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Sample records for reflection nebulae ic4954

  1. THE VARIABLE REFLECTION NEBULA CEPHEUS A EAST

    Hodapp, Klaus W.; Bressert, Eli

    2009-01-01

    We report K'-band imaging observations of the reflection nebula associated with Cepheus A East covering the time interval from 1990 to 2004. Over this time the reflection nebula shows variations of flux distribution, which we interpret as the effect of inhomogeneous and varying extinction in the light path from the illuminating source HW2 to the reflection nebula. The obscuring material is located within typical distances of ∼ 10 AU from the illuminating source.

  2. Properties of interstellar dust in reflection nebulae

    Sellgren, K.

    1988-01-01

    Observations of interstellar dust in reflection nebulae are the closest analog in the interstellar medium to studies of cometary dust in our solar system. The presence of a bright star near the reflection nebula dust provides the opportunity to study both the reflection and emission characteristics of interstellar dust. At 0.1 to 1 micrometer, the reflection nebula emission is due to starlight scattered by dust. The albedo and scattering phase function of the dust is determined from observations of the scattered light. At 50 to 200 micrometers, thermal emission from the dust in equilibrium with the stellar radiation field is observed. The derived dust temperature determines the relative values of the absorption coefficient of the dust at wavelengths where the stellar energy is absorbed and at far infrared wavelengths where the absorbed energy is reradiated. These emission mechanisms directly relate to those seen in the near and mid infrared spectra of comets. In a reflection nebula the dust is observed at much larger distances from the star than in our solar system, so that the equilibrium dust temperature is 50 K rather than 300 K. Thus, in reflection nebulae, thermal emission from dust is emitted at 50 to 200 micrometer

  3. The simplest models of the reflection nebulae

    Voshchinnikov, N.V.

    1977-01-01

    Some models of the reflection nebulue have been considered. The (U-B), (B-V) and (V-R) colors and the U, B, V and R polarization have been calculated for a model of a reflection nebula associated with a large dust cloud. For the cases in which the illuminating star is far from the surface of the cloud, the form of the nebula has been considered to be spherical. If the star is close to the surface of the cloud, a part of the nebura boundary has been considered to be flat. Single scattering within the homogeneous nebula has been assumed. All the calculations use the scattering by spheres as given by the Mie's theory. The effect of variations of chemical composition and size distribution function of the grains and the position of the illuminating star has been examined. Comparison of the theoretical results with the observations of the Merope nebula shows that the dirty ice grains with the refraction index m=1.30-0.02i and size parameter asub(o)=0.5μ represent satisfactorily the observation if the star is embedded 0.7 pc behind the front surface of the nebula

  4. Infrared reflection nebulae in Orion Molecular Cloud

    Pendleton, Y.; Werner, M.W.; Capps, R.; Lester, D.; Hawaii Univ., Honolulu; Texas Univ., Austin)

    1986-01-01

    New observations of Orion Molecular Cloud 2 have been made from 1 to 100 microns using the NASA Infrared Telescope Facility and the Kuiper Airborne Observatory. An extensive program of polarimetry, photometry, and spectrophotometry has shown that the extended emission regions associated with two of the previously known near-infrared sources, IRS 1 and IRS 4, are infrared reflection nebulae, and that the compact sources IRS 1 and IRS 4 are the main luminosity sources in the cloud. The constraints from the far-infrared observations and an analysis of the scattered light from the IRS 1 nebula show that OMC-2/IRS 1 can be characterized by L of 500 solar luminosities or less and T of roughly 1000 K. The near-infrared albedo of the grains in the IRS 1 nebula is greater than 0.08. 27 references

  5. The spatial distribution of infrared radiation from visible reflection nebulae

    Luan, Ling; Werner, Michael W.; Dwek, Eli; Sellgren, Kris

    1989-01-01

    The emission at IRAS 12 and 25 micron bands of reflection nebulae is far in excess of that expected from the longer wavelength equilibrium thermal emission. The excess emission in the IRAS 12 micron band is a general phenomenon, seen in various components of interstellar medium such as IR cirrus clouds, H II regions, atomic and molecular clouds, and also normal spiral galaxies. This excess emission has been attributed to UV excited fluorescence in polycyclic aromatic hydrocarbon (PAH) molecules or to the effect of temperature fluctuations in very small grains. Results are presented of studies of IRAS data on reflection nebulae selected from the van den Bergh reflection nebulae sample. Detailed scans of flux ratio and color temperature across the nebulae were obtained in order to study the spatial distribution of IR emission. A model was used to predict the spatial distribution of IR emission from dust grains illuminated by a B type star. The model was also used to explore the excitation of the IRAS 12 micron band emission as a function of stellar temperature. The model predictions are in good agreement with the analysis of reflection nebulae, illuminated by stars with stellar temperature ranging from 21,000 down to 3,000 K.

  6. Studies of dust grain properties in infrared reflection nebulae.

    Pendleton, Y J; Tielens, A G; Werner, M W

    1990-01-20

    We have developed a model for reflection nebulae around luminous infrared sources embedded in dense dust clouds. The aim of this study is to determine the sizes of the scattering grains. In our analysis, we have adopted an MRN-like power-law size distribution (Mathis, Rumpl, and Nordsieck) of graphite and silicate grains, but other current dust models would give results which were substantially the same. In the optically thin limit, the intensity of the scattered light is proportional to the dust column density, while in the optically thick limit, it reflects the grain albedo. The results show that the shape of the infrared spectrum is the result of a combination of the scattering properties of the dust, the spectrum of the illuminating source, and foreground extinction, while geometry plays a minor role. Comparison of our model results with infrared observations of the reflection nebula surrounding OMC-2/IRS 1 shows that either a grain size distribution like that found in the diffuse interstellar medium, or one consisting of larger grains, can explain the observed shape of the spectrum. However, the absolute intensity level of the scattered light, as well as the observed polarization, requires large grains (approximately 5000 angstroms). By adding water ice mantles to the silicate and graphite cores, we have modeled the 3.08 micrometers ice band feature, which has been observed in the spectra of several infrared reflection nebulae. We show that this ice band arises naturally in optically thick reflection nebulae containing ice-coated grains. We show that the shape of the ice band is diagnostic of the presence of large grains, as previously suggested by Knacke and McCorkle. Comparison with observations of the BN/KL reflection nebula in the OMC-1 cloud shows that large ice grains (approximately 5000 angstroms) contribute substantially to the scattered light.

  7. IRAS surface brightness maps of reflection nebulae in the Pleiades

    Castelaz, Michael W.; Werner, M. W.; Sellgren, K.

    1987-01-01

    Surface brightness maps at 12, 25, 60, and 100 microns were made of a 2.5 deg x 2.5 deg area of the reflection nebulae in the Pleiades by coadding IRAS scans of this region. Emission is seen surrounding 17 Tau, 20 Tau, 23 Tau, and 25 Tau in all four bands, coextensive with the visible reflection nebulosity, and extending as far as 30 arcminutes from the illuminating stars. The infrared energy distributions of the nebulae peak in the 100 micron band, but up to 40 percent of the total infrared power lies in the 12 and 25 micron bands. The brightness of the 12 and 25 micron emission and the absence of temperature gradients at these wavelengths are inconsistent with the predictions of equilibrium thermal emission models. The emission at these wavelengths appears to be the result of micron nonequilibrium emission from very small grains, or from molecules consisting of 10-100 carbon atoms, which have been excited by ultraviolet radiation from the illuminating stars.

  8. POST ASYMPTOTIC GIANT BRANCH BIPOLAR REFLECTION NEBULAE: RESULT OF DYNAMICAL EJECTION OR SELECTIVE ILLUMINATION?

    Koning, N.; Kwok, Sun; Steffen, W.

    2013-01-01

    A model for post asymptotic giant branch bipolar reflection nebulae has been constructed based on a pair of evacuated cavities in a spherical dust envelope. Many of the observed features of bipolar nebulae, including filled bipolar lobes, an equatorial torus, searchlight beams, and a bright central light source, can be reproduced. The effects on orientation and dust densities are studied and comparisons with some observed examples are offered. We suggest that many observed properties of bipolar nebulae are the result of optical effects and any physical modeling of these nebulae has to take these factors into consideration.

  9. IRAS surface brightness maps of visible reflection nebulae: evidence for non-equilibrium infrared emission

    Castelaz, M.W.; Werner, M.W.; Sellgren, K.

    1986-01-01

    Surface brightness maps at 12, 25, 60, and 100 microns of 16 visible reflection nebulae were extracted from the Infrared Astronomy Satellite (IRAS) database. The maps were produced by coadding IRAS survey scans over areas centered on the illuminating stars, and have spatial resolutions of 0.9' x 4' at 12 and 25 microns, 1.8' x 4.5' at 60 microns, and 3.6' x 5' at 100 microns. Extended emission in the four IRAS bandpasses was detected in fourteen of the reflection nebulae. The IRAS data were used to measure the flux of the infrared emission associated with each source. The energy distributions show that the 12 micron flux is greater than the 25 micron flux in 11 of the nebulae, and the peak flux occurs in the 60 or 100 micron bandpass in all 16 nebular. The 60 and 100 micron flux can be approximated by blackbodies with temperatures between 30 and 50 K, consistent with temperatures expected from extrapolation of greybody fits to the 60 and 100 micron data. The excess 12 and 25 micron emission is attributed to a nonequilibrium process such as emission from thermal fluctuations of very small grains excited by single ultraviolet photons, or emission from polycyclic aromatic hydrocarbons (PAHs) excited by ultraviolet radiation. The common features of the energy distributions of the 16 reflection nebulae, also seen in the reflection nebulae associated with the Pleiades, suggest that PAHs or very small grains may be found in most reflection nebulae

  10. The PAH Emission Characteristics of the Reflection Nebula NGC 2023

    Peeters, Els; Bauschlicher, Charles W. Jr.; Allamandola, Louis J.; Tielens, Alexander G. G. M.; Ricca, Alessandra; Wolfire, Mark G.

    2017-01-01

    We present 5–20 μ m spectral maps of the reflection nebula NGC 2023 obtained with the Infrared Spectrograph SL and SH modes on board the Spitzer Space Telescope, which reveal emission from polycyclic aromatic hydrocarbons (PAHs), C 60 , and H 2 superposed on a dust continuum. We show that several PAH emission bands correlate with each other and exhibit distinct spatial distributions that reveal a spatial sequence with distance from the illuminating star. We explore the distinct morphology of the 6.2, 7.7, and 8.6 μ m PAH bands and find that at least two spatially distinct components contribute to the 7–9 μ m PAH emission in NGC 2023. We report that the PAH features behave independently of the underlying plateaus. We present spectra of compact, oval PAHs ranging in size from C 66 to C 210 , determined computationally using density functional theory, and we investigate trends in the band positions and relative intensities as a function of PAH size, charge, and geometry. Based on the NASA Ames PAH database, we discuss the 7–9 μ m components in terms of band assignments and relative intensities. We assign the plateau emission to very small grains with possible contributions from PAH clusters and identify components in the 7–9 μ m emission that likely originate in these structures. Based on the assignments and the observed spatial sequence, we discuss the photochemical evolution of the interstellar PAH family as the PAHs are more and more exposed to the radiation field of the central star in the evaporative flows associated with the Photo-Dissociation Regions in NGC 2023.

  11. The PAH Emission Characteristics of the Reflection Nebula NGC 2023

    Peeters, Els [Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7 (Canada); Bauschlicher, Charles W. Jr. [Entry Systems and Technology Division, Mail Stop 230-3, NASA Ames Research Center, Moffett Field, CA 94035 (United States); Allamandola, Louis J. [NASA Ames Research Center, Space Science Division, Mail Stop 245-6, Moffett Field, CA 94035 (United States); Tielens, Alexander G. G. M. [Leiden Observatory, P.O. Box 9513, 2300 RA Leiden (Netherlands); Ricca, Alessandra [Carl Sagan Center, SETI Institute, 189 N. Bernardo Avenue, Suite 100, Mountain View, CA 94043 (United States); Wolfire, Mark G., E-mail: epeeters@uwo.ca [Astronomy Department, University of Maryland, College Park, MD 20742 (United States)

    2017-02-20

    We present 5–20 μ m spectral maps of the reflection nebula NGC 2023 obtained with the Infrared Spectrograph SL and SH modes on board the Spitzer Space Telescope, which reveal emission from polycyclic aromatic hydrocarbons (PAHs), C{sub 60}, and H{sub 2} superposed on a dust continuum. We show that several PAH emission bands correlate with each other and exhibit distinct spatial distributions that reveal a spatial sequence with distance from the illuminating star. We explore the distinct morphology of the 6.2, 7.7, and 8.6 μ m PAH bands and find that at least two spatially distinct components contribute to the 7–9 μ m PAH emission in NGC 2023. We report that the PAH features behave independently of the underlying plateaus. We present spectra of compact, oval PAHs ranging in size from C{sub 66} to C{sub 210}, determined computationally using density functional theory, and we investigate trends in the band positions and relative intensities as a function of PAH size, charge, and geometry. Based on the NASA Ames PAH database, we discuss the 7–9 μ m components in terms of band assignments and relative intensities. We assign the plateau emission to very small grains with possible contributions from PAH clusters and identify components in the 7–9 μ m emission that likely originate in these structures. Based on the assignments and the observed spatial sequence, we discuss the photochemical evolution of the interstellar PAH family as the PAHs are more and more exposed to the radiation field of the central star in the evaporative flows associated with the Photo-Dissociation Regions in NGC 2023.

  12. The Charge State of Polycyclic Aromatic Hydrocarbons across a Reflection Nebula, an H II Region, and a Planetary Nebula

    Boersma, C.; Bregman, J.; Allamandola, L. J.

    2018-05-01

    Low-resolution Spitzer-IRS spectral map data of a reflection nebula (NGC 7023), H II region (M17), and planetary nebula (NGC 40), totaling 1417 spectra, are analyzed using the data and tools available through the NASA Ames PAH IR Spectroscopic Database. The polycyclic aromatic hydrocarbon (PAH) emission is broken down into PAH charge and size subclass contributions using a database-fitting approach. The resulting charge breakdown results are combined with those derived using the traditional PAH band strength ratio approach, which interprets particular PAH band strength ratios as proxies for PAH charge. Here the 6.2/11.2 μm PAH band strength ratio is successfully calibrated against its database equivalent: the {n}PAH}+}/{n}PAH}0} ratio. In turn, this ratio is converted into the PAH ionization parameter, which relates it to the strength of the radiation field, gas temperature, and electron density. Population diagrams are used to derive the {{{H}}}2 density and temperature. The bifurcated plot of the 8.6 versus 11.2 μm PAH band strength for the northwest photo dissociation region in NGC 7023 is shown to be a robust diagnostic template for the {n}PAH}+}/{n}PAH}0} ratio in all three objects. Template spectra for the PAH charge and size subclasses are determined for each object and shown to favorably compare. Using the determined template spectra from NGC 7023 to fit the emission in all three objects yields, upon inspection of the Structure SIMilarity maps, satisfactory results. The choice of extinction curve proves to be critical. Concluding, the distinctly different astronomical environments of a reflection nebula, H II region, and planetary nebula are reflected in their PAH emission spectra.

  13. Near infrared observations of the visual reflection nebulae NGC 7023, NGC 2023, and NGC 2068

    Sellgren, K.

    1984-01-01

    The emission of the nebulae NGC 7023, 2023, and 2068 at visual wavelengths is due to reflected starlight. Recently the infrared emission of these nebulae has been found to consist not of reflected light, but rather to be due to some other emission process. Spectra of the infrared emission at nebular positions in NGC 7023 and NGC 2023 are shown. The infrared emission consists of a smooth continuum which extends at least from 1.25 to 4.8 μm, and strong emission features at 3.3 and 3.4μm. (author)

  14. Magnetic fields and star formation: evidence from imaging polarimetry of the Serpens Reflection Nebula

    Warren-Smith, R F; Draper, P W; Scarrott, S M

    1987-08-01

    CCD imaging of the Serpens bipolar reflection nebula shows it to be surrounded by dark material having spiral density structure. Multi-colour polarization mapping also reveals details of the surrounding magnetic field, indicating that this also has spiral structure. These observations are discussed along with current ideas about the role of magnetic fields during star formation. An interpretation involving the non-axisymmetric magnetically braked collapse of a protostellar cloud is proposed and a resulting magnetic field configuration is described which can account for the observations. Evidence is also discussed for the formation of a binary star system within the nebula, resulting from the fragmentation of a magnetized protostellar disc.

  15. Quenched carbonaceous composite - Fluorescence spectrum compared to the extended red emission observed in reflection nebulae

    Sakata, Akira; Wada, Setsuko; Narisawa, Takatoshi; Asano, Yoichi; Iijima, Yutaka; Onaka, Takashi; Tokunaga, Alan T.

    1992-01-01

    The photoluminescence (fluorescence) of a film of the laboratory-synthesized quenched carbonaceous composite (filmy QCC) is shown to have a single broad emission feature with a peak wavelength that varies from 670 to 725 nm, and coincides with that of the extended red emission observed in reflection nebulae. The rapid decay of the filmy QCC red fluorescence in air and of the stable blue fluorescence of the filmy QCC dissolved in liquid Freon suggests that the red fluorescence originates from the interaction of active chemical species and aromatic components in the filmy QCC. A material similar in nature to that of the filmy QCC may be a major component of interstellar dust.

  16. Observations of the 18-cm OH lines in Herbig--Haro objects and reflection nebulae

    Pashchenko, M.I.; Rudnitskii, G.M.

    1980-01-01

    In 1978 various Herbig--Haro objects and R-associations (containing reflection nebulae) were observed in the principal (1665, 1667 MHz) lines of the ground state of the hydroxyl molecule with the large radio telescope of the Station Radioastronomique de Nancay. OH emission was detected near 36 of the 63 objects examined. In most cases the line profiles have a simple, single-peaked structure, with a line width of 1--3 km/sec. The OH emission probably originates in interstellar dust clouds surrounding the HH objects and R-associations. Some implications of these results are discussed briefly

  17. Interpretation of a Variable Reflection Nebula Associated with HBC 340 and HBC 341 in NGC 1333

    Dahm, S. E. [U.S. Naval Observatory, Flagstaff Station, 10391 West Naval Observatory Road, Flagstaff, AZ 86005-8521 (United States); Hillenbrand, L. A. [Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States)

    2017-11-01

    We present multi-epoch, R -band imaging obtained from the Palomar Transient Factory of a small, fan-shaped reflection nebula in NGC 1333 that experiences prominent brightness fluctuations. Photometry of HBC 340 (K7e) and HBC 341 (M5e), a visual pair of late-type, young stellar objects lying near the apex of the nebula, demonstrates that while both are variable, the former has brightened by more than two magnitudes following a deep local minimum in 2014 September. Keck high-dispersion ( R  ∼ 45,000–66,000), optical spectroscopy of HBC 340 suggests that the protostar is a spectroscopic binary (HBC 340Aa + HBC 340Ab). Both HBC 340 and HBC 341 exhibit strong H α and forbidden line emission, consistent with accretion and outflow. We conclude that the brightness fluctuations in the reflection nebula represent light echos produced by varying incident radiation emanating from HBC 340. The short-term variability observed in the protostar is attributed to irregular accretion activity, while correlated, dipping behavior on a several hundred day timescale may be due to eclipse-like events caused by orbiting circumstellar material. Archival Hubble Space Telescope imaging of the region reveals a second, faint (F814W ∼ 20.3 mag) companion to HBC 340 that lies 1.″02 (∼235 au) east of the protostar. If associated, this probable substellar mass object (20–50 Jupiter masses), HBC 340B, is likely unrelated to the observed brightness variations. The sustained brightening of HBC 340 since late 2014 can be explained by an EXor-like outburst, the recovery from a long duration eclipse event caused by obscuring circumstellar dust, or by the gradual removal of extincting material from along the line of sight. Our analysis here favors one of the extinction scenarios.

  18. Interpretation of a Variable Reflection Nebula Associated with HBC 340 and HBC 341 in NGC 1333

    Dahm, S. E.; Hillenbrand, L. A.

    2017-01-01

    We present multi-epoch, R -band imaging obtained from the Palomar Transient Factory of a small, fan-shaped reflection nebula in NGC 1333 that experiences prominent brightness fluctuations. Photometry of HBC 340 (K7e) and HBC 341 (M5e), a visual pair of late-type, young stellar objects lying near the apex of the nebula, demonstrates that while both are variable, the former has brightened by more than two magnitudes following a deep local minimum in 2014 September. Keck high-dispersion ( R  ∼ 45,000–66,000), optical spectroscopy of HBC 340 suggests that the protostar is a spectroscopic binary (HBC 340Aa + HBC 340Ab). Both HBC 340 and HBC 341 exhibit strong H α and forbidden line emission, consistent with accretion and outflow. We conclude that the brightness fluctuations in the reflection nebula represent light echos produced by varying incident radiation emanating from HBC 340. The short-term variability observed in the protostar is attributed to irregular accretion activity, while correlated, dipping behavior on a several hundred day timescale may be due to eclipse-like events caused by orbiting circumstellar material. Archival Hubble Space Telescope imaging of the region reveals a second, faint (F814W ∼ 20.3 mag) companion to HBC 340 that lies 1.″02 (∼235 au) east of the protostar. If associated, this probable substellar mass object (20–50 Jupiter masses), HBC 340B, is likely unrelated to the observed brightness variations. The sustained brightening of HBC 340 since late 2014 can be explained by an EXor-like outburst, the recovery from a long duration eclipse event caused by obscuring circumstellar dust, or by the gradual removal of extincting material from along the line of sight. Our analysis here favors one of the extinction scenarios.

  19. CO, CS, and HCN in a clustering of reflection nebulae in Monoceros

    Kutner, M.L.; Tucker, K.D.

    1975-01-01

    Carbon monoxide line emission at lambda=2.6 mm has been observed over an area of approx.3 1/2degreetimes3 1/2degree in L1646, a diffuse dust cloud containing a grouping of reflection nebulae. The H 2 mass is estimated from the CO observations to be >3.2times10 4 M/sub sun/. Five CO emission peaks are observed, each apparently associated with at least one reflection nebula, with the strongest peak at α (1950) =6)05)20), delta (1950) =-6degree22'30''. Around this position, extended (10'times10') emission is observed from HCN and CS, suggesting a core with H 2 density approximately-less-than8times10 4 cm -3 . This core appears to be rotating with Ωgreater than or equal to7.4times10 -14 s -1 . There is also evidence for self-absorption in the CO line in this direction, suggestive of a collapsing cloud. (auth)

  20. Infrared images of reflection nebulae and Orion's bar: Fluorescent molecular hydrogen and the 3.3 micron feature

    Burton, M.G.; Moorhouse, A.; Brand, P.W.J.L.; Roche, P.F.; Geballe, T.R.

    1989-01-01

    Images were obtained of the (fluorescent) molecular hydrogen 1-0 S(1) line, and of the 3.3 micron emission feature, in Orion's Bar and three reflection nebulae. The emission from these species appears to come from the same spatial locations in all sources observed. This suggests that the 3.3 micron feature is excited by the same energetic UV-photons which cause the molecular hydrogen to fluoresce

  1. Ultraviolet Imaging Telescope images of the reflection nebula NGC 7023 - Derivation of ultraviolet scattering properties of dust grains

    Witt, Adolf N.; Petersohn, Jens K.; Bohlin, Ralph C.; O'Connell, Robert W.; Roberts, Morton S.; Smith, Andrew M.; Stecher, Theodore P.

    1992-01-01

    The Ultraviolet Imaging Telescope as part of the Astro-1 mission, was used to obtain high-resolution surface brightness distribution data in six ultraviolet wavelength bands for the bright reflection nebula NGC 7023. From the quantitative comparison of the measured surface brightness gradients ratios of nebular to stellar flux, and detail radial surface brightness profiles with corresponding data from the visible, two major conclusions results: (1) the scattering in the near- and far-ultraviolet in this nebula is more strongly forward-directed than in the visible; (2) the dust albedo in the ultraviolet for wavelengths not less than 140 nm is identical to that in the visible, with the exception of the 220 nm bump in the extinction curve. In the wavelengths region of the bump, the albedo is reduced by 25 to 30 percent in comparison with wavelengths regions both shorter and longer. This lower albedo is expected, if the bump is a pure absorption feature.

  2. THE CHARGE STATE OF POLYCYCLIC AROMATIC HYDROCARBONS ACROSS REFLECTION NEBULAE: PAH CHARGE BALANCE AND CALIBRATION

    Boersma, C.; Bregman, J.; Allamandola, L. J.

    2016-01-01

    Low-resolution Spitzer spectral map data (>1700 spectra) of ten reflection nebulae (RNe) fields are analyzed using the data and tools available through the NASA Ames PAH IR Spectroscopic Database. The PAH emission is broken down into PAH charge state using a database fitting approach. Here, the physics of the PAH emission process is taken into account and uses target appropriate parameters, e.g., a stellar radiation model for the exciting star. The breakdown results are combined with results derived using the traditional PAH band strength approach, which interprets particular PAH band strength ratios as proxies for the PAH charge state, e.g., the 6.2/11.2 μ m PAH band strength ratio. These are successfully calibrated against their database equivalent; the PAH ionized fraction ( f i ). The PAH ionized fraction is converted into the PAH ionization parameter, which relates the PAH ionized fraction to the strength of the radiation field, gas temperature and electron density. The behavior of the 12.7 μ m PAH band is evaluated as a tracer for PAH ionization and erosion. The plot of the 8.6 versus 11.2 μ m PAH band strength for the northwest photo-dominated region (PDR) in NGC 7023 is shown to be a robust diagnostic template for the PAH ionized fraction. Remarkably, most of the other RNe fall within the limits set by NGC 7023. Finally, PAH spectroscopic templates are constructed and verified as principal components. Template spectra derived from NGC 7023 and NGC 2023 compare extremely well with each other, with those derived for NGC 7023 successfully reproducing the PAH emission observed from NGC 2023.

  3. THE CHARGE STATE OF POLYCYCLIC AROMATIC HYDROCARBONS ACROSS REFLECTION NEBULAE: PAH CHARGE BALANCE AND CALIBRATION

    Boersma, C.; Bregman, J.; Allamandola, L. J., E-mail: Christiaan.Boersma@nasa.gov [NASA Ames Research Center, MS 245-6, Moffett Field, CA 94035-0001 (United States)

    2016-11-20

    Low-resolution Spitzer spectral map data (>1700 spectra) of ten reflection nebulae (RNe) fields are analyzed using the data and tools available through the NASA Ames PAH IR Spectroscopic Database. The PAH emission is broken down into PAH charge state using a database fitting approach. Here, the physics of the PAH emission process is taken into account and uses target appropriate parameters, e.g., a stellar radiation model for the exciting star. The breakdown results are combined with results derived using the traditional PAH band strength approach, which interprets particular PAH band strength ratios as proxies for the PAH charge state, e.g., the 6.2/11.2 μ m PAH band strength ratio. These are successfully calibrated against their database equivalent; the PAH ionized fraction ( f {sub i} ). The PAH ionized fraction is converted into the PAH ionization parameter, which relates the PAH ionized fraction to the strength of the radiation field, gas temperature and electron density. The behavior of the 12.7 μ m PAH band is evaluated as a tracer for PAH ionization and erosion. The plot of the 8.6 versus 11.2 μ m PAH band strength for the northwest photo-dominated region (PDR) in NGC 7023 is shown to be a robust diagnostic template for the PAH ionized fraction. Remarkably, most of the other RNe fall within the limits set by NGC 7023. Finally, PAH spectroscopic templates are constructed and verified as principal components. Template spectra derived from NGC 7023 and NGC 2023 compare extremely well with each other, with those derived for NGC 7023 successfully reproducing the PAH emission observed from NGC 2023.

  4. Fluorescent H{sub 2} Emission Lines from the Reflection Nebula NGC 7023 Observed with IGRINS

    Le, Huynh Anh N.; Pak, Soojong; Lee, Hye-In [School of Space Research, Kyung Hee University, 1732 Deogyeong-daero, Giheung-gu, Yongin-si, Gyeonggi-do 17104 (Korea, Republic of); Kaplan, Kyle; Mace, Gregory; Pavel, Michael; Jaffe, Daniel T. [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States); Lee, Sungho; Jeong, Ueejeong; Chun, Moo-Young; Yuk, In-Soo; Hwang, Narae; Kim, Kang-Min; Park, Chan; Oh, Jae Sok; Yu, Young Sam; Park, Byeong-Gon; Minh, Young Chol [Korea Astronomy and Space Science Institute, Daejeon 34055 (Korea, Republic of); Oh, Heeyoung [Department of Physics and Astronomy, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul 08826 (Korea, Republic of); Pyo, Tae-Soo, E-mail: huynhanh7@khu.ac.kr, E-mail: soojong@khu.ac.kr [Subaru Telescope, National Astronomical Observatory of Japan, National Institutes of Natural Sciences (NINS), 650 North Aohoku Place, Hilo, HI 96720 (United States)

    2017-05-20

    We have analyzed the temperature, velocity, and density of H{sub 2} gas in NGC 7023 with a high-resolution near-infrared spectrum of the northwestern filament of the reflection nebula. By observing NGC 7023 in the H and K bands at R ≃ 45,000 with the Immersion GRating INfrared Spectrograph, we detected 68 H{sub 2} emission lines within the 1″ × 15″ slit. The diagnostic ratio of 2-1 S(1)/1-0 S(1) is 0.41−0.56. In addition, the estimated ortho-to-para ratio (OPR) is 1.63−1.82, indicating that the H{sub 2} emission transitions in the observed region arise mostly from gas excited by UV fluorescence. Gradients in the temperature, velocity, and OPR within the observed area imply motion of the photodissociation region (PDR) relative to the molecular cloud. In addition, we derive the column density of H{sub 2} from the observed emission lines and compare these results with PDR models in the literature covering a range of densities and incident UV field intensities. The notable difference between PDR model predictions and the observed data, in high rotational J levels of ν = 1, is that the predicted formation temperature for newly formed H{sub 2} should be lower than that of the model predictions. To investigate the density distribution, we combine pixels in 1″ × 1″ areas and derive the density distribution at the 0.002 pc scale. The derived gradient of density suggests that NGC 7023 has a clumpy structure, including a high clump density of ∼10{sup 5} cm{sup −3} with a size smaller than ∼5 × 10{sup −3} pc embedded in lower-density regions of 10{sup 3}–10{sup 4} cm{sup −3}.

  5. THE 15–20 μm EMISSION IN THE REFLECTION NEBULA NGC 2023

    Peeters, Els; Tielens, Alexander G. G. M.; Allamandola, Louis J.; Wolfire, Mark G.

    2012-01-01

    We present 15-20 μm spectral maps toward the reflection nebula NGC 2023 obtained with the Infrared Spectrograph in short-wavelength, high-resolution mode on board the Spitzer Space Telescope. These spectra reveal emission from polycyclic aromatic hydrocarbons (PAHs), C 60 , and H 2 superposed on a dust continuum. These emission components exhibit distinct spatial distributions: with increasing distance from the illuminating star, we observe the PAH emission followed by the dust continuum emission and the H 2 emission. The C 60 emission is located closest to the illuminating star in the south, while in the north it seems to be associated with the H/H 2 transition. Emission from PAHs and PAH-related species produces features at 15.8, 16.4, 17.4, and 17.8 μm and the 15-18 μm plateau. These different PAH features show distinct spatial distributions. The 15.8 μm band and 15-18 μm plateau correlate with the 11.2 μm PAH band and with each other, and are attributed to large, neutral PAHs. Conversely, the 16.4 μm feature correlates with the 12.7 μm PAH band, suggesting that both arise from species that are favored by the same conditions that favor PAH cations. The PAH contribution to the 17.4 μm band is displaced toward the illuminating star with respect to the 11.2 and 12.7 μm emission and is assigned to doubly ionized PAHs and/or a subset of cationic PAHs. The spatial distribution of the 17.8 μm band suggests that it arises from both neutral and cationic PAHs. In contrast to their intensities, the profiles of the PAH bands and the 15-18 μm plateau do not vary spatially. Consequently, we conclude that the carrier of the 15-18 μm plateau is distinct from that of the PAH bands.

  6. Infrared nebula in the Chamaeleon T association

    Schwartz, R.D.; Henize, K.G.

    1983-01-01

    Data are tabulated for seven nebulae in the Chamaeleon T association. Three, which are large and clearly related to illuminating stars, appear to be typical reflection nebulae. Three are small wisps attached to stars and are probably cometary-type reflection nebulae. The remaining nebula is a triangular wisp having an unusually red spectral energy distribution and showing no illuminating star on visual wavelength photographs. The western tip of this nebula coincides closely with the position of a recently reported infrared source. The nebula is probably one lobe of a bipolar nebula

  7. DETECTION OF ANOMALOUS MICROWAVE EMISSION IN THE PLEIADES REFLECTION NEBULA WITH WILKINSON MICROWAVE ANISOTROPY PROBE AND THE COSMOSOMAS EXPERIMENT

    Genova-Santos, R.; Rebolo, R.; Rubino-Martin, J. A.; Lopez-Caraballo, C. H.; Hildebrandt, S. R. [Instituto de Astrofisica de Canarias, C/Via Lactea s/n, E-38200 La Laguna, Tenerife (Spain)

    2011-12-10

    We present evidence for anomalous microwave emission (AME) in the Pleiades reflection nebula, using data from the seven-year release of the Wilkinson Microwave Anisotropy Probe and from the COSMOSOMAS (Cosmological Structures on Medium Angular Scales) experiment. The flux integrated in a 1 Degree-Sign radius around R.A. = 56.{sup 0}24, decl. = 23.{sup 0}78 (J2000) is 2.15 {+-} 0.12 Jy at 22.8 GHz, where AME is dominant. COSMOSOMAS data show no significant emission, but allow one to set upper limits of 0.94 and 1.58 Jy (99.7% confidence level), respectively, at 10.9 and 14.7 GHz, which are crucial to pin down the AME spectrum at these frequencies, and to discard any other emission mechanisms which could have an important contribution to the signal detected at 22.8 GHz. We estimate the expected level of free-free emission from an extinction-corrected H{alpha} template, while the thermal dust emission is characterized from infrared DIRBE data and extrapolated to microwave frequencies. When we deduct the contribution from these two components at 22.8 GHz, the residual flux, associated with AME, is 2.12 {+-} 0.12 Jy (17.7{sigma}). The spectral energy distribution from 10 to 60 GHz can be accurately fitted with a model of electric dipole emission from small spinning dust grains distributed in two separated phases of molecular and atomic gas, respectively. The dust emissivity, calculated by correlating the 22.8 GHz data with 100 {mu}m data, is found to be 4.36 {+-} 0.17 {mu}K (MJy sr{sup -1}){sup -1}, a value considerably lower than in typical AME clouds, which present emissivities of {approx}20 {mu}K (MJy sr{sup -1}){sup -1}, although higher than the 0.2 {mu}K (MJy sr{sup -1}){sup -1} of the translucent cloud LDN 1780, where AME has recently been claimed. The physical properties of the Pleiades nebula, in particular its low extinction A{sub V} {approx} 0.4, indicate that this is indeed a much less opaque object than those where AME has usually been studied. This fact

  8. DETECTION OF ANOMALOUS MICROWAVE EMISSION IN THE PLEIADES REFLECTION NEBULA WITH WILKINSON MICROWAVE ANISOTROPY PROBE AND THE COSMOSOMAS EXPERIMENT

    Génova-Santos, R.; Rebolo, R.; Rubiño-Martín, J. A.; López-Caraballo, C. H.; Hildebrandt, S. R.

    2011-01-01

    We present evidence for anomalous microwave emission (AME) in the Pleiades reflection nebula, using data from the seven-year release of the Wilkinson Microwave Anisotropy Probe and from the COSMOSOMAS (Cosmological Structures on Medium Angular Scales) experiment. The flux integrated in a 1° radius around R.A. = 56. 0 24, decl. = 23. 0 78 (J2000) is 2.15 ± 0.12 Jy at 22.8 GHz, where AME is dominant. COSMOSOMAS data show no significant emission, but allow one to set upper limits of 0.94 and 1.58 Jy (99.7% confidence level), respectively, at 10.9 and 14.7 GHz, which are crucial to pin down the AME spectrum at these frequencies, and to discard any other emission mechanisms which could have an important contribution to the signal detected at 22.8 GHz. We estimate the expected level of free-free emission from an extinction-corrected Hα template, while the thermal dust emission is characterized from infrared DIRBE data and extrapolated to microwave frequencies. When we deduct the contribution from these two components at 22.8 GHz, the residual flux, associated with AME, is 2.12 ± 0.12 Jy (17.7σ). The spectral energy distribution from 10 to 60 GHz can be accurately fitted with a model of electric dipole emission from small spinning dust grains distributed in two separated phases of molecular and atomic gas, respectively. The dust emissivity, calculated by correlating the 22.8 GHz data with 100 μm data, is found to be 4.36 ± 0.17 μK (MJy sr –1 ) –1 , a value considerably lower than in typical AME clouds, which present emissivities of ∼20 μK (MJy sr –1 ) –1 , although higher than the 0.2 μK (MJy sr –1 ) –1 of the translucent cloud LDN 1780, where AME has recently been claimed. The physical properties of the Pleiades nebula, in particular its low extinction A V ∼ 0.4, indicate that this is indeed a much less opaque object than those where AME has usually been studied. This fact, together with the broad knowledge of the stellar content of this region

  9. Planetary nebulae

    Amnuehl', P.R.

    1985-01-01

    The history of planetary nebulae discovery and their origin and evolution studies is discussed in a popular way. The problem of planetary nebulae central star is considered. The connection between the white-draft star and the planetary nebulae formulation is shown. The experimental data available acknowledge the hypothesis of red giant - planetary nebula nucleus - white-draft star transition process. Masses of planetary nebulae white-draft stars and central stars are distributed practically similarly: the medium mass is close to 0.6Msub(Sun) (Msub(Sun) - is the mass of the Sun)

  10. Gaseous nebulae

    Williams, R.E.

    1976-01-01

    Gaseous nebulae are large, tenuous clouds of ionized gas that are associated with hot stars and that emit visible light because of the energy that they receive from the ultraviolet radiation of the stars. Examples include H II regions, planetary nebulae, and nova/supernova remnants. The emphasis is on the physical processes that occur in gaseous nebulae as opposed to a study of the objects themselves. The introduction discusses thermodynamic vs. steady-state equilibrium and excitation conditions in a dilute radiation field. Subsequent sections take up important atomic processes in gaseous nebulae (particle--particle collision rates, radiative interaction rates, cross sections), the ionization equilibrium (sizes of H II regions, ionization of the heavier elements), kinetic temperature and energy balance (heating of the electrons, cooling of the electrons), and the spectra of gaseous nebulae (line fluxes in nebulae). 7 figures, 5 tables

  11. Observing nebulae

    Griffiths, Martin

    2016-01-01

    This book enables anyone with suitable instruments to undertake an examination of nebulae and see or photograph them in detail. Nebulae, ethereal clouds of gas and dust, are among the most beautiful objects to view in the night sky. These star-forming regions are a common target for observers and photographers. Griffiths describes many of the brightest and best nebulae and includes some challenges for the more experienced observer. Readers learn the many interesting astrophysical properties of these clouds, which are an important subject of study in astronomy and astrobiology. Non-mathematical in approach, the text is easily accessible to anyone with an interest in the subject. A special feature is the inclusion of an observational guide to 70 objects personally observed or imaged by the author. The guide also includes photographs of each object for ease of identification along with their celestial coordinates, magnitudes and other pertinent information. Observing Nebulae provides a ready resource to allow an...

  12. POLYCYCLIC AROMATIC HYDROCARBONS WITH STRAIGHT EDGES AND THE 7.6/6.2 AND 8.6/6.2 INTENSITY RATIOS IN REFLECTION NEBULAE.

    Ricca, Alessandra; Bauschlicher, Charles W; Roser, Joseph E; Peeters, Els

    2018-01-01

    We have investigated the mid-infrared spectral characteristics of a series of polycyclic aromatic hydrocarbons (PAHs) with straight edges and containing an even or odd number of carbons using density functional theory (DFT). For several even and odd-carbon PAHs, the 8.6/6.2 and 7.6/6.2 intensity ratios computed in emission after the absorption of a 8 eV photon match the observed ratios obtained for three reflection nebulae (RNe), namely NGC 1333, NGC 7023, and NGC 2023. Odd-carbon PAHs are favored, particularly for NGC 1333. Both cations and anions are present with the cations being predominant. Relevant PAHs span sizes ranging from 46 to 103-113 carbons for NGC 7023 and NGC 2023 and from 38 to 127 carbons for NGC 1333 and have symmetries ranging from D 2 h to C s . Our work suggests that even and odd-carbon PAHs with straight edges are viable candidates for the PAH emission seen towards irradiated Photo-Dissociation Regions (PDRs).

  13. Polycyclic Aromatic Hydrocarbons with Straight Edges and the 7.6/6.2 and 8.6/6.2 Intensity Ratios in Reflection Nebulae

    Ricca, Alessandra; Bauschlicher, Charles W., Jr.; Roser, Joseph E.; Peeters, Els

    2018-02-01

    Using density functional theory, we have investigated the mid-infrared spectral characteristics of a series of polycyclic aromatic hydrocarbons (PAHs) that have straight edges and that contain an even or odd number of carbons. For several even and odd-carbon PAHs, the 8.6/6.2 and 7.6/6.2 intensity ratios computed in emission after the absorption of a 8 eV photon match the observed ratios obtained for three reflection nebulae (RNe), namely NGC 1333, NGC 7023, and NGC 2023. Odd-carbon PAHs are favored, particularly for NGC 1333. Both cations and anions are present, with the cations being predominant. Relevant PAHs span sizes ranging from 46 to 113 carbons for NGC 7023 and NGC 2023 and from 38 to 127 carbons for NGC 1333, and have symmetries ranging from D2h to C s . Our work suggests that even- and odd-carbon PAHs with straight edges are viable candidates for the PAH emission seen toward irradiated photodissociation regions.

  14. Shaping of planetary nebulae

    Balick, B.

    1987-01-01

    The phases of stellar evolution and the development of planetary nebulae are examined. The relation between planetary nebulae and red giants is studied. Spherical and nonspherical cases of shaping planetaries with stellar winds are described. CCD images of nebulae are analyzed, and it is determined that the shape of planetary nebulae depends on ionization levels. Consideration is given to calculating the distances of planetaries using radio images, and molecular hydrogen envelopes which support the wind-shaping model of planetary nebulae

  15. The Crab Nebula

    Mitton, S.

    1979-01-01

    The subject is covered in chapters, as follows: A.D.1054, a star explodes (historical account of observations of the supernova of which the Crab Nebula is the remnant); the telescope takes over (discovery and subsequent observation of the Crab Nebula); the message of the fiery remnant (detailed structure and its interpretation); the invisible nebula (electromagnetic radiation from the Crab Nebula and its interpretation); a beacon in the night (the discovery of pulsars, with special reference to the pulsar in the Crab Nebula; observation and theory); the strange world of a neutron star (theory, prediction and observation); magnetic fields and energy flow from the pulsar (stellar magnetosphere; luminosity of the nebula); how does the pulsar pulse (observation; models to explain beaming); outburst and aftermath (types of supernovae and their evolution; nucleosynthesis); supernovae and their remnants (account of observations since early records); the Crab Nebula and modern astronomy. (U.K.)

  16. Starlight excitation of permitted lines in gaseous nebulae

    Grandi, S.A.

    1975-01-01

    The weak heavy element permitted lines observed in the spectra of gaseous nebula have, with only a few exceptions, been thought to be excited only by recombination. The accuracy of this assumption for individual lines in nebula spectra is investigated in detail via model nebula calculations. First, approximations and techniques of calculation are considered for the three possible excitation mechanisms: recombination, resonance fluorescence by the starlight continuum, and resonance fluorescence by other nebular emission lines. Next, the permitted lines of O I as observed in gaseous nebulae are discussed. Thirdly, it is shown that varying combinations of recombination, resonance fluorescence by starlight, and resonance fluorescence by other nebula lines can successfully account for the observed strengths in the Orion Nebula of lines of the following ions: C II, N I, N II, N III, O II, Ne II, Si II, Si III, and S III. A similar analysis is performed for the lines in the spectra of the planetary nebulae NGC7662 and NGC7027, and, with some exceptions, satisfactory agreement between the observed and predicted line strengths is found. Finally, observations of the far red spectra of the Orion Nebula, the planetary nebulae NGC3242, NGC6210, NGC2392, IC3568, IC4997, NGC7027, and MGC7662, and the reflection nebulae IC431 and NGC2068 are reported

  17. Dust in planetary nebulae

    Kwok, S.

    1980-01-01

    A two-component dust model is suggested to explain the infrared emission from planetary nebulae. A cold dust component located in the extensive remnant of the red-giant envelope exterior to the visible nebula is responsible for the far-infrared emission. A ward dust component, which is condensed after the formation of the planetary nebula and confined within the ionized gas shell, emits most of the near- and mid-infrared radiation. The observations of NGC 7027 are shown to be consisten with such a model. The correlation of silicate emission in several planetary nebulae with an approximately +1 spectral index at low radio frequencies suggests that both the silicate and radio emissions originate from the remnant of the circumstellar envelope of th precursor star and are observable only while the planetary nebula is young. It is argued that oxygen-rich stars as well as carbon-rich stars can be progenitors of planetary nebulae

  18. Dust in planetary nebulae

    Mathis, J.S.

    1978-01-01

    The author's review concentrates on theoretical aspects of dust in planetary nebulae (PN). He considers the questions: how much dust is there is PN; what is its composition; what effects does it have on the ionization structure, on the dynamics of the nebula. (Auth.)

  19. Nebulae and interstellar matter

    1987-01-01

    The South African Astronomical Observatory (SAAO) has investigated the IRAS source 1912+172. This source appears to be a young planetary nebula with a binary central star. During 1986 SAAO has also studied the following: hydrogen deficient planetary nebulae; high speed flows in HII regions, and the wavelength dependence of interstellar polarization. 2 figs

  20. Proto-planetary nebulae

    Zuckerman, B.

    1978-01-01

    A 'proto-planetary nebula' or a 'planetary nebula progenitor' is the term used to describe those objects that are losing mass at a rate >approximately 10 -5 Msolar masses/year (i.e. comparable to mass loss rates in planetary nebulae with ionized masses >approximately 0.2 Msolar masses) and which, it is believed, will become planetary nebulae themselves within 5 years. It is shown that most proto-planetary nebulae appear as very red objects although a few have been 'caught' near the middle of the Hertzsprung-Russell diagram. The precursors of these proto-planetaries are the general red giant population, more specifically probably Mira and semi-regular variables. (Auth.)end

  1. Bipolar nebulae and type I planetary nebulae

    Calvet, N.; Peimbert, M.

    1983-01-01

    It is suggested that the bipolar nature of PN of type I can be explained in terms of their relatively massive progenitors (Msub(i) 2.4 Msub(o)), that had to lose an appreciable fraction of their mass and angular momentum during their planetary nebulae stage. The following objects are discussed in relation with this suggestion: NGC 6302, NGC 2346, NGC 2440, CRL 618, Mz-3 and M2-9. It is found that CRL 618 is overbundant in N/O by a factor of 5-10 relative to the Orion Nebula. (author)

  2. Charge transfer in astrophysical nebulae

    Shields, G.A.

    1990-01-01

    Charge transfer has become a standard ingredient in models of ionized nebulae, supernovae remnants and active galactic nuclei. Charge transfer rate coefficients and the physics of ionized nebulae are considered. Charge transfer is applied to the ionization structure and line emission of ionized nebulae. Photoionized nebulae observations are used to test theoretical predictions of charge transfer rates. (author)

  3. Wolf-Rayet nebulae

    Chu, You-Hua

    2016-01-01

    Since the discovery of nebulae around Wolf-Rayet (WR) stars in the 1960s, it has been established that WR stars are massive stars at advanced evolutionary stages and that their surrounding nebulae result from the interactions between the stellar mass loss and the ambient interstellar medium. Surveys of WR nebulae have been made in the Galaxy, Magellanic Clouds, and other nearby galaxies in the Local Group. Some WR nebulae exhibit He II λ4686 line emission, indicating stellar effective temperatures of 90 — 100 x 10 3 K. The shocked fast stellar winds from WR nebulae have been detected in soft X-rays, but theoretical models have not been able to reproduce the observed X-ray spectral properties. Elemental abundances of WR nebulae consisting of synthesized stellar material can constrain stellar evolution models, but high-dispersion spectra are needed to kinematically separate the expanding shell of a WR nebula and the background interstellar medium for accurate abundance analyses. (paper)

  4. A Shocking Solar Nebula?

    Liffman, Kurt

    2009-01-01

    It has been suggested that shock waves in the solar nebula formed the high temperature materials observed in meteorites and comets. It is shown that the temperatures at the inner rim of the solar nebula could have been high enough over a sufficient length of time to produce chondrules, CAIs, refractory dust grains and other high-temperature materials observed in comets and meteorites. The solar bipolar jet flow may have produced an enrichment of 16O in the solar nebula over time and the chond...

  5. Structure of planetary nebulae

    Goad, L.E.

    1975-01-01

    Image-tube photographs of planetary nebulae taken through narrow-band interference filters are used to map the surface brightness of these nebulae in their most prominent emission lines. These observations are best understood in terms of a two-component model consisting of a tenuous diffuse nebular medium and a network of dense knots and filaments with neutral cores. The observations of the diffuse component indicate that the inner regions of these nebulae are hollow shells. This suggests that steady stellar winds are the dominant factor in determining the structure of the central regions of planetary nebulae. The observations of the filamentary components of NGC 40 and NGC 6720 show that the observed nebular features can result from the illumination of the inner edges of dense fragmentary neutral filaments by the central stars of these nebulae. From the analysis of the observations of the low-excitation lines in NGC 2392, it is concluded that the rate constant for the N + --H charge transfer reaction is less than 10 -12 cm 3 sec -1

  6. A Tactile Carina Nebula

    Grice, Noreen A.; Mutchler, M.

    2010-01-01

    Astronomy was once considered a science restricted to fully sighted participants. But in the past two decades, accessible books with large print/Braille and touchable pictures have brought astronomy and space science to the hands and mind's eye of students, regardless of their visual ability. A new universally-designed tactile image featuring the Hubble mosaic of the Carina Nebula is being presented at this conference. The original dataset was obtained with Hubble's Advanced Camera for Surveys (ACS) hydrogen-alpha filter in 2005. It became an instant icon after being infused with additional color information from ground-based CTIO data, and released as Hubble's 17th anniversary image. Our tactile Carina Nebula promotes multi-mode learning about the entire life-cycle of stars, which is dramatically illustrated in this Hubble mosaic. When combined with descriptive text in print and Braille, the visual and tactile components seamlessly reach both sighted and blind populations. Specific touchable features of the tactile image identify the shapes and orientations of objects in the Carina Nebula that include star-forming regions, jets, pillars, dark and light globules, star clusters, shocks/bubbles, the Keyhole Nebula, and stellar death (Eta Carinae). Visit our poster paper to touch the Carina Nebula!

  7. New and misclassified planetary nebulae

    Kohoutek, L.

    1978-01-01

    Since the 'Catalogue of Galactic Planetary Nebulae' 226 new objects have been classified as planetary nebulae. They are summarized in the form of designations, names, coordinates and the references to the discovery. Further 9 new objects have been added and called 'proto-planetary nebulae', but their status is still uncertain. Only 34 objects have been included in the present list of misclassified planetary nebulae although the number of doubtful cases is much larger. (Auth.)

  8. The filamentary nebulae S 188

    Rosado, M.; Kwitter, K.B.

    1982-01-01

    The crescent shaped nebula S 188 is identified as a planetary nebula (PN) of Peimbert's Type I on the basis of its observed nebula spectrum. New FP interferometric work allows to determine the systemic motion of this nebula. The derived kinematical distance exceeds Cudworth's distance estimate supporting the idea that Peimbert's Type I PNs have larger ejected masses than typical PNs. A discussion about the origin of its non-spherical shape is also given. (author)

  9. Modelling pulsar wind nebulae

    2017-01-01

    In view of the current and forthcoming observational data on pulsar wind nebulae, this book offers an assessment of the theoretical state of the art of modelling them. The expert authors also review the observational status of the field and provide an outlook for future developments. During the last few years, significant progress on the study of pulsar wind nebulae (PWNe) has been attained both from a theoretical and an observational perspective, perhaps focusing on the closest, more energetic, and best studied nebula: the Crab, which appears in the cover. Now, the number of TeV detected PWNe is similar to the number of characterized nebulae observed at other frequencies over decades of observations. And in just a few years, the Cherenkov Telescope Array will increase this number to several hundreds, actually providing an essentially complete account of TeV emitting PWNe in the Galaxy. At the other end of the multi-frequency spectrum, the SKA and its pathfinder instruments, will reveal thousands of new pulsa...

  10. Can planetary nebulae rotate

    Grinin, V.P.

    1982-01-01

    It is shown that the inclination of spectral lines observed in a number of planetary nebulae when the spectrograph slit is placed along the major axis, which is presently ascribed to nonuniform expansion of the shells, actually may be due to rotation of the nebulae about their minor axes, as Campbell and Moore have suggested in their reports. It is assumed that the rotation of the central star (or, if the core is a binary system, circular motions of gas along quasi-Keplerian orbits) serves as the source of the original rotation of a protoplanetary nebula. The mechanism providing for strengthening of the original rotation in the process of expansion of the shell is the tangential pressure of L/sub α/ radiation due to the anisotropic properties of the medium and radiation field. The dynamic effect produced by them is evidently greatest in the epoch when the optical depth of the nebula in the L/sub c/ continuum becomes on the order of unity in the course of its expansion

  11. Roberts 22: a bipolar nebula with OH emission

    Allen, D.A.; Hyland, A.R.; Caswell, J.L.

    1980-01-01

    Roberts 22 is a bipolar reflection nebula illuminated by a hidden A2 Ie star. Most of its energy is radiated at infrared wavelengths. It also shows strong OH maser emission (OH 284.18 - 0.79) on the 1612 and 1665 MHz transitions, generally similar to the masers associated with M stars having infrared excesses. But the system contains no late-type star. This remarkable assemblage of attributes makes Roberts 22 unique; however, it is probably a key member of the newly-recognized population of bipolar nebulae. From an analysis of the properties of Roberts 22 some published interpretations of other bipolar nebulae are questioned, in particular the derivation of spectral types for their underlying stars by the assumption of photo-ionization of the gas, and their evolutionary description as proto-planetary nebulae. (author)

  12. Models for the structure and origin of bipolar nebulae

    Morris, M.

    1981-01-01

    The appearance of bipolar nebulae-symmetric reflection nebulae centered on evolved, mass-losing stars-can most simply be accounted for in terms of an axisymmetric distribution of outflowing dust in which the dust is concentrated towards an equatorial plane and declines monotonically with latitude above that plane. The symmetrically placed ''horns'' that can be seen radiating out of some bipolar nebulae, notably GL 2688, are a natural consequence of such a dust distribution if, at some latitude, the radial optical depth to starlight falls rapidly below unity. Several models of bipolar nebulae are presented. These structural models for bipolar nebulae lead in turn to an investigation of how such a geometry might arise. Although nonradial pulsation, rotationally forced mass ejection by a single star, and mass loss from a common envelope binary are all considered, the most attractive origin for bipolar nebulae is a binary star system in which the primary is evolving up the red giant branch to the point at which its radius approaches its tidal radius. If this occurs before corotation of the primary with the secondary's orbit can be achieved, then matter from the primary's enveloped can be gravitationally ejected from the system by the secondary, the ejected material being concentrated toward the system's equatorial plane. Numerical models of this phenomenon show that gravitational ejection from an asynchronous binary system easily leads to terminal outflow velocities in the observed range (20--50 km s -1 ), and that the rate of mass loss and the time scale over which the mass ejection takes place are consistent with observations if the particle density in the outer layers of the primary's atmosphere from which the material is extracted is in the range 10 14 --10 15 cm -3 . If this hypothesis is applicable, bipolar nebulae will probably become planetary nebulae, as previously suggested on observational grounds

  13. Review of solar nebula models

    Wood, J.A.; Morfill, G.E.

    1988-01-01

    The major changes that have occurred in thinking about protosolar nebula models are discussed. The concept favored by astrophysicists for the last decade, that of a viscous accretion-disk nebula, is examined. The properties of recent accretion-disk models that are most relevant to chondrite-forming processes are noted. 27 references

  14. Ghost Head Nebula

    1999-01-01

    Looking like a colorful holiday card, a new image from NASA's Hubble Space Telescope reveals a vibrant green and red nebula far from Earth. The image of NGC 2080, taken by Hubble's Wide Field and Planetary Camera 2, designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif., is available online at http://www.jpl.nasa.gov/images/wfpc . Images like this help astronomers investigate star formation in nebulas. NGC 2080, nicknamed 'The Ghost Head Nebula,' is one of a chain of star-forming regions lying south of the 30 Doradus nebula in the Large Magellanic Cloud. 30 Doradus is the largest star-forming complex in the local group of galaxies. This 'enhanced color' picture is composed of three narrow-band-filter images obtained by Hubble on March 28, 2000. The red and blue light come from regions of hydrogen gas heated by nearby stars. The green light on the left comes from glowing oxygen. The energy to illuminate the green light is supplied by a powerful stellar wind, a stream of high-speed particles coming from a massive star just outside the image. The central white region is a combination of all three emissions and indicates a core of hot, massive stars in this star-formation region. Intense emission from these stars has carved a bowl-shaped cavity in surrounding gas. In the white region, the two bright areas (the 'eyes of the ghost') - named A1 (left) and A2 (right) -- are very hot, glowing 'blobs' of hydrogen and oxygen. The bubble in A1 is produced by the hot, intense radiation and powerful stellar wind from one massive star. A2 contains more dust and several hidden, massive stars. The massive stars in A1 and A2 must have formed within the last 10,000 years, since their natal gas shrouds are not yet disrupted by the powerful radiation of the newborn stars. The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract with the Goddard Space Flight Center, Greenbelt, Md. The

  15. The discovery of a highly polarized bipolar nebula

    Wolstencroft, R.D.; Scarrott, S.M.; Menzies, J.

    1989-01-01

    During a search for the optical counterparts of IRAS sources whose flux peaks at 25 microns, a small faint bipolar nebula was discovered in Monoceros at the position of IRAS 07131-0147. The CCD images display the object's considerable structure. The central star seems relatively free of closeby nebulosity: the two lobes have a bow-tie structure with those parts nearest to the star consisting of series of small knots. The outer parts of the lobes seem to be made up of filaments streaming away from knots. On the basis of its optical spectrum, the central star was classified as a M5-6 giant. In the IRAS color classification scheme of Van der Veen and Habing (1988), the central star is VIb which indicates that there are distinct hot and cold components of circumstellar dust and that the mass loss process may have temporarily abated. Therefore, it is proposed that the object is in the post main sequence stage of evolution and is a protoplanetary nebulae. Young protoplanetary nebulae have totally obscured central stars illuminating reflective lobes whereas older ones such as M2-9 have lobes seen in emission from gas ionized by the central hot star which is clearly visible. Since the central object of IRAS07131-0147 is a relatively unobscured late type star and the lobes are seen only by reflection, it is suggested that this nebula is a protoplanetary nebula in an evolutionary stage intermediate between that of CRL2688 and M2-9

  16. Reflections

    Joanne Embree

    2001-01-01

    Full Text Available Ideally, editorials are written one to two months before publication in the Journal. It was my turn to write this one. I had planned to write the first draft the evening after my clinic on Tuesday, September 11. It didn't get done that night or during the next week. Somehow, the topic that I had originally chosen just didn't seem that important anymore as I, along my friends and colleagues, reflected on the changes that the events of that day were likely to have on our lives.

  17. The carbon budget in the outer solar nebula.

    Simonelli, D P; Pollack, J B; McKay, C P; Reynolds, R T; Summers, A L

    1989-01-01

    Detailed models of the internal structures of Pluto and Charon, assuming rock and water ice as the only constituents, indicate that the mean silicate mass fraction of this two-body system is on the order of 0.7; thus the Pluto/Charon system is significantly "rockier" than the satellites of the giant planets (silicate mass fraction approximately 0.55). This compositional contrast reflects different formation mechanisms: it is likely that Pluto and Charon formed directly from the solar nebula, while the circumplanetary nebulae that produced the giant planet satellites were derived from envelopes that surrounded the forming giant planets (envelopes in which icy planetesimals dissolved more readily than rocky planetesimals). Simple cosmic abundance calculations, and the assumption that the Pluto/Charon system formed directly from solar nebula condensates, strongly suggest that the majority of the carbon in the outer solar nebula was in the form of carbon monoxide; these results are consistent with (1) inheritance from the dense molecular clouds in the interstellar medium (where CH4/CO nebula chemistry. Theoretical predictions of the C/H enhancements in the atmospheres of the giant planets, when compared to the actual observed enhancements, suggest that 10%, or slightly more, of the carbon in the outer solar nebula was in the form of condensed materials (although the amount of condensed C may have dropped slightly with increasing heliocentric distance). Strict compositional limits computed for the Pluto/Charon system using the densities of CH4 and CO ices indicate that these pure ices are at best minor components in the interiors of these bodies, and imply that CH4 and CO ices were not the dominant C-bearing solids in the outer nebula. Clathrate-hydrates could not have appropriated enough CH4 or CO to be the major form of condensed carbon, although such clathrates may be necessary to explain the presence of methane on Pluto after its formation from a CO-rich nebula

  18. Ring-shaped nebulae around FU Orionis stars

    Goodrich, R.W.

    1987-01-01

    Observational data on the morphology and spectra of the nebulae surrounding V1057 Cyg, V1515 Cyg, and V1735 Cyg stars are presented and studied. The data reveal that V1735 Cyg is more highly reddened than the nebula and the spectra of all three nebulae are from reflection. A simple model for the dust shell is proposed and it is argued that the shells may indicate a relatively advanced evolutionary state for the FU Orionis star. The relation between the shells and the evolution of the stars is examined. The models of Herbig (1977), Mould et al. (1978), Larson (1980), and Hartmann and Kenyon (1985), which are utilized to analyze the FU Orionis outburst phenomenon, are tested. 23 references

  19. A 'variable' stellar object in a variable blue nebula V-V 1-7

    Rao, N.K.; Gilra, D.P.

