent with the strong, blueshifted absorption of UV wind lines seen in Be shell stars that are observed from near the disc plane. A key overall result is that, after an initial adjustment to the introduction of the disc, the asymptotic disc destruction rate is typically just an order-unity factor times the stellar wind mass-loss rate. For optically thin Be discs, this leads to a disc destruction time of order months to years, consistent with observationally inferred disc decay times. The much stronger radiative forces of O stars reduce this time to order days, making it more difficult for decretion processes to sustain a disc in earlier spectral types, and so providing a natural explanation for the relative rarity of Oe stars in the Galaxy. Moreover, the decrease in line-driving at lower metallicity implies both a reduction in the winds that help spin-down stars from near-critical rotation, and a reduction in the ablation of any decretion disc; together these provide a natural explanation for the higher fraction of classical Be stars, as well as the presence of Oe stars, in the lower metallicity Magellanic Clouds. We conclude with a

  5. 2.4-197 mu m spectroscopy of OH/IR stars : the IR characteristics of circumstellar dust in O-rich environments

    NARCIS (Netherlands)

    Sylvester, RJ; Kemper, F; Barlow, MJ; de Jong, T; Waters, LBFM; Tielens, AGGM; Omont, A

    1999-01-01

    Infrared spectra of a number of evolved O-rich stars have been obtained with the Short- and Long-Wavelength spectrometers on board the Infrared Space Observatory. The very broad wavelength coverage (2.4-197 mu m) obtained by combining observations made with the two spectrometers includes practically

  6. A THERMAL INFRARED IMAGING STUDY OF VERY LOW MASS, WIDE-SEPARATION BROWN DWARF COMPANIONS TO UPPER SCORPIUS STARS: CONSTRAINING CIRCUMSTELLAR ENVIRONMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Bailey, Vanessa; Hinz, Philip M.; Su, Kate Y. L.; Hoffmann, William F.; Rieke, George; Rodigas, Timothy; Skemer, Andrew; Vaitheeswaran, Vidhya [Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States); Currie, Thayne [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada); Esposito, Simone; Pinna, Enrico; Puglisi, Alfio [Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Hill, John M. [Large Binocular Telescope Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States); Jones, Terry [School of Physics and Astronomy, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455 (United States); Kim, Jihun [College of Optical Sciences, University of Arizona, 1630 E. University Blvd., Tucson, AZ 85721 (United States); Leisenring, Jarron; Meyer, Michael [Institut fuer Angewandte Physik, Eidgenoessische Technische Hochschule-Zuerich, CH-8093 (Switzerland); Murray-Clay, Ruth; Skrutskie, Michael F. [Harvard-Smithsonian Center for Astrophysics, Harvard University, 60 Garden St., Cambridge, MA 02138 (United States); Nelson, Matthew J., E-mail: vbailey@as.arizona.edu [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); and others

    2013-04-10

    We present a 3-5 {mu}m LBT/MMT adaptive optics imaging study of three Upper Scorpius stars with brown dwarf (BD) companions with very low masses/mass ratios (M{sub BD} <25 M{sub Jup}; M{sub BD}/M{sub *} Almost-Equal-To 1%-2%) and wide separations (300-700 AU): GSC 06214, 1RXS 1609, and HIP 78530. We combine these new thermal IR data with existing 1-4 {mu}m and 24 {mu}m photometry to constrain the properties of the BDs and identify evidence for circumprimary/circumsecondary disks in these unusual systems. We confirm that GSC 06214B is surrounded by a disk, further showing that this disk produces a broadband IR excess due to small dust near the dust sublimation radius. An unresolved 24 {mu}m excess in the system may be explained by the contribution from this disk. 1RXS 1609B exhibits no 3-4 {mu}m excess, nor does its primary; however, the system as a whole has a modest 24 {mu}m excess, which may come from warm dust around the primary and/or BD. Neither object in the HIP 78530 system exhibits near- to mid-IR excesses. We additionally find that the 1-4 {mu}m colors of HIP 78530B match a spectral type of M3 {+-} 2, inconsistent with the M8 spectral type assigned based on its near-IR spectrum, indicating that it may be a low-mass star rather than a BD. We present new upper limits on additional low-mass companions in the system (<5 M{sub Jup} beyond 175 AU). Finally, we examine the utility of circumsecondary disks as probes of the formation histories of wide BD companions, finding that the presence of a disk may disfavor BD formation near the primary with subsequent outward scattering.

