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Sample records for dwarf nova ht

  1. Orbital period determination in an eclipsing dwarf nova HT Cas

    Science.gov (United States)

    Bąkowska, Karolina; Olech, Arkadiusz

    2014-09-01

    HT Cassiopeiae was discovered over seventy years ago (Hoffmeister 1943). Unfortunately, for 35 years this object did not receive any attention, until the eclipses of HT Cas were observed by Bond. After a first analysis, Patterson (1981) called HT Cas "a Rosetta stone among dwarf novae". Since then, the literature on this star is still growing, reaching several dozens of publications. We present an orbital period determination of HT Cas during the November 2010 super-outburst, but also during a longer time span, to check its stability.

  2. Dwarf Nova Outbursts with Magnetorotational Turbulence

    CERN Document Server

    Coleman, M S B; Blaes, O; Lasota, J -P; Hirose, S

    2016-01-01

    The phenomenological Disc Instability Model has been successful in reproducing the observed light curves of dwarf nova outbursts by invoking an enhanced Shakura-Sunyaev $\\alpha$ parameter $\\sim0.1-0.2$ in outburst compared to a low value $\\sim0.01$ in quiescence. Recent thermodynamically consistent simulations of magnetorotational (MRI) turbulence with appropriate opacities and equation of state for dwarf nova accretion discs have found that thermal convection enhances $\\alpha$ in discs in outburst, but only near the hydrogen ionization transition. At higher temperatures, convection no longer exists and $\\alpha$ returns to the low value comparable to that in quiescence. In order to check whether this enhancement near the hydrogen ionization transition is sufficient to reproduce observed light curves, we incorporate this MRI-based variation in $\\alpha$ into the Disc Instability Model, as well as simulation-based models of turbulent dissipation and convective transport. These MRI-based models can successfully r...

  3. Dwarf nova outbursts with magnetorotational turbulence

    Science.gov (United States)

    Coleman, M. S. B.; Kotko, I.; Blaes, O.; Lasota, J.-P.; Hirose, S.

    2016-11-01

    The phenomenological disc instability model has been successful in reproducing the observed light curves of dwarf nova outbursts by invoking an enhanced Shakura-Sunyaev α parameter ˜0.1-0.2 in outburst compared to a low value ˜0.01 in quiescence. Recent thermodynamically consistent simulations of magnetorotational instability (MRI) turbulence with appropriate opacities and equation of state for dwarf nova accretion discs have found that thermal convection enhances α in discs in outburst, but only near the hydrogen ionization transition. At higher temperatures, convection no longer exists and α returns to the low value comparable to that in quiescence. In order to check whether this enhancement near the hydrogen ionization transition is sufficient to reproduce observed light curves, we incorporate this MRI-based variation in α into the disc instability model, as well as simulation-based models of turbulent dissipation and convective transport. These MRI-based models can successfully reproduce observed outburst and quiescence durations, as well as outburst amplitudes, albeit with different parameters from the standard disc instability models. The MRI-based model light curves exhibit reflares in the decay from outburst, which are not generally observed in dwarf novae. However, we highlight the problematic aspects of the quiescence physics in the disc instability model and MRI simulations that are responsible for this behaviour.

  4. AT Cnc: A SECOND DWARF NOVA WITH A CLASSICAL NOVA SHELL

    Energy Technology Data Exchange (ETDEWEB)

    Shara, Michael M.; Mizusawa, Trisha; Zurek, David [Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024-5192 (United States); Wehinger, Peter [Steward Observatory, the University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Martin, Christopher D.; Neill, James D.; Forster, Karl [Department of Physics, Math and Astronomy, California Institute of Technology, 1200 East California Boulevard, Mail Code 405-47, Pasadena, CA 91125 (United States); Seibert, Mark [Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

    2012-10-20

    We are systematically surveying all known and suspected Z Cam-type dwarf novae for classical nova shells. This survey is motivated by the discovery of the largest known classical nova shell, which surrounds the archetypal dwarf nova Z Camelopardalis. The Z Cam shell demonstrates that at least some dwarf novae must have undergone classical nova eruptions in the past, and that at least some classical novae become dwarf novae long after their nova thermonuclear outbursts, in accord with the hibernation scenario of cataclysmic binaries. Here we report the detection of a fragmented 'shell', 3 arcmin in diameter, surrounding the dwarf nova AT Cancri. This second discovery demonstrates that nova shells surrounding Z Cam-type dwarf novae cannot be very rare. The shell geometry is suggestive of bipolar, conical ejection seen nearly pole-on. A spectrum of the brightest AT Cnc shell knot is similar to that of the ejecta of the classical nova GK Per, and of Z Cam, dominated by [N II] emission. Galaxy Evolution Explorer FUV imagery reveals a similar-sized, FUV-emitting shell. We determine a distance of 460 pc to AT Cnc, and an upper limit to its ejecta mass of {approx}5 Multiplication-Sign 10{sup -5} M {sub Sun }, typical of classical novae.

  5. AT Cnc: A Second Dwarf Nova with a Classical Nova Shell

    CERN Document Server

    Shara, Michael M; Wehinger, Peter; Zurek, David; Martin, Christopher D; Neill, James D; Forster, Karl; Seibert, Mark

    2012-01-01

    We are systematically surveying all known and suspected Z Cam-type dwarf novae for classical nova shells. This survey is motivated by the discovery of the largest known classical nova shell, which surrounds the archetypal dwarf nova Z Camelopardalis. The Z Cam shell demonstrates that at least some dwarf novae must have undergone classical nova eruptions in the past, and that at least some classical novae become dwarf novae long after their nova thermonuclear outbursts, in accord with the hibernation scenario of cataclysmic binaries. Here we report the detection of a fragmented "shell", 3 arcmin in diameter, surrounding the dwarf nova AT Cancri. This second discovery demonstrates that nova shells surrounding Z Cam-type dwarf novae cannot be very rare. The shell geometry is suggestive of bipolar, conical ejection seen nearly pole-on. A spectrum of the brightest AT Cnc shell knot is similar to that of the ejecta of the classical nova GK Per, and of Z Cam, dominated by [NII] emission. Galex FUV imagery reveals a ...

  6. Characterization of Dwarf Novae Using SDSS Colors

    CERN Document Server

    Kato, Taichi; Uemura, Makoto

    2011-01-01

    We have developed a method for estimating orbital periods of dwarf novae from SDSS colors in quiescence using an artificial neural network. For typical objects below the period gap with good photometric accuracy, we could estimate orbital periods to a 1-sigma error of 22%. The error of estimation is worse for systems with longer periods. We have also developed a neural network-based method for categorical classification. This method has been proven to be efficient in classifying objects into three categories (WZ Sge-type, SU UMa-type and SS Cyg/Z Cam-type) and works for very faint objects down to g=21. Using these methods, we have investigated the distribution of orbital periods of dwarf novae from a modern transient survey (Catalina Real-Time Survey). Using Bayesian analysis developed by Uemura et al. (2010, arXiv:1003.0945), the present sample tends to give a flatter distribution toward the shortest period and a shorter estimate of the period minimum, which may have been resulted from the uncertainties in t...

  7. Optical spectroscopy of the dwarf nova U Geminorum

    NARCIS (Netherlands)

    Unda-Sanzana, E.; Marsh, T.R.; Morales-Rueda, L.

    2006-01-01

    The dwarf nova U Gem is unique in having a direct measurement of the K velocity of its white dwarf from Hubble Space Telescope (HST) spectra (K1 = 107 +/- 2kms-1 from Long et al.). We present high-resolution optical spectra of U Gem in quiescence taken to test the accuracy to w

  8. When does an old nova become a dwarf nova? Kinematics and age of the nova shell of the dwarf nova AT Cancri

    Science.gov (United States)

    Shara, Michael M.; Drissen, Laurent; Martin, Thomas; Alarie, Alexandre; Stephenson, F. Richard

    2017-02-01

    The Z Cam-type dwarf nova AT Cancri (AT Cnc) displays a classical nova (CN) shell, demonstrating that mass transfer in cataclysmic binaries decreases substantially after a CN eruption. The hibernation scenario of cataclysmic binaries predicts such a decrease, on a time-scale of a few centuries. In order to measure the time since AT Cnc's last CN eruption, we have measured the radial velocities of a hundred clumps in its ejecta with SITELLE, Canada-France-Hawaii Telescope's recently commissioned imaging Fourier transform spectrometer. These range from -455 to +490 km s-1. Coupled with the known distance to AT Cnc of 460 pc, the size of AT Cnc's shell, and a simple model of nova ejecta deceleration, we determine that the last CN eruption of this system occurred 330_{-90}^{+135} yr ago. This is the most rapid transition from a high mass-transfer rate, nova-like variable to a low mass-transfer rate, dwarf nova yet measured, and in accord with the hibernation scenario of cataclysmic binaries. We conclude by noting the similarity in the deduced outburst date (within a century of 1686 CE) of AT Cnc to a `guest star' reported in the constellation Cancer by Korean observers in 1645 CE.

  9. A Dwarf Nova in the Globular Cluster M13

    NARCIS (Netherlands)

    Servillat, M.; Webb, N.A.; Lewis, F.; Knigge, C.; van den Berg, M.C.; Dieball, A.; Grindlay, J.E.

    2011-01-01

    Dwarf novae (DNe) in globular clusters (GCs) seem to be rare with only 13 detections in the 157 known Galactic GCs. We report the identification of a new DN in M13, the 14th DN identified in a GC to date. Using the 2 m Faulkes Telescope North, we conducted a search for stars in M13 that show variabi

  10. When does an old nova become a dwarf nova? Kinematics and age of the nova shell of the dwarf nova AT Cnc

    CERN Document Server

    Shara, Michael M; Martin, Thomas; Alarie, Alexandre

    2016-01-01

    The Z Cam-type dwarf nova AT Cnc displays a classical nova (CN) shell, demonstrating that mass transfer in cataclysmic binaries decreases substantially after a CN eruption. The hibernation scenario of cataclysmic binaries predicts such a decrease, on a timescale of a few centuries. In order to measure the time since AT Cnc's last CN eruption, we have measured the radial velocities of a hundred clumps in its ejecta with SITELLE, CFHT's recently commissioned imaging Fourier transform spectrometer. These range from -455 to +490 km/s. Coupled with the known distance to AT Cnc of 460 pc (Shara 2012), the size of AT Cnc's shell, and a simple model of nova ejecta deceleration, we determine that the last CN eruption of this system occurred $330_{-90}^{+135}$ years ago. This is the most rapid transition from a high mass transfer rate, novalike variable to a low mass transfer rate, dwarf nova yet measured, and in accord with the hibernation scenario of cataclysmic binaries. We conclude by noting the similarity in deduc...

  11. Erupting Dwarf Novae in the Large Magellanic Cloud

    CERN Document Server

    Shara, M M; Zurek, D R; Shara, Michael M.; Hinkley, Sasha; Zurek, David R.

    2003-01-01

    We report the first likely detections of erupting Dwarf Novae (DN) in an external galaxy: the Large Magellanic Cloud. Six candidates were isolated from approximately a million stars observed every second night over 11 nights with the CTIO 8K x 8K Mosaic2 CCD imager. Artificial dwarf nova and completeness tests suggest that we are seeing only the brightest of the LMC DN, probably SS Cygni-like CVs, but possibly SU UMa-type cataclysmics undergoing superoutbursts. We derive crude but useful limits on the LMC DN surface density, and on the number of DN in the LMC. Many thousands of cataclysmic variables in the Magellanic Clouds can be discovered and characterized with 8 meter class telescopes.

  12. Serendipitous discovery of a dwarf Nova in the Kepler field near the G dwarf KIC 5438845

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Alexander; Ayres, Thomas R. [Center for Astrophysics and Space Astronomy, University of Colorado, 593 UCB, Boulder, CO 80309-0593 (United States); Neff, James E.; Wells, Mark A. [Department of Physics and Astronomy, College of Charleston, 66 George Street, Charleston, SC 29424 (United States); Kowalski, Adam [NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Hawley, Suzanne [Department of Astronomy, University of Washington, Seattle, WA 98195-1580 (United States); Berdyugina, Svetlana [Kiepenheuer Institut für Sonnenphysik, University of Freiburg, Freiburg, D-79104 (Germany); Harper, Graham M. [School of Physics, Trinity College, Dublin 2 (Ireland); Korhonen, Heidi [Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Väisäläntie 20, FI-21500 Piikkiö (Finland); Piskunov, Nikolai [Department of Astronomy and Space Physics, Uppsala University, Uppsala SE-751-20 (Sweden); Saar, Steven [Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Walkowicz, Lucianne, E-mail: Alexander.Brown@colorado.edu [Astrophysical Sciences Department, Princeton University, Princeton, NJ 08544-1001 (United States)

    2015-02-01

    The Kepler satellite provides a unique window into stellar temporal variability by observing a wide variety of stars with multi-year, near-continuous, high precision, optical photometric time series. While most Kepler targets are faint stars with poorly known physical properties, many unexpected discoveries should result from a long photometric survey of such a large area of sky. During our Kepler Guest Observer programs that monitored late-type stars for starspot and flaring variability, we discovered a previously unknown dwarf nova that lies within a few arcseconds of the mid-G dwarf star KIC 5438845. This dwarf nova underwent nine outbursts over a 4 year time span. The two largest outbursts lasted ∼17–18 days and show strong modulations with a 110.8 minute period and a declining amplitude during the outburst decay phase. These properties are characteristic of an SU UMa-type cataclysmic variable. By analogy with other dwarf nova light curves, we associate the 110.8 minute (1.847 hr) period with the superhump period, close to but slightly longer than the orbital period of the binary. No precursor outbursts are seen before the super-outbursts and the overall super-outburst morphology corresponds to Osaki and Meyer “Case B” outbursts, which are initiated when the outer edge of the disk reaches the tidal truncation radius. “Case B” outbursts are rare within the Kepler light curves of dwarf novae. The dwarf nova is undergoing relatively slow mass transfer, as evidenced by the long intervals between outbursts, but the mass transfer rate appears to be steady, because the smaller “normal” outbursts show a strong correlation between the integrated outburst energy and the elapsed time since the previous outburst. At super-outburst maximum the system was at V ∼ 18, but in quiescence it is fainter than V ∼ 22, which will make any detailed quiescent follow-up of this system difficult.

  13. Discovery of an eclipsing dwarf nova in the ancient nova shell Te 11

    CERN Document Server

    Miszalski, Brent; Littlefair, Stuart P; Warner, Brian; Boffin, Henri M J; Corradi, Romano L M; Jones, David; Motsoaledi, Mokhine; Rodríguez-Gil, Pablo; Sabin, Laurence; Santander-García, Miguel

    2015-01-01

    We report on the discovery of an eclipsing dwarf nova (DN) inside the peculiar, bilobed nebula Te 11. Modelling of high-speed photometry of the eclipse finds the accreting white dwarf to have a mass 1.18 M$_\\odot$ and temperature 13 kK. The donor spectral type of M2.5 results in a distance of 330 pc, colocated with Barnard's loop at the edge of the Orion-Eridanus superbubble. The perplexing morphology and observed bow shock of the slowly-expanding nebula may be explained by strong interactions with the dense interstellar medium in this region. We match the DN to the historic nova of 483 CE in Orion and postulate that the nebula is the remnant of this eruption. This connection supports the millennia time scale of the post-nova transition from high to low mass-transfer rates. Te 11 constitutes an important benchmark system for CV and nova studies as the only eclipsing binary out of just three DNe with nova shells.

  14. Hubble Space Telescope Studies of Exposed White Dwarfs in Dwarf Novae

    Science.gov (United States)

    Sion, Edward M.

    Coordinated AAVSO optical observations and Hubble Space Telescope (HST) far ultraviolet (UV) spectroscopic observations of cataclysmic variables, during dwarf nova quiescence when the underlying white dwarf is exposed in the far UV, have yielded a number of new insights into accretional heating, photospheric abundances of the accreted atmosphere, and rotational velocities of the underlying degenerates. Recent results of synthetic spectral analyses of HST spectra are highlighted. Their impact on our understanding of accretion physics and the effect of accretion on the white dwarf are discussed.

  15. CCD Photometry of Dwarf Nova AL Com in Superoutburst

    OpenAIRE

    Pych, W.; Olech, A.

    1995-01-01

    We report a CCD optical photometry of a dwarf nova AL Com in superoutburst. Before superhumps occurred the light curve was highly variable with dominant periods about 41 minutes and 81.5 minutes for different nights. The period of observed superhumps is 82.5 minutes and seems to be stable. The first harmonic of the basic period is also present. We detected a weak signal corresponding to period 78.1 minutes. One of the periods 78.1 or 81.5 is suspected to be a possible signature of orbital mot...

  16. Brief outbursts in the dwarf nova V1316 Cygni

    CERN Document Server

    Shears, J; Poyner, G; Shears, Jeremy; Boyd, David; Poyner, Gary

    2006-01-01

    Several brief outbursts were detected in the dwarf nova V1316 Cyg during 2005. These events have an average amplitude of 1.4 magnitude and a duration of <1 to 2 days. Whilst no outburst period could be confirmed, the shortest period between detected events is 10 days. These curious brief outbursts appear to be the normal pattern of behaviour for this system. They are of smaller amplitude and shorter duration than normal outbursts previously reported in this star. V1316 Cyg appears to be a very unusual system and we suggest that further observations by both amateur and professional astronomers could yield important information about the underlying mechanism.

  17. IX Draconis - a curious ER UMa-type dwarf nova

    CERN Document Server

    Otulakowska-Hypka, M; de Miguel, E; Rutkowski, A; Koff, R; B\\kakowska, K

    2012-01-01

    We report results of an extensive world-wide observing campaign devoted to a very active dwarf nova star - IX Draconis. We investigated photometric behaviour of the system to derive its basic outburst properties and understand peculiarities of IX Dra as well as other active cataclysmic variables, in particular dwarf novae of the ER Uma-type. In order to measure fundamental parameters of the system, we carried out analyses of the light curve, O-C diagram, and power spectra. During over two months of observations we detected two superoutbursts and several normal outbursts. The V magnitude of the star varied in the range 14.6 - 18.2 mag. Superoutbursts occur regularly with the supercycle length of 58.5+/-0.5 d. When analysing data over the past 20 years, we found that the supercycle length is increasing at a rate of P_dot = 1.8 * 10^{-3}. Normal outbursts appear to be irregular, with typical occurrence times in the range 3.1 - 4.1 d. We detected a double-peaked structure of superhumps during superoutburst, with ...

  18. Optical spectroscopy of the dwarf nova U Geminorum

    CERN Document Server

    Morales-Rueda, T R

    2006-01-01

    U Gem is unique in having a direct measurement of K1 = 107 +- 2 km/s, Long et al. 1999). We present high-resolution optical spectra of the dwarf nova U Gem in quiescence taken to test the accuracy to which the HST value can be recovered from optical data. We find that, even with data of very high S/N we cannot recover Long et al.'s value to better than about 20% by any method. Contamination by neighbouring emission lines seems a likely culprit. Our data reveal a number of new features: Doppler tomograms show emission at low velocity, close to the centre of mass, and a transient, narrow absorption feature is seen in the Balmer lines near the line centres at the time of eclipse. We suggest that stellar prominences, as previously invoked for the dwarf novae IP Peg and SS Cyg in outburst, may explain both of these features. The He II 4686.75 A line emission is dominated by the gas stream/disc impact region. Two distinct spots are seen in Doppler maps, the first being very narrow and showing a velocity close to th...

  19. Cyclic Period Oscillation of the Eclipsing Dwarf Nova DV UMa

    Science.gov (United States)

    Han, Z.-T.; Qian, S.-B.; Irina, Voloshina; Zhu, L.-Y.

    2017-05-01

    DV UMa is an eclipsing dwarf nova with an orbital period of ˜2.06 hr, which lies just at the bottom edge of the period gap. To detect its orbital period changes, we present 12 new mid-eclipse times by using our CCD photometric data and archival data. The latest version of the O-C diagram, combined with the published mid-eclipse times in quiescence, and spanning ˜30 years, was obtained and analyzed. The best fit to those available eclipse timings shows that the orbital period of DV UMa is undergoing a cyclic oscillation with a period of 17.58(+/- 0.52) years and an amplitude of 71.1(+/- 6.7) s. The periodic variation most likely arises from the light-travel-time effect via the presence of a circumbinary object, because the required energy to drive the Applegate mechanism is too high in this system. The mass of the unseen companion was derived as {M}3\\sin i\\prime =0.025(+/- 0.004) {M}⊙ . If the third body is in the orbital plane (i.e., i\\prime =i=82\\buildrel{\\circ}\\over{.} 9) of the eclipsing pair, this would indicate it is a brown dwarf. This hypothetical brown dwarf is orbiting its host star at a separation of ˜8.6 au in an eccentric orbit (e = 0.44).

  20. Data Mining for Dwarf Novae in SDSS, GALEX and Astrometric Catalogues

    CERN Document Server

    Wils, Patrick; Drake, Andrew J; Southworth, John

    2009-01-01

    By cross matching blue objects from SDSS with GALEX and the astrometric catalogues USNO-B1.0, GSC2.3 and CMC14, 64 new dwarf nova candidates with one or more observed outbursts have been identified. 14 of these systems are confirmed as cataclysmic variables through existing and follow-up spectroscopy. A study of the amplitude distribution and an estimate of the outburst frequency of these new dwarf novae and those discovered by the Catalina Real-time Transient Survey (CRTS) indicates that besides systems that are faint because they are farther away, there also exists a population of intrinsically faint dwarf novae with rare outbursts.

  1. On The Nature Of Superoutbursts In Dwarf Novae

    CERN Document Server

    Truss, M R; Wynn, G A; Truss, Michael; Murray, James; Wynn, Graham

    2001-01-01

    We present the first detailed hydrodynamic simulation of a superoutburst to incorporate the full tidal potential of a binary system. A two-dimensional smoothed particle hydrodynamics code is used to simulate a superoutburst in a binary with the parameters of the SU UMa system Z Chamaeleontis. The simulated light curves shows all the features observed in such systems. Analysis of the mass flux through the disc and the growth rate of the superhumps and disc eccentricity show that the superoutburst-superhump phenomenon is a direct result of tidal instability. No enhanced mass transfer from the secondary is required to initiate or sustain these phenomena. Comparisons of superoutbursts with normal outbursts are made and we show that the model can be reconciled with the behavior of U Geminorum type dwarf novae, which show no superoutbursts.

  2. Superhumps in Cataclysmic Binaries. XXIV. Twenty More Dwarf Novae

    CERN Document Server

    Patterson, J; Kemp, J; Skillman, D R; Vanmunster, T; Harvey, D; Fried, R E; Jensen, L; Cook, L; Rea, R; Monard, B; McCormick, J; Velthuis, F; Walker, S; Martin, B; Bolt, G; Pavlenko, E P; O'Donoghue, D; Gunn, J; Novak, R; Masi, G; Garradd, G; Butterworth, N D; Krajci, T; Foote, J; Beshore, E

    2003-01-01

    We report precise measures of the orbital and superhump period in twenty more dwarf novae. For ten stars, we report new and confirmed spectroscopic periods - signifying the orbital period P_o - as well as the superhump period P_sh. These are GX Cas, HO Del, HS Vir, BC UMa, RZ Leo, KV Dra, KS UMa, TU Crt, QW Ser, and RZ Sge. For the remaining ten, we report a medley of P_o and P_sh measurements from photometry; most are new, with some confirmations of previous values. These are KV And, LL And, WX Cet, MM Hya, AO Oct, V2051 Oph, NY Ser, KK Tel, HV Vir, and RX J1155.4-5641. Periods, as usual, can be measured to high accuracy, and these are of special interest since they carry dynamical information about the binary. We still have not quite learned how to read the music, but a few things are clear. The fractional superhump excess epsilon [=(P_sh-P_o)/P_o] varies smoothly with P_o. The scatter of the points about that smooth curve is quite low, and can be used to limit the intrinsic scatter in M_1, the white dwarf ...

  3. Hubble COS Spectroscopy of the Dwarf Nova CW Mon: The White Dwarf in Quiescence?

    Science.gov (United States)

    Hause, Connor; Sion, Edward M.; Godon, Patrick; Gänsicke, Boris T.; Szkody, Paula; de Martino, Domitilla; Pala, Anna

    2017-08-01

    We present a synthetic spectral analysis of the HST COS spectrum of the U Geminorum-type dwarf nova CW Mon, taken during quiescence as part of our COS survey of accreting white dwarfs (WDs) in Cataclysmic Variables. We use a synthetic photosphere and optically thick accretion disk spectra to model the COS spectrum as well as archival IUE spectra obtained decades ago, when the system was in an even deeper quiescent state. Assuming a reddening of E(B-V) = 0.06, an inclination of 60° (CW Mon has eclipses of the accretion disk), and a WD mass of 0.8 {M}⊙ , our results indicate the presence of a 22-27,000 K WD and a low mass accretion rate \\dot{M}≲ {10}-10 {M}⊙ {{yr}}-1, for a derived distance of ˜200 to ˜300 pc. Based on observations made with the NASA-Hubble Space Telescope.

  4. The rms-flux relation in accreting white dwarfs: another nova-like variable and the first dwarf nova

    CERN Document Server

    Van de Sande, M; Knigge, C

    2015-01-01

    We report on the detection of the linear rms-flux relation in two accreting white dwarf binary systems: V1504 Cyg and KIC 8751494. The rms-flux relation relates the absolute root-mean-square (rms) variability of the light curve to its mean flux. The light curves analysed were obtained with the Kepler satellite at a 58.8 s cadence. The rms-flux relation was previously detected in only one other cataclysmic variable, MV Lyr. This result reenforces the ubiquity of the linear rms-flux relation as a characteristic property of accretion-induced variability, since it has been observed in several black hole binaries, neutron star binaries and active galactic nuclei. Moreover, its detection in V1504 Cyg is the first time the rms-flux relation has been detected in a dwarf nova-type CV during quiescence. This result, together with previous studies, hence points towards a common physical origin of accretion-induced variability, independent of the size, mass, or type of the central accreting compact object.

  5. Very high energy gamma-ray follow-up observations of novae and dwarf novae with the MAGIC telescopes

    CERN Document Server

    López-Coto, R; Bednarek, W; Desiante, R; Longo, F

    2015-01-01

    In the last few years the Fermi-LAT instrument has detected GeV gamma-ray emission from several novae. Such GeV emission can be interpreted in terms of inverse Compton emission from electrons accelerated in the shock or in terms of emission from hadrons accelerated in the same conditions. The latter might reach much higher energies and could produce a second component in the gamma-ray spectrum at TeV energies. We perform follow-up observations of selected novae and dwarf novae in search of the second component in TeV energy gamma rays. This can shed light on the acceleration process of leptons and hadrons in nova explosions. We have performed observations with the MAGIC telescopes of 3 sources, a symbiotic nova YY Her, a dwarf nova ASASSN-13ax and a classical nova V339 Del, shortly after their outbursts. We did not detect TeV gamma-ray emission from any of the objects observed. The TeV upper limits from MAGIC observations and the GeV detection by Fermi constrain the acceleration parameters for electrons and h...

  6. A Far Ultraviolet Spectroscopic Explorer Survey of High-Declination Dwarf Novae

    Science.gov (United States)

    2009-08-20

    spectroscopy (albeit of NLs alone) does not show any correlation at all ( Puebla et al. 2007). 1.3. The White Dwarf Temperature: The Case for Dwarf Novae...A. 2006, MNRAS, 368, 361 Price, A. 2006, AAN, 339, 1 Puebla , R. E., Diaz, M. P., & Hubeny, I. 2007, AJ, 134, 1923 Rappaport, S., Joss, P. C

  7. GK Per 2015 dwarf nova covered by Suzaku

    CERN Document Server

    Yuasa, Takayuki; Ishida, Manabu

    2016-01-01

    The intermediate polar GK Per exhibited a dwarf nova outburst in March-April 2015. Suzaku X-ray telescope serendipitously captured the onset of the outburst during its pre-scheduled pointing observation spanning four days. In this paper, we present temporal and spectral analysis results of this outburst, together with those from archival data of quiescent obtained in 2009 and 2014. Our temporal analysis confirmed previously reported spin modulation of X-ray count rates in outburst with a WD spin period of P_WD=351.4+/-0.5 s. The modulation is also detected in the hard X-ray band (16-60 keV), and spectral modeling of the absorption suggests obscuration by a dense absorption with a line-of-sight column density of N_H>10^23 cm^-2. A complex time evolution of spin modulation profiles is seen; the spin minimum phase shifts from phase ~0.25 in the first half of the observation to ~0.65 in the second one, and the pulse shape significantly changes epoch by epoch. Spectral fitting in the Fe Kalpha band revealed an inc...

  8. Superhumps in the Rarely Outbursting SU UMa-Type Dwarf Nova, HO Delphini

    CERN Document Server

    Kato, T; Moilanen, M; Yamaoka, H

    2003-01-01

    We observed the 1994, 1996 and 2001 outbursts of HO Del. From the detection of secure superhumps, HO Del is confirmed to be an SU UMa-type dwarf nova with a superhump period of 0.06453(6) d. Based on the recent observations and the past records, the outbursts of HO Del are found to be relatively rare, with the shortest intervals of superoutbursts being ~740 d. Among SU UMa-type dwarf novae with similar outburst intervals, the outburst amplitude (~5.0 mag) is unusually small. HO Del showed a rather rapid decay of the superhump amplitudes, and no regrowth of the amplitudes during the later stage, in contrast to the commonly observed behavior in SU UMa-type dwarf novae with long outburst intervals. We positively identified HO Del with a ROSAT X-ray source, and obtained a relatively large X-ray luminosity of 10^(31.1+/-0.2) erg/s. We also performed a literature survey of SU UMa-type dwarf novae, and presented a new set of basic statistics. The SU UMa-type dwarf novae with a brightening trend or with a regrowth of...

  9. Superoutburst of a New Sub-Period-Minimum Dwarf Nova CSS130418 in Hercules

    Directory of Open Access Journals (Sweden)

    D. Chochol

    2015-02-01

    Full Text Available Multicolour photometry of a new dwarf nova CSS130418 in Hercules, which underwent superoutburst on April 18, 2013, allow to classified it as a WZ Sge-type dwarf nova. The phase light curves for different stages of superoutburst are presented. The early superhumps were used to determine the orbital period Porb = 64.84(1 minutes, which is shorter than the period minimum ~78 minutes for normal hydrogen-rich cataclysmic variables. We found the mean period of ordinary superhumps Psh = 65.559(1 minutes. The quiescent spectrum is rich in helium, showing double peaked emissionlines of H I and He I from accretion disk, so the dwarf nova is in a late stage of stellar evolution.

  10. VizieR Online Data Catalog: New Dwarf novae in SDSS, GALEX and astrom. cat. (Wils+, 2010)

    Science.gov (United States)

    Wils, P.; Gansicke, B. T.; Drake, A. J.; Southworth, J.

    2015-07-01

    Here, we cross-match a number of large surveys to find faint outbursting dwarf novae, and make use of CRTS light curves to compare the properties of the previously known dwarf novae, those identified spectroscopically by SDSS, and the ones discovered in this paper. (3 data files).

  11. Superhumps in the Rarely Outbursting SU UMa-Type Dwarf Nova, HO Delphini

    OpenAIRE

    Kato, T.; Nogami, D.; Moilanen, M. (Miika); Yamaoka, H.

    2003-01-01

    We observed the 1994, 1996 and 2001 outbursts of HO Del. From the detection of secure superhumps, HO Del is confirmed to be an SU UMa-type dwarf nova with a superhump period of 0.06453(6) d. Based on the recent observations and the past records, the outbursts of HO Del are found to be relatively rare, with the shortest intervals of superoutbursts being ~740 d. Among SU UMa-type dwarf novae with similar outburst intervals, the outburst amplitude (~5.0 mag) is unusually small. HO Del showed a r...

  12. An International Ultraviolet Explorer Archival Study of Dwarf Novae in Outburst

    Science.gov (United States)

    Hamilton, Ryan T.; Urban, Joel A.; Sion, Edward M.; Riedel, Adric R.; Voyer, Elysse N.; Marcy, John T.; Lakatos, Sarah L.