    1981-01-01

    V-V 1-7 is supposed to be one of the few planetary nebulae with Ao central stars and was included in the planetary-nebula catalogue as PK 235 + 1 0 1. The nebula was seen on the blue Palomar Observatory Sky Survey (POSS) print but not on the red print; as a result it was thought that it might be a reflection nebula. However, the symmetry of the nebula around the central star (HD 62001), and also the ultraviolet photometric variability of this central star led others to suggest that the nebula might be a nova shell. Subsequently it was found that the nebula V-V 1-7 has disappeared. It is not seen on any direct plate known to us except the POSS blue plate. In this paper the disappearance is reported (along with the nebula) of a stellar object, which appears within the 'nebular shell' of V-V 1-7 on the POSS blue plate, but not on the red plate. (author)

  20. The Toby Jug nebula (IC 2220): a bipolar and biconical nebula

    Perkins, H.G.; King, D.J.; Scarrott, S.M.

    1981-01-01

    An optical linear polarization map of IC 2220, the nebula surrounding the cool red giant HD 65750, is presented. The nebula appears to be bipolar and biconical in structure. The mass of the nebula is estimated to be 0.01 solar mass and is consistent with the nebula being formed from the current mass loss stage of the central star. (author)

  1. Red giants as precursors of planetary nebulae

    Renzini, A.

    1981-01-01

    It is generally accepted that Planetary Nebulae are produced by asymptotic giant-branch stars. Therefore, several properties of planetary nebulae are discussed in the framework of the current theory of stellar evolution. (Auth.)

  2. Number of planetary nebulae in our galaxy

    Alloin, D.; Cruz-Gonzalez, C.; Peimbert, M.

    1976-01-01

    It is found that the contribution to the ionization of the interstellar medium due to planetary nebulae is from one or two orders of magnitude smaller than that due to O stars. The mass return to the interstellar medium due to planetary nebulae is investigated, and the birth rate of white dwarfs and planetary nebulae are compared. Several arguments are given against the possibility that the infrared sources detected by Becklin and Neugebauer in the direction of the galactic center are planetary nebulae

  3. The Formation of a Planetary Nebula.

    Harpaz, Amos

    1991-01-01

    Proposes a scenario to describe the formation of a planetary nebula, a cloud of gas surrounding a very hot compact star. Describes the nature of a planetary nebula, the number observed to date in the Milky Way Galaxy, and the results of research on a specific nebula. (MDH)

  4. The Trifid Nebula: Stellar Sibling Rivalry

    2001-01-01

    A zoom into the Trifid Nebula starts with ground-based observations and ends with a Hubble Space Telescope (HST) image. Another HST image shows star formation in the nebula and the video concludes with a ground-based image of the Trifid Nebula.

  5. Reflected Glory

    2011-02-01

    The nebula Messier 78 takes centre stage in this image taken with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile, while the stars powering the bright display take a backseat. The brilliant starlight ricochets off dust particles in the nebula, illuminating it with scattered blue light. Igor Chekalin was the overall winner of ESO's Hidden Treasures 2010 astrophotography competition with his image of this stunning object. Messier 78 is a fine example of a reflection nebula. The ultraviolet radiation from the stars that illuminate it is not intense enough to ionise the gas to make it glow - its dust particles simply reflect the starlight that falls on them. Despite this, Messier 78 can easily be observed with a small telescope, being one of the brightest reflection nebulae in the sky. It lies about 1350 light-years away in the constellation of Orion (The Hunter) and can be found northeast of the easternmost star of Orion's belt. This new image of Messier 78 from the MPG/ESO 2.2-metre telescope at the La Silla Observatory is based on data selected by Igor Chekalin in his winning entry to the Hidden Treasures competition [1]. The pale blue tint seen in the nebula in this picture is an accurate representation of its dominant colour. Blue hues are commonly seen in reflection nebulae because of the way the starlight is scattered by the tiny dust particles that they contain: the shorter wavelength of blue light is scattered more efficiently than the longer wavelength red light. This image contains many other striking features apart from the glowing nebula. A thick band of obscuring dust stretches across the image from the upper left to the lower right, blocking the light from background stars. In the bottom right corner, many curious pink structures are also visible, which are created by jets of material being ejected from stars that have recently formed and are still buried deep in dust clouds. Two bright stars, HD 38563A and

  6. Kinematics of galactic planetary nebulae

    Kiosa, M.I.; Khromov, G.S.

    1979-01-01

    The classical method of determining the components of the solar motion relative to the centroid of the system of planetary nebulae with known radial velocities is investigated. It is shown that this method is insensitive to random errors in the radial velocities and that low accuracy in determining the coordinates of the solar apex and motion results from the insufficient number of planetaries with measured radial velocities. The planetary nebulae are found not to satisfy well the law of differential galactic rotation with circular orbits. This is attributed to the elongation of their galactic orbits. A method for obtaining the statistical parallax of planetary nebulae is considered, and the parallax calculated from the tau components of their proper motion is shown to be the most reliable

  7. Contraction of the solar nebula

    Rawal, J.J.

    1984-01-01

    The concept of Roche limit is applied to the Laplacian theory of the origin of the solar system to study the contraction of a spherical gas cloud (solar nebula). In the process of contraction of the solar nebula, it is assumed that the phenomenon of supersonic turbulent convection is operative and brings about the halt at various stages of contraction. It is found that the radius of the contracting solar nebula follows the Titius-Bode law. The consequences of the relation are also discussed. The aim is to attempt to explain, on the basis of the concept of Roche limit, the distribution of planets in the solar system and try to understand the physics underlying it. (Auth.)

  8. Ultraviolet spectra of planetary nebulae

    Adams, S.; Seaton, M.J.

    1982-01-01

    Features observed in infrared spectra suggest that certain very low excitation (VLE) nebulae have low C/O abundance ratios (Cohen and Barlow 1980; Aitken and Roche 1982). Fluxes in the multiplets [O II] lambda 2470 and C II] lambda 2326 have been measured for the VLE nebula He He 2-131 = HD 138403 using IUE high-dispersion spectra. An analysis similar to that of Harrington et al. (1980) for IC 418 gives C/O = 0.3 for He 2-131, compared with C/O = 1.3 for IC 418 and 0.6 for the Sun. (author)

  9. Circumnebular neutral hydrogen in planetary nebulae

    Taylor, A.R.; Gussie, G.T.; Pottasch, S.R.

    1990-01-01

    Centimeter line observations of six compact planetary nebulae are reported. Circumnebular atomic hydrogen absorption has been observed in NGC 6790, NGC 6886, IC 418, IC 5117, and BD +30 deg 3639, while H I was not observed to a high upper limit in NGC 6741. Hydrogen was also detected in emission from BD +30 deg 3639. The expansion velocities of the circumnebular envelopes are similar to the expansion velocities observed for the ionized nebula. The optical depth of circumnebular H I appears to decrease with increasing linear radius of the ionized nebulae, indicating that these nebulae are ionization bounded and that the amount of atomic hydrogen decreases as young nebulas evolve. 28 refs

  10. Ultraviolet spectroscopy of planetary nebulae in the Magellanic Clouds

    Maran, S.P.; Aller, L.H.; Gull, T.R.; Stecher, T.P.

    1982-01-01

    Ultraviolet spectra of three high excitation planetary nebulae in the Magellanic Clouds (LMC P40, SMC N2, SMC N5) were obtained with the International Ultraviolet Explorer. The results are analyzed together with new visual wavelength spectrophotometry of LMC P40 and published data on SMC N2 and SMC N5 to investigate chemical composition and in particular to make the first reliable estimates of the carbon abundance in extragalactic planetary nebulae. Although carbon is at most only slightly less abundant in the LMC and SMC planetary nebulae than in galactic planetaries, it is almost 40 times more abundant in the SMC planetaries than in the SMC interstellar medium, and is about 6 times more abundant in the LMC planetary than in the LMC interstellar medium. According to our limited sample, the net result of carbon synthesis and convective dredgeup in the progenitors of planetary nebulae, as reflected in the nebular carbon abundance, is roughly the same in the Galaxy, the LMC, and the SMC

  11. From red giants to planetary nebulae

    Kwok, S.

    1982-01-01

    The transition from red giants to planetary nebulae is studied by comparing the spectral characteristics of red giant envelopes and planetary nebulae. Observational and theoretical evidence both suggest that remnants of red giant envelopes may still be present in planetary nebula systems and should have significant effects on their formation. The dynamical effects of the interaction of stellar winds from central stars of planetary nebulae with the remnant red giant envelopes are evaluated and the mechanism found to be capable of producing the observed masses and momenta of planetary nebulae. The observed mass-radii relation of planetary nebulae may also be best explained by the interacting winds model. The possibility that red giant mass loss, and therefore the production of planetary nebulae, is different between Population I and II systems is also discussed

  12. WR stars with ring nebulae

    Tutukov, A.

    1982-01-01

    It is shown that most of usually apparently single nitrogen WR stars with ring emission nebulae around them (WN + Neb) are a probable product of the evolution of a massive close binary with initial masses of components exceeding approximately 20 solar masses. (Auth.)

  13. New infrared observations of IRS 1, IRS 3, and the adjacent nebula in the OMC-2 cluster

    Pendelton, Y.; Werner, M.; Dinerstein, H.

    1984-01-01

    Recent reports show that near infrared reflection nebulae are often observed around embedded protostellar objects. New observations are here reported of the infrared cluster of low luminosity protostars in Orion Molecular Cloud 2 (OMC2). It has been determined that the asymmetric distribution of the extended emission seen about IRS1 is in fact another infrared reflection nebula. Observations of near infrared polarimetry, photometry, and spectrophotometry were carried out at the NASA Infrared Telescope Facility October 1982 and January 1983. (author)

  14. PC 11: Symbiotic star or planetary nebulae?

    Gutierrez-Moreno, A.; Moreno, H.; Cortes, G.

    1987-01-01

    PC 11 is an object listed in Perek and Kohoutek (1967) Catalogue of Galactic Planetary Nebulae as PK 331 -5 0 1. Some authors suggest that it is not a planetary nebula, but that it has some characteristics (though not all) of symbiotic stars. We have made photographic, spectrophotometric and spectroscopic observations of PC 11. The analysis of the results suggests that it is a young planetary nebula. (Author)

  15. The western Veil nebula (Image)

    Glenny, M.

    2009-12-01

    The western Veil nebula in Cygnus. 15-part mosaic by Mike Glenny, Gloucestershire, taken over several months mostly in the autumn of 2008. 200mm LX90/f10 autoguided, Meade UHC filter, 0.3xFR/FF, Canon 20Da DSLR. Exposures each typically 10x360 secs at ISO1600, processed in Registax4, PixInsight (for flat field correction) & Photoshop CS.

  16. Electron densities in planetary nebulae

    Stanghellini, L.; Kaler, J.B.

    1989-01-01

    Electron densities for 146 planetary nebulae have been obtained for analyzing a large sample of forbidden lines by interpolating theoretical curves obtained from solutions of the five-level atoms using up-to-date collision strengths and transition probabilities. Electron temperatures were derived from forbidden N II and/or forbidden O III lines or were estimated from the He II 4686 A line strengths. The forbidden O II densities are generally lower than those from forbidden Cl III by an average factor of 0.65. For data sets in which forbidden O II and forbidden S II were observed in common, the forbidden O II values drop to 0.84 that of the forbidden S II, implying that the outermost parts of the nebulae might have elevated densities. The forbidden Cl II and forbidden Ar IV densities show the best correlation, especially where they have been obtained from common data sets. The data give results within 30 percent of one another, assuming homogeneous nebulae. 106 refs

  17. Evolution of planetary nebula nuclei

    Shaw, R.A.

    1985-01-01

    The evolution of planetary nebula nuclei (PNNs) is examined with the aid of the most recent available stellar evolution calculations and new observations of these objects. Their expected distribution in the log L-log T plane is calculated based upon the stellar evolutionary models of Paczynski, Schoenberner and Iben, the initial mass function derived by Miller and Scalo, and various assumptions concerning mass loss during post-main sequence evolution. The distribution is found to be insensitive both to the assumed range of main-sequence progenitor mass and to reasonable variations in the age and the star forming history of the galactic disk. Rather, the distribution is determined by the strong dependence of the rate of stellar evolution upon core mass, the steepness of the initial mass function, and to a lesser extent the finite lifetime of an observable planetary nebula. The theoretical distributions are rather different than any of those inferred from earlier observations. Possible observational selection effects that may be responsible are examined, as well as the intrinsic uncertainties associated with the theoretical model predictions. An extensive photometric and smaller photographic survey of southern hemisphere planetary nebulae (PNs) is presented

  18. X-ray observations of planetary nebulae

    Apparao, K.M.V.; Tarafdar, S.P.

    1990-01-01

    The Einstein satellite was used to observe 19 planetary nebulae and X-ray emission was detected from four planetary nebulae. The EXOSAT satellite observed 12 planetary nebulae and five new sources were detected. An Einstein HRI observation shows that NGC 246 is a point source, implying that the X-rays are from the central star. Most of the detected planetary nebulae are old and the X-rays are observed during the later stage of planetary nebulae/central star evolution, when the nebula has dispersed sufficiently and/or when the central star gets old and the heavy elements in the atmosphere settle down due to gravitation. However in two cases where the central star is sufficiently luminous X-rays were observed, even though they were young nebulae; the X-radiation ionizes the nebula to a degree, to allow negligible absorption in the nebula. Temperature T x is obtained using X-ray flux and optical magnitude and assuming the spectrum is blackbody. T x agrees with Zanstra temperature obtained from optical Helium lines. (author)

  19. Luminosity function for planetary nebulae and the number of planetary nebulae in local group galaxies

    Jacoby, G.H.

    1980-01-01

    Identifications of 19 and 34 faint planetary nebulae have been made in the central regions of the SMC and LMC, respectively, using on-line/off-line filter photography at [O III] and Hα. The previously known brighter planetary nebulae in these fields, eight in both the SMC and the LMC, were also identified. On the basis of the ratio of the numbers of faint to bright planetary nebulae in these fields and the numbers of bright planetary nebulae in the surrounding fields, the total numbers of planetary nebulae in the SMC and LMC are estimated to be 285 +- 78 and 996 +- 253, respectively. Corrections have been applied to account for omissions due to crowding confusion in previous surveys, spatial and detectability incompleteness, and obscuration by dust.Equatorial coordinates and finding charts are presented for all the identified planetary nebulae. The coordinates have uncertainties smaller than 0.''6 relative to nearby bright stars, thereby allowing acquisition of the planetary nebulae by bling offsetting.Monochromatic fluxes are derived photographically and used to determine the luminosity function for Magellanic Cloud planetary nebulae as faint as 6 mag below the brightest. The luminosity function is used to estimate the total numbers of planetary nebulae in eight Local Group galaxies in which only bright planetary nebulae have been identified. The dervied luminosity specific number of planetary nebulae per unit luminosity is nearly constant for all eight galaxies, having a value of 6.1 x 10 -7 planetary nebulae L -1 /sub sun/. The mass specific number, based on the three galaxies with well-determined masses, is 2.1 x 10 -7 planetary nebulae M -1 /sub sun/. With estimates for the luminosity and mass of our Galaxy, its total number of planetary nebulae is calculated to be 10,000 +- 4000, in support of the Cudworth distance scale

  20. Optical observations of southern planetary nebula candidates

    VandeSteene, GC; Sahu, KC; Pottasch, [No Value

    1996-01-01

    We present H alpha+[NII] images and low resolution spectra of 16 IRAS-selected, southern planetary nebula candidates previously detected in the radio continuum. The H alpha+[NII] images are presented as finding charts. Contour plots are shown for the resolved planetary nebulae. From these images

  1. Abundances of planetary nebula NGC 5315

    Pottasch, [No Value; Beintema, DA; Salas, JB; Koornneef, J; Feibelman, WA

    2002-01-01

    The ISO and IUE spectra of the elliptical nebula NGC 5315 is presented. These spectra are combined with the spectra in the visual wavelength region to obtain a complete, extinction corrected, spectrum. The chemical composition of the nebulae is then calculated and compared to previous

  2. Plerions and pulsar-powered nebulae

    Gaensler, Bryan

    2000-01-01

    In this brief review, I discuss recent developments in the study of pulsar-powered nebulae ("plerions"). The large volume of data which has been acquired in recent years reveals a diverse range of observational properties, demonstrating how differing environmental and pulsar properties manifest themselves in the resulting nebulae.

  3. A Smoking Gun in the Carina Nebula

    Hamaguchi, Kenji; Corcoran, Michael F.; Ezoe, Yuichiro; Townsley, Leisa; Broos, Patrick; Gruendl, Robert; Vaidya, Kaushar; White, Stephen M.; Petre, Rob; Chu, You-Hua

    2009-01-01

    The Carina Nebula is one of thc youngest, most active sites of massive star formation in our Galaxy. In this nebula, we have discovered a bright X-ray source that has persisted for approx.30 years. The soft X-ray spectrum. consistent with kT approx.130 eV blackbody radiation with mild extinction, and no counterpart in the near- and mid-infrared wavelengths indicate that it is a, approx. 10(exp 6)-year-old neutron star housed in the Carina Nebula. Current star formation theory does not suggest that the progenitor of the neutron star and massive stars in the Carina Nebula, in particular (eta)Car, are coeval. This result demonstrates that the Carina Nebula experienced at least two major episodes of massive star formation. The neutron star would be responsible for remnants of high energy activity seen in multiple wavelengths.

  4. A SMOKING GUN IN THE CARINA NEBULA

    Hamaguchi, Kenji; Corcoran, Michael F.; Ezoe, Yuichiro; Townsley, Leisa; Broos, Patrick; Gruendl, Robert; Vaidya, Kaushar; Chu, You-Hua; White, Stephen M.; Strohmayer, Tod; Petre, Rob

    2009-01-01

    The Carina Nebula is one of the youngest, most active sites of massive star formation in our Galaxy. In this nebula, we have discovered a bright X-ray source that has persisted for ∼30 years. The soft X-ray spectrum, consistent with kT ∼ 128 eV blackbody radiation with mild extinction, and no counterpart in the near- and mid-infrared wavelengths indicates that it is a ∼10 6 year old neutron star housed in the Carina Nebula. Current star formation theory does not suggest that the progenitors of the neutron star and massive stars in the Carina Nebula, in particular η Car, are coeval. This result suggests that the Carina Nebula experienced at least two major episodes of massive star formation. The neutron star may be responsible for remnants of high-energy activity seen in multiple wavelengths.

  5. NIF Discovery Science Eagle Nebula

    Kane, Jave; Martinez, David; Pound, Marc; Heeter, Robert; Casner, Alexis; Villette, Bruno; Mancini, Roberto

    2017-10-01

    The University of Maryland and and LLNL are investigating the origin and dynamics of the famous Pillars of the Eagle Nebula and similar parsec-scale structures at the boundaries of HII regions in molecular hydrogen clouds. The National Ignition Facility (NIF) Discovery Science program Eagle Nebula has performed NIF shots to study models of pillar formation. The shots feature a new long-duration x-ray source, in which multiple hohlraums mimicking a cluster of stars are driven with UV light in series for 10 to 15 ns each to create a 30 to 60 ns output x-ray pulse. The source generates deeply nonlinear hydrodynamics in the Eagle science package, a structure of dense plastic and foam mocking up a molecular cloud containing a dense core. Omega EP and NIF shots have validated the source concept, showing that earlier hohlraums do not compromise later ones by preheat or by ejecting ablated plumes that deflect later beams. The NIF shots generated radiographs of shadowing-model pillars, and also showed evidence that cometary structures can be generated. The velocity and column density profiles of the NIF shadowing and cometary pillars have been compared with observations of the Eagle Pillars made at the millimeter-wave BIMA and CARMA observatories. Prepared by LLNL under Contract DE-AC52-07NA27344.

  6. Reconstruction and visualization of planetary nebulae.

    Magnor, Marcus; Kindlmann, Gordon; Hansen, Charles; Duric, Neb

    2005-01-01

    From our terrestrially confined viewpoint, the actual three-dimensional shape of distant astronomical objects is, in general, very challenging to determine. For one class of astronomical objects, however, spatial structure can be recovered from conventional 2D images alone. So-called planetary nebulae (PNe) exhibit pronounced symmetry characteristics that come about due to fundamental physical processes. Making use of this symmetry constraint, we present a technique to automatically recover the axisymmetric structure of many planetary nebulae from photographs. With GPU-based volume rendering driving a nonlinear optimization, we estimate the nebula's local emission density as a function of its radial and axial coordinates and we recover the orientation of the nebula relative to Earth. The optimization refines the nebula model and its orientation by minimizing the differences between the rendered image and the original astronomical image. The resulting model allows creating realistic 3D visualizations of these nebulae, for example, for planetarium shows and other educational purposes. In addition, the recovered spatial distribution of the emissive gas can help astrophysicists gain deeper insight into the formation processes of planetary nebulae.

  7. Processing NASA Earth Science Data on Nebula Cloud

    Chen, Aijun; Pham, Long; Kempler, Steven

    2012-01-01

    Three applications were successfully migrated to Nebula, including S4PM, AIRS L1/L2 algorithms, and Giovanni MAPSS. Nebula has some advantages compared with local machines (e.g. performance, cost, scalability, bundling, etc.). Nebula still faces some challenges (e.g. stability, object storage, networking, etc.). Migrating applications to Nebula is feasible but time consuming. Lessons learned from our Nebula experience will benefit future Cloud Computing efforts at GES DISC.

  8. The Making of a Pre-Planetary Nebula

    Kohler, Susanna

    2017-07-01

    The gas expelled by dying stars gets twisted into intricate shapes and patterns as nebulae form. Now a team of researchers might have some answers about how this happens.Whats a Pre-Planetary Nebula?This H-R diagram for the globular cluster M5 shows where AGB stars lie: they are represented by blue markers here. The AGB is one of the final stages in a low- to intermediate-mass stars lifetime. [Lithopsian]When a low- to intermediate-mass star approaches the end of its lifetime, it moves onto the Asymptotic Giant Branch (AGB) in the Herzsprung-Russell diagram. As the star exhausts its fuel here, it shrugs off its outer layers. These layers of gas then encase the stars core, which is not yet hot enough to ionize the gas and cause it to glow.Instead, during this time the gas is relatively cool and dark, faintly reflecting light from the star and emitting only very dim infrared emission of its own. At this stage, the gas represents a pre-planetary nebula. Only later when the stellar core contracts enough to heat up and emit ionizing radiation does the nebula begin to properly glow, at which point it qualifies as a full planetary nebula.Images of OH231 in optical light (top) and 12CO (bottom) taken from the literature. [See Balick et al. 2017 for full credit]Unexpected ShapesPre-planetary nebulae are a very short-lived evolutionary stage, so weve observed only a few hundred of them which has left many unanswered questions about these objects.One particular mystery is that of their shapes: if these nebulae are formed by stars expelling their outer layers, we would naively expect them to be simple spherical shells and yet we observe pre-planetary nebulae to have intricate shapes and patterns. How does the star create these asymmetric shapes? A team of scientists led by Bruce Balick (University of Washington, Seattle) has now used simulations to address this question.Injecting MassBalick and collaborators use 3D hydrodynamic simulations to model one particular pre

  9. Planetary nebulae and the interstellar magnetic field

    Heiligman, G.M.

    1980-01-01

    Previous workers have found a statistical correlation between the projected directions of the interstellar magnetic field and the major axes of planetary nebulae. This result has been examined theoretically using a numerical hydromagnetic model of a cold plasma nebula expanding into a uniform vacuum magnetic field, with nebular gas accreting on the surface. It is found that magnetic pressure alone is probably not sufficient to shape most planetary nebulae to the observed degree. Phenomena are discussed which could amplify simple magnetic pressure, alter nebular morphology and account for the observed correlation. (author)

  10. Spatiokinematical models of five planetary nebulae

    Sabbadin, F.

    1984-01-01

    The [OOOI] and Hα expansion velocity fields in the planetary nebulae NGC6058 and 6804 and the [OIII], Hα and [NII] expansion velocity fields in NGC6309, 6751 and 6818, were obtained from high dispersion spectra. Spatiokinematical models of the nebulae were derived assuming an expansion velocity of the gas proportional to the distance from the central star and using the expansion velocity-radius correlation previously given. The observational parameters of the nebulae (radius, mass and expansion velocity) and of the exciting stars (temperature, radius and luminosity) closely fit the suggested evolutionary model for this class of objects. (author)

  11. Radio Observations of Elongated Pulsar Wind Nebulae

    Ng, Stephen C.-Y.

    2015-08-01

    The majority of pulsars' rotational energy is carried away by relativistic winds, which are energetic particles accelerated in the magnetosphere. The confinement of the winds by the ambient medium result in synchrotron bubbles with broad-band emission, which are commonly referred to as pulsar wind nebulae (PWNe). Due to long synchrotron cooling time, a radio PWN reflects the integrated history of the system, complementing information obtained from the X-ray and higher energy bands. In addition, radio polarization measurements can offer a powerful probe of the PWN magnetic field structure. Altogether these can reveal the physical conditions and evolutionary history of a system.I report on preliminary results from high-resolution radio observations of PWNe associated with G327.1-1.1, PSRs J1015-5719, B1509-58, and J1549-4848 taken with the Australia Telescope Compact Array (ATCA). Their magnetic field structure and multiwavelength comparison with other observations are discussed.This work is supported by a ECS grant of the Hong Kong Government under HKU 709713P. The Australia Telescope is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.

  12. Star Formation in the Orion Nebula Cluster

    Palla, Francesco; Stahler, Steven W.

    1999-11-01

    We study the record of star formation activity within the dense cluster associated with the Orion Nebula. The bolometric luminosity function of 900 visible members is well matched by a simplified theoretical model for cluster formation. This model assumes that stars are produced at a constant rate and distributed according to the field-star initial mass function. Our best-fit age for the system, within this framework, is 2×106 yr. To undertake a more detailed analysis, we present a new set of theoretical pre-main-sequence tracks. These cover all masses from 0.1 to 6.0 Msolar, and start from a realistic stellar birthline. The tracks end along a zero-age main-sequence that is in excellent agreement with the empirical one. As a further aid to cluster studies, we offer an heuristic procedure for the correction of pre-main-sequence luminosities and ages to account for the effects of unresolved binary companions. The Orion Nebula stars fall neatly between our birthline and zero-age main-sequence in the H-R diagram. All those more massive than about 8 Msolar lie close to the main sequence, as also predicted by theory. After accounting for the finite sensitivity of the underlying observations, we confirm that the population between 0.4 and 6.0 Msolar roughly follows a standard initial mass function. We see no evidence for a turnover at lower masses. We next use our tracks to compile stellar ages, also between 0.4 and 6.0 Msolar. Our age histogram reveals that star formation began at a low level some 107 yr ago and has gradually accelerated to the present epoch. The period of most active formation is indeed confined to a few×106 yr, and has recently ended with gas dispersal from the Trapezium. We argue that the acceleration in stellar births, which extends over a wide range in mass, reflects the gravitational contraction of the parent cloud spawning this cluster.

  13. VLA observations of a highly symmetric OH maser in a bipolar nebula

    Morris, M.; Bowers, P.F.; Turner, B.E.

    1982-01-01

    The Very Large Array was used to map 1667 MHz OH maser emission from the bipolar nebula OH 231.8+4.2 at 23 distinct velocities within the unusual, 100 km s -1 wide profile. The source is large (approx.10''equivalent3 x 10 17 cm) and well resolved, and displays ordered large-scale velocity gradients. At most velocities, the maser maps display an unmistakable symmetry about the bipolar axis defined by the optical and infrared reflection nebulae. Most of the data can be accounted for by an axisymmetric model in which the measuring OH is concentrated toward the system's equatorial plane and is expanding radially away from the central star. The observation of complete rings of maser emission at some velocities, however, shows that the maser is also present at high latitudes above the equatorial plane. A model which incorporates these features plus other known aspects of bipolar nebulae is presented and discussed

  14. Nebulae and how to observe them

    Coe, Steven

    2007-01-01

    This "Astronomers' Observing Guides" are designed for practical amateur astronomers who not only want to observe, but want to know the details of exactly what they are looking at. Nebulae are the places where the stars are born. For amateur astronomers, the many different kinds of nebulae vary from "easy" targets that can be seen with modest equipment under mediocre skies, to "challenging" objects that require experienced observers, large telescopes and excellent seeing. The concept of the book - and of the series - is to present an up-to-date detailed description and categorisation (part one); and then (part two) to consider how best to successfully observe and record the large range of astronomical objects that fall under the general heading of "nebulae". "Nebulae, and How to Observe Them" is a mine of information for all levels of amateur observers, from the beginner to the experienced.

  15. Hot relativistic winds and the Crab nebula

    Fujimura, F.S.; Kennel, C.F.

    1981-01-01

    Efforts are reviewed to construct a self-consistent model of pulsar magnetospheres that links the particle source near the pulsar to the outflowing relativistic wind and couples the wind to the surrounding nebula. (Auth.)

  16. Spatially extended K Iλ7699 emission in the nebula of VY CMa: kinematics and geometry

    Smith, Nathan

    2004-04-01

    Long-slit echelle spectra reveal bright extended emission from the K Iλ7699 resonance line in the reflection nebula surrounding the extreme red supergiant VY Canis Majoris. The central star has long been known for its unusually bright K I emission lines, but this is the first report of intrinsic emission from K I in the nebula. The extended emission is not just a reflected spectrum of the star, but is due to resonant scattering by K atoms in the outer nebula itself, and is therefore a valuable probe of the kinematics and geometry of the circumstellar environment of VY CMa. Dramatic velocity structure is seen in the long-slit spectra, and most lines of sight through the nebula intersect multiple distinct velocity components. A faint `halo' at large distances from the star does appear to show a reflected spectrum, however, and suggests a systemic velocity of +40 km s-1 with respect to the Sun. The most striking feature is blueshifted emission from the filled interior of a large shell seen in images; the kinematic structure is reminiscent of a Hubble flow, and provides strong evidence for asymmetric and episodic mass loss due to localized eruptions on the stellar surface.

  17. The Boomerang Nebula: a highly polarized bipolar

    Taylor, K.N.R.; Scarrott, S.M.

    1980-01-01

    An optical linear polarization map of a bipolar nebula is presented. Polarizations of approximately 60 per cent are observed in the optically thin lobes. The map leads to a geometry of the object consisting of a central star with an equatorial disc of dust and optically thin lobes illuminated by the central star. The grains in the disc are aligned. The object is a protoplanetary nebula. (author)

  18. Is gas in the Orion nebula depleted

    Aiello, S.; Guidi, I.

    1978-01-01

    Depletion of heavy elements has been recognized to be important in the understanding of the chemical composition of the interstellar medium. This problem is also relevant to the study of H II regions. In this paper the gaseous depletion in the physical conditions of the Orion nebula is investigated. The authors reach the conclusion that very probably no depletion of heavy elements, due to sticking on dust grains, took place during the lifetime of the Orion nebula. (Auth.)

  19. Evolutionary sequence of models of planetary nebulae

    Vil'koviskij, Eh.Ya.; Kondrat'eva, L.N.; Tambovtseva, L.V.

    1983-01-01

    The evolutionary sequences of model planetary nebulae of different masses have been calculated. The computed emission line intensities are compared with the observed ones by means of the parameter ''reduced size of the nebula'', Rsub(n). It is shown that the evolution tracks of Schonberner for the central stars are consistent with the observed data. Part of ionized mass Mi in any nebulae does not not exceed 0.3 b and in the average Msu(i) 3 years at actual values of radius Rsub(i) <0.025 ps. Then the luminosity growth slows down to the maximum temperature which central star reaches and decreases with sharp decrease of the star luminosity. At that, the radius of ionized zone of greater mass nebulae can even decrease, inspite of the constant expansion of the nebula. As a result nebulae of great masses having undergone the evolution can be included in the number of observed compact objects (Rsub(n) < 0.1 ps)

  20. Photoionization modelling of planetary nebulae - II. Galactic bulge nebulae, a comparison with literature results

    van Hoof, PAM; Van de Steene, GC

    1999-01-01

    We have constructed photoionization models of five galactic bulge planetary nebulae using our automatic method, which enables a fully self-consistent determination of the physical parameters of a planetary nebula. The models are constrained using the spectrum, the IRAS and radio fluxes and the

  1. The Crab Nebula flaring activity

    Montani, G., E-mail: giovanni.montani@frascati.enea.it [ENEA – C.R, UTFUS-MAG, via Enrico Fermi 45, I-00044 Frascati (RM) (Italy); Dipartimento di Fisica, Università di Roma “Sapienza”, p.le Aldo Moro 5, I-00185 Roma (Italy); Bernardini, M.G. [INAF – Osservatorio Astronomico di Brera, via Bianchi 46, I-23807 Merate (Italy)

    2014-12-12

    The discovery made by AGILE and Fermi of a short time scale flaring activity in the gamma-ray energy emission of the Crab Nebula is a puzzling and unexpected feature, challenging particle acceleration theory. In the present work we propose the shock-induced magnetic reconnection as a viable mechanism to explain the Crab flares. We postulate that the emitting region is located at ∼10{sup 15} cm from the central pulsar, well inside the termination shock, which is exactly the emitting region size as estimated by the overall duration of the phenomenon ∼1 day. We find that this location corresponds to the radial distance at which the shock-induced magnetic reconnection process is able to accelerate the electrons up to a Lorentz factor ∼10{sup 9}, as required by the spectral fit of the observed Crab flare spectrum. The main merit of the present analysis is to highlight the relation between the observational constraints to the flare emission and the radius at which the reconnection can trigger the required Lorentz factor. We also discuss different scenarios that can induce the reconnection. We conclude that the existence of a plasma instability affecting the wind itself as the Weibel instability is the privileged scenario in our framework.

  2. Ultraviolet imaging of planetary nebulae with GALEX

    Bianchi, Luciana; Thilker, David

    2018-05-01

    Over four hundred Galactic Planetary Nebulae (PNe) have been imaged by GALEX in two ultraviolet (UV) bands, far-UV (FUV, 1344-1786 Å, λ _{eff}= 1528 Å) and near-NUV (NUV, 1771-2831 Å, λ _{eff} = 2271 Å). We present examples of extended PNe, for which UV spectroscopy is also available, to illustrate the variety in UV morphology and color, which reflects ionization conditions. The depth of the GALEX imaging varies from flux ≈ 0.4/5× 10 ^{-18} ergs cm^{-2} s^{-1} Å^{-1} \\square ^'' -1} (FUV/NUV) for exposures of the order of ˜ 100 seconds, typical of the survey with the largest area coverage, to ˜ 0.3/8.3× 10^{-19} ergs cm^{-2} s^{-1} Å^{-1} \\square ^'' -1} (FUV/NUV) for ˜ 1500 sec exposures, typical of the second largest survey (see Bianchi in Astrophys. Space Sci. 320:11, 2009; Bianchi et al. in Adv. Space Res. 53:900, 2014). GALEX broad-band FUV and NUV fluxes include nebular emission lines and in some cases nebular continuum emission. The sensitivity of the GALEX instrument and the low sky background, especially in FUV, enable detection and mapping of very faint ionization regions and fronts, including outermost wisps and bow shocks. The FUV-NUV color of the central star provides a good indication of its T_{eff}, because the GALEX FUV-NUV color is almost reddening-free for Milky Way type dust (Bianchi et al. in Astrophys. J. Suppl. Ser. 230:24, 2017; Bianchi in Astrophys. Space Sci. 335:51, 2011, Bianchi in Astrophys. Space Sci. 354:103, 2014) and it is more sensitive to hot temperatures than optical colors.

  3. Abundance determinations in HII regions and planetary nebulae

    Stasinska, Grazyna

    2002-01-01

    The methods of abundance determinations in HII regions and planetary nebulae are described, with emphasis on the underlying assumptions and inherent problems. Recent results on abundances in Galactic HII regions and in Galactic and extragalactic Planetary Nebulae are reviewed.

  4. Lunar occultation observations of the Crab Nebula

    Maloney, F.P.

    1977-01-01

    Three lunar of occultations of the Crab Nebula were observed, two at 114 MHz and one at 26.3 MHz, during the 1974 series of events. The higher frequency observations were deconvolved of diffraction effects to yield four strip integrated brightness profiles of the Nebula, with an effective resolution of 30 arc-seconds. These four profiles were Fourier inverted and cleaned of sidelobe structure to synthesize a two-dimensional map of the Nebula. At 114 MHz, the Nebula is composed of a broad envelope of emission which contains several smaller sources. The attenuation of the low radio frequency radiation by the thermal hydrogen in the filaments is considered as a possible mechanism to explain these new data. The 26.3 MHz observations indicate the presence of a bright, localized source containing greater than 80% of the flux of the Nebula. The position of the source is confined by the data to a narrow strip centered at the pulsar position. Both sets of data are compared with past occultation observations

  5. Ring nebulae associated with Wolf-Rayet stars

    Chu, Y.-H.

    1982-01-01

    Using strict selection criteria, the author and colleagues have searched for ring nebulae associated with Wolf-Rayet stars in the Galaxy and the Magellanic Clouds. 15 WR ring nebulae are identified in the Galaxy, 9 in the Large Magellanic Cloud, and none in the small Magellanic Cloud. The morphology and kinematics of these 24 nebulae have subsequently been observed to study their nature. These nebulae and their references are listed and a correlation between spectral and nebular types is presented. (Auth.)

  6. Monitoring the Crab Nebula with LOFT

    Wilson-Hodge, Colleen A.

    2012-01-01

    From 2008-2010, the Crab Nebula was found to decline by 7% in the 15-50 keV band, consistently in Fermi GBM, INTEGRAL IBIS, SPI, and JEMX, RXTE PCA, and Swift BAT. From 2001-2010, the 15-50 keV flux from the Crab Nebula typically varied by about 3.5% per year. Analysis of RXTE PCA data suggests possible spectral variations correlated with the flux variations. I will present estimates of the LOFT sensitivity to these variations. Prior to 2001 and since 2010, the observed flux variations have been much smaller. Monitoring the Crab with the LOFT WFM and LAD will provide precise measurements of flux variations in the Crab Nebula if it undergoes a similarly active episode.

  7. Medium-resolution échelle spectroscopy of the Red Square Nebula, MWC 922

    Wehres, N.; Ochsendorf, B. B.; Tielens, A. G. G. M.; Cox, N. L. J.; Kaper, L.; Bally, J.; Snow, T. P.

    2017-05-01

    Context. Medium-resolution échelle spectra of the Red Square Nebula surrounding the star MWC 922 are presented. The spectra have been obtained in 2010 and 2012 using the X-shooter spectrograph mounted on the Very Large Telescope (VLT) in Paranal, Chile. The spectrum covers a wavelength range between 300 nm-2.5 μm and shows that the nebula is rich in emission lines. Aims: We aim to identify the emission lines and use them as a tool to determine the physical and chemical characteristics of the nebula. The emission lines are also used to put constraints on the structure of the nebula and on the nature of the central stars. Methods: We analyzed and identified emission lines that indicated that the Red Square Nebula consists of a low density bipolar outflow, eminent in the broad emission component seen in [Fe II], as well as in P Cygni line profiles indicative of fast outflowing material. The narrow component in the [Fe II] lines is most likely formed in the photosphere of a surrounding disk. Some of the emission lines show a pronounced double peaked profile, such as Ca II, indicating an accretion disk in Keplerian rotation around the central star. [O I] emission lines are formed in the neutral atomic zone separating the ionized disk photosphere from the molecular gas in the interior of the disk, which is prominent in molecular CO emission in the near-IR. [N II] and [S II] emission clearly originates in a low density but fairly hot (7 000-10 000 K) nebular environment. H I recombination lines trace the extended nebula as well as the photosphere of the disk. Results: These findings put constraints on the evolution of the central objects in MWC 922. The Red Square shows strong similarities to the Red Rectangle Nebula, both in morphology and in its mid-IR spectroscopic characteristics. As for the Red Rectangle, the observed morphology of the nebula reflects mass-loss in a binary system. Specifically, we attribute the biconical morphology and the associated rung

  8. Hubble Space Telescope Image of Omega Nebula

    2002-01-01

    This sturning image, taken by the newly installed Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope (HST), is an image of the center of the Omega Nebula. It is a hotbed of newly born stars wrapped in colorful blankets of glowing gas and cradled in an enormous cold, dark hydrogen cloud. The region of nebula shown in this photograph is about 3,500 times wider than our solar system. The nebula, also called M17 and the Swan Nebula, resides 5,500 light-years away in the constellation Sagittarius. The Swan Nebula is illuminated by ultraviolet radiation from young, massive stars, located just beyond the upper-right corner of the image. The powerful radiation from these stars evaporates and erodes the dense cloud of cold gas within which the stars formed. The blistered walls of the hollow cloud shine primarily in the blue, green, and red light emitted by excited atoms of hydrogen, nitrogen, oxygen, and sulfur. Particularly striking is the rose-like feature, seen to the right of center, which glows in the red light emitted by hydrogen and sulfur. As the infant stars evaporate the surrounding cloud, they expose dense pockets of gas that may contain developing stars. One isolated pocket is seen at the center of the brightest region of the nebula. Other dense pockets of gas have formed the remarkable feature jutting inward from the left edge of the image. The color image is constructed from four separate images taken in these filters: blue, near infrared, hydrogen alpha, and doubly ionized oxygen. Credit: NASA, H. Ford (JHU), G. Illingworth (USCS/LO), M. Clampin (STScI), G. Hartig (STScI), the ACS Science Team, and ESA.

  9. From red giants to planetary nebulae: Asymmetries, dust, and polarization

    Johnson, J.J.

    1990-01-01

    In order to investigate the development of aspherical planetary nebulae, polarimetry was obtained for a group of planetary nebulae and for objects that will evolve into planetary nebulae, i.e., red giants, late asymptotic giant branch (AGB) objects, proto-planetary nebulae, and young planetary nebulae. To study the dust around the objects in our sample, we also used data from the Infrared Astronomy Satellite (IRAS) mission. The youngest objects in our survey, red giants, had the hottest dust temperatures while planetary nebulae had the coolest. Most of the objects were intrinsically polarized, including the red giants. This indicated that the circumstellar dust shells of these objects were aspherical. Both carbon- and oxygen-rich objects could be intrinsically polarized. The intrinsic polarizations of a sample of our objects were modeled using an ellipsoidal circumstellar dust shell. The findings of this study suggest that the asphericities that lead to an aspherical planetary nebula originate when a red giant begins to undergo mass loss. The polarization and thus the asphericity as the star evolves, with both reaching a maximum during the proto-planetary nebula stage. The circumstellar dust shell will dissipate after the proto-planetary nebulae stage since no new material is being added. The polarization of planetary nebulae will thus be low. In the most evolved planetary nebulae, the dust has either been destroyed or dissipated into the interstellar medium. In these objects no polarization was observed

  10. An IFU-view of Planetary Nebulae: Exploring NGC 6720 (Ring Nebula) with KCWI

    Hoadley, Keri; Matuszewski, Matt; Hamden, Erika; Martin, Christopher; Neill, Don; Kyne, Gillian

    2018-01-01

    Studying the interaction between the ejected stellar material and interstellar clouds is important for understanding how stellar deaths influences the pollution of matter that will later form other stars. Planetary nebulae provide ideal laboratories to study such interactions. I will present on a case study of one close-by planetary nebula, the Ring Nebula (M 57, NGC 6720), to infer the abundances, temperatures, structures, and dynamics of important atomic and ionic species in two distinct regions of the nebula using a newly-commissioned integral field spectrograph (IFS) on Keck: the Keck Cosmic Web Imager (KCWI). The advantage of an IFS over traditional filter-imaging techniques is the ability to simultaneously observe the spectrum of any given pixel in the imaging area, which provides crucial information about the dynamics of the observed region. This technique is powerful for diffuse or extended astrophysical objects, and I will demonstrate the different imaging and spectral modes of KCWI used to observe the Ring Nebula.KCWI observations of the Ring Nebula focused mainly on the innermost region of the nebula, with a little coverage of the Inner Ring. We also observed the length of the Ring in one set of observations, for which we will estimate the elemental abundances, temperatures, and dynamics of the region. KCWI observations also capture an inner arc and blob that have distinctly difference characteristics than the Ring itself and may be a direct observation of either the planetary nebula ramming into an interstellar cloud projected onto the sightline or a dense interstellar cloud being illuminated by the stellar continuum from the hot central white dwarf.

  11. Angular diameters of Magellanic Cloud plantary nebulae. I. Speckle interferometry

    Wood, P.R.; Bessell, M.S.; Dopita, M.A.

    1986-01-01

    Speckle interferometric angular diameters of Magellanic Cloud planetary nebulae are presented. The mass of ionized gas in each nebula has been derived from the angular diameter and published H-beta line fluxes; the derives masses range from less than 0.006 to more than 0.19 solar mass. The planetary nebulae observed were the brightest in the Magellanic Clouds; consequently, they are all relatively small, young, bright, and dense. They are almost certainly only partially ionized, so that the masses derived for the ionized parts of the nebula are lower limits to the total nebula mass. The properties of the Magellanic Cloud nebulae are compared with those of planetary nebulae at the galactic center. 27 references

  12. HM Sagittae as a young planetary nebula

    Kwok, S.; Purton, C.R.

    1979-01-01

    HM Sagittae is suggested to be a very young planetary nebula recently transformed from a red-giant star through continuous mass loss. The observational data for HM Sge have been analyzed in terms of the interacting stellar wind model of planetary nebula formation. The model is in accord with virtually all the spectral data available--radio, optical, and infrared--as well as with the remarkable brightening of HM Sge observed in 1975. In particular, all three gaseous components predicted by the model are observed in the optical spectrum. The density in the newly formed shell is found to be at least 5 x 10 7 cm -3 , a value considerably higher than that found by the conventional analysis, which assumes a single-component homogeneous nebula. The radio spectrum is dominated by free-free emission from the remnant red-giant wind. The infrared spectrum suggests the presence of two dust components, one consisting of silicate grains left over from the red-giant stage and the other of grains newly formed after the 1975 brightening. The low observed shell mass is consistent with the interacting stellar wind model but is not consistent with the conventional sudden-ejection model of planetary nebula formation

  13. Turbulent Magnetic Relaxation in Pulsar Wind Nebulae

    Zrake, Jonathan [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, SLAC National Accelerator Laboratory, Menlo Park, CA 94025 (United States); Arons, Jonathan [Astronomy Department and Theoretical Astrophysics Center, University of California, Berkeley, 601 Campbell Hall, Berkeley, CA 94720 (United States)

    2017-09-20

    We present a model for magnetic energy dissipation in a pulsar wind nebula. A better understanding of this process is required to assess the likelihood that certain astrophysical transients may be powered by the spin-down of a “millisecond magnetar.” Examples include superluminous supernovae, gamma-ray bursts, and anticipated electromagnetic counterparts to gravitational wave detections of binary neutron star coalescence. Our model leverages recent progress in the theory of turbulent magnetic relaxation to specify a dissipative closure of the stationary magnetohydrodynamic (MHD) wind equations, yielding predictions of the magnetic energy dissipation rate throughout the nebula. Synchrotron losses are self-consistently treated. To demonstrate the model’s efficacy, we show that it can reproduce many features of the Crab Nebula, including its expansion speed, radiative efficiency, peak photon energy, and mean magnetic field strength. Unlike ideal MHD models of the Crab (which lead to the so-called σ -problem), our model accounts for the transition from ultra to weakly magnetized plasma flow and for the associated heating of relativistic electrons. We discuss how the predicted heating rates may be utilized to improve upon models of particle transport and acceleration in pulsar wind nebulae. We also discuss implications for the Crab Nebula’s γ -ray flares, and point out potential modifications to models of astrophysical transients invoking the spin-down of a millisecond magnetar.

  14. Turbulent Magnetic Relaxation in Pulsar Wind Nebulae

    Zrake, Jonathan; Arons, Jonathan

    2017-09-01

    We present a model for magnetic energy dissipation in a pulsar wind nebula. A better understanding of this process is required to assess the likelihood that certain astrophysical transients may be powered by the spin-down of a “millisecond magnetar.” Examples include superluminous supernovae, gamma-ray bursts, and anticipated electromagnetic counterparts to gravitational wave detections of binary neutron star coalescence. Our model leverages recent progress in the theory of turbulent magnetic relaxation to specify a dissipative closure of the stationary magnetohydrodynamic (MHD) wind equations, yielding predictions of the magnetic energy dissipation rate throughout the nebula. Synchrotron losses are self-consistently treated. To demonstrate the model’s efficacy, we show that it can reproduce many features of the Crab Nebula, including its expansion speed, radiative efficiency, peak photon energy, and mean magnetic field strength. Unlike ideal MHD models of the Crab (which lead to the so-called σ-problem), our model accounts for the transition from ultra to weakly magnetized plasma flow and for the associated heating of relativistic electrons. We discuss how the predicted heating rates may be utilized to improve upon models of particle transport and acceleration in pulsar wind nebulae. We also discuss implications for the Crab Nebula’s γ-ray flares, and point out potential modifications to models of astrophysical transients invoking the spin-down of a millisecond magnetar.

  15. Large proper motions in the Orion nebula

    Cudworth, K.M.; Stone, R.C.

    1977-01-01

    Several nebular features, as well as one faint star, with large proper motions were identified within the Orion nebula. The measured proper motions correspond to tangential velocities of up to approximately 70 km sec -1 . One new probable variable star was also found

  16. INTERNAL PROPER MOTIONS IN THE ESKIMO NEBULA

    García-Díaz, Ma. T.; Gutiérrez, L.; Steffen, W.; López, J. A.; Beckman, J.

    2015-01-01

    We present measurements of internal proper motions at more than 500 positions of NGC 2392, the Eskimo Nebula, based on images acquired with WFPC2 on board the Hubble Space Telescope at two epochs separated by 7.695 yr. Comparisons of the two observations clearly show the expansion of the nebula. We measured the amplitude and direction of the motion of local structures in the nebula by determining their relative shift during that interval. In order to assess the potential uncertainties in the determination of proper motions in this object, in general, the measurements were performed using two different methods, used previously in the literature. We compare the results from the two methods, and to perform the scientific analysis of the results we choose one, the cross-correlation method, because it is more reliable. We go on to perform a ''criss-cross'' mapping analysis on the proper motion vectors, which helps in the interpretation of the velocity pattern. By combining our results of the proper motions with radial velocity measurements obtained from high resolution spectroscopic observations, and employing an existing 3D model, we estimate the distance to the nebula to be 1.3 kpc

  17. INTERNAL PROPER MOTIONS IN THE ESKIMO NEBULA

    García-Díaz, Ma. T.; Gutiérrez, L.; Steffen, W.; López, J. A. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Km 103 Carretera Tijuana-Ensenada, 22860 Ensenada, B.C. (Mexico); Beckman, J., E-mail: tere@astro.unam.mx, E-mail: leonel@astro.unam.mx, E-mail: wsteffen@astro.unam.mx, E-mail: jal@astro.unam.mx, E-mail: jeb@iac.es [Instituto de Astrofísica de Canarias, La Laguna, Tenerife (Spain)

    2015-01-10

    We present measurements of internal proper motions at more than 500 positions of NGC 2392, the Eskimo Nebula, based on images acquired with WFPC2 on board the Hubble Space Telescope at two epochs separated by 7.695 yr. Comparisons of the two observations clearly show the expansion of the nebula. We measured the amplitude and direction of the motion of local structures in the nebula by determining their relative shift during that interval. In order to assess the potential uncertainties in the determination of proper motions in this object, in general, the measurements were performed using two different methods, used previously in the literature. We compare the results from the two methods, and to perform the scientific analysis of the results we choose one, the cross-correlation method, because it is more reliable. We go on to perform a ''criss-cross'' mapping analysis on the proper motion vectors, which helps in the interpretation of the velocity pattern. By combining our results of the proper motions with radial velocity measurements obtained from high resolution spectroscopic observations, and employing an existing 3D model, we estimate the distance to the nebula to be 1.3 kpc.

  18. A new bipolar nebula in Centaurus

    Wegner, G.; Glass, I.S.

    1979-01-01

    A new bipolar or butterfly-shaped nebula has been discovered and shown to have an infrared excess. The spectra of the central object and wings are of similar type, around G0. No emission lines are apparent. The infrared excess appears to be due to thermal emission from dust. (U.K.)

  19. Meteoritic Constraints on Models of the Solar Nebula: The Abundances of Moderately Volatile Elements

    Cassen, Patrick; Cuzzi, Jeff (Technical Monitor)

    1994-01-01

    The "moderately volatile" elements are those which condense (or evaporate) in the temperature range 650 - 1350 K, as a mix of material with solar abundances is cooled (or heated) tinder equilibrium conditions. Their relative abundances in chondritic meteorites are solar (or "cosmic", as defined by the composition of Cl meteorites) to within a factor of several, but vary within that range in a way that correlates remarkably well with condensation temperature, independent of chemical affinity. It has been argued that this correlation reflects a systematically selective process which favored the accretion of refractory material over volatile material from a cooling nebula. Wasson and Chou (Meteoritics 9, 69-94, 1974, and Wasson and co-authors in subsequent papers) suggested that condensation and settling of solids contemporaneously with the cooling and removal of nebular gas could produce the observed abundance patterns, but a quantitative model has been lacking. We show that the abundance patterns of the moderately volatile elements in chondritic meteorites can be produced, in some degree of quantitative detail, by models of the solar nebula that are designed to conform to observations of T Tauri stars and the global conservation laws. For example, even if the local surface density of the nebula is not decreasing, condensation and accretion of solids from radially inflowing gas in a cooling nebula can result in depletions of volatiles, relative to refractories, like those observed, The details of the calculated abundance patterns depend on (but are not especially sensitive to) model parameters, and can exhibit the variations that distinguish the meteorite classes. Thus it appears that nebula characteristics such as cooling rates, radial flow velocities, and particle accumulation rates can be quantitatively constrained by demanding that they conform to meteoritic data; and the models, in turn, can produce testable hypotheses regarding the time and location of the

  20. Gamma-rays and neutrinos from the pulsar wind nebulae

    Bednarek, W.; Bartosik, M.

    2005-01-01

    We construct the time-dependent radiation model for the pulsar wind nebulae (PWNe), assuming that leptons are accelerated in resonant scattering with heavy nuclei, which are injected into the nebula by the pulsar. The equilibrium spectra of these particles inside the nebula are calculated taking into account their radiation and adiabatic energy losses. The spectra of γ-rays produced by these particles are compared with the observations of the PWNe emitting TeV γ-rays and predictions are made for the expected γ-ray fluxes from other PWNe. Expected neutrino fluxes and neutrino event rates in a 1 km 2 neutrino detector from these nebulae are also calculated. It is concluded that only the Crab Nebula can produce a detectable neutrino event rate in the 1 km 2 neutrino detector. Other PWNe can emit TeV γ-rays on the level of a few percent of that observed from the Crab Nebula

  1. FACT. Energy spectrum of the Crab Nebula

    Temme, Fabian; Einecke, Sabrina; Buss, Jens [TU Dortmund, Experimental Physics 5, Otto-Hahn-Str.4, 44221 Dortmund (Germany); Collaboration: FACT-Collaboration

    2016-07-01

    The First G-APD Cherenkov Telescope is the first Imaging Air Cherenkov Telescope which uses silicon photon detectors (G-APDs aka SiPM) as photo sensors. With more than four years of operation, FACT proved an application of SiPMs is suitable for the field of ground-based gamma-ray astronomy. Due to the stable flux at TeV energies, the Crab Nebula is handled as a ''standard candle'' in Cherenkov astronomy. The analysis of its energy spectrum and comparison with other experiments, allows to evaluate the performance of FACT. A modern analysis chain, based on data stream handling and multivariate analysis methods was developed in close cooperation with the department of computer science at the TU Dortmund. In this talk, this analysis chain and its application are presented. Further to this, results, including the energy spectrum of the Crab Nebula, measured with FACT, are shown.

  2. Nebulae at keratoconus--the result after excimer laser removal.

    Fagerholm, P; Fitzsimmons, T; Ohman, L; Orndahl, M

    1993-12-01

    Ten patients underwent excimer laser ablation due to nebula formation at keratoconus. The nebulae interfered significantly with contact lens fit or wearing time. The mean follow-up time in these patients was 16.5 months. Following surgery all patients could be successfully fitted with a contact lens and thereby obtain good visual acuity. Furthermore, contact lens wearing time was 8 hours or more in all cases. In 2 patients the nebulae recurred but were successfully retreated.

  3. Astrophysics of gaseous nebulae and active galactic nuclei

    Osterbrock, D.E.

    1989-01-01

    A graduate-level text and reference book on gaseous nebulae and the emission regions in Seyfert galaxies, quasars, and other types of active galactic nuclei (AGN) is presented. The topics discussed include: photoionization equilibrium, thermal equilibrium, calculation of emitted spectrum, comparison of theory with observations, internal dynamics of gaseous nebulae, interstellar dust, regions in the galactic context, planetary nebulae, nova and supernova remnants, diagnostics and physics of AGN, observational results on AGN

  4. Nebula observations. Catalogues and archive of photoplates

    Shlyapnikov, A. A.; Smirnova, M. A.; Elizarova, N. V.

    2017-12-01

    A process of data systematization based on "Academician G.A. Shajn's Plan" for studying the Galaxy structure related to nebula observations is considered. The creation of digital versions of catalogues of observations and publications is described, as well as their presentation in HTML, VOTable and AJS formats and basic principles of work in the interactive application of International Virtual Observatory the Aladin Sky Atlas.

  5. Multiband observations of the Crab Nebula

    Krassilchtchikov, A M; Bykov, A M; Castelletti, G M; Dubner, G M; Kargaltsev, O Yu; Pavlov, G G

    2017-01-01

    Results of simultaneous imaging of the Crab Nebula in the radio (JVLA), optical ( HST ), and X-ray ( Chandra ) bands are presented. The images show a variety of small-scale structures, including wisps mainly located to the north-west of the pulsar and knots forming a ring-like structure associated with the termination shock of the pulsar wind. The locations of the structures in different bands do not coincide with each other. (paper)

  6. Environmental impact study of Orion Nebula dust

    Cardelli, J.A.; Clayton, G.C.

    1988-01-01

    In this paper, new high-quality extinction curves are presented for Theta-1 Ori A, C, and D, and Theta-2 Ori A and B, over the wavelength range 3300-6000 A. These are coupled with near-infrared and ultraviolet data to produce extinction curves from 0.12 to 3.5 microns. The Orion Nebula region is interesting in that most of the known processes of dust-grain growth, processing, and destruction may be operating nearly simultaneously in close proximity to one another. Each of these processes is considered with respect to the observed extinction curves and environmental conditions in the Orion Nebula and its associated molecular cloud. Plausible grain populations are fit to the observed extinction curves. A good fit to the average Theta Ori extinction curve can be obtained with: (1) a combination of larger than normal silicate grains produced through coagulation and accretion; (2) evaporation of volatile mantles; and (3) a reduction in the column density of small (smaller than 0.01 micron) grains responsible for the bump and far-ultraviolet extinction through differential acceleration due to radiation pressure and possible evaporation. It seems plausible to explain the observed peculiar extinction in the Orion Nebula simply by environmental effects on otherwise normal grains. 59 references

  7. of Planetary Nebulae III. NGC 6781

    Hugo E. Schwarz

    2006-01-01

    Full Text Available Continuing our series of papers on the three-dimensional (3D structures and accurate distances to Planetary Nebulae (PNe, we present our study of the planetary nebula NGC6781. For this object we construct a 3D photoionization model and, using the constraints provided by observational data from the literature we determine the detailed 3D structure of the nebula, the physical parameters of the ionizing source and the first precise distance. The procedure consists in simultaneously fitting all the observed emission line morphologies, integrated intensities and the two-dimensional (2D density map from the [SII] (sulfur II line ratios to the parameters generated by the model, and in an iterative way obtain the best fit for the central star parameters and the distance to NGC6781, obtaining values of 950±143 pc (parsec – astronomic distance unit and 385 LΘ (solar luminosity for the distance and luminosity of the central star respectively. Using theoretical evolutionary tracks of intermediate and low mass stars, we derive the mass of the central star of NGC6781 and its progenitor to be 0.60±0.03MΘ (solar mass and 1.5±0.5MΘ respectively.

  8. 3He Abundances in Planetary Nebulae

    Guzman-Ramirez, Lizette

    2017-10-01

    Determination of the 3He isotope is important to many fields of astrophysics, including stellar evolution, chemical evolution, and cosmology. The isotope is produced in stars which evolve through the planetary nebula phase. Planetary nebulae are the final evolutionary phase of low- and intermediate-mass stars, where the extensive mass lost by the star on the asymptotic giant branch is ionised by the emerging white dwarf. This ejecta quickly disperses and merges with the surrounding ISM. 3He abundances in planetary nebulae have been derived from the hyperfine transition of the ionised 3He, 3He+, at the radio rest frequency 8.665 GHz. 3He abundances in PNe can help test models of the chemical evolution of the Galaxy. Many hours have been put into trying to detect this line, using telescopes like the Effelsberg 100m dish of the Max Planck Institute for Radio Astronomy, the National Radio Astronomy Observatory (NRAO) 140-foot telescope, the NRAO Very Large Array, the Arecibo antenna, the Green Bank Telescope, and only just recently, the Deep Space Station 63 antenna from the Madrid Deep Space Communications Complex.

  9. A PHOTOMETRICALLY AND MORPHOLOGICALLY VARIABLE INFRARED NEBULA IN L483

    Connelley, Michael S.; Hodapp, Klaus W.; Fuller, Gary A.

    2009-01-01

    We present narrow and broad K-band observations of the Class 0/I source IRAS 18148-0440 that span 17 years. The infrared nebula associated with this protostar in the L483 dark cloud is both morphologically and photometrically variable on a timescale of only a few months. This nebula appears to be an infrared analog to other well known optically visible variable nebulae associated with young stars, such as Hubble's Variable Nebula. Along with Cepheus A, this is one of the first large variable nebulae to be found that is only visible in the infrared. The variability of this nebula is most likely due to changing illumination of the cloud rather than any motion of the structure in the nebula. Both morphological and photometric changes are observed on a timescale only a few times longer than the light crossing time of the nebula, suggesting very rapid intrinsic changes in the illumination of the nebula. Our narrowband observations also found that H 2 knots are found nearly twice as far to the east of the source as to its west, and that H 2 emission extends farther east of the source than the previously known CO outflow.

  10. Influence of stellar duplicity on the form of planetary nebulae

    Kolesnik, I.G.; Pilyugin, L.S.

    1986-01-01

    Formation of planetary nebulae's spatial structures is considered. Simple expression for angular distribution of density in planetary nebulae is obtained. Bipolar structures are formed effectively in binary systems in which the velocity of the expanding shell around the main star is smaller than the orbital velocity of the satellite. Masses of satellites lie in the range 0.1-0.4Msub(sun). Theoretical isophotal contour map for the model of the planetary nebula NGC 3587 is consistent with observational data. It is shown that central stars of planetary nebulae are usually binary systems

  11. Proto-planetary nebulae. I. The extreme bipolar nebulae M2-9 and M1-91

    Goodrich, R.W.