  7. A Thermal Infrared Imaging Study of Very Low-Mass, Wide Separation Brown Dwarf Companions to Upper Scorpius Stars: Constraining Circumstellar Environments

    CERN Document Server

    Bailey, Vanessa; Currie, Thayne; Su, Kate Y L; Esposito, Simone; Hill, John M; Hoffmann, William F; Jones, Terry; Kim, Jihun; Leisenring, Jarron; Meyer, Michael; Murray-Clay, Ruth; Nelson, Matthew J; Pinna, Enrico; Puglisi, Alfio; Rieke, George; Rodigas, Timothy; Skemer, Andrew; Skrutskie, Michael F; Vaitheeswaran, Vidhya; Wilson, John C

    2013-01-01

    We present a 3-5um LBT/MMT adaptive optics imaging study of three Upper Scorpius stars with brown dwarf (BD) companions with very low-masses/mass ratios (M_BD < 25M_Jup; M_BD / M_star ~ 1-2%), and wide separations (300-700 AU): GSC 06214, 1RXS 1609, and HIP 78530. We combine these new thermal IR data with existing 1-4um and 24um photometry to constrain the properties of the BDs and identify evidence for circumprimary/secondary disks in these unusual systems. We confirm that GSC 06214B is surrounded by a disk, further showing this disk produces a broadband IR excess due to small dust near the dust sublimation radius. An unresolved 24um excess in the system may be explained by the contribution from this disk. 1RXS 1609B exhibits no 3-4um excess, nor does its primary; however, the system as a whole has a modest 24um excess, which may come from warm dust around the primary and/or BD. Neither object in the HIP 78530 system exhibits near- to mid-IR excesses. We additionally find that the 1-4um colors of HIP 7853...

  8. Properties and Nature of Be Stars: 28. Implications of Systematic Observations for the Nature of the Multiple System with the Be Star o Cassiopeae and its Circumstellar Environment

    Science.gov (United States)

    2010-01-01

    1966, Commun. Lun. Planet. Lab., 4, 99 Kaufer , A. 1988, Rev. Mod. Astrophys., 11, 177 Koubský, P., Ak, H., Harmanec, P., Yang, S., & Božić, H. 2004, in...al. (2000). 3. Two echelle spectrograms secured in the Cassegrain focus of the Ondřejov 2-m telescope with the Heros spectrograph ( Kaufer 1988). 4

  9. Far-UV spectroscopy of the planet-hosting star WASP-13: high-energy irradiance, distance, age, planetary mass-loss rate, and circumstellar environment

    CERN Document Server

    Fossati, L; Koskinen, T; Juvan, I G; Haswell, C A; Lendl, M

    2015-01-01

    Several transiting hot Jupiters orbit relatively inactive main-sequence stars. For some of those, the logR'HK activity parameter lies below the basal level (-5.1). Two explanations have been proposed so far: (i) the planet affects the stellar dynamo, (ii) the logR'HK measurements are biased by extrinsic absorption, either by the interstellar medium (ISM) or by material local to the system. We present here Hubble Space Telescope/COS far-UV spectra of WASP-13, which hosts an inflated hot Jupiter and has a measured logR'HK value (-5.26), well below the basal level. From the star's spectral energy distribution we obtain an extinction E(B-V) = 0.045+/-0.025 mag and a distance d = 232+/-8 pc. We detect at >4 sigma lines belonging to three different ionization states of carbon (C1, C2, and C4) and the Si4 doublet at ~3 sigma. Using far-UV spectra of nearby early G-type stars of known age, we derive a C4/C1 flux ratio-age relation, from which we estimate WASP-13's age to be 5.1+/-2.0 Gyr. We rescale the solar irradia...

  10. Key ecological challenges for closed systems facilities

    Science.gov (United States)

    Nelson, Mark; Dempster, William F.; Allen, John P.

    2013-07-01

    Closed ecological systems are desirable for a number of purposes. In space life support systems, material closure allows precious life-supporting resources to be kept inside and recycled. Closure in small biospheric systems facilitates detailed measurement of global ecological processes and biogeochemical cycles. Closed testbeds facilitate research topics which require isolation from the outside (e.g. genetically modified organisms; radioisotopes) so their ecological interactions and fluxes can be studied separate from interactions with the outside environment. But to achieve and maintain closure entails solving complex ecological challenges. These challenges include being able to handle faster cycling rates and accentuated daily and seasonal fluxes of critical life elements such as carbon dioxide, oxygen, water, macro- and mico-nutrients. The problems of achieving sustainability in closed systems for life support include how to handle atmospheric dynamics including trace gases, producing a complete human diet, recycling nutrients and maintaining soil fertility, the maintenance of healthy air and water and preventing the loss of critical elements from active circulation. In biospheric facilities, the challenge is also to produce analogues to natural biomes and ecosystems, studying processes of self-organization and adaptation in systems that allow specification or determination of state variables and cycles which may be followed through all interactions from atmosphere to soils. Other challenges include the dynamics and genetics of small populations, the psychological challenges for small isolated human groups and backup technologies and strategic options which may be necessary to ensure long-term operation of closed ecological systems.