    2007-10-01

    We present a synthetic spectral analysis of nearly the entire far-ultraviolet International Ultraviolet Explorer (IUE) archive of spectra of dwarf novae in or near outburst. The study includes 46 systems of all dwarf nova subtypes, both above and below the period gap. The spectra were uniformly analyzed using synthetic spectral codes for optically thick accretion disks and stellar photospheres, along with the best available distance measurements or estimates. We present newly estimated accretion rates and discuss the implications of our study for disk accretion physics and CV evolution.

  13. An International Ultraviolet Explorer Archival Study of Dwarf Novae in Outburst

    CERN Document Server

    Hamilton, Ryan T; Sion, Edward M; Riedel, Adric R; Voyer, Elysse N; Marcy, John T; Lakatos, Sarah L

    2007-01-01

    We present a synthetic spectral analysis of nearly the entire far ultraviolet International Ultraviolet Explorer (IUE) archive of spectra of dwarf novae in or near outburst. The study includes 46 systems of all dwarf nova subtypes both above and below the period gap. The spectra were uniformly analyzed using synthetic spectral codes for optically thick accretion disks and stellar photospheres along with the best-available distance measurements or estimates. We present newly estimated accretion rates and discuss the implications of our study for disk accretion physics and CV evolution.

  14. Mass transfer in cataclysmic variables - Clues from the dwarf nova period distribution

    Science.gov (United States)

    Shafter, A. W.; Wheeler, J. C.; Cannizzo, J. K.

    1986-01-01

    Evidence is presented in support of the hypothesis that the mean mass-transfer rate at a given orbital period is not continuous across the 2-3 hr gap in the orbital period distribution for cataclysmic variables. It is pointed out that although dwarf novae comprise nearly half (48 percent) of all disk systems with orbital periods less than 10 hr, only three systems out of the 22 with periods between 3 and 4 hr appear to be dwarf novae. The overall orbital period distribution for dwarf novae in conjunction with the predictions from current theories of dwarf nova eruptions are used to argue that mass-transfer rates must be generally higher for systems with orbital periods greater than 3 hr relative to systems with periods less than 2 hr. It is further argued that the mean mass-transfer rate at a given orbital period cannot increase more steeply than P exp 1.7 unless the white dwarf mass is positively correlated with orbital period.

  15. Very-high-energy {\\gamma}-ray observations of novae and dwarf novae with the MAGIC telescopes

    CERN Document Server

    Ahnen, M L; Antonelli, L A; Antoranz, P; Babic, A; Banerjee, B; Bangale, P; de Almeida, U Barres; Barrio, J A; González, J Becerra; Bednarek, W; Bernardini, E; Biasuzzi, B; Biland, A; Blanch, O; Bonnefoy, S; Bonnoli, G; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Chatterjee, A; Clavero, R; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; De Lotto, B; Wilhelmi, E de Oña; Mendez, C Delgado; Di Pierro, F; Prester, D Dominis; Dorner, D; Doro, M; Einecke, S; Glawion, D Eisenacher; Elsaesser, D; Fernández-Barral, A; Fidalgo, D; Fonseca, M V; Font, L; Frantzen, K; Fruck, C; Galindo, D; López, R J García; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Giammaria, P; Godinović, N; Muñoz, A González; Guberman, D; Hanabata, Y; Hayashida, M; Herrera, J; Hose, J; Hrupec, D; Hughes, G; Idec, W; Kellermann, H; Kodani, K; Konno, Y; Kubo, H; Kushida, J; La Barbera, A; Lelas, D; Lewandowska, N; Lindfors, E; Lombardi, S; Longo, F; López, M; López-Coto, R; López-Oramas, A; Lorenz, E; Majumdar, P; Makariev, M; Mallot, K; Maneva, G; Manganaro, M; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martínez, M; Mazin, D; Menzel, U; Miranda, J M; Mirzoyan, R; Moralejo, A; Nakajima, D; Neustroev, V; Niedzwiecki, A; Rosillo, M Nievas; Nilsson, K; Nishijima, K; Noda, K; Orito, R; Overkemping, A; Paiano, S; Palacio, J; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Paredes-Fortuny, X; Persic, M; Poutanen, J; Moroni, P G Prada; Prandini, E; Puljak, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Garcia, J Rodriguez; Saito, T; Saito, K; Satalecka, K; Scapin, V; Schultz, C; Schweizer, T; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Stamerra, A; Steinbring, T; Strzys, M; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzić, T; Tescaro, D; Teshima, M; Thaele, J; Torres, D F; Toyama, T; Treves, A; Verguilov, V; Vovk, I; Will, M; Zanin, R; Desiante, R; Hays, E

    2015-01-01

    Context. In the last five years the Fermi Large Area Telescope (LAT) instrument detected GeV {\\gamma}-ray emission from five novae. The GeV emission can be interpreted in terms of an inverse Compton process of electrons accelerated in a shock. In this case it is expected that protons in the same conditions can be accelerated to much higher energies. Consequently they may produce a second component in the {\\gamma}-ray spectrum at TeV energies. Aims. We aim to explore the very-high-energy domain to search for {\\gamma}-ray emission above 50 GeV and to shed light on the acceleration process of leptons and hadrons in nova explosions. Methods. We have performed observations with the MAGIC telescopes of the classical nova V339 Del shortly after the 2013 outburst, triggered by optical and subsequent GeV {\\gamma}-ray detec- tions. We also briefly report on VHE observations of the symbiotic nova YY Her and the dwarf nova ASASSN-13ax. We complement the TeV MAGIC observations with the analysis of con- temporaneous Fermi-...

  16. RZ Leonis Minoris bridging between ER Ursae Majoris-type dwarf nova and nova-like system

    Science.gov (United States)

    Kato, Taichi; Ishioka, Ryoko; Isogai, Keisuke; Kimura, Mariko; Imada, Akira; Miller, Ian; Masumoto, Kazunari; Nishino, Hirochika; Kojiguchi, Naoto; Kawabata, Miho; Sakai, Daisuke; Sugiura, Yuki; Furukawa, Hisami; Yamamura, Kenta; Kobayashi, Hiroshi; Matsumoto, Katsura; Wang, Shiang-Yu; Chou, Yi; Ngeow, Chow-Choong; Chen, Wen-Ping; Panwar, Neelam; Lin, Chi-Sheng; Hsiao, Hsiang-Yao; Guo, Jhen-Kuei; Lin, Chien-Cheng; Omarov, Chingis; Kusakin, Anatoly; Krugov, Maxim; Starkey, Donn R.; Pavlenko, Elena P.; Antonyuk, Kirill A.; Sosnjvskij, Aleksei A.; Antonyuk, Oksana I.; Pit, Nikolai V.; Baklanov, Alex V.; Babina, Julia V.; Itoh, Hiroshi; Padovan, Stefano; Akazawa, Hidehiko; Kafka, Stella; de Miguel, Enrique; Pickard, Roger D.; Kiyota, Seiichiro; Shugarov, Sergey Yu.; Chochol, Drahomir; Krushevska, Viktoriia; Sekeráš, Matej; Pikalova, Olga; Sabo, Richard; Dubovsky, Pavol A.; Kudzej, Igor; Ulowetz, Joseph; Dvorak, Shawn; Stone, Geoff; Tordai, Tamás; Dubois, Franky; Logie, Ludwig; Rau, Steve; Vanaverbeke, Siegfried; Vanmunster, Tonny; Oksanen, Arto; Maeda, Yutaka; Kasai, Kiyoshi; Katysheva, Natalia; Morelle, Etienne; Neustroev, Vitaly V.; Sjoberg, George

    2016-12-01

    We observed RZ LMi, which is renowned for its extremely short (˜19 d) supercycle and is a member of a small, unusual class of cataclysmic variables called ER UMa-type dwarf novae, in 2013 and 2016. In 2016, the supercycles of this object substantially lengthened in comparison to the previous measurements to 35, 32, and 60 d for three consecutive superoutbursts. We consider that the object virtually experienced a transition to the nova-like state (permanent superhumper). This observed behavior reproduced the prediction of the thermal-tidal instability model extremely well. We detected a precursor in the 2016 superoutburst and detected growing (stage A) superhumps with a mean period of 0.0602(1) d in 2016 and in 2013. Combined with the period of superhumps immediately after the superoutburst, the mass ratio is not as small as in WZ Sge-type dwarf novae, having orbital periods similar to RZ LMi. By using least absolute shrinkage and selection operator (Lasso) two-dimensional power spectra, we detected possible negative superhumps with a period of 0.05710(1) d. We estimated an orbital period of 0.05792 d, which suggests a mass ratio of 0.105(5). This relatively large mass ratio is even above that of ordinary SU UMa-type dwarf novae, and it is also possible that the exceptionally high mass-transfer rate in RZ LMi may be a result of a stripped secondary with an evolved core in a system evolving toward an AM CVn-type object.

  17. Investigating the Sources of Flickering and Superhumps in the Dwarf Nova V4140 Sgr

    Science.gov (United States)

    Baptista, R.; Borges, B.; Oliveira, A.

    2012-04-01

    We report the results of maximum entropy eclipse-mapping analysis of an ensemble of light curves of the dwarf nova V4140 Sagitarii (V4140 Sgr) with the objective of studying the spatial distribution of its steady-light and flickering sources in quiescence, and the changing disk structure during an outburst.

  18. Phase-resolved spectroscopy of the helium dwarf nova `SN 2003aw' in quiescence

    NARCIS (Netherlands)

    Roelofs, G.H.A.; Groot, P.J.; Marsh, T.R.; Steeghs, D.; Nelemans, G.

    2006-01-01

    High time resolution spectroscopic observations of the ultracompact helium dwarf nova `SN2003aw' in its quiescent state at V~ 20.5 reveal its orbital period at 2027.8 +/- 0.5 s or 33.80 min. Together with the photometric `superhump' period of 2041.5 +/- 0.5 s, this implies a mass ratio q~ 0.036. We

  19. The Shape of Long Outbursts in U Gem Type Dwarf Novae from AAVSO Data

    Science.gov (United States)

    Cannizzo, John K.

    2012-01-01

    We search the American Association of Variable Star Observers (AAVSO) archives of the two best studied dwarf novae in an attempt to find light curves for long out bursts that are extremely well-characterized. The systems are U Gem and S8 Cyg. Our goal is to search for embedded precursors such as those that have been found recently in the high fidelity Kepler data for superoutbursts of some members of the 8U UMa subclass of dwarf novae. For the vast majority of AAV80 data, the combination of low data cadence and large errors associated with individual measurements precludes one from making any strong statement about the shape of the long outbursts. However, for a small number of outbursts, extensive long term monitoring with digital photometry yields high fidelity light curves. We report the finding of embedded precursors in two of three candidate long outbursts. This reinforces van Paradijs' finding that long outbursts in dwarf novae above the period gap and superoutbursts in systems below the period gap constitute a unified class. The thermal-tidal instability to account for superoutbursts in the SU UMa stars predicts embedded precursors only for short orbital period dwarf novae, therefore the presence of embedded precursors in long orbital period systems - U Gem and SS Cyg - argues for a more general mechanism to explain long outbursts.

  20. Inner Disk Structure of Dwarf Novae in the Light of X-Ray Observations

    Directory of Open Access Journals (Sweden)

    S. Balman

    2015-02-01

    Full Text Available Diversity of the X-ray observations of dwarf nova are still not fully understood. I review the X-ray spectral characteristics of dwarf novae during the quiescence in general explained by cooling flow models and the outburst spectra that show hard X-ray emission dominantly with few sources that reveal soft X-ray/EUV blackbody emission. The nature of aperiodic time variability of brightness of dwarf novae shows band limited noise, which can be adequately described in the framework of the model of propagating fluctuations. The frequency of the break (1-6 mHz indicates inner disk truncation of the optically thick disk with a range of radii (3.0-10.0×109 cm. The RXTE and optical (RTT150 data of SS Cyg in outburst and quiescence reveal that the inner disk radius moves towards the white dwarf and receeds as the outburst declines to quiescence. A preliminary analysis of SU UMa indicates a similar behaviour. In addition, I find that the outburst spectra of WZ Sge shows two component spectrum of only hard X-ray emission, one of which may be fitted with a power law suggesting thermal Comptonization occuring in the system. Cross-correlations between the simultaneous UV and X-ray light curves (XMM −Newton of five DNe in quiescence show time lags in the X-rays of 96-181 sec consistent with travel time of matter from a truncated inner disk to the white dwarf surface. All this suggests that dwarf novae and other plausible nonmagnetic systems have truncated accretion disks indicating that the disks may be partially evaporated and the accretion may occur through hot (coronal flows in the disk.

  1. Inner Disk Structure of Dwarf Novae in the Light of X-ray Observations

    CERN Document Server

    Balman, S

    2014-01-01

    Diversity of the X-ray observations of dwarf nova are still not fully understood. I review the X-ray spectral characteristics of dwarf novae during the quiescence in general explained by cooling flow models and the outburst spectra that show hard X-ray emission dominantly with few sources that reveal soft X-ray/EUV blackbody emission. The nature of aperiodic time variability of brightness of dwarf novae shows band limited noise, which can be adequately described in the framework of the model of propagating fluctuations. The frequency of the break (1-6 mHz) indicates inner disk truncation of the optically thick disk with a range of radii (3.0-10.0)$\\times$10$^{9}$ cm. The RXTE and optical (RTT150) data of SS Cyg in outburst and quiescence reveal that the inner disk radius moves towards the white dwarf and receeds as the outburst declines to quiescence. A preliminary analysis of SU UMa indicates a similar behaviour. In addition, I find that the outburst spectra of WZ Sge shows two component spectrum of only har...

  2. SDSS J102146.44+234926.3: New WZ Sge-type dwarf nova

    CERN Document Server

    Golovin, Alex; Pavlenko Elena P; Tom, Krajci; Yuliana, Kuznyetsova; Arne, Henden; Victoria, Krushevska; Shawn, Dvorak; Kirill, Sokolovsky; Sergeeva Tatyana P; Robert, James; Tim, Crawford; Laurent, Corp

    2007-01-01

    We report CCD photometry and spectroscopy during 2006 outburst of the dwarf nova SDSS J102146.44+234926.3 (SDSS J1021). The photographic plates from the MAO, SAI and CrAO plate archives, which cover the position of the SDSS J1021, were inspected for the presence of previous outbursts. We also present the BVRcIc photometric calibration of 52 stars in SDSS J1021 vicinity, which have V-magnitude in the range of 11.21-17.23m and can serve as comparison stars. The large amplitude of the SDSS J1021 outburst of 7m, superhumps with a period below the ''period gap'', rebrightening during the declining stage of superoutburst, rarity of outbursts and obtained spectrum allow to classify this object as a WZ Sge type dwarf nova.

  3. Statistical properties of dwarf novae-type cataclysmic variables: The Outburst Catalogue

    CERN Document Server

    Coppejans, Deanne L; Knigge, Christian; Pretorius, Margaretha L; Woudt, Patrick A; Groot, Paul J; Van Eck, Cameron L; Drake, Andrew J

    2015-01-01

    The Outburst Catalogue contains a wide variety of observational properties for 722 dwarf nova-type (DN) cataclysmic variables (CVs) and 309 CVs of other types from the Catalina Real-time Transient Survey. In particular, it includes the apparent outburst and quiescent V-band magnitudes, duty cycles, limits on the recurrence time, upper- and lower-limits on the distance and absolute quiescent magnitudes, colour information, orbital parameters, and X-ray counterparts. These properties were determined by means of a classification script presented in this paper. The DN in the catalogue show a correlation between the outburst duty cycle and the orbital period (and outburst recurrence time), as well as between the quiescent absolute magnitude and the orbital period (and duty cycle). This is the largest sample of dwarf nova properties collected to date. Besides serving as a useful reference for individual systems and a means of selecting objects for targeted studies, it will prove valuable for statistical studies tha...

  4. Beacons In the Dark: Using Novae and Supernovae to Detect Dwarf Galaxies in the Local Universe

    CERN Document Server

    Conroy, Charlie

    2015-01-01

    We propose that luminous transients, including novae and supernovae, can be used to detect the faintest galaxies in the universe. Beyond a few Mpc, dwarf galaxies with stellar masses $<10^6 M_{\\odot}$ will likely be too faint and/or too low in surface brightness to be directly detected in upcoming large area ground-based photometric surveys. However, single epoch LSST photometry will be able to detect novae to distances of $\\sim30$ Mpc and SNe to Gpc-scale distances. Depending on the form of the stellar mass-halo mass relation and the underlying star formation histories of low mass dwarfs, the expected nova rates will be a few to $\\sim100$ yr$^{-1}$ and the expected SN rates (including both type Ia and core-collapse) will be $\\sim10^2-10^4$ within the observable ($4\\pi$ sr) volume. The transient rate associated with intrahalo stars will be comparably large, but these transients will be located close to bright galaxies, in contrast to the dwarfs, which should trace the underlying large scale structure of th...

  5. Clearing the Gas from Globular Clusters & Dwarf Spheroidals with Classical Novae

    CERN Document Server

    Moore, Kevin

    2010-01-01

    Observations of the intra-cluster medium (ICM) in galactic globular clusters (GCs) show a systematic deficiency in ICM mass as compared to that expected from accumulation of stellar winds in the time available between galactic plane crossings. In this paper, we reexamine the original hypothesis of Scott and Durisen that hydrogen-rich explosions on accreting white dwarfs, classical novae (CNe), will sweep out the ICM from the cluster more frequently than galactic plane crossings. From the CNe rate and stellar mass-loss rate, this clearing mechanism predicts that ~ 0.03 M_sun should be present in 5x10^5 M_sun) GCs. We find that nova shells are effective at clearing the ICM in low-mass GCs (<= 10^5 M_sun), whereas higher-mass clusters may experience a quiescent time between novae long enough to prevent the next nova shell from escaping. The nova clearing mechanism will also operate in ultra-faint Milky Way satellites, where many upper limits on gas masses are available.

  6. Hydrodynamic Studies of the Evolution of Recurrent, Symbiotic, and Dwarf Novae: The White Dwarf Components are Growing in Mass

    CERN Document Server

    Starrfield, S; Iliadis, C; Hix, W R; Arnett, W D; Meakin, C; Sparks, W M

    2012-01-01

    Symbiotic binaries are systems containing white dwarfs (WDs) and red giants. Symbiotic novae are those systems in which thermonuclear eruptions occur on the WD components. These are to be distinguished from events driven by accretion disk instabilities analogous to dwarf novae eruptions in cataclysmic variable outbursts. Another class of symbiotic systems are those in which the WD is extremely luminous and it seems likely that quiescent nuclear burning is ongoing on the accreting WD. A fundamental question is the secular evolution of the WD. Do the repeated outbursts or quiescent burning in these accreting systems cause the WD to gain or lose mass? If it is gaining mass, can it eventually reach the Chandrasekhar Limit and become a supernova (a SN Ia if it can hide the hydrogen and helium in the system)? In order to better understand these systems, we have begun a new study of the evolution of Thermonuclear Runaways (TNRs) in the accreted envelopes of WDs using a variety of initial WD masses, luminosities and ...

  7. Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae. III: The Third Year (2010--2011)

    CERN Document Server

    Kato, Taichi; Miller, Ian; Ohshima, Tomohito; de Miguel, Enrique; Tanabe, Kenji; Imamura, Kazuyoshi; Akazawa, Hidehiko; Kunitomi, Nanae; Takagi, Ryosuke; Nose, Mikiha; Hambsch, Franz-Josef; Kiyota, Seiichiro; Pavlenko, Elena P; Baklanov, Aleksei V; Antonyuk, Oksana I; Samsonov, Denis; Sosnovskij, Aleksei; Antonyuk, Kirill; Andreev, Maksim V; Morelle, Etienne; Dubovsky, Pavol A; Kudzej, Igor; Oksanen, Arto; Masi, Gianluca; Krajci, Thomas; Pickard, Roger D; Sabo, Richard; Itoh, Hiroshi; Stein, William; Dvorak, Shawn; Henden, Arne; Nakagawa, Shinichi; Noguchi, Ryo; Iino, Eriko; Matsumoto, Katsura; Nishitani, Hiroki; Aoki, Tomoya; Kobayashi, Hiroshi; Akasaka, Chihiro; Ruiz, Javier; Shugarov, Sergey Yu; Chochol, Drahomir; Parakhin, Nikolai A; Monard, Berto; Shiokawa, Kazuhiko; Kasai, Kiyoshi; Staels, Bart; Miyashita, Atsushi; Starkey, Donn R; Ogmen, Yenal; Littlefield, Colin; Katysheva, Natalia; Sergey, Ivan M; Denisenko, Denis; Tordai, Tamas; Fidrich, Robert; Goranskij, Vitaly P; Virtanen, Jani; Crawford, Tim; Pietz, Jochen; Boyd, David; Brady, Steve; James, Nick; Goff, William N; Itagaki, Koh-ichi; Nishimura, Hideo; Nakashima, Youichirou; Yoshida, Seiichi; Stubbings, Rod; Poyner, Gary; Maeda, Yutaka; Korotkiy, Stanislav; Sokolovsky, Kirill V; Ueda, Seiji

    2011-01-01

    Continuing the project described by Kato et al. (2009, PASJ 61, S395, arXiv:0905.1757), we collected times of superhump maxima for 51 SU UMa-type dwarf novae mainly observed during the 2010-2011 season. Although most of the new data for systems with short superhump periods basically confirmed the findings by Kato et al. (2009) and Kato et al. (2010, PASJ 62, 1525, arXiv:1009.5444), the long-period system GX Cas showed an exceptionally large positive period derivative. An analysis of public Kepler data of V344 Lyr and V1504 Cyg yielded less striking stage transitions. In V344 Lyr, there was prominent secondary component growing during the late stage of superoutbursts, and the component persisted at least for two more cycles of successive normal outbursts. We also investigated the superoutbursts of two conspicuous eclipsing objects: HT Cas and the WZ Sge-type object SDSS J080434.20+510349.2. Strong beat phenomena were detected in both objects, and late-stage superhumps in the latter object had an almost constan...

  8. MN Dra - In-the-Gap Dwarf Nova With Negative Superhumps

    CERN Document Server

    Pavlenko, Elena; Andreev, Max; Sklyanov, Alexandr; Zubareva, Alexandra; Samsonov, Denis; Voloshina, Irina; Metlov, Vladimir; Shugarov, Sergey; Parakhin, Nikolay; Golovin, Alex; Antoniuk, Oksana

    2011-01-01

    The multi-site photometric observations of MN Dra were made over 77 nights in August-November, 2009. The total exposure was 433 hours. During this time the binary underwent two superoutbursts and five normal outbursts. During the course of first superoutburst period of positive superhumps decreased with extremely large $\\dot P = -1.5 \\times 1.0^{-4}$ for SU UMa-like dwarf novae, confirming known behavior of MN Dra [1]. Between the superoutbursts MN Dra displayed negative superhumps. Their period changed cyclically around 0.096-day value.

  9. The Eclipsing Cataclysmic Variable Lanning 386: Dwarf Nova, SW Sextantis Star, or Both?

    OpenAIRE

    Brady, S; Thorstensen, J.R.; Koppelman, M. D.; Prieto, J. L.; Garnavich, P. M.; Hirschauer, A.; Florack, M.

    2008-01-01

    We present photometry and spectroscopy of the suspected cataclysmic variable (CV) Lanning 386. We confirm that it is a CV, and observe deep eclipses, from which we determine the orbital period Porb to be 0.1640517 +- 0.0000001 d (= 3.94 h). Photometric monitoring over two observing seasons shows a very active system with frequent outbursts of variable amplitude, up to approx. 2 mag. The spectrum in quiescence is typical of dwarf novae, but in its high state the system shows strong HeII emissi...

  10. Short-term variability of dwarf nova SS Cyg during outbursts

    Energy Technology Data Exchange (ETDEWEB)

    Voloshina, I; Metlov, V; Rovithis-Livaniou, H, E-mail: vib@sai.msu.r [Section of Astrophysics, Astronomy and Mechanics, Department of Physics, Athens University, Zagrafos 15784, Athens (Greece)

    2009-06-01

    Here we report the results of CCD observations of classical dwarf nova SS Cyg carried out with the two 60-cm telescopes in Crimea during the last years. These observations cover a few outbursts in 2006, 2007 and 2008. Power spectrum analysis of our CCD data clearly shows the existence of rapid periodic oscillations in the light curve of SS Cyg at the stage of decline after maximum. CCD observations of SS Cyg in autumn 2006 outburst revealed oscillations with the two periods 10 s and 76 s, in November 2007 - with 41 s period and in January 2008 with 98 s. We interpret detected variations as quasi-periodic oscillations.

  11. Viscous evolution of accretion discs in the quiescence of dwarf novae

    Science.gov (United States)

    Mineshige, Shin; Wood, Janet H.

    1989-01-01

    Viscous evolution of accretion disks in the quiescence of dwarf novae is investigated semi-analytically. There are two key factors: the inward flow of the initial mass in the disk and the diffusion of the material added into the disk. The results are compared with the brightness temperature distributions obtained by the eclipse mapping of Z Cha and OY Car. The functional form of the viscosity parameter a, its values, the types of outbursts, and the application to soft X-ray transients are discussed.

  12. Viscous evolution of accretion discs in the quiescence of dwarf novae

    Energy Technology Data Exchange (ETDEWEB)

    Mineshige, Shin (Texas Univ., Austin, TX (USA). Dept. of Astronomy); Wood, J.H. (Texas Univ., Austin, TX (USA). Dept. of Astronomy Cambridge Univ. (UK). Inst. of Astronomy)

    1989-11-15

    Viscous evolution of accretion discs in the quiescence of dwarf novae is investigated semi-analytically. There are two key factors: the inward flow of the initial mass in the disc and the diffusion of the material added into the disc. The results are compared with the brightness temperature distributions obtained by the eclipse mapping of Z Cha and OY Car. The functional form of the viscosity parameter, its values, the types of outbursts, and the application to soft X-ray transients are discussed. (author).

  13. X-ray and UV observations of the dwarf nova VW Hyi in quiescence

    CERN Document Server

    Pandel, D; Howell, S B; Pandel, Dirk; Cordova, France A.; Howell, Steve B.

    2003-01-01

    We present an analysis of X-ray and ultra-violet data of the dwarf nova VW Hyi that were obtained with XMM-Newton during the quiescent state. The X-ray spectrum indicates the presence of an optically thin plasma in the boundary layer that cools as it settles onto the white dwarf. The plasma has a continuous temperature distribution that is well described by a power-law or a cooling flow model with a maximum temperature of 6-8 keV. We estimate from the X-ray spectrum a boundary layer luminosity of 8*10^30 erg/s, which is only 20 per cent of the disk luminosity. The rate of accretion onto the white dwarf is 5*10^-12 solar masses per year, about half of the rate in the disk. From the high-resolution X-ray spectra, we estimate that the X-ray emitting part of the boundary layer is rotating with a velocity of 540 km/s, which is close the rotation velocity of the white dwarf but significantly smaller than the Keplerian velocity. We detect a 60-s quasi-periodic oscillation of the X-ray flux that is likely due to the ...

  14. Accurate Pre-Eruption and Post-Eruption Orbital Periods for the Dwarf/Classical Nova V1017 Sgr

    CERN Document Server

    Salazar, Irene V; Schaefer, Bradley E; Landolt, Arlo U; Dvorak, Shawn

    2016-01-01

    V1017 Sgr is a classical nova (in 1919) that displayed an earlier dwarf nova eruption (in 1901), and two more dwarf nova events (in 1973 and 1991). Previous work on this bright system in quiescence (V=13.5) has only been a few isolated magnitudes, a few spectra, and an ambiguous claim for an orbital period of 5.714 days as based on nine radial velocities. To test this period, we have collected 2896 magnitudes (plus 53 in the literature) in the UBVRIJHKL bands from 1897 to 2016, making an essentially complete photometric history of this unique cataclysmic variable. We find that the light curve in all bands is dominated by the ellipsoidal modulations of a G giant companion star, with a post-eruption (after the 1919 nova event) orbital period of 5.786290 +- 0.000032 days. This is the longest period for any classical nova, the accretion must be powered by the nuclear evolution of the companion star, and the dwarf nova events occur only because the outer parts of the large disk are cool enough to be unstable. Furt...

  15. Curious Variables Experiment (CURVE). Superhump Period Change Pattern in KS UMa and Other Dwarf Novae

    CERN Document Server

    Olech, A; Kedzierski, P; Zloczewski, K; Mularczyk, K; Wisniewski, M

    2003-01-01

    We report extensive photometry of the dwarf nova KS UMa throughout its 2003 superoutburst till quiescence. During the superoutburst the star displayed clear superhumps with a mean period of Psh = 0.070092(23) days. In the middle stage of superoutburst the period was increasing with a rate of $dot P/P = (21pm12)times 10^{-5}$ and later was decreasing with a rate of $dot P/P = -(21pm8)times 10^{-5}$. At the end of superoutburst and during first dozen days of quiescence the star was showing late superhumps with a mean period of Plate = 0.06926(2) days. This phenomenon was observed even 30 days after beginning of the superoutburst. In quiescence the star shows quasi-periodic modulations with amplitude reaching 0.5 mag. The most common structure observed during this stage was sinusoidal wave characterized by a period of about 0.1 days. Comparing KS UMa to other SU UMa stars we conclude that this group of dwarf novae shows decreasing superhump periods at the beginning and the end of superoutburst but increasing per...

  16. RZ Leonis Minoris Bridging between ER Ursae Majoris-Type Dwarf Nova and Novalike System

    CERN Document Server

    Kato, Taichi; Isogai, Keisuke; Kimura, Mariko; Imada, Akira; Miller, Ian; Masumoto, Kazunari; Nishino, Hirochika; Kojiguchi, Naoto; Kawabata, Miho; Sakai, Daisuke; Sugiura, Yuki; Furukawa, Hisami; Yamamura, Kenta; Kobayashi, Hiroshi; Matsumoto, Katsura; Wang, Shiang-Yu; Chou, Yi; Ngeow, Chow-Choong; Chen, Wen-Ping; Panwar, Neelam; Lin, Chi-Sheng; Hsiao, Hsiang-Yao; Guo, Jhen-Kuei; Lin, Chien-Cheng; Omarov, Chingis; Kusakin, Anatoly; Krugov, Maxim; Starkey, Donn R; Pavlenko, Elena P; Antonyuk, Kirill A; Sosnjvskij, Aleksei A; Antonyuk, Oksana I; Pit, Nikolai V; Baklanov, Alex V; Babina, Julia V; Itoh, Hiroshi; Padovan, Stefano; Akazawa, Hidehiko; Kafka, Stella; de Miguel, Enrique; Pickard, Roger D; Kiyota, Seiichiro; Shugarov, Sergey Yu; Chochol, Drahomir; Krushevska, Viktoriia; Sekeras, Matej; Pikalova, Olga; Sabo, Richard; Dubovsky, Pavol A; Kudzej, Igor; Ulowetz, Joseph; Dvorak, Shawn; Stone, Geoff; Tordai, Tamas; Dubois, Franky; Logie, Ludwig; Rau, Steve; Vanaverbeke, Siegfried; Vanmunster, Tonny; Oksanen, Arto; Maeda, Yutaka; Kasai, Kiyoshi; Katysheva, Natalia; Morelle, Etienne; Neustroev, Vitaly V; Sjoberg, George

    2016-01-01

    We observed RZ LMi, which is renowned for the extremely (~19d) short supercycle and is a member of a small, unusual class of cataclysmic variables called ER UMa-type dwarf novae, in 2013 and 2016. In 2016, the supercycles of this object substantially lengthened in comparison to the previous measurements to 35, 32, 60d for three consecutive superoutbursts. We consider that the object virtually experienced a transition to the novalike state (permanent superhumper). This observed behavior extremely well reproduced the prediction of the thermal-tidal instability model. We detected a precursor in the 2016 superoutburst and detected growing (stage A) superhumps with a mean period of 0.0602(1)d in 2016 and in 2013. Combined with the period of superhumps immediately after the superoutburst, the mass ratio is not as small as in WZ Sge-type dwarf novae, having orbital periods similar to RZ LMi. By using least absolute shrinkage and selection operator (Lasso) two-dimensional power spectra, we detected possible negative ...