    1991-01-01

    Results are presented on a long-slit optical spectroscopy measurements of the prototype bipolar planetary nebula M2-9 and the M1-91 bipolar nebula, performed in order to determine the nature of the morphology of the wings of these two nebulae. It is concluded that the overall bipolar morphologies of these nebulae might be due to the orbital motions of binaries, with the orbital angular momentum vector defining the axis of the nebula. Secondary symmetries in the nebulae, such as the point-symmetric knots in M1-91, could be due to other symmetries, such as the rotation axis of one of the individual stars or the polar axis of the accretion disk. 39 refs

  12. The Orion Nebula: The Jewel in the Sword

    2001-01-01

    -Res - JPEG: 2273 x 2784 pix - 976k] Caption : PR Photo 03d/01 shows a small section of the observational data (in one infrared spectral band only, here reproduced in B/W) on which PR Photo 03a/01 is based. The field is centred on one of the famous Orion silhouette disks (Orion 114-426) (it is located approximately halfway between the centre and the right edge of PR Photo 03c/01 ). The dusty disk itself is seen edge-on as a dark streak against the background emission of the Orion Nebula, while the bright fuzzy patches on either side betray the presence of the embedded parent star that illuminates tenuous collections of dust above its north and south poles to create these small reflection nebulae. Recent HST studies suggest that the very young Orion 114-426 disk - that is thirty times bigger than our present-day Solar System - may already be showing signs of forming its own proto-planetary system. Technical information about this photo is available below. It is even possible to see disks of dust and gas surrounding a few of the young stars, as silhouettes in projection against the bright background of the nebula. Many of these disks are very small and usually only seen on images obtained with the Hubble Space Telescope (HST) [2]. However, under the best seeing conditions on Paranal, the sharpness of VLT images at infrared wavelengths approaches that of the HST in this spectral band, revealing some of these disks, as shown in PR Photo 03d/01 . Indeed, the theoretical image sharpness of the 8.2-m VLT is more than three times better than that of the 2.4-m HST. Thus, the VLT will soon yield images of small regions with even higher resolution by means of the High-Resolution Near-Infrared Camera (CONICA) and the Nasmyth Adaptive Optics System (NAOS) that will compensate the smearing effect introduced by the turbulence in the atmosphere. Later on, extremely sharp images will be obtained when all four VLT telescopes are combined to form the Very Large Telescope Interferometer (VLTI

  13. Abundances of the planetary nebula Hu 1-2

    Pottasch, [No Value; Hyung, S; Aller, LH; Beintema, DA; Bernard-Salas, J; Feibelman, WA; Klockner, HR

    The ISO and IUE spectra of the "elliptical" nebula Hu 1-2 are presented. These spectra are combined with new, high resolution spectra in the visual wavelength region to obtain a complete, extinction corrected, spectrum. The chemical composition of the nebula is then calculated and compared to

  14. Abundances of planetary nebulae NGC 7662 and NGC 6741

    Pottasch, [No Value; Beintema, DA; Salas, JB; Feibelman, WA

    2001-01-01

    The ISO and IUE spectra of the elliptical nebulae NGC7662 and NGC6741 are presented. These spectra are combined with the spectra in the visual wavelength region to obtain a complete, extinction corrected, spectrum. The chemical composition of the nebulae is then calculated and compared to previous

  15. Starlight excitation of permitted lines in the Orion Nebula

    Grandi, S.A.

    1975-01-01

    From an idealized model of the Orion Nebula and from an analysis of line ratios it is shown that direct starlight excitation of the permitted O I line dominates over recombination and Lyman line fluorescence. The line strengths predicted by this mechanism agree reasonably well with those observed in the Orion Nebula. The application of direct starlight excitation to other ions is also discussed

  16. A comparison of Hipparcos parallaxes with planetary nebulae spectroscopic distances

    Pottasch, [No Value; Acker, A

    1998-01-01

    The Hipparcos satellite has measured the parallax of a small sample of planetary nebulae. In this paper we consider the results for 3 planetary nebulae (PN) for which spectroscopic distances have also been determined from stellar gravities. These gravities in turn have been derived from profile

  17. Abundances of neon, sulfur, and argon in planetary nebulae

    Beck, S.C.; Lacy, J.H.; Townes, C.H.; Geballe, T.R.; Baas, F.

    1981-01-01

    Infrared observations of [Ne II], [S IV], and [Ar III] are used with optical observations to discuss the abundances of Ne, S, and Ar in 18 planetary nebulae. In addition, infrared observations of 18 other nebulae are presented. The derived abundances of S and Ar are each slightly enhanced relative to previous studies

  18. The Planetary Nebula Spectrograph : The green light for galaxy kinematics

    Douglas, NG; Arnaboldi, M; Freeman, KC; Kuijken, K; Merrifield, MR; Romanowsky, AJ; Taylor, K; Capaccioli, M; Axelrod, T; Gilmozzi, R; Hart, J; Bloxham, G; Jones, D

    2002-01-01

    Planetary nebulae (PNe) are now well established as probes of galaxy dynamics and as standard candles in distance determinations. Motivated by the need to improve the efficiency of planetary nebulae searches and the speed with which their radial velocities are determined, a dedicated instrument-the

  19. Galactic planetary nebulae and evolution of their nuclei

    Khromov, G.S.

    1980-01-01

    The galactic system of planetary nebulae is investigated using previously constructed distance scale and kinematics data. A strong effect of observational selection is established, which has the consequence that with increasing distance, ever brighter and younger objects are observed. More accurate determinations of the spatial and surface densities of the planetary nebulae system are obtained as well as a new estimate of their total number in the Galaxy, which is approximately 200,000. New estimates are also made of the masses of the nebulae, the absolute magnitudes of the nebulae and their nuclei, and other physical parameters of these objects. The spatial and kinematic characteristics of the planetary nebulae indicate that they are objects of the old type I population. It is possible that their remote ancestors are main sequence stars of the type B8-A5-F or as yet unidentified objects of the same galactic subsystem

  20. Young planetary nebula with OH molecules - NGC 6302

    Payne, H.E.; Phillips, J.A.; Terzian, Y.

    1988-01-01

    The results of a sensitive survey of planetary nebulae in all four ground-state OH lines are reported. The results confirm that evolved planetary nebulas are not OH sources in general. However, one interesting object was not detected: an OH 1612 MHz maser in the young planetary nebula NGC 6302. This nebula may be in a brief evolutionary stage, similar to the young and compact planetary nebula Vy 2-2, where OH has already been detected. In addition, the results of further observations of NGC 6302 are reported, including VLA observations of the 1612 MHz line and continuum emission and detections of rotationally excited OH lines at 5-cm wavelength in absorption. 28 references

  1. Effects of mass and metallicity upon planetary nebula formation

    Papp, K.A.; Purton, C.R.; Kwok, S.

    1983-01-01

    We construct a parameterized function which describes the possible dependence of planetary nebula formation upon metal abundance and stellar mass. Data on galaxies in the Local Group compared with predictions made from the parameterized function indicate that heavy element abundance is the principal agent influencing the formation of planetary nebulae; stars which are rich in heavy elements are the progenitors of planetary nebulae. Our analysis, when compared with the observations, argues for a modest degree of pre-enrichment in a few of the sample galaxies. The heavy element dependence of planetary nebula formation also accounts for the deficit of planetary nebula in the nuclei of NGC 221 and NGC 224, and in the bulge of our Galaxy

  2. The effects of mass and metallicity upon planetary nebula formation

    Papp, K. A.; Purton, C. R.; Kwok, S.

    1983-05-01

    A parameterized function is constructed which describes the possible dependence of planetary nebula formation upon metal abundance and stellar mass. Data on galaxies in the Local Group compared with predictions made from the parameterized function indicate that heavy element abundance is the principal agent influencing the formation of planetary nebulae; stars which are rich in heavy elements are the progenitors of planetary nebulae. This analysis, when compared with the observations, argues for a modest degree of pre-enrichment in a few of the sample galaxies. The heavy element dependence of planetary nebula formation also accounts for the deficit of planetary nebulae in the nuclei of NGC 221 and NGC 224, and in the bulge of our Galaxy.

  3. Aerodynamics of solid bodies in the solar nebula

    Weidenschilling, S J [Carnegie Institution of Washington, D.C. (USA). Dept. of Terrestrial Magnetism

    1977-07-01

    On a centrally condensed solar nebula, the pressure gradient in the gas causes the nebula to rotate more slowly than the free orbital velocity. Drag forces cause the orbits of solid bodies to decay. Their motions have been investigated analytically and numerically for all applicable drag laws. The maximum radial velocity developed is independent of the drag law, and insensitive to the nebular mass. Results are presented for a variety of model nebulae. Radial velocities depend strongly on particle size, reaching values of the order of 10/sup 4/ cm/s for metre-sized objects. Possible consequences include: mixing of solid matter with the solar nebula on short timescales, collisions leading to rapid accumulation of planetesimals, fractionation of bodies by size or density, and production of regions of anomalous composition in the solar nebula.

  4. Relation between radius and expansion velocity in planetary nebulae

    Chu, Y.H.; Kwitter, K.B.; Kaler, J.B.

    1984-01-01

    The expansion velocity-radius (R-V) relation for planetary nebulae is examined using the existing measurements of expansion velocities and recent calculations of radii. It is found that some of the previously alleged R-V relations for PN are not convincingly established. The scatter in the R-V plots may be due largely to stratification of ions in individual nebulae and to heterogeneity in the planetary nebula population. In addition, from new echelle/CCD observations of planetary nebulae, it is found that spatial information is essential in deriving the internal kinematic properties. Future investigations of R-V relations should be pursued separately for groups of planetaries with similar physical properties, and they should employ observations of appropriate low excitation lines in order to measure the expansion velocity at the surface of the nebula. 26 references

  5. A large bubble around the Crab Nebula

    Romani, Roger W.; Reach, William T.; Koo, Bon Chul; Heiles, Carl

    1990-01-01

    IRAS and 21 cm observations of the interstellar medium around the Crab nebula show evidence of a large bubble surrounded by a partial shell. If located at the canonical 2 kpc distance of the Crab pulsar, the shell is estimated to have a radius of about 90 pc and to contain about 50,000 solar masses of swept-up gas. The way in which interior conditions of this bubble can have important implications for observations of the Crab are described, and the fashion in which presupernova evolution of the pulsar progenitor has affected its local environment is described.

  6. Electrodynamic coupling between pulsars and surrounding nebulae

    Dobrowolny, M [Consiglio Nazionale delle Ricerche, Frascati (Italy). Lab. per il Plasma nello Spazio; L' Aquila Univ. (Italy). Istituto di Fisica); Ferrari, A [Cambridge Univ. (UK). Inst. of Astronomy; Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica; Turin Univ. (Italy). Istituto di Fisica)

    1976-02-01

    In this work a study is presented of collective plasma processes by which pulsars can energetically support young supernova remnants. We show that many of the observed features of the Crab Nebula can be adequately interpreted in terms of a parametric interaction between the low-frequency electromagnetic wave emitted by the pulsar in the oblique rotator model and a relativistic wind of charged particle leaking from the pulsar's inner magnetosphere. In particular we show that there is a relativistic parametric resonant coupling of the strong wave with electrostatic and electromagnetic modes.

  7. ELEMENT MASSES IN THE CRAB NEBULA

    Sibley, Adam R.; Katz, Andrea M.; Satterfield, Timothy J.; Vanderveer, Steven J.; MacAlpine, Gordon M. [Department of Physics and Astronomy, Trinity University, San Antonio, TX 78212 (United States)

    2016-10-01

    Using our previously published element abundance or mass-fraction distributions in the Crab Nebula, we derived actual mass distributions and estimates for overall nebular masses of hydrogen, helium, carbon, nitrogen, oxygen and sulfur. As with the previous work, computations were carried out for photoionization models involving constant hydrogen density and also constant nuclear density. In addition, employing new flux measurements for [Ni ii]  λ 7378, along with combined photoionization models and analytic computations, a nickel abundance distribution was mapped and a nebular stable nickel mass estimate was derived.

  8. Planetary nebulae and the interstellar medium

    Aller, L. H.

    1986-01-01

    In addition to available published data on planetary nebulae (PN), some 40 objects largely concentrated towards the galactic center and anticenter regions were included. All were observed with the Lick 3(sup m) telescope and image tube scanner. Abundances of C, N, O, Ne, Cl, and Ar were determined by a procedure in which theoretical models were used to obtain ionization correction factors (ICF). Of the 106 PN, 66 are N-rich and 40 are N-poor. There appear to be no significant differences between the average compositions in the solar neighborhood and the average taken over the entire observable portion of the galaxy.

  9. Orion infrared nebula/molecular cloud

    Zuckerman, B.; Palmer, P.

    1975-01-01

    Observational and theoretical studies of the Orion Nebula and the associated molecular clouds have greatly increased our understanding of this and other regions in which star formation is taking place. Fundamental questions remain unanswered; and in this Letter we address three of them: (1) the chemical composition of the molecular cloud, (2) its internal motions, and (3) the role of magnetic fields in its evolution. We show that the gas phase chemistry and internal motions in one part of the cloud are distinctly different from those in the rest of the cloud, and two recent estimates of the magnetic field strengths are very uncertain. (auth)

  10. On planetary nebulae as sources of carbon dust: Infrared emission from planetary nebulae of the galactic halo

    Dinerstein, H.L.; Lester, D.F.

    1990-01-01

    Researchers examine here the characteristics of the infrared emission from the four planetary nebulae which are believed on the basis of their low overall metallicities to belong to the halo population. These nebulae are of particular interest because they are the most metal-poor ionized nebulae known in our Galaxy, and offer the opportunity to probe possible dependences of the dust properties on nebular composition. Researchers present fluxes extracted from co-addition of the IRAS data, as well as ground-based near infrared measurements. Each of the four halo objects, including the planetary nebula in the globular cluster M15, is detected in at least one infrared band. Researchers compare the estimated infrared excesses of these nebulae (IRE, the ratio of measured infrared power to the power available in the form of resonantly-trapped Lyman alpha photons) to those of disk planetary nebulae with similar densities but more normal abundances. Three of the halo planetaries have IRE values similar to those of the disk nebulae, despite the fact that their Fe- and Si-peak gas phase abundances are factors of 10 to 100 lower. However, these halo nebulae have normal or elevated C/H ratios, due to nuclear processing and mixing in their red giant progenitors. Unlike the other halo planetaries, DDDM1 is deficient in carbon as well as in the other light metals. This nebula has a substantially lower IRE than the other halo planetaries, and may be truly dust efficient. Researchers suggest that the deficiency is due to a lack of the raw material for producing carbon-based grains, and that the main bulk constituent of the dust in these planetary nebulae is carbon

  11. Physics and chemistry of the solar nebula.

    Lunine, J I

    1997-06-01

    The solar system is thought to have begun in a flattened disk of gas and dust referred to traditionally as the solar nebula. Such a construct seems to be a natural product of the collapse of dense parts of giant molecular clouds, the vast star-forming regions that pepper the Milky Way and other galaxies. Gravitational, magnetic and thermal forces within the solar nebula forced a gradual evolution of mass toward the center (where the sun formed) and angular momentum (borne by a small fraction of the mass) toward the outer more distant regions of the disk. This evolution was accompanied by heating and a strong temperature contrast from the hot, inner regions to the cold, more remote parts of the disk. The resulting chemistry in the disk determined the initial distribution of organic matter in the planets; most of the reduced carbon species, in condensed form, were located beyond the asteroid belt (the 'outer' solar system). The Earth could have received much of its inventory of pre-biological material from comets and other icy fragments of the process of planetary formation in the outer solar system.

  12. Dark nebulae, dark lanes, and dust belts

    Cooke, Antony

    2012-01-01

    As probably the only book of its type, this work is aimed at the observer who wants to spend time with something less conventional than the usual fare. Because we usually see objects in space by means of illumination of one kind or another, it has become routine to see them only in these terms. However, part of almost everything that we see is the defining dimension of dark shading, or even the complete obscuration of entire regions in space. Thus this book is focused on everything dark in space: those dark voids in the stellar fabric that mystified astronomers of old; the dark lanes reported in many star clusters; the magical dust belts or dusty regions that have given so many galaxies their identities; the great swirling 'folds' that we associate with bright nebulae; the small dark feature detectable even in some planetary nebulae; and more. Many observers pay scant attention to dark objects and details. Perhaps they are insufficiently aware of them or of the viewing potential they hold, but also it may be...

  13. Theoretical investigation into the existence of molecules in planetary nebulae

    Carlson, W.J.

    1980-01-01

    Calculations of chemical kinetic equilibrium molecular abundances in the neutral regions of planetary nebulae are presented. The development of these abundances during the expansion of the nebula is calculated. The physical parameters in the neutral regions following the formation of the nebula by the ejection of the envelope of a long peiod variable star have been taken from available dynamical models. Similarly, the temperature and luminosity of the central star as a function of time have been taken from available theoretical calculations. The thermal equilibrium has been solved independently. The temperatures in the shell and later in the condensations which develop are in the range from 30 to 250 K. Number densities range from 10 7 for the youngest model calculated to 2 x 10 4 for neutral condensations in a 10,000 year old nebula. It is shown that, for a typical nebula containing 0.2 Msub solar, molecules are expected to be the dominant form for only a short period early in the expansion phase. Subsequently, the condensations are not sufficiently optically thick to permit the continued existence of a preponderance of molecules. The molecular abundances in the later models are similar to those in diffuse interstellar clouds. The expectation arising from those results is that little molecular material will be injected into the interstellar medium by planetary nebulae. There is, however, a remarkable resemblance between the conditions in the model calculated at very early stages of the expansion and conditions deduced from observations for proto-planetary nebulae

  14. Spectrophotometry of ring nebulae around Wolf-Rayet stars

    Kwitter, K.B.

    1979-01-01

    Spectrophotometric observations of four ring nebulae surrounding population I Wolf-Rayet (WN) stars have been obtained, and four additional filamentary nebulae in order to determine the physical conditions and chemical abundances in these objects. It was concluded that the ring nebulae are enriched in nitrogen and helium as a result of contamination of the ambient interstellar medium by the helium- and nitrogen-rich wind from the central Wolf-Rayet star. Of the additional nebulae studied, two were found to be Peimbert Type I planetary nebulae, overabundant in nitrogen and helium due to mixing of CNO processed material into the parent envelope prior to ejection. One of the remaining objects, a shell around an Oef star, is found to have normal abundances; the other, a small H II region around an early Be star, also exhibits normal abundances. It was attempted to interpret the ring nebulae and the Oef shell as interstellar bubbles, according to recent theory; it met with varying degrees of success. For two of the ring nebulae, the fraction of nebular mass contributed by the central star can be estimated from published stellar abundances. It was found that in these two cases, the stellar wind has provided less than 10% of the observed nebular mass

  15. Induced massive star formation in the trifid nebula?

    Cernicharo; Lefloch; Cox; Cesarsky; Esteban; Yusef-Zadeh; Mendez; Acosta-Pulido; Garcia Lopez RJ; Heras

    1998-10-16

    The Trifid nebula is a young (10(5) years) galactic HII region where several protostellar sources have been detected with the infrared space observatory. The sources are massive (17 to 60 solar masses) and are associated with molecular gas condensations at the edges or inside the nebula. They appear to be in an early evolutionary stage and may represent the most recent generation of stars in the Trifid. These sources range from dense, apparently still inactive cores to more evolved sources, undergoing violent mass ejection episodes, including a source that powers an optical jet. These observations suggest that the protostellar sources may have evolved by induced star formation in the Trifid nebula.

  16. X-ray Emission from the Guitar Nebula

    Romani, Roger W.; Cordes, James M.; Yadigaroglu, I. -A.

    1997-01-01

    We have detected weak soft X-ray emission from the Pulsar Wind Nebula trailing the high velocity star PSR 2224+65 (the `Guitar Nebula'). This X-ray flux gives evidence of \\gamma~10^7 eV particles in the pulsar wind and constrains the properties of the post-shock flow. The X-ray emission is most easily understood if the shocked pulsar wind is partly confined in the nebula and if magnetic fields in this zone can grow to near equipartition values.

  17. X-Ray Emission from the Guitar Nebula

    Romani, Roger W.; Cordes, James M.; Yadigaroglu, I.-A.

    1997-01-01

    We have detected weak soft X-ray emission from the pulsar wind nebula trailing the high-velocity star PSR 2224+65 (the "Guitar Nebula"). This X-ray flux gives evidence of gamma approximately 10(exp 7) eV particles in the pulsar wind and constrains the properties of the postshock flow. The X-ray emission is most easily understood if the shocked pulsar wind is partly confined in the nebula and if magnetic fields in this zone can grow to near-equipartition values.

  18. Radio and infrared observations of the faint nebula GM24

    Rodriguez, L F; Roth, M; Tapia, M; Canto, J; Persi, P; Ferrari-Toniolo, M

    1986-02-01

    The faint nebulosity GM24=PP85 listed by Parsamian and Petrosian (1979) was observed at infrared (1-10 ..mu..m) and radio (6 cm and CO line) wavelengths in the vicinity of the CO hot spot reported by Torrelles et al. (1983). The radio continuum (6 cm) emission from a spherically symmetrical HII region was detected with the Very Large Array. Its position coincides with the brightest part of the visible nebulosity and a 1-4 ..mu..m emission peak. Their infrared maps made at the Observatorio Astronomico Nacional de San Pedro Martir, show two additional (1-10 ..mu..m) peaks located at distances approx. 30 arc sec from the compact HII region, all surrounded by extended near infrared (1-4 ..mu..m) emission. A detailed CO (J=1 ..-->.. 0) map of the whole molecular cloud was also obtained with the University of Texas Millimeter - Wave Telescope. Their results are interpreted in terms of the recent formation of three massive stars, one of which, having developed an HII region, is at a slightly later phase of its evolution. The extended near infrared emission may arise in a reflection nebula similar to NGC 7538-Irs 9. 4 references.

  19. An investigation of the Carina Nebula

    Brooks, Kate J.

    2000-10-01

    It is well known that the radiation fields and stellar winds of massive stars can drastically affect the physical conditions, structure and chemistry of the giant molecular cloud (GMC) from which they formed. It is also thought that massive stars are at least partly responsible for triggering further star formation within a GMC. The details of this interaction, however, are not well understood and additional detailed study of massive star-forming regions is needed. This study has focused on a multi-wavelength investigation of the Carina Nebula. This is a spectacular massive star-forming region that contains two of the most massive star clusters in our galaxy, Trumpler 14 and Trumpler 16, and one of the most massive stars known -- η Car. The goal of this study has been to obtain information on the molecular gas, ionized gas and photodissociation regions (PDRs) from a collection of instruments which have the highest angular resolution and sensitivity available to date. The Mopra Telescope and the Swedish-ESO Submillimeter Telescope (SEST) were used to obtain a series of molecular line observations of the GMC between 150 and 230 GHz. Observations of H110α recombination-line emission at 4.874 GHz and the related continuum emission were obtained with the Australia Telescope Compact Array and used to study the ionized gas associated with the two HII regions, Car I and Car II. H2 1--0 S(1) (2.12 microns) and Brγ (2.16 microns) observations using the University of New South Wales Infrared Fabry-Perot (UNSWIRF) and 3.29 micron narrow-band observations obtained with the SPIREX/Abu thermal infrared camera were used to study the PDRs on the surface of molecular clumps in the Keyhole region, a dark optical feature in the vicinity of η Car. The results of these observations provide detailed information on the excitation conditions, kinematics and morphology of regions within the HII region/molecular cloud complex of the Carina Nebula. In addition, the results confirm that

  20. Classification of ISO SWS 01 spectra of proto-planetary nebulae: a search for precursors of planetary nebulae with [WR] central stars

    Szczerba, R.; Stasi{ń}ska, G.; Siódmiak, N.; Górny, S. K.

    2002-01-01

    We have analyzed ISO SWS 01 observations for 61 proto-planetary nebulae candidates and classified their spectra according to their dominant chemistry. On the basis of our classification and the more general classification of SWS 01 spectra by Kraemer et al. (2002) we discuss the connection between proto-planetary nebulae candidates and planetary nebulae, with emphasis on possible precursors of planetary nebulae with [WR] central stars.

  1. A symmetric bipolar nebula around MWC 922.

    Tuthill, P G; Lloyd, J P

    2007-04-13

    We report regular and symmetric structure around dust-enshrouded Be star MWC 922 obtained with infrared imaging. Biconical lobes that appear nearly square in aspect, forming this "Red Square" nebula, are crossed by a series of rungs that terminate in bright knots or "vortices," and an equatorial dark band crossing the core delimits twin hyperbolic arcs. The intricate yet cleanly constructed forms that comprise the skeleton of the object argue for minimal perturbation from global turbulent or chaotic effects. We also report the presence of a linear comb structure, which may arise from optically projected shadows of a periodic feature in the inner regions, such as corrugations in the rim of a circumstellar disk. The sequence of nested polar rings draws comparison with the triple-ring system seen around the only naked-eye supernova in recent history: SN1987A.

  2. ISO Spectroscopy of Proto-Planetary Nebulae

    Hrivnak, Bruce J.

    2000-01-01

    The goal of this program was to determine the chemical properties of the dust shells around protoplanetary nebulae (PPNs) through a study of their short-wavelength (6-45 micron) infrared spectra. PPNs are evolved stars in transition from the asymptotic giant branch to the planetary nebula stages. Spectral features in the 10 to 20 gm region indicate the chemical nature (oxygen- or carbon-rich), and the strengths of the features relate to the physical properties of the shells. A few bright carbon-rich PPNs have been observed to show PAH features and an unidentified 21 micron emission feature. We used the Infrared Space Observatory (ISO) to observe a sample of IRAS sources that have the expected properties of PPNs and for which we have accurate positions. Some of these have optical counterparts (proposal SWSPPN01) and some do not (SWSPPN02). We had previously observed these from the ground with near-infrared photometry and, for those with visible counterparts, visible photometry and spectroscopy, which we have combined with these new ISO data in the interpretation of the spectra. We have completed a study of the unidentified emission feature at 21 micron in eight sources. We find the shape of the feature to be the same in all of the sources, with no evidence of any substructure. The ratio of the emission peak to continuum ranges from 0.13 to 1.30. We have completed a study of seven PPNs and two other carbon-rich objects for which we had obtained ISO 2-45 micron observations. The unidentified emission features at 21 and 30 micron were detected in six sources, including four new detections of the 30 micron feature. This previously unresolved 30 micron feature was resolved and found to consist of a broad feature peaking at 27.2 micron (the "30 micron" feature) and a narrower feature peaking at 25.5 micron (the "26 micron" feature). This new 26 micron feature is detected in eight sources and is particularly strong in IRAS Z02229+6208 and 16594-4656. The unidentified

  3. Chemical enrichment in halo planetary nebulae

    Torres-Peimbert, S; Rayo, J F; Peimbert, M [Universidad Nacional Autonoma de Mexico, Mexico City. Inst. de Astronomia

    1981-01-01

    Photoelectric spectrophotometry of emission lines in the 3400-7400 A region is presented for the planetary nebulae 108-76/sup 0/1(BB1). From these observations the relative abundances of H, He, C, N, O and Ne are derived. The abundances of the halo PN (BB1, H4-1 and K648) are compared to those predicted by stellar evolution theory under the assumption that the envelope has the chemical composition of the matter located between the H burning shell and the surface. The observed He/H and C/O values are higher than predicted which implies that halo PN contain matter from deeper layers than the H burning shell. Furthermore, the O/Ar, N/Ar and Ne/Ar values in halo PN are higher than in the solar neighbourhood, at least part of this enrichment is produced by the PN progenitors.

  4. Distinguishing between symbiotic stars and planetary nebulae

    Iłkiewicz, K.; Mikołajewska, J.

    2017-10-01

    Context. The number of known symbiotic stars (SySt) is still significantly lower than their predicted population. One of the main problems in finding the total population of SySt is the fact that their spectrum can be confused with other objects, such as planetary nebulae (PNe) or dense H II regions. This problem is reinforced by the fact that in a significant fraction of established SySt the emission lines used to distinguish them from other objects are not present. Aims: We aim at finding new diagnostic diagrams that could help separate SySt from PNe. Additionally, we examine a known sample of extragalactic PNe for candidate SySt. Methods: We employed emission line fluxes of known SySt and PNe from the literature. Results: We found that among the forbidden lines in the optical region of spectrum, only the [O III] and [N II] lines can be used as a tool for distinguishing between SySt and PNe, which is consistent with the fact that they have the highest critical densities. The most useful diagnostic that we propose is based on He I lines, which are more common and stronger in SySt than forbidden lines. All these useful diagnostic diagrams are electron density indicators that better distinguish PNe and ionized symbiotic nebulae. Moreover, we found six new candidate SySt in the Large Magellanic Cloud and one in M 81. If confirmed, the candidate in M 81 would be the farthest known SySt thus far.

  5. Nucleation and condensation in the primitive solar nebula

    Cameron, A.G.W.; Fegley, M.B.

    1982-01-01

    It is pointed out that the primitive solar nebula may be modeled using the frictionally induced transport theory of Lynden-Bell and Pringle (1974) if the principal frictional mechanism within the nebula is turbulent viscosity. The present investigation is concerned with the construction of a model of a section of the primitive solar nebula as a basis for the study of nucleation and condensation processes within this section. The construction involves a relatively simple application of the Lynden-Bell and Pringle theory subject to steady mass flow conditions. The calculations which are conducted in connection with the investigation indicate that by the time the gas in the primitive solar nebula has become sufficiently supercooled to nucleate condensation centers, several different compounds, including the magnesium silicates forsterite and enstatite (MgSiO 3 ), will probably be able to condense on the growing condensation center

  6. The carbon budget in the outer solar nebula

    Simonelli, D.P.; Pollack, J.B.; Mckay, C.P.; Reynolds, R.T.; Summers, A.L.

    1989-01-01

    The compositional contrast between the giant-planet satellites and the significantly rockier Pluto/Charon system is indicative of different formation mechanisms; cosmic abundance calculations, in conjunction with an assumption of the Pluto/Charon system's direct formation from solar nebula condensates, strongly suggest that most of the carbon in the outer solar nebula was in CO form, in keeping with both the inheritance from the dense molecular clouds in the interstellar medium, and/or the Lewis and Prinn (1980) kinetic-inhibition model of solar nebula chemistry. Laboratory studies of carbonaceous chondrites and Comet Halley flyby studies suggest that condensed organic material, rather than elemental carbon, is the most likely candidate for the small percentage of the carbon-bearing solid in the outer solar nebula. 71 refs

  7. From red giant to planetary nebula - Dust, asymmetry, and polarization

    Johnson, J.J.; Jones, T.J.

    1991-01-01

    The polarization characteristics of stars in the stages of evolution from red giant to planetary nebula are investigated. Polarization is found to be a characteristic of the majority of these stars. The maximum observed polarization increases with age as the star evolves up the asymptotic giant branch (AGB) to the protoplanetary nebula phase, where the polarization reaches a maximum. The polarization then decreases as the star further evolves into a planetary nebula. These results indicate that aspherical mass loss is likely to be a continual feature of the late stages of stellar evolution, maintaining a clear continuity throughout the life of a star from the moment it first develops a measurable dust shell. The aspherical morphology seen in planetary nebulae has its origin in an intrinsic property of the star that is present at least as early as its arrival at the base of the AGB. 77 refs

  8. The [NeIV] Lines in High Excitation Gaseous Nebulae.

    Aller, L H

    1970-04-01

    The "forbidden" lines of three times ionized neon are among the most precious indicators of electron temperature and excitation. They are also predicted to be among the strongest lines observed in the far ultraviolet spectra of high excitation nebulae.

  9. Possible mass distributions in the nebulae of other solar systems

    Brown, W.K.

    1987-01-01

    The supernova shell fragmentation model of solar system formation - previously shown to be successful in describing the mass distribution of our solar system - is used to calculate the mass distributions of other solar nebulae. (Auth.)

  10. Pulsar Wind Nebulae and Cosmic Rays: A Bedtime Story

    Weinstein, A.

    2014-11-15

    The role pulsar wind nebulae play in producing our locally observed cosmic ray spectrum remains murky, yet intriguing. Pulsar wind nebulae are born and evolve in conjunction with SNRs, which are favored sites of Galactic cosmic ray acceleration. As a result they frequently complicate interpretation of the gamma-ray emission seen from SNRs. However, pulsar wind nebulae may also contribute directly to the local cosmic ray spectrum, particularly the leptonic component. This paper reviews the current thinking on pulsar wind nebulae and their connection to cosmic ray production from an observational perspective. It also considers how both future technologies and new ways of analyzing existing data can help us to better address the relevant theoretical questions. A number of key points will be illustrated with recent results from the VHE (E > 100 GeV) gamma-ray observatory VERITAS.

  11. Statistical and physical study of one-sided planetary nebulae.

    Ali, A.; El-Nawawy, M. S.; Pfleiderer, J.

    The authors have investigated the spatial orientation of one-sided planetary nebulae. Most of them if not all are interacting with the interstellar medium. Seventy percent of the nebulae in the sample have inclination angles larger than 45° to the Galactic plane and 30% of the inclination angles are less than 45°. Most of the selected objects are old, evolved planetary nebulae with large dimensions, and not far away from the Galactic plane. Seventy-five percent of the objects are within 160 pc from the Galactic plane. The enhanced concavity arc can be explained physically as a result of the 'planetary nebulae-interstellar matter' interaction. The authors discuss the possible effect of the interstellar magnetic field in the concavity regions.

  12. On the evolution of central stars of planetary nebulae

    Yahel, R.Z.

    1977-01-01

    The evolution of nuclei of planetary nebulae has been calculated from the end of the ejection stage that produces the nebulae to the white dwarf stage. The structure of the central star is in agreement with the general picture of Finzi (1973) about the mass ejection from the progenitors of planetary nebulae. It has been found that in order to obtain evolutionary track consistent with the Harman-Seaton track (O'Dell, 1968) one has to assume that the masses of the nuclei stars are less than approximately 0.7 solar masses. The calculated evolutionary time scale of the central stars of planetary nebulae is approximately 2 x 10 4 yr. This time scale is negatively correlated with the stellar mass: the heavier the stellar mass, the shorter the evolutionary time scale. (Auth.)

  13. Chemical composition of planetary nebulae : Including ISO results

    Pottasch, [No Value; Beintema, DA; Salas, JB; Feibelman, WA; Henney, WJ; Franco, J; Martos, M; Pena, M

    2002-01-01

    The method of determining abundances using Infrared Space Observatory spectra is discussed. The results for seven planetary nebula are given. Using these data, a preliminary discussion of their evolution is given.

  14. Polarimetric evidence against a collimated outflow in the Horsehead Nebula

    Warren-Smith, R F; Gledhill, T M; Scarrott, S M

    1985-08-01

    Imaging polarimetry of the Horsehead Nebula in Orion shows that the 'jaw' region of the nebula, which includes a proposed collimated flow from a highly reddened star B33-6, is illuminated by a distant source, sigma Orionis, and not by B33-6. The polarization pattern also shows features which suggest the presence of magnetically aligned dust grains in the surrounding medium. The possible structure of the aligning field is discussed.

  15. Complex molecules in the Orion Kleinmann-Low nebula

    Despois D.

    2014-02-01

    Full Text Available In the framework of the delivery to the early Earth of extraterrestrial molecules, we have studied complex molecular species toward the Orion Kleinmann-Low nebula. This nebula is rich in molecules as well as in nascent stars and planetary systems. We focus here on HCOOCH3, CH3OCH3 and deuterated methanol. Upper limits on species of prebiotic interest like glycine were also obtained.

  16. Interpretation of the [ClIII] Lines in Gaseous Nebulae.

    Aller, L H; Czyzak, S J; Walker, M F; Krueger, T K

    1970-05-01

    The intensity ratio of the green lambdalambda5517 and 5537 lines of [ClIII] serves as an indicatrix of the electron density in many gaseous nebulae whose spectra can be observed with an image converter. Quantitative interpretation of the line ratio requires accurate values of the collisional strengths and transition probabilities. With improved values of these parameters we have revised electron densities for a number of nebulae; the results seem to be in good accord with those derived from other criteria.

  17. The Boomerang Nebula - The Coldest Region of the Universe

    Sahai, Raghvendra; Nyman, Lars-Ake

    1997-01-01

    In this letter, we report such observations of the Boomerang Nebula which show it to be a unique object, consisiting of an ultra-cold and extremely massive molecular envolope, expanding at very high speed. The extreeme physical characteristics of the Boomerang Nebula reported here have never been seen before in any AGB or post-AGB object, and should spur new theoretical and obesrvational efforts to understand the nature of the mass-loss processes occurring during later stellar evolution.

  18. Distribution of mass in the planetary system and solar nebulae

    Weidenschilling, S J [Carnegie Institution of Washington, D.C. (USA). Dept. of Terrestrial Magnetism

    1977-09-01

    A model 'solar nebula' is constructed by adding the solar complement of light elements to each planet, using recent models of planetary compositions. Uncertainties in this approach are estimated. The computed surface density varies approximately as rsup(-3/2). Mercury, Mars and the asteroid belt are anomalously low in mass, but processes exist which would preferentially remove matter from these regions. Planetary masses and compositions are generally consistent with a monotonic density distribution in the primordial solar nebula.

  19. Pulsar Wind Nebulae Created by Fast-Moving Pulsars

    Kargaltsev, Oleg; Pavlov, George G.; Klingler, Noel; Rangelov, Blagoy

    2017-01-01

    We review multiwavelength properties of pulsar wind nebulae (PWNe) created by supersonically moving pulsars and the effects of pulsar motion on the PWN morphologies and the ambient medium. Supersonic pulsar wind nebulae (SPWNe) are characterized by bow-shaped shocks around the pulsar and/or cometary tails filled with the shocked pulsar wind. In the past several years significant advances in SPWN studies have been made in deep observations with the Chandra and XMM-Newton X-ray Observatories as...

  20. PROBING THE ROSETTE NEBULA STELLAR BUBBLE WITH FARADAY ROTATION

    Savage, Allison H.; Spangler, Steven R.; Fischer, Patrick D. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States)

    2013-03-01

    We report the results of Faraday rotation measurements of 23 background radio sources whose lines of sight pass through or close to the Rosette Nebula. We made linear polarization measurements with the Karl G. Jansky Very Large Array (VLA) at frequencies of 4.4 GHz, 4.9 GHz, and 7.6 GHz. We find the background Galactic contribution to the rotation measure in this part of the sky to be +147 rad m{sup -2}. Sources whose lines of sight pass through the nebula have an excess rotation measure of 50-750 rad m{sup -2}, which we attribute to the plasma shell of the Rosette Nebula. We consider two simple plasma shell models and how they reproduce the magnitude and sign of the rotation measure, and its dependence on distance from the center of the nebula. These two models represent different modes of interaction of the Rosette Nebula star cluster with the surrounding interstellar medium. Both can reproduce the magnitude and spatial extent of the rotation measure enhancement, given plausible free parameters. We contend that the model based on a stellar bubble more closely reproduces the observed dependence of rotation measure on distance from the center of the nebula.

  1. The Nature of the Stingray Nebula from Radio Observations

    Harvey-Smith, Lisa; Hardwick, Jennifer A.; De Marco, Orsola; Parthasarathy, Mudumba; Gonidakis, Ioannis; Akhter, Shaila; Cunningham, Maria; Green, James A.

    2018-06-01

    We have analysed the full suite of Australia Telescope Compact Array data for the Stingray planetary nebula. Data were taken in the 4- to 23-GHz range of radio frequencies between 1991 and 2016. The radio flux density of the nebula generally declined during that period, but between 2013 and 2016 it shows signs of halting that decline. We produced the first spatially resolved radio images of the Stingray nebula from data taken in 2005. A ring structure, which appears to be associated with the ring seen in HST images, was visible. In addition, we found a narrow extension to the radio emission towards the eastern and western edges of the nebula. We derived the emission measure of the nebula - this decreased between 1992 and 2011, suggesting that the nebula is undergoing recombination. The radio spectral index is broadly consistent with a free-free emission mechanism, however a single data point hints that a steeper spectral index has possibly emerged since 2013, which could indicate the presence of synchrotron emission. If a non-thermal component component has emerged, such as one associated with a region that is launching a jet or outflow, we predict that it would intensify in the years to come.

  2. Featured Image: A Detailed Look at the Crab Nebula

    Kohler, Susanna

    2017-07-01

    Planning on watching fireworks tomorrow? Heres an astronomical firework to help you start the celebrations! A new study has stunningly detailed the Crab Nebula (click for a closer look), a nebula 6,500 light-years away thought to have been formedby a supernova explosion and the subsequent ultrarelativistic wind emitted by the pulsar at its heart. Led by Gloria Dubner (University of Buenos Aires), the authors of this study obtained new observations of the Crab Nebula from five different telescopes. They compiled these observations to compare the details of the nebulas structure across different wavelengths, which allowedthem to learnabout the sources of various features within the nebula. In the images above, thetop left shows the 3 GHz data from the Very Large Array (radio). Moving clockise, the radio data (shown in red) is composited with: infrared data from Spitzer Space Telescope, optical continuum from Hubble Space Telescope, 500-nm optical datafrom Hubble, and ultraviolet data from XMM-Newton. The final two images are of the nebula center, and they are composites of the radio imagewith X-ray data from Chandra and near-infrared data from Hubble. To read more about what Dubner and collaborators learned (and to see more spectacular images!), check out the paper below.CitationG. Dubner et al 2017 ApJ 840 82. doi:10.3847/1538-4357/aa6983

  3. Reflecting reflection in supervision

    Lystbæk, Christian Tang

    associated with reflection and an exploration of alternative conceptions that view reflection within the context of settings which have a more group- and team-based orientation. Drawing on an action research project on health care supervision, the paper questions whether we should reject earlier views...... of reflection, rehabilitate them in order to capture broader connotations or move to new ways of regarding reflection that are more in keeping with not only reflective but also emotive, normative and formative views on supervision. The paper presents a critical perspective on supervision that challenge...... the current reflective paradigm I supervision and relate this to emotive, normative and formative views supervision. The paper is relevant for Nordic educational research into the supervision and guidance...

  4. The Asymmetric Nebula Surrounding the Extreme Red Supergiant VY Canis Majoris

    Smith, Nathan; Humphreys, Roberta M.; Davidson, Kris; Gehrz, Robert D.; Schuster, M. T.; Krautter, Joachim

    2001-02-01

    We present HST/WFPC2 images plus ground-based infrared images and photometry of the very luminous OH/IR star VY Canis Majoris. Our WFPC2 data show a complex distribution of knots and filamentary arcs in the asymmetric reflection nebula around the obscured central star. The reflection arcs may result from multiple, asymmetric ejection episodes due to localized events on VY CMa's surface. Such events probably involve magnetic fields and convection, by analogy with solar activity. Surface photometry indicates that the star may have experienced enhanced mass loss over the past 1000 yr. We also demonstrate that the apparent asymmetry of the nebula results from a combination of high extinction and backscattering by dust grains. Thermal-infrared images reveal a more symmetric distribution, elongated along a nearly east-west direction. VY CMa probably has a flattened disklike distribution of dust with a northeast-southwest polar axis and may be experiencing activity analogous to solar prominences. The presence of an axis of symmetry raises interesting questions for a star the size of Saturn's orbit. Magnetic fields and surface activity may play an important role in VY CMa's mass-loss history. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  5. Mixing and Transport in the Solar Nebula

    Boss, Alan P.

    2003-01-01

    Boss & Vanhala (2000, 2001) prepared reviews of triggered collapse and injection models, using Prudence Foster's finite differences code at very high spatial resolution (440 x 1440 cells) to demonstrate the convergence of the R-T fingers in triggered injection models. A two dimensional hydrodynamical calculation with unprecedentedly high spatial resolution (960 x 2880 zones, or almost 3 million grid points) demonstrated that it suitable shock front can both trigger the collapse of an otherwise stable presolar cloud, and inject shock front particles into the collapsing cloud through the formation of what become Rayleigh-Taylor fingers of compressed fluid layers falling into the gravitational potential well of the growing protostar. These calculations suggest that heterogeneity derived from these R-T fingers will persist down to the scale of their injection onto the surface of the solar nebula. Haghighipour developed a numerical code capable of calculating the orbital evolution of dust grains of varied sizes in a gaseous nebula, subject to Epstein and Stokes drag as well as the self-gravity of the disk. In collaboration with the PI and George W. Wetherill, Haghighipour has been involved in development of a new idea on the possibility of rapid formation of ice giant planets via the disk instability mechanism. Haghighipour studied the stability of a five-body system consisting of the Sun and four protoplanets by numerically integrating their equations of motions. Using Levison and Duncan s SWIFT integrator, Haghighipour showed that, depending on the orbital parameters of the bodies, such a system can be stable for 0.1-10 Myr. Time periods of 1 Myr or more are long enough to be consistent with the time scale proposed for the formation of giant planets by the disk instability mechanism and the photoevaporation of the gaseous envelopes of the outermost protoplanets by a nearby OB star, resulting in the formation of ice giant planets. The PI has used his three dimensional

  6. Signatures of Chemical Evolution in Protostellar Nebulae

    Nuth, Joseph A., III; Johnson, Natasha

    2011-01-01

    A decade ago observers began to take serious notice of the presence of crystalline silicate grains in the dust flowing away from some comets. While crystallinity had been seen in such objects previously, starting with the recognitions by Campins and Ryan (1990) that the 10 micron feature of Comet Halley resembled that of the mineral forsterite, most such observations were either ignored or dismissed as no path to explain such crystalline grains was available in the literature. When it was first suggested that an outward flow must be present to carry annealed silicate grains from the innermost regions of the Solar Nebula out to the regions where comets could form (Nuth, 1999; 2001) this suggestion was also dismissed because no such transport mechanism was known at the time. Since then not only have new models of nebular dynamics demonstrated the reality of long distance outward transport (Ciesla, 2007; 2008; 2009) but examination of older models (Boss, 2004) showed that such transport had been present but had gone unrecognized for many years. The most unassailable evidence for outward nebular transport came with the return of the Stardust samples from Comet Wild2, a Kuiper-belt comet that contained micron-scale grains of high temperature minerals resembling the Calcium-Aluminum Inclusions found in primitive meteorites (Zolensky et aI., 2006) that formed at T > 1400K. Now that outward transport in protostellar nebulae has been firmly established, a re-examination of its consequences for nebular gas is in order that takes into account both the factors that regulate both the outward flow as well as those that likely control the chemical composition of the gas. Laboratory studies of surface catalyzed reactions suggest that a trend toward more highly reduced carbon and nitrogen compounds in the gas phase should be correlated with a general increase in the crystallinity of the dust (Nuth et aI., 2000), but is such a trend actually observable? Unlike the Fischer-Tropsch or

  7. Model for the filamentary structure in the pleiades reflection nebulosity

    Arny, T.

    1977-01-01

    It is suggested that the filamentary structure in the Pleiades reflection nebula is caused by shearing of dust clumps in an interstellar cloud moving through the star cluster. Radiation pressure flattens a dust clump and causes it to flow around a star, forming a shell. The anisotropy of the radiation field shears clumps into long streamers

  8. Pinwheel Nebula around WR 98a.

    Monnier; Tuthill; Danchi

    1999-11-10

    We present the first near-infrared images of the dusty Wolf-Rayet star WR 98a. Aperture-masking interferometry has been utilized to recover images at the diffraction limit of the Keck I telescope, less, similar50 mas at 2.2 µm. Multiepoch observations spanning about 1 yr have resolved the dust shell into a "pinwheel" nebula, the second example of a new class of dust shell first discovered around WR 104 by Tuthill, Monnier, & Danchi. Interpreting the collimated dust outflow in terms of an interacting winds model, the binary orbital parameters and apparent wind speed are derived: a period of 565+/-50 days, a viewing angle of 35&j0;+/-6 degrees from the pole, and a wind speed of 99+/-23 mas yr-1. This period is consistent with a possible approximately 588 day periodicity in the infrared light curve, linking the photometric variation to the binary orbit. Important implications for binary stellar evolution are discussed by identifying WR 104 and WR 98a as members of a class of massive, short-period binaries whose orbits were circularized during a previous red supergiant phase. The current component separation in each system is similar to the diameter of a red supergiant, which indicates that the supergiant phase was likely terminated by Roche lobe overflow, leading to the present Wolf-Rayet stage.

  9. Planetary Nebulae and How to Observe Them

    Griffiths, Martin

    2012-01-01

    Astronomers' Observing Guides provide up-to-date information for amateur astronomers who want to know all about what is it they are observing. This is the basis of the first part of the book. The second part details observing techniques for practical astronomers, working with a range of different instruments. Planetary Nebulae and How to Observe Them is intended for amateur astronomers who want to concentrate on one of the most beautiful classes of astronomical objects in the sky. This book will help the observer to see these celestial phenomena using telescopes of various apertures. As a Sun-like star reaches the end of its life, its hydrogen fuel starts to run out. It collapses until helium nuclei begin nuclear fusion, whereupon the star begins to pulsate, each pulsation throwing off a layer of the star's atmosphere. Eventually the atmosphere has all been ejected as an expanding cloud of gas, the star's core is exposed and ultraviolet photons cause the shell of gas to glow brilliantly - that's planetary ...

  10. Scaled Eagle Nebula Experiments on NIF

    Pound, Marc W. [Univ. of Maryland, College Park, MD (United States)

    2017-03-28

    We performed scaled laboratory experiments at the National Ignition Facility laser to assess models for the creation of pillar structures in star-forming clouds of molecular hydrogen, in particular the famous Pillars of the Eagle Nebula. Because pillars typically point towards nearby bright ultraviolet stars, sustained directional illumination appears to be critical to pillar formation. The experiments mock up illumination from a cluster of ultraviolet-emitting stars, using a novel long duration (30--60 ns), directional, laser-driven x-ray source consisting of multiple radiation cavities illuminated in series. Our pillar models are assessed using the morphology of the Eagle Pillars observed with the Hubble Space Telescope, and measurements of column density and velocity in Eagle Pillar II obtained at the BIMA and CARMA millimeter wave facilities. In the first experiments we assess a shielding model for pillar formation. The experimental data suggest that a shielding pillar can match the observed morphology of Eagle Pillar II, and the observed Pillar II column density and velocity, if augmented by late time cometary growth.

  11. Planetary nebulae: 20 years of Hubble inquiry

    Balick, Bruce

    2012-08-01

    The Hubble Space Telescope has served the critical roles of microscope and movie camera in the past 20 years of research on planetary nebulae (``PNe''). We have glimpsed the details of the evolving structures of neutral and ionized post-AGB objects, built ingenious heuristic models that mimic these structures, and constrained most of the relevant physical processes with careful observations and interpretation. We have searched for close physical binary stars with spatial resolution ~50 AU at 1 AU, located jets emerging from the nucleus at speeds up to 2000 km s-1 and matched newly discovered molecular and X-ray emission regions to physical substructures in order to better understand how stellar winds and ionizing radiation interact to form the lovely symmetries that are observed. Ultraviolet spectra of CNO in PNe help to uncover how stars process deep inside AGB stars with unstable nuclear burning zones. HST broadband imaging has been at the forefront of uncovering surprisingly complex wind morphologies produced at the tip of the AGB, and has led to an increasing realization of the potentially vital roles of close binary stars and emerging magnetic fields in shaping stellar winds.

  12. Continuous emission from the gaseous nebula beyond the Lyman limit

    Bolgova, G.T.; Khromov, G.S.

    1975-01-01

    Models of spherically-symmetric isothermic hydrogen nebula with an exciting star in the centre are considered. Spectra and energies of diffuse radiation of nebula and of direct radiation of its kernel are calculated in the Lyman continuum for the external boundary of the object. The spectrum of the diffuse radiation is shown to be to a great extent invariant in relation to all parameters of models except for Tsub(e). The total loss in energy of Lsub(c)-radiation of kernel through the external border of the ionized nebula, amounts to 20-30% in the average even at a considerable optical thickness of the object tausub(0). The greater part of this energy is transferred via direct ionizing radiation, though the relative contribution of the diffuse Lsub(c)-radiation of nebula reaches 30% at low temperatures of the exciting star and at large tausub(0). The results of this work may be applied to calculating the energy balance of the star-nebula system, the heating of dust particles and ionization of the neighbouring interstellar medium, and also for determining the conditions of observation of the far ultra-violet radiation of similar objects

  13. A turbulent two-phase flow model for nebula flows

    Champney, J.M.; Cuzzi, J.N.

    1990-01-01

    A new and very efficient turbulent two-phase flow numericaly model is described to analyze the environment of a protoplanetary nebula at a stage prior to the formation of planets. Focus is on settling processes of dust particles in flattened gaseous nebulae. The model employs a perturbation technique to improve the accuracy of the numerical simulations of such flows where small variations of physical quantities occur over large distance ranges. The particles are allowed to be diffused by gas turbulence in addition to settling under gravity. Their diffusion coefficients is related to the gas turbulent viscosity by the non-dimensional Schmidt number. The gas turbulent viscosity is determined by the means of the eddy viscosity hypothesis that assumes the Reynolds stress tensor proportional to the mean strain rate tensor. Zero- and two-equation turbulence models are employed. Modeling assumptions are detailed and discussed. The numerical model is shown to reproduce an existing analytical solution for the settling process of particles in an inviscid nebula. Results of nebula flows are presented taking into account turbulence effects of nebula flows. Diffusion processes are found to control the settling of particles. 24 refs

  14. Spectral and interferometric observation of four emission nebulas

    Lozinskaya, T.A.; Klement'eva, A.Yu.; Zhukov, G.V.; Shenavrin, V.I.

    1975-01-01

    Results of spectrophotometric and interferometric observations of four emission nebulae are presented; electron temperature Te and electron density Ne are estimated; mean beam velocities and parameters of the internal motion in the nebylae are determined. The following objects have been investigated: 1) a bright compact nebulae of unknown nature 2.5 in size which is identified with the non-thermal radiosource G6.4-0.5 in the region W28; 2) nebulae RCW171 5' in size which is identified with the radiosource G23.1+0.6; 3) the nebulae Simeiz 34/Sharpless 261/d 1950 =6sup(h)05sup(m), sigma 1950 =+15 deg 49'; its diameter is approximately 30 an extensive complex of bright emission fibres in the nebulae Swan, which are partially projected into a possible remainder of the outburst of a supernova W63; L 1950 =20sup(h)17sup(m); S 1950 =45 deg 30' its diameter is approximately 1 deg 5

  15. On the injection of relativistic particles into the Crab Nebula

    Shklovskij, I.S.

    1977-01-01

    It is shown that a flux of relativistic electrons from the NP 0532 pulsar magnetosphere, responsible for its synchrotron emission, cannot provide the necessary energy pumping to the Crab Nebula. A conclusion is reached that such a pumping can be effectuated by a flow of relativistic electrons leaving the NP 0532 magnetosphere at small pitch angles and giving therefore no appreciable contribution to the synchrotron emission of the pulsar. An interpretation of the Crab Nebula synchrotron spectrum is given on the assumption of secular ''softening'' of the energy spectrum of the relativistic electrons injected into the Nebula. A possibility of explanation of the observed rapid variability of some features in the central part of the Nebula by ejection of free - neutron - rich dense gas clouds from the pulsar surface during ''starquakes'' is discussed. The clouds of rather dense (nsub(e) approximately 10 7 cm -3 ) plasma, thus formed at about 10 13 cm from pulsar, will be accelerated up to relativistic velocities by the pressure of the magneto-dipole radiation of NP 0532 and will deform the magnetic field in the inner part (R 17 cm) of the Crab Nebula, that is the cause of the variability observed. In this case, favourable conditions for the acceleration of the particles in the cloud up to relativistic energies are realized; that may be an additional source of injection

  16. Gamma rays and neutrinos from the Crab Nebula produced by pulsar accelerated nuclei

    Bednarek, W.; Protheroe, R. J.

    1997-01-01

    We investigate the consequences of the acceleration of heavy nuclei (e.g. iron nuclei) by the Crab pulsar. Accelerated nuclei can photodisintegrate in collisions with soft photons produced in the pulsar's outer gap, injecting energetic neutrons which decay either inside or outside the Crab Nebula. The protons from neutron decay inside the nebula are trapped by the Crab Nebula magnetic field, and accumulate inside the nebula producing gamma-rays and neutrinos in collisions with the matter in t...

  17. Abundance in the planetary nebulae NGC 6537 and He2-111

    Pottasch, [No Value; Beintema, DA; Feibelman, WA

    2000-01-01

    The ISO and IUE spectra of the bipolar planetary nebulae NGC 6537 and He2-111 are presented. These spectra are combined with the spectrum in the visual wavelength region from the nebulae to obtain a complete spectrum that is corrected for extinction. The chemical abundance of the nebulae is then

  18. Lifetime of the solar nebula constrained by meteorite paleomagnetism.

    Wang, Huapei; Weiss, Benjamin P; Bai, Xue-Ning; Downey, Brynna G; Wang, Jun; Wang, Jiajun; Suavet, Clément; Fu, Roger R; Zucolotto, Maria E

    2017-02-10

    A key stage in planet formation is the evolution of a gaseous and magnetized solar nebula. However, the lifetime of the nebular magnetic field and nebula are poorly constrained. We present paleomagnetic analyses of volcanic angrites demonstrating that they formed in a near-zero magnetic field (nebula field, and likely the nebular gas, had dispersed by this time. This sets the time scale for formation of the gas giants and planet migration. Furthermore, it supports formation of chondrules after 4563.5 million years ago by non-nebular processes like planetesimal collisions. The core dynamo on the angrite parent body did not initiate until about 4 to 11 million years after solar system formation. Copyright © 2017, American Association for the Advancement of Science.

  19. Abundance of carbon and magnesium in the Orion nebula

    Perinotto, M.; Patriarchi, P.

    1980-01-01

    The Orion nebula has been observed in two positions with IUE (International Ultraviolet Explorer) in the low-resolution mode (approx.7 A) and in the spectral range 1150--3200 A. Emission lines of C II], C III], [O II], and He I have been measured and used to determine what is probably the first reliable abundance of carbon in H II regions. The logarithmic total abundance of carbon is found to be 8.4 close to the solar value. In contrast with the situation in the planetary nebula of similar excitation, IC 418, where the resonance Mg II lambda2800 line is observed to be relatively strong, in the Orion nebula the lambda2800 line is not detectable. an upper limit for the magnesium abundance of the order of 10 times smaller than in the Sun is suggested

  20. The surprising Crab pulsar and its nebula: a review.

    Bühler, R; Blandford, R

    2014-06-01

    The Crab nebula and its pulsar (referred to together as 'the Crab') have historically played a central role in astrophysics. True to this legacy, several unique discoveries have been made recently. The Crab was found to emit gamma-ray pulsations up to energies of 400 GeV, beyond what was previously expected from pulsars. Strong gamma-ray flares, of durations of a few days, were discovered from within the nebula, while the source was previously expected to be stable in flux on these time scales. Here we review these intriguing and suggestive developments. In this context we give an overview of the observational properties of the Crab and our current understanding of pulsars and their nebulae.

  1. Facilitating NASA Earth Science Data Processing Using Nebula Cloud Computing

    Chen, A.; Pham, L.; Kempler, S.; Theobald, M.; Esfandiari, A.; Campino, J.; Vollmer, B.; Lynnes, C.

    2011-12-01

    Cloud Computing technology has been used to offer high-performance and low-cost computing and storage resources for both scientific problems and business services. Several cloud computing services have been implemented in the commercial arena, e.g. Amazon's EC2 & S3, Microsoft's Azure, and Google App Engine. There are also some research and application programs being launched in academia and governments to utilize Cloud Computing. NASA launched the Nebula Cloud Computing platform in 2008, which is an Infrastructure as a Service (IaaS) to deliver on-demand distributed virtual computers. Nebula users can receive required computing resources as a fully outsourced service. NASA Goddard Earth Science Data and Information Service Center (GES DISC) migrated several GES DISC's applications to the Nebula as a proof of concept, including: a) The Simple, Scalable, Script-based Science Processor for Measurements (S4PM) for processing scientific data; b) the Atmospheric Infrared Sounder (AIRS) data process workflow for processing AIRS raw data; and c) the GES-DISC Interactive Online Visualization ANd aNalysis Infrastructure (GIOVANNI) for online access to, analysis, and visualization of Earth science data. This work aims to evaluate the practicability and adaptability of the Nebula. The initial work focused on the AIRS data process workflow to evaluate the Nebula. The AIRS data process workflow consists of a series of algorithms being used to process raw AIRS level 0 data and output AIRS level 2 geophysical retrievals. Migrating the entire workflow to the Nebula platform is challenging, but practicable. After installing several supporting libraries and the processing code itself, the workflow is able to process AIRS data in a similar fashion to its current (non-cloud) configuration. We compared the performance of processing 2 days of AIRS level 0 data through level 2 using a Nebula virtual computer and a local Linux computer. The result shows that Nebula has significantly

  2. The solar nebula redox state as recorded by most reduced chondrules of five primitive chondrites

    Johnson, M.C.; Harvard Univ., Cambridge, MA

    1986-01-01

    Mafic minerals in the most reduced chondrules of five primitive meteorites were analyzed with an electron microprobe to determine the lower limit on their FeO contents. The accuracy obtained was +-0.01 weight percent FeO. The thermodynamic relationship between mole fraction FeSiO 3 and pO 2 of the ambient nebular gas at the time of mineral equilibration was established, and was used to infer the local O/H ratio of the nebular gas during chondrule formation. The lowest ferrosilite compositions reflected equilibration at 1500K with a gas 2-18 times more oxidizing than a gas of solar composition. Olivines in low-FeO UOC chondrules are uniformly more FeO-rich than coexisting pyroxenes. This descrepancy suggests that a significant change in the O/H ratio of the nebular gas occurred between the time of olivine and pyroxene crystallization in the region of the nebula where UOCs formed. Mineral compositions in the chondrules of two C2 chondrites studied suggest they formed in a more homogeneous region of the nebula than the UOCs. (author)

  3. IRAS 06562-0337, The Ironclad Nebula: A New Young Star Cluster

    Alves, D.R.; Hoard, D.W.; Rodgers, B.