  11. The circumstellar disc in the Bok globule CB 26: Multi-wavelength observations and modelling of the dust disc and envelope

    CERN Document Server

    Sauter, J; Launhardt, R; Padgett, D L; Stapelfeldt, K R; Pinte, C; Duchêne, G; Ménard, F; McCabe, C -E; Pontoppidan, K; Dunham, M; Bourke, T -L; Chen, J -H

    2009-01-01

    Circumstellar discs are expected to be the nursery of planets. Grain growth within such discs is the first step in the planet formation process. The Bok globule CB 26 harbours such a young disc. We present a detailed model of the edge-on circumstellar disc and its envelope in the Bok globule CB 26. The model is based on HST near-infrared maps in the I, J, H, and K bands, OVRO and SMA radio maps at 1.1mm, 1.3mm and 2.7mm, and the spectral energy distribution (SED) from 0.9 microns to 3mm. New photometric and spectroscopic data from the Spitzer Space Telescope and the Caltech Submilimeter Observatory have been obtained and are part of our analysis. Using the self-consistent radiative transfer code MC3D, the model we construct is able to discriminate parameter sets and dust properties of both its parts, namely envelope and disc. We find that the disc has an inner hole with a radius of 45 +/- 5 AU. Based on a dust model including silicate and graphite the maximum grain size needed to reproduce the spectral millim...

  12. Interferometric observations of non-maser SiO emission from circumstellar envelopes of AGB stars - Acceleration regions and SiO depletion

    Science.gov (United States)

    Sahai, Raghvendra; Bieging, John H.

    1993-01-01

    High- and medium-resolution images of SiO J = 2-1(V = 0) from the circumstellar envelopes (CSEs) of three oxygen-rich stars, Chi Cyg, RX Boo, and IK Tau, were obtained. The SIO images were found to be roughly circular, implying that the CSEs are spherically symmetric on angular-size scales of about 3-9 arcsec. The observed angular half-maximum intensity source radius is nearly independent of the LSR velocity for all three CSEs. Chi Cyg and RX Boo are argued to be less than 450 pc distant, and have mass-loss rates larger than about 10 exp -6 solar mass/yr. In Chi Cyg and RX Boo, the line profiles at the peak of the brightness distribution are rounded, typical of optically-thick emission from a spherical envelope expanding with a constant velocity. In the IK Tau line profiles, an additional narrower central component is present, probably a result of emission from an inner circumstellar shell with a significantly smaller expansion velocity than the extended envelope.

  13. Comparative Spectra of Oxygen-Rich vs. Carbon-Rich Circumstellar Shells: VY Canis Majoris and IRC+10216 at 215-285 GHz

    CERN Document Server

    Tenenbaum, E D; Milam, S N; Woolf, N J; Ziurys, L M

    2010-01-01

    A sensitive (1{\\sigma} rms at 1 MHz resolution ~3 mK) 1 mm spectral line survey (214.5-285.5 GHz) of VY Canis Majoris (VY CMa) and IRC+10216 has been conducted to compare the chemistries of oxygen and carbon-rich circumstellar envelopes. This study was carried out using the Submillimeter Telescope (SMT) of the Arizona Radio Observatory (ARO) with a new ALMA-type receiver. This survey is the first to chemically characterize an O-rich circumstellar shell at millimeter wavelengths. In VY CMa, 128 emission features were detected arising from 18 different molecules, and in IRC+10216, 720 lines were observed, assigned to 32 different species. The 1 mm spectrum of VY CMa is dominated by SO2 and SiS; in IRC +10216, C4H and SiC2 are the most recurrent species. Ten molecules were common to both sources: CO, SiS, SiO, CS, CN, HCN, HNC, NaCl, PN, and HCO+. Sulfur plays an important role in VY CMa, but saturated/unsaturated carbon dominates the molecular content of IRC+10216, producing CH2NH, for example. Although the mol...