  17. Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae

    CERN Document Server

    Kato, Taichi; Uemura, Makoto; Nogami, Daisaku; Maehara, Hiroyuki; Ishioka, Ryoko; Baba, Hajime; Matsumoto, Katsura; Iwamatsu, Hidetoshi; Kubota, Kaori; Sugiyasu, Kei; Soejima, Yuichi; Moritani, Yuuki; Ohshima, Tomohito; Ohashi, Hiroyuki; Tanaka, Junpei; Sasada, Mahito; Arai, Akira; Nakajima, Kazuhiro; Kiyota, Seiichiro; Tanabe, Kenji; Imamura, Kayuyoshi; Kunitomi, Nanae; Kunihiro, Kenji; Taguchi, Hiroki; Koizumi, Mitsuo; Yamada, Norimi; Nishi, Yuichi; Kida, Mayumi; Tanaka, Sawa; Ueoka, Rie; Yasui, Hideki; Maruoka, Koichi; Henden, Arne; Oksanen, Arto; Moilanen, Marko; Tikkanen, Petri; Aho, Mika; Monard, Berto; Itoh, Hiroshi; Dubovsky, Pavol A; Kudzej, Igor; Dancikova, Radka; Vanmunster, Tonny; Pietz, Jochen; Bolt, Greg; Boyd, David; Nelson, Peter; Krajci, Thomas; Cook, Lewis M; Torii, Ken'ichi; Starkey, Donn R; Shears, Jeremy; Jensen, Lasse-Teist; Masi, Gianluca; Novak, Rudolf; Hynek, Tomas; Kocian, Radek; Kral, Lukas; Kucakova, Hana; Kolasa, Marek; Stastny, Petr; Staels, Bart

    2009-01-01

    We systematically surveyed period variations of superhumps in SU UMa-type dwarf novae based on newly obtained data and past publications. In many systems, the evolution of superhump period are found to be composed of three distinct stages: early evolutionary stage with a longer superhump period, middle stage with systematically varying periods, final stage with a shorter, stable superhump period. During the middle stage, many systems with superhump periods less than 0.08 d show positive period derivatives. Contrary to the earlier claim, we found no clear evidence for variation of period derivatives between superoutburst of the same object. We present an interpretation that the lengthening of the superhump period is a result of outward propagation of the eccentricity wave and is limited by the radius near the tidal truncation. We interprete that late stage superhumps are rejuvenized excitation of 3:1 resonance when the superhumps in the outer disk is effectively quenched. Many of WZ Sge-type dwarf novae showed...

  18. Mass transfer variation in the outburst model of dwarf novae and soft X-ray transients

    CERN Document Server

    Viallet, M

    2008-01-01

    We discuss two mechanisms that could result in an enhancement of the mass transfer rate during outbursts of dwarf novae and soft X-ray transients: the hot outer disc rim itself could heat the L1 point and scattered radiation by optically thin outflowing matter could also heat L1 significantly. We determine quantitatively the increase of the mass transfer rate resulting from an extra heating. During outbursts, the disc edge heats up the upper layer of the secondary with a flux of the order of the intrinsic stellar flux. This probably has no large effect on the mass transfer rate. In soft X-ray transients, the environing medium of the disc (corona+wind) could back-scatter a certain fraction of the accretion luminosity toward L1. Since soft X-ray transients reach high luminosities, even a low efficiency of this effect could yield a significant heating of L1, whereas we show that in dwarf novae this effect is negligible. Initially the incoming radiation does not penetrate below the photosphere of the secondary. D...

  19. Novae from isolated white dwarfs as a source of helium for second generation stars in globular clusters

    CERN Document Server

    Maccarone, Thomas J

    2011-01-01

    We explore the possible contribution of classical and recurrent novae from isolated white dwarfs accreting from the intracluster medium to the abundances of "second generation" globular cluster stellar populations. We show that under reasonable assumptions the helium abundances of clusters can be enhanced substantially by these novae and argue that novae should be considered as an important, and perhaps even dominant channel in the evolution of the intracluster medium. We also discuss a possible test for whether helium enhancement really is the cause of the multiple main sequences in globular clusters that is independent of the positions of stars in the color-magnitude diagram.

  20. Quark-Novae in Neutron Star-White-Dwarf Binaries: A model for dim, sub-Chandrasekhar, Type Ia Supernovae ?

    CERN Document Server

    Ouyed, Rachid

    2011-01-01

    We show that appealing to a Quark-Nova in a tight NS-WD binary system, a Type Ia explosion can occur for a narrow range in white dwarf mass (0.5 2 universe, we expect QNe-Ia to manifest themselves as rare sub-Chandrasekhar Type Ias; most likely in star-forming galaxies.

  1. Hystereses in dwarf nova outbursts and low-mass X-ray binaries

    Science.gov (United States)

    Hameury, J.-M.; Lasota, J.-P.; Knigge, C.; Körding, E. G.

    2017-04-01

    Context. The disc instability model (DIM) successfully explains why many accreting compact binary systems exhibit outbursts during which their luminosity increases by orders of magnitude. The DIM correctly predicts which systems should be transient and works regardless of whether the accretor is a black hole, a neutron star, or a white dwarf. However, it has been known for some time that the outbursts of X-ray binaries, which contain neutron-star or black-hole accretors, exhibit hysteresis in the X-ray hardness-intensity diagram (HID). More recently, it has been shown that the outbursts of accreting white dwarfs also show hysteresis, but in a diagram combining optical, EUV, and X-ray fluxes. Aims: We examine the nature of the hysteresis observed in cataclysmic variables and low-mass X-ray binaries. Methods: We used our disc evolution code for modelling dwarf nova outbursts, and constructed the hardness intensity diagram as predicted by the disc instability model. Results: We show explicitly that the standard DIM, modified only to account for disc truncation, can explain the hysteresis observed in accreting white dwarfs, but cannot explain that observed in X-ray binaries. Conclusions: The spectral evidence for the existence of different accretion regimes or components (disc, corona, jets, etc.) should only be based on wavebands that are specific to the innermost parts of the discs, i.e. EUV and X-rays; this task is difficult because of interstellar absorption. The existing data, however, indicate that a hysteresis is in the EUV - X-ray domain is present in SS Cyg.

  2. Accurate pre- and post-eruption orbital periods for the dwarf/classical nova V1017 Sgr

    Science.gov (United States)

    Salazar, Irene V.; LeBleu, Amy; Schaefer, Bradley E.; Landolt, Arlo U.; Dvorak, Shawn

    2017-08-01

    V1017 Sgr is a classical nova (from 1919) that displayed an earlier dwarf nova eruption (from 1901) and underwent two more dwarf nova events (in 1973 and 1991). Previous work on this bright system in quiescence (V = 13.5) has consisted only of a few isolated magnitudes, a few spectra and an ambiguous claim of an orbital period of 5.714 d based on nine radial velocities. To test this period, we have collected 2896 magnitudes (plus 53 in the literature) in the UBVRIJHKL bands from 1897-2016, making an essentially complete photometric history of this unique cataclysmic variable. We find that the light curve in all bands is dominated by the ellipsoidal modulations of a G giant companion star, with a post-eruption (after the 1919 nova event) orbital period of 5.786290 ± 0.000032 d. This is the longest period for any classical nova; the accretion must be powered by the nuclear evolution of the companion star and dwarf nova events occur only because the outer parts of the large disc are cool enough to be unstable. Further, we measure the pre-eruption orbital period (from 1907-1916). The orbital period has decreased by 273 ± 61 parts per million across the 1919 eruption, with the significance of the period change being at the 5.7σ confidence level. This is startling and mystifying for nova theory, because the three known period-change effects cannot account for a period decrease in V1017 Sgr, much less one of such a large size.

  3. Dwarf nova-type cataclysmic variable stars are significant radio emitters

    CERN Document Server

    Coppejans, Deanne L; Miller-Jones, James C A; Rupen, Michael P; Sivakoff, Gregory R; Knigge, Christian; Groot, Paul J; Woudt, Patrick A; Waagen, Elizabeth O; Templeton, Matthew

    2016-01-01

    We present 8--12\\,GHz radio light curves of five dwarf nova (DN) type Cataclysmic Variable stars (CVs) in outburst (RX And, U Gem and Z Cam), or superoutburst (SU UMa and YZ Cnc), increasing the number of radio-detected DN by a factor of two. The observed radio emission was variable on time-scales of minutes to days, and we argue that it is likely to be synchrotron emission. This sample shows no correlation between the radio luminosity and optical luminosity, orbital period, CV class, or outburst type; however higher-cadence observations are necessary to test this, as the measured luminosity is dependent on the timing of the observations in these variable objects. The observations show that the previously detected radio emission from SS Cyg is not unique in type, luminosity (in the plateau phase of the outburst), or variability time-scales. Our results prove that DN, as a class, are radio emitters in outburst.

  4. Suppression of X-rays during an optical outburst of the helium dwarf nova KL Dra

    CERN Document Server

    Ramsay, Gavin; Rosen, Simon; Barclay, Thomas; Steeghs, Danny

    2012-01-01

    KL Dra is a helium accreting AM CVn binary system with an orbital period close to 25 mins. Approximately every 60 days there is a 4 mag optical outburst lasting ~10 days. We present the most sensitive X-ray observations made of an AM CVn system during an outburst cycle. A series of eight observations were made using XMM-Newton which started shortly after the onset of an optical outburst. We find that X-rays are suppressed during the optical outburst. There is some evidence for a spectral evolution of the X-ray spectrum during the course of the outburst. A periodic modulation is seen in the UV data at three epochs -- this is a signature of the binary orbital or the super-hump period. The temperature of the X-ray emitting plasma is cooler compared to dwarf novae, which may suggest a wind is the origin of a significant fraction of the X-ray flux.

  5. Curious Variables Experiment (CURVE). CCD Photometry of Dwarf Nova V660 Herculis

    CERN Document Server

    Olech, A; Cook, L M; Mularczyk, K; Kedzierski, P; Wisniewski, M

    2005-01-01

    We report extensive photometry of the dwarf nova V660 Herculis. During our campaign, lasting from August 2003 to November 2004, we recorded one bright eruption which turned out to be a superoutburst lasting about 15 days and having amplitude of ~4.5 mag. Clear superhumps with a mean period of Psh = 0.080924(18) days were present during all nights of the superoutburst. The period of the superhumps was not stable and in the interval covered by our observations it decreased with a rate of -4.0(1.4) * 10^{-5}. Basing on our data and the known orbital period of the binary (Thorstensen and Fenton 2003) we calculate the period excess of 3.4 +/- 0.1%, which is typical for an SU UMa star at this orbital period. This value indicates that the mass ratio of the system is q=0.154.

  6. Quiescent Superhumps Detected in the Dwarf Nova V344 Lyrae by Kepler

    CERN Document Server

    Still, Martin; Wood, Matt A; Cannizzo, John K; Smale, Alan P

    2010-01-01

    The timing capabilities and sensitivity of Kepler, NASA's observatory to find Earth-sized planets within the habitable zone of stars, are well matched to the timescales and amplitudes of accretion disk variability in cataclysmic variables. This instrumental combination provides an unprecedented opportunity to test and refine stellar accretion paradigms with high-precision, uniform data, containing none of the diurnal or season gaps that limit ground-based observations. We present a 3-month, 1 minute cadence Kepler light curve of V344 Lyr, a faint, little-studied dwarf nova within the Kepler field. The light curve samples V344 Lyr during five full normal outbursts and one superoutburst. Surprisingly, the superhumps found during superoutburst continue to be detected during the following quiescent state and normal outburst. The fractional excess of superhump period over the presumed orbital period suggests a relatively high binary mass ratio in a system where the radius of the accretion disk must vary by less th...

  7. Suzaku Observation of the Dwarf Nova V893 Scorpii: The Discovery of a Partial X-Ray Eclipse

    Science.gov (United States)

    Mukai, Koji; Zietsman, E.; Still, M.

    2008-01-01

    V893 Sco is an eclipsing dwarf nova that had attracted little attention from X-ray astronomers until it was proposed as the identification of an RXTE all-sky slew survey (XSS) source. Here we report on the po inted X-ray observations of this object using Suzaku. We confirm V893 Sco to be X-ray bright, whose spectrum is highly absorbed for a dwar f nova. We have also discovered a partial X-ray eclipse in V893 Sco. This is the first time that a partial eclipse is seen in Xray light c urves of a dwarf nova. We have successfully modeled the gross features of the optical and X-ray eclipse light curves using a boundary layer geometry of the X-ray emission region. Future observations may lead to confirmation of this basic picture, and allow us to place tight co nstraints on the size of the X-ray emission region. The partial X-ray eclipse therefore should make V893 Sco a key object in understanding the physics of accretion in quiescent dwarf nova.

  8. Phase-resolved spectroscopy of the helium dwarf nova 'SN 2003aw' in quiescence

    CERN Document Server

    Roelofs, G; Marsh, T; Steeghs, D; Nelemans, G

    2006-01-01

    High time resolution spectroscopic observations of the ultra-compact helium dwarf nova 'SN 2003aw' in its quiescent state at V=20.5 reveal its orbital period at 2027.8 +/- 0.5 seconds or 33.80 minutes. Together with the photometric 'superhump' period of 2041.5 +/- 0.5 seconds, this implies a mass ratio q of 0.036. We compare both the average and time-resolved spectra of 'SN 2003aw' and SDSS J124058.03-015919.2. Both show a DB white dwarf spectrum plus an optically thin, helium-dominated accretion disc. 'SN 2003aw' distinguishes itself from the SDSS source by its strong calcium H & K emission lines, suggesting higher abundances of heavy metals than the SDSS source. The silicon and iron emission lines observed in the SDSS source are about twice as strong in 'SN 2003aw'. The peculiar 'double bright spot' accretion disc feature seen in the SDSS source is also present in time-resolved spectra of 'SN 2003aw', albeit much weaker.

  9. Superoutburst of WZ Sge-type dwarf nova below the period minimum: ASASSN-15po

    Science.gov (United States)

    Namekata, Kosuke; Isogai, Keisuke; Kato, Taichi; Littlefield, Colin; Matsumoto, Katsura; Kojiguchi, Naoto; Sugiura, Yuki; Uto, Yusuke; Fukushima, Daiki; Tatsumi, Taiki; Yamada, Eiji; Kamibetsunawa, Taku; de Miguel, Enrique; Stein, William L.; Sabo, Richard; Andreev, Maksim V.; Morelle, Etienne; Pavlenko, E. P.; Babina, Julia V.; Baklanov, Alex V.; Antonyuk, Kirill A.; Antonyuk, Okasana I.; Sosnovskij, Aleksei A.; Shugarov, Sergey Yu.; Golysheva, Polina Yu.; Gladilina, Natalia G.; Miller, Ian; Neustroev, Vitaly V.; Chavushyan, Vahram; Valdés, José R.; Sjoberg, George; Maeda, Yutaka; Itoh, Hiroshi; Masi, Gianluca; Michel, Raúl; Dubovsky, Pavol A.; Kiyota, Seiichiro; Tordai, Tamás; Oksanen, Arto; Ruiz, Javier; Nogami, Daisaku

    2017-02-01

    We report on a superoutburst of a WZ Sge-type dwarf nova (DN), ASASSN-15po. The light curve showed the main superoutburst and multiple rebrightenings. In this outburst, we observed early superhumps and growing (stage A) superhumps with periods of 0.050454(2) and 0.051809(13) d, respectively. We estimated that the mass ratio of secondary to primary (q) is 0.0699(8) by using Porb and a superhump period PSH of stage A. ASASSN-15po [Porb ˜ 72.6 min] is the first DN with an orbital period between 67-76 min. Although the theoretical predicted period minimum Pmin of hydrogen-rich cataclysmic variables (CVs) is about 65-70 min, the observational cut-off of the orbital period distribution at 80 min implies that the period minimum is about 82 min, and the value is widely accepted. We suggest the following four possibilities: the object is (1) a theoretical period minimum object, (2) a binary with a evolved secondary, (3) a binary with a metal-poor (Popullation II) seconday, or (4) a binary which was born with a brown-dwarf donor below the period minimum.

  10. Cyclical period changes in the dwarf novae V2051 Oph and V4140 Sgr

    CERN Document Server

    Baptista, R; Bond, H E; Jablonski, F J; Steiner, J E; Grauer, A D

    2003-01-01

    We report the identification of cyclical changes in the orbital period of the eclipsing dwarf novae V2051 Ophiuchi and V4140 Sagitarii. We used sets of white dwarf mid-eclipse timings to construct observed-minus-calculated diagrams covering, respectively, 25 and 16 years of observations. The V2051 Oph data present cyclical variations that can be fitted by a linear plus sinusoidal function with period 22 +/- 2 yr and amplitude 17 +/- 3 s. The statistical significance of this period by an F-test is larger than 99.9 per cent. The V4140 Sgr data present cyclical variations of similar amplitude and period 6.9 +/- 0.3 yr which are statistically significant at the 99.7 per cent level. We derive upper limits for secular period changes of |dP/dt| < 3x10^{-12} and |dP/dt| < 1.8x10^{-11}, respectively for V2051 Oph and V4140 Sgr. We combined our results with those in the literature to construct a diagram of the amplitude versus period of the modulation for a sample of 11 eclipsing cataclysmic variables (CVs). If t...

  11. Eclipse mapping of the flickering sources in the dwarf nova V2051 Ophiuchi

    CERN Document Server

    Baptista, R; Baptista, Raymundo; Bortoletto, Alexandre

    2004-01-01

    We report on the eclipse mapping analysis of an ensemble of light curves of the dwarf nova V2051 Oph with the aim to study the spatial distribution of its steady-light and flickering sources. The data are combined to derive the orbital dependency of the steady-light and the flickering components at two different brightness levels, named the 'faint' and 'bright' states. The differences in brightness are caused by long-term variations in the mass transfer rate from the secondary star. Eclipse maps of the steady-light show enhanced emission along the ballistic stream trajectory, in a clear evidence of gas stream overflow. We identify two different and independent sources of flickering in V2051 Oph. Low-frequency flickering arises in the overflowing gas stream and is associated to the mass transfer process. It maximum emission occurs at the position of closest approach of the gas stream to the white dwarf, and its spatial distribution changes in response to variations in mass transfer rate. High-frequency flicker...

  12. Spectroscopy and photometry of the dwarf nova BZ Ursae Majoris and the CV linewidth/K, mass-ratio relation

    Science.gov (United States)

    Jurcevic, J. S.; Honeycutt, R. K.; Schlegel, E. M.; Webbink, R. F.

    1994-01-01

    Time-resolved spectroscopy of the dwarf nova BZ Ursae Majoris (BZ UMa) reveals periodic velocity variations in the hydrogen emission lines with P = 97.9 +/- 0.1 min and K = 73 +/- 6 km/s. CCD photometry over a 16-month interval shows three outbursts of about 4 mag with a mean separation of 181 days. The mean full width at half maximum (FWHM) for the hydrogen beta emission is large, prompting a recalibration of the FWHM/K vs. mass ratio relation, giving a mass ratio (M(sub RD)/M(sub WD)) of 0.20 for BZ UMa. The short period, long outburst interval, and small mass ratio support the suggestion of BZ UMa being in the SU Ursae Majoris subclass of dwarf novae.

  13. Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae. VI: The Sixth Year (2013-2014)

    CERN Document Server

    Kato, Taichi; Kudzej, Igor; Hambsch, Franz-Josef; Miller, Ian; Ohshima, Tomohito; Nakata, Chikako; Kawabata, Miho; Nishino, Hirochika; Masumoto, Kazunari; Mizoguchi, Sahori; Yamanaka, Masayuki; Matsumoto, Katsura; Sakai, Daisuke; Fukushima, Daiki; Matsuura, Minami; Bouno, Genki; Takenaka, Megumi; Nakagawa, Shinichi; Noguchi, Ryo; Iino, Eriko; Pickard, Roger D; Maeda, Yutaka; Henden, Arne; Kasai, Kiyoshi; Kiyota, Seiichiro; Akazawa, Hidehiko; Imamura, Kazuyoshi; de Miguel, Enrique; Maehara, Hiroyuki; Monard, Berto; Pavlenko, Elena P; Antonyuk, Kirill; Pit, Nikolaj; Antonyuk, Oksana I; Baklanov, Aleksei V; Ruiz, Javier; Richmond, Michael; Oksanen, Arto; Harlingten, Caisey; Shugarov, Sergey Yu; Chochol, Drahomir; Masi, Gianluca; Nocentini, Francesca; Schmeer, Patrick; Bolt, Greg; Nelson, Peter; Ulowetz, Joseph; Sabo, Richard; Goff, William N; Stein, William; Michel, Raul; Dvorak, Shawn; Voloshina, Irina B; Metlov, Vladimir; Katysheva, Natalia; Neustroev, Vitaly V; Sjoberg, George; Littlefield, Colin; Debski, Bartlomiej; Sowicka, Paulina; Klimaszewski, Marcin; Curylo, Malgorzata; Morelle, Etienne; Curtis, Ivan A; Iwamatsu, Hidetoshi; Butterworth, Neil D; Andreev, Maksim V; Parakhin, Nikolai; Sklyanov, Aleksandr; Shiokawa, Kazuhiko; Novak, Rudolf; Irsmambetova, Tat'yana R; Itoh, Hiroshi; Ito, Yoshiharu; Hirosawa, Kenji; Denisenko, Denis; Kochanek, Christopher S; Shappee, Benjamin; Stanek, Krzysztof Z; Prieto, Jose L; Itagaki, Koh-ichi; Stubbings, Rod; Ripero, Jose; Muyllaert, Eddy; Poyner, Gary

    2014-01-01

    Continuing the project described by Kato et al. (2009, PASJ, 61, S395, arXiv:0905.1757), we collected times of superhump maxima for 56 SU UMa-type dwarf novae mainly observed during the 2013-2014 season and characterized these objects. We detected negative superhumps in VW Hyi and indicated that the low number of normal outbursts in some supercycle can be interpreted as a result of the disk tilt. This finding, combined with the Kepler observation of V1504 Cyg and V344 Lyr, suggests that the disk tilt is responsible for modulating the outburst pattern in SU UMa-type dwarf novae. We also studied the deeply eclipsing WZ Sge-type dwarf nova MASTER OT J005740.99+443101.5 and found evidence of a sharp eclipse during the phase of early superhumps. The profile can be reproduced by a combination of the eclipse of the axisymmetric disk and the uneclipsed light source of early superhumps. This finding confirms the lack of evince of a greatly enhanced hot spot during the early stage of WZ Sge-type outburst. We detected g...

  14. A systematic X-ray study of the dwarf novae observed with Suzaku

    Science.gov (United States)

    Wada, Qazuya; Tsujimoto, Masahiro; Ebisawa, Ken; Hayashi, Takayuki

    2017-02-01

    X-ray behavior of the dwarf novae (DNe) outside the quiescent state has not been fully understood. We thus assembled 21 data sets of the 15 DNe observed by the Suzaku satellite by the end of 2013, which include spectra taken during not only the quiescence, but also the transitional, outburst, and super-outburst states. Starting with the traditional cooling flow model to explain the X-ray emission from the boundary layer, we made several modifications to account for the observed spectra. As a result, we found that the best-fitting spectral model depends strongly on the state of the DNe with only a few exceptions. Spectra in the quiescent state are explained by the cooling flow model plus a Fe fluorescent line emission attenuated by an interstellar extinction. Spectra in the transitional state require an additional partial covering extinction. Spectra in the outburst and super-outburst state require additional low-temperature thin-thermal plasma component(s). Spectra in the super-outburst state further require a high value of minimum temperature for the boundary layer. We present an interpretation on the required modifications to the cooling flow model for each state.

  15. A Systematic X-ray Study of the Dwarf Novae Observed with Suzaku

    CERN Document Server

    Wada, Qazuya; Ebisawa, Ken; Hayashi, Takayuki

    2016-01-01

    X-ray behavior of the dwarf novae (DNe) outside the quiescent state has not been fully understood. We thus assembled 21 data sets of the 15 DNe observed by the Suzaku satellite by the end of 2013, which include spectra taken during not only the quiescence, but also the transitional, outburst, and super-outburst states. Starting with the traditional cooling flow model to explain the X-ray emission from the boundary layer, we made several modifications to account for the observed spectra. As a result, we found that the best-fit spectral model depends strongly on the state of the DNe with only a few exceptions. Spectra in the quiescent state are explained by the cooling flow model plus a Fe fluorescent line emission attenuated by an interstellar extinction. Spectra in the transitional state require an additional partial covering extinction. Spectra in the outburst and super-outburst state require additional low-temperature thin-thermal plasma component(s). Spectra in the super-outburst state further require a hi...

  16. The orbital and superhump periods of the dwarf nova SDSS J093249.57+472523.0

    CERN Document Server

    Shears, Jeremy; Dvorak, Shawn; de Miguel, Enrique; Morelle, Etienne; Oksanen, Arto; Sabo, Richard

    2012-01-01

    We report unfiltered CCD photometry of the eclipsing dwarf nova SDSS J093249.57+472523.0 obtained during its first confirmed outburst in 2011 March. The outburst amplitude was at least 3.0 magnitudes above mean quiescence and it lasted at least 11 days, although we missed the beginning of the outburst. Superhumps having peak-to-peak amplitude up to 0.3 magnitudes were present during the outburst, thereby establishing it to be a member of the SU UMa family. The mean superhump period was Psh = 0.06814(11) d. Analysis of our measurements of eclipse times of minimum, supplemented with data from other researchers, allowed us to measure the orbital period as Porb = 0.06630354(5) d. The superhump period excess was epsilon = 0.028(1) which is consistent with of SU UMa systems of similar Porb. The FWHM eclipse duration varied between 6 and 13 mins and the eclipse depth was up to 1.6 magnitudes.

  17. Curious Variables Experiment (CURVE). Variable properties of the dwarf nova SS UMi

    CERN Document Server

    Olech, A; Kedzierski, P; Zloczewski, K; Wisniewski, M; Szaruga, K

    2006-01-01

    We report on extensive photometry of the dwarf nova SS Ursae Minoris throughout nine months of 2004. In total, we recorded two superoutbursts and 11 normal outbursts of the star. SS UMi has been known to show frequent superoutbursts with a mean interval of 84.7 days. Our data suggest that the interval between successive superoutbursts lengthened to 197 days, indicating that SS UMi entered a period of untypical behavior manifested by a growth in the quiescent magnitude of the star and a series of frequent, low-amplitude, normal outbursts observed from July to September 2004. The mean superhump period derived for the April 2004 superoutburst of SS UMi is 0.070149(16) days (101.015 min). Combining this value with an earlier orbital period determination, we were able to derive the period excess, which is equal to 3.5 +/- 1.6%, and estimate the mass ratio of the binary system as equal to q=0.16 +/- 0.07. During the entire superoutburst, the period decreased at a rate of $\\dot P/P_{\\rm sh} = -6.3(1.4) \\times 10^{-5...

  18. Curious Variables Experiment (CURVE). CCD photometry of active dwarf nova DI UMa

    CERN Document Server

    Rutkowski, A; Wiśniewski, M; Pietrukowicz, P; Pala, J; Poleski, R

    2008-01-01

    We report an analysis of photometric behaviour of DI UMa - an extremaly active dwarf nova. The observational campaign (carried on in 2007) covers five superoutbursts and four normal outbursts. We examined principal parameters of the system in order to understand peculiarities of DI UMa, and other most active cataclysmic variables. Based on precise photometric measurements, temporal light curve behaviour, O-C analysis and power spectrum analysis, we investigated physical parameters of the system. We found that the period of the supercycle is now equal to 31.45 +/-0.3 days. Observations during superoutbursts give the period of superhumps equal to P_sh = 0.055318(11) days (79.66 +/- 0.02 min). During quiescence, light curve reveals modulation with a period P_orb = 0.054579(6) days (78.59 +/- 0.01 min), which we interpret as the orbital period of the binary system. The values obtained allowed us to determine fractional period excess equal to 1.35% +/- 0.02%, which is surprisingly small compared to the usual value...

  19. Cluster AgeS Experiment (CASE): Deficiency of observed dwarf novae in globular clusters

    CERN Document Server

    Pietrukowicz, P; Schwarzenberg-Czerny, A; Thompson, I B; Pych, W; Krzeminski, W; Mazur, B

    2008-01-01

    We present the results of a search for dwarf novae (DNe) in globular clusters (GCs). It is based on the largest available homogeneous sample of observations, in terms of the time span, number of observations and number of clusters. It includes 16 Galactic GCs and yielded two new certain DNe: M55-CV1 and M22-CV2. All previously known systems located in our fields were recovered, too. We surveyed M4, M5, M10, M12, M22, M30, M55, NGC 288, NGC 362, NGC 2808, NGC 3201, NGC 4372, NGC 6362, NGC 6752, omega Cen (NGC 5139) and 47 Tuc (NGC 104). The discovery of two DNe, namely M55-CV1 and M22-CV2, was already reported by Kaluzny et al. (2005) and Pietrukowicz et al. (2005), respectively. In the remaining 14 GCs we found no certain new DNe. Our result raises the total number of known DNe in the Galactic globular clusters to 12 DNe, distributed among 7 clusters. Our survey recovered all three already known erupting cataclysmic variables (CVs) located in our fields, namely M5-V101, M22-CV1, and V4 in the foreground of M3...

  20. Superoutburst of WZ Sge-type Dwarf Nova Below the Period Minimum: ASASSN-15po

    CERN Document Server

    Namekata, Kosuke; Kato, Taichi; Littlefield, Colin; Matsumoto, Katsura; Kojiguchi, Naoto; Sugiura, Yuki; Uto, Yusuke; Fukushima, Daiki; Tatsumi, Taiki; Yamada, Eiji; Kamibetsunawa, Taku; de Miguel, Enrique; Stein, William L; Sabo, Richard; Andreev, Maksim V; Morelle, Etienne; Pavlenko, E P; Babina, Julia V; Baklanov, Alex V; Antonyuk, Kirill A; Antonyuk, Okasana I; Sosnovskij, Aleksei A; Shugarov, Sergey Yu; Golysheva, Polina Yu; Gladilina, Natalia G; Miller, Ian; Neustroev, Vitaly V; Chavushyan, Vahram; Valdes, Jose R; Sjoberg, George; Maeda, Yutaka; Itoh, Hiroshi; Masi, Gianluca; Michel, Raul; Dubovsky, Pavol A; Kiyota, Seiichiro; Tordai, Tamas; Oksanen, Arto; Ruiz, Javier; Nogami, Daisaku

    2016-01-01

    We report on a superoutburst of a WZ Sge-type dwarf nova (DN), ASASSN-15po. The light curve showed the main superoutburst and multiple rebrightenings. In this outburst, we observed early superhumps and growing (stage A) superhumps with periods of 0.050454(2) and 0.051809(13) d, respectively. We estimated that the mass ratio of secondary to primary ($q$) is 0.0699(8) by using $P_{\\rm orb}$ and a superhump period $P_{\\rm SH}$ of stage A. ASASSN-15po [$P_{\\rm orb} \\sim$ 72.6 min] is the first DN with the orbital period between 67--76 min. Although the theoretical predicted period minimum $P_{\\rm min}$ of hydrogen-rich cataclysmic variables (CVs) is about 65--70 min, the observational cut-off of the orbital period distribution at 80 min implies that the period minimum is about 82 min, and the value is widely accepted. We suggest the following four possibilities: the object is (1) a theoretical period minimum object (2) a binary with a evolved secondary (3) a binary with a metal-poor (Popullation II) seconday (4) ...

  1. The 2011 Outburst of Recurrent Nova T Pyx: X-ray Observations Expose the White Dwarf Mass and Ejection Dynamics

    CERN Document Server

    Chomiuk, Laura; Mukai, Koji; Sokoloski, J L; Rupen, Michael P; Page, Kim L; Osborne, Julian P; Kuulkers, Erik; Mioduszewski, Amy J; Roy, Nirupam; Weston, Jennifer; Krauss, Miriam I

    2014-01-01

    The recurrent nova T Pyx underwent its sixth historical outburst in 2011, and became the subject of an intensive multi-wavelength observational campaign. We analyze data from the Swift and Suzaku satellites to produce a detailed X-ray light curve augmented by epochs of spectral information. X-ray observations yield mostly non-detections in the first four months of outburst, but both a super-soft and hard X-ray component rise rapidly after Day 115. The super-soft X-ray component, attributable to the photosphere of the nuclear-burning white dwarf, is relatively cool (~45 eV) and implies that the white dwarf in T Pyx is significantly below the Chandrasekhar mass (~1 M_sun). The late turn-on time of the super-soft component yields a large nova ejecta mass (>~10^-5 M_sun), consistent with estimates at other wavelengths. The hard X-ray component is well fit by a ~1 keV thermal plasma, and is attributed to shocks internal to the 2011 nova ejecta. The presence of a strong oxygen line in this thermal plasma on Day 194...