    1998-01-01

    IRAS 06562-0337 has been the recent subject of a classic debate: is it a proto endash planetary nebula or a young stellar object? We present the first 2 μm image of IRAS 06562-0337, which reveals an extended diffuse nebula containing approximately 70 stars inside a 30 double-prime radius around a bright, possibly resolved, central object. The derived stellar luminosity function is consistent with that expected from a single coeval population, and the brightness of the nebulosity is consistent with the predicted flux of unresolved low-mass stars. The stars and nebulosity are spatially coincident with strong CO line emission. We therefore identify IRAS 06562-0337 as a new young star cluster embedded in its placental molecular cloud. The central object is likely a Herbig Be star, M ∼ 20 M circle-dot , which may be seen in reflection. We present medium-resolution high signal-to-noise ratio 1997 epoch optical spectra of the central object. Comparison with previously published spectra shows new evidence for time-variable permitted and forbidden line emission, including Si ii, Fe ii, [Fe ii], and [O i]. We suggest that the origin is a dynamic stellar wind in the extended stratified atmosphere of the massive central star in IRAS 06562-0337. copyright copyright 1998. The American Astronomical Society

  4. GBT, VLA Team Up to Produce New Image of Orion Nebula

    2002-01-01

    Combining the best features of the National Science Foundation's (NSF) new Robert C. Byrd Green Bank Telescope (GBT) in West Virginia with those of the NSF's Very Large Array (VLA) in New Mexico, astronomers have produced a vastly improved radio image of the Orion Nebula and developed a valuable new technique for studying star formation and other astrophysical processes. GBT-VLA Image of Orion Nebula GBT-VLA Image of Orion Nebula "Our GBT image of the Orion Nebula is the best image ever produced with a single-dish radio telescope and it illustrates the superb performance of this new telescope," said Debra Shepherd, of the National Radio Astronomy Observatory (NRAO) in Socorro, NM. "By combining data from the GBT with that from the VLA, we get an image that reflects reality far better than images from the separate telescopes could do," she added. Shepherd worked with Ron Maddalena from NRAO in Green Bank and Joe McMullin, from NRAO in Socorro. The astronomers presented their work to the American Astronomical Society meeting in Washington, DC. Single-dish radio telescopes such as the GBT, dedicated in 2000, are able to capture the large-scale structure of objects such as the Orion Nebula. However, they are unable to discern the fine detail revealed by multi-antenna arrays such as the VLA. Conversely, a VLA-like array is "blind" to the larger-scale structures. Combining the data from both types of radio telescopes to produce an image showing both large- and small-scale structures in the same celestial object has been a difficult, laborious task. "We are developing new observing techniques and software to make this task much easier and quicker," said McMullin. "We now have achieved in hours what used to take months or even longer to do, but we are producing an observational tool that will allow astronomers to make much higher-fidelity images that will greatly improve our understanding of several important astronomical processes," McMullin added. For this observation

  5. Layers in the Central Orion Nebula

    O'Dell, C. R.

    2018-04-01

    The existence of multiple layers in the inner Orion Nebula has been revealed using data from an Atlas of spectra at 2″ and 12 km s-1 resolution. These data were sometimes grouped over Samples of 10″×10″ to produce high Signal to Noise spectra and sometimes grouped into sequences of pseudo-slit Spectra of 12{^''.}8 - 39″width for high spatial resolution studies. Multiple velocity systems were found: V_{MIF} traces the Main Ionization Front (MIF), V_{scat} arises from back-scattering of V_{MIF} emission by particles in the background Photon Dissociation Region (PDR), V_{low} is an ionized layer in front of the MIF and if it is the source of the stellar absorption lines seen in the Trapezium stars, it must lie between the foreground Veil and those stars, V_{new,[O III]} may represent ionized gas evaporating from the Veil away from the observer. There are features such as the Bright Bar where variations of velocities are due to changing tilts of the MIF, but velocity changes above about 25″ arise from variations in velocity of the background PDR. In a region 25″ ENE of the Orion-S Cloud one finds dramatic changes in the [O III] components, including the signals from the V_{low,[O III]} and V_{MIF,[O III]} becoming equal, indicating shadowing of gas from stellar photons of >24.6 eV. This feature is also seen in areas to the west and south of the Orion-S Cloud.

  6. Asymmetric Planetary Nebulae VI: the conference summary

    De Marco, O.

    2014-04-01

    The Asymmetric Planetary Nebulae conference series, now in its sixth edition, aims to resolve the shaping mechanism of PN. Eighty percent of PN have non spherical shapes and during this conference the last nails in the coffin of single stars models for non spherical PN have been put. Binary theories abound but observational tests are lagging. The highlight of APN6 has been the arrival of ALMA which allowed us to measure magnetic fields on AGB stars systematically. AGB star halos, with their spiral patterns are now connected to PPN and PN halos. New models give us hope that binary parameters may be decoded from these images. In the post-AGB and pre-PN evolutionary phase the naked post-AGB stars present us with an increasingly curious puzzle as complexity is added to the phenomenologies of objects in transition between the AGB and the central star regimes. Binary central stars continue to be detected, including the first detection of longer period binaries, however a binary fraction is still at large. Hydro models of binary interactions still fail to give us results, if we make an exception for the wider types of binary interactions. More promise is shown by analytical considerations and models driven by simpler, 1D simulations such as those carried out with the code MESA. Large community efforts have given us more homogeneous datasets which will yield results for years to come. Examples are the ChanPlaN and HerPlaNe collaborations that have been working with the Chandra and Herschel space telescopes, respectively. Finally, the new kid in town is the intermediate-luminosity optical transient, a new class of events that may have contributed to forming several peculiar PN and pre-PN.

  7. Do stellar and nebular abundances in the Cocoon nebula agree?

    García-Rojas, J.; Simón-Díaz, S.; Esteban, C.

    2015-05-01

    The Cocoon nebula is an apparently spherical Galactic HII region ionized by a single star (BD+46 3474). This nebula seems to be appropriate to investigate the chemical behavior of oxygen and other heavy elements from two different points of view: a detailed analysis of the chemical content of the ionized gas through nebular spectrophotometry and a detailed spectroscopic analysis of the spectrum of the ionizing star using the state-of-the-art stellar atmosphere modelling. In this poster we present the results from a set of high-quality observations, from 2m-4m class telescopes, including the optical spectrum of the ionizing star BD+46 3474, along with long-slit spatially resolved spectroscopy of the nebula. We have used state-of-the-art stellar atmosphere codes to determine stellar parameters and the chemical content of several heavy elements. Traditional nebular techniques along with updated atomic data have been used to compute gaseous abundances of O, N and S in the Cocoon nebula. Thanks to the low ionization degree of the nebula, we could determine total abundances directly from observable ions (no ionization correction factors were needed) for three of the analyzed elements (O, S, and N). The derived stellar and nebular abundances are compared and the influence of the possible presence of the so-called temperature fluctuations on the nebula is discussed. The results of this study are presented in more detail in García-Rojas, Simón-Díaz & Esteban 2014, A&A, 571, A93.

  8. Binarity and the Abundance Discrepancy Problem in Planetary Nebulae

    Corradi, Romano L. M.; García-Rojas, Jorge; Jones, David; Rodríguez-Gil, Pablo

    2015-04-01

    The discrepancy between abundances computed using optical recombination lines and collisionally excited lines is a major unresolved problem in nebular astrophysics. Here, we show that the largest abundance discrepancies are reached in planetary nebulae with close binary central stars. We illustrate this using deep spectroscopy of three nebulae with a post common-envelope (CE) binary star. Abell 46 and Ou 5 have O2+/H+ abundance discrepancy factors larger than 50, and as high as 300 in the inner regions of Abell 46. Abell 63 has a smaller discrepancy factor around 10, which is still above the typical values in ionized nebulae. Our spectroscopic analysis supports previous conclusions that, in addition to “standard” hot ({{T}e} ˜ 104 K) gas, there exists a colder ({{T}e} ˜ 103 K), ionized component that is highly enriched in heavy elements. These nebulae have low ionized masses, between 10-3 and 10-1 M⊙ depending on the adopted electron densities and temperatures. Since the much more massive red giant envelope is expected to be entirely ejected in the CE phase, the currently observed nebulae would be produced much later, during post-CE mass loss episodes when the envelope has already dispersed. These observations add constraints to the abundance discrepancy problem. We revise possible explanations. Some explanations are naturally linked to binarity such as, for instance, high-metallicity nova ejecta, but it is difficult at this stage to depict an evolutionary scenario consistent with all of the observed properties. We also introduce the hypothesis that these nebulae are the result of tidal destruction, accretion, and ejection of Jupiter-like planets.

  9. Excimer laser superficial keratectomy for proud nebulae in keratoconus.

    Moodaley, L; Liu, C; Woodward, E G; O'Brart, D; Muir, M K; Buckley, R

    1994-06-01

    Contact lens intolerance in keratoconus may be due to the formation of a proud nebula at or near the apex of the cone. Excimer laser superficial keratectomy was performed as an outpatients with proud nebulae as treatment patients with proud nebulae as treatment for their contact lens intolerance. The mean period of contact lens wear before the development of intolerance was 13.4 years (range 2 to 27 years). Following the development of intolerance, three patients abandoned contact lens wear in the affected eye while the remainder experienced a reduction in comfortable wearing time (mean = 3.75 hours; range: 0-14 hours). All patients had good potential Snellen visual acuity with a contact lens of 6/9 (nine eyes) and 6/12 (one eye). The proud nebulae were directly ablated with a 193 nm ArF excimer laser using a 1 mm diameter beam. Between 100-150 pulses were sufficient to ablate the raised area. Patients experienced no pain during the procedure and reported minimal discomfort postoperatively. In all cases flattening of the proud nebulae was achieved. Seven patients were able to resume regular contact lens wear (mean wearing time = 10.17 hours; range 8 to 16 hours). In three patients, resumption of contact lens wear was unsuccessful because of cone steepness. All patients achieved postoperative Snellen visual acuity of 6/12 or better with a contact lens. Four patients experienced a loss of one line in Snellen acuity. The mean follow up period was 8.3 months (range 2 to 17 months). Excimer laser superficial keratectomy is a useful technique for the treatment of contact lens intolerance caused by proud nebulae in patients with keratoconus. Penetrating keratoplasty is thus avoided.

  10. The blue supergiant MN18 and its bipolar circumstellar nebula

    Gvaramadze, V. V.; Kniazev, A. Y.; Bestenlehner, J. M.; Bodensteiner, J.; Langer, N.; Greiner, J.; Grebel, E. K.; Berdnikov, L. N.; Beletsky, Y.

    2015-11-01

    We report the results of spectrophotometric observations of the massive star MN18 revealed via discovery of a bipolar nebula around it with the Spitzer Space Telescope. Using the optical spectrum obtained with the Southern African Large Telescope, we classify this star as B1 Ia. The evolved status of MN18 is supported by the detection of nitrogen overabundance in the nebula, which implies that it is composed of processed material ejected by the star. We analysed the spectrum of MN18 by using the code CMFGEN, obtaining a stellar effective temperature of ≈21 kK. The star is highly reddened, E(B - V) ≈ 2 mag. Adopting an absolute visual magnitude of MV = -6.8 ± 0.5 (typical of B1 supergiants), MN18 has a luminosity of log L/L⊙ ≈ 5.42 ± 0.30, a mass-loss rate of ≈(2.8-4.5) × 10- 7 M⊙ yr- 1, and resides at a distance of ≈5.6^{+1.5} _{-1.2} kpc. We discuss the origin of the nebula around MN18 and compare it with similar nebulae produced by other blue supergiants in the Galaxy (Sher 25, HD 168625, [SBW2007] 1) and the Large Magellanic Cloud (Sk-69°202). The nitrogen abundances in these nebulae imply that blue supergiants can produce them from the main-sequence stage up to the pre-supernova stage. We also present a K-band spectrum of the candidate luminous blue variable MN56 (encircled by a ring-like nebula) and report the discovery of an OB star at ≈17 arcsec from MN18. The possible membership of MN18 and the OB star of the star cluster Lynga 3 is discussed.

  11. Experimental simulations of sulfide formation in the solar nebula.

    Lauretta, D S; Lodders, K; Fegley, B

    1997-07-18

    Sulfurization of meteoritic metal in H2S-H2 gas produced three different sulfides: monosulfide solid solution [(Fe,Ni)1-xS], pentlandite [(Fe,Ni)9-xS8], and a phosphorus-rich sulfide. The composition of the remnant metal was unchanged. These results are contrary to theoretical predictions that sulfide formation in the solar nebula produced troilite (FeS) and enriched the remaining metal in nickel. The experimental sulfides are chemically and morphologically similar to sulfide grains in the matrix of the Alais (class CI) carbonaceous chondrite, suggesting that these meteoritic sulfides may be condensates from the solar nebula.

  12. Particle Acceleration in Pulsar Wind Nebulae: PIC Modelling

    Sironi, Lorenzo; Cerutti, Benoît

    We discuss the role of PIC simulations in unveiling the origin of the emitting particles in PWNe. After describing the basics of the PIC technique, we summarize its implications for the quiescent and the flaring emission of the Crab Nebula, as a prototype of PWNe. A consensus seems to be emerging that, in addition to the standard scenario of particle acceleration via the Fermi process at the termination shock of the pulsar wind, magnetic reconnection in the wind, at the termination shock and in the Nebula plays a major role in powering the multi-wavelength signatures of PWNe.

  13. A radio search for planetary nebulae near the galactic center

    Isaacman, R.B.

    1980-01-01

    Because of galactic center is a hostile environment, and because planetaries are weak radio emitters, it is not clear a priori that one expects to detect any planetary nebulae at all in the nuclear region of the Galaxy. Therefore the expected lifetime and flux density distribution of galactic center nebulae is considered. The principal observational results from the Westerbork data, and the results of some pilot observations with the Very Large Array, which were intended to distinguish planetaries from other radio sources on an individual basis are given. (Auth.)

  14. Facilitating NASA Earth Science Data Processing Using Nebula Cloud Computing

    Pham, Long; Chen, Aijun; Kempler, Steven; Lynnes, Christopher; Theobald, Michael; Asghar, Esfandiari; Campino, Jane; Vollmer, Bruce

    2011-01-01

    Cloud Computing has been implemented in several commercial arenas. The NASA Nebula Cloud Computing platform is an Infrastructure as a Service (IaaS) built in 2008 at NASA Ames Research Center and 2010 at GSFC. Nebula is an open source Cloud platform intended to: a) Make NASA realize significant cost savings through efficient resource utilization, reduced energy consumption, and reduced labor costs. b) Provide an easier way for NASA scientists and researchers to efficiently explore and share large and complex data sets. c) Allow customers to provision, manage, and decommission computing capabilities on an as-needed bases

  15. Morphology of bipolar planetary nebulae. I. Two-dimensional spectrophotometry

    Pascoli, G.

    1990-01-01

    Two-dimensional spectrophotometric observations of bipolar planetary nebulae were performed by using a CCD detector mounted at the Cassegrain focus of either 1.54 m Danish Telescope or 2.2 m German Telescope at La Silla (ESO) in Chile. Emission lines have been selected with the help of narrow band-pass interference filters (Δλ∼ 10 - 20 A). Isophotal maps in various lines Hα, [NII] λ 6584, [OIII] λ 5007 and [SII] λλ 6717-6731 are presented. Particular attention has been given to scrutinize the symmetries inside a few bipolar planetary nebulae, in order to subsequently investigate their space structure

  16. Infrared studies of galactic nebulae. IV - Continuum and line radiation from planetary nebulae.

    Gillett, F. C.; Merrill, K. M.; Stein, W. A.

    1972-01-01

    Observations are reported of the detection of IR radiation from several planetary nebulae not previously known to be radiating at these wavelengths. Broad spectral bandwidth observations indicate that ir radiation in excess of that expected from atomic processes is a common phenomenon among these objects. Investigations with narrow spectral bandwidth show that in a few cases the energy in the 10.52-micron line is a significant fraction of the total energy observed in the broad-band measurements and in other cases a relatively small fraction of the total radiation. Other observations on two sources with narrow spectral bandwidth adjacent to the 10.52-micron line indicate that at these wavelengths a true continuum of radiation exists as well as lines. The results are discussed in relation to visual and radio-wavelength data.

  17. International Ultraviolet Explorer satellite observations of seven high-excitation planetary nebulae.

    Aller, L H; Keyes, C D

    1980-03-01

    Observations of seven high-excitation planetary nebulae secured with the International Ultraviolet Explorer (IUE) satellite were combined with extensive ground-based data to obtain electron densities, gas kinetic temperatures, and ionic concentrations. We then employed a network of theoretical model nebulae to estimate the factors by which observed ionic concentrations must be multiplied to obtain elemental abundances. Comparison with a large sample of nebulae for which extensive ground-based observations have been obtained shows nitrogen to be markedly enhanced in some of these objects. Possibly most, if not all, high-excitation nebulae evolve from stars that have higher masses than progenitors of nebulae of low-to-moderate excitation.

  18. A new survey of nebulae around Galactic Wolf-Rayet stars in the northern sky

    Miller, Grant J.; Chu, You-Hua

    1993-01-01

    Interference filter CCD images have been obtained in H-alpha and forbidden O III 5007 A for 62 Wolf-Rayet (W-R) stars, representing a complete survey of nebulae around Galactic W-R stars in the northern sky. We find probable new ring nebulae around W-R stars number 113, 116 and 132, and possible new ring nebulae around W-R stars number 133 and 153. All survey images showing nebulosities around W-R stars are presented in this paper. New physical information is derived from the improved images of known ring nebulae. The absence of ring nebulae around most W-R stars is discussed.

  19. A new planetary nebula in the outer reaches of the Galaxy

    Viironen, K.; Mampaso, A.; L. M. Corradi, R.

    2011-01-01

    of a new planetary nebula towards the Anticentre direction, IPHASX J052531.19+281945.1 (PNG 178.1-04.0), is presented. The planetary nebula was discovered from the IPHAS survey. Long-slit follow-up spectroscopy was carried out to confirm its planetary nebula nature and to calculate its physical...... and chemical characteristics. The newly discovered planetary nebula turned out to be located at a very large galactocentric distance (D_GC=20.8+-3.8 kpc), larger than any previously known planetary nebula with measured abundances. Its relatively high oxygen abundance (12+log(O/H) = 8.36+-0.03) supports...

  20. VizieR Online Data Catalog: MIPS 24um nebulae (Gvaramadze+, 2010)

    Gvaramadze, V. V.; Kniazev, A. Y.; Fabrika, S.

    2011-03-01

    Massive evolved stars lose a large fraction of their mass via copious stellar wind or instant outbursts. During certain evolutionary phases, they can be identified by the presence of their circumstellar nebulae. In this paper, we present the results of a search for compact nebulae (reminiscent of circumstellar nebulae around evolved massive stars) using archival 24um data obtained with the Multiband Imaging Photometer for Spitzer. We have discovered 115 nebulae, most of which bear a striking resemblance to the circumstellar nebulae associated with luminous blue variables (LBVs) and late WN-type (WNL) Wolf-Rayet (WR) stars in the Milky Way and the Large Magellanic Cloud (LMC). (1 data file).

  1. A 'FIREWORK' OF H2 KNOTS IN THE PLANETARY NEBULA NGC 7293 (THE HELIX NEBULA)

    Matsuura, M.; Speck, A. K.; McHunu, B. M.; Tanaka, I.; Wright, N. J.; Viti, S.; Wesson, R.; Smith, M. D.; Zijlstra, A. A.

    2009-01-01

    We present a deep and wide field-of-view (4' x 7') image of the planetary nebula (PN) NGC 7293 (the Helix Nebula) in the 2.12 μm H 2 v = 1 → 0 S(1) line. The excellent seeing (0.''4) at the Subaru Telescope, allows the details of cometary knots to be examined. The knots are found at distances of 2.'2-6.'4 from the central star (CS). At the inner edge and in the inner ring (up to 4.'5 from the CS), the knot often show a 'tadpole' shape, an elliptical head with a bright crescent inside and a long tail opposite to the CS. In detail, there are variations in the tadpole shapes, such as narrowing tails, widening tails, meandering tails, or multipeaks within a tail. In the outer ring (4.'5-6.'4 from the CS), the shapes are more fractured, and the tails do not collimate into a single direction. The transition in knot morphology from the inner edge to the outer ring is clearly seen. The number density of knots governs the H 2 surface brightness in the inner ring: H 2 exists only within the knots. Possible mechanisms which contribute to the shaping of the knots are discussed, including photoionization and streaming motions. A plausible interpretation of our images is that inner knots are being overrun by a faster wind, but that this has not (yet) reached the outer knots. Based on H 2 formation and destruction rates, H 2 gas can survive in knots from formation during the late asymptotic giant branch phase throughout the PN phase. These observations provide new constraints on the formation and evolution of knots, and on the physics of molecular gas embedded within ionized gas.

  2. A "Firework" of H2 Knots in the Planetary Nebula NGC 7293 (The Helix Nebula)

    Matsuura, M.; Speck, A. K.; McHunu, B. M.; Tanaka, I.; Wright, N. J.; Smith, M. D.; Zijlstra, A. A.; Viti, S.; Wesson, R.

    2009-08-01

    We present a deep and wide field-of-view (4' × 7') image of the planetary nebula (PN) NGC 7293 (the Helix Nebula) in the 2.12 μm H2 v = 1 → 0 S(1) line. The excellent seeing (0farcs4) at the Subaru Telescope, allows the details of cometary knots to be examined. The knots are found at distances of 2farcm2-6farcm4 from the central star (CS). At the inner edge and in the inner ring (up to 4farcm5 from the CS), the knot often show a "tadpole" shape, an elliptical head with a bright crescent inside and a long tail opposite to the CS. In detail, there are variations in the tadpole shapes, such as narrowing tails, widening tails, meandering tails, or multipeaks within a tail. In the outer ring (4farcm5-6farcm4 from the CS), the shapes are more fractured, and the tails do not collimate into a single direction. The transition in knot morphology from the inner edge to the outer ring is clearly seen. The number density of knots governs the H2 surface brightness in the inner ring: H2 exists only within the knots. Possible mechanisms which contribute to the shaping of the knots are discussed, including photoionization and streaming motions. A plausible interpretation of our images is that inner knots are being overrun by a faster wind, but that this has not (yet) reached the outer knots. Based on H2 formation and destruction rates, H2 gas can survive in knots from formation during the late asymptotic giant branch phase throughout the PN phase. These observations provide new constraints on the formation and evolution of knots, and on the physics of molecular gas embedded within ionized gas. Based on data taken with the Subaru Telescope, National Astronomical Observatory of Japan (proposal ID S07B-054).

  3. Expansion patterns and parallaxes for planetary nebulae

    Schönberner, D.; Balick, B.; Jacob, R.

    2018-02-01

    Aims: We aim to determine individual distances to a small number of rather round, quite regularly shaped planetary nebulae by combining their angular expansion in the plane of the sky with a spectroscopically measured expansion along the line of sight. Methods: We combined up to three epochs of Hubble Space Telescope imaging data and determined the angular proper motions of rim and shell edges and of other features. These results are combined with measured expansion speeds to determine individual distances by assuming that line of sight and sky-plane expansions are equal. We employed 1D radiation-hydrodynamics simulations of nebular evolution to correct for the difference between the spectroscopically measured expansion velocities of rim and shell and of their respective shock fronts. Results: Rim and shell are two independently expanding entities, driven by different physical mechanisms, although their model-based expansion timescales are quite similar. We derive good individual distances for 15 objects, and the main results are as follows: (i) distances derived from rim and shell agree well; (ii) comparison with the statistical distances in the literature gives reasonable agreement; (iii) our distances disagree with those derived by spectroscopic methods; (iv) central-star "plateau" luminosities range from about 2000 L⊙ to well below 10 000 L⊙, with a mean value at about 5000 L⊙, in excellent agreement with other samples of known distance (Galactic bulge, Magellanic Clouds, and K648 in the globular cluster M 15); (v) the central-star mass range is rather restricted: from about 0.53 to about 0.56 M⊙, with a mean value of 0.55 M⊙. Conclusions: The expansion measurements of nebular rim and shell edges confirm the predictions of radiation-hydrodynamics simulations and offer a reliable method for the evaluation of distances to suited objects. Results of this paper are based on observations made with the NASA/ESA Hubble Space Telescope in Cycle 16 (GO11122

  4. Abundant Solar Nebula Solids in Comets

    Messenger, S.; Keller, L. P.; Nakamura-Messenger, K.; Nguyen, A. N.; Clemett, S.

    2016-01-01

    Comets have been proposed to consist of unprocessed interstellar materials together with a variable amount of thermally annealed interstellar grains. Recent studies of cometary solids in the laboratory have shown that comets instead consist of a wide range of materials from across the protoplanetary disk, in addition to a minor complement of interstellar materials. These advances were made possible by the return of direct samples of comet 81P/Wild 2 coma dust by the NASA Stardust mission and recent advances in microscale analytical techniques. Isotopic studies of 'cometary' chondritic porous interplanetary dust particles (CP-IDPs) and comet 81P/Wild 2 Stardust samples show that preserved interstellar materials are more abundant in comets than in any class of meteorite. Identified interstellar materials include sub-micron-sized presolar silicates, oxides, and SiC dust grains and some fraction of the organic material that binds the samples together. Presolar grain abundances reach 1 weight percentage in the most stardust-rich CP-IDPs, 50 times greater than in meteorites. Yet, order of magnitude variations in presolar grain abundances among CP-IDPs suggest cometary solids experienced significant variations in the degree of processing in the solar nebula. Comets contain a surprisingly high abundance of nebular solids formed or altered at high temperatures. Comet 81P/Wild 2 samples include 10-40 micron-sized, refractory Ca- Al-rich inclusion (CAI)-, chondrule-, and ameboid olivine aggregate (AOA)-like materials. The O isotopic compositions of these refractory materials are remarkably similar to their meteoritic counterparts, ranging from 5 percent enrichments in (sup 16) O to near-terrestrial values. Comet 81P/Wild 2 and CP-IDPs also contain abundant Mg-Fe crystalline and amorphous silicates whose O isotopic compositions are also consistent with Solar System origins. Unlike meteorites, that are dominated by locally-produced materials, comets appear to be composed of

  5. The first frost in the Pipe Nebula

    Goto, Miwa; Bailey, Jeffrey D.; Hocuk, Seyit; Caselli, Paola; Esplugues, Gisela B.; Cazaux, Stephanie; Spaans, Marco

    2018-02-01

    Context. Spectroscopic studies of ices in nearby star-forming regions indicate that ice mantles form on dust grains in two distinct steps, starting with polar ice formation (H2O rich) and switching to apolar ice (CO rich). Aims: We test how well the picture applies to more diffuse and quiescent clouds where the formation of the first layers of ice mantles can be witnessed. Methods: Medium-resolution near-infrared spectra are obtained toward background field stars behind the Pipe Nebula. Results: The water ice absorption is positively detected at 3.0 μm in seven lines of sight out of 21 sources for which observed spectra are successfully reduced. The peak optical depth of the water ice is significantly lower than those in Taurus with the same AV. The source with the highest water-ice optical depth shows CO ice absorption at 4.7 μm as well. The fractional abundance of CO ice with respect to water ice is 16-6+7%, and about half as much as the values typically seen in low-mass star-forming regions. Conclusions: A small fractional abundance of CO ice is consistent with some of the existing simulations. Observations of CO2 ice in the early diffuse phase of a cloud play a decisive role in understanding the switching mechanism between polar and apolar ice formation. Based on data collected by SpeX at the Infrared Telescope Facility, which is operated by the University of Hawaii under contract NNH14CK55B with the National Aeronautics and Space Administration.Based also on data obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.The final reduced spectra (FITS format) are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/610

  6. INFRARED STUDY OF FULLERENE PLANETARY NEBULAE

    García-Hernández, D. A.; Acosta-Pulido, J. A.; Manchado, A.; Villaver, E.; García-Lario, P.; Stanghellini, L.; Shaw, R. A.; Cataldo, F.

    2012-01-01

    We present a study of 16 planetary nebulae (PNe) where fullerenes have been detected in their Spitzer Space Telescope spectra. This large sample of objects offers a unique opportunity to test conditions of fullerene formation and survival under different metallicity environments because we are analyzing five sources in our own Galaxy, four in the Large Magellanic Cloud (LMC), and seven in the Small Magellanic Cloud (SMC). Among the 16 PNe studied, we present the first detection of C 60 (and possibly also C 70 ) fullerenes in the PN M 1–60 as well as of the unusual ∼6.6, 9.8, and 20 μm features (attributed to possible planar C 24 ) in the PN K 3–54. Although selection effects in the original samples of PNe observed with Spitzer may play a potentially significant role in the statistics, we find that the detection rate of fullerenes in C-rich PNe increases with decreasing metallicity (∼5% in the Galaxy, ∼20% in the LMC, and ∼44% in the SMC) and we interpret this as a possible consequence of the limited dust processing occurring in Magellanic Cloud (MC) PNe. CLOUDY photoionization modeling matches the observed IR fluxes with central stars that display a rather narrow range in effective temperature (∼30,000-45,000 K), suggesting a common evolutionary status of the objects and similar fullerene formation conditions. Furthermore, the data suggest that fullerene PNe likely evolve from low-mass progenitors and are usually of low excitation. We do not find a metallicity dependence on the estimated fullerene abundances. The observed C 60 intensity ratios in the Galactic sources confirm our previous finding in the MCs that the fullerene emission is not excited by the UV radiation from the central star. CLOUDY models also show that line- and wind-blanketed model atmospheres can explain many of the observed [Ne III]/[Ne II] ratios using photoionization, suggesting that possibly the UV radiation from the central star, and not shocks, is triggering the decomposition

  7. Observational study of Herbig-Haro nebulae

    Brugel, E.W.

    1981-01-01

    Spectrophotometric data have been obtained for twelve Herbig-Haro nebulae with the multichannel spectrometer on the Mt. Palomar 5.08 meter telescope and with the image intensified dissector scanner on the Kitt Peak 2.13 meter telescope. Energy distributions of the continuous spectra of the Herbig-Haro objects H-H 1 (NW), H-H 2A, H-H 2G, H-H 2H, H-H 24A and H-H 32 have been determined in the wavelength range 3300 to 8000A. The signal-to-noise ratio has been improved in comparison to an earlier attempt to measure the continuum in H-H 1 and H-H 2H. Reddening corrections are based on Miller's [SII] method. The [FeII] emission line spectra have also been utilized as a secondary method for determining the interstellar reddening. In all continua the flux F/sub lambda/ increases rapidly with decreasing wavelength after the small scale structure has been averaged out. A power law interpolation F/sub lambda/ proportional lambda/sup -n/ demonstrates that for all observed H-H objects n lies in the range between 2.04 (H-H 2A, H-H 2H) and 2.92 (H-H 32). The relation of these results to recent I.U.E. observations of H-H 1 is discussed. It is also found that the ratio of the total optical continuum flux to Hβ flux is almost the same for all observed H-H objects with the sole exception of H-H 24A in which the continuum is considerably stronger than in other objects. This fact leads to difficulties in the usual dust scattering hypothesis for the interpretation of H-H continua. It is argued, if these energy distributions are really due to dust scattering in stellar continua as has been usually assumed, the original source must be a hot object and cannot be a T Tauri star.An interpretation in terms of transition radiation (as suggested by Gurzadyan) does not seem to be possible because the observed rise of F/sub lambda/ towards the ultraviolet is too steep

  8. The central star of the Planetary Nebula NGC 6537

    Pottasch, [No Value

    2000-01-01

    The fact that Space Telescope WFPC2 images of the planetary nebula NGC 6537 fail to show the central star is used to derive a limit to its magnitude: it is fainter than a magnitude of 22.4 in the visible. This is used to derive a lower limit to the temperature of the star. The Zanstra temperature is

  9. Large-Scale Structure of the Carina Nebula.

    Smith; Egan; Carey; Price; Morse; Price

    2000-04-01

    Observations obtained with the Midcourse Space Experiment (MSX) satellite reveal for the first time the complex mid-infrared morphology of the entire Carina Nebula (NGC 3372). On the largest size scale of approximately 100 pc, the thermal infrared emission from the giant H ii region delineates one coherent structure: a (somewhat distorted) bipolar nebula with the major axis perpendicular to the Galactic plane. The Carina Nebula is usually described as an evolved H ii region that is no longer actively forming stars, clearing away the last vestiges of its natal molecular cloud. However, the MSX observations presented here reveal numerous embedded infrared sources that are good candidates for sites of current star formation. Several compact infrared sources are located at the heads of dust pillars or in dark globules behind ionization fronts. Because their morphology suggests a strong interaction with the peculiar collection of massive stars in the nebula, we speculate that these new infrared sources may be sites of triggered star formation in NGC 3372.

  10. Preferrential Concentration of Particles in Protoplanetary Nebula Turbulence

    Hartlep, Thomas; Cuzzi, Jeffrey N.

    2015-01-01

    Preferential concentration in turbulence is a process that causes inertial particles to cluster in regions of high strain (in-between high vorticity regions), with specifics depending on their stopping time or Stokes number. This process is thought to be of importance in various problems including cloud droplet formation and aerosol transport in the atmosphere, sprays, and also in the formation of asteroids and comets in protoplanetary nebulae. In protoplanetary nebulae, the initial accretion of primitive bodies from freely-floating particles remains a problematic subject. Traditional growth-by-sticking models encounter a formidable "meter-size barrier" [1] in turbulent nebulae. One scenario that can lead directly from independent nebula particulates to large objects, avoiding the problematic m-km size range, involves formation of dense clumps of aerodynamically selected, typically mm-size particles in protoplanetary turbulence. There is evidence that at least the ordinary chondrite parent bodies were initially composed entirely of a homogeneous mix of such particles generally known as "chondrules" [2]. Thus, while it is arcane, turbulent preferential concentration acting directly on chondrule size particles are worthy of deeper study. Here, we present the statistical determination of particle multiplier distributions from numerical simulations of particle-laden isotopic turbulence, and a cascade model for modeling turbulent concentration at lengthscales and Reynolds numbers not accessible by numerical simulations. We find that the multiplier distributions are scale dependent at the very largest scales but have scale-invariant properties under a particular variable normalization at smaller scales.

  11. Hard X-ray Variations in the Crab Nebula

    Wilson-Hodge, Colleen A.; Cherry, M. L.; Case, G. L.; Baumgartner, W. H.; Beklen, E.; Bhat, P. N.; Briggs, M. S.; Camero-Arranz, A.; Connaughton, V.; Finger, M. H.; hide

    2013-01-01

    In the first two years of science operations of the Fermi Gamma-ray Burst Monitor (GBM), August 2008 to August 2010, approximately 7% (70 mcrab) decline was discovered in the overall Crab Nebula flux in the 15 - 50 keV band, measured with the Earth occultation technique. This decline was independently confirmed with four other instruments: the RXTE/PCA, Swift/BAT, INTEGRAL/IBIS, and INTEGRAL/SPI. The pulsed flux measured with RXTE/PCA from 1999-2010 was consistent with the pulsar spin-down, indicating that the observed changes were nebular. From 2001 to 2010, the Crab nebula flux measured with RXTE/ PCA was particularly variable, changing by up to approximately 3.5% per year in the 15-50 keV band. These variations were confirmed with INTEGRAL/SPI starting in 2003, Swift/BAT starting in 2005, and Fermi GBM starting in 2008. Before 2001 and since 2010, the Crab nebula flux has appeared more stable, varying by less than 2% per year. I will present updated light curves in multiple energy bands for the Crab Nebula, including recent data from Fermi GBM, Swift/BAT, INTEGRAL and MAXI, and a 16-year long light curve from RXTE/PCA.

  12. Millimeter-wave molecular line observations of the Tornado nebula

    Sakai, D.; Oka, T.; Tanaka, K.; Matsumura, S.; Miura, K.; Takekawa, S.

    2014-01-01

    We report the results of millimeter-wave molecular line observations of the Tornado Nebula (G357.7-0.1), which is a bright radio source behind the Galactic center region. A 15' × 15' area was mapped in the J = 1-0 lines of CO, 13 CO, and HCO + with the Nobeyama Radio Observatory 45 m telescope. The Very Large Array archival data of OH at 1720 MHz were also reanalyzed. We found two molecular clouds with separate velocities, V LSR = –14 km s –1 and +5 km s –1 . These clouds show rough spatial anti-correlation. Both clouds are associated with OH 1720 MHz emissions in the area overlapping with the Tornado Nebula. The spatial and velocity coincidence indicates violent interaction between the clouds and the Tornado Nebula. Modestly excited gas prefers the position of the Tornado 'head' in the –14 km s –1 cloud, also suggesting the interaction. Virial analysis shows that the +5 km s –1 cloud is more tightly bound by self-gravity than the –14 km s –1 cloud. We propose a formation scenario for the Tornado Nebula; the +5 km s –1 cloud collided into the –14 km s –1 cloud, generating a high-density layer behind the shock front, which activates a putative compact object by Bondi-Hoyle-Lyttleton accretion to eject a pair of bipolar jets.

  13. Unusual motions in the Wolf-Rayet nebula NGC 6888

    Johnson, P.G.; Songsathaporn, R.

    1981-01-01

    A systematic survey of the velocity structure within the Wolf-Rayet ring nebula NGC 6888 has been undertaken by making observations of the [N II] line profiles. They reveal a hitherto undetected and particularly unusual velocity structure with three of the brightest portions of the circumference of this ring exhibiting triple line components. Possible models to explain these observations are discussed. (author)

  14. Multibaseline Observations of the Occultation of Crab Nebula by the ...

    tribpo

    Observations of the radio source Crab Nebula were made at the time of transit during. June 1986 and 1987. The fringe amplitude V(S) for a baseline S was calibrated using the corresponding baseline fringe amplitude of radio source 3C123 or 3C134 and normalised to the preoccultation value V(O). Normalised fringe ...

  15. Crab Nebula Variations in Hard X-rays

    Wilson-Hodge, Colleen A.

    2012-01-01

    The Crab Nebula was surprisingly variable from 2001-2010, with less variability before 2001 and since mid-2010. We presented evidence for spectral softening from RXTE, Swift/BAT, and Fermi GBM during the mid-2008-2010 flux decline. We see no clear connections between the hard X-ray variations and the GeV flares

  16. OpenNebula KVM SR-IOV driver

    Macleod, D

    2013-05-01

    Full Text Available With the recent release of an OFED which supports SR-IOV on Infiniband HCAs it is now possible to use verbs from inside a VM. This VMM driver supports these Infiniband HCAs, and any other SR-IOV network device, in OpenNebula....

  17. Modern techniques in galaxy kinematics : Results from planetary nebula spectroscopy

    Romanowsky, AJ; Douglas, NG; Kuijken, K; Arnaboldi, M; Gerssen, J; Merrifield, MR; Kwok, S; Dopita, M; Sutherland, R

    2003-01-01

    We have observed planetary nebulae (PNe) in several early-type galaxies using new techniques on 4- to 8-meter-class telescopes. We obtain the first large data sets (greater than or similar to 100 velocities each) of PN kinematics in galaxies at greater than or similar to 15 Mpc, and present some

  18. Protostar Evolution in the Orion Nebula Cluster (ONC)

    Sanchez, Michael Allan

    2018-01-01

    We present our preliminary analysis of the protostars within the Orion Nebula Cluster (ONC). We developed a pipeline to identify protostars in the ONC using the IRAC instrument aboard Spitzer. We verified our photometric measurements with the catalog provided by Megeath et al. (2012). We then classified the protostar evolution stages (0/I, Flatt, II, and III) based on their spectral slope.

  19. Probing AGB nucleosynthesis via accurate Planetary Nebula abundances

    Marigo, P; Bernard-Salas, J; Pottasch, S. R.; Tielens, A. G. G. M.; Wesselius, P. R.

    2003-01-01

    The elemental abundances of ten planetary nebulae, derived with high accuracy including ISO and IUE spectra, are analysed with the aid of synthetic evolutionary models for the TP-AGB phase. The accuracy on the observed abundances is essential in order to make a reliable comparison with the models.

  20. Formation of planetary nebulae with close binary nuclei

    Livio, M; Salzman, J; Shaviv, G [Tel Aviv Univ. (Israel). Dept. of Physics and Astronomy

    1979-07-01

    A model for the formation of planetary nebulae with a close binary as a nucleus is presented. The model is based on mass loss instability at L/sub 2/. The instability is demonstrated. The conditions on the mass loss are formulated and analysed. The observational consequence of the model is described briefly and its relation to symbiotic stars and cataclysmic binaries discussed.

  1. Spectrum and the structure of the bipolar nebula S 106

    Solf, J [Max-Planck-Institut fuer Astronomie, Heidelberg (Germany, F.R.)

    1980-12-01

    Optically the compact region S 106 appears as a bipolar nebula with the exciting stellar source located between the lobes and embedded in a flat disk of material of high visual extinction. Associated with the nebula is a massive molecular cloud exhibiting a rotating disk-like structure, the axis of rotation being observed in the same direction as the bipolar axis of the nebula. We analyse new optical and near-infrared spectra obtained with an image-tube spectrograph. The emission line spectrum of both lobes resembles that of the Orion nebula and indicates high electron density throughout. The nebular continuum discovered in both lobes is interpreted as originating from an early-type stellar source between the lobes, and scattered by dust particles coexisting with the ionized gas within the lobes. The Hsub(..cap alpha..) radial velocity field indicates supersonic motion of ionized material flowing radially outward through the lobes. The shape and kinematic structure of the lobes are in qualitative agreement with the predictions of the champagne model of Tenorio-Tagle (1979) applied to the case of star formation near the center of a disk-shaped dense cloud.

  2. Modelling the ArH+ emission from the Crab nebula

    Priestley, F. D.; Barlow, M. J.; Viti, S.

    2017-12-01

    We have performed combined photoionization and photodissociation region (PDR) modelling of a Crab nebula filament subjected to the synchrotron radiation from the central pulsar wind nebula, and to a high flux of charged particles; a greatly enhanced cosmic-ray ionization rate over the standard interstellar value, ζ0, is required to account for the lack of detected [C I] emission in published Herschel SPIRE FTS observations of the Crab nebula. The observed line surface brightness ratios of the OH+ and ArH+ transitions seen in the SPIRE FTS frequency range can only be explained with both a high cosmic-ray ionization rate and a reduced ArH+ dissociative recombination rate compared to that used by previous authors, although consistent with experimental upper limits. We find that the ArH+/OH+ line strengths and the observed H2 vibration-rotation emission can be reproduced by model filaments with nH = 2 × 104 cm-3, ζ = 107ζ0 and visual extinctions within the range found for dusty globules in the Crab nebula, although far-infrared emission from [O I] and [C II] is higher than the observational constraints. Models with nH = 1900 cm-3 underpredict the H2 surface brightness, but agree with the ArH+ and OH+ surface brightnesses and predict [O I] and [C II] line ratios consistent with observations. These models predict HeH+ rotational emission above detection thresholds, but consideration of the formation time-scale suggests that the abundance of this molecule in the Crab nebula should be lower than the equilibrium values obtained in our analysis.

  3. Super-Acceleration in the Flaring Crab Nebula

    Tavani, Marco, E-mail: marco.tavani@inaf.it

    2013-10-15

    The Crab Nebula continues to surprise us. The Crab system (energized by a very powerful pulsar at the center of the Supernova Remnant SN1054) is known to be a very efficient particle “accelerator” which can reach PeV energies. Today, new surprising data concerning the gamma-ray flares produced by the Crab Nebula challenge models of particle acceleration. The total energy flux from the Crab has been considered for many decades substantially stable at X-ray and gamma-ray energies. However, this paradigm was shattered by the AGILE discovery and Fermi confirmation in September 2010 of transient gamma-ray emission from the Crab. Indeed, we can state that four major flaring gamma-ray episodes have been detected by AGILE and Fermi during the period mid-2007/2012. During these events, transient particle acceleration occurs in a regime which apparently violates the MHD conditions and synchrotron cooling constraints. This fact justifies calling “super-acceleration” the mechanism which produces the “flaring Crab phenomenon”. Radiation between 50 MeV and a few GeV is emitted with a quite hard spectrum within a short timescale (hours-days), with no obvious relation with simultaneous optical and X-ray emissions in the inner Nebula. “Super-acceleration” implies overcoming synchrotron cooling by strong (and “parallel”) electric fields most likely produced by magnetic field reconnection within the pulsar wind outflow. This acceleration appears to be very efficient and, remarkably, limited by radiation reaction. It is not clear at the moment where in the Nebula this phenomenon occurs. An intense observational program is now focused on the Crab Nebula to resolve its most challenging mystery.

  4. The Chandra planetary nebula survey (CHANPLANS). II. X-ray emission from compact planetary nebulae

    Freeman, M.; Kastner, J. H. [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Montez, R. Jr. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN (United States); Balick, B. [Department of Astronomy, University of Washington, Seattle, WA (United States); Frew, D. J.; De Marco, O.; Parker, Q. A. [Department of Physics and Astronomy and Macquarie Research Centre for Astronomy, Astrophysics and Astrophotonics, Macquarie University, Sydney, NSW 2109 (Australia); Jones, D. [Departamento de Física, Universidad de Atacama, Copayapu 485, Copiapó (Chile); Miszalski, B. [South African Astronomical Observatory, P.O. Box 9, Observatory, 7935 (South Africa); Sahai, R. [Jet Propulsion Laboratory, MS 183-900, California Institute of Technology, Pasadena, CA 91109 (United States); Blackman, E.; Frank, A. [Department of Physics and Astronomy, University of Rochester, Rochester, NY (United States); Chu, Y.-H. [Department of Astronomy, University of Illinois at Urbana-Champaign, Urbana, IL (United States); Guerrero, M. A. [Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, Granada, E-18008 (Spain); Lopez, J. A. [Instituto de Astronomía, Universidad Nacional Autonoma de Mexico, Campus Ensenada, Apdo. Postal 22860, Ensenada, B. C. (Mexico); Zijlstra, A. [School of Physics and Astronomy, University of Manchester, Manchester M13 9PL (United Kingdom); Bujarrabal, V. [Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife (Spain); Corradi, R. L. M. [Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife (Spain); Nordhaus, J. [NSF Astronomy and Astrophysics Fellow, Center for Computational Relativity and Gravitation, Rochester Institute of Technology, Rochester, NY 14623 (United States); and others

    2014-10-20

    We present results from the most recent set of observations obtained as part of the Chandra X-ray observatory Planetary Nebula Survey (CHANPLANS), the first comprehensive X-ray survey of planetary nebulae (PNe) in the solar neighborhood (i.e., within ∼1.5 kpc of the Sun). The survey is designed to place constraints on the frequency of appearance and range of X-ray spectral characteristics of X-ray-emitting PN central stars and the evolutionary timescales of wind-shock-heated bubbles within PNe. CHANPLANS began with a combined Cycle 12 and archive Chandra survey of 35 PNe. CHANPLANS continued via a Chandra Cycle 14 Large Program which targeted all (24) remaining known compact (R {sub neb} ≲ 0.4 pc), young PNe that lie within ∼1.5 kpc. Results from these Cycle 14 observations include first-time X-ray detections of hot bubbles within NGC 1501, 3918, 6153, and 6369, and point sources in HbDs 1, NGC 6337, and Sp 1. The addition of the Cycle 14 results brings the overall CHANPLANS diffuse X-ray detection rate to ∼27% and the point source detection rate to ∼36%. It has become clearer that diffuse X-ray emission is associated with young (≲ 5 × 10{sup 3} yr), and likewise compact (R {sub neb} ≲ 0.15 pc), PNe with closed structures and high central electron densities (n{sub e} ≳ 1000 cm{sup –3}), and is rarely associated with PNe that show H{sub 2} emission and/or pronounced butterfly structures. Hb 5 is one such exception of a PN with a butterfly structure that hosts diffuse X-ray emission. Additionally, two of the five new diffuse X-ray detections (NGC 1501 and NGC 6369) host [WR]-type central stars, supporting the hypothesis that PNe with central stars of [WR]-type are likely to display diffuse X-ray emission.

  5. PLANETARY NEBULAE IN FACE-ON SPIRAL GALAXIES. II. PLANETARY NEBULA SPECTROSCOPY

    Herrmann, Kimberly A.; Ciardullo, Robin

    2009-01-01

    As the second step in our investigation of the mass-to-light ratio of spiral disks, we present the results of a spectroscopic survey of planetary nebulae (PNe) in five nearby, low-inclination galaxies: IC 342, M74 (NGC 628), M83 (NGC 5236), M94 (NGC 4736), and M101 (NGC 5457). Using 50 setups of the WIYN/Hydra and Blanco/Hydra spectrographs, and 25 observations with the Hobby-Eberly Telescope's Medium Resolution Spectrograph, we determine the radial velocities of 99, 102, 162, 127, and 48 PNe, respectively, to a precision better than 15 km s -1 . Although the main purpose of this data set is to facilitate dynamical mass measurements throughout the inner and outer disks of large spiral galaxies, our spectroscopy has other uses as well. Here, we co-add these spectra to show that, to first order, the [O III] and Balmer line ratios of PNe vary little over the top ∼1.5 mag of the PN luminosity function. The only obvious spectral change occurs with [N II], which increases in strength as one proceeds down the luminosity function. We also show that typical [O III]-bright planetaries have E(B - V) ∼ 0.2 of circumstellar extinction, and that this value is virtually independent of [O III] luminosity. We discuss the implications this has for understanding the population of PN progenitors.

  6. Evolution of planetary nebulae. III. Position-velocity images of butterfly-type nebulae

    Icke, V.; Preston, H.L.; Balick, B.

    1989-01-01

    Observations of the motions of the shells of the planetary nebulae NGC 2346, NGC 2371-2, NGC 2440, NGC 6058, NGC 6210, IC 1747, IC 5217, J-320, and M2-9 are presented. These are all 'butterfly' type PNs, and show evidence for bipolar shocks. The observations are interpreted in terms of a fast spherical wind, driven by the central star into a quasi-toroidal envelope deposited earlier by the star, during its slow-wind phase on the asymptotic giant branch. It is shown that this model, which is a straightforward extension of a mechanism previously invoked to account for elliptical PNs, reproduces the essential kinematic features of butterfly PNs. It is inferred that the envelopes of butterflies must have a considerable equator-to-pole density gradient, and it is suggested that the origin of this asphericity must be sought in an as yet unknown mechanism during the AGB, Mira, or OH/IR phases of late stellar evolution. 28 references

  7. GHOSTLY REFLECTIONS IN THE PLEIADES

    2002-01-01

    NASA's Hubble Space Telescope has caught the eerie, wispy tendrils of a dark interstellar cloud being destroyed by the passage of one of the brightest stars in the Pleiades star cluster. Like a flashlight beam shining off the wall of a cave, the star is reflecting light off the surface of pitch black clouds of cold gas laced with dust. These are called reflection nebulae. The famous cluster is easily visible in the evening sky during the winter months as a small grouping of bright blue stars, named after the 'Seven Sisters' of Greek mythology. Resembling a small dipper, this star cluster lies in the constellation Taurus at a distance of about 380 light-years from Earth. The unaided eye can discern about half a dozen bright stars in the cluster, but a small telescope will reveal that the Pleiades contains many hundreds of fainter stars. In many cases, the nebulae surrounding star clusters represent material from which the stars have formed recently. However the Pleiades nebulosity is actually an independent cloud, drifting through the cluster at a relative speed of about 6.8 miles/second (11 kilometers/second). In 1890, American astronomer E. E. Barnard, observing visually with the Lick Observatory 36-inch telescope in California, discovered an exceptionally bright nebulosity adjacent to the bright Pleiades star Merope. It is now cataloged as IC 349, or 'Barnard's Merope Nebula.' IC 349 is so bright because it lies extremely close to Merope--only about 3,500 times the separation of the Earth from the Sun, or about 0.06 light-year--and thus is strongly illuminated by the star's light. In the new Hubble image, Merope itself is just outside the frame on the upper right. The colorful rays of light at the upper right, pointing back to the star, are an optical phenomenon produced within the telescope, and are not real. However, the remarkable parallel wisps extending from lower left to upper right are real features, revealed for the first time through Hubble's high

  8. Gamma-ray flares from the Crab Nebula.

    Abdo, A A; Ackermann, M; Ajello, M; Allafort, A; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bouvier, A; Brandt, T J; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Cannon, A; Caraveo, P A; Casandjian, J M; Çelik, Ö; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Costamante, L; Cutini, S; D'Ammando, F; Dermer, C D; de Angelis, A; de Luca, A; de Palma, F; Digel, S W; do Couto e Silva, E; Drell, P S; Drlica-Wagner, A; Dubois, R; Dumora, D; Favuzzi, C; Fegan, S J; Ferrara, E C; Focke, W B; Fortin, P; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guiriec, S; Hadasch, D; Hanabata, Y; Harding, A K; Hayashi, K; Hayashida, M; Hays, E; Horan, D; Itoh, R; Jóhannesson, G; Johnson, A S; Johnson, T J; Khangulyan, D; Kamae, T; Katagiri, H; Kataoka, J; Kerr, M; Knödlseder, J; Kuss, M; Lande, J; Latronico, L; Lee, S-H; Lemoine-Goumard, M; Longo, F; Loparco, F; Lubrano, P; Madejski, G M; Makeev, A; Marelli, M; Mazziotta, M N; McEnery, J E; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nakamori, T; Naumann-Godo, M; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Okumura, A; Omodei, N; Ormes, J F; Ozaki, M; Paneque, D; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Pierbattista, M; Piron, F; Porter, T A; Rainò, S; Rando, R; Ray, P S; Razzano, M; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Romani, R W; Sadrozinski, H F-W; Sanchez, D; Saz Parkinson, P M; Scargle, J D; Schalk, T L; Sgrò, C; Siskind, E J; Smith, P D; Spandre, G; Spinelli, P; Strickman, M S; Suson, D J; Takahashi, H; Takahashi, T; Tanaka, T; Thayer, J B; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Troja, E; Uchiyama, Y; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Wang, P; Wood, K S; Yang, Z; Ziegler, M

    2011-02-11

    A young and energetic pulsar powers the well-known Crab Nebula. Here, we describe two separate gamma-ray (photon energy greater than 100 mega-electron volts) flares from this source detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The first flare occurred in February 2009 and lasted approximately 16 days. The second flare was detected in September 2010 and lasted approximately 4 days. During these outbursts, the gamma-ray flux from the nebula increased by factors of four and six, respectively. The brevity of the flares implies that the gamma rays were emitted via synchrotron radiation from peta-electron-volt (10(15) electron volts) electrons in a region smaller than 1.4 × 10(-2) parsecs. These are the highest-energy particles that can be associated with a discrete astronomical source, and they pose challenges to particle acceleration theory.

  9. Million-degree plasma pervading the extended Orion Nebula.

    Güdel, Manuel; Briggs, Kevin R; Montmerle, Thierry; Audard, Marc; Rebull, Luisa; Skinner, Stephen L

    2008-01-18

    Most stars form as members of large associations within dense, very cold (10 to 100 kelvin) molecular clouds. The nearby giant molecular cloud in Orion hosts several thousand stars of ages less than a few million years, many of which are located in or around the famous Orion Nebula, a prominent gas structure illuminated and ionized by a small group of massive stars (the Trapezium). We present x-ray observations obtained with the X-ray Multi-Mirror satellite XMM-Newton, revealing that a hot plasma with a temperature of 1.7 to 2.1 million kelvin pervades the southwest extension of the nebula. The plasma flows into the adjacent interstellar medium. This x-ray outflow phenomenon must be widespread throughout our Galaxy.

  10. Spectrophotometry of Bowen resonance fluorescence lines in three planetary nebulae

    O'Dell, C. R.; Miller, Christopher O.

    1992-01-01

    The results are presented of a uniquely complete, carefully reduced set of observations of the O III Bowen fluorescence lines in the planetary nebulae NGC 6210, NGC 7027, and NGC 7662. A detailed comparison with the predictions of radiative excitation verify that some secondary lines are enhanced by selective population by the charge exchange mechanism involving O IV. Charge exchange is most important in NGC 6210, which is of significantly lower ionization than the other nebulae. In addition to the principal Bowen lines arising from Ly-alpha pumping of the O III O1 line, lines arising from pumping of the O3 line are also observed. Comparison of lines produced by O1 and O3 with the theoretical predictions of Neufeld indicate poor agreement; comparison with the theoretical predictions of Harrington show agreement with NGC 7027 and NGC 7662.

  11. Catalysis by Dust Grains in the Solar Nebula

    Kress, Monika E.; Tielens, Alexander G. G. M.

    1996-01-01

    In order to determine whether grain-catalyzed reactions played an important role in the chemistry of the solar nebula, we have applied our time-dependent model of methane formation via Fischer-Tropsch catalysis to pressures from 10(exp -5) to 1 bar and temperatures from 450 to 650 K. Under these physical conditions, the reaction 3H2 + CO yields CH4 + H2O is readily catalyzed by an iron or nickel surface, whereas the same reaction is kinetically inhibited in the gas phase. Our model results indicate that under certain nebular conditions, conversion of CO to methane could be extremely efficient in the presence of iron-nickel dust grains over timescales very short compared to the lifetime of the solar nebula.

  12. The gas-to-dust ratio in the Orion nebula

    Perinotto, M.; Patriarchi, P.

    1974-01-01

    About sixty spectra have been obtained using an image tube with the nebular spectrograph of the Asiago 122cm reflector, in a position W-E from north of the Trapezium across the star P 1925 into the bay area of the Orion Nebula. Twenty-five spectra have been selected for accurate measurements of the Hβ intensity and of the electron density by the [S II] 6730/6716 intensity line ratio. The results are interpreted in terms of well-mixed gas and dust, not only in the central bright regions, but even in the bay area, where the coefficient of dust extinction counted per electron is found to be larger than in the bright centre of the nebula

  13. Gamma-ray flares from the Crab nebula

    Abdo, A.A.; Ackermann, M.; Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Casandjian, J.M.; Grenier, I.A.; Naumann-Godo, M.; Pierbattista, M.; Tibaldo, L.

    2011-01-01

    A young and energetic pulsar powers the well-known Crab Nebula. Here, we describe two separate gamma-ray (photon energy greater than 100 mega-electron volts) flares from this source detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The first flare occurred in February 2009 and lasted approximately 16 days. The second flare was detected in September 2010 and lasted approximately 4 days. During these outbursts, the gamma-ray flux from the nebula increased by factors of four and six, respectively. The brevity of the flares implies that the gamma rays were emitted via synchrotron radiation from peta-electron-volt (10 15 electron volts) electrons in a region smaller than 1.4 * 10 -2 parsecs. These are the highest-energy particles that can be associated with a discrete astronomical source, and they pose challenges to particle acceleration theory. (authors)

  14. Probing Shocks of the Young Planetary Nebula NGC 7027

    Montez, Rodolfo

    2013-09-01

    The rapid evolution of the planetary nebula NGC 7027 provides a rare glimpse at the evolution of the shocks. We propose a detailed spatial and spectroscopic study of the shock conditions in NGC 7027 that will enhance and bridge our understanding of the shocks seen in other planetary nebula. Comparison between the Cycle 1 observation and a new Cycle 15 observation will (i) confirm the presence of the two components in the extended X-ray emission, (ii) measure the changes (spatial and spectral) in the components, and, (iii) provide a valuable trove of tests and inputs for shock conditions and hydrodynamical simulations. We rely on the unprecedented spatial resolution and soft-sensitivity of Chandra.

  15. Identification of faint central stars in extended, low-surface-brightness planetary nebulae

    Kwitter, K.B.; Lydon, T.J.; Jacoby, G.H.

    1988-01-01

    As part of a larger program to study the properties of planetary nebula central stars, a search for faint central stars in extended, low-surface-brightness planetary nebulae using CCD imaging is performed. Of 25 target nebulae, central star candidates have been identified in 17, with certainties ranging from extremely probable to possible. Observed V values in the central star candidates extend to fainter than 23 mag. The identifications are presented along with the resulting photometric measurements. 24 references

  16. Variation of the extinction law in the Trifid nebula

    Cambrésy, L.; Rho, J.; Marshall, D. J.; Reach, W. T.

    2011-01-01

    Context. In the past few years, the extinction law has been measured in the infrared wavelengths for various molecular clouds and different laws have been obtained. Aims. In this paper we seek variations of the extinction law within the Trifid nebula region. Such variations would demonstrate local dust evolution linked to variation of the environment parameters such as the density or the interstellar radiation field. Methods. The extinction values, A_λ/A_v, are obtained using the 2MASS, UKIDS...

  17. Millimeter-wave molecular line observations of the Tornado nebula

    Sakai, D. [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Oka, T.; Tanaka, K.; Matsumura, S.; Miura, K.; Takekawa, S., E-mail: sakai.daisuke@nao.ac.jp [Department of Physics, Institute of Science and Technology, Keio University, 3-14-1 Hiyoshi, Yokohama, Kanagawa 223-8522 (Japan)

    2014-08-10

    We report the results of millimeter-wave molecular line observations of the Tornado Nebula (G357.7-0.1), which is a bright radio source behind the Galactic center region. A 15' × 15' area was mapped in the J = 1-0 lines of CO, {sup 13}CO, and HCO{sup +} with the Nobeyama Radio Observatory 45 m telescope. The Very Large Array archival data of OH at 1720 MHz were also reanalyzed. We found two molecular clouds with separate velocities, V{sub LSR} = –14 km s{sup –1} and +5 km s{sup –1}. These clouds show rough spatial anti-correlation. Both clouds are associated with OH 1720 MHz emissions in the area overlapping with the Tornado Nebula. The spatial and velocity coincidence indicates violent interaction between the clouds and the Tornado Nebula. Modestly excited gas prefers the position of the Tornado 'head' in the –14 km s{sup –1} cloud, also suggesting the interaction. Virial analysis shows that the +5 km s{sup –1} cloud is more tightly bound by self-gravity than the –14 km s{sup –1} cloud. We propose a formation scenario for the Tornado Nebula; the +5 km s{sup –1} cloud collided into the –14 km s{sup –1} cloud, generating a high-density layer behind the shock front, which activates a putative compact object by Bondi-Hoyle-Lyttleton accretion to eject a pair of bipolar jets.

  18. Very bright optical transient near the Trifid and Lagoon Nebulae

    Dunsby, Peter

    2018-03-01

    Peter Dunsby (University of Cape Town) reports the detection of a very bright optical transient in the region between the Lagoon and Trifid Nebulae based on observations obtained from Cape Town on 20 March 2018, between 01:00 and 03:45 UT. The object was visible throughout the full duration of the observations and not seen when this field was observed previously (08 March 2018).

  19. YOUNG STARLESS CORES EMBEDDED IN THE MAGNETICALLY DOMINATED PIPE NEBULA

    Frau, P.; Girart, J. M.; Alves, F. O.; Beltran, M. T.; Morata, O.; Masque, J. M.; Busquet, G.; Sanchez-Monge, A.; Estalella, R.; Franco, G. A. P.