  14. Photochemistry in the inner layers of clumpy circumstellar envelopes: formation of water in C-rich objects and of C-bearing molecules in O-rich objects

    CERN Document Server

    Agundez, Marcelino; Guelin, Michel

    2010-01-01

    A mechanism based on the penetration of interstellar ultraviolet photons into the inner layers of clumpy circumstellar envelopes around AGB stars is proposed to explain the non-equilibrium chemistry observed in such objects. We show through a simple modelling approach that in circumstellar envelopes with a certain degree of clumpiness or with moderately low mass loss rates (a few 10^(-7) solar masses per year) a photochemistry can take place in the warm and dense inner layers inducing important changes in the chemical composition. In carbon-rich objects water vapor and ammonia would be formed with abundances of 10^(-8) - 10(^-6) relative to H2, while in oxygen-rich envelopes ammonia and carbon-bearing molecules such as HCN and CS would form with abundances of 10^(-9) - 10^(-7) relative to H2. The proposed mechanism would explain the recent observation of warm water vapor in the carbon-rich envelope IRC +10216 with the Herschel Space Observatory, and predict that H2O should be detectable in other carbon-rich o...

  15. Gemini helium closed cycle cooling system

    Science.gov (United States)

    Lazo, Manuel; Galvez, Ramon; Rogers, Rolando; Solis, Hernan; Tapia, Eduardo; Maltes, Diego; Collins, Paul; White, John; Cavedoni, Chas; Yamasaki, Chris; Sheehan, Michael P.; Walls, Brian

    2008-07-01

    The Gemini Observatory presents the Helium Closed Cycle Cooling System that provides cooling capacity at cryogenic temperatures for instruments and detectors. It is implemented by running three independent helium closed cycle cooling circuits with several banks of compressors in parallel to continuously supply high purity helium gas to cryocoolers located about 100-120 meters apart. This poster describes how the system has been implemented, the required helium pressures and gas flow to reach cryogenic temperature, the performance it has achieved, the helium compressors and cryocoolers in use and the level of vibration the cryocoolers produce in the telescope environment. The poster also describes the new technology for cryocoolers that Gemini is considering in the development of new instruments.

  16. On fuzzy weakly-closed sets

    OpenAIRE

    Mahanta, J.; P. K. Das

    2012-01-01

    A new class of fuzzy closed sets, namely fuzzy weakly closed set in a fuzzy topological space is introduced and it is established that this class of fuzzy closed sets lies between fuzzy closed sets and fuzzy generalized closed sets. Alongwith the study of fundamental results of such closed sets, we define and characterize fuzzy weakly compact space and fuzzy weakly closed space.

  17. Rotational mixing in close binaries

    CERN Document Server

    de Mink, S E; Langer, N; Yoon, S -Ch; Brott, I; Glebbeek, E; Verkoulen, M; Pols, O R

    2008-01-01

    Rotational mixing is a very important but uncertain process in the evolution of massive stars. We propose to use close binaries to test its efficiency. Based on rotating single stellar models we predict nitrogen surface enhancements for tidally locked binaries. Furthermore we demonstrate the possibility of a new evolutionary scenario for very massive (M > 40 solar mass) close (P < 3 days) binaries: Case M, in which mixing is so efficient that the stars evolve quasi-chemically homogeneously, stay compact and avoid any Roche-lobe overflow, leading to very close (double) WR binaries.

  18. Closed planar curves without inflections

    CERN Document Server

    Ohno, Shuntaro; Umehara, Masaaki

    2011-01-01

    We define a computable topological invariant $\\mu(\\gamma)$ for generic closed planar regular curves $\\gamma$, which gives an effective lower bound for the number of inflection points on a given generic closed planar curve. Using it, we classify the topological types of locally convex curves (i.e. closed planar regular curves without inflections) whose numbers of crossings are less than or equal to five. Moreover, we discuss the relationship between the number of double tangents and the invariant $\\mu(\\gamma)$ on a given $\\gamma$.

  19. Proposed Closing Order : St. Vincent

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The attached letter directed to Secretary Morton from the Florida Chapter of The Nature Conservancy recommends the establishment of a Secretarial closing order on...

  20. Pollution hazard closes neutrino lab

    CERN Multimedia

    Jones, Nicola

    2003-01-01

    "A leading astrophysics laboratory in Italy has closed down all but one of its experiments over concerns that toxic polluants could leak form the underground lab into the local water supply" (0.5 page)