  2. NLTE model atmospheres for the hottest white dwarfs: Spectral analysis of the compact component in nova V4743 Sgr

    CERN Document Server

    Rauch, T; Gonzales-Riestra, R; Nelson, T; Still, M; Werner, K; Wilms, J; 10.1088/0004-637X/717/1/363

    2010-01-01

    Half a year after its outburst in September 2002, nova V4743 Sgr evolved into the brightest supersoft X-ray source in the sky with a flux maximum around 30A. We calculated grids of synthetic energy distributions (SEDs) based on NLTE model atmospheres for the analysis of the hottest white dwarfs and present the result of fits to Chandra and XMM-Newton grating X-ray spectra of V4743 Sgr of outstanding quality, exhibiting prominent resonance lines of C V, C VI, N VI, N VII, and O VII in absorption. The nova reached its highest effective temperature (Teff = 740 +/- 70kK) around April 2003 and remained at that temperature at least until September 2003. We conclude that the white dwarf is massive, about 1.1 - 1.2 Msun. The nuclear-burning phase lasted for 2 to 2.5 years after the outburst, probably the average duration for a classical nova. The photosphere of V4743 Sgr was strongly carbon deficient (about times solar) and enriched in nitrogen and oxygen (> 5 times solar). Especially the very low C/N ratio indicates...

  3. EUVE All-Sky Survey Observations of the Dwarf Nova VW Hydri

    Science.gov (United States)

    Mauche, C. W.; Warren, J. K.; Vallerga, J. V.; Mukai, K.; Mattei, J. A.

    1993-05-01

    The dwarf nova VW Hyi was observed from 1992 November 1 to 18 and from November 20 to 23 by the Extreme Ultraviolet Explorer (EUVE) satellite during its all-sky survey. The total time on source was 22 kiloseconds. During the first part of the scan, VW Hyi was in quiescence following a superoutburst and was not detected by EUVE above background. However, the source went into a narrow outburst on November 13.8 U.T., peaked at V ~ 10 on November 14.8 U.T., started to fade on November 15.9 U.T., and returned to quiescence on November 17.8 U.T. In contrast, the source did not turn on in the EUV until November 15.0 U.T., did not peak until November 15.3 U.T., and had returned to quiescence by November 16.3 U.T. Accounting for the different sensitivities in the two wavebands, we conclude that the EUV outburst was delayed relative to the optical outburst by ~ 0.5 day and that the EUV outburst was narrower than the optical outburst by ~ 1 day. During the peak of the EUV outburst, the source was detected at the 3sigma level in the Lex/B (50--180 Angstroms ) scanner with a count rate of ~ 0.03 s(-1) and at the 4sigma level in the Al/Ti/C (160--240 Angstroms ) scanner with a count rate of ~ 0.09 s(-1) . That the Al/Ti/C count rate is significantly higher than the Lex/B count rate, whereas the effective area of the Al/Ti/C filter is smaller than that of the Lex/B filter, strongly indicates that the source was very soft when it was on. We use the count rates in these two filters to constrain the temperature and luminosity of the source of the shortest wavelength radiation in VW Hyi: the inner disk and the boundary layer between the disk and the surface of the white dwarf.

  4. WZ Sge-type dwarf novae with multiple rebrightenings: MASTER OT J211258.65+242145.4 and MASTER OT J203749.39+552210.3

    CERN Document Server

    Nakata, Chikako; Kato, Taichi; Nogami, Daisaku; Masi, Gianluca; de Miguel, Enrique; Ulowetz, Joseph; Littlefield, Colin; Goff, William N; Krajci, Thomas; Maehara, Hiroyuki; Stein, William; Sabo, Richard; Noguchi, Ryo; Ono, Rikako; Kawabata, Miho; Furukawa, Hisami; Matsumoto, Katsura; Ishibashi, Takehiro; Dubovsky, Pavol A; Kudzej, Igor; Dvorak, Shawn; Hambsch, Franz-Josef; Pickard, Roger D; Morelle, Etienne; Muyllaert, Eddy; Padovan, Stefano; Henden, Arne

    2013-01-01

    We report on photometric observations of WZ Sge-type dwarf novae, MASTER OT J211258.65+242145.4 and MASTER OT J203749.39+552210.3 which underwent outbursts in 2012. Early superhumps were recorded in both systems. During superoutburst plateau, ordinary superhumps with a period of 0.060291(4) d (MASTER J211258) and of 0.061307(9) d (MASTER J203749) in average were observed. MASTER J211258 and MASTER J203749 exhibited eight and more than four post-superoutburst rebrightenings, respectively. In the final part of the superoutburst, an increase in the superhump periods was seen in both systems. We have made a survey of WZ Sge-type dwarf novae with multiple rebrightenings, and confirmed that the superhump periods of WZ Sge-type dwarf novae with multiple rebrightenings were longer than those of WZ Sge-type dwarf novae without a rebrightening. Although WZ Sge-type dwarf novae with multiple rebrightenings have been thought to be the good candidates for period bouncers based on their low mass ratio (q) from inferred fro...

  5. Suzaku Observations of the Dwarf Nova V893 Scorpii: the Discovery of a Partial X-ray Eclipse

    CERN Document Server

    Mukai, K; Still, M

    2009-01-01

    V893 Sco is an eclipsing dwarf nova that had attracted little attention from X-ray astronomers until it was proposed as the identification of an RXTE all-sky slew survey (XSS) source. Here we report on the pointed X-ray observations of this object using Suzaku. V893 Sco was in quiescence at the time, as indicated by the coordinated optical photometry we obtained at the South African Astronomical Observatory. Our Suzaku data show V893 Sco to be X-ray bright, with a highly absorbed spectrum. Most importantly, we have discovered a partial X-ray eclipse in V893 Sco. This is the first time that a partial eclipse is seen in X-ray light curves of a dwarf nova. Our preliminary simulations demonstrate that the partial X-ray eclipse can be in principle reproduced if the white dwarf in V893 Sco is partially eclipsed. Higher quality observations of this object have the potential to place significant constraints on the latitudinal extent of the X-ray emission region and thereby discriminating between an equatorial boundar...

  6. NuSTAR observations of the Dwarf Nova GK Persei in 2015: comparison between outburst and quiescent phases

    CERN Document Server

    Wada, Yuuki; Nakazawa, Kazuhiro; Makishima, Kazuo; Hayashi, Takayuki; Ishida, Manabu

    2016-01-01

    We report on NuSTAR observations of the Intermediate Polar GK Persei which also behaves as a Dwarf Nova. It exhibited a Dwarf Nova outburst in 2015 March-April. The object was observed in 3-79 keV X-rays with NuSTAR, once at the outburst peak, and again in 2015 September during quiescence. The 5-50 keV flux during the outburst was 26 times higher than that during the quiescence. With a multi-temperature emission model and a reflection model, we derived the post-shock temperature as 19.2 +/- 0.7 keV in the outburst, and 38.5 +4.1/-3.6 keV in the quiescence. This temperature difference is considered to reflect changes in the radius at which the accreting matter, forming an accretion disk, is captured by the magnetosphere of the white dwarf (WD). Assuming that this radius scales as the power of -2/7 of the mass accretion rate, and utilizing the two temperature measurements, as well as the standard mass-radius relation of WDs, we determined the WD mass in GK Persei as 0.90 +/- 0.06 solar masses. The magnetic fiel...

  7. MN Draconis: a peculiar, active dwarf nova in the period gap

    Science.gov (United States)

    Bąkowska, K.; Olech, A.; Pospieszyński, R.; Świerczyński, E.; Martinelli, F.; Rutkowski, A.; Koff, R.; Drozd, K.; Butkiewicz-Bąk, M.; Kankiewicz, P.

    2017-07-01

    Context. We present results of an extensive world-wide observing campaign of MN Draconis. Aims: MN Draconis is a poorly known active dwarf nova in the period gap and is one of only two known cases of period-gap SU UMa objects showing negative superhumps. The photometric behaviour of MN Draconis poses a challenge for existing models of the superhump and superoutburst mechanisms. Therefore, a thorough investigation of peculiar systems like MN Draconis is crucial for our understanding of the evolution of close binary stars. Methods: To measure the fundamental parameters of the system, we collected photometric data in October 2009, June-September 2013, and June-December 2015. We analysed the light curves, O-C diagrams, and power spectra. Results: During our three observational seasons we detected four superoutburts and several normal outbursts. Based on the two consecutive superoutbursts detected in 2015, the supercycle length was derived as Psc = 74 ± 0.5 days, and it has been increasing with a rate of ˙P = 3.3 × 10-3 during the past twelve years. Based on the positive and negative superhumps, we calculated the period excess ɛ = 5.6% ± 0.1%, the period deficit ɛ- = 2.5% ± 0.6%, and as a result, the orbital period Porb = 0.0994(1) days (143.126 ± 0.144 min). We updated the basic light curve parameters of MN Draconis. Conclusions: MN Draconis is the first discovered SU UMa system in the period gap with an increasing supercycle length. Photometric data are only 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/603/A72

  8. A Brief Overview and Research Progress of Dwarf Novae%矮新星概述与研究进展

    Institute of Scientific and Technical Information of China (English)

    韩忠涛

    2014-01-01

    矮新星是爆发频繁的激变变星,主星是白矮星,次星是充满洛希瓣的晚型矮星;白矮星周围有吸积盘,物质流与吸积盘的碰撞区域即热斑。与大多数密近双星系统相比,矮新星最大的特点是吸积盘的存在以及频繁的爆发现象。首先介绍了矮新星的研究历史和现状,对吸积盘的形成过程进行总结,给出了矮新星的基本物理图像;其次简要介绍了矮新星的各种次型的特征和形成原因,对目前的爆发模型进行归纳;回顾了矮新星中著名的轨道周期空缺现象和最短轨道周期截止现象,并给出其在标准化模型下的解释以及标准化模型面临的挑战;举例说明了矮新星的轨道周期变化分析不仅对研究其演化起着重要作用,而且是探测褐矮星和地外行星的重要手段;对食光变曲线的分析方法和矮新星中罕见的高低态变化进行了简单小结;最后,进行总结并讨论矮新星领域的发展趋势和目前的一些热点问题。%Dwarf novae are erupting cataclysmic variable stars in which a Roche-lobe filling dwarf star (Secondary star) transfers matter to an accretion disc around a white dwarf (Primary star). The gas stream from the secondary star feeds material into the disc at a point near its outer rim where a bright spot is formed. The existence of accretion disc induces complex physical changes and observed features, including the frequent outburst phenomenon and the transitions from high states to low states, etc. The eclipse between binary stars provides an excellent opportunity to determine the relative brightness of each light source, geometric position and physical structure. Compared to most close binary systems, the largest characteristic of dwarf novae are the existence of accretion disc and the frequent outburst phenomenon. First, we give a brief review of the research history and status of dwarf novae studies. Second, the famous

  9. Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae. VIII: The Eighth Year (2015-2016)

    CERN Document Server

    Kato, Taichi; Monard, Berto; Vanmunster, Tonny; Maeda, Yutaka; Miller, Ian; Itoh, Hiroshi; Kiyota, Seiichiro; Isogai, Keisuke; Kimura, Mariko; Imada, Akira; Tordai, Tamas; Akazawa, Hidehiko; Tanabe, Kenji; Otani, Noritoshi; Ogi, Minako; Ando, Kazuko; Takigawa, Naoki; Dubovsky, Pavol A; Kudzej, Igor; Shugarov, Sergey Yu; Katysheva, Natalia; Golysheva, Polina; Gladilina, Natalia; Chochol, Drahomir; Starr, Peter; Kasai, Kiyoshi; Pickard, Roger D; de Miguel, Enrique; Kojiguchi, Naoto; Sugiura, Yuki; Fukushima, Daiki; Yamada, Eiji; Uto, Yusuke; Kamibetsunawa, Taku; Tatsumi, Taiki; Takeda, Nao; Matsumoto, Katsura; Cook, Lewis M; Pavlenko, Elena P; Babina, Julia V; Pit, Nikolaj V; Antonyuk, Oksana I; Antonyuk, Kirill A; Sosnovskij, Aleksei A; Baklanov, Aleksei V; Kafka, Stella; Stein, William; Voloshina, Irina B; Ruiz, Javier; Sabo, Richard; Dvorak, Shawn; Stone, Geoff; Andreev, Maksim V; Antipin, Sergey V; Zubareva, Alexandra M; Zaostrojnykh, Anna M; Richmond, Michael; Shears, Jeremy; Dubois, Franky; Logie, Ludwig; Rau, Steve; Vanaverbeke, Siegfried; Simon, Andrei; Oksanen, Arto; Goff, William N; Bolt, Greg; Debski, Bartomiej; Kochanek, Christopher S; Shappee, Benjamin; Stanek, Krzysztof Z; Prieto, Jose L; Stubbings, Rod; Muyllaert, Eddy; Hiraga, Mitsutaka; Horie, Tsuneo; Schmeer, Patrick; Hirosawa, Kenji

    2016-01-01

    Continuing the project described by Kato et al. (2009, arXiv:0905.1757), we collected times of superhump maxima for 128 SU UMa-type dwarf novae observed mainly during the 2015-2016 season and characterized these objects. The data have improved the distribution of orbital periods, the relation between the orbital period and the variation of superhumps, the relation between period variations and the rebrightening type in WZ Sge-type objects. Coupled with new measurements of mass ratios using growing stages of superhumps, we now have a clearer and statistically greatly improved evolutionary path near the terminal stage of evolution of cataclysmic variables. Three objects (V452 Cas, KK Tel, ASASSN-15cl) appear to have slowly growing superhumps, which is proposed to reflect the slow growth of the 3:1 resonance near the stability border. ASASSN-15sl, ASASSN-15ux, SDSS J074859.55+312512.6 and CRTS J200331.3-284941 are newly identified eclipsing SU UMa-type (or WZ Sge-type) dwarf novae. ASASSN-15cy has a short (~0.05...

  10. Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae. V: The Fifth Year (2012-2013)

    CERN Document Server

    Kato, Taichi; Maehara, Hiroyuki; Nocentini, Gianluca Masi Francesca; Dubovsky, Pavol A; Kudzej, Igor; Ogi, Kazuyoshi Imamura Minako; Tanabe, Kenji; Akazawa, Hidehiko; Krajci, Thomas; de Miguel, Ian Miller Enrique; Henden, Arne; Littlefield, Colin; Ishibashi, Ryo Noguchi Takehiro; Ono, Rikako; Kawabata, Miho; Sakai, Hiroshi Kobayashi Daisuke; Nishino, Hirochika; Furukawa, Hisami; Matsumoto, Kazunari Masumoto Katsura; Ohshima, Tomohito; Nakata, Chikako; Kinugasa, Satoshi Honda Kenzo; Hashimoto, Osamu; Stein, William; Kiyota, Roger D Pickard Seiichiro; Pavlenko, Elena P; Antonyuk, Oksana I; Antonyuk, Aleksei V Baklanov Kirill; Samsonov, Denis; Pit, Nikolaj; Oksanen, Aleksei Sosnovskij Arto; Harlingten, Caisey; Tyyska, Jenni; Shugarov, Berto Monard Sergey Yu; Chochol, Drahomir; Kasai, Kiyoshi; Hirosawa, Yutaka Maeda Kenji; Itoh, Hiroshi; Sabo, Richard; Morelle, Joseph Ulowetz Etienne; Michel, Raul; Suarez, Genaro; James, Nick; Voloshina, Shawn Dvorak Irina B; Richmond, Michael; Staels, Bart; Andreev, David Boyd Maksim V; Parakhin, Nikolai; Miyashita, Natalia Katysheva Atsushi; Nakajima, Kazuhiro; Bolt, Greg; Nelson, Stefano Padovan Peter; Starkey, Donn R; Buczynski, Denis; Starr, Peter; Denisenko, William N Goff Denis; Kochanek, Christopher S; Stanek, Benjamin Shappee Krzysztof Z; Prieto, Jose L; Itagaki, Koh-ichi; Stubbings, Shizuo Kaneko Rod; Muyllaert, Eddy; Schmeer, Jeremy Shears Patrick; Poyner, Gary; Marco, Miguel Rodriguez

    2013-01-01

    Continuing the project described by Kato et al. (2009a, arXiv:0905.1757), we collected times of superhump maxima for SU UMa-type dwarf novae mainly observed during the 2012-2013 season. We found three objects (V444 Peg, CSS J203937 and MASTER J212624) having strongly positive period derivatives despite the long orbital period (Porb). By using the period of growing stage (stage A) superhumps, we obtained mass ratios for six objects. We characterized nine new WZ Sge-type dwarf novae. We made a pilot survey of the decline rate of slowly fading part of SU UMa-type and WZ Sge-type outbursts. The decline time scale was found to generally follow the expected Porb^(1/4) dependence and WZ Sge-type outbursts also generally follow this trend. There are some objects which show slower decline rates, and we consider these objects good candidates for period bouncers. We also studied unusual behavior in some objects, including BK Lyn which made a transition from an ER UMa-type state to the novalike (standstill) state in 2013...

  11. Suzaku X-Ray Observation of the Dwarf Nova Z Camelopardalis at the Onset of an Optical Outburst

    CERN Document Server

    Saitou, Kei; Ebisawa, Ken; Ishida, Manabu

    2012-01-01

    We present the result of a Suzaku X-ray spectroscopic observation of the dwarf nova Z Camelopardalis, which was conducted by chance at the onset of an optical outburst. We used the X-ray Imaging Spectrometer (a 38 ks exposure) and the Hard X-ray Detector (34 ks) to obtain a 0.35-40 keV spectrum simultaneously. Spectral characteristics suggest that the source was in the X-ray quiescent state despite being in the rising phase of an outburst in the optical band. The spectrum shows a clear signature of circumstellar absorption in excess of interstellar absorption and the reprocessed emission features of Fe fluorescence and Compton scattering. The extra absorption is explained due to partial coverage by either neutral or ionized matter. We found a spectral change during the observation, which is attributable only to the change in the circumstellar absorption. Such an X-ray spectral variation is reported for the first time in dwarf novae. We speculate that the variation in the circumstellar absorption is interprete...

  12. Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae. II: The Second Year (2009-2010)

    CERN Document Server

    Kato, Taichi; Uemura, Makoto; Henden, Arne; de Miguel, Enrique; Miller, Ian; Dubovsky, Pavol A; Kudzej, Igor; Kiyota, Seiichiro; Hambsch, Franz-Josef; Tanabe, Kenji; Imamura, Kazuyoshi; Kunitomi, Nanae; Takagi, Ryosuke; Nose, Mikiha; Akazawa, Hidehiko; Masi, Gianluca; Nakagawa, Shinichi; Iino, Eriko; Noguchi, Ryo; Matsumoto, Katsura; Fujii, Daichi; Kobayashi, Hiroshi; Ogura, Kazuyuki; Ohtomo, Sachi; Yamashita, Kousei; Yanagisawa, Hirofumi; Itoh, Hiroshi; Bolt, Greg; Monard, Berto; Ohshima, Tomohito; Shears, Jeremy; Ruiz, Javier; Imada, Akira; Oksanen, Arto; Nelson, Peter; Gomez, Tomas L; Staels, Bart; Boyd, David; Voloshina, Irina B; Krajci, Thomas; Crawford, Tim; Stockdale, Chris; Richmond, Michael; Morelle, Etienne; Novak, Rudolf; Nogami, Daisaku; Ishioka, Ryoko; Brady, Steve; Simonsen, Mike; Pavlenko, Elena P; Kuramoto, Tetsuya; Miyashita, Atsushi; Pickard, Roger D; Hynek, Tomas; Dvorak, Shawn; Stubbings, Rod; Muyllaert, Eddy

    2010-01-01

    As an extension of the project in Kato et al. (2009, arXiv:0905.1757), we collected times of superhump maxima for 61 SU UMa-type dwarf novae mainly observed during the 2009-2010 season. The newly obtained data confirmed the basic findings reported in Kato et al. (2009): the presence of stages A-C, as well as the predominance of positive period derivatives during stage B in systems with superhump periods shorter than 0.07 d. There was a systematic difference in period derivatives for systems with superhump periods longer than 0.075 d between this study and Kato et al. (2009). We suggest that this difference is possibly caused by the relative lack of frequently outbursting SU UMa-type dwarf novae in this period regime in the present study. We recorded a strong beat phenomenon during the 2009 superoutburst of IY UMa. The close correlation between the beat period and superhump period suggests that the changing angular velocity of the apsidal motion of the elliptical disk is responsible for the variation of superh...

  13. The Fall and the Rise of X-Rays from Dwarf Novae in Outburst: RXTE Observations of VW Hydri and WW Ceti

    Science.gov (United States)

    Fertig, D.; Mukai, K.; Nelson, T.; Cannizzo, J. K.

    2011-01-01

    In a dwarf nova, the accretion disk around the white dwarf is a source of ultraviolet, optical, and infrared photons, but is never hot enough to emit X-rays. Observed X-rays instead originate from the boundary layer between the disk and the white dwarf. As the disk switches between quiescence and outburst states, the 2-10 keV X-ray flux is usually seen to be anti-correlated with the optical brightness. Here we present RXTE monitoring observations of two dwarf novae, VW Hyi and WW Cet, confirming the optical/X-ray anti-correlation in these two systems. However, we do not detect any episodes of increased hard X-ray flux on the rise (out of two possible chances for WW Cet) or the decline (two for WW Cet and one for VW Hyi) from outburst, attributes that are clearly established in SS Cyg. The addition of these data to the existing literature establishes the fact that the behavior of SS Cyg is the exception, rather than the archetype as is often assumed. We speculate that only dwarf novae with a massive white dwarf may show these hard X-ray spikes.

  14. Survey of period variations of superhumps in SU UMa-type dwarf novae. VIII. The eighth year (2015-2016)

    Science.gov (United States)

    Kato, Taichi; Hambsch, Franz-Josef; Monard, Berto; Vanmunster, Tonny; Maeda, Yutaka; Miller, Ian; Itoh, Hiroshi; Kiyota, Seiichiro; Isogai, Keisuke; Kimura, Mariko; Imada, Akira; Tordai, Tamás; Akazawa, Hidehiko; Tanabe, Kenji; Otani, Noritoshi; Ogi, Minako; Ando, Kazuko; Takigawa, Naoki; Dubovsky, Pavol A.; Kudzej, Igor; Shugarov, Sergey Yu.; Katysheva, Natalia; Golysheva, Polina; Gladilina, Natalia; Chochol, Drahomir; Starr, Peter; Kasai, Kiyoshi; Pickard, Roger D.; Miguel, Enrique de; Kojiguchi, Naoto; Sugiura, Yuki; Fukushima, Daiki; Yamada, Eiji; Uto, Yusuke; Kamibetsunawa, Taku; Tatsumi, Taiki; Takeda, Nao; Matsumoto, Katsura; Cook, Lewis M.; Pavlenko, Elena P.; Babina, Julia V.; Pit, Nikolaj V.; Antonyuk, Oksana I.; Antonyuk, Kirill A.; Sosnovskij, Aleksei A.; Baklanov, Aleksei V.; Kafka, Stella; Stein, William; Voloshina, Irina B.; Ruiz, Javier; Sabo, Richard; Dvorak, Shawn; Stone, Geoff; Andreev, Maksim V.; Antipin, Sergey V.; Zubareva, Alexandra M.; Zaostrojnykh, Anna M.; Richmond, Michael; Shears, Jeremy; Dubois, Franky; Logie, Ludwig; Rau, Steve; Vanaverbeke, Siegfried; Simon, Andrei; Oksanen, Arto; Goff, William N.; Bolt, Greg; Dębski, Bartłomiej; Kochanek, Christopher S.; Shappee, Benjamin; Stanek, Krzysztof Z.; Prieto, José L.; Stubbings, Rod; Muyllaert, Eddy; Hiraga, Mitsutaka; Horie, Tsuneo; Schmeer, Patrick; Hirosawa, Kenji

    2016-08-01

    Continuing the project described by Kato et al. (2009, PASJ, 61, S395), we collected times of superhump maxima for 128 SU UMa-type dwarf novae observed mainly during the 2015-2016 season and characterized these objects. The data have improved the distribution of orbital periods, the relation between the orbital period and the variation of superhumps, and the relation between period variations and the rebrightening type in WZ Sge-type objects. Coupled with new measurements of mass ratios using growing stages of superhumps, we now have a clearer and statistically greatly improved evolutionary path near the terminal stage of evolution of cataclysmic variables. Three objects (V452 Cas, KK Tel, and ASASSN-15cl) appear to have slowly growing superhumps, which is proposed to reflect the slow growth of the 3 : 1 resonance near the stability border. ASASSN-15sl, ASASSN-15ux, SDSS J074859.55+312512.6, and CRTS J200331.3-284941 are newly identified eclipsing SU UMa-type (or WZ Sge-type) dwarf novae. ASASSN-15cy has a short (˜0.050 d) superhump period and appears to belong to EI Psc-type objects with compact secondaries having an evolved core. ASASSN-15gn, ASASSN-15hn, ASASSN-15kh, and ASASSN-16bu are candidate period bouncers with superhump periods longer than 0.06 d. We have newly obtained superhump periods for 79 objects and 13 orbital periods, including periods from early superhumps. In order that future observations will be more astrophysically beneficial and rewarding to observers, we propose guidelines on how to organize observations of various superoutbursts.

  15. The mass donor star and the accretion disc of the dwarf nova V2051 Ophiuchi in the infrared

    Science.gov (United States)

    Wojcikiewicz, Eduardo; Baptista, Raymundo; Ribeiro, Tiago

    2016-07-01

    We report the analysis of infrared JHK_s high speed photometry of the dwarf nova V2051 Oph in quiescence. We model the ellipsoidal variations in the light curve to measure the fluxes of the mass donor star. Its colors are consistent with an M8 ± 1 spectral type with an equivalent blackbody temperature of T_{bb}= (2700± 300) K, in agreement with spectroscopic measurements and with theoretical expectation for donor stars at the same orbital period. We use the mass donor star fluxes and the Barnes & Evans relation to find a photometric parallax distance of (102 ± 16) pc to the binary. At this distance the outbursts of V2051 Oph occur at disc temperatures everywhere lower than the minimum/critical temperature predicted by the disc instability model, underscoring previous suggestions that they are powered by mass transfer bursts. We subtract the contribution of the mass donor star and apply eclipse mapping techniques to the remaining light curve in order to investigate the structure and emission of its accretion disc. The infrared accretion disc is bright and 'blue' in the inner regions and becomes progressively fainter and redder with increasing radii, indicating that the disc temperature decreases with radius. Bulges in the eclipse shape, more prominent in the H and K_s bands, lead to asymmetric arcs in the eclipse maps reminiscent of the spiral arms found in disc maps of outbursting dwarf novae. The arcs show an azimuthal extent of ˜90^o, extend from the intermediate to the outer disc regions (0.3-0.4 R_{L1}, where R_{L1} is the distance from disc center to the inner lagrangian point), and account for ≃ 30 per cent of the total flux in the H and K_s bands.

  16. Survey of period variations of superhumps in SU UMa-type dwarf novae. V. The fifth year (2012-2013)

    Science.gov (United States)

    Kato, Taichi; Hambsch, Franz-Josef; Maehara, Hiroyuki; Masi, Gianluca; Nocentini, Francesca; Dubovsky, Pavol A.; Kudzej, Igor; Imamura, Kazuyoshi; Ogi, Minako; Tanabe, Kenji; Akazawa, Hidehiko; Krajci, Thomas; Miller, Ian; de Miguel, Enrique; Henden, Arne; Noguchi, Ryo; Ishibashi, Takehiro; Ono, Rikako; Kawabata, Miho; Kobayashi, Hiroshi; Sakai, Daisuke; Nishino, Hirochika; Furukawa, Hisami; Masumoto, Kazunari; Matsumoto, Katsura; Littlefield, Colin; Ohshima, Tomohito; Nakata, Chikako; Honda, Satoshi; Kinugasa, Kenzo; Hashimoto, Osamu; Stein, William; Pickard, Roger D.; Kiyota, Seiichiro; Pavlenko, Elena P.; Antonyuk, Oksana I.; Baklanov, Aleksei V.; Antonyuk, Kirill; Samsonov, Denis; Pit, Nikolaj; Sosnovskij, Aleksei; Oksanen, Arto; Harlingten, Caisey; Tyyskä, Jenni; Monard, Berto; Shugarov, Sergey Yu.; Chochol, Drahomir; Kasai, Kiyoshi; Maeda, Yutaka; Hirosawa, Kenji; Itoh, Hiroshi; Sabo, Richard; Ulowetz, Joseph; Morelle, Etienne; Michel, Raúl; Suárez, Genaro; James, Nick; Dvorak, Shawn; Voloshina, Irina B.; Richmond, Michael; Staels, Bart; Boyd, David; Andreev, Maksim V.; Parakhin, Nikolai; Katysheva, Natalia; Miyashita, Atsushi; Nakajima, Kazuhiro; Bolt, Greg; Padovan, Stefano; Nelson, Peter; Starkey, Donn R.; Buczynski, Denis; Starr, Peter; Goff, William N.; Denisenko, Denis; Kochanek, Christopher S.; Shappee, Benjamin; Stanek, Krzysztof Z.; Prieto, José L.; Itagaki, Koh-ichi; Kaneko, Shizuo; Stubbings, Rod; Muyllaert, Eddy; Shears, Jeremy; Schmeer, Patrick; Poyner, Gary; Rodríguez-Marco, Miguel

    2014-04-01

    Continuing the project described in Kato et al. (2009, PASJ, 61, S395), we collected times of superhump maxima for SU UMa-type dwarf novae mainly observed during the 2012-2013 season. We found three objects (V444 Peg, CSS J203937, and MASTER J212624) having strongly positive period derivatives despite the long orbital period (Porb). By using the period of growing stage (stage A) superhumps, we obtained mass ratios for six objects. We characterized nine new WZ Sge-type dwarf novae. We made a pilot survey of the decline rate in the slowly fading parts of SU UMa-type and WZ Sge-type outbursts. The decline time scale was found to generally follow an expected P_orb^{1/4} dependence, and WZ Sge-type outbursts also generally follow this trend. There are some objects which show slower decline rates, and we consider these objects good candidates for period bouncers. We also studied unusual behavior in some objects, including BK Lyn which made a transition from an ER UMa-type state to a novalike (standstill) state in 2013, and unusually frequent occurrences of superoutbursts in NY Ser and CR Boo. We applied the least absolute shrinkage and selection operator (Lasso) power spectral analysis, which has been proven to be very effective in analyzing the Kepler data, to the ground-based photometry of BK Lyn, and detected a dramatic disappearance of the signal of negative superhumps in 2013. We suggested that the mass-transfer rates did not strongly vary between the ER UMa-type state and novalike state in BK Lyn, and this transition was less likely caused by a systematic variation of the mass-transfer rate.

  17. The white dwarf in dwarf nova SDSS J080434.20+510349.2: Entering the instability strip?

    Energy Technology Data Exchange (ETDEWEB)

    Pavlenko, E, E-mail: pavlenko@crao.crimea.u [Crimean astrophysical observatory, Crimea 98409 (Ukraine)

    2009-06-01

    SDSS J080434.20+510349.2 is a WZ Sge type binary that displayed a rare outburst in 2006 (Pavlenko et al. 2007). During the long-lasting tail of the late stage of the outburst, the binary showed a two-humped or four-humped profile of the orbital light modulation. The amplitude of the orbital light curve decreased while the mean brightness decreased; moreover, that occurred approx 10 times faster during the fast outburst decline with respect to the late quiet state of slow outburst fading. There were no white dwarf pulsations detected in this system, neither 1 - 1.5 months prior to the outburst, nor in 1.5 - 2 months after the 2006 outburst. However, strong non-radial pulsations with period 12.6 minutes and a mean amplitude of 0.05m were first detected in the V band with the 2.6-m Shajn mirror telescope of the Crimean astrophysical observatory, approx 8 months after the outburst. The evolution of pulsations over two years, in 2006 - 2008, is considered. It is supposed that pulsations first appeared when the cooling white dwarf (after the outburst) entered the instability strip, although the possibility of temporary lack of pulsations at some occasions could not be excluded.