    2010-01-01

    The Pipe Nebula is a massive, nearby dark molecular cloud with a low star formation efficiency which makes it a good laboratory in which to study the very early stages of the star formation process. The Pipe Nebula is largely filamentary and appears to be threaded by a uniform magnetic field at scales of a few parsecs, perpendicular to its main axis. The field is only locally perturbed in a few regions, such as the only active cluster-forming core B59. The aim of this study is to investigate primordial conditions in low-mass pre-stellar cores and how they relate to the local magnetic field in the cloud. We used the IRAM 30 m telescope to carry out a continuum and molecular survey at 3 and 1 mm of early- and late-time molecules toward four selected starless cores inside the Pipe Nebula. We found that the dust continuum emission maps trace the densest regions better than previous Two Micron All Sky Survey (2MASS) extinction maps, while 2MASS extinction maps trace the diffuse gas better. The properties of the cores derived from dust emission show average radii of ∼0.09 pc, densities of ∼1.3x10 5 cm -3 , and core masses of ∼2.5 M sun . Our results confirm that the Pipe Nebula starless cores studied are in a very early evolutionary stage and present a very young chemistry with different properties that allow us to propose an evolutionary sequence. All of the cores present early-time molecular emission with CS detections in the whole sample. Two of them, cores 40 and 109, present strong late-time molecular emission. There seems to be a correlation between the chemical evolutionary stage of the cores and the local magnetic properties that suggests that the evolution of the cores is ruled by a local competition between the magnetic energy and other mechanisms, such as turbulence.

  20. THE LINE POLARIZATION WITHIN A GIANT Lyα NEBULA

    Prescott, Moire K. M.; Smith, Paul S.; Schmidt, Gary D.; Dey, Arjun

    2011-01-01

    Recent theoretical work has suggested that Lyα nebulae could be substantially polarized in the Lyα emission line, depending on the geometry, kinematics, and powering mechanism at work. Polarization observations can therefore provide a useful constraint on the source of ionization in these systems. In this Letter, we present the first Lyα polarization measurements for a giant Lyα nebula at z∼ 2.656. We do not detect any significant linear polarization of the Lyα emission: P Lyα = 2.6% ± 2.8% (corrected for statistical bias) within a single large aperture. The current data also do not show evidence for the radial polarization gradient predicted by some theoretical models. These results rule out singly scattered Lyα (e.g., from the nearby active galactic nucleus, AGN) and may be inconsistent with some models of backscattering in a spherical outflow. However, the effects of seeing, diminished signal-to-noise ratio, and angle averaging within radial bins make it difficult to put strong constraints on the radial polarization profile. The current constraints may be consistent with higher density outflow models, spherically symmetric infall models, photoionization by star formation within the nebula or the nearby AGN, resonant scattering, or non-spherically symmetric cold accretion (i.e., along filaments). Higher signal-to-noise ratio data probing to higher spatial resolution will allow us to harness the full diagnostic power of polarization observations in distinguishing between theoretical models of giant Lyα nebulae.

  1. Helix Nebula Science Cloud pilot phase open session

    CERN. Geneva

    2018-01-01

    This Helix Nebula Science Cloud (HNSciCloud) public session is open to everyone and will be webcast. The session will provide the audience with an overview of the HNSciCloud pre-commercial procurement project and the innovative cloud platforms that have been developed. A number of practical use-cases from the physics community will be presented as well as the next steps to be undertaken.

  2. Isotopic homogeneity of iron in the early solar nebula.

    Zhu, X K; Guo, Y; O'Nions, R K; Young, E D; Ash, R D

    2001-07-19

    The chemical and isotopic homogeneity of the early solar nebula, and the processes producing fractionation during its evolution, are central issues of cosmochemistry. Studies of the relative abundance variations of three or more isotopes of an element can in principle determine if the initial reservoir of material was a homogeneous mixture or if it contained several distinct sources of precursor material. For example, widespread anomalies observed in the oxygen isotopes of meteorites have been interpreted as resulting from the mixing of a solid phase that was enriched in 16O with a gas phase in which 16O was depleted, or as an isotopic 'memory' of Galactic evolution. In either case, these anomalies are regarded as strong evidence that the early solar nebula was not initially homogeneous. Here we present measurements of the relative abundances of three iron isotopes in meteoritic and terrestrial samples. We show that significant variations of iron isotopes exist in both terrestrial and extraterrestrial materials. But when plotted in a three-isotope diagram, all of the data for these Solar System materials fall on a single mass-fractionation line, showing that homogenization of iron isotopes occurred in the solar nebula before both planetesimal accretion and chondrule formation.

  3. Modeling radio circular polarization in the Crab nebula

    Bucciantini, N.; Olmi, B.

    2018-03-01

    In this paper, we present, for the first time, simulated maps of the circularly polarized synchrotron emission from the Crab nebula, using multidimensional state of the art models for the magnetic field geometry. Synchrotron emission is the signature of non-thermal emitting particles, typical of many high-energy astrophysical sources, both Galactic and extragalactic ones. Its spectral and polarization properties allow us to infer key information on the particles distribution function and magnetic field geometry. In recent years, our understanding of pulsar wind nebulae has improved substantially thanks to a combination of observations and numerical models. A robust detection or non-detection of circular polarization will enable us to discriminate between an electron-proton plasma and a pair plasma, clarifying once for all the origin of the radio emitting particles, setting strong constraints on the pair production in pulsar magnetosphere, and the role of turbulence in the nebula. Previous attempts at measuring the circular polarization have only provided upper limits, but the lack of accurate estimates, based on reliable models, makes their interpretation ambiguous. We show here that those results are above the expected values, and that current polarimetric techniques are not robust enough for conclusive result, suggesting that improvements in construction and calibration of next generation radio facilities are necessary to achieve the desired sensitivity.

  4. The Formation of Graphite Whiskers in the Primitive Solar Nebula

    Nuth, Joseph A., III; Kimura, Yuki; Lucas, Christopher; Ferguson, Frank; Johnson, Natasha M.

    2010-01-01

    It has been suggested that carbonaceous grains are efficiently destroyed in the interstellar medium and must either reform in situ at very low pressures and temperatures or in an alternative environment more conducive to grain growth. Graphite whiskers have been discovered associated with high-temperature phases in meteorites such as calcium aluminum inclusions and chondrules, and it has been suggested that the expulsion of such material from proto stellar nebulae could significantly affect the optical properties of the average interstellar grain population. We have experimentally studied the potential for Fischer-Tropsch and Haber-Bosch type reactions to produce organic materials in protostellar systems from the abundant H2, CO, and N2 reacting on the surfaces of available silicate grains. When graphite grains are repeatedly exposed to H2, CO, and N2 at 875 K abundant graphite whiskers are observed to form on or from the surfaces of the graphite grains. In a dense, turbulent nebula, such extended whiskers are very likely to be broken off, and fragments could be ejected either in polar jets or by photon pressure after transport to the outer reaches of the nebula.

  5. CO survey of the dark nebulae in Taurus and Perseus

    Baran, G.P.

    1986-01-01

    The thesis reports a large-scale survey of carbon monoxide ( 12 CO) emission (at λ = 2.6 mm) from dark nebulae in Taurus and Perseus. CO spectra at 4395 points were obtained within an area of about 800 square degrees generally west of the galactic anti-center. The spatial resolution of the instrument was eight arcminutes and velocity resolution was 2.6 km s -1 /. CO emission is strongest wherever extinction by dust is greatest, spilling over the apparent outer boundaries of the dust clouds observed optically. Combining CO velocity for the nebulae with optically determined distances shows that the clouds in the survey area form several layers. The molecular cloud mass closest to the sun is the Taurus and Auriga complex about 150 +/- 50 pc). Nearer to the Per )B2 OB association (at 350 +/- 100 pc) than the Taurus clouds are the Per OB2 molecular cloud (350 +/- 100 pc) and the California Nebula = NGC15979 molecular clouds (at 400 +/- 150 pc). Cloud masses were determined from integrated CO emission intensity alone by assuming that γ-ray emission intensities can be used to relate H 2 column densities to CO emission intensities

  6. He I lambda 584 in quasars and gaseous nebulae

    Ferland, G.J.

    1980-01-01

    The He I Lα lambda 584 transfer problem for gaseous nebulae is investigated. Realistic photo-ionization models of quasar clouds and planetary nebulae are combined with the Monte Carlo line transfer technique to determine both the efficiency of destruction of lambda 584 by photo-ionization of hydrogen and the mean number of scatterings undergone before destruction. It is found that large fractions (approximately > 90 per cent) of the lambda 584 photons are destroyed before escaping in all cases considered. Nonetheless, the He I lambda lambda 584, 626 doublet should be present in high redshift quasars with an observed equivalent width of approximately 1 A. Detection of this doublet would provide the only clear indication of the presence or absence of a low density narrow line region for objects in which optical forbidden lines have been redshifted beyond the optical window. The strength of the He I 2 1 S-2 1 P 2.0 μm line is predicted to be approximately 4 times stronger than is actually observed in the planetary nebulae NGC 7027. This suggests that dust is embedded in the ionized gas and causes additional destruction of lambda 584. Finally, the calculations show that photo-ionization model calculations can safely assume nearly complete on-the-spot destruction of lambda 584. The common assumption that the He I singlets are formed in case B conditions is examined in an appendix. (author)

  7. Collisional effects in He I lines and helium abundances in planetary nebulae

    Clegg, R.E.S.

    1987-01-01

    Attention is drawn to new, 19-state quantal calculations for collisional excitation by electron impact in neutral helium. Recommended empirical formulae are given for the collisional contribution to HeI recombination lines such as λλ4471, 5876 A in gaseous nebulae. Collisional ionization of metastable (2 3 S) He I is significant for high-temperature nebulae. Collisional transfers provide significant cooling in nebulae with low heavy-element abundances. Revised mean He/H ratios for three large samples of planetary nebulae are given. (author)

  8. The internal kinematics of the planetary nebula NGC 650/1

    Taylor, K.

    1979-01-01

    Hα and [N II], lambda 6584 line profiles from the bright lobes of planetary nebula NGC 650/1 have been obtained. These emission lines show a very strong symmetrical triple-peak velocity structure, not observed previously to the author's knowledge in planetary nebulae. Models are tentatively proposed to explain both the velocity data and the nebula's optical appearance. The velocity splitting amounts to approximately 62 km/s and the rest frame of the nebula is found to have a heliocentric radial velocity of -19 +- 2 km/s. (author)

  9. The nature of the nebula associated with the luminous blue variable star WRA 751

    Hutsemekers, Damien; van Drom, E.

    1991-01-01

    Narrow-band filter imagery as well as medium to high resolution spectroscopy of the nebula surrounding the luminous blue variable (LBV) star WRA 751 are presented. The nebula appears as a slowly expanding H II region of low excitation characterized by a significant N/O overabundance which may be due to the presence in the nebula of nuclear processed material ejected by the star. With the recent discovery of a nebula around HR Car, all but one known galactic LBVs are now shown to be associated...

  10. The emerging planetary nebula CRL 618 and its unsettled central star(s)

    Balick, B. [Department of Astronomy, University of Washington, Seattle, WA 98195-1580 (United States); Riera, A. [Departament de Física I Enginyeria Nuclear, EUETIB, Universitat Politècnica de Catalunya, Comte d' Urgell 187, E-08036 Barcelona (Spain); Raga, A.; Velázquez, P. F. [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, 04510 D.F. (Mexico); Kwitter, K. B., E-mail: balick@uw.edu, E-mail: angels.riera@upc.edu, E-mail: raga@nucleares.unam.mx, E-mail: pablo@nucleares.unam.mx, E-mail: kkwitter@williams.edu [Department of Astronomy, Williams College, Williamstown, MA 01267 (United States)

    2014-11-01

    We report deep long-slit emission-line spectra, the line flux ratios, and Doppler profile shapes of various bright optical lines. The low-ionization lines (primarily [N I], [O I], [S II], and [N II]) originate in shocked knots, as reported by many previous observers. Dust-scattered lines of higher ionization are seen throughout the lobes but do not peak in the knots. Our analysis of these line profiles and the readily discernible stellar continuum shows that (1) the central star is an active symbiotic (whose spectrum resembles the central stars of highly bipolar and young planetary nebulae such as M2-9 and Hen2-437) whose compact companion shows a WC8-type spectrum, (2) extended nebular lines of [O III] and He I originate in the heavily obscured nuclear H II region, and (3) the Balmer lines observed throughout the lobes are dominated by reflected Hα emission from the symbiotic star. Comparing our line ratios with those observed historically shows that (1) the [O III]/Hβ and He I/Hβ ratios have been steadily rising by large amounts throughout the nebula, (2) the Hα/Hβ ratio is steadily decreasing while Hγ/Hβ remains nearly constant, and (3) the low-ionization line ratios formed in the shocked knots have been in decline in different ways at various locations. We show that the first two of these results might be expected if the symbiotic central star has been active and if its bright Hα line has faded significantly in the past 20 years.

  11. Evidence for Widespread 26Al in the Solar Nebula and Constraints for Nebula Time Scales

    Russell; Srinivasan; Huss; Wasserburg; MacPherson

    1996-08-09

    A search was made for 26Mg (26Mg*) from the decay of 26Al (half-life = 0.73 million years) in Al-rich objects from unequilibrated ordinary chondrites. Two Ca-Al-rich inclusions (CAIs) and two Al-rich chondrules (not CAIs) were found that contained 26Al when they formed. Internal isochrons for the CAIs yielded an initial 26Al/27Al ratio [(26Al/27Al)0] of 5 x 10(-5), indistinguishable from most CAIs in carbonaceous chondrites. This result shows that CAIs with this level of 26Al are present throughout the classes of chondrites and strengthens the notion that 26Al was widespread in the early solar system. The two Al-rich chondrules have lower 26Mg*, corresponding to a (26Al/27Al)0 ratio of approximately 9 x 10(-6). Five other Al-rich chondrules contain no resolvable 26Mg*. If chondrules and CAIs formed from an isotopically homogeneous reservoir, then the chondrules with 26Al must have formed or been last altered approximately2 million years after CAIs formed; the 26Mg*-free chondrules formed >1 to 3 million years later still. Because 26Mg*-containing and 26Mg*-free chondrules are both found in Chainpur, which was not heated to more than approximately400°C, it follows that parent body metamorphism cannot explain the absence of 26Mg* in some of these chondrules. Rather, its absence indicates that the lifetime of the solar nebula over which CAIs and chondrules formed extended over approximately5 million years.

  12. The Reflective Learning Continuum: Reflecting on Reflection

    Peltier, James W.; Hay, Amanda; Drago, William

    2005-01-01

    The importance of reflection to marketing educators is increasingly recognized. However, there is a lack of empirical research that considers reflection within the context of both the marketing and general business education literature. This article describes the use of an instrument that can be used to measure four identified levels of a…

  13. 146Sm-142Nd systematics measured in enstatite chondrites reveals a heterogeneous distribution of 142Nd in the solar nebula.

    Gannoun, Abdelmouhcine; Boyet, Maud; Rizo, Hanika; El Goresy, Ahmed

    2011-05-10

    The short-lived (146)Sm-(142)Nd chronometer (T(1/2) = 103 Ma) is used to constrain the early silicate evolution of planetary bodies. The composition of bulk terrestrial planets is then considered to be similar to that of primitive chondrites that represent the building blocks of rocky planets. However for many elements chondrites preserve small isotope differences. In this case it is not always clear to what extent these variations reflect the isotope heterogeneity of the protosolar nebula rather than being produced by the decay of parent isotopes. Here we present Sm-Nd isotopes data measured in a comprehensive suite of enstatite chondrites (EC). The EC preserve (142)Nd/(144)Nd ratios that range from those of ordinary chondrites to values similar to terrestrial samples. The EC having terrestrial (142)Nd/(144)Nd ratios are also characterized by small (144)Sm excesses, which is a pure p-process nuclide. The correlation between (144)Sm and (142)Nd for chondrites may indicate a heterogeneous distribution in the solar nebula of p-process matter synthesized in supernovae. However to explain the difference in (142)Nd/(144)Nd ratios, 20% of the p-process contribution to (142)Nd is required, at odds with the value of 4% currently proposed in stellar models. This study highlights the necessity of obtaining high-precision (144)Sm measurements to interpret properly measured (142)Nd signatures. Another explanation could be that the chondrites sample material formed in different pulses of the lifetime of asymptotic giant branch stars. Then the isotope signature measured in SiC presolar would not represent the unique s-process signature of the material present in the solar nebula during accretion.

  14. A detailed study of the structure of the nested planetary nebula, Hb 12, the Matryoshka nebula

    Clark, D. M.; López, J. A. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Campus Ensenada, Ensenada, Baja California, 22860 (Mexico); Edwards, M. L. [LBT Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Winge, C., E-mail: dmclark@astrosen.unam.mx, E-mail: jal@astrosen.unam.mx, E-mail: medwards@lbto.org, E-mail: cwinge@gemini.edu [Gemini Observatory, Southern Operations Center, c/o AURA Inc., Casilla 603, La Serena (Chile)

    2014-11-01

    We present near-IR, integral field spectroscopic observations of the planetary nebula (PN) Hb 12 using Near-infrared Integral Field Spectrograph (NIFS) on Gemini-North. Combining NIFS with the adaptive optics system Altair, we provide a detailed study of the core and inner structure of this PN. We focus the analysis in the prominent emission lines [Fe II] (1.6436 μm), He I (2.0585 μm), H{sub 2} (2.1214 μm), and Br{sub γ} (2.16553 μm). We find that the [Fe II] emission traces a tilted system of bipolar lobes, with the northern lobe being redshifted and the southern lobe blueshifted. The [Fe II] emission is very faint at the core and only present close to the systemic velocity. There is no H{sub 2} emission in the core, whereas the core is prominent in the He I and Br{sub γ} recombination lines. The H{sub 2} emission is concentrated in equatorial arcs of emission surrounding the core and expanding at ∼30 km s{sup –1}. These arcs are compared with Hubble Space Telescope images and shown to represent nested loops belonging to the inner sections of a much larger bipolar structure that replicates the inner one. The He I and Br{sub γ} emission from the core clearly show a cylindrical central cavity that seems to represent the inner walls of an equatorial density enhancement or torus. The torus is 0.''2 wide (≡200 AU radius at a distance of 2000 pc) and expanding at ≤30 km s{sup –1}. The eastern wall of the inner torus is consistently more intense than the western wall, which could indicate the presence of an off-center star, such as is observed in the similar hourglass PN, MyCn 18. A bipolar outflow is also detected in Br{sub γ} emerging within 0.''1 from the core at ∼ ± 40 km s{sup –1}.

  15. Reflective photovoltaics

    Lentine, Anthony L.; Nielson, Gregory N.; Cruz-Campa, Jose Luis; Okandan, Murat; Goeke, Ronald S.

    2018-03-06

    A photovoltaic module includes colorized reflective photovoltaic cells that act as pixels. The colorized reflective photovoltaic cells are arranged so that reflections from the photovoltaic cells or pixels visually combine into an image on the photovoltaic module. The colorized photovoltaic cell or pixel is composed of a set of 100 to 256 base color sub-pixel reflective segments or sub-pixels. The color of each pixel is determined by the combination of base color sub-pixels forming the pixel. As a result, each pixel can have a wide variety of colors using a set of base colors, which are created, from sub-pixel reflective segments having standard film thicknesses.

  16. Nebula--a web-server for advanced ChIP-seq data analysis.

    Boeva, Valentina; Lermine, Alban; Barette, Camille; Guillouf, Christel; Barillot, Emmanuel

    2012-10-01

    ChIP-seq consists of chromatin immunoprecipitation and deep sequencing of the extracted DNA fragments. It is the technique of choice for accurate characterization of the binding sites of transcription factors and other DNA-associated proteins. We present a web service, Nebula, which allows inexperienced users to perform a complete bioinformatics analysis of ChIP-seq data. Nebula was designed for both bioinformaticians and biologists. It is based on the Galaxy open source framework. Galaxy already includes a large number of functionalities for mapping reads and peak calling. We added the following to Galaxy: (i) peak calling with FindPeaks and a module for immunoprecipitation quality control, (ii) de novo motif discovery with ChIPMunk, (iii) calculation of the density and the cumulative distribution of peak locations relative to gene transcription start sites, (iv) annotation of peaks with genomic features and (v) annotation of genes with peak information. Nebula generates the graphs and the enrichment statistics at each step of the process. During Steps 3-5, Nebula optionally repeats the analysis on a control dataset and compares these results with those from the main dataset. Nebula can also incorporate gene expression (or gene modulation) data during these steps. In summary, Nebula is an innovative web service that provides an advanced ChIP-seq analysis pipeline providing ready-to-publish results. Nebula is available at http://nebula.curie.fr/ Supplementary data are available at Bioinformatics online.

  17. Evolution of extra-galactic nebulae and the origin of metagalactic radio noise

    Bruce, C.E.R.

    1975-01-01

    It is pointed out that the discovery of the 'jet' in the radio source NGC 4486 fulfils a prediction made many years ago that such 'jets' would exist in some globular or elliptical nebulae. They are the channels of electrical discharges on a nebular scale then postulated, which will last for about 10 million years. It is emphasized that the discharge hypothesis would account for - 1. the existence of irregular nebulae; 2. the 'cataclysmic action' which Hubble regarded as required to account for the transition from nebulae of Type E to Type Sa; 3. the fact that the arms of spiral nebulae are never seen in process of formation; 4. the gathering of the matter towards the discharge channels by magnetic pinch effect; 5. the frequent occurrence of two diametrically opposed major arms; 6. the origin of radio waves throughout an extensive volume of space surrounding the 'jet' or discharge channel in NGC 4486; 7. the effect of one extra galactic nebula, NGC 3187, on another, NGC 3190; 8. the existence of diffuse patches of luminosity, 'emission nebulae', in the spiral arms of our own galaxy and in those of the 'Andromeda Nebula'. On the discharge theory about one per cent of all nebulae will be passing through the discharge phase at any one time, i.e., the number required to account for the observed intensity of metagalactic radio noise. (author)

  18. On planetary nebulae and Wolf-Rayet stars in the galactic-centre field

    Allen, D.A.

    1979-01-01

    A UK Schmidt objective-prism plate of the Galactic-centre field has been examined. Of the 74 objects in the field which have been catalogued as planetary nebulae, only half appear correctly classified; the others include Be stars, symbiotic stars, and stars without emission lines. A further 19 planetary nebulae and two Wolf-Rayet stars have been discovered. (author)

  19. Three-Dimensional Adaptive Mesh Refinement Simulations of Point-Symmetric Nebulae

    Rijkhorst, E.-J.; Icke, V.; Mellema, G.; Meixner, M.; Kastner, J.H.; Balick, B.; Soker, N.

    2004-01-01

    Previous analytical and numerical work shows that the generalized interacting stellar winds model can explain the observed bipolar shapes of planetary nebulae very well. However, many circumstellar nebulae have a multipolar or point-symmetric shape. With two-dimensional calculations, Icke showed

  20. Abundances of Planetary Nebulae IC 418, IC 2165 and NGC 5882

    Pottasch, [No Value; Bernard-Salas, J; Beintema, DA; Feibelman, WA

    The ISO and IUE spectra of the elliptical nebulae NGC 5882, IC 418 and IC 2165 are presented. These spectra are combined with the spectra in the visual wavelength region to obtain a complete, extinction corrected, spectrum. The chemical composition of the nebulae is then calculated and compared to

  1. Dark-Matter Content of Early-Type Galaxies with Planetary Nebulae

    Napolitano, N.R.; Romanowsky, A.J.; Coccato, L; Capaccioli, M.; Douglas, N.G.; Noordermeer, E.; Merrifield, M.R.; Kuijken, K.; Arnaboldi, M.; Gerhard, O.; Freeman, K.C.; De Lorenzi, F.; Das, P.

    2007-01-01

    Abstract. We examine the dark matter properties of nearby early-type galaxies using plane- tary nebulae (PNe) as mass probes. We have designed a specialised instrument, the Planetary Nebula Spectrograph (PN.S) operating at the William Herschel telescope, with the purpose of measuring PN velocities

  2. Characteristics of planetary nebulae and H II regions based on lambda = 1. 35 cm continuum measurements

    Braz, M A; Jardim, J O; Kaufmann, P [Universidade Mackenzie, Sao Paulo (Brazil). Centro de Radio-Astronomia et Astrofisica

    1975-11-01

    Physical parameters are derived and discussed for stronger H II regions and planetary nebulae for which continuum radio data at lambda = 1.35 cm was obtained. The study includes southern hemisphere planetary nebulae IC-418, NGC-6,302, NGC-6,369, and H II regions RCW-65, RCW-87, RCW-99, H 2-3 and H 2-6.

  3. PPAK integral field spectroscopy survey of the Orion nebula. Data release

    Sánchez, S. F.; Cardiel, N.; Verheijen, M. A. W.; Martín-Gordón, D.; Vilchez, J. M.; Alves, J.

    2007-01-01

    Aims:We present a low-resolution spectroscopic survey of the Orion nebula. The data are released for public use. We show the possible applications of this dataset analyzing some of the main properties of the nebula. Methods: We perform an integral field spectroscopy mosaic of an area of ~5 arcmin× 6

  4. Planetary nebulae and Wolf-Rayet stars in the galactic-centre field

    Allen, D A [Anglo-Australian Observatory, Epping (Australia)

    1979-06-01

    A UK Schmidt objective-prism plate of the Galactic-centre field has been examined. Of the 74 objects in the field which have been catalogued as planetary nebulae, only half appear correctly classified; the others include Be stars, symbiotic stars, and stars without emission lines. A further 19 planetary nebulae and two Wolf-Rayet stars have been discovered.

  5. Radio synthesis observations of planetary nebulae. II. A search for sub-arcsecond structure

    Balick, B.; Terzian, Y.

    1976-01-01

    Observations of 11 planetary nebulae with spatial resolutions from 0''.2 to 2'' at 2695 and 8085 MHz failed to show any very bright structure smaller than about 2''. The observations are shown to be consistent with the present understanding of the temperatures and density distributions thought to typify most planetary nebulae

  6. Broadband x-ray imaging and spectroscopy of the crab nebula and pulsar with NuSTAR

    Madsen, Kristin K.; Reynolds, Stephen; Harrison, Fiona

    2015-01-01

    We present broadband (3-78 keV) NuSTAR X-ray imaging and spectroscopy of the Crab nebula and pulsar. We show that while the phase-averaged and spatially integrated nebula + pulsar spectrum is a power law in this energy band, spatially resolved spectroscopy of the nebula finds a break at ~9 ke...

  7. Cooling and quasi-static contraction of the primitive solar nebula after gas accretion

    Watanabe, Seichiro; Nakagawa, Yoshitsugu; Nakazawa, Kiyoshi

    1990-01-01

    The evolution of the primitive solar nebula in the quasi-static contraction phase where the nebula cools down toward the thermal steady state is studied. The solar irradiation onto the nebula keeps the surface temperature constant, so that the convective ozone retreats from the surface as the nebula cools. Thus if thermal convection is the only source of turbulence, convection will quiet down in an early time of the cooling. Afterward, the nebula evolves toward an isothermal structure in a time scale of 1000 yr. The cooling rates in the vicinity of the midplate at 1 AU are 0.003 K/hr at T(c) = 1000 K and 3 x 10 to the -5th K/hr at T(c) = 300 K for the standard model. If some turbulence exists irrespective of convection, convection may continue for sufficiently strong turbulent heating. 39 refs

  8. Helium shell flashes and ionization of planetary nebulae. Pt. 2. FG Sge

    Tylenda, R.

    1980-01-01

    Theoretical models have been constructed to study time-dependent effects in the nebulae (He 1-5) associated with FG Sge. Two cases have been considered: recombination of an initially stationary nebula of moderate excitation (Case A), and nonequilibrium ionization (and subsequent recombination) of an initially neutral nebula by a thermal pulse in the central star (Case B). Comparison with the observed spectrum does not allow to distinguish definitely between both cases. There are slight indications that the present state of He 1-5 is better reproduced in Case B which is also preferable from the point of view of the present theoretical knowledge of observational appearances of helium shell flashes in planetary nebula nuclei. The nebula has a normal chemical composition. (author)

  9. Emission lines of Mg2 and Ca2 in planetary nebulae

    Gurzadyan, G.A.

    1979-01-01

    Conditions of exciting resonance lines in the emission of ionized magnesium (lambda lambda 2796+2803 Mg2) and calcium (lambda lambda 3934+3968 Ca2) in planetary nebulae have been analyzed. It is shown that the allowed lines are excited with the same mechanism, as the forbidden lines, i.e. inelastic electron collisions, but not with common fluorescence. The emission line lambda 2800 Mg2 of enough force can be observed only in the spectra of planetary nebulae with mean excitation (IC 2149) as well as in the spectra of diffuse nebulae. The line must not be observed in high-excited planetary nebulae (NGC 7026, 7662). The absence of emission lines H and K Ca2 in planetary nebulae spectra results from the fact, that their expected intensity is by 3-4 orders less than the intensity of the line lambda 2800 Mg2 or Hsub(β) hydrogen

  10. SHAPING THE GLOWING EYE PLANETARY NEBULA, NGC 6751

    Clark, D. M.; Garcia-Diaz, Ma. T.; Lopez, J. A.; Steffen, W. G.; Richer, M. G.

    2010-01-01

    NGC 6751 is a highly structured multiple-shell planetary nebula (PN) with a bipolar outflow. In this work, we present a comprehensive set of spatially resolved, high spectral resolution, long-slit spectra and deep imaging from San Pedro Martir, Gemini, the Hα composite full sky survey and archive images from the Hubble Space Telescope and Spitzer. This material allows us to identify all the main morphological components and study their detailed kinematics. We find a thick equatorial structure fragmented into multiple knots that enclose a fast expanding bubble with a filamentary surface structure. The knotty ring is surrounded by faint emission from a disk-like envelope. Lobes with embedded filaments form a bipolar outflow. The equatorial ring is tilted with respect to the line of sight and with respect to the bipolar outflow. A spherical halo surrounds the PN and there is material further out identified as a fragmented outer halo. This information is used to derive a three-dimensional morpho-kinematic model using the code SHAPE that closely replicates the observed image and long-slit spectra of the nebula, providing a fair representation of its complex structure. NGC 6751 is located close to the galactic plane and its large-scale surrounding environment is shown to be a gas-rich region. We find indications that the PN is interacting with the interstellar medium. Emission components from an extended nebulosity located a couple of arcminutes away from the nebula have radial velocities that are inconsistent with the rest of NGC 6751 and are confirmed as originating from the ambient material, not related to the PN, in agreement with a previous suggestion.

  11. Infrared polarimetry of the reflection nebula near L 1551 IRS 5

    Nagata, Tetsuya; Yamashita, Takuya; Sato, Shuji; Suzuki, Hiro; Hough, J H; Garden, R; Gatley, I

    1986-11-01

    The K-band polarization has been measured in the region extending 30 arcsec to the SW of L 1551 IRS5. The degree of polarization is exceptionally high, reaching approx. 67 per cent. The large polarizations and the azimuthal pattern of the position angles are attributed to scattering of infrared radiation from IRS5 by dust grains. The infrared brightness distribution resembles that of the optical nebulosity. It is proposed that infrared scattering occurs at the 'walls' of a cavity formed by the interaction of stellar winds with the ambient cloud.

  12. Reflection nebulae in the Galactic center: soft X-ray imaging polarimetry

    Marin, Frederic; Muleri, F.; Soffitta, P.; Karas, Vladimír; Kunneriath, Devaky

    2015-01-01

    Roč. 576, April (2015), A19/1-A19/7 ISSN 0004-6361 R&D Projects: GA MŠk LD12010; GA ČR(CZ) GC13-00070J Institutional support: RVO:67985815 Keywords : Galaxy * nucleus * structure Subject RIV: BN - Astronomy, Celestial Mechanics, Astrophysics Impact factor: 4.378, year: 2014

  13. IRAS observations of the ISM in the gamma CAS reflection nebula

    Buss, Richard H., Jr.; Werner, Michael W.

    1990-01-01

    Mid-infrared emission from other galaxies originates both from interstellar grains heated by diffuse starlight and local excitation of grains by hot OB stars. Thus, a detailed examination of the Infrared Astronomy Satellite (IRAS) data from a B star interacting with the interstellar medium (ISM) could provide insight into infrared (IR) emission processes in external galaxies. Researchers have therefore used IRAS data to study the B0 IVe star gamma Cas and its surroundings, which they find to exhibit evidence of grain heating, destruction, and possible star formation.

  14. Nebula: reconstruction and visualization of scattering data in reciprocal space.

    Reiten, Andreas; Chernyshov, Dmitry; Mathiesen, Ragnvald H

    2015-04-01

    Two-dimensional solid-state X-ray detectors can now operate at considerable data throughput rates that allow full three-dimensional sampling of scattering data from extended volumes of reciprocal space within second to minute time-scales. For such experiments, simultaneous analysis and visualization allows for remeasurements and a more dynamic measurement strategy. A new software, Nebula , is presented. It efficiently reconstructs X-ray scattering data, generates three-dimensional reciprocal space data sets that can be visualized interactively, and aims to enable real-time processing in high-throughput measurements by employing parallel computing on commodity hardware.

  15. Interstellar Organics, the Solar Nebula, and Saturn's Satellite Phoebe

    Pendleton, Y. J.; Cruikshank, D. P.

    2014-01-01

    The diffuse interstellar medium inventory of organic material (Pendleton et al. 1994, Pendleton & Allamandola 2002) was likely incorporated into the molecular cloud in which the solar nebula condensed. This provided the feedstock for the formation of the Sun, major planets, and the smaller icy bodies in the region outside Neptune's orbit (transneptunian objects, or TNOs). Saturn's satellites Phoebe, Iapetus, and Hyperion open a window to the composition of one class of TNO as revealed by the near-infrared mapping spectrometer (VIMS) on the Cassini spacecraft at Saturn. Phoebe (mean diameter 213 km) is a former TNO now orbiting Saurn. VIMS spaectral maps of PHoebe's surface reveal a complex organic spectral signature consisting of prominent aromatic (CH) and alophatic hydrocarbon (CH2, CH3) absorption bands (3.2-3.6 micrometers). Phoebe is the source of a huge debris ring encircling Saturn, and from which particles (approximately 5-20 micrometer size) spiral inward toward Saturn. They encounter Iapetus and Hperion where they mix with and blanket the native H2O ice of those two bodies. Quantitative analysis of the hydrocarbon bands on Iapetus demonstrates that aromatic CH is approximately 10 times as abundant as aliphatic CH2+CH3, significantly exceeding the strength of the aromatic signature in interplanetary dust particles, comet particles, ad in carbonaceous meteorites (Cruikshank et al. 2013). A similar excess of aromatics over aliphatics is seen in the qualitative analysis of Hyperion and Phoebe itself (Dalle Ore et al. 2012). The Iapetus aliphatic hydrocarbons show CH2/CH3 approximately 4, which is larger than the value found in the diffuse ISM (approximately 2-2.5). In so far as Phoebe is a primitive body that formed in the outer regions of the solar nebula and has preserved some of the original nebula inventory, it can be key to understanding the content and degree of procesing of the nebular material. There are other Phoebe-like TNOs that are presently

  16. Stellar outflow: relative motions of nebulae and Of stars

    Lynds, B.T.

    1979-01-01

    On the basis of arguments presented by Roberts (1972) and of Shu et al. (1972), Minn and Greenberg (1973) argued that the velocity differences between newly formed hot stars and the surrounding interstellar medium are sufficiently different so that typical H II regions should consist of material which is continually being replaced by the ambient medium and which should therefore possess the velocity of the medium rather than that of the star. The critical test of this hypothesis will be a comparison of nebular velocities with the velocities of the exciting stars. This is performed for Of stars and nebulae. (Auth.)

  17. Near-infrared imaging polarimetry of bipolar nebulae: Pt. 1

    Minchin, N.R.; Hough, J.H.; McCall, A.; Burton, M.G.; McCaughrean, M.J.; Aspin, C.; Bailey, J.A.; Axon, D.J.; Sato, Shuji

    1991-01-01

    New high-spatial-resolution polarization images of the BN-KL region of OMC-1 from 1.25-3.6 μm are presented. At the longer wavelengths these show a centro-symmetric polarization vector pattern, centred mainly on IRc2, and high degrees of polarization across the nebula, confirming that the diffuse nebulosity is dominated by the scattering of radiation, mainly from IRc2. Degrees of polarization, position angles and magnitudes are given for the observable IRc sources. These are discussed. (author)

  18. Pulsating stars in the region of Carina Nebula

    Steslicki, Marek [Astronomical Institute, University of Wroclaw (Poland)], E-mail: steslicki@astro.uni.wroc.p1

    2008-10-15

    We present the results of a search for pulsating stars in the region of Carina Nebula which includes three very young open clusters: Trumpler 14, 15 and 16. The search was made with the Wide Field Imager (WFI) on the MPG/ESO 2.2-m telescope in La Silla (Chile). In total, about 16,000 stars have been analyzed using classical Fourier techniques. We found over 20 pulsating {delta}-Scuti type stars in this region. Most of them are probable members of open clusters at the pre-main sequence evolutionary stage.

  19. Model atmospheres and parameters of central stars of planetary nebulae

    Patriarchi, P.; Cerruti-sola, M.; Perinotto, M.

    1989-01-01

    Non-LTE hydrogen and helium model atmospheres have been obtained for temperatures and gravities relevant to the central stars of planetary nebulae. Low-resolution and high-resolution observations obtained by the IUE satellite have been used along with optical data to determine Zanstra temperatures of the central stars of NGC 1535, NGC 6210, NGC 7009, IC 418, and IC 4593. Comparison of the observed stellar continuum of these stars with theoretical results allowed further information on the stellar temperature to be derived. The final temperatures are used to calculate accurate stellar parameters. 62 refs

  20. Flare stars of the Orion Nebula - spectra of an outburst

    Carter, B.D.; O'Mara, B.J.; Ross, J.E.

    1988-01-01

    For the first time, detailed, time-resolved spectra of a flare event of an Orion cluster flare star are presented. These spectra, covering ∼ λλ3600-4600, were obtained by using the Anglo-Australian Telescope with a fibre coupler to simultaneously monitor 23 flare stars in the region of the Orion Nebula. The flare spectra reveal continuous emission which filled in the photospheric Ca I 4226 A absorption, and hydrogen Balmer, Ca II H and K, He I 4026 A and He I 4471 A line emission. Overall, the spectral behaviour indicates similarities to strong outbursts of the classical dMe flare stars. (author)

  1. He 2-104 - A symbiotic proto-planetary nebula?

    Schwarz, H.E.; Aspin, C.; Lutz, J.H.

    1989-01-01

    CCD observations are presented for He 2-104, an object previously classified as both PN and symbiotic star, which show that this is in fact a protoplanetary nebula (PPN) with a dynamical age of about 800 yr. The presence of highly collimated jets, extending over 75 arcsec on the sky, combined with an energy distribution showing a hot as well as a cool component, indicates that He 2-104 is a binary PPN. Since the primary is probably a Mira with a 400-d period (as reported by Whitelock, 1988), it is proposed that the system is a symbiotic PPN. 16 refs

  2. Bi-Abundance Ionisation Structure of the Wolf-Rayet Planetary Nebula PB 8

    Danehkar, A.

    2018-01-01

    The planetary nebula PB 8 around a [WN/WC]-hybrid central star is one of planetary nebulae with moderate abundance discrepancy factors (ADFs 2-3), which could be an indication of a tiny fraction of metal-rich inclusions embedded in the nebula (bi-abundance). In this work, we have constructed photoionisation models to reproduce the optical and infrared observations of the planetary nebula PB 8 using a non-LTE stellar model atmosphere ionising source. A chemically homogeneous model initially used cannot predict the optical recombination lines. However, a bi-abundance model provides a better fit to most of the observed optical recombination lines from N and O ions. The metal-rich inclusions in the bi-abundance model occupy 5.6% of the total volume of the nebula, and are roughly 1.7 times cooler and denser than the mean values of the surrounding nebula. The N/H and O/H abundance ratios in the metal-rich inclusions are 1.0 and 1.7 dex larger than the diffuse warm nebula, respectively. To reproduce the Spitzer spectral energy distribution of PB 8, dust grains with a dust-to-gas ratio of 0.01 (by mass) were also included. It is found that the presence of metal-rich inclusions can explain the heavy element optical recombination lines, while a dual-dust chemistry with different grain species and discrete grain sizes likely produces the infrared continuum of this planetary nebula. This study demonstrates that the bi-abundance hypothesis, which was examined in a few planetary nebulae with large abundance discrepancies (ADFs > 10), could also be applied to those typical planetary nebulae with moderate abundance discrepancies.

  3. Personal Reflections

    Home; Journals; Resonance – Journal of Science Education. Personal Reflections. Articles in Resonance – Journal of Science Education. Volume 6 Issue 3 March 2001 pp 90-93 Personal Reflections. Why did I opt for Career in Science? Jayant V Narlikar · More Details Fulltext PDF. Volume 9 Issue 8 August 2004 pp 89-89 ...

  4. Reflection groups

    Eggermont, G.

    2006-01-01

    In 2005, PISA organised proactive meetings of reflection groups on involvement in decision making, expert culture and ethical aspects of radiation protection.All reflection group meetings address particular targeted audiences while the output publication in book form is put forward

  5. Reflection ciphers

    Boura, Christina; Canteaut, Anne; Knudsen, Lars Ramkilde

    2017-01-01

    study the necessary properties for this coupling permutation. Special care has to be taken of some related-key distinguishers since, in the context of reflection ciphers, they may provide attacks in the single-key setting.We then derive some criteria for constructing secure reflection ciphers...

  6. Quantifying Reflection

    Alcock, Gordon Lindsay

    2013-01-01

    ´ These are all based on Blooms taxonomy and levels of competence and form a major part of individual student and group learning portfolios. Key Words :Project-Based learning, Reflective Portfolios, Self assessment, Defining learning gains, Developing learning strategies , Reflections on and for learning....... It contrasts the students’ self-assessment in a range of ‘product’ skills such as Revit, Structural Design, Mathematics of construction, Technical Installations; as well as ‘process’ competencies such as ‘Working in a team’, Sharing knowledge, Maintaining a portfolio and Reflecting ON learning and FOR learning......This paper documents 1st semester student reflections on “learning to learn” in a team-based PBL environment with quantitative and qualitative student reflective feedback on the learning gains of 60 Architectural Technology and Construction Management students at VIA University College, Denmark...

  7. Ionization structure of planetary nebulae. Part 8: NGC 6826

    Barker, T.

    1987-01-01

    Spectrophotometric observations of emission-line intensities over the spectral range 1400 to 1700 A were made in seven positions in the planetary nebulae NCG 6826. The O(++) electron temperature varies little from 8900 K throughout the nebula; the Balmer continuum electron temperature averages 1500 K higher. The wavelength 4267 C II line intensities imply C(++) abundances that are systematically higher than those determined from the wavelength 1906, 1909 C III lines, but because of uncertainties in the intensities of the ultraviolet lines relative to the optical ones, this discrepancy is less conclusively demonstrated in NGC 6826 than in other planetaries in this series. Standard equations used to correct for the existence of elements in other than the optically observable ionization stages give results that are consistent and also in approximate agreement with abundances calculated using ultraviolet lines in the few cases where the relevant ultraviolet lines are measurable. The results of the logarithmic abundances differ somewhat from the recent study by Aller and Czyzak, in part because their measured electron temperatures are somewhat higher. The Ar, Ne, and, to some extent, O and S abundances appear to be somewhat low, suggesting that the progenitor to NGC 6826 like that to NGC 7662, may have formed out of somewhat metal-poor material

  8. Broad Halpha Wing Formation in the Planetary Nebula IC 4997.

    Lee; Hyung

    2000-02-10

    The young and compact planetary nebula IC 4997 is known to exhibit very broad wings with a width exceeding 5000 km s-1 around Halpha. We propose that the broad wings are formed through Rayleigh-Raman scattering that involves atomic hydrogen, by which Lybeta photons with a velocity width of a few 102 km s-1 are converted to optical photons and fill the Halpha broad wing region. The conversion efficiency reaches 0.6 near the line center, where the scattering optical depth is much larger than 1, and rapidly decreases in the far wings. Assuming that close to the central star there exists an unresolved inner compact core of high density, nH approximately 109-1010 cm-3, we use the photoionization code "CLOUDY" to show that sufficient Lybeta photons for scattering are produced. Using a top-hat-incident profile for the Lybeta flux and a scattering region with a H i column density NHi=2x1020 cm-2 and a substantial covering factor, we perform a profile-fitting analysis in order to obtain a satisfactory fit to the observed flux. We briefly discuss the astrophysical implications of the Rayleigh-Raman processes in planetary nebulae and other emission objects.

  9. The remarkably high excitation planetary nebula GC 6537.

    Aller, L H; Hung, S; Feibelman, W A

    1999-05-11

    NGC 6537 is an unusually high excitation point symmetric planetary nebula with a rich spectrum. Its kinematical structures are of special interest. We are here primarily concerned with the high resolution spectrum as revealed by the Hamilton echelle Spectrograph at Lick Observatory (resolution approximately 0.2 A) and supplemented by UV and near-UV data. These extensive data permit a determination of interstellar extinction, plasma diagnostics, and ionic concentrations. The photoionization models that have been used successfully for many planetary nebulae are not entirely satisfactory here. The plasma electron temperature of a photoionization model cannot much exceed 20,000 K, but plasma diagnostics show that regions emitting radiation of highly ionized atoms such as [NeIV] and [NeV] are much hotter, showing that shock excitation must be important, as suggested by the remarkable kinematics of this object. Hence, instead of employing a strict photoionization model, we are guided by the nebular diagnostics, which reveal how electron temperature varies with ionization potential and accommodates density effects. The predictions of the photoionization model may be useful in estimating ionization correction factor. In effect, we have estimated the chemical composition by using both photoionization and shock considerations.

  10. Planetesimal Sizes and Mars Formation in the Magnetized Solar Nebula

    Hasegawa, Yasuhiro; Morishima, Ryuji

    2017-10-01

    The Hf-W chronology inferred from Martian meteorites suggests that Mars should be a stranded planetary embryo formed within a very short (about 2 Myr) accretion timescale. Previous studies show that such rapid growth can be realized when small (nebular evolution. Under this circumstance, impact velocity of planetesimals can be very high due to nebular density fluctuations caused by turbulence, and hence collisions between small planetesimals can become destructive, rather than mergers. Here, we investigate how Mars formed in the magnetized solar nebula, focusing on MHD turbulence. We demonstrate what mass of planetesimals can contribute to Mars formation and what value of the nebular mass is needed to satisfy the rapid accretion timescale. We therefore derive a more realistic condition of the solar nebula under which Mars formation took place. While this study is based on the standard picture of runaway and oligarchic growth, we also discuss other formation mechanisms in order to compare how our results would be consistent with the properties of the solar system. These mechanisms are a hypothesis that Mars formed from a narrow ring of planetesimals, and the pebble accretion scenario.

  11. The Crab nebula's ''wisps'' as shocked pulsar wind

    Gallant, Y.A.; Arons, J.; Langdon, A.B.

    1992-01-01

    The Crab synchrotron nebula has been successfully modelled as the post-shock region of a relativistic, magnetized wind carrying most of the spindown luminosity from the central pulsar. While the Crab is the best-studied example, most of the highest spindown luminosity pulsars are also surrounded by extended synchrotron nebulae, and several additional supernova remnants with ''plerionic'' morphologies similar to the Crab are known where the central object is not seen. All these objects have nonthermal, power-law spectra attributable to accelerated high-energy particles thought to originate in a Crab-like relativistic pulsar wind. However, proposed models have so far treated the wind shock as an infinitesimally thin discontinuity, with an arbitrarily ascribed particle acceleration efficiency. To make further progress, investigations resolving the shock structure seemed in order. Motivated by these considerations, we have performed ''particle-in-cell (PIC) simulations of perpendicularly magnetized shocks in electron-positron and electron-positron-ion plasmas. The shocks in pure electron-positron plasmas were found to produce only thermal distributions downstream, and are thus poor candidates as particle acceleration sites. When the upstream plasma flow also contained a smaller population of positive ions, however, efficient acceleration of positrons, and to a lesser extent of electrons, was observed in the simulations

  12. Photoionization modeling of Magellanic Cloud planetary nebulae. I

    Dopita, M. A.; Meatheringham, S. J.

    1991-01-01

    The results of self-consistent photoionization modeling of 38 Magellanic Cloud PNe are presented and used to construct an H-R diagram for the central stars and to obtain both the nebular chemical abundances and the physical parameters of the nebulae. T(eff)s derived from nebular excitation analysis are in agreement with temperatures derived by the classical Zanstra method. There is a linear correlation between log T(eff) and the excitation class. The majority of the central stars in the sample with optically thick nebulae have masses between 0.55 and 0.7 solar mass and are observed during their hydrogen-burning excursion toward high temperatures. Optically thin objects are found scattered throughout the H-R diagram, but tend to have a somewhat smaller mean mass. Type I PN are found to have high core masses and to lie on the descending branch of the evolutionary tracks. The nebular mass of the optically thick objects is closely related to the nebular radius, and PN with nebular masses over one solar are observed.

  13. Version 2000 of the Catalogue of Galactic Planetary Nebulae

    Kohoutek, L.

    2001-11-01

    The ``Catalogue of Galactic Planetary Nebulae (Version 2000)'' appears in Abhandlungen aus der Hamburger Sternwarte, Band XII in the year 2001. It is a continuation of CGPN(1967) and contains 1510 objects classified as galactic PNe up to the end of 1999. The lists of possible pre-PNe and possible post-PNe are also given. The catalogue is restricted only to the data belonging to the location and identification of the objects. It gives identification charts of PNe discovered since 1965 (published in the supplements to CGPN) and those charts of objects discovered earlier, which have wrong or uncertain identification. The question ``what is a planetary nebula'' is discussed and the typical values of PNe and of their central stars are summarized. Short statistics about the discoveries of PNe are given. The catalogue is also available in the Centre de Données, Strasbourg and at Hamburg Observatory via internet. The Catalogue is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/378/843

  14. The Integral Field View of the Orion Nebula

    Adal Mesa-Delgado

    2014-01-01

    Full Text Available This paper reviews the major advances achieved in the Orion Nebula through the use of integral field spectroscopy (IFS. Since the early work of Vasconcelos and collaborators in 2005, this technique has facilitated the investigation of global properties of the nebula and its morphology, providing new clues to better constrain its 3D structure. IFS has led to the discovery of shock-heated zones at the leading working surfaces of prominent Herbig-Haro objects as well as the first attempt to determine the chemical composition of Orion protoplanetary disks, also known as proplyds. The analysis of these morphologies using IFS has given us new insights into the abundance discrepancy problem, a long-standing and unresolved issue that casts doubt on the reliability of current methods used for the determination of metallicities in the universe from the analysis of H II regions. Results imply that high-density clumps and high-velocity flows may play an active role in the production of such discrepancies. Future investigations based on the large-scale IFS mosaic of Orion will be very valuable for exploring how the integrated effect of small-scale structures may have impact at larger scales in the framework of star-forming regions.

  15. GRAVITATIONAL COLLAPSE AND FILAMENT FORMATION: COMPARISON WITH THE PIPE NEBULA

    Heitsch, Fabian; Ballesteros-Paredes, Javier; Hartmann, Lee

    2009-01-01

    Recent models of molecular cloud formation and evolution suggest that such clouds are dynamic and generally exhibit gravitational collapse. We present a simple analytic model of global collapse onto a filament and compare this with our numerical simulations of the flow-driven formation of an isolated molecular cloud to illustrate the supersonic motions and infall ram pressures expected in models of gravity-driven cloud evolution. We compare our results with observations of the Pipe Nebula, an especially suitable object for our purposes as its low star formation activity implies insignificant perturbations from stellar feedback. We show that our collapsing cloud model can explain the magnitude of the velocity dispersions seen in the 13 CO filamentary structure by Onishi et al. and the ram pressures required by Lada et al. to confine the lower-mass cores in the Pipe Nebula. We further conjecture that higher-resolution simulations will show small velocity dispersions in the densest core gas, as observed, but which are infall motions and not supporting turbulence. Our results point out the inevitability of ram pressures as boundary conditions for molecular cloud filaments, and the possibility that especially lower-mass cores still can be accreting mass at significant rates, as suggested by observations.

  16. Gigahertz-peaked spectra pulsars in Pulsar Wind Nebulae

    Basu, R.; RoŻko, K.; Kijak, J.; Lewandowski, W.

    2018-04-01

    We have carried out a detailed study of the spectral nature of six pulsars surrounded by pulsar wind nebulae (PWNe). The pulsar flux density was estimated using the interferometric imaging technique of the Giant Metrewave Radio Telescope at three frequencies 325, 610, and 1280 MHz. The spectra showed a turnover around gigahertz frequency in four out of six pulsars. It has been suggested that the gigahertz-peaked spectrum (GPS) in pulsars arises due to thermal absorption of the pulsar emission in surrounding medium like PWNe, H II regions, supernova remnants, etc. The relatively high incidence of GPS behaviour in pulsars surrounded by PWNe imparts further credence to this view. The pulsar J1747-2958 associated with the well-known Mouse nebula was also observed in our sample and exhibited GPS behaviour. The pulsar was detected as a point source in the high-resolution images. However, the pulsed emission was not seen in the phased-array mode. It is possible that the pulsed emission was affected by extreme scattering causing considerable smearing of the emission at low radio frequencies. The GPS spectra were modelled using the thermal free-free absorption and the estimated absorber properties were largely consistent with PWNe. The spatial resolution of the images made it unlikely that the point source associated with J1747-2958 was the compact head of the PWNe, but the synchrotron self-absorption seen in such sources was a better fit to the estimated spectral shape.

  17. Two different sources of water for the early solar nebula.

    Kupper, Stefan; Tornow, Carmen; Gast, Philipp

    2012-06-01

    Water is essential for life. This is a trivial fact but has profound implications since the forming of life on the early Earth required water. The sources of water and the related amount of delivery depend not only on the conditions on the early Earth itself but also on the evolutionary history of the solar system. Thus we ask where and when water formed in the solar nebula-the precursor of the solar system. In this paper we explore the chemical mechanics for water formation and its expected abundance. This is achieved by studying the parental cloud core of the solar nebula and its gravitational collapse. We have identified two different sources of water for the region of Earth's accretion. The first being the sublimation of the icy mantles of dust grains formed in the parental cloud. The second source is located in the inner region of the collapsing cloud core - the so-called hot corino with a temperature of several hundred Kelvin. There, water is produced efficiently in the gas phase by reactions between neutral molecules. Additionally, we analyse the dependence of the production of water on the initial abundance ratio between carbon and oxygen.

  18. The chemical composition of three planetary nebulae in the Magellanic clouds

    Dufour, R.J.; Killen, R.M.

    1977-01-01

    Emission-line intensities in the planetary nebulae Henize 67 in the Small Magellanic Cloud (SMC) and Henize 97 and 153 in the LMC along with the small SMC H II regions Henize 9, 61, and 81 were measured from photographic image-tube spectra taken with the 1.5 m telescope at Cerro Tololo. The relative abundances of H, He, N, O, Ne, S, and Ar in the nebulae were estimated and compared with the compositions of galactic planetary nebulae and previously studied H II regions in the Clouds. The results show that (1) the N/O ratios in the planetary nebulae are substantially higher than found in the H II regions of each Cloud; (2) He/H approx. = 0.18 in the SMC planetary nebula, but seems normal (approx.0.10) in the two LMC planetaries; and (3) the compositions of the three small SMC H II regions are similar to that of larger SMC H II regions studied previously. It is concluded that the N/H values in the shells of planetary nebulae may not depend on the metal content of the progenitor star as much as recent theoretical models suggest and that the N content of the gas in the Magellanic Clouds arises primarily from sources other than planetary nebulae

  19. Model planetary nebulae: the effect of shadowed filaments on low ionization potential ion radiation

    Katz, A.

    1977-01-01

    Previous homogeneous model planetary nebulae calculations No. 4 have yielded emission strengths for low ionization potential No. 4 ions which are considerably lower than those observed. Several attempts were to correct this problem by the inclusion of optically thin condensations, the use of energy flux distributions from stellar model calculations instead of blackbody spectrum stars, and the inclusion of dust in the nebulae. The effect that shadowed filaments have on the ionization and thermal structure of model nebulae and the resultant line strengths are considered. These radial filaments are shielded from the direct stellar ionizing radiation by optically thick condensations in the nebula. Theoretical observational evidence exists for the presence of condensations and filaments. Since the only source of ionizing photons in the shadowed filaments is due to diffuse photons produced by recombination, ions of lower ionization potential are expected to exist there in greater numbers than those found in the rest of the nebula. This leads to increased line strengths from these ions and increases their values to match the observational values. It is shown that these line strengths in the filaments increase by over one to two orders of magnitude relative to values found in homogeneous models. This results in an increase of approximately one order of magnitude for these lines when contributions from both components of the nebula are considered. The parameters that determine the exact value of the increase are the radial location of the filaments in the nebula and the fraction of the nebular volume occupied by the filaments

  20. A Self-Perpetuating Catalyst for the Production of Complex Organic Molecules in Protostellar Nebulae

    Nuth, Joseph A.; Johnson, N. M.

    2010-01-01

    The formation of abundant carbonaceous material in meteorites is a long standing problem and an important factor in the debate on the potential for the origin of life in other stellar systems. Many mechanisms may contribute to the total organic content in protostellar nebulae, ranging from organics formed via ion-molecule and atom-molecule reactions in the cold dark clouds from which such nebulae collapse, to similar ion-molecule and atom-molecule reactions in the dark regions of the nebula far from the proto star, to gas phase reactions in sub-nebulae around growing giant planets and in the nebulae themselves. The Fischer-Tropsch-type (FTT) catalytic reduction of CO by hydrogen was once the preferred model for production of organic materials in the primitive solar nebula. The Haber-Bosch catalytic reduction of N2 by hydrogen was thought to produce the reduced nitrogen found in meteorites. However, the clean iron metal surfaces that catalyze these reactions are easily poisoned via reaction with any number of molecules, including the very same complex organics that they produce and both reactions work more efficiently in the hot regions of the nebula. We have demonstrated that many grain surfaces can catalyze both FTT and HB-type reactions, including amorphous iron and magnesium silicates, pure silica smokes as well as several minerals. Although none work as well as pure iron grains, and all produce a wide range of organic products rather than just pure methane, these materials are not truly catalysts.

  1. Structure of the solar nebula, growth and decay of magnetic fields and effects of magnetic and turbulent viscosities on the nebula

    Hayashi, Chushiro

    1982-01-01

    First, distributions of surface densities of dust materials and gases in a preplanetary solar nebula, which give a good fit to the distribution of the planetary mass, are presented and the over-all structure of this nebula, which is in thermal and gravitational equilibrium, is studied. Second, in order to see magnetic effect on the structure, electric conductivity of a gas ionized by cosmic rays and radioactivities contained in dust grains is estimated for each region of the nebula and, then, the growth and decay of seed magnetic fields, which are due to differential rotation of the nebula and to the Joule dissipation, respectively, are calculated. The results indicate that, in regions of the terrestrial planets, magnetic fields decay much faster than they grow and magnetic effects can be ignored, except for the outermost layers of very low density. This is not the case for regions of Uranus and Neptune where magnetic fields can be amplified to considerable extents. Third, the transport of angular momentum due to magnetic and mechanical turbulent viscosities and the resultant redistribution of surface density in the nebula are investigated. The results show that the density redistribution occurs, in general, in a direction to attain a distribution of surface density which has nearly the same ν-dependence as that obtained from the present distribution of the planetary mass. This redistribution seems to be possible if it occurs at a formation stage of the nebula where the presence of large viscosities is expected. Finally, a comment is given on the initial condition of a collapsing interstellar cloud from which the solar nebula is formed at the end of the collapse. (author)

  2. Registration of H2O and SiO masers in the Calabash Nebula to confirm the planetary nebula paradigm

    Dodson, R.; Rioja, M.; Bujarrabal, V.; Kim, J.; Cho, S. H.; Choi, Y. K.; Youngjoo, Y.

    2018-05-01

    We report on the astrometric registration of very long baseline interferometry images of the SiO and H2O masers in OH 231.8+4.2, the iconic proto-planetary nebula also known as the Calabash nebula, using the Korean VLBI Network and source frequency phase referencing. This, for the first time, robustly confirms the alignment of the SiO masers, close to the asymptotic giant branch star, driving the bilobe structure with the water masers in the outflow. We are able to trace the bulk motions for the H2O masers over the last few decades to be 19 km s-1 and deduce that the age of this expansion stage is 38 ± 2 yr. The combination of this result with the distance allows a full 3D reconstruction and confirms that the H2O masers lie on and expand along the known large-scale symmetry axis and that the outflow is only a few decades old, so mass loss is almost certainly ongoing. Therefore, we conclude that the SiO emission marks the stellar core of the nebular, the H2O emission traces the expansion, and there must be multiple epochs of ejection to drive the macro-scale structure.

  3. Planetary nebulae: understanding the physical and chemical evolution of dying stars.

    Weinberger, R; Kerber, F

    1997-05-30

    Planetary nebulae are one of the few classes of celestial objects that are active in every part of the electromagnetic spectrum. These fluorescing and often dusty expanding gaseous envelopes were recently found to be quite complex in their dynamics and morphology, but refined theoretical models can account for these discoveries. Great progress was also made in understanding the mechanisms that shape the nebulae and the spectra of their central stars. In addition, applications for planetary nebulae have been worked out; for example, they have been used as standard candles for long-range distances and as tracers of the enigmatic dark matter.

  4. The colorimetry of the nebulae NGC 6914b and Parsamian 22

    Khachikyan, Eh.E.; Ehjnatyan, D.A.

    1975-01-01

    Given in the paper are the results of colorimetry of two diffuse nebulae: NGC 6914b and Parsamian 22. Use was made of pictures obtained on the one-meter Schmidt telescope of the Byurakan Observatory. The surface brightness of certain regions of the nebulae and their colors (U-B) and (B-V) have been determined. Although these nebulae are seen in the same sky region, they differ sharply in color: NGC 6914b is intensely blue, while Parsamian 22 is intensely red

  5. Central Stars of Mid-Infrared Nebulae Discovered with Spitzer and WISE

    Gvaramadze, V. V.; Kniazev, A. Y.

    2017-02-01

    Searches for compact mid-IR nebulae with the Spitzer Space Telescope and the Wide-field Infrared Survey Explorer (WISE), accompanied by spectroscopic observations of central stars of these nebulae led to the discovery of many dozens of massive stars at different evolutionary stages, of which the most numerous are candidate luminous blue variables (LBVs). In this paper, we give a census of candidate and confirmed Galactic LBVs revealed with Spitzer and WISE, and present some new results of spectroscopic observations of central stars of mid-IR nebulae.

  6. V900 MON AND THOMMES' NEBULA: A NEW FUor IN MONOCEROS

    Reipurth, Bo; Aspin, Colin [Institute for Astronomy, University of Hawaii at Manoa, 640 N. Aohoku Place, Hilo, HI 96720 (United States); Herbig, G. H., E-mail: herbig@ifa.hawaii.edu [Institute for Astronomy, University of Hawaii at Manoa, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2012-03-20

    Detailed observations of a recently recognized eruptive variable, V900 Mon, are presented. The star is located in the small cloud L1656, a little-studied region of modest star formation activity in Monoceros, and is presently at a magnitude of r {approx} 16, surrounded by a bright compact reflection nebula, where only a 20th magnitude star was seen on the red first-epoch POSS plate. Optical spectra show a red absorption-line spectrum not later than mid-K, and the H{alpha} line and the Na I D{sub 12} doublet display prominent P Cygni profiles with massive absorption troughs indicating a cool outflowing wind. Near-infrared spectra show deep CO bandhead absorption and pronounced molecular bands of water vapor indicative of a much cooler object. This spectral appearance is very similar to that of FU Orionis, except that V900 Mon has a much higher reddening of A{sub V} {approx} 13 mag. The energy distribution of V900 Mon, compiled from non-simultaneous observations and thus dependent on possible luminosity changes, shows that V900 Mon is a Class I protostar with a massive cool envelope. At a distance of about 1100 pc, V900 Mon has a luminosity of 106 L{sub Sun} in the range of 0.55-160 {mu}m. These data identify V900 Mon as a new member of the rare class of FU Orionis variables.

  7. Multifrequency observations of the region associated with the cometary nebulae GM24

    Tapia, M; Roth, M; Rodriguez, L F; Canto, J; Persi, P; Ferrari-Toniolo, M; Lopez, J A

    1985-12-01

    The faint nebulosity GM24 = PP85 was observed at infrared (1-20 ..mu..m) and radio (6-cm and CO line) wavelengths in the vicinity of a CO ''hot spot'' reported previously. Radio continuum (6-cm) emission from an H II region was detected with the Very Large Array. Its position coincides with a 1-4 ..mu..m emission peak. CM24 appears to be the visible part of an obscured H II region that is beginning to emerge from the molecular cloud. Our infrared maps made at the Observatorio Astronomico Nacional at San Pedro Martir, show two additional (1-20 ..mu..m) peaks located at distances approx. 30 arcsec from the compact H II region, all surrounded by extended near-infrared (1-4 ..mu..m) emission. A detailed CO (J = 1 ..-->.. 0) map of the whole molecular cloud was obtained with the University of Texas Milimeter Wave Telescope. High resolution spectroscopy of the H..cap alpha.. line was also obtained with the Anglo-Australian Telescope. Our results are interpreted in terms of recent formation of three massive stars; one of which, having developed an H II region, is at a slightly later phase of its evolution. The extended near-infrared emission may arise in a reflection nebula similar to NGC 7538-Irs 9.

  8. Multifrequency observations of the region associated with the cometary nebulae GM24

    Tapia, M.; Roth, M.; Rodriguez, L.F.; Canto, J.; Persi, P.; Ferrari-Toniolo, M.; Lopez, J.A.

    1985-01-01

    The faint nebulosity GM24 = PP85 was observed at infrared (1-20 μm) and radio (6-cm and CO line) wavelengths in the vicinity of a CO ''hot spot'' reported previously. Radio continuum (6-cm) emission from an H II region was detected with the Very Large Array. Its position coincides with a 1-4 μm emission peak. CM24 appears to be the visible part of an obscured H II region that is beginning to emerge from the molecular cloud. Our infrared maps made at the Observatorio Astronomico Nacional at San Pedro Martir, show to additional (1-20 μm) peaks located at distances approx. 30 arcsec from the compact H II region, all surrounded by extended near-infrared (1-4 μm) emission. A detailed CO (J = 1 → 0) map of the whole molecular cloud was obtained with the University of Texas Milimeter Wave Telescope. High resolution spectroscopy of the Hα line was also obtained with the Anglo-Australian Telescope. Our results are interpreted in terms of recent formation of three massive stars; one of which, having developed an H II region, is at a slightly later phase of its evolution. The extended near-infrared emission may arise in a reflection nebula similar to NGC 7538-Irs 9. (author)

  9. Pre-accretional sorting of grains in the outer solar nebula

    Wozniakiewicz, P. J.; Bradley, J. P.; Ishii, H. A.; Price, M. C.; Brownlee, D. E.

    2013-01-01

    Despite their micrometer-scale dimensions and nanogram masses, chondritic porous interplanetary dust particles (CP IDPs) are an important class of extraterrestrial material since their properties are consistent with a cometary origin and they show no evidence of significant post-accretional parent body alteration. Consequently, they can provide information about grain accretion in the comet-forming region of the outer solar nebula. We have previously reported our comparative study of the sizes and size distributions of crystalline silicate and sulfide grains in CP IDPs, in which we found these components exhibit a size-density relationship consistent with having been sorted together prior to accretion. Here we extend our data set and include GEMS (glass with embedded metal and sulfide), the most abundant amorphous silicate phase observed in CP IDPs. We find that while the silicate and sulfide sorting trend previously observed is maintained, the GEMS size data do not exhibit any clear relationship to these crystalline components. Therefore, GEMS do not appear to have been sorted with the silicate and sulfide crystals. The disparate sorting trends observed in GEMS and the crystalline grains in CP IDPs present an interesting challenge for modeling early transport and accretion processes. They may indicate that several sorting mechanisms operated on these CP IDP components, or alternatively, they may simply be a reflection of different source environments.

  10. Ionization structure of planetary nebulae. 4. NGC 6853

    Barker, T.

    1983-01-01

    Spectrophotometric observations of emission line intensities were made in seven positions in the planetary nebula NGC 6853. For five of the positions, coverage is across the entire spectral range 1400A to 9600A. Standard equations used to correct for the existence of elements in other than the optically-observable ionization stages give results over a wide range of ionization that are generally consistent and in agreement with abundances calculated using ultraviolet lines. As in the previous studies in this series, the lambda 4267 CII line implies a c(2+) abundance that is higher than that determined from UV lines. Although this effect is much smaller than in NGC 6720 and NGC 7009, it is again largest nearest the central star, giving more evidence that the excitation mechanism for the lambda 4267 line is not understood

  11. An earlier explosion date for the Crab Nebula supernova

    Abt, Helmut A.; Fountain, John W.

    2018-04-01

    The Chinese first reported the Crab Nebula supernova on 1054 July 5. Ecclesiastical documents from the near east reported it in April and May of 1054. More than 33 petroglyphs made by Native Americans in the US and Mexico are consistent with sightings both before and after conjunction with the Sun on 1054 May 27. We found a petroglyph showing the new star close to Venus and the Moon, which occurred on 1054 April 12 and April 13, respectively. Collins et al., using the four historical dates, derived a light curve that is like that of a Type Ia supernova. The only remaining problem with this identification is that this supernova was near maximum light for 85 d, which is unlike the behavior of any known supernova.

  12. Volatile inventories in clathrate hydrates formed in the primordial nebula.

    Mousis, Olivier; Lunine, Jonathan I; Picaud, Sylvain; Cordier, Daniel

    2010-01-01

    The examination of ambient thermodynamic conditions suggests that clathrate hydrates could exist in the Martian permafrost, on the surface and in the interior of Titan, as well as in other icy satellites. Clathrate hydrates are probably formed in a significant fraction of planetesimals in the solar system. Thus, these crystalline solids may have been accreted in comets, in the forming giant planets and in their surrounding satellite systems. In this work, we use a statistical thermodynamic model to investigate the composition of clathrate hydrates that may have formed in the primordial nebula. In our approach, we consider the formation sequence of the different ices occurring during the cooling of the nebula, a reasonable idealization of the process by which volatiles are trapped in planetesimals. We then determine the fractional occupancies of guests in each clathrate hydrate formed at a given temperature. The major ingredient of our model is the description of the guest-clathrate hydrate interaction by a spherically averaged Kihara potential with a nominal set of parameters, most of which are fitted to experimental equilibrium data. Our model allows us to find that Kr, Ar and N2 can be efficiently encaged in clathrate hydrates formed at temperatures higher than approximately 48.5 K in the primitive nebula, instead of forming pure condensates below 30 K. However, we find at the same time that the determination of the relative abundances of guest species incorporated in these clathrate hydrates strongly depends on the choice of the parameters of the Kihara potential and also on the adopted size of cages. Indeed, by testing different potential parameters, we have noted that even minor dispersions between the different existing sets can lead to non-negligible variations in the determination of the volatiles trapped in clathrate hydrates formed in the primordial nebula. However, these variations are not found to be strong enough to reverse the relative abundances

  13. Two-dimensional spectrophotometry of planetary nebulae by CCD imaging

    Jacoby, G.H.; Africano, J.L.; Quigley, R.J.; Western Washington Univ., Bellingham, WA)

    1987-01-01

    The spatial distribution of the electron temperature and density and the ionic abundances of O(+), O(2+), N(+), and S(+) have been derived from CCD images of the planetary nebulae NGC 40 and NGC 6826 taken in the important emission lines of forbidden O II, forbidden O III, H-beta, forbidden N II, and forbidden S II. The steps required in the derivation of the absolute fluxes, line, ratios, and ionic abundances are outlined and then discussed in greater detail. The results show that the CCD imaging technique for two-dimensional spectrophotometry can effectively compete with classical spectrophotometry, providing the added benefits of complete spatial coverage at seeing-disk spatial resolution. The multiplexing in the spatial dimension, however, results in a loss of spectral information, since only one emission line is observed at any one time. 37 references

  14. The ultraviolet extinction properties of the 30 Dor Nebula

    De Marchi, Guido; Panagia, Nino

    2018-01-01

    Recent investigation of the extinction law in 30 Dor and the Tarantula Nebula, at optical and near infrared wavelengths, has revealed a ratio of total to selective extinction RV=AV/E(B-V) of about 4.5. This indicates a larger proportion of large grains than in the Galactic diffuse interstellar medium. Possible origins include coalescence of small grains, grain growth, selective destruction of small grains, and fresh injection of large grains. From a study of the ultraviolet extinction properties of three Wolf-Rayet stars in 30 Dor (R 139, R 140, R 145), observed with the International Ultraviolet Explorer, we show that the excess of large grains does not come at the expense of small grains, which are still present. Fresh injection of large grains by supernova explosions appears to be the dominant mechanism.

  15. Discovery of new planetary nebulae in the Small Magellanic Cloud

    Drašković, D.; Reid, W. A.; Parker, Q. A.; Stupar, M.

    2016-01-01

    We present six new planetary nebulae (PNe) discovered in the Small Magellanic Cloud (SMC) from deep UK Schmidt telescope (UKST) narrow band Ha and broad-band short- red “SR” continuum images and confirmed spectroscopically. These 6 preliminary discoveries provide a 6% increase to the previously known SMC PN population of ∼⃒100. Once spectroscopic follow-up of all our newly identified candidates is complete, we expect to increase the total number of known SMC PNe by up to 50%. This will permit a significant improvement to determination of the SMC PN luminosity function (PNLF) and enable further insights into the chemical evolution and kinematics of the SMC PN population. (paper)

  16. The Σ − D relation for planetary nebulae: Preliminary analysis

    Urošević D.

    2007-01-01

    Full Text Available An analysis of the relation between radio surface brightness and diameter, so-called Σ − D relation, for planetary nebulae (PNe is presented: i the theoretical Σ − D relation for the evolution of bremsstrahlung surface brightness is derived; ii contrary to the results obtained earlier for the Galactic supernova remnant (SNR samples, our results show that the updated sample of Galactic PNe does not severely suffer from volume selection effect - Malmquist bias (same as for the extragalactic SNR samples and; iii we conclude that the empirical S − D relation for PNe derived in this paper is not useful for valid determination of distances for all observed PNe with unknown distances. .

  17. The radial velocities of planetary nebulae in NGC 3379

    Ciardullo, Robin; Jacoby, George H.; Dejonghe, Herwig B.

    1993-09-01

    We present the results of a radial velocity survey of planetary nebulae (PNs) in the normal elliptical galaxy NGC 3379 performed with the Kitt Peak 4 m telescope and the NESSIE multifiber spectrograph. In two half-nights, we measured 29 PNs with projected galactocentric distances between 0.4 and 3.8 effective radii with an observational uncertainty of about 7 km/s. These data extend three times farther into the halo than any previous absorption-line velocity study. The velocity dispersion and photometric profile of the galaxy agrees extremely well with that expected from a constant mass-to-light ratio, isotropic orbit Jaffe model with M/L(B) about 7; the best-fitting anisotropic models from a quadratic programming algorithm also give M/L(B) about 7. The data are consistent with models that contain no dark matter within 3.5 effective radii of the galaxy's nucleus.

  18. Herbig-Haro objects and T Tauri nebulae

    Boehm, K.H.

    1975-01-01

    The empirical information about Herbig-Haro objects and T Tauri nebulae is summarized. We emphasize especially the importance of the spectroscopic and spectrophotometric data. Relative and (preliminary) absolute emission line fluxes are presented and discussed. We consider the radial velocity data and the detection of a faint blue continuum in Herbig-Haro objects as important from a theoretical point of view. The direct interpretation of the emission line spectra is simple and leads to values of the electron temperature, electron density, density inhomogeneities, filling factors, degree of ionization and chemical abundances. The relevant procedures are discussed in some detail. The possible role of the Herbig-Haro objects in the early phases of stellar evolution is discussed. (orig./BJ) [de

  19. Synthesis of Organics in the Early Solar Nebula

    Johnson, Natasha M.; Manning, S.; Nuth, J. A., III

    2007-10-01

    It is unknown what process or processes made the organics that are found or detected in extraterrestrial materials. One process that forms organics are Fischer-Tropsch type (FTT) reactions. Fischer-Tropsch type synthesis produces complex hydrocarbons by hydrogenating carbon monoxide via surface mediated reactions. The products of these reactions have been well-studied using `natural’ catalysts [1] and calculations of the efficiency of FTT synthesis in the Solar Nebula suggest that these types of reactions could make significant contributions to material near three AU [2]. We use FTT synthesis to coat Fe-silicate amorphous grains with organic material to simulate the chemistry in the early Solar Nebula. These coatings are composed of macromolecular organic phases [3]. Previous work also showed that as the grains became coated, Haber-Bosch type reactions took place resulting in nitrogen-bearing organics [4]. Our experiments consist of circulating CO, N2, and H2 gas through Fe- amorphous silicate grains that are maintained at a specific temperature in a closed system. The gases are passed through an FTIR spectrometer and are measured to monitor the reaction progress. Samples are analyzed using FTIR, and GCMS (including pyrolysis) and extraction techniques are used to analyze the organic coatings. These experiments show that these types of reactions are an effective means to produce complex hydrocarbons. We present the analysis of the produced organics (solid and gas phase) and the change in the production rate of several compounds as the grains become coated. Organics generated by this technique could represent the carbonaceous material incorporated in comets and meteorites. References: [1] Hayatsu and Anders 1981. Topics in Current Chemistry 99:1-37. [2] Kress and Tielens 2001. MAPS 36:75-91. [3] Johnson et al. 2004. #1876. 35th LPSC. [4] Hill and Nuth 2003. Astrobiology 3:291-304. This work was supported by a grant from NASA.

  20. Hot Gas in the Wolf–Rayet Nebula NGC 3199

    Toalá, J. A.; Chu, Y.-H. [Institute of Astronomy and Astrophysics, Academia Sinica (ASIAA), Taipei 10617, Taiwan (China); Marston, A. P. [European Space Agency/STScI, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Guerrero, M. A. [Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, Granada E-18008 (Spain); Gruendl, R. A. [Department of Astronomy, University of Illinois, 1002 West Green Street, Urbana, IL 61801 (United States)

    2017-09-01

    The Wolf–Rayet (WR) nebula NGC 3199 has been suggested to be a bow shock around its central star, WR 18, which is presumably a runaway star, because optical images of the nebula show a dominating arc of emission southwest of the star. We present the XMM-Newton detection of extended X-ray emission from NGC 3199, unveiling the powerful effect of the fast wind from WR 18. The X-ray emission is brighter in the region southeast of the star and an analysis of the spectral properties of the X-ray emission reveals abundance variations: (i) regions close to the optical arc present nitrogen-rich gas enhanced by the stellar wind from WR 18 and (ii) gas at the eastern region exhibits abundances close to those reported for the nebular abundances derived from optical studies, which is a signature of an efficient mixing of the nebular material with the stellar wind. The dominant plasma temperature and electron density are estimated to be T ≈ 1.2 × 10{sup 6} K and n {sub e} = 0.3 cm{sup −3} with an X-ray luminosity in the 0.3–3.0 keV energy range of L {sub X} = 2.6 × 10{sup 34} erg s{sup −1}. Combined with information derived from Herschel and the recent Gaia first data release, we conclude that WR 18 is not a runaway star and that the formation, chemical variations, and the shape of NGC 3199 depend on the initial configuration of the interstellar medium.

  1. New View of Gas and Dust in the Solar Nebula

    Taylor, G. J.

    2010-08-01

    The recognizable components in meteorites differ in their relative abundances of the three oxygen isotopes (16O, 17O, and 18O). In particular, the amount of 16O varies from being like that of the Earth to substantially enriched compared to the other two isotopes. The current explanation for this interesting range in isotopic composition is that dust and gas in the solar nebula (the cloud of gas and dust surrounding the primitive Sun) began with the same 16O-rich composition, but the solids evolved towards the terrestrial value. A new analysis of the problem by Alexander Krot (University of Hawaii) and colleagues at the University of Hawaii, the University of Chicago, Clemson University, and Lawrence Livermore National Laboratory leads to the bold assertion that primordial dust and gas differed in isotopic composition. The gas was rich in 16O as previously thought (possibly slightly richer in 16O than the measurements of the solar wind returned by the Genesis Mission), but that the dust had a composition close to the 16O-depleted terrestrial average. In this new view, the dust had a different history than did the gas before being incorporated into the Solar System. Solids with compositions near the terrestrial line may have formed in regions of the solar nebula where dust had concentrated compared to the mean solar dust/gas ratio (1 : ~100). The idea has great implications for understanding the oxygen-isotope composition of the inner Solar System and the origin of materials in the molecular cloud from which the Solar System formed.

  2. Reflectance Modeling

    Smith, J. A.; Cooper, K.; Randolph, M.

    1984-01-01

    A classical description of the one dimensional radiative transfer treatment of vegetation canopies was completed and the results were tested against measured prairie (blue grama) and agricultural canopies (soybean). Phase functions are calculated in terms of directly measurable biophysical characteristics of the canopy medium. While the phase functions tend to exhibit backscattering anisotropy, their exact behavior is somewhat more complex and wavelength dependent. A Monte Carlo model was developed that treats soil surfaces with large periodic variations in three dimensions. A photon-ray tracing technology is used. Currently, the rough soil surface is described by analytic functions and appropriate geometric calculations performed. A bidirectional reflectance distribution function is calculated and, hence, available for other atmospheric or canopy reflectance models as a lower boundary condition. This technique is used together with an adding model to calculate several cases where Lambertian leaves possessing anisotropic leaf angle distributions yield non-Lambertian reflectance; similar behavior is exhibited for simulated soil surfaces.

  3. An Analysis of Spectra in the Red Rectangle Nebula Frédéric Zagury

    If the preceding paper emphasized the importance of atmospheric extinction for our understanding of ...... paper, the authors address several problems which concern the star system at the center of the nebula ... 1981), on-going research being ...

  4. Resonance-enhanced two-photon ionization of ions by Lyman alpha radiation in gaseous nebulae.

    Johansson, S; Letokhov, V

    2001-01-26

    One of the mysteries of nebulae in the vicinity of bright stars is the appearance of bright emission spectral lines of ions, which imply fairly high excitation temperatures. We suggest that an ion formation mechanism, based on resonance-enhanced two-photon ionization (RETPI) by intense H Lyman alpha radiation (wavelength of 1215 angstroms) trapped inside optically thick nebulae, can produce these spectral lines. The rate of such an ionization process is high enough for rarefied gaseous media where the recombination rate of the ions formed can be 10(-6) to 10(-8) per second for an electron density of 10(3) to 10(5) per cubic centimeter in the nebula. Under such conditions, the photo-ions formed may subsequently undergo further RETPI, catalyzed by intense He i and He ii radiation, which also gets enhanced in optically thick nebulae that contain enough helium.

  5. Gas capture and rare gas retention by accreting planets in the solar nebula

    Mizuno, H.; Nakazawa, K.; Hayashi, C.

    1982-01-01

    In this paper, the physico-chemical effects of the nebula gas on the planets are reviewed from a standpoint of planetary formation in the solar nebula. The proto-Earth growing in the nebula was surrounded by a primordial atmosphere with a solar chemical composition and solar isotopic composition. When the mass of the proto-Earth was greater than 0.3 times the present Earth mass, the surface was molten because of the blanketing effect of the atmosphere. Therefore, the primordial rare gases contained in the primordial atmosphere dissolved into the molten Earth material without fractionation and in particular the dissolved neon is expected to be conserved in the present Earth material. Hence, if dissolved neon with a solar isotopic ratio is discovered in the Earth material, it will indicate that the Earth was formed in the nebula and that the dissolved rare gases were one of the sources which degassed to form the present atmosphere. (author)

  6. Colorimetry of the diffuse nebulas S 156, S 157A, S 158, and NGC 7635

    Parsamian, E.S.; Petrosian, V.M.

    1984-01-01

    The results of a colorimetric investigation of the diffuse nebulas S 156, S 157A, S 158, and NGC 7635, which are excited by O stars, are presented. The nebulas S 156, S 157A, and NGC 7635 are very bright in U due to the presence in them of strong ultraviolet doublet forbidden O II 3727 A. These values correspond effectively to the monochromatic image of the nebulas at this wavelength. The measurements show that the B-V color index does not change significantly with distance from the star except for S 158, where a weak dependence is observed. The results indicate that the physical properties of these nebulas differ little. It is concluded that the gas masses in this association are remnants of star formation that have a common origin with the stars. The age of the association is estimated at 100,000-1,000,000 yr. 13 references

  7. Reflective optics

    Korsch, Dietrich

    1991-01-01

    This is the first book dedicated exclusively to all-reflective imaging systems. It is a teaching tool as well as a practical design tool for anyone who specializes in optics, particularly for those interested in telescopes, infrared, and grazing-incidence systems. The first part of the book describes a unified geometric optical theory of all-reflective imaging systems (from near-normal to grazing incidence) developed from basic principles. The second part discusses correction methods and a multitude of closed-form solutions of well-corrected systems, supplemented with many conventional and unc

  8. ABOUT TEMPERATURE FIELDS AND CONDITIONS OF GASEOUS CONDENSATION OF NEBULAES IN THE PLANETARY VORTEX

    L. V. Klyuchinskaya

    2014-01-01

    Full Text Available New exact solution of the spherically-axissymmetric Eiler's equations, called as plan­etary vortex, is applied to the problem of formation in planetary nebula germs of planets due to the condensation of gases in the areas of vortex instability which calls the rings of planetary vortex. It is shown that the vortex perturbations causes changes in preassure and temperature at which the gases of nebula condense themselves, forming the germs of the planets.

  9. Spatio-kinematic modelling: Testing the link between planetary nebulae and close binaries

    Jones, David; Tyndall, Amy A.; Huckvale, Leo; Prouse, Barnabas; Lloyd, Myfanwy

    2011-01-01

    It is widely believed that central star binarity plays an important role in the formation and evolution of aspherical planetary nebulae, however observational support for this hypothesis is lacking. Here, we present the most recent results of a continuing programme to model the morphologies of all planetary nebulae known to host a close binary central star. Initially, this programme allows us to compare the inclination of the nebular symmetry axis to that of the binary plane, testing the theo...

  10. ALMA OBSERVATIONS OF THE COLDEST PLACE IN THE UNIVERSE: THE BOOMERANG NEBULA

    Sahai, R.; Vlemmings, W. H. T.; Huggins, P. J.; Nyman, L.-Å.; Gonidakis, I.

    2013-01-01

    The Boomerang Nebula is the coldest known object in the universe, and an extreme member of the class of pre-planetary nebulae, objects which represent a short-lived transitional phase between the asymptotic giant branch and planetary nebula evolutionary stages. Previous single-dish CO (J = 1-0) observations (with a 45'' beam) showed that the high-speed outflow in this object has cooled to a temperature significantly below the temperature of the cosmic background radiation. Here we report the first observations of the Boomerang Nebula with ALMA in the CO J = 2-1 and J = 1-0 lines to resolve the structure of this ultra-cold nebula. We find a central hourglass-shaped nebula surrounded by a patchy, but roughly round, cold high-velocity outflow. We compare the ALMA data with visible-light images obtained with the Hubble Space Telescope and confirm that the limb-brightened bipolar lobes seen in these data represent hollow cavities with dense walls of molecular gas and dust producing both the molecular-emission-line and scattered-light structures seen at millimeter and visible wavelengths. The large diffuse biconical shape of the nebula seen in the visible wavelength range is likely due to preferential illumination of the cold, high-velocity outflow. We find a compact source of millimeter-wave continuum in the nebular waist—these data, together with sensitive upper limits on the radio continuum using observations with ATCA, indicate the presence of a substantial mass of very large (millimeter-sized) grains in the waist of the nebula. Another unanticipated result is the detection of CO emission regions beyond the ultra-cold region which indicate the re-warming of the cold gas, most likely due to photoelectric grain heating

  11. ALMA Observations of the Coldest Place in the Universe: The Boomerang Nebula

    Sahai, R.; Vlemmings, W. H. T.; Huggins, P. J.; Nyman, L.-Å.; Gonidakis, I.

    2013-11-01

    The Boomerang Nebula is the coldest known object in the universe, and an extreme member of the class of pre-planetary nebulae, objects which represent a short-lived transitional phase between the asymptotic giant branch and planetary nebula evolutionary stages. Previous single-dish CO (J = 1-0) observations (with a 45'' beam) showed that the high-speed outflow in this object has cooled to a temperature significantly below the temperature of the cosmic background radiation. Here we report the first observations of the Boomerang Nebula with ALMA in the CO J = 2-1 and J = 1-0 lines to resolve the structure of this ultra-cold nebula. We find a central hourglass-shaped nebula surrounded by a patchy, but roughly round, cold high-velocity outflow. We compare the ALMA data with visible-light images obtained with the Hubble Space Telescope and confirm that the limb-brightened bipolar lobes seen in these data represent hollow cavities with dense walls of molecular gas and dust producing both the molecular-emission-line and scattered-light structures seen at millimeter and visible wavelengths. The large diffuse biconical shape of the nebula seen in the visible wavelength range is likely due to preferential illumination of the cold, high-velocity outflow. We find a compact source of millimeter-wave continuum in the nebular waist—these data, together with sensitive upper limits on the radio continuum using observations with ATCA, indicate the presence of a substantial mass of very large (millimeter-sized) grains in the waist of the nebula. Another unanticipated result is the detection of CO emission regions beyond the ultra-cold region which indicate the re-warming of the cold gas, most likely due to photoelectric grain heating.

  12. ALMA OBSERVATIONS OF THE COLDEST PLACE IN THE UNIVERSE: THE BOOMERANG NEBULA

    Sahai, R. [Jet Propulsion Laboratory, MS 183-900, California Institute of Technology, Pasadena, CA 91109 (United States); Vlemmings, W. H. T. [Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-43992 Onsala (Sweden); Huggins, P. J. [Physics Department, New York University, 4 Washington Place, New York, NY 10003 (United States); Nyman, L.-Å. [Joint ALMA Observatory (JAO), Alonso de Cordova 3107, Vitacura, Santiago de Chile (Chile); Gonidakis, I., E-mail: raghvendra.sahai@jpl.nasa.gov [CSIRO Astronomy and Space Science, Australia Telescope National Facility, Marsfield NSW 2122 (Australia)

    2013-11-10

    The Boomerang Nebula is the coldest known object in the universe, and an extreme member of the class of pre-planetary nebulae, objects which represent a short-lived transitional phase between the asymptotic giant branch and planetary nebula evolutionary stages. Previous single-dish CO (J = 1-0) observations (with a 45'' beam) showed that the high-speed outflow in this object has cooled to a temperature significantly below the temperature of the cosmic background radiation. Here we report the first observations of the Boomerang Nebula with ALMA in the CO J = 2-1 and J = 1-0 lines to resolve the structure of this ultra-cold nebula. We find a central hourglass-shaped nebula surrounded by a patchy, but roughly round, cold high-velocity outflow. We compare the ALMA data with visible-light images obtained with the Hubble Space Telescope and confirm that the limb-brightened bipolar lobes seen in these data represent hollow cavities with dense walls of molecular gas and dust producing both the molecular-emission-line and scattered-light structures seen at millimeter and visible wavelengths. The large diffuse biconical shape of the nebula seen in the visible wavelength range is likely due to preferential illumination of the cold, high-velocity outflow. We find a compact source of millimeter-wave continuum in the nebular waist—these data, together with sensitive upper limits on the radio continuum using observations with ATCA, indicate the presence of a substantial mass of very large (millimeter-sized) grains in the waist of the nebula. Another unanticipated result is the detection of CO emission regions beyond the ultra-cold region which indicate the re-warming of the cold gas, most likely due to photoelectric grain heating.

  13. The distribution of mass in the planetary system and solar nebulae

    Weidenschilling, S.J.

    1977-01-01

    A model 'solar nebula' is constructed by adding the solar complement of light elements to each planet, using recent models of planetary compositions. Uncertainties in this approach are estimated. The computed surface density varies approximately as rsup(-3/2). Mercury, Mars and the asteroid belt are anomalously low in mass, but processes exist which would preferentially remove matter from these regions. Planetary masses and compositions are generally consistent with a monotonic density distribution in the primordial solar nebula. (Auth.)

  14. CRL 2688: A post-carbon-star object and probable planetary nebula progenitor

    Zuckerman, B.; Gilra, D.P.; Turner, B.E.; Morris, M.; Palmer, P.

    1976-01-01

    Millimeter-wavelength emission is observed toward CRL 2688 from H 12 CN, H 13 CN, CS, and HC 3 N. The similarity of this emission and that from the molecular envelope of the carbon star IRC+10216 establishes, beyond a reasonable doubt, that CRL 2688 is a post--carbon-star object. It appears probable that both of these objects will evolve into planetary nebulae. An evolutionary sequence leading from carbon stars to planetary nebulae is outlined

  15. The mysterious age invariance of the planetary nebula luminosity function bright cut-off

    Gesicki, K.; Zijlstra, A. A.; Miller Bertolami, M. M.

    2018-05-01

    Planetary nebulae mark the end of the active life of 90% of all stars. They trace the transition from a red giant to a degenerate white dwarf. Stellar models1,2 predicted that only stars above approximately twice the solar mass could form a bright nebula. But the ubiquitous presence of bright planetary nebulae in old stellar populations, such as elliptical galaxies, contradicts this: such high-mass stars are not present in old systems. The planetary nebula luminosity function, and especially its bright cut-off, is almost invariant between young spiral galaxies, with high-mass stars, and old elliptical galaxies, with only low-mass stars. Here, we show that new evolutionary tracks of low-mass stars are capable of explaining in a simple manner this decades-old mystery. The agreement between the observed luminosity function and computed stellar evolution validates the latest theoretical modelling. With these models, the planetary nebula luminosity function provides a powerful diagnostic to derive star formation histories of intermediate-age stars. The new models predict that the Sun at the end of its life will also form a planetary nebula, but it will be faint.

  16. Polarization due to dust scattering in the planetary nebula Cn1-1

    Bhatt, H.C.

    1989-01-01

    The peculiar emission-line object Cn1-1 (=HDE330036=PK330+4 degrees 1), classified both as a symbiotic star and as a planetary nebula, was detected by the Infrared Astronomical Satellite (IRAS) as a strong source of far-infrared dust in the system. Bhatt and Mallik (1986) discussed the nature of the dust in Cn1-1 and argued that the object is a Type I protoplanetary nebula in a binary system. The argument presented here is that the polarization is intrinsic to Cn1-1 and is due to scattering by large (compared to interstellar) dust grains in the protoplanetary nebula that are asymmetrically distributed around the central star. The large degree of polarization (approximately 3 percent for the Cn1-1 distance of approximately 450 pc) with a large lambda(sub max) is naturally explained if it is caused by scattering by large dust grains in the Cn1-1 nebula. Since the H(sub alpha) line is also polarized at the same level and position angle as the continuum, the dust must be asymmetrically distributed around the central star. The morphology of the protoplanetary nebula in Cn1-1 may be bipolar. Thus, the polarization observations support the suggestion that Cn1-1 is a bipolar Type I planetary nebula

  17. Observations of the planetary nebula RWT 152 with OSIRIS/GTC

    Aller, A.; Miranda, L. F.; Olguín, L.; Solano, E.; Ulla, A.

    2016-11-01

    RWT 152 is one of the few known planetary nebulae with an sdO central star. We present subarcsecond red tunable filter Hα imaging and intermediate-resolution, long-slit spectroscopy of RWT 152 obtained with OSIRIS/GTC (Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy/Gran Telescopio Canarias) with the goal of analysing its properties. The Hα image reveals a bipolar nebula with a bright equatorial region and multiple bubbles in the main lobes. A faint circular halo surrounds the main nebula. The nebular spectra reveal a very low excitation nebula with weak emission lines from H+, He+ and double-ionized metals, and absence of emission lines from neutral and single-ionized metals, except for an extremely faint [N II] λ6584 emission line. These spectra may be explained if RWT 152 is a density-bounded planetary nebula. Low nebular chemical abundances of S, O, Ar, N and Ne are obtained in RWT 152, which, together with the derived high peculiar velocity (˜ 92-131 km s-1), indicate that this object is a halo planetary nebula. The available data are consistent with RWT 152 evolving from a low-mass progenitor (˜1 M⊙) formed in a metal-poor environment.

  18. A ROTATIONALLY POWERED MAGNETAR NEBULA AROUND SWIFT J1834.9–0846

    Torres, Diego F. [Institute of Space Sciences (IEEC-CSIC), Campus UAB, Carrer de Magrans s/n, E-08193 Barcelona (Spain)

    2017-01-20

    A wind nebula generating extended X-ray emission was recently detected surrounding Swift J1834.9–0846. This is the first magnetar for which such a wind nebula was found. Here, we investigate whether there is a plausible scenario where the pulsar wind nebula (PWN) can be sustained without the need of advocating for additional sources of energy other than rotational. We do this by using a detailed radiative and dynamical code that studies the evolution of the nebula and its particle population in time. We find that such a scenario indeed exists: Swift J1834.9–0846's nebula can be explained as being rotationally powered, as all other known PWNe are, if it is currently being compressed by the environment. The latter introduces several effects, the most important of which is the appearance of adiabatic heating, being increasingly dominant over the escape of particles as reverberation goes by. The need of reverberation naturally explains why this is the only magnetar nebula detected and provides estimates for Swift 1834.9–0846's age.

  19. Discovery of a Circumstellar Disk in the Lagoon Nebula

    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

  20. Reflective Efficacy

    Carla Bagnoli

    2018-04-01

    Full Text Available The purpose of this paper is to highlight some difficulties of Neil Sinhababu’s Humean theory of agency, which depend on his radically reductivist approach, rather than to his Humean sympathies. The argument is that Sinhababu’s theory builds upon a critique of reflective agency which is based on equivocation and misunderstandings of the Kantian approach. Ultimately, the objection is that his reductivist view is unequipped to address the rclassical problems of rational deliberation and agential authority.

  1. Turbulent Concentration of mm-Size Particles in the Protoplanetary Nebula: Scale-Dependent Cascades

    Cuzzi, J. N.; Hartlep, T.

    2015-01-01

    The initial accretion of primitive bodies (here, asteroids in particular) from freely-floating nebula particles remains problematic. Traditional growth-by-sticking models encounter a formidable "meter-size barrier" (or even a mm-to-cm-size barrier) in turbulent nebulae, making the preconditions for so-called "streaming instabilities" difficult to achieve even for so-called "lucky" particles. Even if growth by sticking could somehow breach the meter size barrier, turbulent nebulae present further obstacles through the 1-10km size range. On the other hand, nonturbulent nebulae form large asteroids too quickly to explain long spreads in formation times, or the dearth of melted asteroids. Theoretical understanding of nebula turbulence is itself in flux; recent models of MRI (magnetically-driven) turbulence favor low-or- no-turbulence environments, but purely hydrodynamic turbulence is making a comeback, with two recently discovered mechanisms generating robust turbulence which do not rely on magnetic fields at all. An important clue regarding planetesimal formation is an apparent 100km diameter peak in the pre-depletion, pre-erosion mass distribution of asteroids; scenarios leading directly from independent nebula particulates to large objects of this size, which avoid the problematic m-km size range, could be called "leapfrog" scenarios. The leapfrog scenario we have studied in detail involves formation of dense clumps of aerodynamically selected, typically mm-size particles in turbulence, which can under certain conditions shrink inexorably on 100-1000 orbit timescales and form 10-100km diameter sandpile planetesimals. There is evidence that at least the ordinary chondrite parent bodies were initially composed entirely of a homogeneous mix of such particles. Thus, while they are arcane, turbulent concentration models acting directly on chondrule size particles are worthy of deeper study. The typical sizes of planetesimals and the rate of their formation can be

  2. G25.5 + 0.2: a very young supernova remnant or a galactic planetary nebula?

    White, R.L.; Becker, R.H.

    1990-01-01

    G25.5 + 0.2, a radio source suggested by previous authors to be a very young galactic supernova remnant, is more likely to be a planetary nebula. Its IRAS colours and fluxes and its radio spectrum and morphology are all consistent with the properties of planetary nebulae; its radio flux and distance imply a large mass of ionized gas, which is expected from a Type I planetary nebula lying in the galactic plane. We suggest some definitive observations which should be able to determine whether this interesting object is a planetary nebula or a supernova remnant. (author)

  3. On Reflection

    Blasco, Maribel

    2012-01-01

    produces: that the self is accessible and transcendable, that reflexivity is universal across space and time, and that the self can act as its own remedial change agent or ‘inner consultant.’ I argue that because reflexivity is understood in many different ways, attention to definition is crucial, both...... on the concepts of selfhood that prevail and how notions of difference are constructed. First, I discuss how the dominant usages of reflexivity in intercultural education reflect and reproduce a Cartesian view of the self that shapes how ICC is conceptualized and taught. I discuss three assumptions that this view...

  4. Inspiring Reflections

    Muchie, Mammo

    2011-01-01

    A numberof Chris Freeman's colleagues were asked to reflect on what they thought describes his life and work in a few words. Some of the colleagues replied including former SPRU students that were taught or supervised by Chris Freeman. Their views on what they thought were Chris Freeman's defining...... life is not free from fluctuations, cycles, disruptions, crises and destructions both human and ecological. Innovation research ought to position itself to address environmental, financial and economic crises. The third is innovation research for development by addressing not only poverty erdaication...

  5. Reflective Writing

    Ahrenkiel Jørgensen, Andriette

    2016-01-01

    In Breve fra min Have (Letters from my Garden), the Swedish landscape architect, Sven-Ingvar Andersson, produces dialogues about his garden to a wide circle of friends, colleagues, deceased and still living acquaintances such as Karen Blixen, Gertrude Stein, C. Th. Sørensen, Albrecht Dürer, Peter...... Høeg etetera. The dialogues work as a tool of reflection in terms of providing opportunity to examine his own beliefs, to explore the possible reasons for engaging in a particular activity. On the basis of Sven-Ingvar Andersson’s book a teaching program at the Aarhus School of Architecture provides...

  6. Reflective Packaging

    1994-01-01

    The aluminized polymer film used in spacecraft as a radiation barrier to protect both astronauts and delicate instruments has led to a number of spinoff applications. Among them are aluminized shipping bags, food cart covers and medical bags. Radiant Technologies purchases component materials and assembles a barrier made of layers of aluminized foil. The packaging reflects outside heat away from the product inside the container. The company is developing new aluminized lines, express mailers, large shipping bags, gel packs and insulated panels for the building industry.

  7. Neutron reflectivity

    Cousin Fabrice

    2015-01-01

    Full Text Available The specular neutron reflectivity is a technique enabling the measurement of neutron scattering length density profile perpendicular to the plane of a surface or an interface, and thereby the profile of chemical composition. The characteristic sizes that are probed range from around 5 Å up 5000 Å. It is a scattering technique that averages information on the entire surface and it is therefore not possible to obtain information within the plane of the interface. The specific properties of neutrons (possibility of tuning the contrast by isotopic substitution, sensitivity to magnetism, negligible absorption, low energy of the incident neutrons makes it particularly interesting in the fields of soft matter, biophysics and magnetic thin films. This course is a basic introduction to the technique and does not address the magnetic reflectivity. It is composed of three parts describing respectively its principle and its formalism, the experimental aspects of the method (spectrometers, samples and two examples related to the materials for energy.

  8. A nebula of gases from Io surrounding Jupiter.

    Krimigis, Stamatios M; Mitchell, Donald G; Hamilton, Douglas C; Dandouras, Jannis; Armstrong, Thomas P; Bolton, Scott J; Cheng, Andrew F; Gloeckler, George; Hsieh, K C; Keath, Edwin P; Krupp, Norbert; Lagg, Andreas; Lanzerotti, Louis J; Livi, Stefano; Mauk, Barry H; McEntire, Richard W; Roelof, Edmond C; Wilken, Berend; Williams, Donald J

    2002-02-28

    Several planetary missions have reported the presence of substantial numbers of energetic ions and electrons surrounding Jupiter; relativistic electrons are observable up to several astronomical units (au) from the planet. A population of energetic (>30[?]keV) neutral particles also has been reported, but the instrumentation was not able to determine the mass or charge state of the particles, which were subsequently labelled energetic neutral atoms. Although images showing the presence of the trace element sodium were obtained, the source and identity of the neutral atoms---and their overall significance relative to the loss of charged particles from Jupiter's magnetosphere---were unknown. Here we report the discovery by the Cassini spacecraft of a fast (>103[?]km[?]s-1) and hot magnetospheric neutral wind extending more than 0.5[?]au from Jupiter, and the presence of energetic neutral atoms (both hot and cold) that have been accelerated by the electric field in the solar wind. We suggest that these atoms originate in volcanic gases from Io, undergo significant evolution through various electromagnetic interactions, escape Jupiter's magnetosphere and then populate the environment around the planet. Thus a 'nebula' is created that extends outwards over hundreds of jovian radii.

  9. Understanding Galactic planetary nebulae with precise/reliable nebular abundances

    García-Hernández, D. A.; Ventura, P.; Delgado-Inglada, G.; Dell'Agli, F.; di Criscienzo, M.; Yagüe, A.

    2017-10-01

    We compare recent precise/reliable nebular abundances - as derived from high-quality optical spectra and the most recent ICFs - in a sample of Galactic planetary nebulae (PNe) with nucleosynthesis predictions (HeCNOCl) from asymptotic giant branch (AGB) ATON models in the metallicity range Z ⊙/4 3.5 M⊙) solar/supersolar metallicity AGBs that experience hot bottom burning (HBB), but other formation channels in low-mass AGBs like extra mixing, stellar rotation, binary interaction, or He pre-enrichment cannot be disregarded until more accurate C/O ratios can be obtained. Two DC PNe show the imprint of advanced CNO processing and deep second dredge-up, suggesting progenitors masses close to the limit to evolve as core collapse supernovae (above 6 M⊙). Their actual C/O ratios, if confirmed, indicate contamination from the third dredge-up, rejecting the hypothesis that the chemical composition of such high-metallicity massive AGBs is modified exclusively by HBB.

  10. Giant Ly α Nebulae in the Illustris Simulation

    Gronke, Max [Institute of Theoretical Astrophysics, University of Oslo, Postboks 1029 Blindern, NO-0315 Oslo (Norway); Bird, Simeon, E-mail: maxbg@astro.uio.no [Department of Physics and Astronomy, Johns Hopkins University, 3400 N. Charles St., Baltimore, MD 21218 (United States)

    2017-02-01

    Several “giant” Ly α nebulae with an extent ≳300 kpc and observed Ly α luminosity of ≳10{sup 44} erg s{sup −1} cm{sup −2} arcsec{sup −2} have recently been detected, and it has been speculated that their presence hints at a substantial cold gas reservoir in small cool clumps not resolved in modern hydrodynamical simulations. We use the Illustris simulation to predict the Ly α emission emerging from large halos ( M > 10{sup 11.5} M {sub ⊙}) at z ∼ 2 and thus test this model. We consider both active galactic nucleus (AGN) and star driven ionization, and compare the simulated surface brightness maps, profiles, and Ly α spectra to a model where most gas is clumped below the simulation resolution scale. We find that with Illustris, no additional clumping is necessary to explain the extents, luminosities, and surface brightness profiles of the “giant Ly α nebulae” observed. Furthermore, the maximal extents of the objects show a wide spread for a given luminosity and do not correlate significantly with any halo properties. We also show how the detected size depends strongly on the employed surface brightness cutoff, and predict that further examples of such objects will be found in the near future.

  11. Helix Nebula: sunshine and clouds on the CERN computing horizon

    Joannah Caborn Wengler

    2012-01-01

    23 petabytes is how much data CERN recorded during 2011, and this number will rise in 2012. In order to respond to the challenge, the IT department is upping its game, amongst other things by participating in the Helix Nebula project, a public-private partnership to create a European cloud-computing platform, as announced in a recent CERN press release.   “We’re not replacing the Grid,” clarifies Bob Jones, responsible for CERN openlab who is also responsible for EC-funded projects in IT, “but looking at three complementary ways of increasing CERN’s computing capacity, so that as demand goes up we can continue to satisfy our users.” “First we are upgrading the electrical and cooling infrastructure of the computer centre in order to increase the availability of critical IT services needed for the Laboratory. This will also provide more floor space in the area called The Barn, allowing for more servers to fit in.”...

  12. Do all Planetary Nebulae result from Common Envelopes?

    De Marco, O.; Moe, M.; Herwig, F.; Politano, M.

    2005-12-01

    The common envelope interaction is responsible for evolved close binaries. Some of these binaries reside in the middle of planetary nebulae (PN). Conventional wisdom has it that only about 10% of all PN contain close binary central stars. Recent observational results, however, strongly suggest that most or even all PN are in close binary systems. Interestingly, our population synthesis calculations predict that the number of post-common envelope PN is in agreement with the total number of PN in the Galaxy. On the other hand, if all stars (single and in binaries) with mass between ˜1-8 M⊙ eject a PN, there would be 10-20 times many more PN in the galaxy than observed. This theoretical result is in agreement with the observations in suggesting that binary interactions play a functional rather than marginal role in the creation of PN. FH acknowledges funds from the U.S. Dept. of Energy, under contract W-7405-ENG-36 to Los Alamos National Laboratory. MP gratefully acknowledges NSF grant AST-0328484 to Marquette University.

  13. Compact continuum radio sources in the Orion Nebula

    Garay, G.; Moran, J.M.; Reid, M.J.; European Southern Observatory, Garching, West Germany)

    1987-01-01

    The Orion Nebula was observed with the VLA in order to search for radio emission from compact H II regions indicative of embedded OB stars or from winds associated with pre-main sequence, low-mass stars. Fourteen of the 21 detected radio sources are within 30 arcsec of Omega 1 Orionis C; 13 of these objects are probably neutral condensations surrounded by ionized envelopes that are excited by the star. If the temperature of the ionized envelopes is 10,000 K and their electron densities decrease as the square of the distance from the core center, then a typical neutral condensation has a radius of 10 to the 15th cm and a peak electron density of 400,000/cu cm. Seven sources are in or near the Orion molecular cloud. Four of the sources have optical counterparts. Two are highly variable radio sources associated with X-ray sources, and two have radio spectra indicative of thermal emission. Two of the three optically invisible sources have radio emission likely to arise in a dense ionized envelope surrounding and excited by an early B-type star. 46 references

  14. Determination of helium and oxygen abundances in gaseous nebulae

    Pronik, V.I.

    1975-01-01

    A new method of determining the abudance of helium and oxygen is proposed. It is based on the statement that functions of atomic distribution with states of ionization may be determined to the sufficient precision by the amount of atoms in two states of ionization. The abudance of helium atoms in nebulae is determined with most probability, since of three possible states of ionization two states with the overwhelming majority atoms may be directly observed. The amount of He++ ions is determined from He 2 recombination lines, and the amount of He+ ions is from He1 lines. The total abudance of He atoms can be found from the observed ratios of I(4686)/I(Hsub(β)) and I(4471)/I(Hsub(β)) at any degree of ionization. These ratios slightly depend on the electron temperature. For oxygen, unlike helium, the observed ratios depend on the electron temperature of gas, and at high densities they also depend on the density of electrons (it is necessary to take account of deactivation of the excited level by electron impacts). Constructed are curves of equal abundance He/H=const for determining He/H according to the ratios observed I(4686)/I(Hsub(β)) and I(4471)/I(Hsub(β)) and curves of equal abudance O/H=const for determining O/H according to the ratios observed I(3727)/I(Hsub(/b)) and I(Nsub(1)+Nsub(2))/I(Hsub(β)), corrected preliminarily for density and temperature

  15. On the origin of cometary nuclei in the presolar nebula

    Biermann, L.; Michel, K.W.

    1978-01-01

    If it is assumed that the cometary nuclei originated by the gravitational instability of a dust layer, which formed in the equatorial plane of the outer parts of the presolar nebula (PSN) during a period of approximate equilibrium between gravity, centrifugal force, and the pressure gradient a simple relation is derived between the PSN's temperature and the upper limit to the mass of the planetesimals. It contains, beside the density of the cometary nuclei, rhosub(p) only the factor (by mass) of the condensable elements in the PSN, which became part of the dust particle disc, which, on the basis of available observational evidence on the solid particles in interplanetary and interstellar space and of theoretical considerations on the relationship between them and on the sedimentation process, is found to be of the order of >=approximately 10%; this estimate will require still further justification. Assuming a temperature in the range 15-20 K, an equatorial diameter of the PSN of 0.1 pc and rhosub(p) approximately a few 0.1 g/cm 3 , upper limits for the planetesimal's mass of approximately 10 18 g and for their radius of approximately 10km are obtained (on the basis of conservation of circulation, of mass and of angular momentum in the differential rotating disc), in fair agreement with observation. (Auth.)

  16. Single rotating stars and the formation of bipolar planetary nebula

    García-Segura, G. [Instituto de Astronomía, Universidad Nacional Autónoma de Mexico, Km. 103 Carr. Tijuana-Ensenada, 22860 Ensenada, B. C. (Mexico); Villaver, E. [Departamento de Física Teórica, Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Langer, N. [Argelander-Institut für Astronomie, Universität Bonn, D-53121 Bonn (Germany); Yoon, S.-C. [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Seoul, 151-747 (Korea, Republic of); Manchado, A., E-mail: ggs@astrosen.unam.mx [Instituto de Astrofísica de Canarias, Via Láctea s/n, E-38200 La Laguna, Tenerife (Spain)

    2014-03-10

    We have computed new stellar evolution models that include the effects of rotation and magnetic torques under different hypotheses. The goal is to test whether a single star can sustain the rotational velocities needed in the envelope for magnetohydrodynamical(MHD) simulations to shape bipolar planetary nebulae (PNe) when high mass-loss rates take place. Stellar evolution models with main sequence masses of 2.5 and 5 M {sub ☉} and initial rotational velocities of 250 km s{sup –1} have been followed through the PNe formation phase. We find that stellar cores have to be spun down using magnetic torques in order to reproduce the rotation rates observed for white dwarfs. During the asymptotic giant branch phase and beyond, the magnetic braking of the core has a practically null effect on increasing the rotational velocity of the envelope since the stellar angular momentum is efficiently removed by the wind. We have also tested the best possible case scenarios in rather non-physical contexts to give enough angular momentum to the envelope. We find that we cannot get the envelope of a single star to rotate at the speeds needed for MHD simulations to form bipolar PNe. We conclude that single stellar rotators are unlikely to be the progenitors of bipolar PNe under the current MHD model paradigm.

  17. Dust and molecules in extra-galactic planetary nebulae

    Garcia-Hernandez, Domingo Aníbal

    2015-08-01

    Extra-galactic planetary nebulae (PNe) permit the study of dust and molecules in metallicity environments other than the Galaxy. Their known distances lower the number of free parameters in the observations vs. models comparison, providing strong constraints on the gas-phase and solid-state astrochemistry models. Observations of PNe in the Galaxy and other Local Group galaxies such as the Magellanic Clouds (MC) provide evidence that metallicity affects the production of dust as well as the formation of complex organic molecules and inorganic solid-state compounds in their circumstellar envelopes. In particular, the lower metallicity MC environments seem to be less favorable to dust production and the frequency of carbonaceous dust features and complex fullerene molecules is generally higher with decreasing metallicity. Here, I present an observational review of the dust and molecular content in extra-galactic PNe as compared to their higher metallicity Galactic counterparts. A special attention is given to the level of dust processing and the formation of complex organic molecules (e.g., polycyclic aromatic hydrocarbons, fullerenes, and graphene precursors) depending on metallicity.

  18. Central stars of planetary nebulae: New spectral classifications and catalogue

    Weidmann, W. A.; Gamen, R.

    2011-02-01

    Context. There are more than 3000 confirmed and probable known Galactic planetary nebulae (PNe), but central star spectroscopic information is available for only 13% of them. Aims: We undertook a spectroscopic survey of central stars of PNe at low resolution and compiled a large list of central stars for which information was dispersed in the literature. Methods: We observed 45 PNs using the 2.15 m telescope at Casleo, Argentina. Results: We present a catalogue of 492 confirmed and probable CSPN and provide a preliminary spectral classification for 45 central star of PNe. This revises previous values of the proportion of CSPN with atmospheres poor in hydrogen in at least 30% of cases and provide statistical information that allows us to infer the origin of H-poor stars. Based on data collected at the Complejo Astronómico El Leoncito (CASLEO), which is operated under agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina y Universidades Nacionales de La Plata, Córdoba y San Juan, Argentina.

  19. OH+ emission from cometary knots in planetary nebulae

    Priestley, F. D.; Barlow, M. J.

    2018-05-01

    We model the molecular emission from cometary knots in planetary nebulae (PNe) using a combination of photoionization and photodissociation region (PDR) codes, for a range of central star properties and gas densities. Without the inclusion of ionizing extreme ultraviolet (EUV) radiation, our models require central star temperatures T* to be near the upper limit of the range investigated in order to match observed H2 and OH+ surface brightnesses consistent with observations - with the addition of EUV flux, our models reproduce observed OH+ surface brightnesses for T* ≥ 100 kK. For T* non-detection of this molecule in PNe with such central star temperatures. Our predicted level of H2 emission is somewhat weaker than commonly observed in PNe, which may be resolved by the inclusion of shock heating or fluorescence due to UV photons. Some of our models also predict ArH+ and HeH+ rotational line emission above detection thresholds, despite neither molecule having been detected in PNe, although the inclusion of photodissociation by EUV photons, which is neglected by our models, would be expected to reduce their detectability.

  20. Hydrogen-deficient Central Stars of Planetary Nebulae

    Todt, H.; Kniazev, A. Y.; Gvaramadze, V. V.; Hamann, W.-R.; Pena, M.; Graefener, G.; Buckley, D.; Crause, L.; Crawford, S. M.; Gulbis, A. A. S.; Hettlage, C.; Hooper, E.; Husser, T.-O.; Kotze, P.; Loaring, N.; Nordsieck, K. H.; O'Donoghue, D.; Pickering, T.; Potter, S.; Romero-Colmenero, E.; Vaisanen, P.; Williams, T.; Wolf, M.

    2015-06-01

    A significant number of the central stars of planetary nebulae (CSPNe) are hydrogen-deficient and are considered as the progenitors of H-deficient white dwarfs. Almost all of these H-deficient CSPNe show a chemical composition of helium, carbon, and oxygen. Most of them exhibit Wolf-Rayet-like emission line spectra and are therefore classified as of spectral type [WC]. In the last years, CSPNe of other Wolf-Rayet spectral subtypes have been identified, namely PB 8 (spectral type [WN/WC]), IC 4663 and Abell 48 (spectral type [WN]). We performed spectral analyses for a number of Wolf-Rayet type central stars of different evolutionary stages with the help of our Potsdam Wolf-Rayet (PoWR) model code for expanding atmospheres to determine relevant stellar parameters. The results of our recent analyses will be presented in the context of stellar evolution and white dwarf formation. Especially the problems of a uniform evolutionary channel for [WC] stars as well as constraints to the formation of [WN] or [WN/WC] subtype stars will be addressed.

  1. Turbulent Concentration of MM-Size Particles in the Protoplanetary Nebula: Scaled-Dependent Multiplier Functions

    Cuzzi, Jeffrey N.; Hartlep, Thomas; Weston, B.; Estremera, Shariff Kareem

    2014-01-01

    The initial accretion of primitive bodies (asteroids and TNOs) from freely-floating nebula particles remains problematic. Here we focus on the asteroids where constituent particle (read "chondrule") sizes are observationally known; similar arguments will hold for TNOs, but the constituent particles in those regions will be smaller, or will be fluffy aggregates, and are unobserved. Traditional growth-bysticking models encounter a formidable "meter-size barrier" [1] (or even a mm-cm-size barrier [2]) in turbulent nebulae, while nonturbulent nebulae form large asteroids too quickly to explain long spreads in formation times, or the dearth of melted asteroids [3]. Even if growth by sticking could somehow breach the meter size barrier, other obstacles are encountered through the 1-10km size range [4]. Another clue regarding planetesimal formation is an apparent 100km diameter peak in the pre-depletion, pre-erosion mass distribution of asteroids [5]; scenarios leading directly from independent nebula particulates to this size, which avoid the problematic m-km size range, could be called "leapfrog" scenarios [6-8]. The leapfrog scenario we have studied in detail involves formation of dense clumps of aerodynamically selected, typically mm-size particles in turbulence, which can under certain conditions shrink inexorably on 100-1000 orbit timescales and form 10-100km diameter sandpile planetesimals. The typical sizes of planetesimals and the rate of their formation [7,8] are determined by a statistical model with properties inferred from large numerical simulations of turbulence [9]. Nebula turbulence can be described by its Reynolds number Re = L/eta sup(4/3), where L = ETA alpha sup (1/2) the largest eddy scale, H is the nebula gas vertical scale height, and a the nebula turbulent viscosity parameter, and ? is the Kolmogorov or smallest scale in turbulence (typically about 1km), with eddy turnover time t?. In the nebula, Re is far larger than any numerical simulation can

  2. Formation of solid materials in the preplanetary nebula and the composition of chondrites

    Izakov, M.N.

    1986-07-01

    On the basis of the model of the formation of the preplanetary nebula as an accretion disk during the formation of the sun, the hypothesis is proposed that a significant fraction of the solid materials of the preplanetary nebula was formed by the successive condensation of the components of the gas of solar composition during its motion from the hot, dense region near the protosun to the periphery of the nebula into regions of ever decreasing values of temperature and pressure. The hypothesis removes the contradiction materials and the presence of traces of high-temperature phenomena in chondrite materials and the conclusion that there were never high temperature in the preplanetary nebula at distances of 2-4 AU from the sun, where meteorites encountering the earth originate, and also explains a number of properties of chondrites. It follows from this hypothesis that the mass and angular momentum of the nebula were close to their minimum possible values and that the loss of the nebular gas had already begun at the final stage of its formation.

  3. Formation of solid materials in the preplanetary nebula and the composition of chondrites

    Izakov, M.N.

    1986-01-01

    On the basis of the model of the formation of the preplanetary nebula as an accretion disk during the formation of the sun, the hypothesis is proposed that a significant fraction of the solid materials of the preplanetary nebula was formed by the successive condensation of the components of the gas of solar composition during its motion from the hot, dense region near the protosun to the periphery of the nebula into regions of ever decreasing values of temperature and pressure. The hypothesis removes the contradiction materials and the presence of traces of high-temperature phenomena in chondrite materials and the conclusion that there were never high temperature in the preplanetary nebula at distances of 2-4 AU from the sun, where meteorites encountering the earth originate, and also explains a number of properties of chondrites. It follows from this hypothesis that the mass and angular momentum of the nebula were close to their minimum possible values and that the loss of the nebular gas had already begun at the final stage of its formation

  4. Chemical composition and origin of the Wolf-Rayet ring Nebula NGC 6888

    Kwitter, K.B.

    1981-01-01

    We have obtained spectrophotometric observations of NGC 6888, a ring nebula surrounding the Population I Wolf-Rayet star HD 192163, in order to determine the physical conditions and chemical abundances in this object. We conclude that NGC 6888 is enriched in nitrogen and helium by factors of about 9 and 2, respectively, compared with the Orion Nebula. This enrichment is a result of contamination of the ambient abundances by the nigrogen-rich and helium-rich wind from the central Wolf-rayet star. We have interpreted NGC 6888 as an interstellar bubble, according to recent theory, and calculate an approximate age for the nebula of 18,000 years. The fraction of nebular mass contributed by the central star can be estimated from published stellar abundances; we calculate that the stellar wind has provided approx.10% of the observed nebular mass. If this nebula is representative, then the total mass contributed to a ring nebula by stellar wind is small (< or approx. =1M/sub sun/). This suggests that mass loss from stars in the Wolf-Rayet phase does not play a significant role in the nitrogen and helium enrichment of the interstellar medium

  5. DISCOVERY OF TWIN WOLF-RAYET STARS POWERING DOUBLE RING NEBULAE

    Mauerhan, Jon C.; Wachter, Stefanie; Van Dyk, Schuyler D.; Hoard, D. W.; Morris, Patrick W.

    2010-01-01

    We have spectroscopically discovered a pair of twin, nitrogen-type, hydrogen-rich, Wolf-Rayet stars (WN8-9h) that are both surrounded by circular, mid-infrared-bright nebulae detected with the Spitzer Space Telescope and MIPS instrument. The emission is probably dominated by a thermal continuum from cool dust, but also may contain contributions from atomic line emission. There is no counterpart at shorter Spitzer/IRAC wavelengths, indicating a lack of emission from warm dust. The two nebulae are probably wind-swept stellar ejecta released by the central stars during a prior evolutionary phase. The nebulae partially overlap on the sky and we speculate on the possibility that they are in the early stage of a collision. Two other evolved massive stars have also been identified within the area subtended by the nebulae, including a carbon-type Wolf-Rayet star (WC8) and an O7-8 III-I star, the latter of which appears to be embedded in one of the larger WN8-9h nebulae. The derived distances to these stars imply that they are coeval members of an association lying 4.9 ± 1.2 kpc from Earth, near the intersection of the Galaxy's Long Bar and the Scutum-Centaurus spiral arm. This new association represents an unprecedented display of complex interactions between multiple stellar winds, outflows, and the radiation fields of evolved massive stars.