  18. XMM-Newton observation of MACHO 104.20906.960: a dwarf nova candidate with a 2 h period

    CERN Document Server

    Nucita, A A; De Paolis, F; Ingrosso, G; Maiolo, B M T; Guainazzi, M

    2008-01-01

    The binaries known as cataclysmic variables are particular binary systems in which the primary star (a white dwarf) accretes material from a secondary via Roche-lobe mechanism. Usually, these objects have orbital period of a few hours so that a detailed temporal analysis can be performed. Here, we present Chandra ${\\it XMM}$-Newton observations of a dwarf nova candidate identified in the past by optical observations towards the galactic Bulge and labeled as MACHO 104.20906.960. After a spectral analysis, we used the Lomb-Scargle technique for the period search and evaluated the confidence level using Monte-Carlo simulations. In this case, we found that the $X$-ray source shows a period of $2.03_{-0.07}^{+0.09} $ hours (3$\\sigma$ error) so that it is most likely a system of interacting objects. The modulation of the signal was found with a confidence level of $>$99%. The spectrum can be described by a two thermal plasma components with X-ray flux in the 0.3--10 keV energy band of $1.77_{-0.19}^{+0.16}\\times10^...

  19. Disks, Winds, and Veiling Curtains: Dissecting the Ultraviolet Spectrum of the Dwarf Nova Z Camelopardalis in Outburst

    Science.gov (United States)

    Knigge, Christian; Long, Knox S.; Blair, William P.; Wade, Richard A.

    1997-02-01

    We present a far-ultraviolet spectrum of the dwarf nova Z Cam near the peak of a normal outburst as observed with the Hopkins Ultraviolet Telescope (HUT) on the Astro-2 mission. The continuum shape and luminosity are almost identical to an Astro-1 HUT spectrum of the same object in a similar state obtained about 4 years or 50 outburst episodes earlier. This suggests that, following the onset of an outburst, the system quickly reaches a (quasi-) steady state that is insensitive to the interoutburst history. A variance analysis of the Astro-2 data reveals no evidence for spectral variability on a timescale of minutes. The rms amplitude of any intrinsic fluctuations is ignored--or that the standard picture itself may require modification. Blackbody disk models actually match the data better at longer HUT wavelengths, but the redder color of these models is a direct consequence of the neglect of all radiative transfer effects. The same neglect prevents blackbody models from reproducing the turnover in the spectrum and causes them to overpredict the accretion rate. We use a Monte Carlo line profile synthesis code to model five of the high-ionization lines in Z Cam's spectrum in terms of a simple, kinematic description of a rotating, biconical accretion disk wind. Adopting the picture of such an outflow that has recently been proposed for another cataclysmic variable, UX UMa, we find that acceptable fits to the data can be obtained. The relative mean ionization fractions we derive for the ionic species included in our wind modeling appear to be consistent with photoionization by a radiation field with T ~ 1.2 × 105 K. This temperature is within the range that has recently been inferred for Z Cam's soft X-ray component from ROSAT data and similar to the boundary layer temperature that has been derived on the basis of Extreme-Ultraviolet Explorer (EUVE) observations for the dwarf nova U Gem in outburst. An important feature of our adopted outflow model is the existence of

  20. Helium accreting CO white dwarfs with rotation: helium novae instead of double detonation

    CERN Document Server

    Yoon, S C

    2004-01-01

    We present evolutionary models of helium accreting carbon-oxygen white dwarfs in which we include the effects of the spin-up of the accreting star induced by angular momentum accretion, rotationally induced chemical mixing and rotational energy dissipation. Initial masses of 0.6 Msun and 0.8 Msun and constant accretion rates of a few times 10^{-8} Msun/yr of helium rich matter have been considered, which is typical for the sub-Chandrasekhar mass progenitor scenario for Type Ia supernovae. It is found that the helium envelope in an accreting white dwarf is heated efficiently by friction in the differentially rotating spun-up layers. As a result, helium ignites much earlier and under much less degenerate conditions compared to the corresponding non-rotating case. Consequently, a helium detonation may be avoided, which questions the sub-Chandrasekhar mass progenitor scenario for Type Ia supernovae. We discuss implications of our results for the evolution of helium star plus white dwarf binary systems as possible...

  1. The remarkable outburst of the highly-evolved post period-minimum dwarf nova SSS J122221.7-311525

    Science.gov (United States)

    Neustroev, V. V.; Marsh, T. R.; Zharikov, S. V.; Knigge, C.; Kuulkers, E.; Osborne, J. P.; Page, K. L.; Steeghs, D.; Suleimanov, V. F.; Tovmassian, G.; Breedt, E.; Frebel, A.; García-Díaz, Ma. T.; Hambsch, F.-J.; Jacobson, H.; Parsons, S. G.; Ryu, T.; Sabin, L.; Sjoberg, G.; Miroshnichenko, A. S.; Reichart, D. E.; Haislip, J. B.; Ivarsen, K. M.; LaCluyze, A. P.; Moore, J. P.

    2017-01-01

    We report extensive 3-yr multiwavelength observations of the WZ Sge-type dwarf nova SSS J122221.7-311525 during its unusual double superoutburst, the following decline and in quiescence. The second segment of the superoutburst had a long duration of 33 days and a very gentle decline with a rate of 0.02 mag d-1, and it displayed an extended post-outburst decline lasting at least 500 days. Simultaneously with the start of the rapid fading from the superoutburst plateau, the system showed the appearance of a strong NIR excess resulting in very red colours, which reached extreme values (B-I≃1.4) about 20 days later. The colours then became bluer again, but it took at least 250 days to acquire a stable level. Superhumps were clearly visible in the light curve from our very first time-resolved observations until at least 420 days after the rapid fading from the superoutburst. The spectroscopic and photometric data revealed an orbital period of 109.80 min and a fractional superhump period excess ≲0.8%, indicating a very low mass ratio q ≲0.045. With such a small mass ratio the donor mass should be below the hydrogen-burning minimum mass limit. The observed IR flux in quiescence is indeed much lower than is expected from a CV with a near-main sequence donor star. This strongly suggests a brown-dwarf-like nature for the donor and that SSS J122221.7-311525 has already evolved away from the period minimum towards longer periods, with the donor now extremely dim.

  2. Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae. VII: The Seventh Year (2014-2015)

    CERN Document Server

    Kato, Taichi; Dubovsky, Pavol A; Kudzej, Igor; Monard, Berto; Miller, Ian; Itoh, Hiroshi; Kiyota, Seiichiro; Masumoto, Kazunari; Fukushima, Daiki; Kinoshita, Hiroki; Maeda, Kazuki; Mikami, Jyunya; Matsuda, Risa; Kojiguchi, Naoto; Kawabata, Miho; Takenaka, Megumi; Matsumoto, Katsura; de Miguel, Enrique; Maeda, Yutaka; Ohshima, Tomohito; Isogai, Keisuke; Pickard, Roger D; Henden, Arne; Kafka, Stella; Akazawa, Hidehiko; Otani, Noritoshi; Ishibashi, Sakiko; Ogi, Minako; Tanabe, Kenji; Imamura, Kazuyoshi; Stein, William; Kasai, Kiyoshi; Vanmunster, Tonny; Starr, Peter; Pavlenko, Elena P; Antonyuk, Oksana I; Antonyuk, Kirill A; Sosnovskij, Aleksei A; Pit, Nikolaj V; Babina, Julia V; Sklyanov, Aleksandr; Novak, Rudolf; Oksanen, Arto; Dvorak, Shawn; Michel, Raul; Masi, Gianluca; Littlefield, Colin; Ulowetz, Joseph; Shugarov, Sergey Yu; Golysheva, Polina Yu; Chochol, Drahomir; Krushevska, Viktoriia; Ruiz, Javier; Tordai, Tamas; Morelle, Etienne; Sabo, Richard; Maehara, Hiroyuki; Richmond, Michael; Katysheva, Natalia; Hirosawa, Kenji; Goff, William N; Dubois, Franky; Logie, Ludwig; Rau, Steve; Voloshina, Irina B; Andreev, Maksim V; Shiokawa, Kazuhiko; Neustroev, Vitaly V; Sjoberg, George; Zharikov, Sergey; James, Nick; Bolt, Greg; Crawford, Tim; Buczynski, Denis; Cook, Lewis M; Kochanek, Christopher S; Shappee, Benjamin; Stanek, Krzysztof Z; Prieto, Jose L; Denisenko, Denis; Nishimura, Hideo; Mukai, Masaru; Kaneko, Shizuo; Ueda, Seiji; Stubbings, Rod; Moriyama, Masayuki; Schmeer, Patrick; Muyllaert, Eddy; Shears, Jeremy; Modic, Robert J; Paxson, Kevin B

    2015-01-01

    Continuing the project described by Kato et al. (2009, arXiv:0905.1757), we collected times of superhump maxima for 102 SU UMa-type dwarf novae observed mainly during the 2014-2015 season and characterized these objects. Our project has greatly improved the statistics of the distribution of orbital periods, which is a good approximation of the distribution of cataclysmic variables at the terminal evolutionary stage, and confirmed the presence of a period minimum at a period of 0.053 d and a period spike just above this period. The number density monotonically decreased toward the longer period and there was no strong indication of a period gap. We detected possible negative superhumps in Z Cha. It is possible that normal outbursts are also suppressed by the presence of a disk tilt in this system. There was no indication of enhanced orbital humps just preceding the superoutburst, and this result favors the thermal-tidal disk instability as the origin of superoutbursts. We detected superhumps in three AM CVn-ty...

  3. Long-term photometry of the eclipsing dwarf nova V893 Scorpii: Orbital period, oscillations, and a possible giant planet

    CERN Document Server

    Bruch, Albert

    2014-01-01

    The cataclysmic variable V893 Sco is an eclipsing dwarf nova which, apart from outbursts with comparatively low amplitudes, exhibits a particularly strong variability during quiescence on timescales of days to seconds.The present study aims to update the outdated orbital ephemerides published previously, to investigate deviations from linear ephemerides, and to characterize non-random brightness variations in a range of timescales. Light curves of V893 Sco were observed on 39 nights, spanning a total time base of about 14 years. They contain 114 eclipses which were used to significantly improve the precision of the orbital period and to study long-term variations of the time of revolution. Oscillations and similar brightness variations were studied with Fourier techniques in the individual light curves. The orbital period exhibits long-term variations with a cycle time of 10.2 years. They can be interpreted as a light travel time effect caused by the presence of a giant planet with approximately 9.5 Jupiter m...

  4. The orbital and superhump periods of the dwarf nova HS 0417+7445 in Camelopardalis

    CERN Document Server

    Shears, J H; Brady, S; Dubovsky, P; Miller, I; Staels, B

    2010-01-01

    We present the 2005-2010 outburst history of the SUUMa-type dwarf HS 0417+7445,along with a detailed analysis of extensive time-series photometry obtained in March 2008 during the second recorded superoutburst of the system. The mean outburst interval is 197 \\pm 59 d, with a median of 193 d. The March 2008 superoutburst was preceeded by a precursor outburst, had an amplitude of 4.2 magnitudes, and the whole event lasted about 16 days. No superhumps were detected during the decline from the precursor outburst, and our data suggests instead that orbital humps were present during that phase. Early superhumps detected during the rise to the superoutburst maximum exhibited an unusually large fractional period excess of epsilon = 0.137 (Psh = 0.0856(88) d). Following the maximum, a linear decline in brightness followed, lasting at least 6 days. During this decline, a stable superhump period of Psh = 0.07824(2) d was measured. Superimposed on the superhumps were orbital humps, which allowed us to accurately measure ...

  5. Multiwavelength monitoring of a very active dwarf nova AX J1549.8-5416 with an unusually high duty cycle

    Science.gov (United States)

    Zhang, Guobao; Gelfand, Joseph D.; Russell, David M.; Lewis, Fraser; Masetti, Nicola; Bernardini, Federico; Andruchow, Ileana; Zibecchi, L.

    2017-08-01

    We present the results of our analysis of new optical, ultraviolet (UV) and X-ray observations of a highly variable source - AX J1549.8-5416. Both the detection of several fast rise, exponential decay outbursts in the optical light curve and the lack of He ii emission lines in the optical spectra suggest AX J1549.8-5416 is a cataclysmic variable of the dwarf nova (DN) type. The multiwavelength analysis of three mini-outbursts and one normal outburst represent one of the most complete multiwavelength studies of a DN and help to refine the relationship between the X-ray, UV and optical emission in this system. We find that the UV emission is delayed with respect to the optical by 1.0-5.4 d during the rising phase of the outburst. The X-ray emission is suppressed during the peak of the optical outburst and recovers during the end of the outburst. From our analysis of archival Swift, Chandra and XMM-Newton observations of AX J1549.8-5416, we estimate this DN has a high duty cycle (˜50 per cent), suggesting a quiescent X-ray luminosity larger than 1032 erg s-1. We also find the X-ray and UV flux are roughly anticorrelated. Furthermore, we find that, at low X-ray fluxes, the X-ray spectrum is well described by a single temperature thermal plasma model, while at high X-ray fluxes, an isobaric cooling flow model also works. We find that the maximum temperature of the plasma in quiescence is significantly higher than that in outburst.

  6. MASTER: dwarf novae outbursts

    Science.gov (United States)

    Gress, O.; Balanutsa, P.; Lipunov, V.; Gorbovskoy, E.; Otero, S.; Rebolo, R.; Serra-Ricart, M.; Buckley, D.; Tiurina, N. V.; Kuznetsov, A. S.; Kornilov, V. G.; Vladimirov, V. V.; Kuvshinov, D. A.; Chazov, V. V.; Shumkov, V.; Pogrosheva, T.

    2017-02-01

    MASTER-IAC auto-detection system ( Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 30L ) discovered OT source at (RA, Dec) = 15h 05m 18.03s -14d 39m 33.6s on 2017-02-08.27692 UT. The OT unfiltered magnitude is (limit 19.8m).

  7. A multi-wavelength survey of NGC\\,6752: X-ray counterparts, two new dwarf novae, and a core-collapsed radial profile

    CERN Document Server

    Thomson, G S; Dieball, A; Maccarone, T J; Dolphin, A; Zurek, D; Long, K S; Shara, M; Sarajedini, A

    2012-01-01

    We present the results of a multi-wavelength (FUV to I-band) survey of the stellar populations of the globular cluster NGC 6752, using STIS, ACS and WFC3 on board the Hubble Space Telescope. We have confirmed that two previously identified CV candidates are, in fact, dwarf novae which underwent outbursts during our observations. We have also identified previously unknown optical counterparts to two X-ray sources. We estimate the position of the centre of the cluster, and show that the stellar density profile is not well described by a single King model, indicating that this cluster is in a core-collapsed or post-core collapse phase. The colour-magnitude diagram shows a well-populated horizontal branch, numerous blue stragglers and white dwarfs (WDs), as well as 87 sources in the gap region where we expect to find WD - main sequence binaries, including cataclysmic variables (CVs). The X-ray sources and WD binary systems are the most centrally concentrated populations, with dynamically estimated characteristic ...

  8. Magnetic novae

    Science.gov (United States)

    Zemko, Polina; Orio, Marina

    2016-07-01

    We present the results of optical and X-ray observations of two quiescent novae, V2491 Cyg and V4743 Sgr. Our observations suggest the intriguing possibility of localization of hydrogen burning in magnetic novae, in which accretion is streamed to the polar caps. V2491 Cyg was observed with Suzaku more than 2 years after the outburst and V4743 Sgr was observed with XMM Newton 2 and 3.5 years after maximum. In the framework of a monitoring program of novae previously observed as super soft X-ray sources we also obtained optical spectra of V4743 Sgr with the SALT telescope 11.5 years after the eruption and of V2491 Cyg with the 6m Big Azimutal Telescope 4 and 7 years post-outburst. In order to confirm the possible white dwarf spin period of V2491 Cyg measured in the Suzaku observations we obtained photometric data using the 90cm WIYN telescope at Kitt Peak and the 1.2 m telescope in Crimea. We found that V4743 Sgr is an intermediate polar (IP) and V2491 Cyg is a strong IP candidate. Both novae show modulation of their X-ray light curves and have X-ray spectra typical of IPs. The Suzaku and XMM Newton exposures revealed that the spectra of both novae have a very soft blackbody-like component with a temperature close to that of the hydrogen burning white dwarfs in their SSS phases, but with flux by at least two orders of magnitude lower, implying a possible shrinking of emitting regions in the thin atmosphere that is heated by nuclear burning underneath it. In quiescent IPs, independently of the burning, an ultrasoft X-ray flux component originates at times in the polar regions irradiated by the accretion column, but the soft component of V4743 Sgr disappeared in 2006, indicating that the origin may be different from accretion. We suggest it may have been due to an atmospheric temperature gradient on the white dwarf surface, or to continuing localized thermonuclear burning at the bottom of the envelope, before complete turn-off. The optical spectra of V2491 Cyg and V

  9. Voloshina I.B., Metlov V.G., Shugarov S.Yu., Golovin A.V., Antoniuk O.I. Positive and Negative Superhumps of the Dwarf Nova MN Dra

    Science.gov (United States)

    Samsonov, D. A.; Pavlenko, E. P.; Andreev, M. V.; Sklyanov, A.; Zubareva, A. M.

    2010-12-01

    We present the result of O-C analysis of the dwarf nova MN Dra. It is based on the multi-site photometric observations that were made over 77 nights in August - November, 2009. The total exposure was 433 hours. During this time binary underwent two superoutbursts and five normal outbursts. In superoutbursts the positive superhumps decreased with extremely large P = -(3 - 8) x 10-4 for SU UMa-like dwarf novae, confirming the known behavior of MN Dra in 2003. MN Dra displayed large-amplitude (up to 1.4m in quiescence and 0.1m-0.2m in normal outbursts) negative superhumps. The improved value of negative superhump period is 0.095952(4) d.

  10. V1006 Cygni: Dwarf Nova Showing Three Types of Outbursts and Simulating Some Features of the WZ Sge-Type Behavior

    CERN Document Server

    Kato, Taichi; Shchurova, Alisa V; Sosnovskij, Aleksei A; Babina, Julia V; Baklanov, Aleksei V; Shugarov, Sergey Yu; Littlefield, Colin; Dubovsky, Pavol A; Kudzej, Igor; Pickard, Roger D; Isogai, Keisuke; Kimura, Mariko; de Miguel, Enrique; Tordai, Tamas; Chochol, Drahomir; Maeda, Yutaka; Cook, Lewis M; Miller, Ian; Itoh, Hiroshi

    2015-01-01

    We observed the 2015 July-August long outburst of V1006 Cyg and established this object to be an SU UMa-type dwarf nova in the period gap. Our observations have confirmed that V1006 Cyg is the second established object showing three types of outbursts (normal, long normal and superoutbursts) after TU Men. We have succeeded in recording the growing stage of superhumps (stage A superhumps) and obtained a mass ratio of 0.26-0.33, which is close to the stability limit of tidal instability. This identification of stage A superhumps demonstrated that superhumps indeed slowly grow in systems near the stability limit, the idea first introduced by Kato et al. 2014, arXiv:1406.6428). The superoutburst showed a temporary dip followed by a rebrightening. The moment of the dip coincided with the stage transition of superhumps, and we suggest that stage C superhumps is related to the start of the cooling wave in the accretion disk. We interpret that the tidal instability was not strong enough to maintain the disk in the ho...

  11. SOAR observations of the high-viscosity accretion disc of the dwarf nova V4140 Sagitarii in quiescence and in outburst

    CERN Document Server

    Baptista, Raymundo; Oliveira, Alexandre S

    2016-01-01

    We report the analysis of 22 B-band light curves of the dwarf nova V4140 Sgr obtained with SOI/SOAR during two nights along the decline of a superoutburst in 2006 Sep 12-24 and in quiescence over 50 days following the superoutburst. Three-dimensional eclipse mapping of the outburst light curves indicates that the accretion disc is elliptical (eccentricity e=0.13) and that superhump maximum occurs when the mass donor star is aligned with the bulge of the elliptical disc. The accretion disc is geometrically thin both in outburst and in quiescence; it fills the primary Roche lobe in outburst and shrinks to about half this size in quiescence. The stability of the eclipse shape, width and depth along quiescence and the derived disc surface brightness distribution indicate that the quiescent accretion disc is in a high-viscosity, steady-state. Flickering mapping of the quiescent data reveal that the low-frequency flickering arises from an azimuthally-extended stream-disc impact region at disc rim and from the inner...

  12. Extensive photometry of the WZ Sge-type dwarf nova V455 And (HS2331+3905): detection of negative superhumps and coherence features of the short-period oscillations

    CERN Document Server

    Kozhevnikov, V P

    2015-01-01

    We report the results of photometry of the WZ Sge-type dwarf nova V455 And. Observations were obtained over 19 nights in 2013 and 2014. The total duration of the observations was 96 h. We clearly detected three coherent oscillations with periods of 80.376+/-0.003 min, 40.5431+/-0.0004 min and 67.619685+/-0.000040 s. The 67.619685-s period can be the spin period of the white dwarf. The 40.5431-minute period is the first harmonic of the orbital period. The 80.376-minute oscillation can be a negative superhump because its period is 0.9% less than the orbital period. This oscillation was evident both in the data of 2013 and in the data of 2014. These results make V455 And a permanent superhump system which shows negative superhumps. This is also the first detection of persistent negative superhumps in a WZ Sge-type dwarf nova. In addition, the analysis of our data revealed incoherent oscillations with periods in the range 5-6 min, which were observed earlier and accounted for by non-radial pulsations of the white...

  13. Quark-novae in neutron star-white dwarf binaries: a model for luminous (spin-down powered) sub-Chandrasekhar-mass Type Ia supernovae?

    Institute of Scientific and Technical Information of China (English)

    Rachid Ouyed; Jan Staff

    2013-01-01

    We show that,by appealing to a Quark-Nova (QN) in a tight binary system containing a massive neutron star and a CO white dwarf (WD),a Type Ia explosion could occur.The QN ejecta collides with the WD,driving a shock that triggers carbon burning under degenerate conditions (the QN-Ia).The conditions in the compressed low-mass WD (MWD < 0.9 M☉) in our model mimic those of a Chandrasekhar mass WD.The spin-down luminosity from the QN compact remnant (the quark star) provides additional power that makes the QN-Ia light-curve brighter and broader than a standard SN-Ia with similar 56Ni yield.In QNe-Ia,photometry and spectroscopy are not necessarily linked since the kinetic energy of the ejecta has a contribution from spin-down power and nuclear decay.Although QNe-Ia may not obey the Phillips relationship,their brightness and their relatively "normal looking" light-curves mean they could be included in the cosmological sample.Light-curve fitters would be confused by the discrepancy between spectroscopy at peak and photometry and would correct for it by effectively brightening or dimming the QNe-Ia apparent magnitudes,thus over-or under-estimating the true magnitude of these spin-down powered SNe-Ia.Contamination of QNe-Ia in samples of SNe-Ia used for cosmological analyses could systematically bias measurements of cosmological parameters if QNe-Ia are numerous enough at high-redshift.The strong mixing induced by spin-down wind combined with the low 56Ni yields in QNe-Ia means that these would lack a secondary maximum in the i-band despite their luminous nature.We discuss possible QNe-Ia progenitors.

  14. SOAR observations of the high-viscosity accretion disc of the dwarf nova V4140 Sagitarii in quiescence and in outburst

    Science.gov (United States)

    Baptista, Raymundo; Borges, Bernardo W.; Oliveira, Alexandre S.

    2016-12-01

    We report the analysis of 22 B-band light curves of the dwarf nova V4140 Sgr obtained with SOAR Optical Imager (SOI)/SOAR during two nights along the decline of a superoutburst in 2006 September 12-24 and in quiescence over 50 d following the superoutburst. 3D eclipse mapping of the outburst light curves indicates that the accretion disc is elliptical (eccentricity e = 0.13) and that superhump maximum occurs when the mass donor star is aligned with the bulge of the elliptical disc. The accretion disc is geometrically thin both in outburst and in quiescence; it fills the primary Roche lobe in the outburst and shrinks to about half this size in quiescence. The stability of the eclipse shape, width and depth along quiescence and the derived disc surface brightness distribution indicate that the quiescent accretion disc is in a high-viscosity, steady-state. Flickering mapping of the quiescent data reveals that the low-frequency flickering arises from an azimuthally extended stream-disc impact region at disc rim and from the innermost disc region, whereas the high-frequency flickering originates in the accretion disc. Assuming the disc-related flickering to be caused by fluctuations in the energy dissipation rate induced by magnetohydrodynamic turbulence (Geertsema & Achterberg), we find that the quiescent disc viscosity parameter is large, α ≃ 0.2-0.4, at all radii. The high-viscosity quiescent disc and the inferred low disc temperatures in superoutburst are inconsistent with expectations of the disc-instability model, and lead to the conclusion that the outbursts of V4140 Sgr are powered by mass transfer bursts from its donor star.

  15. The awakening of a classical nova from hibernation

    Science.gov (United States)

    Mróz, Przemek; Udalski, Andrzej; Pietrukowicz, Paweł; Szymański, Michał K.; Soszyński, Igor; Wyrzykowski, Łukasz; Poleski, Radosław; Kozłowski, Szymon; Skowron, Jan; Ulaczyk, Krzysztof; Skowron, Dorota; Pawlak, Michał

    2016-09-01

    Cataclysmic variable stars—novae, dwarf novae, and nova-likes—are close binary systems consisting of a white dwarf star (the primary) that is accreting matter from a low-mass companion star (the secondary). From time to time such systems undergo large-amplitude brightenings. The most spectacular eruptions, with a ten-thousandfold increase in brightness, occur in classical novae and are caused by a thermonuclear runaway on the surface of the white dwarf. Such eruptions are thought to recur on timescales of ten thousand to a million years. In between, the system’s properties depend primarily on the mass-transfer rate: if it is lower than a billionth of a solar mass per year, the accretion becomes unstable and the matter is dumped onto the white dwarf during quasi-periodic dwarf nova outbursts. The hibernation hypothesis predicts that nova eruptions strongly affect the mass-transfer rate in the binary, keeping it high for centuries after the event. Subsequently, the mass-transfer rate should significantly decrease for a thousand to a million years, starting the hibernation phase. After that the nova awakes again—with accretion returning to the pre-eruption level and leading to a new nova explosion. The hibernation model predicts cyclical evolution of cataclysmic variables through phases of high and low mass-transfer. The theory gained some support from the discovery of ancient nova shells around the dwarf novae Z Camelopardalis and AT Cancri, but direct evidence for considerable mass-transfer changes prior, during and after nova eruptions has not hitherto been found. Here we report long-term observations of the classical nova V1213 Cen (Nova Centauri 2009) covering its pre- and post-eruption phases and precisely documenting its evolution. Within the six years before the explosion, the system revealed dwarf nova outbursts indicative of a low mass-transfer rate. The post-nova is two orders of magnitude brighter than the pre-nova at minimum light with no trace of

  16. The awakening of a classical nova from hibernation.

    Science.gov (United States)

    Mróz, Przemek; Udalski, Andrzej; Pietrukowicz, Paweł; Szymański, Michał K; Soszyński, Igor; Wyrzykowski, Łukasz; Poleski, Radosław; Kozłowski, Szymon; Skowron, Jan; Ulaczyk, Krzysztof; Skowron, Dorota; Pawlak, Michał

    2016-09-29

    Cataclysmic variable stars-novae, dwarf novae, and nova-likes-are close binary systems consisting of a white dwarf star (the primary) that is accreting matter from a low-mass companion star (the secondary). From time to time such systems undergo large-amplitude brightenings. The most spectacular eruptions, with a ten-thousandfold increase in brightness, occur in classical novae and are caused by a thermonuclear runaway on the surface of the white dwarf. Such eruptions are thought to recur on timescales of ten thousand to a million years. In between, the system's properties depend primarily on the mass-transfer rate: if it is lower than a billionth of a solar mass per year, the accretion becomes unstable and the matter is dumped onto the white dwarf during quasi-periodic dwarf nova outbursts. The hibernation hypothesis predicts that nova eruptions strongly affect the mass-transfer rate in the binary, keeping it high for centuries after the event. Subsequently, the mass-transfer rate should significantly decrease for a thousand to a million years, starting the hibernation phase. After that the nova awakes again-with accretion returning to the pre-eruption level and leading to a new nova explosion. The hibernation model predicts cyclical evolution of cataclysmic variables through phases of high and low mass-transfer. The theory gained some support from the discovery of ancient nova shells around the dwarf novae Z Camelopardalis and AT Cancri, but direct evidence for considerable mass-transfer changes prior, during and after nova eruptions has not hitherto been found. Here we report long-term observations of the classical nova V1213 Cen (Nova Centauri 2009) covering its pre- and post-eruption phases and precisely documenting its evolution. Within the six years before the explosion, the system revealed dwarf nova outbursts indicative of a low mass-transfer rate. The post-nova is two orders of magnitude brighter than the pre-nova at minimum light with no trace of dwarf

  17. Nova Aquila 1919: a nova after all?

    CERN Document Server

    Lau, Herbert H B; Liu, X W

    2010-01-01

    Nova 1919 Aquila is today widely assumed to have been the result of a final helium shell flash occurring on a single post-asymptotic giant branch star. The fact that the outbursting star is in the middle of an old planetary nebula and that the ejecta associated with the outburst is hydrogen deficient supports this diagnosis. However, the material ejected during that outburst is also extremely neon rich, suggesting that it derives from an oxygen-neon-magnesium star, as is the case in the so-called neon novae. We have therefore attempted to construct a scenario that explains all the observations of the nebula and its central star, including the ejecta abundances. We find two scenarios that have the potential to explain the observations, although neither is a perfect match. The first scenario invokes the merger of a main sequence star and a massive oxygen-neon-magnesium white dwarf. The second invokes an oxygen-neon-magnesium classical nova that takes place shortly after a final helium shell flash. The main draw...

  18. Eastern Spruce Dwarf Mistletoe

    Science.gov (United States)

    F. Baker; Joseph O' Brien; R. Mathiasen; Mike Ostry

    2006-01-01

    Eastern spruce dwarf mistletoe (Arceuthobium pusillum) is a parasitic flowering plant that causes the most serious disease of black spruce (Picea mariana) throughout its range. The parasite occurs in the Canadian provinces of Saskatchewan, Manitoba, Ontario, Quebec, New Brunswick, Nova Scotia, Prince Edward Island, and Newfoundland; in the Lake States of Minnesota,...

  19. The Place of Recurrent Novae among the Symbiotic Stars

    CERN Document Server

    Mikolajewska, Joanna

    2008-01-01

    The observational properties of recurrent novae indicate that they can be divided into two subclasses:systems with a dwarf and a red giant secondary, respectively. The second type -- which includes RS Oph -- bears many similarities to symbiotic stars.