  6. A SUCCESSFUL BROADBAND SURVEY FOR GIANT Ly{alpha} NEBULAE. I. SURVEY DESIGN AND CANDIDATE SELECTION

    Prescott, Moire K. M. [Department of Physics, Broida Hall, Mail Code 9530, University of California, Santa Barbara, CA 93106 (United States); Dey, Arjun; Jannuzi, Buell T., E-mail: mkpresco@physics.ucsb.edu [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)

    2012-04-01

    Giant Ly{alpha} nebulae (or Ly{alpha} 'blobs') are likely sites of ongoing massive galaxy formation, but the rarity of these powerful sources has made it difficult to form a coherent picture of their properties, ionization mechanisms, and space density. Systematic narrowband Ly{alpha} nebula surveys are ongoing, but the small redshift range covered and the observational expense limit the comoving volume that can be probed by even the largest of these surveys and pose a significant problem when searching for such rare sources. We have developed a systematic search technique designed to find large Ly{alpha} nebulae at 2 {approx}< z {approx}< 3 within deep broadband imaging and have carried out a survey of the 9.4 deg{sup 2} NOAO Deep Wide-Field Survey Booetes field. With a total survey comoving volume of Almost-Equal-To 10{sup 8} h{sup -3}{sub 70} Mpc{sup 3}, this is the largest volume survey for Ly{alpha} nebulae ever undertaken. In this first paper in the series, we present the details of the survey design and a systematically selected sample of 79 candidates, which includes one previously discovered Ly{alpha} nebula.

  7. A SUCCESSFUL BROADBAND SURVEY FOR GIANT Ly{alpha} NEBULAE. II. SPECTROSCOPIC CONFIRMATION

    Prescott, Moire K. M. [Department of Physics, University of California, Broida Hall, Mail Code 9530, Santa Barbara, CA 93106 (United States); Dey, Arjun; Jannuzi, Buell T., E-mail: mkpresco@physics.ucsb.edu [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)

    2013-01-01

    Using a systematic broadband search technique, we have carried out a survey for large Ly{alpha} nebulae (or Ly{alpha} {sup b}lobs{sup )} at 2 {approx}< z {approx}< 3 within 8.5 deg{sup 2} of the NOAO Deep Wide-Field Survey Booetes field, corresponding to a total survey comoving volume of Almost-Equal-To 10{sup 8} h {sup -3} {sub 70} Mpc{sup 3}. Here, we present our spectroscopic observations of candidate giant Ly{alpha} nebulae. Of 26 candidates targeted, 5 were confirmed to have Ly{alpha} emission at 1.7 {approx}< z {approx}< 2.7, 4 of which were new discoveries. The confirmed Ly{alpha} nebulae span a range of Ly{alpha} equivalent widths, colors, sizes, and line ratios, and most show spatially extended continuum emission. The remaining candidates did not reveal any strong emission lines, but instead exhibit featureless, diffuse, blue continuum spectra. Their nature remains mysterious, but we speculate that some of these might be Ly{alpha} nebulae lying within the redshift desert (i.e., 1.2 {approx}< z {approx}< 1.6). Our spectroscopic follow-up confirms the power of using deep broadband imaging to search for the bright end of the Ly{alpha} nebula population across enormous comoving volumes.

  8. A Study of Planetary Nebulae using the Faint Object Infrared Camera for the SOFIA Telescope

    Davis, Jessica

    2012-01-01

    A planetary nebula is formed following an intermediate-mass (1-8 solar M) star's evolution off of the main sequence; it undergoes a phase of mass loss whereby the stellar envelope is ejected and the core is converted into a white dwarf. Planetary nebulae often display complex morphologies such as waists or torii, rings, collimated jet-like outflows, and bipolar symmetry, but exactly how these features form is unclear. To study how the distribution of dust in the interstellar medium affects their morphology, we utilize the Faint Object InfraRed CAmera for the SOFIA Telescope (FORCAST) to obtain well-resolved images of four planetary nebulae--NGC 7027, NGC 6543, M2-9, and the Frosty Leo Nebula--at wavelengths where they radiate most of their energy. We retrieve mid infrared images at wavelengths ranging from 6.3 to 37.1 micron for each of our targets. IDL (Interactive Data Language) is used to perform basic analysis. We select M2-9 to investigate further; analyzing cross sections of the southern lobe reveals a slight limb brightening effect. Modeling the dust distribution within the lobes reveals that the thickness of the lobe walls is higher than anticipated, or rather than surrounding a vacuum surrounds a low density region of tenuous dust. Further analysis of this and other planetary nebulae is needed before drawing more specific conclusions.

  9. THE RADIO-2 mm SPECTRAL INDEX OF THE CRAB NEBULA MEASURED WITH GISMO

    Arendt, R. G.; George, J. V.; Staguhn, J. G.; Benford, D. J.; Fixsen, D. J.; Maher, S. F.; Moseley, S. H.; Sharp, E.; Wollack, E. J.; Devlin, M. J.; Dicker, S. R.; Korngut, P. M.; Irwin, K. D.; Jhabvala, C. A.; Miller, T. M.; Kovacs, A.; Mason, B. S.; Navarro, S.; Sievers, A.; Sievers, J. L.

    2011-01-01

    We present results of 2 mm observations of the Crab Nebula, obtained using the Goddard-IRAM Superconducting 2 Millimeter Observer (GISMO) bolometer camera on the IRAM 30 m telescope. Additional 3.3 mm observations with the MUSTANG bolometer array on the Green Bank Telescope are also presented. The integrated 2 mm flux density of the Crab Nebula provides no evidence for the emergence of a second synchrotron component that has been proposed. It is consistent with the radio power-law spectrum, extrapolated up to a break frequency of log (ν b [GHz]) = 2.84 ± 0.29 or ν b = 695 +651 -336 GHz. The Crab Nebula is well resolved by the ∼16.''7 beam (FWHM) of GISMO. Comparison to radio data at comparable spatial resolution enables us to confirm significant spatial variation of the spectral index between 21 cm and 2 mm. The main effect is a spectral flattening in the inner region of the Crab Nebula, correlated with the toroidal structure at the center of the nebula that is prominent in the near-IR through X-ray regime.

  10. A SUCCESSFUL BROADBAND SURVEY FOR GIANT Lyα NEBULAE. I. SURVEY DESIGN AND CANDIDATE SELECTION

    Prescott, Moire K. M.; Dey, Arjun; Jannuzi, Buell T.

    2012-01-01

    Giant Lyα nebulae (or Lyα 'blobs') are likely sites of ongoing massive galaxy formation, but the rarity of these powerful sources has made it difficult to form a coherent picture of their properties, ionization mechanisms, and space density. Systematic narrowband Lyα nebula surveys are ongoing, but the small redshift range covered and the observational expense limit the comoving volume that can be probed by even the largest of these surveys and pose a significant problem when searching for such rare sources. We have developed a systematic search technique designed to find large Lyα nebulae at 2 ∼ 2 NOAO Deep Wide-Field Survey Boötes field. With a total survey comoving volume of ≈10 8 h –3 70 Mpc 3 , this is the largest volume survey for Lyα nebulae ever undertaken. In this first paper in the series, we present the details of the survey design and a systematically selected sample of 79 candidates, which includes one previously discovered Lyα nebula.

  11. THE EVOLUTION OF THE KINEMATICS OF NEBULAR SHELLS IN PLANETARY NEBULAE IN THE MILKY WAY BULGE

    Richer, Michael G.; Lopez, Jose Alberto; Garcia-Diaz, Maria Teresa; Clark, David M.; Pereyra, Margarita; Diaz-Mendez, Enrique

    2010-01-01

    We study the line widths in the [O III]λ5007 and Hα lines for two groups of planetary nebulae in the Milky Way bulge based upon spectroscopy obtained at the Observatorio Astronomico Nacional in the Sierra San Pedro Martir (OAN-SPM) using the Manchester Echelle Spectrograph. The first sample includes objects early in their evolution, having high Hβ luminosities, but [O III]λ5007/Hβ 0.5. These planetary nebulae represent evolutionary phases preceding and following those of the objects studied by Richer et al. in 2008. Our sample of planetary nebulae with weak [O III]λ5007 has a line width distribution similar to that of the expansion velocities of the envelopes of asymptotic giant branch stars and shifted to systematically lower values as compared to the less evolved objects studied by Richer et al. The sample with strong He II λ4686 has a line width distribution indistinguishable from that of the more evolved objects from Richer et al., but a distribution in angular size that is systematically larger and so they are clearly more evolved. These data and those of Richer et al. form a homogeneous sample from a single Galactic population of planetary nebulae, from the earliest evolutionary stages until the cessation of nuclear burning in the central star. They confirm the long-standing predictions of hydrodynamical models of planetary nebulae, where the kinematics of the nebular shell are driven by the evolution of the central star.

  12. Discovery of a Pulsar Wind Nebula Candidate in the Cygnus Loop

    Katsuda, Satoru; Tsunemi, Hiroshi; Mori, Koji; Uchida, Hiroyuki; Petre, Robert; Yamada, Shin'ya; Tamagawa, Toru

    2012-01-01

    We report on a discovery of a diffuse nebula containing a point-like source in the southern blowout region of the Cygnus Loop supernova remnant, based on Suzaku and XMM-Newton observations. The X-ray spectra from the nebula and the point-like source are well represented by an absorbed power-law model with photon indices of 2.2+/-0.1 and 1.6+/-0.2, respectively. The photon indices as well as the flux ratio of F(sub nebula)/F(sub point-like) approx. 4 lead us to propose that the system is a pulsar wind nebula, although pulsations have not yet been detected. If we attribute its origin to the Cygnus Loop supernova, then the 0.5-8 keV luminosity of the nebula is computed to be 2.1x10(exp 31)(d/540pc)(exp 2)ergss/2, where d is the distance to the Loop. This implies a spin-down loss-energy E approx. 2.6x10(exp 35)(d/540pc)(exp 2)ergs/s. The location of the neutron star candidate, approx.2deg away from the geometric center of the Loop, implies a high transverse velocity of approx.1850(theta/2deg)(d/540pc)(t/10kyr)/k/s assuming the currently accepted age of the Cygnus Loop.

  13. Photometric investigation of possible binary occurrence in the central stars of seventeen planetary nebulae

    Drummond, J.D. III.

    1980-01-01

    A comprehensive literature search was conducted for all possible bihary central stars in planetary nebulae. The results, which include all known and suspected visual, spectroscopic, and spectrum binaries, as well as all reported variable central stars, are presented in a series of tables. A photoelectric study was conducted in order to determine the status of short period (on the order of hours) variability of the central regions of seventeen planetary nebulae. Only the stellar appearing planetary nebula M1-2 (PK 133-8 0 1) was found to be variable. Its short (4.0002 hours) period suggests that it may be only the second eclipsing binary found among central stars to date. A method of concentric apertures was developed to determine the amount of light contributed by the central star vis-a-vis the nebula through a given aperture and filter. The procedure enabled UBV magnitudes and colors (and the errors) of central stars to be measured, including some in the sample of seventeen for which no previous values have been published. Mean nebular UBV magnitudes, surface brightnesses, and color indices were also found with the technique, and represent the first such published measurements. Various UBV two-parameter were constructed, revealing possible nebular/stellar sequences; a star-plus-nebula two-color diagram identifies three spectral classes of central stars, and two suspected binaries in the seventeen studied

  14. A study of the compact nebulae VV 8 and M3-27

    Adams, T.F.

    1975-01-01

    New photometric observations of the lines and continuum in the compact nebulae VV 8 and M3-27 are presented. The data for VV 8 are very similar to those obtained by O'Dell nearly 10 years ago. Both nebulae have high electron densities and are self-absorbed in Hα. Parameters describing the physical conditions are estimated using the observed Balmer and O iii line strengths. By comparing the observations with suitable models for young planetary nebulae, the abundances of helium, oxygen, and neon are shown to be normal. The N ii lines are stronger than predicted. The continuum in M3-27 is shown to be in good agreement with theory, while the continuum in VV 8 in the visible and infrared is much brighter than predicted. The similarity between the line spectra and inferred properties of the nebulae suggests that the optical continuum in VV 8 is unrelated to the nebula, and may come from a late-type companion in a binary. Serious difficulties remain, however, concerning the absolute magnitude and color of the companion in the binary model. Some implications of Zipoy's shell star model are also examined

  15. SYNCHROTRON HEATING BY A FAST RADIO BURST IN A SELF-ABSORBED SYNCHROTRON NEBULA AND ITS OBSERVATIONAL SIGNATURE

    Yang, Yuan-Pei; Dai, Zi-Gao; Zhang, Bing

    2016-01-01

    Fast radio bursts (FRBs) are mysterious transient sources. If extragalactic, as suggested by their relative large dispersion measures, their brightness temperatures must be extremely high. Some FRB models (e.g., young pulsar model, magnetar giant flare model, or supra-massive neutron star collapse model) suggest that they may be associated with a synchrotron nebula. Here we study a synchrotron-heating process by an FRB in a self-absorbed synchrotron nebula. If the FRB frequency is below the synchrotron self-absorption frequency of the nebula, electrons in the nebula would absorb FRB photons, leading to a harder electron spectrum and enhanced self-absorbed synchrotron emission. In the meantime, the FRB flux is absorbed by the nebula electrons. We calculate the spectra of FRB-heated synchrotron nebulae, and show that the nebula spectra would show a significant hump in several decades near the self-absorption frequency. Identifying such a spectral feature would reveal an embedded FRB in a synchrotron nebula

  16. SYNCHROTRON HEATING BY A FAST RADIO BURST IN A SELF-ABSORBED SYNCHROTRON NEBULA AND ITS OBSERVATIONAL SIGNATURE

    Yang, Yuan-Pei; Dai, Zi-Gao [School of Astronomy and Space Science, Nanjing University, Nanjing 210093 (China); Zhang, Bing, E-mail: zhang@physics.unlv.edu [Department of Physics and Astronomy, University of Nevada, Las Vegas, NV 89154 (United States)

    2016-03-01

    Fast radio bursts (FRBs) are mysterious transient sources. If extragalactic, as suggested by their relative large dispersion measures, their brightness temperatures must be extremely high. Some FRB models (e.g., young pulsar model, magnetar giant flare model, or supra-massive neutron star collapse model) suggest that they may be associated with a synchrotron nebula. Here we study a synchrotron-heating process by an FRB in a self-absorbed synchrotron nebula. If the FRB frequency is below the synchrotron self-absorption frequency of the nebula, electrons in the nebula would absorb FRB photons, leading to a harder electron spectrum and enhanced self-absorbed synchrotron emission. In the meantime, the FRB flux is absorbed by the nebula electrons. We calculate the spectra of FRB-heated synchrotron nebulae, and show that the nebula spectra would show a significant hump in several decades near the self-absorption frequency. Identifying such a spectral feature would reveal an embedded FRB in a synchrotron nebula.

  17. A second list of new planetary nebulae found on United Kingdom 1.2-m Schmidt telescope plates

    Longmore, A.J.; Tritton, S.B.

    1980-01-01

    Positions, photographs and descriptions are given for 11 new planetary nebulae discovered on United Kingdom Schmidt plates. One of the planetary nebulae has the highest galactic latitude of any known planetary, and may be associated with a magnitude 9 G5 star. Near-infrared (J,H,K) magnitudes are given for the star. (author)

  18. Detonative propagation and accelerative expansion of the Crab Nebula shock front.

    Gao, Yang; Law, Chung K

    2011-10-21

    The accelerative expansion of the Crab Nebula's outer envelope is a mystery in dynamics, as a conventional expanding blast wave decelerates when bumping into the surrounding interstellar medium. Here we show that the strong relativistic pulsar wind bumping into its surrounding nebula induces energy-generating processes and initiates a detonation wave that propagates outward to form the current outer edge, namely, the shock front, of the nebula. The resulting detonation wave, with a reactive downstream, then provides the needed power to maintain propagation of the shock front. Furthermore, relaxation of the curvature-induced reduction of the propagation velocity from the initial state of formation to the asymptotic, planar state of Chapman-Jouguet propagation explains the observed accelerative expansion. Potential richness in incorporating reactive fronts in the description of various astronomical phenomena is expected. © 2011 American Physical Society

  19. Detection of gamma-ray emission from the Vela pulsar wind nebula with AGILE.

    Pellizzoni, A; Trois, A; Tavani, M; Pilia, M; Giuliani, A; Pucella, G; Esposito, P; Sabatini, S; Piano, G; Argan, A; Barbiellini, G; Bulgarelli, A; Burgay, M; Caraveo, P; Cattaneo, P W; Chen, A W; Cocco, V; Contessi, T; Costa, E; D'Ammando, F; Del Monte, E; De Paris, G; Di Cocco, G; Di Persio, G; Donnarumma, I; Evangelista, Y; Feroci, M; Ferrari, A; Fiorini, M; Fuschino, F; Galli, M; Gianotti, F; Hotan, A; Labanti, C; Lapshov, I; Lazzarotto, F; Lipari, P; Longo, F; Marisaldi, M; Mastropietro, M; Mereghetti, S; Moretti, E; Morselli, A; Pacciani, L; Palfreyman, J; Perotti, F; Picozza, P; Pittori, C; Possenti, A; Prest, M; Rapisarda, M; Rappoldi, A; Rossi, E; Rubini, A; Santolamazza, P; Scalise, E; Soffitta, P; Striani, E; Trifoglio, M; Vallazza, E; Vercellone, S; Verrecchia, F; Vittorini, V; Zambra, A; Zanello, D; Giommi, P; Colafrancesco, S; Antonelli, A; Salotti, L; D'Amico, N; Bignami, G F

    2010-02-05

    Pulsars are known to power winds of relativistic particles that can produce bright nebulae by interacting with the surrounding medium. These pulsar wind nebulae are observed by their radio, optical, and x-ray emissions, and in some cases also at TeV (teraelectron volt) energies, but the lack of information in the gamma-ray band precludes drawing a comprehensive multiwavelength picture of their phenomenology and emission mechanisms. Using data from the AGILE satellite, we detected the Vela pulsar wind nebula in the energy range from 100 MeV to 3 GeV. This result constrains the particle population responsible for the GeV emission and establishes a class of gamma-ray emitters that could account for a fraction of the unidentified galactic gamma-ray sources.

  20. Two-zone model for the broadband Crab nebula spectrum: microscopic interpretation

    Fraschetti F.

    2017-01-01

    Full Text Available We develop a simple two-zone interpretation of the broadband baseline Crab nebula spectrum between 10−5 eV and ~ 100 TeV by using two distinct log-parabola energetic electrons distributions. We determine analytically the very-high energy photon spectrum as originated by inverse-Compton scattering of the far-infrared soft ambient photons within the nebula off a first population of electrons energized at the nebula termination shock. The broad and flat 200 GeV peak jointly observed by Fermi/LAT and MAGIC is naturally reproduced. The synchrotron radiation from a second energetic electron population explains the spectrum from the radio range up to ~ 10 keV. We infer from observations the energy dependence of the microscopic probability of remaining in proximity of the shock of the accelerating electrons.

  1. The Extended X-ray Nebula of PSR J1420-6048

    Van Etten, Adam; Romani, Roger W.; /Stanford U., Phys. Dept.

    2011-08-19

    The vicinity of the unidentified EGRET source 3EG J1420-6038 has undergone extensive study in the search for counterparts, revealing the energetic young pulsar PSR J1420-6048 and its surrounding wind nebula as a likely candidate for at least part of the emission from this bright and extended gamma-ray source. We report on new Suzaku observations of PSR J1420-6048, along with analysis of archival XMM Newton data. The low background of Suzaku permits mapping of the extended X-ray nebula, indicating a tail stretching {approx} 8 minutes north of the pulsar. The X-ray data, along with archival radio and VHE data, hint at a pulsar birthsite to the North, and yield insights into its evolution and the properties of the ambient medium. We further explore such properties by modeling the spectral energy distribution (SED) of the extended nebula.

  2. Inductive Spikes in the Crab Nebula: A Theory of γ-Ray Flares.

    Kirk, John G; Giacinti, Gwenael

    2017-11-24

    We show that the mysterious, rapidly variable emission at ∼400  MeV observed from the Crab Nebula by the AGILE and Fermi satellites could be the result of a sudden drop in the mass loading of the pulsar wind. The current required to maintain wave activity in the wind is then carried by very few particles of a high Lorentz factor. On impacting the nebula, these particles produce a tightly beamed, high-luminosity burst of hard gamma rays, similar to those observed. This implies that (i) the emission is synchrotron radiation in the toroidal field of the nebula and, therefore, linearly polarized and (ii) this mechanism potentially contributes to the gamma-ray emission from other powerful pulsars, such as the Magellanic Cloud objects J0537-6910 and B0540-69.

  3. Spectral analysis of the Crab Pulsar and Nebula with the Fermi Large Area Telescope

    Loparco, F.

    2011-01-01

    The Crab Pulsar is a relatively young neutron star. The Pulsar is the central star in the Crab Nebula, a remnant of the supernova SN 1054, which was observed on Earth in the year 1054. The Crab Pulsar has been extensively observed in the gamma-ray energy band by the Large Area Telescope (LAT), the main instrument onboard the Fermi gamma-ray space telescope, during its first months of data taking. The LAT data have been used to reconstruct the fluxes and the energy spectra of the pulsed gamma-ray component and of the gamma-rays from the Nebula. The results on the pulsed component are in good agreement with the previous measurement from EGRET, while the results on the Nebula are consistent with the observations from Earth based telescopes.

  4. The Wolf-Rayet nebula NGC 6888 as a pressure driven bubble

    Marston, A.P.; Meaburn, J.

    1988-01-01

    Profiles of the Hα and [NII] emission lines have been obtained across the major axis of the Wolf-Rayet ring nebula NGC6888 with the Manchester echelle spectrometer combined with the Isaac Newton Telescope. Although triple profiles are found, this nebula is shown to approximate to a shell of radius 3pc expanding at 85 km s -1 . The ionized mass in the shell is 3.5 ± 1.2 M solar masses . IRAS survey maps also reveal a shell of neutral material containing 40 M solar masses , assuming the far infrared continuum emission from warm dust dominates the line emission. If it is assumed that this mass is also expanding at 85 km s -1 it is shown that the nebula is a pressure driven bubble, which conserves the kinetic energy of the driving stellar wind. (author)

  5. CO survey of the dark nebulae in Perseus, Taurus, and Auriga

    Ungerechts, H.; Thaddeus, P.

    1987-01-01

    A new SIS receiver with extremely low noise temperature, used on the Columbia 1.2-m telescope has permitted mapping CO rapidly with full sampling. Results are presented of a survey for which the angular resolution of the telescope was reduced to 0.5 deg, allowing the observations for the complete region of 750 square degrees to be finished within four months, while retaining sufficient resolution to see significant substructure. Most positions with emission are in the Taurus-Auriga dark nebulae, a cloud associated with IC 348 and NGC 1333, and a cloud associated with the California nebula (NGC 1499) and NGC 1579, which overlaps the northern Taurus-Auriga nebulae but is separated from them in velocity. Also seen were several small clouds at Galactic latitude -25 deg to -35 deg southwest of the Taurus clouds, and the L1558 and L1551 clouds in the south. 89 references

  6. Discovery of Spatial and Spectral Structure in the X-Ray Emission from the Crab Nebula

    Weisskopf, Martin C.; Hester, J. Jeff; Tennant, Allyn F.; Elsner, Ronald F.; Schulz, Norbert S.; Marshall, Herman L.; Karovska, Margarita; Nichols, Joy S.; Swartz, Douglas A.; Kolodziejczak, Jeffery J.

    2000-01-01

    The Chandra X-Ray Observatory observed the Crab Nebula and pulsar during orbital calibration. Zeroth-order images with the High-Energy Transmission Grating (HETG) readout by the Advanced Charge Coupled Devices (CCD) Imaging Spectrometer spectroscopy array (ACIS-S) show a striking richness of X-ray structure at a resolution comparable to that of the best ground-based visible-light observations. The HETG-ACIS-S images reveal, for the first time, an X-ray inner ring within the X-ray torus, the suggestion of a hollow-tube structure for the torus, and X-ray knots along the inner ring and (perhaps) along the inward extension of the X-ray jet. Although complicated by instrumental effects and the brightness of the Crab Nebula, the spectrometric analysis shows systematic variations of the X-ray spectrum throughout the nebula.

  7. Discovery of Spatial and Spectral Structure in the X-Ray Emission from the Crab Nebula.

    Weisskopf; Hester; Tennant; Elsner; Schulz; Marshall; Karovska; Nichols; Swartz; Kolodziejczak; O'Dell

    2000-06-20

    The Chandra X-Ray Observatory observed the Crab Nebula and pulsar during orbital calibration. Zeroth-order images with the High-Energy Transmission Grating (HETG) readout by the Advanced CCD Imaging Spectrometer spectroscopy array (ACIS-S) show a striking richness of X-ray structure at a resolution comparable to that of the best ground-based visible-light observations. The HETG-ACIS-S images reveal, for the first time, an X-ray inner ring within the X-ray torus, the suggestion of a hollow-tube structure for the torus, and X-ray knots along the inner ring and (perhaps) along the inward extension of the X-ray jet. Although complicated by instrumental effects and the brightness of the Crab Nebula, the spectrometric analysis shows systematic variations of the X-ray spectrum throughout the nebula.

  8. Absolute spectrophotometry of the IC 2149, 4593, and NGC 6210 planetary nebulae in near infrared region

    Noskova, R.I.

    1976-01-01

    The absolute monochromatic energy flux (in ergs.cm -2 sec -1 ) was determined for the emission lines of the planetary nebulae IC2149, 4593 and NGC 6210 in the spectral interval lambda 6300-11000 A. The interstellar extinction Asub(β)=1.sup(m)3; O.sup(m)4; O.sup(m)6, accordingly, was estimated by using spectral lines HI of the Paschen and Balmer series. The energy distribution (in ergsxcm -2 xsec -1 1A -1 ) was found in summary continuous spectrum in the interval lambda 4000-10000 A. The attempt was made to separate the continuum of the nucleus and the nebula. The theoretical nebula continuous spectrum was calculated from lambda 3000 A to the radio range. The continuum, calibrated by menas of the flat part of the radiospectrum, linked well enough with the optical spectrum calculated here

  9. Interstellar and Solar Nebula Materials in Cometary Dust

    Messenger, Scott; Nakamura-Messenger, Keiko; Keller, Lindsay; Nguyen, Ann; Clemett, Simon

    2017-01-01

    Laboratory studies of cometary dust collected in the stratosphere and returned from comet 81P/Wild 2 by the Stardust spacecraft have revealed ancient interstellar grains and molecular cloud organic matter that record a range of astrophysical processes and the first steps of planetary formation. Presolar materials are rarer meteorites owing to high temperature processing in the solar nebula and hydrothermal alteration on their asteroidal parent bodies. The greater preservation of presolar materials in comets is attributed to their low accretion temperatures and limited planetary processing. Yet, comets also contain a large complement of high temperature materials from the inner Solar System. Owing to the limited and biased sampling of comets to date, the proportions of interstellar and Solar System materials within them remains highly uncertain. Interstellar materials are identified by coordinated isotopic, mineralogical, and chemical measurements at the scale of individual grains. Chondritic porous interplanetary dust particles (CP IDPs) that likely derive from comets are made up of 0.1 - 10 micron-sized silicates, Fe-Ni-sulfides, oxides, and other phases bound by organic material. As much as 1% of the silicates are interstellar grains that have exotic isotopic compositions imparted by nucleosynthetic processes in their parent stars. Crystalline silicates in CP IDPs dominantly have normal isotopic compositions and probably formed in the Solar System. 81P samples include isotopically normal refractory minerals that resemble Ca-Al rich inclusions and chondrules common in meteorites. The origins of sub-micron amorphous silicates in IDPs are not certain, but at least a few % of them are interstellar grains. The remainder have isotopic compositions consistent with Solar System origins and elemental compositions that are inconsistent with interstellar grain properties, thus favoring formation in the solar nebula [4]. The organic component in comets and primitive

  10. Rosette nebula globules: Seahorse giving birth to a star

    Mäkelä, M. M.; Haikala, L. K.; Gahm, G. F.

    2017-09-01

    Context. The Rosette nebula is an H II region ionized mainly by the stellar cluster NGC 2244. Elephant trunks, globules, and globulettes are seen at the interface where the H II region and the surrounding molecular shell meet. Aims: We have observed a field in the northwestern part of the Rosette nebula where we study the small globules protruding from the shell. Our aim is to measure their properties and study their star-formation history in continuation of our earlier study of the features of the region. Methods: We imaged the region in broadband near-infrared (NIR) JsHKs filters and narrowband H2 1-0 S(1), Pβ, and continuum filters using the SOFI camera at the ESO/NTT. The imaging was used to study the stellar population and surface brightness, create visual extinction maps, and locate star formation. Mid-infrared (MIR) Spitzer IRAC and WISE and optical NOT images were used to further study the star formation and the structure of the globules. The NIR and MIR observations indicate an outflow, which is confirmed with CO observations made with APEX. Results: The globules have mean number densities of 4.6 × 104 cm-3. Pβ is seen in absorption in the cores of the globules where we measure visual extinctions of 11-16 mag. The shell and the globules have bright rims in the observed bands. In the Ks band 20 to 40% of the emission is due to fluorescent emission in the 2.12 μmH2 line similar to the tiny dense globulettes we studied earlier in a nearby region. We identify several stellar NIR excess candidates and four of them are also detected in the Spitzer IRAC 8.0 μm image and studied further. We find an outflow with a cavity wall bright in the 2.124 μmH2 line and at 8.0 μm in one of the globules. The outflow originates from a Class I young stellar object (YSO) embedded deep inside the globule. An Hα image suggests the YSO drives a possible parsec-scale outflow. Despite the morphology of the globule, the outflow does not seem to run inside the dusty fingers

  11. Extended Structures of Planetary Nebulae Detected in H2 Emission

    Fang, Xuan; Zhang, Yong; Kwok, Sun; Hsia, Chih-Hao; Chau, Wayne; Ramos-Larios, Gerardo; Guerrero, Martín A.

    2018-06-01

    We present narrowband near-infrared images of a sample of 11 Galactic planetary nebulae (PNe) obtained in the H2 2.122 μm and Brγ 2.166 μm emission lines and the K c 2.218 μm continuum. These images were collected with the Wide-field Infrared Camera on the 3.6 m Canada–France–Hawaii Telescope (CFHT); their unprecedented depth and wide field of view allow us to find extended nebular structures in H2 emission in several PNe, some of these being the first detection. The nebular morphologies in H2 emission are studied in analogy with the optical images, and indication of stellar wind interactions is discussed. In particular, the complete structure of the highly asymmetric halo in NGC 6772 is witnessed in H2, which strongly suggests interaction with the interstellar medium. Our sample confirms the general correlation between H2 emission and the bipolarity of PNe. The knotty or filamentary fine structures of the H2 gas are resolved in the inner regions of several ring-like PNe, also confirming the previous argument that H2 emission mostly comes from knots or clumps embedded within fully ionized material at the equatorial regions. Moreover, the H2 image of the butterfly-shaped Sh 1-89, after removal of field stars, clearly reveals a tilted ring structure at the waist. These high-quality CFHT images justify follow-up detailed morphokinematic studies that are desired in order to deduce the true physical structures of a few PNe in the sample. Based on observations obtained with WIRCam, a joint project of CFHT, Taiwan, Korea, Canada, and France, at the Canada–France–Hawaii Telescope (CFHT), which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

  12. Dusty disks around central stars of planetary nebulae

    Clayton, Geoffrey C. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); De Marco, Orsola [Department of Physics and Astronomy, Macquarie University, Sydney, NSW 2109 (Australia); Nordhaus, Jason [Center for Computational Relativity and Gravitation, and National Technical Institute for the Deaf, Rochester Institute of Technology, Rochester, NY 14623 (United States); Green, Joel [Department of Astronomy, The University of Texas, 1 University Station, C1400, Austin, TX 78712-0259 (United States); Rauch, Thomas; Werner, Klaus [Institute for Astronomy and Astrophysics, Kepler Center for Astro and Particle Physics, Eberhard Karls University, Sand 1, D-72076 Tübingen (Germany); Chu, You-Hua, E-mail: gclayton@fenway.phys.lsu.edu, E-mail: orsola@science.mq.edu.au, E-mail: nordhaus@astro.rit.edu, E-mail: joel@astro.as.utexas.edu, E-mail: rauch@astro.uni-tuebingen.de, E-mail: werner@astro.uni-tuebingen.de, E-mail: chu@astro.uiuc.edu [Department of Astronomy, University of Illinois at Urbana-Champaign, 1002 West Green Street, Urbana, IL 61801 (United States)

    2014-06-01

    Only a few percent of cool, old white dwarfs (WDs) have infrared excesses interpreted as originating in small hot disks due to the infall and destruction of single asteroids that come within the star's Roche limit. Infrared excesses at 24 μm were also found to derive from the immediate vicinity of younger, hot WDs, most of which are still central stars of planetary nebulae (CSPNe). The incidence of CSPNe with this excess is 18%. The Helix CSPN, with a 24 μm excess, has been suggested to have a disk formed from collisions of Kuiper belt-like objects (KBOs). In this paper, we have analyzed an additional sample of CSPNe to look for similar infrared excesses. These CSPNe are all members of the PG 1159 class and were chosen because their immediate progenitors are known to often have dusty environments consistent with large dusty disks. We find that, overall, PG 1159 stars do not present such disks more often than other CSPNe, although the statistics (five objects) are poor. We then consider the entire sample of CSPNe with infrared excesses and compare it to the infrared properties of old WDs, as well as cooler post-asymptotic giant branch (AGB) stars. We conclude with the suggestion that the infrared properties of CSPNe more plausibly derive from AGB-formed disks rather than disks formed via the collision of KBOs, although the latter scenario cannot be ruled out. Finally, there seems to be an association between CSPNe with a 24 μm excess and confirmed or possible binarity of the central star.

  13. THE YOUNG INTERSTELLAR BUBBLE WITHIN THE ROSETTE NEBULA

    Bruhweiler, F. C.; Bourdin, M. O.; Freire Ferrero, R.; Gull, T. R.

    2010-01-01

    We use high-resolution International Ultraviolet Explorer (IUE) data and the interstellar (IS) features of highly ionized Si IV and C IV seen toward the young, bright OB stars of NGC 2244 in the core of the Rosette Nebula to study the physics of young IS bubbles. Two discrete velocity components in Si IV and C IV are seen toward stars in the 6.2 pc radius central cavity, while only a single velocity component is seen toward those stars in the surrounding H II region, at the perimeter and external to this cavity. The central region shows characteristics of a very young, windblown bubble. The shell around the central hot cavity is expanding at 56 km s -1 with respect to the embedded OB stars, while the surrounding H II region of the Rosette is expanding at ∼13 km s -1 . Even though these stars are quite young (∼2-4 Myr), both the radius and expansion velocity of the 6.2 pc inner shell point to a far younger age; t age ∼ 6.4 x 10 4 years. These results represent a strong contradiction to theory and present modeling, where much larger bubbles are predicted around individual O stars and O associations. Specifically, the results for this small bubble and its deduced age extend the 'missing wind luminosity problem' to young evolving bubbles. These results indicate that OB star winds mix the surrounding H II regions and the wind kinetic energy is converted to turbulence and radiated away in the dense H II regions. These winds do not form hot, adiabatically expanding cavities. True IS bubbles appear only to form at later evolutionary times, perhaps triggered by increased mass loss rates or discrete ejection events. Means for rectifying discrepancies between theory and observations are discussed.

  14. NEUTRON-CAPTURE ELEMENT ABUNDANCES IN MAGELLANIC CLOUD PLANETARY NEBULAE

    Mashburn, A. L.; Sterling, N. C. [Department of Physics, University of West Georgia, 1601 Maple Street, Carrollton, GA 30118 (United States); Madonna, S. [Instituto de Astrofísica de Canarias, Departamento Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife (Spain); Dinerstein, Harriet L. [Department of Astronomy, University of Texas, 2515 Speedway, C1400, Austin, TX 78712-1205 (United States); Roederer, I. U. [Department of Astronomy, University of Michigan, 1085 South University Avenue, Ann Arbor, MI 48109 (United States); Geballe, T. R., E-mail: awhite15@my.westga.edu, E-mail: nsterlin@westga.edu, E-mail: smadonna@iac.es, E-mail: harriet@astro.as.utexas.edu, E-mail: iur@umich.edu, E-mail: tgeballe@gemini.edu [Gemini Observatory, 670 N. A’ohoku Place, Hilo, HI 96720 (United States)

    2016-11-01

    We present near-infrared spectra of 10 planetary nebulae (PNe) in the Large and Small Magellanic Clouds (LMC and SMC), acquired with the FIRE and GNIRS spectrometers on the 6.5 m Baade and 8.1 m Gemini South Telescopes, respectively. We detect Se and/or Kr emission lines in eight of these objects, the first detections of n -capture elements in Magellanic Cloud PNe. Our abundance analysis shows large s -process enrichments of Kr (0.6–1.3 dex) in the six PNe in which it was detected, and Se is enriched by 0.5–0.9 dex in five objects. We also estimate upper limits to Rb and Cd abundances in these objects. Our abundance results for the LMC are consistent with the hypothesis that PNe with 2–3 M {sub ⊙} progenitors dominate the bright end of the PN luminosity function in young gas-rich galaxies. We find no significant correlations between s -process enrichments and other elemental abundances, central star temperature, or progenitor mass, though this is likely due to our small sample size. We determine S abundances from our spectra and find that [S/H] agrees with [Ar/H] to within 0.2 dex for most objects, but is lower than [O/H] by 0.2–0.4 dex in some PNe, possibly due to O enrichment via third dredge-up. Our results demonstrate that n -capture elements can be detected in PNe belonging to nearby galaxies with ground-based telescopes, allowing s -process enrichments to be studied in PN populations with well-determined distances.

  15. DIFFERENTIAL PROPER-MOTION MEASUREMENTS OF THE CYGNUS EGG NEBULA: THE PRESENCE OF EQUATORIAL OUTFLOWS

    Ueta, Toshiya; Tomasino, Rachael L. [Department of Physics and Astronomy, MS 6900, University of Denver, Denver, CO 80208 (United States); Ferguson, Brian A. [Space Telescope Science Institute, Baltimore, MD 21218 (United States)

    2013-08-01

    We present the results of differential proper-motion analyses of the Egg Nebula (RAFGL 2688, V1610 Cyg) based on the archived two-epoch optical data taken with the Hubble Space Telescope. First, we determined that the polarization characteristics of the Egg Nebula are influenced by the higher optical depth of the central regions of the nebula (i.e., the 'dustsphere' of {approx}10{sup 3} AU radius), causing the nebula to illuminate in two steps-the direct starlight is first channeled into bipolar cavities and then scattered off to the rest of the nebula. We then measured the amount of motion of local structures and the signature concentric arcs by determining their relative shifts over the 7.25 yr interval. Based on our analysis, which does not rely on the single-scattering assumption, we concluded that the lobes have been excavated by a linear expansion along the bipolar axis for the past {approx}400 yr, while the concentric arcs have been generated continuously and moving out radially at about 10 km s{sup -1} for the past {approx}5500 yr, and there appears to be a colatitudinally increasing trend in the radial expansion velocity field of the concentric arcs. Numerical investigations into the mass-loss modulation by the central binary system exist, which predict such a colatitudinally increasing expansion velocity field in the spiral-shock trails of the mass-loss ejecta. Therefore, the Egg Nebula may represent a rare edge-on case of the binary-modulated circumstellar environs, corroborating the previous theoretical predictions.

  16. The ionization structure of planetary nebulae 10: NGC 2392. Semiannual report

    Barker, T.

    1989-10-01

    Spectrophotometric observations of emission-line intensities over the spectral range 1400 to 7200 A were made in six positions in the planetary nebula NGC 2392. Standard equations used to correct for the existence of elements in other than the optically observable ionization stages give consistent results for the different positions that are in excellent agreement with abundances calculated using ultraviolet lines, and there is no evidence for any abundance gradient in the nebula. The logarithmic abundances agree well with determinations by Aller and Keyes

  17. Detection of C60 and C70 in a young planetary nebula.

    Cami, Jan; Bernard-Salas, Jeronimo; Peeters, Els; Malek, Sarah Elizabeth

    2010-09-03

    In recent decades, a number of molecules and diverse dust features have been identified by astronomical observations in various environments. Most of the dust that determines the physical and chemical characteristics of the interstellar medium is formed in the outflows of asymptotic giant branch stars and is further processed when these objects become planetary nebulae. We studied the environment of Tc 1, a peculiar planetary nebula whose infrared spectrum shows emission from cold and neutral C60 and C70. The two molecules amount to a few percent of the available cosmic carbon in this region. This finding indicates that if the conditions are right, fullerenes can and do form efficiently in space.

  18. The far-UV spectrum of the low-excitation planetary nebula HD 138403

    Surdej, Jean; Heck, A.

    1982-01-01

    Two high-resolution far-UV spectra of the low-excitation planetary nebula HD 138403 are analyzed which were obtained with the IUE satellite over the wavelength range from 1170 to 2070 A. It is shown that the nebula's far-UV spectrum comprises a stellar continuum on which are superimposed a few emission lines, numerous interstellar absorption lines, and various types of P Cygni profiles. Evidence is examined for substantial mass loss from the central nucleus, with terminal velocities of the or...

  19. The spectrophotometry and chemical composition of the oxygen-poor bipolar nebula NGC 6164-5

    Dufour, Reginald J.; Parker, Robert A. R.; Henize, Karl G.

    1988-01-01

    The paper presents new ground-based and IUE spectrophotometry of several positions in NGC 6164-5 surrounding the Population I Of star HD 148937. Electron temperatures, densities, and abundances are derived for the various positions in the nebula using spectral line information. For all of the regions observed, Ne/H is depleted by an amount comparable to O/H, while S/H and Ar/H have normal values. The results suggest that the nebula consists partly of material ejected from inner shell-burning regions of the Of star. In effect, HD 148937 is older and more advanced than what was previously thought.

  20. Spectrophotometry and chemical composition of the oxygen-poor bipolar nebula NGC 6164-5

    Dufour, R.J.; Parker, R.A.R.; Henize, K.G.

    1988-01-01

    The paper presents new ground-based and IUE spectrophotometry of several positions in NGC 6164-5 surrounding the Population I Of star HD 148937. Electron temperatures, densities, and abundances are derived for the various positions in the nebula using spectral line information. For all of the regions observed, Ne/H is depleted by an amount comparable to O/H, while S/H and Ar/H have normal values. The results suggest that the nebula consists partly of material ejected from inner shell-burning regions of the Of star. In effect, HD 148937 is older and more advanced than what was previously thought. 34 references

  1. Model nebulae and determination of the chemical composition of the Magellanic Clouds.

    Aller, L H; Keyes, C D; Czyzak, S J

    1979-04-01

    An analysis of previously presented photoelectric spectrophotometry of HII regions (emission-line diffuse nebulae) in the two Magellanic Clouds is carried out with the aid of theoretical nebular models, which are used primarily as interpolation devices. Some advantages and limitations of such theoretical models are discussed. A comparison of the finally obtained chemical compositions with those found by other observers shows generally a good agreement, suggesting that it is possible to obtain reliable chemical compositions from low excitation gaseous nebulae in our own galaxy as well as in distant stellar systems.

  2. Role of ionization fronts in the colliding wind model of planetary nebulae

    Giuliani, J.L. Jr.

    1981-01-01

    A similarity transformation is used to study the expansion of a planetary nebula which is driven by a fast stellar wind as well as an expanding H II region. The undisturbed gas is taken to be the remnant of a slow, red giant wind. The present analysis improves upon Kwok, Purton, and FitzGerald's colliding wind model for the formation of planetary nebulae since it includes the dynamical influence of ionization fronts, and calculates the variation of velocity and density within the flow

  3. Physical conditions within the poly-polar nebula NGC 6302. 3

    Barral, J F; Canto, J [Universidad Nacional Autonoma de Mexico, Mexico City; Meaburn, J; Walsh, J R [Manchester Univ. (UK). Dept of Astronomy

    1982-06-01

    IUE observations of the ultraviolet emission lines and continuum from the wind-driven poly-polar nebula NGC 6302 have been combined with those obtained of the visible emission lines to investigate the physical parameters of the ionized gas. Several relationships consolidate the view that this nebula is predominantly ionized radiatively by a very hot central star. However, the 'poly-polar' appearance and complex, high velocity flows of ionized material from the nebular core strongly suggest the presence of an energetic stellar wind from the central, but obscured star.

  4. The Emerging Population of Pulsar Wind Nebulae in Hard X-rays

    Mattana, F.; Götz, D.; Terrier, R.; Renaud, M.; Falanga, M.

    2009-05-01

    The hard X-ray synchrotron emission from Pulsar Wind Nebulae probes energetic particles, closely related to the pulsar injection power at the present time. INTEGRAL has disclosed the yet poorly known population of hard X-ray pulsar/PWN systems. We summarize the properties of the class, with emphasys on the first hard X-ray bow-shock (CTB 80 powered by PSR B1951+32), and highlight some prospects for the study of Pulsar Wind Nebulae with the Simbol-X mission.

  5. Search of a cyclotron line at 70 keV from Crab Nebula

    Ubertini, P.; Bazzano, A.; La Padula, C.D.; Polcaro, V.F.

    1980-01-01

    An observation of Crab Nebula was made during a transmediterranean balloon flight launched on August 26, 1979 from Milo Base (Sicily, Italy). The hard X-ray experiment (HXR 79) carried a payload consisting of two multiwire proportional counters having a geometric area of 900 cm 2 each. A single transit scan of the source was performed on the Crab Nebula region at a float altitude of 2.9 mbs. The preliminary results indicate the existence of an excess flux between 64 - 76 KeV above the expected value of Esup(-2.0) power law. (Auth.)

  6. Search of a cyclotron line at 70 keV from Crab Nebula

    Ubertini, P.; Bazzano, A.; La Padula, C.D.; Polcaro, V.F.

    1980-01-01

    An observation of Crab Nebula was made during a transmediterranean balloon flight launched on August 26, 1979 from Milo Base. The hard x-ray experiment carried a payload consisting of two multiwire proportional counters having a geometric area of 900 cm 2 each. A single transit scan of the source was performed on the Crab Nebula region at a float altitude of 2.9 mbs. The preliminary results indicate the existence of an excess flux between 64 - 76 keV above the expected value of Esup(-2.0) power law

  7. Ultraviolet observations of planetary nebulae NGC 6572, NGC 5315 and BD + 30/sup 0/ 3639

    Torres-Peimbert, S; Pena, M [Universidad Nacional Autonoma de Mexico, Mexico City. Inst. de Astronomia

    1981-01-01

    We present IUE observations of three planetary nebulae. We have obtained the chemical composition of NGC 6572 to be log C = -3.60, log N = -3.67, log O = -3.27, and log Ne = -3.8. For NGC 5315 and BD + 30/sup 0/ 3639, the stellar WR contribution in the UV is very significant, and for these nebulae we are only able to derive the carbon abundance. We found log C = -3.01 and >-3.27, respectively.

  8. Central Stars of Planetary Nebulae in the SMC

    Bianchi, Luciana

    2004-01-01

    In FUSE cycle 3's program C056 we studied four Central Stars of Planetary Nebulae (CSPN) in the Small Magellanic Could. All FUSE observations have been successfully completed and have been reduced and analyzed. The observation of one object (SMP SMC 5) appeared to be off-target and no useful stellar flux was gathered. For another observation (SMP SMC 1) the voltage problems resulted in the loss of data from one of the SiC detectors, but we were still able to analyze the remaining data. The analysis and the results are summarized below. The FUSE data were reduced using the latest available version of the FUSE calibration pipeline (CALFUSE v2.4). The flux of these SMC post-AGB objects is at the threshold of FUSE S sensitivity, and the targets required many orbit-long exposures, each of which typically had low (target) count-rates. The background subtraction required special care during the reduction, and was done in a similar manner to our FUSE cycle 2 BOO1 objects. The resulting calibrated data from the different channels were compared in the overlapping regions for consistency. The final combined, extracted spectra of each target was then modeled to determine the stellar and nebular parameters. The FUSE spectra, combined with archival HST spectra, have been analyzed using stellar atmospheres codes such as TLUSTY and CMFGEN to derive photospheric and wind parameters of the central stars, and with ISM models to determine the amount and temperature of the surrounding atomic and molecular hydrogen. We have combined these results with those of our cycle 4 (D034) program (CSPN of the LMC) in Herald & Bianchi 2004a (paper in preparation, will be submitted to ApJ in June 2004). Two of the three SMC objects analyzed were found to have significantly lower stellar temperatures than had been predicted using nebular photoionization models, indicating either a hotter ionizing companion or the existence of strong shocks in the nebular environment. The analysis also revealed that

  9. Molecular clouds in the North American and Pelican Nebulae: structures

    Zhang, Shaobo; Xu, Ye; Yang, Ji, E-mail: shbzhang@pmo.ac.cn [Purple Mountain Observatory, and Key Laboratory for Radio Astronomy, Chinese Academy of Sciences, Nanjing 210008 (China)

    2014-03-01

    We present observations of a 4.25 deg{sup 2} area toward the North American and Pelican Nebulae in the J = 1-0 transitions of {sup 12}CO, {sup 13}CO, and C{sup 18}O. Three molecules show different emission areas with their own distinct structures. These different density tracers reveal several dense clouds with a surface density of over 500 M {sub ☉} pc{sup –2} and a mean H{sub 2} column density of 5.8, 3.4, and 11.9 × 10{sup 21} cm{sup –2} for {sup 12}CO, {sup 13}CO, and C{sup 18}O, respectively. We obtain a total mass of 5.4 × 10{sup 4} M {sub ☉} ({sup 12}CO), 2.0 × 10{sup 4} M {sub ☉} ({sup 13}CO), and 6.1 × 10{sup 3} M {sub ☉} (C{sup 18}O) in the complex. The distribution of excitation temperature shows two phases of gas: cold gas (∼10 K) spreads across the whole cloud; warm gas (>20 K) outlines the edge of the cloud heated by the W80 H II region. The kinetic structure of the cloud indicates an expanding shell surrounding the ionized gas produced by the H II region. There are six discernible regions in the cloud: the Gulf of Mexico, Caribbean Islands and Sea, and Pelican's Beak, Hat, and Neck. The areas of {sup 13}CO emission range within 2-10 pc{sup 2} with mass of (1-5) × 10{sup 3} M {sub ☉} and line width of a few km s{sup –1}. The different line properties and signs of star-forming activity indicate they are in different evolutionary stages. Four filamentary structures with complicated velocity features are detected along the dark lane in LDN 935. Furthermore, a total of 611 molecular clumps within the {sup 13}CO tracing cloud are identified using the ClumpFind algorithm. The properties of the clumps suggest that most of the clumps are gravitationally bound and at an early stage of evolution with cold and dense molecular gas.

  10. CO self-shielding as the origin of oxygen isotope anomalies in the early solar nebula.

    Lyons, J R; Young, E D

    2005-05-19

    The abundances of oxygen isotopes in the most refractory mineral phases (calcium-aluminium-rich inclusions, CAIs) in meteorites have hitherto defied explanation. Most processes fractionate isotopes by nuclear mass; that is, 18O is twice as fractionated as 17O, relative to 16O. In CAIs 17O and 18O are nearly equally fractionated, implying a fundamentally different mechanism. The CAI data were originally interpreted as evidence for supernova input of pure 16O into the solar nebula, but the lack of a similar isotope trend in other elements argues against this explanation. A symmetry-dependent fractionation mechanism may have occurred in the inner solar nebula, but experimental evidence is lacking. Isotope-selective photodissociation of CO in the innermost solar nebula might explain the CAI data, but the high temperatures in this region would have rapidly erased the signature. Here we report time-dependent calculations of CO photodissociation in the cooler surface region of a turbulent nebula. If the surface were irradiated by a far-ultraviolet flux approximately 10(3) times that of the local interstellar medium (for example, owing to an O or B star within approximately 1 pc of the protosun), then substantial fractionation of the oxygen isotopes was possible on a timescale of approximately 10(5) years. We predict that similarly irradiated protoplanetary disks will have H2O enriched in 17O and 18O by several tens of per cent relative to CO.

  11. Spatially-Dependent Modelling of Pulsar Wind Nebula G0.9+0.1

    van Rensburg, C.; Krüger, P. P.; Venter, C.

    2018-03-01

    We present results from a leptonic emission code that models the spectral energy distribution of a pulsar wind nebula by solving a Fokker-Planck-type transport equation and calculating inverse Compton and synchrotron emissivities. We have created this time-dependent, multi-zone model to investigate changes in the particle spectrum as they traverse the pulsar wind nebula, by considering a time and spatially-dependent B-field, spatially-dependent bulk particle speed implying convection and adiabatic losses, diffusion, as well as radiative losses. Our code predicts the radiation spectrum at different positions in the nebula, yielding the surface brightness versus radius and the nebular size as function of energy. We compare our new model against more basic models using the observed spectrum of pulsar wind nebula G0.9+0.1, incorporating data from H.E.S.S. as well as radio and X-ray experiments. We show that simultaneously fitting the spectral energy distribution and the energy-dependent source size leads to more stringent constraints on several model parameters.

  12. A compact planetary nebula around the hot white dwarf EGB 6/PG 0950 + 139

    Liebert, J.; Green, R.; Bond, H.E.; Holberg, J.B.; Wesemael, F. (Steward Observatory, Tucson, AZ (USA) Mount Wilson and Las Campanas Observatories, Pasadena, CA (USA) Kitt Peak National Observatory, Tucson, AZ (USA) Space Telescope Science Institute, Baltimore, MD (USA) Arizona Univ., Tucson (USA) Montreal Universite, Montreal (Canada))

    1989-11-01

    The remarkable central star (0950 + 139), a very hot DA/DAO white dwarf, of the planetary nebula EGB 6 is described. Follow-up observations relevant to the analyses of both the nebula and the stellar photosphere are presented. Three kinds of scenarios are discussed to account for the existence of this peculiar nebula, but none appears very promising. The first consideration is that the nebula was ejected from the white dwarf as a discret event. This hypothesis is heavily constrained by the nebular size, density, and expansion rate; by the low luminosity and radius of the star; and by the absence of evidence for variation in density-sensitive forbidden lines from 1978 to 1987. No plausible mechanism can cause the observed amount of mass to be lost directly from a white dwarf in a steady or sporadic wind, at outflow velocities orders of magnitude below the escape velocity. Final consideration is given to the possibility that the gas is lost from a close companion star, but there is no evidence that this is a close binary system. 45 refs.

  13. The role of Fischer-Tropsch catalysis in solar nebula chemistry

    Kress, ME; Tielens, AGGM

    Fischer-Tropsch catalysis, the iron/nickel catalyzed conversion of CO and H(2) to hydrocarbons, would have been the only thermally-driven pathway available in the solar nebula to convert CO into other forms of carbon. A major issue in meteoritics is to determine the origin of meteoritic organics:

  14. A compact planetary nebula around the hot white dwarf EGB 6/PG 0950 + 139

    Liebert, James; Green, Richard; Bond, Howard E.; Holberg, J. B.; Wesemael, F.

    1989-01-01

    The remarkable central star (0950 + 139), a very hot DA/DAO white dwarf, of the planetary nebula EGB 6 is described. Follow-up observations relevant to the analyses of both the nebula and the stellar photosphere are presented. Three kinds of scenarios are discussed to account for the existence of this peculiar nebula, but none appears very promising. The first consideration is that the nebula was ejected from the white dwarf as a discret event. This hypothesis is heavily constrained by the nebular size, density, and expansion rate; by the low luminosity and radius of the star; and by the absence of evidence for variation in density-sensitive forbidden lines from 1978 to 1987. No plausible mechanism can cause the observed amount of mass to be lost directly from a white dwarf in a steady or sporadic wind, at outflow velocities orders of magnitude below the escape velocity. Final consideration is given to the possibility that the gas is lost from a close companion star, but there is no evidence that this is a close binary system.

  15. A compact planetary nebula around the hot white dwarf EGB 6/PG 0950 + 139

    Liebert, J.; Green, R.; Bond, H.E.; Holberg, J.B.; Wesemael, F.

    1989-01-01

    The remarkable central star (0950 + 139), a very hot DA/DAO white dwarf, of the planetary nebula EGB 6 is described. Follow-up observations relevant to the analyses of both the nebula and the stellar photosphere are presented. Three kinds of scenarios are discussed to account for the existence of this peculiar nebula, but none appears very promising. The first consideration is that the nebula was ejected from the white dwarf as a discret event. This hypothesis is heavily constrained by the nebular size, density, and expansion rate; by the low luminosity and radius of the star; and by the absence of evidence for variation in density-sensitive forbidden lines from 1978 to 1987. No plausible mechanism can cause the observed amount of mass to be lost directly from a white dwarf in a steady or sporadic wind, at outflow velocities orders of magnitude below the escape velocity. Final consideration is given to the possibility that the gas is lost from a close companion star, but there is no evidence that this is a close binary system. 45 refs

  16. RAPID GAMMA-RAY FLUX VARIABILITY DURING THE 2013 MARCH CRAB NEBULA FLARE

    Mayer, M.; Buehler, R.; Hays, E.; Cheung, C. C.; Grove, J. E.; Dutka, M. S.; Kerr, M.; Ojha, R.

    2013-01-01

    We report on a bright flare in the Crab Nebula detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The period of significantly increased luminosity occurred in 2013 March and lasted for approximately two weeks. During this period, we observed flux variability on timescales of approximately 5 hr. The combined photon flux above 100 MeV from the pulsar and its nebula reached a peak value of (12.5 ± 0.8) · 10 –6 cm –2 s –1 on 2013 March 6. This value exceeds the average flux by almost a factor of six and implies a ∼20 times higher flux for the synchrotron component of the nebula alone. This is the second brightest flare observed from this source. Spectral and temporal analysis of the LAT data collected during the outburst reveal a rapidly varying synchrotron component of the Crab Nebula while the pulsar emission remains constant in time

  17. Dynamos in asymptotic-giant-branch stars as the origin of magnetic fields shaping planetary nebulae.

    Blackman, E G; Frank, A; Markiel, J A; Thomas, J H; Van Horn, H M

    2001-01-25

    Planetary nebulae are thought to be formed when a slow wind from the progenitor giant star is overtaken by a subsequent fast wind generated as the star enters its white dwarf stage. A shock forms near the boundary between the winds, creating the relatively dense shell characteristic of a planetary nebula. A spherically symmetric wind will produce a spherically symmetric shell, yet over half of known planetary nebulae are not spherical; rather, they are elliptical or bipolar in shape. A magnetic field could launch and collimate a bipolar outflow, but the origin of such a field has hitherto been unclear, and some previous work has even suggested that a field could not be generated. Here we show that an asymptotic-giant-branch (AGB) star can indeed generate a strong magnetic field, having as its origin a dynamo at the interface between the rapidly rotating core and the more slowly rotating envelope of the star. The fields are strong enough to shape the bipolar outflows that produce the observed bipolar planetary nebulae. Magnetic braking of the stellar core during this process may also explain the puzzlingly slow rotation of most white dwarf stars.

  18. Chemical abundances and dust in planetary nebulae in the Galactic bulge

    Gutenkunst, S.; Bernard-Salas, J.; Pottasch, S. R.; Sloan, G. C.; Houck, J. R.

    2008-01-01

    We present mid-infrared Spitzer spectra of 11 planetary nebulae in the Galactic bulge. We derive argon, neon, sulfur, and oxygen abundances for them using mainly infrared line fluxes combined with some optical line fluxes from the literature. Due to the high extinction toward the bulge, the infrared

  19. DETAILED INTERSTELLAR POLARIMETRIC PROPERTIES OF THE PIPE NEBULA AT CORE SCALES

    Franco, G. A. P.; Alves, F. O.; Girart, J. M.

    2010-01-01

    We use R-band CCD linear polarimetry collected for about 12,000 background field stars in 46 fields of view toward the Pipe nebula to investigate the properties of the polarization across this dark cloud. Based on archival Two Micron All Sky Survey data, we estimate that the surveyed areas present total visual extinctions in the range 0.6 mag ≤ A V ≤ 4.6 mag. While the observed polarizations show a well-ordered large-scale pattern, with polarization vectors almost perpendicularly aligned to the cloud's long axis, at core scales one sees details that are characteristics of each core. Although many observed stars present degrees of polarization that are unusual for the common interstellar medium (ISM), our analysis suggests that the dust grains constituting the diffuse parts of the Pipe nebula seem to have the same properties as the normal Galactic ISM. Estimates of the second-order structure function of the polarization angles suggest that most of the Pipe nebula is magnetically dominated and that turbulence is sub-Alvenic. The Pipe nebula is certainly an interesting region to investigate the processes that prevailed during the initial phases of low-mass stellar formation.

  20. Revealing the velocity structure of the filamentary nebula in NGC 1275 in its entirety

    Gendron-Marsolais, M.; Hlavacek-Larrondo, J.; Martin, T. B.; Drissen, L.; McDonald, M.; Fabian, A. C.; Edge, A. C.; Hamer, S. L.; McNamara, B.; Morrison, G.

    2018-05-01

    We have produced for the first time a detailed velocity map of the giant filamentary nebula surrounding NGC 1275, the Perseus cluster's brightest galaxy, and revealed a previously unknown rich velocity structure across the entire nebula. These new observations were obtained with the optical imaging Fourier transform spectrometer SITELLE at CFHT. With its wide field of view (˜11'×11'), SITELLE is the only integral field unit spectroscopy instrument able to cover the 80 kpc×55 kpc (3.8'×2.6') large nebula in NGC 1275. Our analysis of these observations shows a smooth radial gradient of the [N II]λ6583/Hα line ratio, suggesting a change in the ionization mechanism and source across the nebula. The velocity map shows no visible general trend or rotation, indicating that filaments are not falling uniformly onto the galaxy, nor being uniformly pulled out from it. Comparison between the physical properties of the filaments and Hitomi measurements of the X-ray gas dynamics in Perseus are also explored.

  1. Probing the Molecular Outflows of the Coldest Known Object in the Universe: The Boomerang Nebula

    Sahai, Raghvendra; Vlemmings, W.; Nyman, L. A.; Huggins, P.

    2012-05-01

    The Boomerang Nebula is the coldest known object in the Universe, and an extreme member of the class of Pre-Planetary Nebulae, objects which represent a short-lived transitional phase between the AGB and Planetary Nebula evolutionary stages. The Boomerang's estimated prodigious mass-loss rate (0.001 solar masses/year) and low-luminosity (300 Lsun) lack an explanation in terms of current paradigms for dusty mass-loss and standard evolutionary theory of intermediate-mass stars. Single-dish CO J=1-0 observations (with a 45 arcsec beam) show that the high-speed outflow in this object has cooled to a temperature significantly below the temperature of the cosmic background radiation. We report on our high-resolution ALMA mapping of the CO lines in this ultra-cold nebula to determine the origin of these extreme conditions and robustly confirm current estimates of the fundamental physical properties of its ultra-cold outflow.

  2. THE NATURE AND FREQUENCY OF OUTFLOWS FROM STARS IN THE CENTRAL ORION NEBULA CLUSTER

    O’Dell, C. R. [Department of Physics and Astronomy, Vanderbilt University, Box 1807-B, Nashville, TN 37235 (United States); Ferland, G. J. [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506 (United States); Henney, W. J. [Instituto de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Apartado Postal 3-72, 58090 Morelia, Michoacán, México (Mexico); Peimbert, M. [Instituto de Astronomia, Universidad Nacional Autónoma de México, Apdo, Postal 70-264, 04510 México D. F., México (Mexico); García-Díaz, Ma. T. [Instituto de Astronomia, Universidad Nacional Autónoma de México, Km 103 Carretera Tijuana-Ensenada, 22860 Ensenada, B.C., México (Mexico); Rubin, Robert H., E-mail: cr.odell@vanderbilt.edu [NASA/Ames Research Center, Moffett Field, CA 94035-0001 (United States)

    2015-10-15

    Recent Hubble Space Telescope images have allowed the determination with unprecedented accuracy of motions and changes of shocks within the inner Orion Nebula. These originate from collimated outflows from very young stars, some within the ionized portion of the nebula and others within the host molecular cloud. We have doubled the number of Herbig–Haro objects known within the inner Orion Nebula. We find that the best-known Herbig–Haro shocks originate from relatively few stars, with the optically visible X-ray source COUP 666 driving many of them. While some isolated shocks are driven by single collimated outflows, many groups of shocks are the result of a single stellar source having jets oriented in multiple directions at similar times. This explains the feature that shocks aligned in opposite directions in the plane of the sky are usually blueshifted because the redshifted outflows pass into the optically thick photon-dominated region behind the nebula. There are two regions from which optical outflows originate for which there are no candidate sources in the SIMBAD database.

  3. Planetary nebula velocities in the disc and bulge of M31

    Halliday, C.; Carter, D.; Bridges, T. J.; Jackson, Z. C.; Wilkinson, M. I.; Quinn, D. P.; Evans, N. W.; Douglas, N. G.; Merrett, H. R.; Merrifield, M. R.; Romanowsky, A. J.; Kuijken, K.; Irwin, M. J.

    2006-01-01

    We present radial velocities for a sample of 723 planetary nebulae in the disc and bulge of M31, measured using the WYFFOS fibre spectrograph on the William Herschel Telescope. Velocities are determined using the [OIII] lambda 5007 emission line. Rotation and velocity dispersion are measured to a

  4. A HOT GAP AROUND JUPITER'S ORBIT IN THE SOLAR NEBULA

    Turner, N. J.; Choukroun, M.; Castillo-Rogez, J.; Bryden, G., E-mail: neal.turner@jpl.nasa.gov [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2012-04-01

    The Sun was an order of magnitude more luminous during the first few hundred thousand years of its existence, due in part to the gravitational energy released by material accreting from the solar nebula. If Jupiter was already near its present mass, the planet's tides opened an optically thin gap in the nebula. Using Monte Carlo radiative transfer calculations, we show that sunlight absorbed by the nebula and re-radiated into the gap raised temperatures well above the sublimation threshold for water ice, with potentially drastic consequences for the icy bodies in Jupiter's feeding zone. Bodies up to a meter in size were vaporized within a single orbit if the planet was near its present location during this early epoch. Dust particles lost their ice mantles, and planetesimals were partially to fully devolatilized, depending on their size. Scenarios in which Jupiter formed promptly, such as those involving a gravitational instability of the massive early nebula, must cope with the high temperatures. Enriching Jupiter in the noble gases through delivery trapped in clathrate hydrates will be more difficult, but might be achieved by either forming the planet much farther from the star or capturing planetesimals at later epochs. The hot gap resulting from an early origin for Jupiter also would affect the surface compositions of any primordial Trojan asteroids.

  5. The Eighty Six Hα Spectra from the Orion Nebula (M42, Sh2-281)

    ∼40′×40′) of the Orion Nebula (NGC1976, M42, Sh2-281) have been obtained using DEFPOS spectrometer with a circular field of view of 4′ at TUBITAK National Observatory (TUG, Antalya, Turkey). Measurements provide information ...

  6. The high energy x-ray spectrum of the Crab Nebula observed from OSO 8

    Dolan, J.F.; Crannell, L.J.; Dennis, B.R.; Orwig, L.E.; Maurer, G.S.

    1977-01-01

    The X-ray spectrum of the Crab Nebula was measured with the scintillation spectrometer on board the OSO-8 satellite. The total emission of the X-ray source shows no long term variability. The spectrum itself can be described by a single power law out to energies of at least 500 keV

  7. Abundances in planetary nebulae: NGC 1535, NGC 6629, He2-108, and Tc1

    Pottasch, S. R.; Surendiranath, R.; Bernard-Salas, J.

    Context. Models have been made of stars of a given mass that produce planetary nebulae that usually begin on the AGB (although they may begin earlier) and run to the white dwarf stage. While these models cover the so-called dredge-up phases when nuclear reactions occur and the newly formed products

  8. Abundances in planetary nebulae near the galactic centre .1. Abundance determinations

    Ratag, MA; Pottasch, [No Value; Dennefeld, M; Menzies, J

    1997-01-01

    Abundance determinations of about 110 planetary nebulae, which are likely to be in the Galactic Bulge are presented. Plasma diagnostics have been performed by making use of the available forbidden line ratios combined with radio continuum measurements. Chemical abundances of He, O, N, Ne, S, Ar, and

  9. Abundances in planetary nebulae : NGC1535, NGC6629, He2-108, and Tc1

    Pottasch, S. R.; Surendiranath, R.; Bernard-Salas, J.

    Context. Models have been made of stars of a given mass that produce planetary nebulae that usually begin on the AGB (although they may begin earlier) and run to the white dwarf stage. While these models cover the so-called dredge-up phases when nuclear reactions occur and the newly formed products

  10. An Application-Based Performance Evaluation of NASAs Nebula Cloud Computing Platform

    Saini, Subhash; Heistand, Steve; Jin, Haoqiang; Chang, Johnny; Hood, Robert T.; Mehrotra, Piyush; Biswas, Rupak

    2012-01-01

    The high performance computing (HPC) community has shown tremendous interest in exploring cloud computing as it promises high potential. In this paper, we examine the feasibility, performance, and scalability of production quality scientific and engineering applications of interest to NASA on NASA's cloud computing platform, called Nebula, hosted at Ames Research Center. This work represents the comprehensive evaluation of Nebula using NUTTCP, HPCC, NPB, I/O, and MPI function benchmarks as well as four applications representative of the NASA HPC workload. Specifically, we compare Nebula performance on some of these benchmarks and applications to that of NASA s Pleiades supercomputer, a traditional HPC system. We also investigate the impact of virtIO and jumbo frames on interconnect performance. Overall results indicate that on Nebula (i) virtIO and jumbo frames improve network bandwidth by a factor of 5x, (ii) there is a significant virtualization layer overhead of about 10% to 25%, (iii) write performance is lower by a factor of 25x, (iv) latency for short MPI messages is very high, and (v) overall performance is 15% to 48% lower than that on Pleiades for NASA HPC applications. We also comment on the usability of the cloud platform.

  11. High-speed knots in the hourglass shaped planetary nebula Hubble 12

    Vaytet, N. M. H.; Rushton, A. P.; Lloyd, M.

    2009-01-01

    We present a detailed kinematical analysis of the young compact hourglass-shaped planetary nebula Hb 12. We performed optical imaging and longslit spectroscopy of Hb 12 using the Manchester echelle spectrometer with the 2.1m San Pedro Martir telescope. We reveal, for the first time, the presence...

  12. Central star of NGC 1360: a spectroscopic binary within a planetary nebula

    Mendez, R H; Niemela, V S [Instituto de Astronomia y Fisica del Espacio, Buenos Aires (Argentina)

    1977-02-01

    CPD - 26/sup 0/389, a hot subdwarf at the centre of the planetary nebula NGC 1360, is shown to be a single-lined spectroscopic binary with a period of about 8 day. The primary (visible) component appears to be less massive than its companion, and the total stellar mass of the system is presumably below one solar mass.

  13. Discovery of a parsec-scale bipolar nebula around MWC 349A

    Gvaramadze, V. V.; Menten, K. M.

    2012-05-01

    We report the discovery of a bipolar nebula around the peculiar emission-line star MWC 349A using archival Spitzer Space Telescope 24 μm data. The nebula extends over several arcminutes (up to 5 pc) and has the same orientation and geometry as the well-known subarcsecond-scale (~400 times smaller) bipolar radio nebula associated with this star. We discuss the physical relationship between MWC 349A and the nearby B0 III star MWC 349B and propose that both stars were members of a hierarchical triple system, which was ejected from the core of the Cyg OB2 association several Myr ago and recently was dissolved into a binary system (now MWC 349A) and a single unbound star (MWC 349B). Our proposal implies that MWC 349A is an evolved massive star (likely a luminous blue variable) in a binary system with a low-mass star. A possible origin of the bipolar nebula around MWC 349A is discussed.

  14. Discovery of powerful gamma-ray flares from the Crab Nebula.

    Tavani, M; Bulgarelli, A; Vittorini, V; Pellizzoni, A; Striani, E; Caraveo, P; Weisskopf, M C; Tennant, A; Pucella, G; Trois, A; Costa, E; Evangelista, Y; Pittori, C; Verrecchia, F; Del Monte, E; Campana, R; Pilia, M; De Luca, A; Donnarumma, I; Horns, D; Ferrigno, C; Heinke, C O; Trifoglio, M; Gianotti, F; Vercellone, S; Argan, A; Barbiellini, G; Cattaneo, P W; Chen, A W; Contessi, T; D'Ammando, F; DePris, G; Di Cocco, G; Di Persio, G; Feroci, M; Ferrari, A; Galli, M; Giuliani, A; Giusti, M; Labanti, C; Lapshov, I; Lazzarotto, F; Lipari, P; Longo, F; Fuschino, F; Marisaldi, M; Mereghetti, S; Morelli, E; Moretti, E; Morselli, A; Pacciani, L; Perotti, F; Piano, G; Picozza, P; Prest, M; Rapisarda, M; Rappoldi, A; Rubini, A; Sabatini, S; Soffitta, P; Vallazza, E; Zambra, A; Zanello, D; Lucarelli, F; Santolamazza, P; Giommi, P; Salotti, L; Bignami, G F

    2011-02-11

    The well-known Crab Nebula is at the center of the SN1054 supernova remnant. It consists of a rotationally powered pulsar interacting with a surrounding nebula through a relativistic particle wind. The emissions originating from the pulsar and nebula have been considered to be essentially stable. Here, we report the detection of strong gamma-ray (100 mega-electron volts to 10 giga-electron volts) flares observed by the AGILE satellite in September 2010 and October 2007. In both cases, the total gamma-ray flux increased by a factor of three compared with the non-flaring flux. The flare luminosity and short time scale favor an origin near the pulsar, and we discuss Chandra Observatory x-ray and Hubble Space Telescope optical follow-up observations of the nebula. Our observations challenge standard models of nebular emission and require power-law acceleration by shock-driven plasma wave turbulence within an approximately 1-day time scale.

  15. THE NATURE AND FREQUENCY OF OUTFLOWS FROM STARS IN THE CENTRAL ORION NEBULA CLUSTER

    O’Dell, C. R.; Ferland, G. J.; Henney, W. J.; Peimbert, M.; García-Díaz, Ma. T.; Rubin, Robert H.

    2015-01-01

    Recent Hubble Space Telescope images have allowed the determination with unprecedented accuracy of motions and changes of shocks within the inner Orion Nebula. These originate from collimated outflows from very young stars, some within the ionized portion of the nebula and others within the host molecular cloud. We have doubled the number of Herbig–Haro objects known within the inner Orion Nebula. We find that the best-known Herbig–Haro shocks originate from relatively few stars, with the optically visible X-ray source COUP 666 driving many of them. While some isolated shocks are driven by single collimated outflows, many groups of shocks are the result of a single stellar source having jets oriented in multiple directions at similar times. This explains the feature that shocks aligned in opposite directions in the plane of the sky are usually blueshifted because the redshifted outflows pass into the optically thick photon-dominated region behind the nebula. There are two regions from which optical outflows originate for which there are no candidate sources in the SIMBAD database

  16. THE [O III] NEBULA OF THE MERGER REMNANT NGC 7252: A LIKELY FAINT IONIZATION ECHO

    Schweizer, François; Kelson, Daniel D.; Villanueva, Edward V.; Seitzer, Patrick; Walth, Gregory L.

    2013-01-01

    We present images and spectra of a ∼10 kpc-sized emission-line nebulosity discovered in the prototypical merger remnant NGC 7252 and dubbed the ''[O III] nebula'' because of its dominant [O III] λ5007 line. This nebula seems to yield the first sign of episodic active galactic nucleus (AGN) activity still occurring in the remnant, ∼220 Myr after the coalescence of two gas-rich galaxies. Its location and kinematics suggest it belongs to a stream of tidal-tail gas falling back into the remnant. Its integrated [O III] λ5007 luminosity is 1.4 × 10 40 erg s –1 , and its spectrum features some high-excitation lines, including He II λ4686. In diagnostic line-ratio diagrams, the nebula lies in the domain of Seyfert galaxies, suggesting that it is photoionized by a source with a power-law spectrum. Yet, a search for AGN activity in NGC 7252 from X-rays to radio wavelengths yields no detection, with the most stringent upper limit set by X-ray observations. The upper luminosity limit of L 2-10 k eV,0 39 erg s –1 estimated for the nucleus is ∼10 3 times lower than the minimum ionizing luminosity of ∼> 5 × 10 42 erg s –1 necessary to excite the nebula. This large discrepancy suggests that the nebula is a faint ionization echo excited by a mildly active nucleus that has declined by ∼3 orders of magnitude over the past 20,000-200,000 yr. In many ways this nebula resembles the prototypical ''Hanny's Voorwerp'' near IC 2497, but its size is 3× smaller and its [O III] luminosity ∼100× lower. We propose that it be classified as an extended emission-line region (EELR). The [O III] nebula is then the lowest-luminosity ionization echo and EELR discovered so far, indicative of recent, probably sputtering AGN activity of Seyfert-like intensity in NGC 7252

  17. The planetary nebula IPHASXJ211420.0+434136 (Ou5): insights into common-envelope dynamical and chemical evolution

    Corradi, R. L. M.; Rodriguez-Gil, P.; Jones, D.; Garcia-Rojas, J.; Mampaso, A.; Garcia-Alvarez, D.; Pursimo, T.; Eenmäe, T.; Liimets, T.; Miszalski, B.

    2014-01-01

    While analysing the images of the IPHAS H$\\alpha$ survey, we noticed that the central star of the candidate planetary nebula IPHASXJ211420.0+434136 (also named Ou5) was clearly variable. This is generally considered as an indication of binarity. To confirm it, we performed a photometric monitoring of the central star, and obtained images and spectra of the nebula. The nebular spectrum confirms that IPHASXJ211420.0+434136 is a planetary nebula of moderately high excitation. It has a remarkable...

  18. Hard x-ray to low energy gamma ray spectrum of the Crab Nebula

    Jung, G.V.

    1986-01-01

    The spectrum of the Crab Nebula has been determined in the energy range 10 keV to 5 MeV from the data of the UCSD/MIT Hard-X-ray and Low Energy Gamma Ray Experiment on the first High Energy Astronomy Observatory, HEAO-1. The x-ray to γ-ray portion of the continuous emission from the Crab is indicative of the electron spectrum, its transport through the nebula, and the physical conditions near the shocked interface between the nebular region and the wind which is the physical link between the nebula and the pulsar, NP0532. The power-law dependence of the spectrum found in the lower-energy decade of this observation (10 to 100 keV) is not continued without modification to higher energies. Evidence for this has been accumulating from previous observations in the γ-ray ranges of 1-10 MeV and above 35 MeV. The observations on which this dissertation is based further characterize the spectral change in the 100 keV to 1 MeV region. These observations provide a crucial connection between the x-ray and γ-ray spectrum of the non-pulsed emission of the Crab Nebula. The continuity of this spectrum suggests that the emission mechanism responsible for the non-pulsed γ-rays observed above 35 MeV is of the same origin as the emission at lower energies, i.e. that of synchrotron radiation in the magnetic field of the nebula

  19. GLOBAL MODELING OF NEBULAE WITH PARTICLE GROWTH, DRIFT, AND EVAPORATION FRONTS. I. METHODOLOGY AND TYPICAL RESULTS

    Estrada, Paul R. [Carl Sagan Center, SETI Institute, 189 N. Bernardo Avenue # 100, Mountain View, CA 94043 (United States); Cuzzi, Jeffrey N. [Ames Research Center, NASA, Mail Stop 245-3, Moffett Field, CA 94035 (United States); Morgan, Demitri A., E-mail: Paul.R.Estrada@nasa.gov [USRA, NASA Ames Research Center, Mail Stop 245-3, Moffett Field, CA 94035 (United States)

    2016-02-20

    We model particle growth in a turbulent, viscously evolving protoplanetary nebula, incorporating sticking, bouncing, fragmentation, and mass transfer at high speeds. We treat small particles using a moments method and large particles using a traditional histogram binning, including a probability distribution function of collisional velocities. The fragmentation strength of the particles depends on their composition (icy aggregates are stronger than silicate aggregates). The particle opacity, which controls the nebula thermal structure, evolves as particles grow and mass redistributes. While growing, particles drift radially due to nebula headwind drag. Particles of different compositions evaporate at “evaporation fronts” (EFs) where the midplane temperature exceeds their respective evaporation temperatures. We track the vapor and solid phases of each component, accounting for advection and radial and vertical diffusion. We present characteristic results in evolutions lasting 2 × 10{sup 5} years. In general, (1) mass is transferred from the outer to the inner nebula in significant amounts, creating radial concentrations of solids at EFs; (2) particle sizes are limited by a combination of fragmentation, bouncing, and drift; (3) “lucky” large particles never represent a significant amount of mass; and (4) restricted radial zones just outside each EF become compositionally enriched in the associated volatiles. We point out implications for millimeter to submillimeter SEDs and the inference of nebula mass, radial banding, the role of opacity on new mechanisms for generating turbulence, the enrichment of meteorites in heavy oxygen isotopes, variable and nonsolar redox conditions, the primary accretion of silicate and icy planetesimals, and the makeup of Jupiter’s core.

  20. GLOBAL MODELING OF NEBULAE WITH PARTICLE GROWTH, DRIFT, AND EVAPORATION FRONTS. I. METHODOLOGY AND TYPICAL RESULTS

    Estrada, Paul R.; Cuzzi, Jeffrey N.; Morgan, Demitri A.

    2016-01-01

    We model particle growth in a turbulent, viscously evolving protoplanetary nebula, incorporating sticking, bouncing, fragmentation, and mass transfer at high speeds. We treat small particles using a moments method and large particles using a traditional histogram binning, including a probability distribution function of collisional velocities. The fragmentation strength of the particles depends on their composition (icy aggregates are stronger than silicate aggregates). The particle opacity, which controls the nebula thermal structure, evolves as particles grow and mass redistributes. While growing, particles drift radially due to nebula headwind drag. Particles of different compositions evaporate at “evaporation fronts” (EFs) where the midplane temperature exceeds their respective evaporation temperatures. We track the vapor and solid phases of each component, accounting for advection and radial and vertical diffusion. We present characteristic results in evolutions lasting 2 × 10 5 years. In general, (1) mass is transferred from the outer to the inner nebula in significant amounts, creating radial concentrations of solids at EFs; (2) particle sizes are limited by a combination of fragmentation, bouncing, and drift; (3) “lucky” large particles never represent a significant amount of mass; and (4) restricted radial zones just outside each EF become compositionally enriched in the associated volatiles. We point out implications for millimeter to submillimeter SEDs and the inference of nebula mass, radial banding, the role of opacity on new mechanisms for generating turbulence, the enrichment of meteorites in heavy oxygen isotopes, variable and nonsolar redox conditions, the primary accretion of silicate and icy planetesimals, and the makeup of Jupiter’s core

  1. Fermi-LAT Constraints on the Pulsar Wind Nebula Nature of HESS J1857+026

    Rousseau, R.; Grondin, M.-H.; VanEtten, A.; Lemoine-Goumard, M.; Bogdanov, S.; Hessels, J. W. T.; Kaspi, V. M.; Arzoumanian, Z.; Camilo, F.; Casandjian, J. M.; hide

    2012-01-01

    Since its launch, the Fermi satellite has firmly identified 5 pulsar wind nebulae plus a large number of candidates, all powered by young and energetic pulsars. HESS J1857+026 is a spatially extended gamma-ray source detected by H.E.S.S. and classified as a possible pulsar wind nebula candidate powered by PSR J1856+0245. Aims. We search for -ray pulsations from PSR J1856+0245 and explore the characteristics of its associated pulsar wind nebula. Methods. Using a rotational ephemeris obtained from the Lovell telescope at Jodrell Bank Observatory at 1.5 GHz, we phase.fold 36 months of gamma-ray data acquired by the Large Area Telescope (LAT) aboard Fermi. We also perform a complete gamma-ray spectral and morphological analysis. Results. No pulsation was detected from PSR J1856+0245. However, significant emission is detected at a position coincident with the TeV source HESS J1857+026. The gamma-ray spectrum is well described by a simple power law with a spectral index of Gamma = 1.53 +/- 0.11(sub stat) +/- 0.55(sub syst) and an energy flux of G(0.1 C100 GeV) = (2.71 +/- 0.52(sub stat) +/- 1.51(sub syst) X 10(exp -11) ergs/ sq cm/s. This implies a gamma.ray efficiency of approx 5 %, assuming a distance of 9 kpc, the gamma-ray luminosity of L(sub gamma) (sub PWN) (0.1 C100 GeV) = (2.5 +/- 0.5(sub stat) +/- 1.5(sub syst)) X 10(exp 35)(d/(9kpc))(exp 2) ergs/s and E-dot = 4.6 X 10(exp 36) erg /s, in the range expected for pulsar wind nebulae. Detailed multi-wavelength modeling provides new constraints on its pulsar wind nebula nature.

  2. Millimeter observations of CS, HCO{sup +}, and CO toward five planetary nebulae: following molecular abundances with nebular age

    Edwards, J. L.; Ziurys, L. M. [Department of Chemistry, The University of Arizona, P.O. Box 210041, Tucson, AZ 85721 (United States); Cox, E. G., E-mail: lziurys@email.arizona.edu [Department of Astronomy and Steward Observatory, Arizona Radio Observatory, The University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

    2014-08-20

    Millimeter and sub-millimeter observations of CO, CS, and HCO{sup +} have been conducted toward five planetary nebulae (PNe: K4-47, NGC 6537 (Red Spider), M2-48, NGC 6720 (Ring), and NGC 6853 (Dumbbell)), spanning an age range of 900-10,000 yr, using the Sub-Millimeter Telescope and the 12 m antenna of the Arizona Radio Observatory. The J = 5 → 4, J = 3 → 2, and J = 2 → 1 transitions of CS at 245, 147, and 98 GHz, as well as the J = 3 → 2 and J = 1 → 0 lines of HCO{sup +} at 268 and 89 GHz, were detected toward each source. At least three rotational transitions of CO have also been observed, including the J = 6 → 5 and J = 4 → 3 lines at 691 and 461 GHz. CS had not been definitively identified previously in PNe, and new detections of HCO{sup +} were made in four of the five nebulae. From a radiative transfer analysis of the CO and CS data, kinetic temperatures of T {sub K} ∼ 10-80 K and gas densities of n(H{sub 2}) ∼ 0.1-1 × 10{sup 6} cm{sup –3} were determined for the molecular material in these sources. Column densities for CO, CS, and HCO{sup +} were N {sub tot} ∼ 0.2-5 × 10{sup 16} cm{sup –2}, N {sub tot} ∼ 0.4-9 × 10{sup 12} cm{sup –2}, and N {sub tot} ∼ 0.3-5 × 10{sup 12} cm{sup –2}, respectively, with fractional abundances, relative to H{sub 2}, of f ∼ 0.4-2 × 10{sup –4}, f ∼ 1-4 × 10{sup –8}, and f ∼ 1 × 10{sup –8}, with the exception of M2-48, which had f(HCO{sup +}) ∼ 10{sup –7}. Overall, the molecular abundances do not significantly vary over a duration of 10,000 yr, in contrast to predictions of chemical models. The abundances reflect the remnant asymptotic giant branch shell material, coupled with photochemistry in the early PN phase. These observations also suggest that PNe eject substantial amounts of molecular material into the diffuse interstellar medium.

  3. Cu and Zn Isotopes as New Tracers of Early Solar Nebula and Asteroidal processes

    LUCK, J.; BEN OTHMAN, D.; ALBAREDE, F.

    2001-12-01

    experiments have been conducted on various powder aliquots : HF-HCl cold(#1), HF-HCl hot(#2), HF-HNO3(#3) hot under pressure. Results show clearly that different Zn (and Cu) isotopic signatures (are preserved in early components. We stress that these are NOT anomalies for Zn : three isotopic ratios (66, 67 and 68 vs. 64) agree perfectly with a mass-dependent process. In particular Zn gets systematically lighter from the ``volatile" compounds (#1) to the refractory ones (#3). The rough correlation between O and Zn isotopes in these compounds could imply that Zinc, like Oxygen, experienced interaction between gaseous and solid states (e.g. spinels) at high temperatures. III- Iron Meteorites Non magmatic irons do not show much variation (less than 1 permil in range for both elements). On the other hand, meteorites from the IAB-IIICD group show not only large variations (3.5 permil in Zn), but also a negative correlation between Cu and Zn isotopes : this could be interpreted as a mixing between two endmembers, one of them being strongly fractionated in Zn isotopes. Fractionation of such extent (+3.7 permil) could reflect either volatilization during impact melting, or alteration on the parent body. Data available indicate that Cu and Zn isotopes are potentially important tracers for studying : 1- early solar nebula processes (e.g. high and low-T compounds exhibit different isotopic signatures); 2- meteorite parent body evolution (e.g. Cu and Zn isotopes correlate remarkably well with Oxygen isotopes in a well-established order : CV-CO-CM-CI). References (1)\\x90Marechal C., Telouk P. and Albarede F. (1999) Chem. Geol., 156, 251-273.

  4. Transformation of Graphitic and Amorphous Carbon Dust to Complex Organic Molecules in a Massive Carbon Cycle in Protostellar Nebulae

    Nuth, Joseph A., III; Johnson, Natasha M.

    2012-01-01

    More than 95% of silicate minerals and other oxides found in meteorites were melted, or vaporized and recondensed in the Solar Nebula prior to their incorporation into meteorite parent bodies. Gravitational accretion energy and heating via radioactive decay further transformed oxide minerals accreted into planetesimals. In such an oxygen-rich environment the carbonaceous dust that fell into the nebula as an intimate mixture with oxide grains should have been almost completely converted to CO. While some pre-collapse, molecular-cloud carbonaceous dust does survive, much in the same manner as do pre-solar oxide grains, such materials constitute only a few percent of meteoritic carbon and are clearly distinguished by elevated D/H, N-15/N-16, C-13/C-12 ratios or noble gas patterns. Carbonaceous Dust in Meteorites: We argue that nearly all of the carbon in meteorites was synthesized in the Solar Nebula from CO and that this CO was generated by the reaction of carbonaceous dust with solid oxides, water or OH. It is probable that some fraction of carbonaceous dust that is newly synthesized in the Solar Nebula is also converted back into CO by additional thermal processing. CO processing might occur on grains in the outer nebula through irradiation of CO-containing ice coatings or in the inner nebula via Fischer-Tropsch type (FTT) reactions on grain surfaces. Large-scale transport of both gaseous reaction products and dust from the inner nebula out to regions where comets formed would spread newly formed carbonaceous materials throughout the solar nebula. Formation of Organic Carbon: Carbon dust in the ISM might easily be described as inorganic graphite or amorphous carbon, with relatively low structural abundances of H, N, O and S . Products of FTT reactions or organics produced via irradiation of icy grains contain abundant aromatic and aliphatic hydrocarbons. aldehydes, keytones, acids, amines and amides.. The net result of the massive nebular carbon cycle is to convert

  5. Search for gamma ray emission above 20 MeV from the Crab nebula and the NP 0532 pulsar

    Leray, J.-P.

    1976-08-01

    The search for gamma-ray emission above 20 MeV from the Crab Nebula and Pulsar NP 0532 was undertaken. A critical analysis of the detector is presented together with a study of the background. The observed flux from the sources are compared with a theoretical model for the gamma-ray emission bases on the synchrotron process in the Crab Nebula and Pulsar NP 0532 [fr

  6. Challenging Narcissus, or Reflecting on Reflecting.

    Achilles, C. M.

    The concept of reflective practice and teaching people to be reflective practitioners is examined. The document begins with a look at professional knowledge according to three prominent professionals in the educational administration field: Schon, Schein, and Achilles. "Reflective" strategies that could be incorporated into courses and…

  7. X-ray observations of two lunar occultations of the Crab Nebula

    Ku, W.H.M.

    1976-01-01

    The x-ray source in the Crab nebula was observed during two lunar occultations. The combined results of the two scans of the nebula indicate that the spatial distribution of the X-ray flux from the nebula is centered on a region 10'' to 15'' NW of the pulsar. The half-intensity size, as measured by the FWHM of the best Gaussian representation of each strip flux distribution, is 46.7'' +- 1.5'' along p.a. = 300 0 , and is 42'' +- 2'' along p.a. = 255 0 . A closer examination of the size of the nebular emission region measured along p.a. = 300 0 reveals that the size decreases significantly with increasing photon energy. A power-law function with an exponent of γ = -0.148 +- 0.012 characterizes the optical (approximately 2 eV) to X-ray (approximately 50 keV) size measurements well, but it fails to predict the observed sizes of the radio nebula. Power-law spectral indices derived for different regions of the nebula support this finding. These results are interpreted in terms of existing theoretical models for the motion of electrons in the nebula. The data obtained on 28 December 1974 also provide strong evidence for the existence of a low-luminosity soft X-ray component more than 60'' W of the pulsar. Such emission was not detected in data from the first scan, but the upper limit derived from those data is consistent with the existence of a soft extended source. Several plausible explanations for the origin of this radiation are considered including the interesting possibility of thermal emission from a supernova remnant shell. Data obtained near the time of emergence of the pulsar for both observations are examined for possible flux contribution from a discrete steady radiation source. The null result allows an upper limit of 4.7 x 10 6 0 K (99 percent confidence) to be established on the surface temperature of the neutron star associated with NP 0532. This result is used to set limits on some physical parameters of a neutron star

  8. Nature versus nurture: Luminous blue variable nebulae in and near massive stellar clusters at the galactic center

    Lau, R. M.; Herter, T. L.; Adams, J. D.; Morris, M. R.

    2014-01-01

    Three luminous blue variables (LBVs) are located in and near the Quintuplet Cluster at the Galactic center: the Pistol Star, G0.120-0.048, and qF362. We present imaging at 19, 25, 31, and 37 μm of the region containing these three LBVs, obtained with SOFIA using FORCAST. We argue that Pistol and G0.120-0.048 are identical 'twins' that exhibit contrasting nebulae due to the external influence of their different environments. Our images reveal the asymmetric, compressed shell of hot dust surrounding the Pistol Star and provide the first detection of the thermal emission from the symmetric, hot dust envelope surrounding G0.120-0.048. However, no detection of hot dust associated with qF362 is made. Dust and gas composing the Pistol nebula are primarily heated and ionized by the nearby Quintuplet Cluster stars. The northern region of the Pistol nebula is decelerated due to the interaction with the high-velocity (2000 km s –1 ) winds from adjacent Wolf-Rayet Carbon (WC) stars. From fits to the spectral energy distribution (SED) of the Pistol nebula with the DustEM code we determine that the Pistol nebula is composed of a distribution of very small, transiently heated grains (10 to ∼ 35 Å) having a total dust mass of 0.03 M ☉ , and that it exhibits a gradient of decreasing grain size from south to north due to differential sputtering by the winds from the WC stars. The total IR luminosity of the Pistol nebula is 5.2 × 10 5 L ☉ . Dust in the G0.120-0.048 nebula is primarily heated by the central star; however, the nebular gas is ionized externally by the Arches Cluster. Unlike the Pistol nebula, the G0.120-0.048 nebula is freely expanding into the surrounding medium. A grain size distribution identical to that of the non-sputtered region of the Pistol nebula satisfies the constraints placed on the G0.120-0.048 nebula from DustEM model fits to its SED and implies a total dust mass of 0.021 M ☉ . The total IR luminosity of the G0.120-0.048 nebula is

  9. Nature versus nurture: Luminous blue variable nebulae in and near massive stellar clusters at the galactic center

    Lau, R. M.; Herter, T. L.; Adams, J. D. [Astronomy Department, 202 Space Sciences Building, Cornell University, Ithaca, NY 14853-6801 (United States); Morris, M. R. [Department of Physics and Astronomy, University of California, Los Angeles, 430 Portola Plaza, Los Angeles, CA 90095-1547 (United States)

    2014-04-20

    Three luminous blue variables (LBVs) are located in and near the Quintuplet Cluster at the Galactic center: the Pistol Star, G0.120-0.048, and qF362. We present imaging at 19, 25, 31, and 37 μm of the region containing these three LBVs, obtained with SOFIA using FORCAST. We argue that Pistol and G0.120-0.048 are identical 'twins' that exhibit contrasting nebulae due to the external influence of their different environments. Our images reveal the asymmetric, compressed shell of hot dust surrounding the Pistol Star and provide the first detection of the thermal emission from the symmetric, hot dust envelope surrounding G0.120-0.048. However, no detection of hot dust associated with qF362 is made. Dust and gas composing the Pistol nebula are primarily heated and ionized by the nearby Quintuplet Cluster stars. The northern region of the Pistol nebula is decelerated due to the interaction with the high-velocity (2000 km s{sup –1}) winds from adjacent Wolf-Rayet Carbon (WC) stars. From fits to the spectral energy distribution (SED) of the Pistol nebula with the DustEM code we determine that the Pistol nebula is composed of a distribution of very small, transiently heated grains (10 to ∼ 35 Å) having a total dust mass of 0.03 M {sub ☉}, and that it exhibits a gradient of decreasing grain size from south to north due to differential sputtering by the winds from the WC stars. The total IR luminosity of the Pistol nebula is 5.2 × 10{sup 5} L {sub ☉}. Dust in the G0.120-0.048 nebula is primarily heated by the central star; however, the nebular gas is ionized externally by the Arches Cluster. Unlike the Pistol nebula, the G0.120-0.048 nebula is freely expanding into the surrounding medium. A grain size distribution identical to that of the non-sputtered region of the Pistol nebula satisfies the constraints placed on the G0.120-0.048 nebula from DustEM model fits to its SED and implies a total dust mass of 0.021 M {sub ☉}. The total IR luminosity of the G

  10. Imaging Obsearvations of Jupiter's Sodium Magneto-Nebula During the Ulysses Encounter.

    Mendillo, M; Flynn, B; Baumgardner, J

    1992-09-11

    Jupiter's great sodium nebula represents the largest visible structure traversed by the Ulysses spacecraft during its encounter with the planet in February 1992. Ground-based imaging conducted on Mount Haleakala, Hawaii, revealed a nebula that extended to at least +/-300 Jovian radii (spanning approximately 50 million kilometers); it was somewhat smaller in scale and less bright than previously observed. Analysis of observations and results of modeling studies suggest reduced volcanic activity on the moon lo, higher ion temperatures in the plasma torus, lower total plasma content in the torus, and fast neutral atomic clouds along the Ulysses inbound trajectory through the magnetosphere. Far fewer neutrals were encountered by the spacecraft along its postencounter, out-of-ecliptic trajectory.

  11. Solar nebula heterogeneity in p-process samarium and neodymium isotopes.

    Andreasen, Rasmus; Sharma, Mukul

    2006-11-03

    Bulk carbonaceous chondrites display a deficit of approximately 100 parts per million (ppm) in 144Sm with respect to other meteorites and terrestrial standards, leading to a decrease in their 142Nd/144Nd ratios by approximately 11 ppm. The data require that samarium and neodymium isotopes produced by the p process associated with photodisintegration reactions in supernovae were heterogeneously distributed in the solar nebula. Other samarium and neodymium isotopes produced by rapid neutron capture (r process) in supernovae and by slow neutron capture (s process) in red giants were homogeneously distributed. The supernovae sources supplying the p- and r-process nuclides to the solar nebula were thus disconnected or only weakly connected.

  12. Oxygen isotope exchange between refractory inclusion in allende and solar nebula Gas

    Yurimoto; Ito; Nagasawa

    1998-12-04

    A calcium-aluminum-rich inclusion (CAI) from the Allende meteorite was analyzed and found to contain melilite crystals with extreme oxygen-isotope compositions ( approximately 5 percent oxygen-16 enrichment relative to terrestrial oxygen-16). Some of the melilite is also anomalously enriched in oxygen-16 compared with oxygen isotopes measured in other CAIs. The oxygen isotopic variation measured among the minerals (melilite, spinel, and fassaite) indicates that crystallization of the CAI started from oxygen-16-rich materials that were probably liquid droplets in the solar nebula, and oxygen isotope exchange with the surrounding oxygen-16-poor nebular gas progressed through the crystallization of the CAI. Additional oxygen isotope exchange also occurred during subsequent reheating events in the solar nebula.

  13. A Model for the Dynamical and Ionization Structure of Planetary Nebula IC 418

    J. Ghanbari

    1997-04-01

    Full Text Available   The interacting two winds model and a spherical density distribution function are introduced to study the dynamical and ionization structure of the planetary nebula IC 418. A fast wind with a mechanical luminousity  2/34×1034erg.s-1 of interacts with a super wind with a mass-loss rate of  2×10-5M(°yr-1 and  a velocity of 10 , and produces a dense and luminous medium.   In this model, the expansion velocities of OI and HI lines are predicted to be 11 and 10.5kms-1 , respectively. The calculated dynamical time-scale 1033yr for the nebula is in good agreement with the evolution time of the central star after the interaction of the two winds. Our calculations give a luminosity  0.05M(°of for the central star

  14. Organic synthesis via irradiation and warming of ice grains in the solar nebula.

    Ciesla, Fred J; Sandford, Scott A

    2012-04-27

    Complex organic compounds, including many important to life on Earth, are commonly found in meteoritic and cometary samples, though their origins remain a mystery. We examined whether such molecules could be produced within the solar nebula by tracking the dynamical evolution of ice grains in the nebula and recording the environments to which they were exposed. We found that icy grains originating in the outer disk, where temperatures were less than 30 kelvin, experienced ultraviolet irradiation exposures and thermal warming similar to that which has been shown to produce complex organics in laboratory experiments. These results imply that organic compounds are natural by-products of protoplanetary disk evolution and should be important ingredients in the formation of all planetary systems, including our own.

  15. The interstellar medium, expanding nebulae and triggered star formation theory and simulations

    Bisbas, Thomas G

    2016-01-01

    This brief brings together the theoretical aspects of star formation and ionized regions with the most up-to-date simulations and observations. Beginning with the basic theory of star formation, the physics of expanding HII regions is reviewed in detail and a discussion on how a massive star can give birth to tens or hundreds of other stars follows. The theoretical description of star formation is shown in simplified and state-of-the-art numerical simulations, describing in a more clear way how feedback from massive stars can trigger star and planet formation. This is also combined with spectacular images of nebulae taken by talented amateur astronomers. The latter is very likely to stimulate the reader to observe the structure of nebulae from a different point of view, and better understand the associated star formation therein.

  16. Discovery of a radio nebula around PSR J0855-4644

    Maitra, C.; Roy, S.; Acero, F.; Gupta, Y.

    2018-03-01

    We report the discovery of a diffuse radio emission around PSR J0855-4644 using an upgraded GMRT (uGMRT) observation at 1.35 GHz. The radio emission is spatially coincident with the diffuse X-ray pulsar wind nebula (PWN) seen with XMM-Newton but is much larger in extent compared to the compact axisymmetric PWN seen with Chandra. The morphology of the emission, with a bright partial ring-like structure and two faint tail-like features strongly resembles a bow shock nebula, and indicates a velocity of 100 km/s through the ambient medium. We conclude that the emission is most likely to be associated with the radio PWN of PSR J0855-4644. From the integrated flux density, we estimate the energetics of the PWN.

  17. Detection of a noble gas molecular ion, 36ArH+, in the Crab Nebula.

    Barlow, M J; Swinyard, B M; Owen, P J; Cernicharo, J; Gomez, H L; Ivison, R J; Krause, O; Lim, T L; Matsuura, M; Miller, S; Olofsson, G; Polehampton, E T

    2013-12-13

    Noble gas molecules have not hitherto been detected in space. From spectra obtained with the Herschel Space Observatory, we report the detection of emission in the 617.5- and 1234.6-gigahertz J = 1-0 and 2-1 rotational lines of (36)ArH(+) at several positions in the Crab Nebula, a supernova remnant known to contain both molecular hydrogen and regions of enhanced ionized argon emission. Argon-36 is believed to have originated from explosive nucleosynthesis in massive stars during core-collapse supernova events. Its detection in the Crab Nebula, the product of such a supernova event, confirms this expectation. The likely excitation mechanism for the observed (36)ArH(+) emission lines is electron collisions in partially ionized regions with electron densities of a few hundred per centimeter cubed.

  18. Small-scale kinematic structures in ring nebulae around Wolf-Rayet stars

    Chu, Y.H.

    1988-01-01

    Four ring nebulas around galactic Wolf-Rayet stars have been observed with echelle spectrographs in the long-slit mode: NGC 2359, NGC 3199, NGC 6888, and RCW 58. The spatial resolution of these observations is seeing limited at about 1-3 arcsec, which is almost a two orders of magnitude improvement from the previous Fabry-Perot scanner observations. To avoid large geometric corrections, the slit positions were placed as close to the central stars as possible. The results show that the ejecta-type nebula RCW 58 is a clumpy shell expanding regularly at about 110 km/s, as opposed to the chaotic expansion concluded from the earlier Fabry-Perot observations. For the three windblown bubbles, NGC 2359, NGC 3199, and NGC 6888, the small-scale structures revealed in the echelle data can explain the apparently discrepant expansion velocities derived from the previous large-aperture Fabry-Perot observations. 20 references

  19. Bursts of the Crab Nebula gamma-ray emission at high and ultra-high energies

    Lidvansky A.S.

    2017-01-01

    Full Text Available Characteristics of the flares of gamma rays detected from the Crab Nebula by the AGILE and Fermi-LAT satellite instruments are compared with those of a gamma ray burst recorded by several air shower arrays on February 23, 1989 and with one recent observation made by the ARGO-YBJ array. It is demonstrated that though pulsar-periodicity and energy spectra of emissions at 100 MeV (satellite gamma ray telescopes and 100 TeV (EAS arrays are different, their time structures seem to be similar. Moreover, maybe the difference between “flares” and “waves” recently found in the Crab Nebula emission by the AGILE team also exists at ultra-high energies.

  20. The population of planetary nebulae near the Galactic Centre: chemical abundances

    Mollá, M.; Cavichia, O.; Costa, R. D. D.; Maciel, W. J.

    2017-10-01

    In this work, we report physical parameters and abundances derived for a sample of 15 high extinction planetary nebulae located in the inner 2° of the Galactic bulge, based on low dispersion spectroscopy secured at the SOAR telescope using the Goodman spectrograph. The new data allow us to extend our database including older, weaker objects that are at the faint end of the planetary nebulae luminosity function. The data provide chemical compositions for PNe located in this region of the bulge to explore the chemical enrichment history of the central region of the Galactic bulge. The results show that the abundances of our sample are skewed to higher metallicities than previous data in the outer regions of the bulge. This can indicate a faster chemical enrichment taking place at the Galactic centre.

  1. Aerodynamic properties of fractal grains: implications for the primordial solar nebula

    Meakin, P.; Donn, B.

    1988-01-01

    Under conditions in the primordial solar nebula and dense interstellar clouds, small grains have low relative velocities. This is the condition for efficient sticking and formation of fractal aggregates. A calculation of the ratio of cross section, sigma, to number of primary particles, N, for fractal clusters yielded 1n sigma/N = 0.2635 + 0.5189N sup (-0.1748). This ratio decreases slowly with N and approaches a constant for large N. Under the usual assumption of collisions producing spherical compact, uniform density aggregates, sigma/N varies as N sup -1/3 and decreases rapidly. Fractal grains are therefore much more closely coupled to the gas than are compact aggregates. This has a significant effect on the aerodynamic behavior of aggregates and consequently on their evolution and that of the nebula

  2. VizieR Online Data Catalog: Catalogue of Galactic Planetary Nebulae (Kohoutek, 2001)

    Kohoutek, L.

    2001-05-01

    The "Catalogue of Galactic Planetary Nebulae (Version 2000)" appears in Abhandlungen aus der Hamburger Sternwarte, Band XII in the year 2001. It is a continuation of CGPN(1967) and contains 1510 objects classified as galactic PNe up to the end of 1999. The lists of possible pre-PNe and possible post-PNe are also given. The catalogue is restricted only to the data belonging to the location and identification of the objects. It gives identification charts of PNe discovered since 1965 (published in the supplements to CGPN) and those charts of objects discovered earlier, which have wrong or uncertain identification. The question "what is a planetary nebula" is discussed and the typical values of PNe and of their central stars are summarized. Short statistics about the discoveries of PNe are given. The catalogue is also available in the Centre de Donnees, Strasbourg and at Hamburg Observatory via internet. (15 data files).

  3. Abundances in Planetary Nebulae: an Autopsy of Low and Intermediate Mass Stars

    Buell, James Francis

    In this work we report on the results of synthetic thermally pulsing asymptotic giant branch models (TP-AGB) and compare the results to the abundance ratios in a sample of planetary nebulae. We use updated the input parameters for mass-loss, the stellar luminosity, and dredge-up. We calculated models with masses between 0.8 solar masses and 8 solar masses. We also calculated models with (Fe/H) between -2.5 and 0.3. The effect of the first, second, and third dredge-up as well as hot-bottom burning are reported on. The analysis of a sample of Galactic bulge and disk planetary nebulae is also reported on.

  4. Mass distribution and evolutionary scheme for central stars of planetary nebulae

    Heap, S.R.; Augensen, H.J.; Widener Univ., Chester, PA)

    1987-01-01

    IUE data and a distance measuring method that considered central stars in optically thick nebulae were used to examine mass distributions of planetary nebulae. Other data such as spectral type, spatial and kinematic characteristics, etc., were studied to derive relationships between population type and mass distribution. A central star mass range of at least 0.55 solar mass was obtained. Stars with masses of at least 0.64 solar mass, concentrated in the galactic disk, originated from 1.5 solar mass stars. Low mass nuclei originated in old disk or halo populations and evolved from 1.0 solar mass objects. A mass-loss parameter value of 1/3 was calculated for red giants, implying that white dwarfs evolve from stars of under 5 solar masses. Mass distributions around planetary nuclei were concluded to follow patterns associated with the individual mass. 75 references

  5. On the formation of runaway stars BN and x in the Orion Nebula Cluster

    Farias, J. P.; Tan, J. C.

    2018-05-01

    We explore scenarios for the dynamical ejection of stars BN and x from source I in the Kleinmann-Low nebula of the Orion Nebula Cluster (ONC), which is important because it is the closest region of massive star formation. This ejection would cause source I to become a close binary or a merger product of two stars. We thus consider binary-binary encounters as the mechanism to produce this event. By running a large suite of N-body simulations, we find that it is nearly impossible to match the observations when using the commonly adopted masses for the participants, especially a source I mass of 7 M⊙. The only way to recreate the event is if source I is more massive, that is, 20 M⊙. However, even in this case, the likelihood of reproducing the observed system is low. We discuss the implications of these results for understanding this important star-forming region.

  6. Exploring Infiniband Hardware Virtualization in OpenNebula towards Efficient High-Performance Computing

    Pais Pitta de Lacerda Ruivo, Tiago [IIT, Chicago; Bernabeu Altayo, Gerard [Fermilab; Garzoglio, Gabriele [Fermilab; Timm, Steven [Fermilab; Kim, Hyun-Woo [Fermilab; Noh, Seo-Young [KISTI, Daejeon; Raicu, Ioan [IIT, Chicago

    2014-11-11

    has been widely accepted that software virtualization has a big negative impact on high-performance computing (HPC) application performance. This work explores the potential use of Infiniband hardware virtualization in an OpenNebula cloud towards the efficient support of MPI-based workloads. We have implemented, deployed, and tested an Infiniband network on the FermiCloud private Infrastructure-as-a-Service (IaaS) cloud. To avoid software virtualization towards minimizing the virtualization overhead, we employed a technique called Single Root Input/Output Virtualization (SRIOV). Our solution spanned modifications to the Linux’s Hypervisor as well as the OpenNebula manager. We evaluated the performance of the hardware virtualization on up to 56 virtual machines connected by up to 8 DDR Infiniband network links, with micro-benchmarks (latency and bandwidth) as well as w a MPI-intensive application (the HPL Linpack benchmark).

  7. Galaxy evolution. Quasar quartet embedded in giant nebula reveals rare massive structure in distant universe.

    Hennawi, Joseph F; Prochaska, J Xavier; Cantalupo, Sebastiano; Arrigoni-Battaia, Fabrizio

    2015-05-15

    All galaxies once passed through a hyperluminous quasar phase powered by accretion onto a supermassive black hole. But because these episodes are brief, quasars are rare objects typically separated by cosmological distances. In a survey for Lyman-α emission at redshift z ≈ 2, we discovered a physical association of four quasars embedded in a giant nebula. Located within a substantial overdensity of galaxies, this system is probably the progenitor of a massive galaxy cluster. The chance probability of finding a quadruple quasar is estimated to be ∼10(-7), implying a physical connection between Lyman-α nebulae and the locations of rare protoclusters. Our findings imply that the most massive structures in the distant universe have a tremendous supply (≃10(11) solar masses) of cool dense (volume density ≃ 1 cm(-3)) gas, which is in conflict with current cosmological simulations. Copyright © 2015, American Association for the Advancement of Science.

  8. Organic Synthesis via Irradiation and Warming of Ice Grains in the Solar Nebula

    Ciesla, Fred J.; Sanford, Scott A.

    2012-01-01

    Complex organic compounds, including many important to life on Earth, are commonly found in meteoritic and cometary samples, though their origins remain a mystery. We examined whether such molecules could be produced within the solar nebula by tracking the dynamical evolution of ice grains in the nebula and recording the environments they were exposed to. We found that icy grains originating in the outer disk, where temperatures were less than 30 K, experienced UV irradiation exposures and thermal warming similar to that which has been shown to produce complex organics in laboratory experiments. These results imply that organic compounds are natural byproducts of protoplanetary disk evolution and should be important ingredients in the formation of all planetary systems, including our own.

  9. The Wolf-Rayet nebula NGC 3199 - an interstellar snow plough?

    Dyson, J. E.; Ghanbari, J.

    1989-12-01

    The Wolf-Rayet nebula NGC 3199 has a highly asymmetric morphology, with a very bright hemisphere near the exciting star HD 89358 and a much fainter and more extended other hemisphere. This nebula is modeled in terms of the distorted bubble produced by a moving star blowing a strong stellar wind into a surrounding uniform interstellar medium; this model is fitted to the morphology and observed kinematic data. The exciting star appears to be moving at about 60 km/s into local interstellar gas of density of about 10/cu cm, and has a mass-loss rate of about 0.000027 solar mass/yr. This latter mass-loss rate is in excellent agreement with observed mass-loss rates from Wolf-Rayet stars.

  10. New DSH planetary nebulae and candidates from optical and infrared surveys

    Kronberger, Matthias; Jacoby, George H; Alves, Filipe; Patchick, Dana; Parker, Quentin A; Bojicic, Ivan; Frew, David J; Acker, Agnes; Eigenthaler, Paul; Harmer, Dianne; Reid, Warren; Schedler, Johannes

    2016-01-01

    To date, the planetary nebula (PN) survey of the Deep Sky Hunters collaboration has led to the detection of more than 250 previously unknown candidate planetary nebulae (PNe). About 60% of them were found during the past two years and are expected to be true, likely or possible PNe because careful vetting has already thrown out more doubtful objects. The majority of the new PN candidates are located within the boundaries of the SHS and IPHAS Ha surveys and were discovered by combining MIR data from the WideField Infrared Survey Explorer (WISE) with optical data from the IPHAS, SHS and DSS surveys, and UV data from the Galaxy Evolution Explorer(GALEX). (paper)

  11. Pregalactic helium abundance and abundance gradients across our galaxy from planetary nebulae

    D' Odorico, S; Peimbert, M [Universidad Nacional Autonoma de Mexico, Mexico City. Instituto de Astronomia; Sabbadin, F [Padua Univ. (Italy). Istituto di Astronomia

    1976-03-01

    From the observations of planetary nebulae by Peimbert and Torres-Peimbert we have studied the radial gradients across our galaxy of the helium, oxygen and nitrogen abundance relative to hydrogen. The increase of the oxygen to hydrogen abundance ratio from a radial distance to the galactic center of 14 to 8 kpc is about a factor of 3 while that of the nitrogen to hydrogen ratio is about twice as large. By adopting oxygen as representative of the heavy elements it is found that the helium enrichment is coupled to the heavy metal enrichment by ..delta..Y/..delta..Zapproximately2.9 in close agreement with the value derived from H II regions. The pregalactic N(He)/N(H) value derived from planetary nebulae is 0.073+-0.008 also in agreement with the value derived from H II regions.

  12. Spatially-resolved Spectroscopy of the IC443 Pulsar Wind Nebula and Environs

    Swartz, Douglas A.; Weisskopf, M. C.; Zavlin, V.; Bucciantini, N.; Clarke, T. E.; Karovska, M.; Pavlov, G. G.; van der Horst, A.; Yukita, M.

    2013-04-01

    Deep Chandra ACIS observations of the region around the putative pulsar, CXO J061705.3+222127, in the supernova remnant IC443 confirm that (1) the spectrum and flux of the central object are consistent with a rotation-powered pulsar interpretation, (2) the non-thermal surrounding nebula is likely powered by a pulsar wind, and (3) the thermal-dominated spectrum at greater distances is consistent with emission from the supernova remnant. The observations further reveal, for the first time, a ring-like morphology surrounding the pulsar and a jet-like structure oriented roughly north-south across the ring and through the pulsar location. The cometary shape of the nebula, suggesting motion towards the southwest, appears to be subsonic; there is no evidence for a strong bow shock and the ring, presumably formed at a wind termination shock, is not distorted by motion through the ambient medium.

  13. Spatially-resolved Spectroscopy of the IC443 Pulsar Wind Nebula and Environs

    Swartz, D. A.; Weisskopf, M. C.; Zavlin, V. E.; Bucciantini, N.; Clarke, T. E.; Karovska, M.; Pavlov, G. G.; O'Dell, S. L.; vanderHorst, A J.; Yukita, M.

    2013-01-01

    Deep Chandra ACIS observations of the region around the putative pulsar, CXOU J061705.3+222117, in the supernova remnant IC443 reveal, for the first time, a ring-like morphology surrounding the pulsar and a jet-like structure oriented roughly north-south across the ring and through the pulsar location. The observations further confirm that (1) the spectrum and flux of the central object are consistent with a rotation-powered pulsar interpretation, (2) the non-thermal surrounding nebula is likely powered by the pulsar wind, and (3) the thermal-dominated spectrum at greater distances is consistent with emission from the supernova remnant. The cometary shape of the nebula, suggesting motion towards the southwest (or, equivalently, flow of ambient medium to the northeast), appears to be subsonic; there is no evidence for a strong bow shock, and the circular ring is not distorted by motion through the ambient medium.

  14. Helix Nebula and CERN: A Symbiotic approach to exploiting commercial clouds

    Barreiro Megino, Fernando Harald; Kucharczyk, Katarzyna; Medrano Llamas, Ramón; van der Ster, Daniel

    2014-01-01

    The recent paradigm shift toward cloud computing in IT, and general interest in "Big Data" in particular, have demonstrated that the computing requirements of HEP are no longer globally unique. Indeed, the CERN IT department and LHC experiments have already made significant R&D investments in delivering and exploiting cloud computing resources. While a number of technical evaluations of interesting commercial offerings from global IT enterprises have been performed by various physics labs, further technical, security, sociological, and legal issues need to be address before their large-scale adoption by the research community can be envisaged. Helix Nebula - the Science Cloud is an initiative that explores these questions by joining the forces of three European research institutes (CERN, ESA and EMBL) with leading European commercial IT enterprises. The goals of Helix Nebula are to establish a cloud platform federating multiple commercial cloud providers, along with new business models, which can sustain ...

  15. A D'-type symbiotic binary in the planetary nebula SMP LMC 88

    Iłkiewicz, Krystian; Mikołajewska, Joanna; Miszalski, Brent; Kozłowski, Szymon; Udalski, Andrzej

    2018-05-01

    SMP LMC 88 is one of the planetary nebulae (PNe) in the Large Magellanic Cloud. We identify in its spectrum Raman scattered O VI lines at 6825 and 7083 Å. This unambiguously classifies the central object of the nebula as a symbiotic star (SySt). We identified the cold component to be a K-type giant, making this the first D'-type (yellow) SySt discovered outside the Galaxy. The photometric variability in SMP LMC 88 resembles the orbital variability of Galactic D'-type SySt with its low amplitude and sinusoidal light-curve shape. The SySt classification is also supported by the He I diagnostic diagram.

  16. Helix Nebula and CERN: A Symbiotic approach to exploiting commercial clouds

    Barreiro Megino, Fernando Harald; Kucharczyk, Katarzyna; Medrano Llamas, Ramón; van der Ster, Daniel

    2013-01-01

    The recent paradigm shift toward cloud computing in IT, and general interest in "Big Data" in particular, have demonstrated that the computing requirements of HEP are no longer globally unique. Indeed, the CERN IT department and LHC experiments have already made significant R&D; investments in delivering and exploiting cloud computing resources. While a number of technical evaluations of interesting commercial offerings from global IT enterprises have been performed by various physics labs, further technical, security, sociological, and legal issues need to be address before their large-scale adoption by the research community can be envisaged. Helix Nebula - the Science Cloud is an initiative that explores these questions by joining the forces of three European research institutes (CERN, ESA and EMBL) with leading European commercial IT enterprises. The goals of Helix Nebula are to establish a cloud platform federating multiple commercial cloud providers, along with new business models, which can sustain...

  17. SMC SMP 24: A newly radio-detected planetary nebula in the small Magellanic cloud

    Bojičić I.S.

    2010-01-01

    Full Text Available In this paper we report a new radio-continuum detection of an extragalactic planetary nebula (PN: SMC SMP 24. We show the radio-continuum image of this PN and present the measured radio data. The newly reduced radio observations are consistent with the multi-wavelength data and derived parameters found in the literature. SMC SMP 24 appears to be a young and compact PN, optically thick at frequencies below 2 GHz.

  18. SMC SMP 24: A Newly Radio-Detected Planetary Nebula in the Small Magellanic Cloud

    Bojicic, I. S.

    2010-12-01

    Full Text Available In this paper we report a new radio-continuum detection of an extragalactic planetary nebula (PN: SMC~SMP~24. We show the radio-continuum image of this PN and present the measured radio data. The newly reduced radio observations are consistent with the multi-wavelength data and derived parameters found in the literature. SMC~SMP~24 appears to be a young and compact PN, optically thick at frequencies below 2~GHz.

  19. The trace of the CNO cycle in the ring nebula NGC 6888

    Mesa-Delgado, A. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago (Chile); Esteban, C.; García-Rojas, J. [Instituto de Astrofísica de Canarias, E-38200 La Laguna, Tenerife (Spain); Reyes-Pérez, J.; Morisset, C. [Instituto de Astronomía, Universidad Nacional Autónoma de México, Apdo. Postal 70264, Méx. D. F. 04510 (Mexico); Bresolin, F., E-mail: amesad@astro.puc.cl [Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2014-04-20

    We present new results on the chemical composition of the Galactic ring nebula NGC 6888 surrounding the WN6(h) star WR136. The data are based on deep spectroscopical observations taken with the High Dispersion Spectrograph at the 8.2 m Subaru Telescope. The spectra cover the optical range from 3700 to 7400 Å. The effect of the CNO cycle is well-identified in the abundances of He, N, and O, while elements not involved in the synthesis such as Ar, S, and Fe present values consistent with the solar vicinity and the ambient gas. The major achievement of this work is the first detection of the faint C II λ4267 recombination line in a Wolf-Rayet nebula. This allows us to estimate the C abundance in NGC 6888 and therefore investigate for the first time the trace of the CNO cycle in a ring nebula around a Wolf-Rayet star. Although the detection of the C II line has a low signal-to-noise ratio, the C abundance seems to be higher than the predictions of recent stellar evolution models of massive stars. The Ne abundance also shows a puzzling pattern with an abundance of about 0.5 dex lower than the solar vicinity, which may be related to the action of the NeNa cycle. Attending to the constraints imposed by the dynamical timescale and the He/H and N/O ratios of the nebula, the comparison with stellar evolution models indicates that the initial mass of the stellar progenitor of NGC 6888 is between 25 M {sub ☉} and 40 M {sub ☉}.

  20. The spectrum of HM Sagittae: a planetary nebula excited by a Wolf--Rayet star

    Brown, L.W.; Feibelman, W.A.; Hobbs, R.W.; Mccracken, C.W.

    1977-10-01

    Image tube spectrograms of HM Sagittae were obtained. More than 70 emission lines, including several broad emission features, were identified. An analysis of the spectra indicates that HM Sagittae is a planetary nebula excited by a Wolf-Rayet star. The most conspicuous Wolf-Rayet feature is that attributed to a blend of C III at 4650 A and He II at 4686 A