  20. Nova Delphini 2013: Backyard Analysis of a Classical Nova

    Science.gov (United States)

    Reid, Piper

    2014-01-01

    On August 14, 2013, Nova Delphini was discovered by Koichi Itagaki. This nova erupted to a maximum brightness of magnitude 4.4 by August 16, 2013. The extraordinary brightness of this event has allowed many amateur astronomers to have the chance to study it. More than 750 amateur astronomers have contributed to the AAVSO photometry database of Nova Delphini.1 The amount and quality of spectroscopic data gathered is unprecedented as well, as over 700 individual spectra have been collected so far in the ARAS database.2 A nova is a class of variable star that undergoes a cataclysmic eruption, which can be observed through a sudden increase in brightness that declines over a series of months or years. At the center of a nova is an accreting white dwarf star which is collecting hydrogen from its surroundings. The accreting mass causes a nuclear reaction on the surface of the white dwarf and as the pressure increases the reaction becomes super-critical and a thermonuclear runaway is ignited causing the brightness increase as well as triggering the ejection of a shell of material form the star. The stages of a classical nova outburst are outlined along with techniques available to amateur astronomers for study of these phenomena. The author’s equipment and software setup are detailed. Results obtained using a low resolution grating, Schmidt-cassegrain telescope and CCD camera that were acquired while Nova Delphini was in the “fireball stage” 3 and subsequent “iron curtain phase”3 are compared and discussed. Results obtained using a high resolution spectroscope, Schmidt-cassegrain telescope and CCD camera that were acquired during the “lifting of the iron curtain phase”3 are also presented. References 1. Turner, Rebecca. “AAVSO - Nova Del 2013” 20 Aug 2013 Web. 8 Sep 2013 2. Tessier, Francois. “ARAS Spectral Database - Nova-Del-2013” 22 Sep 2013 Web. 22 Sep 2013 3. Shore, Steven N. “Spectroscopy of Novae - A User’s Manual” arXiv:1211.3176 [astro

  1. Modelling nova populations in galaxies

    CERN Document Server

    Chen, Hai-Liang; Yungelson, L R; Gilfanov, M; Han, Zhanwen

    2016-01-01

    Theoretical modelling of the evolution of classical and recurrent novae plays an important role in studies of binary evolution, nucleosynthesis and accretion physics. However, from a theoretical perspective the observed statistical properties of novae remain poorly understood. In this paper, we have produced model populations of novae using a hybrid binary population synthesis approach for differing star formation histories (SFHs): a starburst case (elliptical-like galaxies), a constant star formation rate case (spiral-like galaxies) and a composite case (in line with the inferred SFH for M31). We found that the nova rate at 10\\;Gyr in an elliptical-like galaxy is $\\sim 10-20$ times smaller than a spiral-like galaxy with the same mass. The majority of novae in elliptical-like galaxies at the present epoch are characterized by low mass white dwarfs (WDs), long decay times, relatively faint absolute magnitudes and long recurrence periods. In contrast, the majority of novae in spiral-like galaxies at 10\\;Gyr hav...

  2. Hydrodynamic studies of oxygen, neon, and magnesium novae

    Science.gov (United States)

    Starrfield, Sumner; Sparks, W. M.; Truran, J. W.

    1987-01-01

    Results are presented from recent theoretical studies that have examined the properties of nova outbursts on ONeMg white dwarfs. These outbursts are much more violent and occur much more frequently than outbursts on CO white dwarfs. Hydrodynamic simulations of both kinds of outbursts are in excellent agreement with the observations.

  3. Ultraviolet spectroscopy of old novae and symbiotic stars

    Science.gov (United States)

    Lambert, D. L.; Slovak, M. H.; Shields, G. A.; Ferland, G. J.

    1981-01-01

    The IUE spectra are presented for two old novae and for two of the symbiotic variables. Prominent emission line spectra are revealed as a continuum whose appearance is effected by the system inclination. These data provide evidence for hot companions in the symbiotic stars, making plausible the binary model for these peculiar stars. Recent IUE spectra of dwarf novae provide additional support for the existence of optically thick accretion disks in active binary systems. The ultraviolet data of the eclipsing dwarf novae EX Hya and BV Cen appear flatter than for the noneclipsing systems, an effect which could be ascribed to the system inclination.

  4. The Expanding Fireball of Nova Delphini 2013

    CERN Document Server

    Schaefer, G H; Gies, D R; Farrington, C D; Kloppenborg, B; Chesneau, O; Monnier, J D; Ridgway, S T; Scott, N; Tallon-Bosc, I; McAlister, H A; Boyajian, T; Maestro, V; Mourard, D; Meilland, A; Nardetto, N; Stee, P; Sturmann, J; Vargas, N; Baron, F; Ireland, M; Baines, E K; Che, X; Jones, J; Richardson, N D; Roettenbacher, R M; Sturmann, L; Turner, N H; Tuthill, P; van Belle, G; von Braun, K; Zavala, R T; Banerjee, D P K; Ashok, N M; Joshi, V; Becker, J; Muirhead, P S

    2015-01-01

    A classical nova occurs when material accreting onto the surface of a white dwarf in a close binary system ignites in a thermonuclear runaway. Complex structures observed in the ejecta at late stages could result from interactions with the companion during the common envelope phase. Alternatively, the explosion could be intrinsically bipolar, resulting from a localized ignition on the surface of the white dwarf or as a consequence of rotational distortion. Studying the structure of novae during the earliest phases is challenging because of the high spatial resolution needed to measure their small sizes. Here we report near-infrared interferometric measurements of the angular size of Nova Delphini 2013, starting from one day after the explosion and continuing with extensive time coverage during the first 43 days. Changes in the apparent expansion rate can be explained by an explosion model consisting of an optically thick core surrounded by a diffuse envelope. The optical depth of the ejected material changes ...

  5. Novae news

    CERN Multimedia

    2012-01-01

    As announced in the previous Bulletin, Novae has opened a new snack bar on the Flagstaff car park, just a few metres from CERN's reception area (Building 33).   Just a few metres from the CERN Reception, the new Novae snack point welcomes visitors and CERNois. Opening hours Currently: Monday to Friday, 8 a.m. to 4 p.m. From September: Monday to Friday, 7:45 a.m. to 5 p.m.; Saturdays from 8 a.m. to 2 p.m. The snack bar selection includes breakfast, starting at 2.70 CHF, cold dishes from 5 CHF, and hot dishes from 6 CHF.   Novae has also installed a 24-hour-a-day food vending machine in the CERN hostel (Building 39) and in Building 13. You can buy pasta and cooked dishes for 6.50 CHF to 8 CHF. In addition, a groceries vending machine has been installed in the main building, just across from the news kiosk. Nearly 60 different items are available around the clock. Finally, Novae has introduced a new payment system in several buildings on the Meyrin site. It accepts credit ca...

  6. On the long term evolution of white dwarfs in cataclysmic variables and their recurrence times

    Science.gov (United States)

    Sion, E. M.; Starrfield, S. G.

    1985-01-01

    The relevance of the long term quasi-static evolution of accreting white dwarfs to the outbursts of Z Andromeda-like symbiotics; the masses and accretion rates of classical nova white dwarfs; and the observed properties of white dwarfs detected optically and with IUE in low M dot cataclysmic variables is discussed. A surface luminosity versus time plot for a massive, hot white dwarf bears a remarkable similarity to the outburst behavior of the hot blue source in Z Andromeda. The long term quasi-static models of hot accreting white dwarfs provide convenient constraints on the theoretically permissible parameters to give a dynamical (nova-like) outburst of classic white dwarfs.

  7. On Orbital Period Changes in Nova Outbursts

    CERN Document Server

    Martin, Rebecca G; Schaefer, Bradley E

    2011-01-01

    We propose a new mechanism that produces an orbital period change during a nova outburst. When the ejected material carries away the specific angular momentum of the white dwarf, the orbital period increases. A magnetic field on the surface of the secondary star forces a fraction of the ejected material to corotate with the star, and hence the binary system. The ejected material thus takes angular momentum from the binary orbit and the orbital period decreases. We show that for sufficiently strong magnetic fields on the surface of the secondary star, the total change to the orbital period could even be negative during a nova outburst, contrary to previous expectations. Accurate determinations of pre- and post-outburst orbital periods of recurrent nova systems could test the new mechanism, in addition to providing meaningful constraints on otherwise difficult to measure physical quantities. We apply our mechanism to outbursts of the recurrent nova U Sco.

  8. Searching for nova shells around cataclysmic variables

    CERN Document Server

    Sahman, D I; Knigge, C; Marsh, T R

    2015-01-01

    We present the results of a search for nova shells around 101 cataclysmic variables (CVs), using Halpha images taken with the 4.2-m William Herschel Telescope (WHT) and the 2.5-m Isaac Newton Telescope Photometric Halpha Survey of the Northern Galactic Plane (IPHAS). Both telescopes are located on La Palma. We concentrated our WHT search on nova-like variables, whilst our IPHAS search covered all CVs in the IPHAS footprint. We found one shell out of the 24 nova-like variables we examined. The newly discovered shell is around V1315 Aql and has a radius of approx.2.5 arcmin, indicative of a nova eruption approximately 120 years ago. This result is consistent with the idea that the high mass-transfer rate exhibited by nova-like variables is due to enhanced irradiation of the secondary by the hot white dwarf following a recent nova eruption. The implications of our observations for the lifetime of the nova-like variable phase are discussed. We also examined 4 asynchronous polars, but found no new shells around an...

  9. MASTER-OAFA discovery: dwarf nova outburst

    Science.gov (United States)

    Shumkov, V.; Lipunov, V.; Podesta, R.; Levato, H.; Buckley, D.; Tiurina, N.; Balanutsa, P.; Kuznetsov, A.; Gorbovskoy, E.; Kornilov, V.; Chazov, V.; Vlasenko, D.; Vladimirov, V.; Gress, O.; Ivanov, K.; Lopez, C.; Podesta, F.; Saffe, C.; Pogrosheva, T.

    2016-10-01

    MASTER-OAFA (Argentina, San Juan National Univeristy's Observatorio Astronomico Felix Aguilar) auto-detection system ( Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 30L ) discovered OT source at (RA, Dec) = 02h 19m 51.96s -69d 26m 59.6s on 2016-10-18.23277 UT. The OT magnitude in unfiltered is 17.2m (limit 18.3m).

  10. Dynamical Masses of Accreting White Dwarfs

    Science.gov (United States)

    Pala, A. F.; Gänsckie, B. T.

    2017-03-01

    The mass retention efficiency is a key question in both the theoretical and observational study of accreting white dwarfs in interacting binaries, with important implications for their potential as progenitors for type Ia supernovae (SNe Ia). Canonical wisdom is that classical nova eruptions erode the white dwarf mass, and consequently, cataclysmic variables (CVs) have been excluded from the SN Ia progenitor discussion. However the average mass of white dwarfs in CVs is substantially higher (≃ 0.83 M⊙) than that of single white dwarfs (≃ 0.64 M ⊙), in stark contrast to expectations based on current classical nova models. This finding is based on a sample of ≃ 30 CV white dwarfs with accurate mass measurements, most of them in eclipsing systems. Given the fundamental importance of the mass evolution of accreting white dwarfs, it is necessary to enlarge this sample and to diversify the methods used for measuring masses. We have begun a systematic study of 27 CVs to almost double the number of CV white dwarfs with an accurate mass measurement. Using VLT/X-shooter phase-resolved observations, we can measure the white dwarf masses to a few percent, and will be able to answer the question whether accreting CV white dwarfs grow in mass.

  11. Pre-nova X-ray observations of V2491 Cyg (Nova Cyg 2008b)

    CERN Document Server

    Ibarra, A; Osborne, J P; Page, K; Ness, J U; Saxton, R D; Baumgartner, W; Beckmann, V; Bode, M F; Hernanz, M; Mukai, K; Orio, M; Sala, G; Starrfield, S; Wynn, G A

    2009-01-01

    Classical novae are phenomena caused by explosive hydrogen burning on an accreting white dwarf. So far, only one classical nova has been identified in X-rays before the actual optical outburst occurred (V2487 Oph). The recently discovered nova, V2491 Cyg, is one of the fastest (He/N) novae observed so far. Using archival ROSAT, XMM-Newton and Swift data, we show that V2491 Cyg was a persistent X-ray source during its quiescent time before the optical outburst. We present the X-ray spectral characteristics and derive X-ray fluxes. The pre-outburst X-ray emission is variable, and at least in one observation it shows a very soft X-ray source.

  12. Identifying and Quantifying Recurrent Novae Masquerading as Classical Novae

    CERN Document Server

    Pagnotta, Ashley

    2014-01-01

    Recurrent novae (RNe) are cataclysmic variables with two or more nova eruptions within a century. Classical novae (CNe) are similar systems with only one such eruption. Many of the so-called 'CNe' are actually RNe for which only one eruption has been discovered. Since RNe are candidate Type Ia supernova progenitors, it is important to know whether there are enough in our galaxy to provide the supernova rate, and therefore to know how many RNe are masquerading as CNe. To quantify this, we collected all available information on the light curves and spectra of a Galactic, time-limited sample of 237 CNe and the 10 known RNe, as well as exhaustive discovery efficiency records. We recognize RNe as having (a) outburst amplitude smaller than 14.5 - 4.5 * log(t_3), (b) orbital period >0.6 days, (c) infrared colors of J-H > 0.7 mag and H-K > 0.1 mag, (d) FWHM of H-alpha > 2000 km/s, (e) high excitation lines, such as Fe X or He II near peak, (f) eruption light curves with a plateau, and (g) white dwarf mass greater tha...

  13. The Effect of Composition on Nova Ignitions

    CERN Document Server

    Shen, Ken J

    2008-01-01

    The accretion of hydrogen-rich matter onto C/O and O/Ne white dwarfs in binary systems leads to unstable thermonuclear ignition of the accreted envelope, triggering a convective thermonuclear runaway and a subsequent classical, recurrent, or symbiotic nova. Prompted by uncertainties in the composition at the base of the accreted envelope at the onset of convection, as well as the range of abundances detected in nova ejecta, we examine the effects of varying the composition of the accreted material. For high accretion rates and carbon mass fractions 0.002. These different triggering mechanisms, which occur for critical abundances relevant to many nova systems, alter the amount of mass that is accreted prior to a nova, causing the nova rate to depend on accreted composition. Upcoming deep optical surveys such as Pan-STARRS-1, Pan-STARRS-4, and the Large Synoptic Survey Telescope may allow us to detect the dependence of nova rates on accreted composition. Furthermore, the burning and depletion of 3He with a mas...

  14. The Inter-Eruption Timescale of Classical Novae from Expansion of the Z Camelopardalis Shell

    CERN Document Server

    Shara, Michael M; Zurek, David; Martin, Christopher D; Neill, James D; Seibert, Mark

    2012-01-01

    The dwarf nova Z Camelopardalis is surrounded by the largest known classical nova shell. This shell demonstrates that at least some dwarf novae must have undergone classical nova eruptions in the past, and that at least some classical novae become dwarf novae long after their nova thermonuclear outbursts. The current size of the shell, its known distance, and the largest observed nova ejection velocity set a lower limit to the time since Z Cam's last outburst of 220 years. The brightest part of the Z Cam shell's radius is currently p ~ 1690 pixels. No expansion of the radius of the brightest part of the ejecta was detected, with an upper limit of pdot 5,000 years ago. However, including the important effect of deceleration as the ejecta sweeps up interstellar matter in its snowplow phase reduces the lower limit to 1300 years. This is the first strong test of the prediction of nova thermonuclear runaway theory that the inter-outburst times of classical novae are longer than 1000 yr. The intriguing suggestion ...

  15. /sup 7/Li production in Nova explosions

    Energy Technology Data Exchange (ETDEWEB)

    Starrfield, S.; Truran, J.W.; Sparks, W.M.; Arnould, M.

    1978-06-01

    Calculations of /sup 7/Li production occurring as a concomitant of thermonuclear runaways in hydrogen envelopes of white dwarfs are reported. It is found that sufficient /sup 7/Li can be produced in models displaying fast--nova-like features to suggest that the corresponding objects represent significant contributors to the /sup 7/Li enrichment of galactic matter. The sensitivities of these results to various assumptions and uncertainties are discussed.

  16. Synthesis of C-rich dust in CO nova ourbursts

    CERN Document Server

    Jose, Jordi; Eid, Mounib F El

    2016-01-01

    Context. Classical novae are thermonuclear explosions that take place in the envelopes of accreting white dwarfs in stellar binary systems. The material transferred onto the white dwarf piles up under degenerate conditions, driving a thermonuclear runaway. In those outbursts, about 10-7 - 10-3 Msun, enriched in CNO and, sometimes, other intermediate-mass elements (e.g., Ne, Na, Mg, or Al, for ONe novae) are ejected into the interstellar medium. The large concentrations of metals spectroscopically inferred in the nova ejecta reveal that the (solar-like) material transferred from the secondary mixes with the outermost layers of the underlying white dwarf. Aims. Most theoretical models of nova outbursts reported to date yield, on average, outflows characterized by O > C, from which only oxidized condensates (e.g, O-rich grains) would be expected, in principle. Methods. To specifically address whether CO novae can actually produce C-rich dust, six different hydrodynamic nova models have been evolved, from accreti...

  17. A Decade of Progress in Understanding the Eruptions of Classical Novae

    Science.gov (United States)

    Shara, M. M.

    2014-12-01

    During the 11 years since the 2002 Sitges Nova conference, over 700 refereed papers dealing with classical novae have been published. Rather than spend 2.3 seconds reviewing each one, I've tried to focus on the main themes that have captured the interests of most researchers. I've also used, as examples, the most influential and cited papers in each subfield, though a decade from now some of my choices may seem dated, provincial, or flat-out wrong. The key topics that I address include theory and simulations of nova explosions; the recurrent novae; observations of ejecta; symbiotic novae; connections between novae and type Ia supernovae; connections between classical and dwarf novae; extragalactic novae; the maximum magnitude - rate of decline relationship; and a set of challenges and unanswered questions that I hope we will have made much progress on by the time we reassemble around 2024.

  18. The expanding fireball of Nova Delphini 2013.

    Science.gov (United States)

    Schaefer, G H; ten Brummelaar, T; Gies, D R; Farrington, C D; Kloppenborg, B; Chesneau, O; Monnier, J D; Ridgway, S T; Scott, N; Tallon-Bosc, I; McAlister, H A; Boyajian, T; Maestro, V; Mourard, D; Meilland, A; Nardetto, N; Stee, P; Sturmann, J; Vargas, N; Baron, F; Ireland, M; Baines, E K; Che, X; Jones, J; Richardson, N D; Roettenbacher, R M; Sturmann, L; Turner, N H; Tuthill, P; van Belle, G; von Braun, K; Zavala, R T; Banerjee, D P K; Ashok, N M; Joshi, V; Becker, J; Muirhead, P S

    2014-11-13

    A classical nova occurs when material accreting onto the surface of a white dwarf in a close binary system ignites in a thermonuclear runaway. Complex structures observed in the ejecta at late stages could result from interactions with the companion during the common-envelope phase. Alternatively, the explosion could be intrinsically bipolar, resulting from a localized ignition on the surface of the white dwarf or as a consequence of rotational distortion. Studying the structure of novae during the earliest phases is challenging because of the high spatial resolution needed to measure their small sizes. Here we report near-infrared interferometric measurements of the angular size of Nova Delphini 2013, starting one day after the explosion and continuing with extensive time coverage during the first 43 days. Changes in the apparent expansion rate can be explained by an explosion model consisting of an optically thick core surrounded by a diffuse envelope. The optical depth of the ejected material changes as it expands. We detect an ellipticity in the light distribution, suggesting a prolate or bipolar structure that develops as early as the second day. Combining the angular expansion rate with radial velocity measurements, we derive a geometric distance to the nova of 4.54 ± 0.59 kiloparsecs from the Sun.

  19. The Unusually Luminous Extragalactic Nova SN 2010U

    CERN Document Server

    Czekala, Ian; Chornock, R; Pastorello, A; Marion, G H; Margutti, R; Botticella, M T; Challis, P; Ergon, M; Smartt, S; Sollerman, J; Vinkó, J; Wheeler, J C

    2012-01-01

    We present observations of the unusual optical transient SN 2010U, including spectra taken 1.03 days to 15.3 days after maximum light that identify it as a fast and luminous Fe II type nova. Our multi-band light curve traces the fast decline (t_2 = 3.5 days) from maximum light (M_V = -10.2 mag), placing SN 2010U in the top 0.5% of the most luminous novae ever observed. We find typical ejecta velocities of approximately 1100 km/s and that SN 2010U shares many spectral and photometric characteristics with two other fast and luminous Fe II type novae, including Nova LMC 1991 and M31N-2007-11d. For the extreme luminosity of this nova, the maximum magnitude vs. rate of decline relationship indicates a massive white dwarf progenitor with a low pre-outburst accretion rate. However, this prediction is in conflict with emerging theories of nova populations, which predict that luminous novae from massive white dwarfs should preferentially exhibit an alternate spectral type (He/N) near maximum light.

  20. The panchromatic spectroscopic evolution of the classical CO nova V339 Del (Nova Del 2013) until X-ray turnoff

    CERN Document Server

    Shore, S N; Schwarz, G J; Teyssier, F M; Buil, C; Aquino, I De Gennaro; Page, K L; Osborne, J P; Scaringi, S; Starrfield, S; van Winckel, H; Williams, R E; Woodward, C E

    2016-01-01

    Classical novae are the product of thermonuclear runaway-initiated explosions occurring on accreting white dwarfs. V339 Del (Nova Delphinus 2013) was one of the brightest classical novae of the last hundred years. Spectroscopy and photometry are available from $\\gamma$-rays through infrared at stages that have frequently not been well observed. The complete data set is intended to provide a benchmark for comparison with modeling and for understanding more sparsely monitored historical classical and recurrent novae. This paper is the first in the series of reports on the development of the nova. We report here on the early stages of the outburst, through the X-ray active stage. A time sequence of optical, flux calibrated high resolution spectra was obtained with the Nordic Optical Telescope (NOT) using FIES simultaneously, or contemporaneously, with the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope during the early stages of the outburst. These were supplemented with MERCATOR/HE...

  1. Synthesis of C-rich dust in CO nova outbursts

    Science.gov (United States)

    José, Jordi; Halabi, Ghina M.; El Eid, Mounib F.

    2016-09-01

    Context. Classical novae are thermonuclear explosions that take place in the envelopes of accreting white dwarfs in stellar binary systems. The material transferred onto the white dwarf piles up under degenerate conditions, driving a thermonuclear runaway. In these outbursts, about 10-7-10-3 M⊙, enriched in CNO and sometimes other intermediate-mass elements (e.g., Ne, Na, Mg, or Al for ONe novae) are ejected into the interstellar medium. The large concentrations of metals spectroscopically inferred in the nova ejecta reveal that the solar-like material transferred from the secondary mixes with the outermost layers of the underlying white dwarf. Aims: Most theoretical models of nova outbursts reported to date yield, on average, outflows characterized by O > C, from which, in principle, only oxidized condensates (e.g., O-rich grains) would be expected. Methods: To specifically address whether CO novae can actually produce C-rich dust, six different hydrodynamic nova models have been evolved, from accretion to the expansion and ejection stages, with different choices for the composition of the substrate with which the solar-like accreted material mixes. Updated chemical profiles inside the H-exhausted core have been used, based on stellar evolution calculations for a progenitor of 8 M⊙ through H- and He-burning phases. Results: We show that these profiles lead to C-rich ejecta after the nova outburst. This extends the possible contribution of novae to the inventory of presolar grains identified in meteorites, particularly in a number of carbonaceous phases (i.e., nanodiamonds, silicon carbides, and graphites).

  2. The awakening of a classical nova from hibernation

    CERN Document Server

    Mroz, P; Pietrukowicz, P; Szymanski, M K; Soszynski, I; Wyrzykowski, L; Poleski, R; Kozlowski, S; Skowron, J; Ulaczyk, K; Skowron, D; Pawlak, M

    2016-01-01

    Cataclysmic variable stars (CVs) are close binary systems consisting of a white dwarf (primary) that is accreting matter from a low-mass companion star (secondary). From time to time such systems undergo large-amplitude brightenings. The most spectacular eruptions, over $10^4$ times in brightness, occur in classical novae and are caused by a thermonuclear runaway on the surface of the white dwarf. Such eruptions are thought to recur on timescales of $10^4-10^6$. In between, the system's properties depend primarily on the mass-transfer rate: if it is lower than a $10^{-9} M_{\\odot}$/year, the accretion becomes unstable and the matter is dumped onto the white dwarf during quasi-periodic dwarf nova outbursts. The hibernation hypothesis predicts that nova eruptions strongly affect the mass-transfer rate, keeping it high for centuries after the event. Subsequently, the mass-transfer rate should significantly decrease for $10^3-10^6$ years, starting the hibernation phase. After that the nova awakes again - with acc...

  3. THE INTER-ERUPTION TIMESCALE OF CLASSICAL NOVAE FROM EXPANSION OF THE Z CAMELOPARDALIS SHELL

    Energy Technology Data Exchange (ETDEWEB)

    Shara, Michael M.; Mizusawa, Trisha; Zurek, David [Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024-5192 (United States); Martin, Christopher D.; Neill, James D. [Department of Physics, Math and Astronomy, California Institute of Technology, 1200 East California Boulevard, Mail Code 405-47, Pasadena, CA 91125 (United States); Seibert, Mark [Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States)

    2012-09-10

    The dwarf nova Z Camelopardalis is surrounded by the largest known classical nova shell. This shell demonstrates that at least some dwarf novae must have undergone classical nova eruptions in the past, and that at least some classical novae become dwarf novae long after their nova thermonuclear outbursts. The current size of the shell, its known distance, and the largest observed nova ejection velocity set a lower limit to the time since Z Cam's last outburst of 220 years. The radius of the brightest part of Z Cam's shell is currently {approx}880 arcsec. No expansion of the radius of the brightest part of the ejecta was detected, with an upper limit of {<=}0.17 arcsec yr{sup -1}. This suggests that the last Z Cam eruption occurred {>=}5000 years ago. However, including the important effect of deceleration as the ejecta sweeps up interstellar matter in its snowplow phase reduces the lower limit to 1300 years. This is the first strong test of the prediction of nova thermonuclear runaway theory that the interoutburst times of classical novae are longer than 1000 years. The intriguing suggestion that Z Cam was a bright nova, recorded by Chinese imperial astrologers in October-November 77 B.C.E., is consistent with our measurements. If Z Cam was indeed the nova of 77 B.C.E. we predict that its ejecta are currently expanding at 85 km s{sup -1}, or 0.11 arcsec yr{sup -1}. Detection and measurement of this rate of expansion should be possible in just a few years.

  4. Binary Orbits as the Driver of Gamma-Ray Emission and Mass Ejection in Classical Novae

    Science.gov (United States)

    Chomiuk, Laura; Linford, Justin D.; Yang, Jun; O'Brien, T. J.; Paragi, Zsolt; Mioduszewski, Amy J.; Beswick, R. J.; Cheung, C. C.; Mukai, Koji; Nelson, Thomas

    2014-01-01

    Classical novae are the most common astrophysical thermonuclear explosions, occurring on the surfaces of white dwarf stars accreting gas from companions in binary star systems. Novae typically expel about 10 (sup -4) solar masses of material at velocities exceeding 1,000 kilometers per second.However, the mechanism of mass ejection in novae is poorly understood, and could be dominated by the impulsive flash of thermonuclear energy, prolonged optically thick winds or binary interaction with the nova envelope. Classical novae are now routinely detected at giga-electronvolt gamma-ray wavelengths, suggesting that relativistic particles are accelerated by strong shocks in the ejecta. Here we report high-resolution radio imaging of the gamma-ray-emitting nova V959 Mon. We find that its ejecta were shaped by the motion of the binary system: some gas was expelled rapidly along the poles as a wind from the white dwarf, while denser material drifted out along the equatorial plane, propelled by orbital motion..At the interface between the equatorial and polar regions, we observe synchrotron emission indicative of shocks and relativistic particle acceleration, thereby pinpointing the location of gamma-ray production. Binary shaping of the nova ejecta and associated internal shocks are expected to be widespread among novae, explaining why many novae are gamma-ray emitters.

  5. Onset of Convectionon a Pre-Runaway White Dwarf

    CERN Document Server

    Dursi, L J; Alexakis, A; Truran, J W; Rosner, R; Zingale, M A; Fryxell, B; Ricker, P M; Timmes, F X; Olson, K

    2002-01-01

    Observed novae abundances and explosion energies estimated from observations indicate that there must be significant mixing of the heavier material of the white dwarf (C+O) into the lighter accreted material (H+He). Accordingly, nova models must incorporate a mechanism that will dredge up the heavier white dwarf material, and fluid motions from an early convection phase is one proposed mechanism. We present results from two-dimensional simulations of classical nova precursor models that demonstrate the beginning of a convective phase during the `simmering' of a Nova precursor. We use a new hydrostatic equilibrium hydrodynamics module recently developed for the adaptive-mesh code FLASH. The two-dimensional models are based on the one-dimensional models of Ami Glasner, and were evolved with FLASH from a pre-convective state to the onset of convection.

  6. Recovery of old novae

    Directory of Open Access Journals (Sweden)

    L. Schmidtobreick

    2004-01-01

    Full Text Available Durante un proyecto a largo plazo dedicado a la investigaci on de novas cl asicas con explosiones de grandes amplitudes hemos llevado a cabo fotometr a a m ultiples longitudes de onda y espectroscop a optica de varios candidatos de novas viejas. Introducimos aqu el objetivo del proyecto, la b usqueda de novas con baja trans- ferencia de masa y per odos orbitales cortos, y explicamos el m etodo para recuperar estas novas viejas a trav es de sus caracter sticas de color. Finalmente nos concentramos en los primeros resultados para una selecci on de objetos de nuestra muestra.

  7. A classical nova, V2487 Oph 1998, seen in x-rays before and after its explosion.

    Science.gov (United States)

    Hernanz, Margarita; Sala, Glòria

    2002-10-11

    Classical nova explosions are very energetic and frequent phenomena caused by explosive hydrogen burning on top of an accreting white dwarf. Observations of the recent nova V2487 Oph 1998 by the X-ray Multi-Mirror satellite (XMM-Newton) provide evidence that accretion (probably on a magnetic white dwarf) was reestablished as early as 2.7 years after the explosion. In addition, positional correlation with a source previously discovered by the Röntgen Satellite (ROSAT) in 1990 suggests that the site of a nova explosion had been seen in x-rays before the outburst.

  8. The unreasonable effectiveness of experiments in constraining nova nucleosynthesis

    Directory of Open Access Journals (Sweden)

    Parikh Anuj

    2014-01-01

    Full Text Available Classical nova explosions arise from thermonuclear ignition in the envelopes of accreting white dwarfs in close binary star systems. Detailed observations of novae have stimulated numerous studies in theoretical astrophysics and experimental nuclear physics. These phenomena are unusual in nuclear astrophysics because most of the thermonuclear reaction rates thought to be involved are constrained by experimental measurements. This situation allows for rather precise statements to be made about which measurements are still necessary to improve the nuclear physics input to astrophysical models. We briefly discuss desired measurements in these environments with an emphasis on recent experimental progress made to better determine key rates.

  9. Fermi Establishes Classical Novae as a Distinct Class of Gamma-ray Sources

    Science.gov (United States)

    Ackermann, M.; Ajello, M.; Albert, A.; Baldini, L.; Ballet, J.; Bastieri, D.; Bellazzini, R.; Bissaldi, E.; Blandford, R. D.; Bloom, E. D.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caragiulo, M.; Caraveo, P. A.; Ferrara, E. C.; Harding, A. K.; Hays, E.; Perkins, J. S.; Thompson, D. J.

    2014-01-01

    A classical nova results from runaway thermonuclear explosions on the surface of a white dwarf that accretes matter from a low-mass main-sequence stellar companion. In 2012 and 2013, three novae were detected in gamma rays and stood in contrast to the first gamma-ray detected nova V407 Cygni 2010, which belongs to a rare class of symbiotic binary systems. Despite likely differences in the compositions and masses of their white dwarf progenitors, the three classical novae are similarly characterized as soft spectrum transient gamma-ray sources detected over 2-3 week durations. The gamma-ray detections point to unexpected high-energy particle acceleration processes linked to the mass ejection from thermonuclear explosions in an unanticipated class of Galactic gamma-ray sources.

  10. Radioactive Nova Zembla; Nova Zembla radioactief

    Energy Technology Data Exchange (ETDEWEB)

    Duursma, E.

    1996-10-01

    The former Soviet Union dumped radioactive wastes in the seas around the island Nova Zembla (Novaya Zemlya) for decades. Complete nuclear reactors were sunk down. In this non-specialist article the risks from this Cold War heritage are discussed. 4 figs., 1 tab., 1 ref.

  11. Voracious vortexes in cataclysmic variables. Multi-epoch tomographic study of HT Cassiopeia

    CERN Document Server

    Neustroev, V V; Borisov, N V

    2016-01-01

    We present multi-epoch, time-resolved optical spectroscopic observations of the dwarf nova HT Cas, obtained during 1986, 1992, 1995 and 2005 with the aim to study the properties of emission structures in the system. We determined that the accretion disc radius, measured from the double-peaked emission line profiles, is persistently large and lies within the range of 0.45-0.52a, where a is the binary separation. This is close to the tidal truncation radius r_max=0.52a. This result contradicts with previous radius measurements. An extensive set of Doppler maps has revealed a very complex emission structure of the accretion disc. Apart from a ring of disc emission, the tomograms display at least three areas of enhanced emission: the hot spot from the area of interaction between the gas stream and the disc, which is superposed on the elongated spiral structure, and the extended bright region on the leading side of the disc, opposite to the location of the hot spot. The position of the hot spot in all the emission...

  12. The Thermonuclear Runaway and the Classical Nova Outburst

    CERN Document Server

    Starrfield, S; Hix, W R

    2016-01-01

    Nova explosions occur on the white dwarf component of a Cataclysmic Variable binary stellar system that is accreting matter lost by its companion. When sufficient material has been accreted by the white dwarf, a thermonuclear runaway occurs and ejects material in what is observed as a Classical Nova explosion. We describe both the recent advances in our understanding of the progress of the outburst and outline some of the puzzles that are still outstanding. We report on the effects of improving both the nuclear reaction rate library and including a modern nuclear reaction network in our one-dimensional, fully implicit, hydrodynamic computer code. In addition, there has been progress in observational studies of Supernovae Ia with implications about the progenitors and we discuss that in this review.

  13. Strangelet dwarfs

    CERN Document Server

    Alford, Mark G; Reddy, Sanjay

    2011-01-01

    If the surface tension of quark matter is low enough, quark matter is not self bound. At sufficiently low pressure and temperature, it will take the form of a crystal of positively charged strangelets in a neutralizing background of electrons. In this case there will exist, in addition to the usual family of strange stars, a family of low-mass large-radius objects analogous to white dwarfs, which we call "strangelet dwarfs". Using a generic parametrization of the equation of state of quark matter, we calculate the mass-radius relationship of these objects.

  14. A Thousand and One Nova Outbursts

    CERN Document Server

    Epchtein, N; Kovetz, A; Prialnik, D

    2006-01-01

    Multicycle nova evolution models have been calculated over the past twenty years, the number being limited by numerical constraints. Here we present a long-term evolution code that enables a continuous calculation through an unlimited number of nova cycles for an unlimited evolution time, even up to (or exceeding) a Hubble time. Starting with two sets of the three independent nova parameters -- the white dwarf mass, the temperature of its isothermal core, and the rate of mass transfer on to it -- we have followed the evolution of two models, with initial masses of 1 and 0.65 solar masses, accretion rates (constant throughout each calculation) of 1e-11 and 1e-9 solar-masses/yr, and relatively high initial temperatures (as they are likely to be at the onset of the outburst phase), through over 1000 and over 3000 cycles, respectively. The results show that although on the short-term consecutive outbursts are almost identical, on the long-term scale the characteristics change. This is mainly due to the changing c...

  15. Recurrent Novae - A Review

    CERN Document Server

    Mukai, Koji

    2014-01-01

    In recent years, recurrent nova eruptions are often observed very intensely in wide range of wavelengths from radio to optical to X-rays. Here I present selected highlights from recent multi-wavelength observations. The enigma of T Pyx is at the heart of this paper. While our current understanding of CV and symbiotic star evolution can explain why certain subset of recurrent novae have high accretion rate, that of T Pyx must be greatly elevated compared to the evolutionary mean. At the same time, we have extensive data to be able to estimate how the nova envelope was ejected in T Pyx, and it turns to be a rather complex tale. One suspects that envelope ejection in recurrent and classical novae in general is more complicated than the textbook descriptions. At the end of the review, I will speculate that these two may be connected.

  16. 5-HT system and cognition.

    Science.gov (United States)

    Meneses, A

    1999-12-01

    The study of 5-hydroxytryptamine (5-HT) system has benefited from the identification, classification and cloning of multiple 5-HT receptors (5-HT1 to 5-HT7). Growing evidence suggests that 5-HT is important in learning and memory and all its receptors might be implicated in this. Actually, 5-HT pathways, 5-HT reuptake site/transporter complex and 5-HT receptors show regional distribution in brain areas implicated in learning and memory. Likewise, the stimulation or blockade of presynaptic 5-HT1A, 5-HT1B, 5-HT(2A/2C) and 5-HT3 receptors, postsynaptic 5-HT(2B/2C) and 5-HT4 receptors and 5-HT uptake/transporter sites modulate these processes. Available evidence strongly suggests that the 5-HT system may be important in normal function, the treatment and/or pathogenesis of cognitive disorders. Further investigation will help to specify the 5-HT system nature involvement in cognitive processes, pharmacotherapies, their mechanisms and action sites and to determine under which conditions they could operate. In this regard, it is probable that selective drugs with agonists, neutral antagonist, agonists or inverse agonist properties for 5-HT1A, 5-HT(1B/1D), 5-HT(2A/2B/2C), 5-HT4 and 5-HT7 receptors could constitute a new therapeutic opportunity for learning and memory alterations.

  17. 3D Hydrodynamic Simulation of Classical Novae Explosions

    Science.gov (United States)

    Kendrick, Coleman J.

    2015-01-01

    This project investigates the formation and lifecycle of classical novae and determines how parameters such as: white dwarf mass, star mass and separation affect the evolution of the rotating binary system. These parameters affect the accretion rate, frequency of the nova explosions and light curves. Each particle in the simulation represents a volume of hydrogen gas and are initialized randomly in the outer shell of the companion star. The forces on each particle include: gravity, centrifugal, coriolis, friction, and Langevin. The friction and Langevin forces are used to model the viscosity and internal pressure of the gas. A velocity Verlet method with a one second time step is used to compute velocities and positions of the particles. A new particle recycling method was developed which was critical for computing an accurate and stable accretion rate and keeping the particle count reasonable. I used C++ and OpenCL to create my simulations and ran them on two Nvidia GTX580s. My simulations used up to 1 million particles and required up to 10 hours to complete. My simulation results for novae U Scorpii and DD Circinus are consistent with professional hydrodynamic simulations and observed experimental data (light curves and outburst frequencies). When the white dwarf mass is increased, the time between explosions decreases dramatically. My model was used to make the first prediction for the next outburst of nova DD Circinus. My simulations also show that the companion star blocks the expanding gas shell leading to an asymmetrical expanding shell.

  18. SW Sex stars, old novae, and the evolution of cataclysmic variables

    CERN Document Server

    Schmidtobreick, Linda

    2014-01-01

    The population of cataclysmic variables with orbital periods right above the period gap are dominated by systems with extremely high mass transfer rates, the so-called SW Sextantis stars. On the other hand, some old novae in this period range which are expected to show high mass transfer rate instead show photometric and/or spectroscopic resemblance to low mass transfer systems like dwarf novae. We discuss them as candidates for so-called hibernating systems, CVs that changed their mass transfer behaviour due to a previously experienced nova outburst. This paper is designed to provide input for further research and discussion as the results as such are still very preliminary.

  19. On Heavy Element Enrichment in Classical Novae

    CERN Document Server

    Alexakis, A; Heger, A; Brown, E F; Dursi, L J; Truran, J W; Rosner, R; Lamb, D Q; Timmes, F X; Fryxell, B; Zingale, M A; Ricker, P M; Olson, K

    2004-01-01

    Many classical nova ejecta are enriched in CNO and Ne. Rosner et al. recently suggested that the enrichment might originate in the resonant interaction between large-scale shear flows in the accreted H/He envelope and gravity waves at the interface between the envelope and the underlying C/O white dwarf. The shear flow amplifies the waves, which eventually form cusps and break. This wave breaking injects a spray of C/O into the superincumbent H/He. Using two-dimensional simulations, we formulate a quantitative expression for the amount of C/O that can be entrained into the H/He at saturation. The fraction of the envelope that is enriched depends on the shear velocity and density contrast between the C/O white dwarf and the H/He layer but is roughly independent of the shape of the shear profile. Using this parameterization for the mixed mass, we then perform several one-dimensional Lagrangian calculations of an accreting white dwarf envelope and consider two scenarios: that the wave breaking and mixing is driv...

  20. SWIFT X-RAY OBSERVATIONS OF CLASSICAL NOVAE. II. THE SUPER SOFT SOURCE SAMPLE

    Energy Technology Data Exchange (ETDEWEB)

    Schwarz, Greg J. [American Astronomical Society, 2000 Florida Avenue, NW, Suite 400, Washington, DC 20009-1231 (United States); Ness, Jan-Uwe [XMM-Newton Science Operations Centre, ESAC, Apartado 78, 28691 Villanueva de la Canada, Madrid (Spain); Osborne, J. P.; Page, K. L.; Evans, P. A.; Beardmore, A. P. [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); Walter, Frederick M. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States); Andrew Helton, L. [SOFIA Science Center, USRA, NASA Ames Research Center, M.S. N211-3, Moffett Field, CA 94035 (United States); Woodward, Charles E. [Minnesota Institute of Astrophysics, 116 Church Street S.E., University of Minnesota, Minneapolis, MN 55455 (United States); Bode, Mike [Astrophysics Research Institute, Liverpool John Moores University, Birkenhead CH41 1LD (United Kingdom); Starrfield, Sumner [School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287-1404 (United States); Drake, Jeremy J., E-mail: Greg.Schwarz@aas.org [Smithsonian Astrophysical Observatory, 60 Garden Street, MS 3, Cambridge, MA 02138 (United States)

    2011-12-01

    The Swift gamma-ray burst satellite is an excellent facility for studying novae. Its rapid response time and sensitive X-ray detector provides an unparalleled opportunity to investigate the previously poorly sampled evolution of novae in the X-ray regime. This paper presents Swift observations of 52 Galactic/Magellanic Cloud novae. We included the X-Ray Telescope (0.3-10 keV) instrument count rates and the UltraViolet and Optical Telescope (1700-8000 A) filter photometry. Also included in the analysis are the publicly available pointed observations of 10 additional novae the X-ray archives. This is the largest X-ray sample of Galactic/Magellanic Cloud novae yet assembled and consists of 26 novae with Super Soft X-ray emission, 19 from Swift observations. The data set shows that the faster novae have an early hard X-ray phase that is usually missing in slower novae. The Super Soft X-ray phase occurs earlier and does not last as long in fast novae compared to slower novae. All the Swift novae with sufficient observations show that novae are highly variable with rapid variability and different periodicities. In the majority of cases, nuclear burning ceases less than three years after the outburst begins. Previous relationships, such as the nuclear burning duration versus t{sub 2} or the expansion velocity of the eject and nuclear burning duration versus the orbital period, are shown to be poorly correlated with the full sample indicating that additional factors beyond the white dwarf mass and binary separation play important roles in the evolution of a nova outburst. Finally, we confirm two optical phenomena that are correlated with strong, soft X-ray emission which can be used to further increase the efficiency of X-ray campaigns.

  1. White dwarf-red dwarf binaries in the Galaxy

    NARCIS (Netherlands)

    Besselaar, E.J.M. van den

    2007-01-01

    This PhD thesis shows several studies on white dwarf - red dwarf binaries. White dwarfs are the end products of most stars and red dwarfs are normal hydrogen burning low-mass stars. White dwarf - red dwarf binaries are both blue (white dwarf) and red (red dwarf). Together with the fact that they are

  2. Classical Novae in Andromeda: Light Curves from the Palomar Transient Factory and GALEX

    CERN Document Server

    Cao, Yi; Neill, James D; Kulkarni, S R; Lou, Yu-Qing; Ben-Ami, Sagi; Bloom, Joshua S; Cenko, S Bradley; Law, Nicholas M; Nugent, Peter E; Ofek, Eran O; Poznanski, Dovi; Quimby, Robert M

    2012-01-01

    We present optical light curves of twenty-nine novae in M31 during the 2009 and 2010 observing seasons of the Palomar Transient Factory (PTF). The dynamic and rapid cadences in PTF monitoring of M31, from one day to even ten minutes, provide excellent temporal coverage of nova light curves, enabling us to record the photometric evolution of M31 novae in unprecedented detail. We also detect eight of these novae in the near ultraviolet (UV) band with the Galaxy Evolution Explorer (GALEX) satellite. Novae M31N2009-10b and 2010-11a show prominent UV emission peaking a few days prior to their optical maxima, possibly implying aspherical outbursts. Additionally, our blue-shifted spectrum of the recent outburst of PT And (M31N2010-12a) indicates that it is a recurrent nova in M31 and not a dwarf nova in the Milky Way as was previously assumed. Finally, we systematically searched for novae in all confirmed globular clusters of M31 and found only M31N 2010-10f associated with Bol 126. The specific nova rate in the M31...

  3. CLASSICAL NOVAE IN ANDROMEDA: LIGHT CURVES FROM THE PALOMAR TRANSIENT FACTORY AND GALEX

    Energy Technology Data Exchange (ETDEWEB)

    Cao Yi; Lou Yuqing [Tsinghua Center for Astrophysics (THCA), Department of Physics, Tsinghua University, Beijing 100084 (China); Kasliwal, Mansi M.; Neill, James D.; Kulkarni, S. R.; Quimby, Robert M. [Astronomy Department, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Ben-Ami, Sagi [Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100 (Israel); Bloom, Joshua S.; Cenko, S. Bradley; Nugent, Peter E. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Law, Nicholas M. [Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, M5S 3H4 Ontario (Canada); Ofek, Eran O. [Benoziyo Center for Astrophysics, Faculty of Physics, Weizmann Institute of Science, Rehovot 76100 (Israel); Poznanski, Dovi, E-mail: ycao@astro.caltech.edu [School of Physics and Astronomy, Tel-Aviv University, Tel Aviv 69978 (Israel)

    2012-06-20

    We present optical light curves of 29 novae in M31 during the 2009 and 2010 observing seasons of the Palomar Transient Factory (PTF). The dynamic and rapid cadences in PTF monitoring of M31, from one day to ten minutes, provide excellent temporal coverage of nova light curves, enabling us to record the photometric evolution of M31 novae in unprecedented detail. We also detect eight of these novae in the near-ultraviolet (UV) band with the Galaxy Evolution Explorer (GALEX) satellite. Novae M31N 2009-10b and M31N 2010-11a show prominent UV emission peaking a few days prior to their optical maxima, possibly implying aspherical outbursts. Additionally, our blueshifted spectrum of the recent outburst of PT And (M31N 2010-12a) indicates that it is a recurrent nova in M31 and not a dwarf nova in the Milky Way as was previously assumed. Finally, we systematically searched for novae in all confirmed globular clusters (GCs) of M31 and found only M31N 2010-10f associated with Bol 126. The specific nova rate in the M31 GC system is thus about one per year, which is not enhanced relative to the rate outside the GC system.

  4. MESA and NuGrid Simulations of Classical Nova Outbursts: ONe Nova and Nucleosynthesis

    CERN Document Server

    Denissenkov, Pavel A; Pignatari, Marco; Trappitsch, Reto; Ritter, Christian; Herwig, Falk; Battino, Umberto; Setoodehnia, Kiana

    2013-01-01

    Classical novae are the result of thermonuclear flashes of H accreted by CO or ONe white dwarfs, leading eventually to the dynamic ejection of the surface layers. These are observationally known to be enriched in heavy elements, such as C, O and Ne that must originate in layers below the H-flash convection zone. Building on our previous work we now present stellar evolution simulations of ONe nova, and provide a comprehensive comparison of our models with previous work. Some of our models include exponential convective boundary mixing model to account for the observed enrichment of the ejecta even when accreting material with a solar abundance distribution. Our models produce maximum temperature evolution profiles and nucleosynthesis yields in good agreement with models that generate enriched ejecta by assuming that the accreted material was pre-enriched. We confirm for ONe nova the result we reported previously, i.e. we found that 3He can be produced in situ in solar-composition envelopes accreted with slow ...

  5. New Novae snack point

    CERN Multimedia

    2012-01-01

    Located next to the car park by the flag poles, a few metres from the Main CERN Reception (building 33), a new snack point catered by Novae will open to the public on Wednesday 8 August. More information will be available in the next issue of the Bulletin!

  6. Aprendizagens e novas tecnologias

    Directory of Open Access Journals (Sweden)

    Pedro Demo*

    2011-06-01

    Full Text Available Pretendo aqui, muito preliminarmente, reunir alguns argumentos favoráveis à multiplicidade de oportunidades de aprender que o aluno pode encontrar hoje em ambientes de aprendizagem mediados por novas tecnologias. Centro-me principalmente na desconstrução de algumas resistências pedagógicas (EVANS, 2001 ainda persistentes entre nós como “transmissão de conteúdos”; agarramento a uma única teoria; fixação na aula instrucionista; extirpação/endeusamento de processos avaliativos, etc. Procuro ver, em um vasto âmbito de ofertas teóricas, componentes atualmente ressaltados na discussão tecnológica em vigor, com o objetivo de indicar oportunidades de reconstrução muito aproveitável de autores e clássicos, uma vez que aprender bem não foi algo inventado pelas novas tecnologias; sempre existiu e os grandes pedagogos tiveram consciência disso, insinuando infinitas maneiras de aprender bem (DEMO, 2008. As novas tecnologias proporcionam oportunidades ainda mais ampliadas, em meio também a enormes riscos e desacertos. O que menos interessa aqui é incidir em panaceias tecnológicas, bem a gosto do consumismo neoliberal. Interessa, porém, explorar novas oportunidades de aprendizagem, bem mais centradas na atividade dos alunos, flexíveis, motivadoras e capazes de sustentar processos de autoria e autonomia.

  7. Naming Disney's Dwarfs.

    Science.gov (United States)

    Sidwell, Robert T.

    1980-01-01

    Discusses Disney's version of the folkloric dwarfs in his production of "Snow White" and weighs the Disney rendition of the dwarf figure against the corpus of traits and behaviors pertaining to dwarfs in traditional folklore. Concludes that Disney's dwarfs are "anthropologically true." (HOD)

  8. Binary orbits as the driver of gamma-ray emission and mass ejection in classical novae

    CERN Document Server

    Chomiuk, Laura; Yang, Jun; O'Brien, T J; Paragi, Zsolt; Mioduszewski, Amy J; Beswick, R J; Cheung, C C; Mukai, Koji; Nelson, Thomas; Ribeiro, Valerio A R M; Rupen, Michael P; Sokoloski, J L; Weston, Jennifer; Zheng, Yong; Bode, Michael F; Eyres, Stewart; Roy, Nirupam; Taylor, Gregory B

    2014-01-01

    Classical novae are the most common astrophysical thermonuclear explosions, occurring on the surfaces of white dwarf stars accreting gas from companions in binary star systems. Novae typically expel ~10^(-4) solar masses of material at velocities exceeding 1,000 kilometres per second. However, the mechanism of mass ejection in novae is poorly understood, and could be dominated by the impulsive flash of thermonuclear energy, prolonged optically thick winds, or binary interaction with the nova envelope. Classical novae are now routinely detected in gigaelectronvolt gamma-ray wavelengths, suggesting that relativistic particles are accelerated by strong shocks in the ejecta. Here we report high-resolution radio imaging of the gamma-ray-emitting nova V959 Mon. We find that its ejecta were shaped by the motion of the binary system: some gas was expelled rapidly along the poles as a wind from the white dwarf, while denser material drifted out along the equatorial plane, propelled by orbital motion. At the interface ...

  9. Brown Dwarf Companions to White Dwarfs

    CERN Document Server

    Burleigh, M R; Dobbie, P D; Farihi, J; Napiwotzki, R; Maxted, P F L; Barstow, M A; Jameson, R F; Casewell, S L; Gänsicke, B T; Marsh, T R

    2011-01-01

    Brown dwarf companions to white dwarfs are rare, but recent infra-red surveys are slowly reveal- ing examples. We present new observations of the post-common envelope binary WD0137-349, which reveals the effects of irradiation on the ~ 0.05M* secondary, and new observations of GD 1400 which show that it too is a close, post-comon envelope system. We also present the lat- est results in a near-infrared photometric search for unresolved ultracool companions and to white dwarfs with UKIDSS. Twenty five DA white dwarfs were identified as having photometric excesses indicative of a low mass companion, with 8-10 of these having a predicted mass in the range asso- ciated with brown dwarfs. The results of this survey show that the unresolved (< 2") brown dwarf companion fraction to DA white dwarfs is 0.3 \\leq fWD+BD \\leq 1.3%.

  10. Direct Three-body Triple-$\\alpha$ in Helium Novae

    CERN Document Server

    Connolly, Ryan; Brown, Edward F

    2016-01-01

    In AM CVn binaries, a white dwarf primary accretes material from a helium-rich white dwarf or stellar companion. The unstable ignition of nuclear burning via the $3\\alpha$ reaction in an accumulated helium layer powers a thermonuclear runaway near accretion rates $\\dot{M} \\lesssim 10^{-6} \\, \\mathrm{M_{\\odot} \\ yr^{-1}}$ that may be observed as helium nova or .Ia supernova. Helium burning in the primary's envelope at temperatures $T \\lesssim 10^{8} \\, \\mathrm{K}$ may proceed via the direct three-body fusion of $\\alpha$-particles. Here we show that the direct three-body rate by Nguyen et al. (2012) -- which is reduced relative to the extrapolated resonant rate at temperatures $T \\gtrsim 5 \\times 10^{7} \\, \\mathrm{K}$ -- results in novae with longer recurrence times and larger ignition masses. By contrast, we find that the enhancement in the direct three-body rate at temperatures below $T \\lesssim 5 \\times 10^{7} \\, \\mathrm{K}$ does not result in significant differences in nova outburst properties. The most mas...

  11. A LIGHT CURVE ANALYSIS OF CLASSICAL NOVAE: FREE-FREE EMISSION VERSUS PHOTOSPHERIC EMISSION

    Energy Technology Data Exchange (ETDEWEB)

    Hachisu, Izumi [Department of Earth Science and Astronomy, College of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902 (Japan); Kato, Mariko, E-mail: hachisu@ea.c.u-tokyo.ac.jp, E-mail: mariko@educ.cc.keio.ac.jp [Department of Astronomy, Keio University, Hiyoshi, Kouhoku-ku, Yokohama 223-8521 (Japan)

    2015-01-10

    We analyzed light curves of seven relatively slower novae, PW Vul, V705 Cas, GQ Mus, RR Pic, V5558 Sgr, HR Del, and V723 Cas, based on an optically thick wind theory of nova outbursts. For fast novae, free-free emission dominates the spectrum in optical bands rather than photospheric emission, and nova optical light curves follow the universal decline law. Faster novae blow stronger winds with larger mass-loss rates. Because the brightness of free-free emission depends directly on the wind mass-loss rate, faster novae show brighter optical maxima. In slower novae, however, we must take into account photospheric emission because of their lower wind mass-loss rates. We calculated three model light curves of free-free emission, photospheric emission, and their sum for various white dwarf (WD) masses with various chemical compositions of their envelopes and fitted reasonably with observational data of optical, near-IR (NIR), and UV bands. From light curve fittings of the seven novae, we estimated their absolute magnitudes, distances, and WD masses. In PW Vul and V705 Cas, free-free emission still dominates the spectrum in the optical and NIR bands. In the very slow novae, RR Pic, V5558 Sgr, HR Del, and V723 Cas, photospheric emission dominates the spectrum rather than free-free emission, which makes a deviation from the universal decline law. We have confirmed that the absolute brightnesses of our model light curves are consistent with the distance moduli of four classical novae with known distances (GK Per, V603 Aql, RR Pic, and DQ Her). We also discussed the reason why the very slow novae are about ∼1 mag brighter than the proposed maximum magnitude versus rate of decline relation.

  12. V4743 Sgr, a magnetic nova?

    Science.gov (United States)

    Zemko, P.; Orio, M.; Mukai, K.; Bianchini, A.; Ciroi, S.; Cracco, V.

    2016-08-01

    Two XMM-Newton observations of Nova V4743 Sgr (Nova Sgr 2002) were performed shortly after it returned to quiescence, 2 and 3.5 yr after the explosion. The X-ray light curves revealed a modulation with a frequency of ≃0.75 mHz, indicating that V4743 Sgr is most probably an intermediate polar (IP). The X-ray spectra have characteristics in common with known IPs, with a hard thermal plasma component that can be fitted only assuming a partially covering absorber. In 2004, the X-ray spectrum had also a supersoft blackbody-like component, whose temperature was close to that of the white dwarf (WD) in the supersoft X-ray phase following the outburst, but with flux by at least two orders of magnitude lower. In quiescent IPs, a soft X-ray flux component originates at times in the polar regions irradiated by an accretion column, but the supersoft component of V4743 Sgr disappeared in 2006, indicating a possible origin different from accretion. We suggest that it may have been due to an atmospheric temperature gradient on the WD surface, or to continuing localized thermonuclear burning at the bottom of the envelope, before complete turn-off. An optical spectrum obtained with Southern African Large Telescope (SALT) 11.5 yr after the outburst showed a prominent He II λ4686 line and the Bowen blend, which reveal a very hot region, but with peak temperature shifted to the ultraviolet range. V4743 Sgr is the third post-outburst nova and IP candidate showing a low-luminosity supersoft component in the X-ray flux a few years after the outburst.

  13. The Galactic Nova Rate Revisited

    CERN Document Server

    Shafter, A W

    2016-01-01

    Despite its fundamental importance, a reliable estimate of the Galactic nova rate has remained elusive. Here, the overall Galactic nova rate is estimated by extrapolating the observed rate for novae reaching $m\\leq2$ to include the entire Galaxy using a two component disk plus bulge model for the distribution of stars in the Milky Way. The present analysis improves on previous work by considering important corrections for incompleteness in the observed rate of bright novae. Several models are considered to account for differences in the assumed properties of bulge and disk nova populations. The simplest models, which assume uniform properties between bulge and disk novae, predict Galactic nova rates between $\\sim$50 to as many as $\\sim$100 per year, depending on the assumed incompleteness at bright magnitudes. Models where the disk novae are assumed to be more luminous than bulge novae are explored, and predict nova rates up to 30% lower, in the range of $\\sim$35 to $\\sim$70 per year. An average of the most p...

  14. Vila Nova de Gaia

    OpenAIRE

    Almeida, Salvador de Pinho Ferreira de

    2012-01-01

    Tese de doutoramento em Geografia, no ramo de Geografia Física, apresentado à Faculdade de Letras da Universidade de Coimbra The Old Historic Centre of Vila Nova de Gaia is a real living document of the life conditions and construction techniques of ancestral generations representative of cultural values, namely historical, architectural, urbanistic or just emotional that cannot be lost by neglect or carelessness, as they constitute a collective memory. It is necessary to draw ...

  15. Observations and Analysis of the GK Persei Nova Shell and its "Jet-like" Feature

    CERN Document Server

    Harvey, E; Boumis, P; Akras, S

    2016-01-01

    GK Persei (1901, the 'Firework Nebula') is an old but bright nova remnant that offers a chance to probe the physics and kinematics of nova shells. The kinematics in new and archival longslit optical echelle spectra were analysed using the shape software. New imaging from the Aristarchos telescope continues to track the proper motion, extinction and structural evolution of the knots, which have been observed intermittently over several decades. We present for the first time, kinematical constraints on a large faint 'jet' feature, that was previously detected beyond the shell boundary. These observational constraints allow for the generation of models for individual knots, interactions within knot complexes, and the 'jet' feature. Put together, and taking into account dwarf-nova accelerated winds emanating from the central source, these data and models give a deeper insight into the GK Per nova remnant as a whole.

  16. Chandra Discovers Eruption and Pulsation in Nova Outburst

    Science.gov (United States)

    2001-09-01

    NASA's Chandra X-ray Observatory has discovered a giant outburst of X-rays and unusual cyclical pulsing from a white dwarf star that is closely orbiting another star -- the first time either of these phenomena has been seen in X-rays. The observations are helping scientists better understand the thermonuclear explosions that occur in certain binary star systems. The observations of Nova Aquilae were reported today at the "Two Years of Science with Chandra" symposium by an international team led by Sumner Starrfield of Arizona State University. "We found two important results in our Chandra observations. The first was an underlying pulsation every 40 minutes in the X-ray brightness, which we believe comes from the cyclical expansion and contraction of the outer layers of the white dwarf," said Starrfield. "The other result was an enormous flare of X-rays that lasted for 15 minutes. Nothing like this has been seen before from a nova, and we don't know how to explain it." Novas occur on a white dwarf (a star which used up all its nuclear fuel and shrank to roughly the size of the Earth) that is orbiting a normal size star. Strong gravity tides drag hydrogen gas off the normal star and onto the white dwarf, where it can take more than 100,000 years for enough hydrogen to accumulate to ignite nuclear fusion reactions. Gradually, these reactions intensify until a cosmic-sized hydrogen bomb blast results. The outer layers of the white dwarf are then blown away, producing a nova outburst that can be observed for a period of months to years as the material expands into space. "Chandra has allowed us to see deep into the gases ejected by this giant explosion and extract unparalleled information on the evolution of the white dwarf whose surface is exploding," said Jeremy Drake of the Harvard-Smithsonian Center for Astrophysics. The brightening of Nova Aquilae was first detected by optical astronomers in December 1999. "Although this star is at a distance of more than 6

  17. Atmospheres of Brown Dwarfs

    CERN Document Server

    Helling, Christiane

    2014-01-01

    Brown Dwarfs are the coolest class of stellar objects known to date. Our present perception is that Brown Dwarfs follow the principles of star formation, and that Brown Dwarfs share many characteristics with planets. Being the darkest and lowest mass stars known makes Brown Dwarfs also the coolest stars known. This has profound implication for their spectral fingerprints. Brown Dwarfs cover a range of effective temperatures which cause brown dwarfs atmospheres to be a sequence that gradually changes from a M-dwarf-like spectrum into a planet-like spectrum. This further implies that below an effective temperature of < 2800K, clouds form already in atmospheres of objects marking the boundary between M-Dwarfs and brown dwarfs. Recent developments have sparked the interest in plasma processes in such very cool atmospheres: sporadic and quiescent radio emission has been observed in combination with decaying Xray-activity indicators across the fully convective boundary.

  18. UY Puppis A New Anomalous Z Cam Type Dwarf Nova

    CERN Document Server

    Stubbings, Rod

    2016-01-01

    The defining characteristic of Z Cam stars are standstills in their light curves. Some Z Cams exhibit atypical behaviour by going into outburst from a standstill. It has previously been suggested that UY Pup had been a Z Cam star, but it was ruled out due to its long-term light curve. However, in December 2015 UY Pup went into outburst and unexpectedly entered into a short standstill instead of returning to quiescence. Furthermore, UY Pup exhibited additional unusual behaviour with two outbursts detected during its standstill. After this standstill UY Pup made a brief excursion to a quiescence state and slowly rose to a longer and well-defined standstill, where it again went into another outburst. Through comparative analysis, researching and observational data of UY Pup it is evident and thus concluded that it is indeed a Z Cam star, in which renders it to be one of only four known anomalous Z Cam stars.

  19. Eclipse studies of the dwarf-nova Ex Draconis

    CERN Document Server

    Baptista, R; Da Costa, L N

    2000-01-01

    We report on high speed photometry of EX Dra in quiescence and in outburst.The analysis of the lightcurves indicates that the outbursts do not start inthe outer disc regions. The disc expands during rise to maximum and shrinksduring decline and along the quiescent period. At the end of two outbursts thesystem was seen to go through a phase of lower brightness, characterized by anout-of-eclipse level ~15 per cent lower than the typical quiescent level and bythe fairly symmetric eclipse of a compact source at disc centre with littleevidence of a bright spot at disc rim. New eclipse timings were measured and arevised ephemeris was derived. The residuals with respect to the linearephemeris are well described by a sinusoid of amplitude 1.2 minutes and period\\~4 years and are possibly related to a solar-like magnetic activity cycle inthe secondary star. Eclipse phases of the compact central source and of thebright spot were used to derive the geometry of the binary. By constraining thegas stream trajectory to pass ...

  20. Accretion-disc model spectra for dwarf-nova stars

    OpenAIRE

    Idan, Irit; Lasota, Jean-Pierre; Hameury, Jean-Marie; Shaviv, Giora

    2008-01-01

    Radiation from accretion discs in cataclysmic variable stars (CVs) provides fundamental information about the properties of these close binary systems and about the physics of accretion in general. The detailed diagnostics of accretion disc structure can be achieved by including in its description all the relevant heating and cooling physical mechanism, in particular the convective energy transport that, although dominant at temperatures less than about 10 000 K, is usually not taken into acc...

  1. Photometry of the long period dwarf nova MU Centauri

    CERN Document Server

    Bruch, Albert

    2016-01-01

    Even among the brigher cataclysmic variables an appreciable number of objects exist about which not much is known. One of them, MU Cen, was observed as part of a small project to better characterize these neglected systems. The temporal variations of the brightness of MU Cen during quiescence were studied in order to find clues to the structure of the system and its behaviour on time scales of hours and shorter. Light curves observed in white light at a time resolution of a few seconds and with a duration of several hours, obtained in six nights and spanning a total time base of five months, were investigated using different time series analysis tools, as well as model fits. The light curve of MU Cen is dominated by ellipsoidal variations of the secondary star. The refined orbital period is P(orb) = 0.341883 days. Model fits permit to constrain the temperature of the secondary star to ~5000 K and the orbital inclination to 50 deg <= i \\<= 65 deg. The latter result permits estimates of the component mass...

  2. The Formation of Cataclysmic Variables: The Influence of Nova Eruptions

    Science.gov (United States)

    Nelemans, G.; Siess, L.; Repetto, S.; Toonen, S.; Phinney, E. S.

    2016-01-01

    The theoretical and observed populations of pre-cataclysmic variables are dominated by systems with low-mass white dwarfs (WDs), while the WD masses in cataclysmic variables (CVs) are typically high. In addition, the space density of CVs is found to be significantly lower than in the theoretical models. We investigate the influence of nova outbursts on the formation and initial evolution of CVs. In particular, we calculate the stability of the mass transfer in the case where all of the material accreted on the WD is lost in classical novae and part of the energy to eject the material comes from a common-envelope-like interaction with the companion. In addition, we study the effect of an asymmetry in the mass ejection that may lead to small eccentricities in the orbit. We find that a common-envelope-like ejection significantly decreases the stability of the mass transfer, particularly for low-mass WDs. Similarly, the influence of asymmetric mass loss can be important for short-period systems and even more so for low-mass WDs; however, this influence likely disappears long before the next nova outburst due to orbital circularization. In both cases the mass-transfer rates increase, which may lead to observable (and perhaps already observed) consequences for systems that do survive to become CVs. However, a more detailed investigation of the interaction between nova ejecta and the companion and the evolution of slightly eccentric CVs is needed before definite conclusions can be drawn.

  3. Three-dimensional simulations of turbulent convective mixing in ONe and CO classical nova explosions

    Science.gov (United States)

    Casanova, Jordi; José, Jordi; García-Berro, Enrique; Shore, Steven N.

    2016-10-01

    Classical novae are thermonuclear explosions that take place in the envelopes of accreting white dwarfs in binary systems. The material piles up under degenerate conditions, driving a thermonuclear runaway. The energy released by the suite of nuclear processes operating at the envelope heats the material up to peak temperatures of (1-4) × 108 K. During these events, about 10-3-10-7 M⊙, enriched in CNO and, sometimes, other intermediate-mass elements (e.g., Ne, Na, Mg, Al) are ejected into the interstellar medium. To account for the gross observational properties of classical novae (in particular, the high concentrations of metals spectroscopically inferred in the ejecta), models require mixing between the (solar-like) material transferred from the secondary and the outermost layers (CO- or ONe-rich) of the underlying white dwarf. Recent multidimensional simulations have demonstrated that Kelvin-Helmholtz instabilities can naturally produce self-enrichment of the accreted envelope with material from the underlying white dwarf at levels that agree with observations. However, the feasibility of this mechanism has been explored in the framework of CO white dwarfs, while mixing with different substrates still needs to be properly addressed. Three-dimensional simulations of mixing at the core-envelope interface during nova outbursts have been performed with the multidimensional code FLASH, for two types of substrates: CO- and ONe-rich. We show that the presence of an ONe-rich substrate, as in "neon novae", yields higher metallicity enhancements in the ejecta than CO-rich substrates (i.e., non-neon novae). A number of requirements and constraints for such 3D simulations (e.g., minimum resolution, size of the computational domain) are also outlined. Movies associated to Fig. 1 are available at http://www.aanda.org

  4. NOVAS TECNOLOGIAS NO ENVELHECIMENTO

    Directory of Open Access Journals (Sweden)

    Rosa Maria Farah

    2010-02-01

    Full Text Available O Programa de Estudos Pós-Graduados em Gerontologia/PUC-SP desenvolve pesquisas em diversificadas linhas algumas das quais têm em comum o acolhimento à questão das novas tecnologias no envelhecimento. São investigações de caráter interdisciplinar que envolvem docentes-pesquisadores, orientandos de mestrado e de iniciação científica. Na área da educação a distância, a PUC-SP inaugura um trabalho em que o idoso interessado em avançar em seus conhecimentos é recebido em um ambiente virtual de aprendizagem, em que pode participar de cursos avançados de aquisição de novas linguagens e de navegação na Internet, cujas consequências são o investimento em uma via mais digna para o envelhecer no sentido de esse idoso sentir-se um ser ligado aos novos tempos em que a interatividade digital traz-lhe possibilidades ilimitadas de contatos com o outro, com o mundo enfim. A pesquisa sobre a inclusão cibersocial do idoso mostra o que significa colocar o idoso em contato com a Internet, quando este recebe, por meio das redes sociais, ofertas de várias ordens, e equipamentos que contornam limitações de ordem física ou motora. Além disso, o registro digital da memória do idoso, de sua história e referências também podem constituir conteudos preciosos para pesquisas. A relação do idoso com a informática pode situá-lo como um ator, produtor e reprodutor no ciberespaço. Isso significa que as vantagens do uso do computador fazem o idoso ganhar novo sentido na vida, na medida em que pode assim preencher o vazio causado pelas perdas que lhe vão ocorrendo, possibilitando que ele redimensione seu olhar para o presente e futuro. Palavras-chave: o sujeito-idoso nas novas tecnologias; novas tecnologias e envelhecimento; o idoso na educação a distância; internet na velhice.

  5. Investigating Dwarf Spiral Galaxies

    Science.gov (United States)

    Weerasooriya, Sachithra; Dunn, Jacqueline M.

    2017-01-01

    Several studies have proposed that dwarf elliptical / spheroidal galaxies form through the transformation of dwarf irregular galaxies. Early and late type dwarfs resemble each other in terms of their observed colors and light distributions (each can often be represented by exponential disks), providing reason to propose an evolutionary link between the two types. The existence of dwarf spirals has been largely debated. However, more and more recent studies are using the designation of dwarf spiral to describe their targets of interest. This project seeks to explore where dwarf spirals fit into the above mentioned evolutionary sequence, if at all. Optical colors will be compared between a sample of dwarf irregular, dwarf elliptical, and dwarf spiral galaxies. The dwarf irregular and dwarf elliptical samples have previously been found to overlap in both optical color and surface brightness profile shape when limiting the samples to their fainter members. A preliminary comparison including the dwarf spiral sample will be presented here, along with a comparison of available ultraviolet and near-infrared data. Initial results indicate a potential evolutionary link that merits further investigation.

  6. Recurrent Novae in M31

    CERN Document Server

    Shafter, A W; Rector, T A; Schweizer, F; Hornoch, K; Orio, M; Pietsch, W; Darnley, M J; Williams, S C; Bode, M F; Bryan, J

    2014-01-01

    The reported positions of 964 suspected nova eruptions in M31 recorded through the end of calendar year 2013 have been compared in order to identify recurrent nova candidates. To pass the initial screen and qualify as a recurrent nova candidate two or more eruptions were required to be coincident within 0.1', although this criterion was relaxed to 0.15' for novae discovered on early photographic patrols. A total of 118 eruptions from 51 potential recurrent nova systems satisfied the screening criterion. To determine what fraction of these novae are indeed recurrent the original plates and published images of the relevant eruptions have been carefully compared. This procedure has resulted in the elimination of 27 of the 51 progenitor candidates (61 eruptions) from further consideration as recurrent novae, with another 8 systems (17 eruptions) deemed unlikely to be recurrent. Of the remaining 16 systems, 12 candidates (32 eruptions) were judged to be recurrent novae, with an additional 4 systems (8 eruptions) b...

  7. High energy emission of symbiotic recurrent novae: RS Ophiuchi and V407 Cygni

    CERN Document Server

    Hernanz, Margarita

    2011-01-01

    Recurrent novae occurring in symbiotic binaries are candidate sources of high energy photons, reaching GeV energies. Such emission is a consequence of particle acceleration leading to pion production. The shock between matter ejected by the white dwarf, undergoing a nova explosion, and the wind from the red giant companion is responsible for such a process, which mimics a supernova remnant but with much smaller energetic output and much shorter time scales. Inverse Compton can also be responsible for high energy emission. Recent examples are V407 Cyg, detected by Fermi, and RS Oph, which unfortunately exploded in 2006, before Fermi was launched.

  8. High energy X-ray emission from recurrent novae in quiescence: T CrB

    CERN Document Server

    Luna, Gerardo J M; Mukai, Koji

    2007-01-01

    We present Suzaku X-ray observations of the recurrent nova T CrB in quiescence. T CrB is the first recurrent nova to be detected in the hard-X-ray band (E ~ 40.0 keV) during quiescence. The X-ray spectrum is consistent with cooling-flow emission emanating from an optically thin region in the boundary layer of an accretion disk around the white dwarf. The detection of strong stochastic flux variations in the light curve supports the interpretation of the hard X-ray emission as emanating from a boundary layer.

  9. Franchising in Nova Scotia

    Energy Technology Data Exchange (ETDEWEB)

    Hoffman, G. [Nova Scotia Petroleum Directorate, Halifax, NS (Canada)

    1998-09-01

    Opportunities for the local distribution of natural gas in Nova Scotia were reviewed, with special emphasis on franchising. Franchising in Nova Scotia began in 1980, made possible by the passage of the Gas Utilities Act and the Pipeline Act which promised western Canadian natural gas to eastern Canada. However, proposals for franchisees to distribute natural gas in the province were abandoned as the hope for natural gas transmission service to the province faded. The plummeting of world oil prices by the mid-1980s was also a contributory factor. Discovery and development of natural gas facilities around Sable Island led to the September 1997 proclamation of the Gas Distribution Act, which also led to the revival of interest in franchising. The Act provides for the competitive marketing of natural gas as a commodity and the regulation of the gas delivery system under a franchise agreement. Competitive applications are expected early in 1998, with awards of franchises in late 1998. Construction and gas delivery services should begin operations late in 1999.

  10. Terra Nova update

    Energy Technology Data Exchange (ETDEWEB)

    Carrick, G. [Petro-Canada, Inc. (Canada)

    2002-07-01

    This power point presentation shows a location map of the offshore oil and gas fields found off the Grand Banks of Newfoundland. It depicts the proximity of the Terra Nova oil field to Hibernia, White Rose, and the Hebron/Ben Nevis oil fields. The progress of the Terra Nova project since 2001 is described along with the commissioning challenges regarding turret and moorings as well as its modules, underwater components, flow lines, offshore marine operation, well construction and offshore start up. The 2002 operations schedule is also presented, along with production performance, and drilling/completions performance. A chart depicting environment, health and safety (EHS) indicators show that the current focus is on achieving superior environmental performance, injury free and to achieve the EHS performance target in the leading/lagging indicator ratio. Other current issues include the achievement of stable gas compression and sustained production, and to test the full capacity of the FPSO up to 150,000 barrels per day. The drivers of the first quartile performance include unit lifting costs, operating costs, and production efficiency. Operating costs include maintenance, platform support, logistics, onshore support, and well work. The project signifies tremendous growth opportunities for the east coast offshore petroleum industry. tabs., figs.

  11. Nova Mus 2008 = QY Mus

    Science.gov (United States)

    Templeton, Matthew R.

    2008-10-01

    Nova Mus 2008 = QY Mus was discovered by William Liller, Vina del Mar, Chile, on 2008 September 28.998 UT at magnitude 8.6 (Tech Pan film + orange filter). The position is RA = 13h 16m 36.44s , Dec = -67d 36m 47.8s (from P. Nelson). This object was announced as a nova in IAU Circular 8990 (Daniel W.E. Green, editor). The nova classification was determined using low-resolution spectra by W. Liller indicating the presence of broad H-alpha lines at least 2300 angstroms wide. Several observers confirmed the nova and provided photometry. The position above was provided by Peter Nelson (Ellinbank, Vic., Aus.), and is averaged from four separate exposures (rms error approx. 0.4 arcseconds). The GCVS team have formally designated Nova Mus 2008 as QY MUS. Observations should be reported to the AAVSO International Database as QY MUS.

  12. Radiative shocks create environments for dust formation in classical novae

    Science.gov (United States)

    Derdzinski, Andrea M.; Metzger, Brian D.; Lazzati, Davide

    2017-08-01

    Classical novae commonly show evidence of rapid dust formation within months of the outburst. However, it is unclear how molecules and grains are able to condense within the ejecta, given the potentially harsh environment created by ionizing radiation from the white dwarf. Motivated by the evidence for powerful radiative shocks within nova outflows, we propose that dust formation occurs within the cool, dense shell behind these shocks. We incorporate a simple molecular chemistry network and classical nucleation theory with a model for the thermodynamic evolution of the post-shock gas, in order to demonstrate the formation of both carbon and forsterite (Mg2SiO4) grains. The high densities due to radiative shock compression (n ∼ 1014 cm-3) result in CO saturation and rapid dust nucleation. Grains grow efficiently to large sizes ≳ 0.1 μm, in agreement with IR observations of dust-producing novae, and with total dust masses sufficient to explain massive extinction events such as V705 Cas. As in dense stellar winds, dust formation is CO-regulated, with carbon-rich flows producing carbon-rich grains and oxygen-rich flows primarily forming silicates. CO is destroyed by non-thermal particles accelerated at the shock, allowing additional grain formation at late times, but the efficiency of this process appears to be low. Given observations showing that individual novae produce both carbonaceous and silicate grains, we concur with previous works attributing this bimodality to chemical heterogeneity of the ejecta. Nova outflows are diverse and inhomogeneous, and the observed variety of dust formation events can be reconciled by different abundances, the range of shock properties, and the observer viewing angle. The latter may govern the magnitude of extinction, with the deepest extinction events occurring for observers within the binary equatorial plane.

  13. Newly Identified Rydberg Emission Lines in Novae

    Science.gov (United States)

    Lynch, David K.; Rudy, R. J.; Bernstein, L. S.

    2008-09-01

    Newly Identified Rydberg Emission Lines in Novae David K. Lynch, Richard. J. Rudy (The Aerospace Corporation) & Lawrence S. Bernstein (Spectral Sciences, Inc.) Novae spectra in the near infrared frequently show a set of six emission lines that have not been positively identified (Williams, Longmore, & Geballe 1996, MNRAS, 279, 804; Lynch et al. 2001, AJ, 122, 2013; Rudy et al. 2002 ApJ, 573, 794; Lynch et al. 2004 Astron. J. 127, 1089-1097). These lines are at 0.8926, 1.1114, 1.1901, 1.5545, 2.0996 and 2.425 µm ± 0.005 µm. Krautter et al. (1984 A&A 137, 304) suggested that three of the lines were due to rydberg (hydrogenic) transitions in an unspecified atomic species that was in the 4th or 5th ionization stage (core charge = 4 & 5). We believe that Krautter et al.'s explanation is correct based on 4 additional lines that we have identified in the visible and near infrared spectrum of V723 Cassiopeiae. The observed Rydberg lines appear to originate from high angular momentum states with negligible quantum defects. The species cannot be determined with any certainty because in rydberg states, the outer electron sees a nucleus shielded by the inner electrons and together the inner atom appears to have a charge of +1, like hydrogen. As a result, the atom looks hydrogenic and species such as CV, NV, OV, MgV, SiV, etc. have their rydberg transitions at very similar wavelengths. All the lines represent permitted transitions, most likely formed by recombination. Atoms with core charges 4, 5 & 6 are rarely seen in the astrophysical environment because an extremely hot radiation field is necessary to ionize them. Thermonuclear runaways on the surface of a white dwarf can reach millions of degrees K, and thus there are enough X-ray photons available to achieve the necessary high ionization levels.

  14. Light Curve Analysis of Neon Novae

    CERN Document Server

    Hachisu, Izumi

    2015-01-01

    We analyzed light curves of five neon novae, QU Vul, V351 Pup, V382 Vel, V693 CrA, and V1974 Cyg, and determined their white dwarf (WD) masses and distance moduli on the basis of theoretical light curves composed of free-free and photospheric emission. For QU Vul, we obtained a distance of d~2.4 kpc, reddening of E(B-V)~0.55, and WD mass of M_WD=0.82-0.96 M_sun. This suggests that an oxygen-neon WD lost a mass of more than ~0.1 M_sun since its birth. For V351 Pup, we obtained d~5.5 kpc, E(B-V)~0.45, and M_WD=0.98-1.1 M_sun. For V382 Vel, we obtained d~1.6 kpc, E(B-V)~0.15, and M_WD=1.13-1.28 M_sun. For V693 CrA, we obtained d~7.1 kpc, E(B-V)~0.05, and M_WD=1.15-1.25 M_sun. For V1974 Cyg, we obtained d~1.8 kpc, E(B-V)~0.30, and M_WD=0.95-1.1 M_sun. For comparison, we added the carbon-oxygen nova V1668 Cyg to our analysis and obtained d~5.4 kpc, E(B-V)~0.30, and M_WD=0.98-1.1 M_sun. In QU Vul, photospheric emission contributes 0.4-0.8 mag at most to the optical light curve compared with free-free emission only....

  15. RECURRENT NOVAE IN M31

    Energy Technology Data Exchange (ETDEWEB)

    Shafter, A. W. [Department of Astronomy, San Diego State University, San Diego, CA 92182 (United States); Henze, M. [European Space Astronomy Centre, P.O. Box 78, E-28692 Villanueva de la Cañada, Madrid (Spain); Rector, T. A. [Department of Physics and Astronomy, University of Alaska Anchorage, 3211 Providence Dr., Anchorage, AK 99508 (United States); Schweizer, F. [Carnegie Observatories, 813 Santa Barbara St., Pasadena, CA 91101 (United States); Hornoch, K. [Astronomical Institute, Academy of Sciences, CZ-251 65 Ondřejov (Czech Republic); Orio, M. [Astronomical Observatory of Padova (INAF), I-35122 Padova (Italy); Pietsch, W. [Max Planck Institute for Extraterrestrial Physics, P.O. Box 1312, Giessenbachstr., D-85741, Garching (Germany); Darnley, M. J.; Williams, S. C.; Bode, M. F. [Astrophysics Research Institute, Liverpool John Moores University, Liverpool L3 5RF (United Kingdom); Bryan, J., E-mail: aws@nova.sdsu.edu [McDonald Observatory, Austin, TX 78712 (United States)

    2015-02-01

    The reported positions of 964 suspected nova eruptions in M31 recorded through the end of calendar year 2013 have been compared in order to identify recurrent nova (RN) candidates. To pass the initial screen and qualify as a RN candidate, two or more eruptions were required to be coincident within 0.′1, although this criterion was relaxed to 0.′15 for novae discovered on early photographic patrols. A total of 118 eruptions from 51 potential RN systems satisfied the screening criterion. To determine what fraction of these novae are indeed recurrent, the original plates and published images of the relevant eruptions have been carefully compared. This procedure has resulted in the elimination of 27 of the 51 progenitor candidates (61 eruptions) from further consideration as RNe, with another 8 systems (17 eruptions) deemed unlikely to be recurrent. Of the remaining 16 systems, 12 candidates (32 eruptions) were judged to be RNe, with an additional 4 systems (8 eruptions) being possibly recurrent. It is estimated that ∼4% of the nova eruptions seen in M31 over the past century are associated with RNe. A Monte Carlo analysis shows that the discovery efficiency for RNe may be as low as 10% that for novae in general, suggesting that as many as one in three nova eruptions observed in M31 arise from progenitor systems having recurrence times ≲100 yr. For plausible system parameters, it appears unlikely that RNe can provide a significant channel for the production of Type Ia supernovae.

  16. Mixing in classical novae: a 2-D sensitivity study

    CERN Document Server

    Casanova, Jordi; Garcia-Berro, Enrique; Calder, Alan; Shore, Steven N

    2010-01-01

    Classical novae are explosive phenomena that take place in stellar binary systems. They are powered by mass transfer from a low-mass, main sequence star onto a white dwarf. The material piles up under degenerate conditions and a thermonuclear runaway ensues. The energy released by the suite of nuclear processes operating at the envelope heats the material up to peak temperatures of ~ (1 - 4) \\times 108 K. During these events, about 10-4 - 10-5 M\\odot, enriched in CNO and other intermediate-mass elements, are ejected into the interstellar medium. To account for the gross observational properties of classical novae (in particular, a metallicity enhancement in the ejecta above solar values), numerical models assume mixing between the (solar-like) material transferred from the companion and the outermost layers (CO- or ONe-rich) of the underlying white dwarf. The nature of the mixing mechanism that operates at the core-envelope interface has puzzled stellar modelers for about 40 years. Here we investigate the rol...

  17. Construction and compression of Dwarf

    Institute of Scientific and Technical Information of China (English)

    XIANG Long-gang; FENG Yu-cai; GUI Hao

    2005-01-01

    There exists an inherent difficulty in the original algorithm for the construction of Dwarf, which prevents it from constructing true Dwarfs. We explained when and why it introduces suffix redundancies into the Dwarf structure. To solve this problem, we proposed a completely new algorithm called PID. It bottom-up computes partitions of a fact table, and inserts them into the Dwarf structure. Ifa partition is an MSV partition, coalesce its sub-Dwarf; otherwise create necessary nodes and cells. Our performance study showed that PID is efficient. For further condensing of Dwarf, we proposed Condensed Dwarf, a more compressed structure, combining the strength of Dwarf and Condensed Cube. By eliminating unnecessary stores of "ALL" cells from the Dwarf structure, Condensed Dwarf could effectively reduce the size of Dwarf, especially for Dwarfs of the real world, which was illustrated by our experiments. Its query processing is still simple and, only two minor modifications to PID are required for the construction of Condensed Dwarf.

  18. Olivier Chesneau's Work on Novae

    Science.gov (United States)

    Millour, F.; Lagadec, E.

    2015-12-01

    Olivier Chesneau founded a brand new field of observational astrophysics with his attempts to resolve the novae expanding fireball from the very first days of the explosion. With the images he could get, he showed that novae do indeed explode in an aspherical way, leading to a change of paradigm for the physics of these yet-poorly understood catastrophic systems. He also set the stage for a new way of estimating novae distances, by directly measuring the sky-size of the fireball and comparing it with spectroscopic scales, taking into account the tremendous effects of the fireball geometry.

  19. Olivier Chesneau's work on novae

    CERN Document Server

    Millour, Florentin

    2016-01-01

    Olivier Chesneau founded a brand new field of observational astrophysics with his attempts to resolve the novae expanding fireball from the very first days of the explosion. With the images he could get, he showed that novae do indeed explode in an aspherical way, leading to a change of paradigm for the physics of these yet-poorly understood catastrophic systems. He also set the stage for a new way of estimating novae distances, by directly measuring the sky-size of the fireball and comparing it with spectroscopic scales, taking into account the tremendous effects of the fireball geometry.

  20. Three-dimensional simulations of turbulent convective mixing in ONe and CO classical nova explosions

    CERN Document Server

    Casanova, Jordi; Garcia-Berro, Enrique; Shore, Steven N

    2016-01-01

    Classical novae are thermonuclear explosions that take place in the envelopes of accreting white dwarfs in binary systems. The material piles up under degenerate conditions, driving a thermonuclear runaway. The energy released by the suite of nuclear processes operating at the envelope heats the material up to peak temperatures about 100 - 400 MK. During these events, about 10-3 - 10-7 Msun, enriched in CNO and, sometimes, other intermediate-mass elements (e.g., Ne, Na, Mg, Al) are ejected into the interstellar medium. To account for the gross observational properties of classical novae (in particular, the large concentrations of metals spectroscopically inferred in the ejecta), models require mixing between the (solar-like) material transferred from the secondary and the outermost layers (CO- or ONe-rich) of the underlying white dwarf. Recent multidimensional simulations have demonstrated that Kelvin-Helmholtz instabilities can naturally produce self-enrichment of the accreted envelope with material from the...

  1. V5852 Sgr: An Unusual Nova Possibly Associated with the Sagittarius Stream

    CERN Document Server

    Aydi, E; Whitelock, P A; Mohamed, S; Wyrzykowski, Ł; Udalski, A; Vaisanen, P; Nagayama, T; Dominik, M; Scholz, A; Onozato, H; Williams, R E; Hodgkin, S T; Nishiyama, S; Yamagishi, M; Smith, A M S; Ryu, T; Iwamatsu, A; Kawamata, I

    2016-01-01

    We report spectroscopic and photometric follow-up of the peculiar nova V5852~Sgr (discovered as OGLE-2015-NOVA-01), which exhibits a combination of features from different nova classes. The photometry shows a flat-topped light curve with quasi-periodic oscillations, then a smooth decline followed by two fainter recoveries in brightness. Spectroscopy with the Southern African Large Telescope shows first a classical nova with an Fe II or Fe IIb spectral type. In the later spectrum, broad emissions from helium, nitrogen and oxygen are prominent and the iron has faded which could be an indication to the start of the nebular phase. The line widths suggest ejection velocities around $1000\\,{\\rm km\\,s^{-1}}$. The nova is in the direction of the Galactic bulge and is heavily reddened by an uncertain amount. The $V$ magnitude 16 days after maximum enables a distance to be estimated and this suggests that the nova may be in the extreme trailing stream of the Sagittarius dwarf spheroidal galaxy. If so it is the first no...

  2. Radiative shocks create environments for dust formation in novae

    CERN Document Server

    Derdzinski, Andrea M; Lazzati, Davide

    2016-01-01

    Classical novae commonly show evidence of rapid dust formation within months of the outburst. However, it is unclear how molecules and grains are able to condense within the ejecta given the potentially harsh environment created by ionizing radiation from the white dwarf. Motivated by the evidence for powerful radiative shocks within nova outflows, we propose that dust formation occurs within the cool, dense shell behind these shocks. We incorporate a simple molecular chemistry network and classical nucleation theory with a model for the thermodynamic evolution of the post-shock gas to demonstrate the formation of both carbon and forsterite ($\\rm Mg_2SiO_4$) grains. The high densities due to radiative shock compression ($n \\sim 10^{14}$ cm$^{-3}$) result in CO saturation and rapid dust nucleation. Grains grow efficiently to large sizes $\\gtrsim 0.1\\mu$m, in agreement with IR observations of dust-producing novae, and with total dust masses sufficient to explain massive extinction events such as V705 Cas. As in...

  3. Recurrent Novae as a progenitor system of Type Ia Supernovae

    Science.gov (United States)

    Hachisu, Izumi; Kato, Mariko

    2002-11-01

    Theoretical light curves of 8 recurrent novae in outburst are modeled to obtain various physical parameters. Light curve calculation includes reflection effects of the companion star and the accretion disk by the photosphere of the white dwarf (WD). We also include a radiation-induced warping instability of the accretion disk in order to reproduce the second peak of T CrB outbursts. The early visual light curves are well reproduced with an expanded WD photosphere of a thermonuclear runaway model on a very massive WD close to the Chandrasekhar mass limit, i.e., MWD = 1.35 - 1.37 Msolar except for CI Aql. The white dwarf mass of CI Aql is estimated to be MWD = 1.2 +/- 0.05 Msolar. Optically thick winds, which blow from the WDs during the outbursts, play a key role in determining the nova duration and the speed of decline because the wind quickly reduces the envelope mass on the WD. Each envelope mass at the optical maximum is estimated, which indicates an average mass accretion rate on to the WDs during the quiescent phase before the last outburst. Although a large part of the envelope mass is blown in the wind, each WD can retain a substantial part of the envelope mass after hydrogen burning ends. Thus, we have obtained net mass-increasing rates of the WDs. These obtained values strongly indicate that the WDs in the recurrent novae have now grown up to near the Chandrasekhar mass limit and will soon explode as a Type Ia supernova if the WDs consist of carbon and oxygen. We have also clarified the reason why only T CrB shows a secondary maximum.

  4. Recurrent Novae — A Review

    Directory of Open Access Journals (Sweden)

    K. Mukai

    2015-02-01

    Full Text Available In recent years, recurrent nova eruptions are often observed very intensely in wide range of wavelengths from radio to optical to X-rays. Here I present selected highlights from recent multi-wavelength observations. The enigma of T Pyx is at the heart of this paper. While our current understanding of CV and symbiotic star evolution can explain why certain subset of recurrent novae have high accretion rate, that of T Pyx must be greatly elevated compared to the evolutionary mean. At the same time, we have extensive data to be able to estimate how the nova envelope was ejected in T Pyx, and it turns to be a rather complex tale. One suspects that envelope ejection in recurrent and classical novae in general is more complicated than the textbook descriptions. At the end of the review, I will speculate that these two may be connected.

  5. Thermal radio emission from novae & symbiotics with the Square Kilometre Array

    CERN Document Server

    O'Brien, Tim; Chomiuk, Laura; Ribeiro, Valerio; Bode, Michael; Sokoloski, Jennifer; Woudt, Patrick

    2015-01-01

    The thermal radio emission of novae during outburst enables us to derive fundamental quantities such as the ejected mass, kinetic energy, and density profile of the ejecta. Recent observations with newly-upgraded facilities such as the VLA and e-MERLIN are just beginning to reveal the incredibly complex processes of mass ejection in novae (ejections appear to often proceed in multiple phases and over prolonged timescales). Symbiotic stars can also exhibit outbursts, which are sometimes accompanied by the expulsion of material in jets. However, unlike novae, the long-term thermal radio emission of symbiotics originates in the wind of the giant secondary star, which is irradiated by the hot white dwarf. The effect of the white dwarf on the giant's wind is strongly time variable, and the physical mechanism driving these variations remains a mystery (possibilities include accretion instabilities and time-variable nuclear burning on the white dwarf's surface). The exquisite sensitivity of SKA1 will enable us to su...

  6. Hydrodynamic models for novae with ejecta rich in oxygen, neon and magnesium

    Science.gov (United States)

    Starrfield, S.; Sparks, W. M.; Truran, J. W.

    1985-01-01

    The characteristics of a new class of novae are identified and explained. This class consists of those objects that have been observed to eject material rich in oxygen, neon, magnesium, and aluminum at high velocities. We propose that for this class of novae the outburst is occurring not on a carbon-oxygen white dwarf but on an oxygen-neon-magnesium white dwarf which has evolved from a star which had a main sequence mass of approx. 8 solar masses to approx. 12 solar masses. An outburst was simulated by evolving 1.25 solar mass white dwarfs accreting hydrogen rich material at various rates. The effective enrichment of the envelope by ONeMg material from the core is simulated by enhancing oxygen in the accreted layers. The resulting evolutionary sequences can eject the entire accreted envelope plus core material at high velocities. They can also become super-Eddington at maximum bolometric luminosity. The expected frequency of such events (approx. 1/4) is in good agreement with the observed numbers of these novae.

  7. A Far Ultraviolet Spectroscopic Analysis of the Old Nova Q Cygni

    Science.gov (United States)

    Kolobow, Craig; Sion, E. M.

    2011-01-01

    Q Cygni (Nova Cygni 1876) is one of the oldest old novae with a long orbital period of 10.08 hours and spectroscopic peculiarities in the optical including the presence of variable wind outflow revealed by optical P Cygni profiles in the He I lines and Halpha (Kafka et al.2003). There has never been a far UV spectroscopic analysis of this system. Therefore, we have carried out a synthetic spectral analysis of a far ultraviolet IUE archival spectrum of Q Cygni using our optically thick, steady state, accretion disk models and model white dwarf photospheres. We report the results of our spectroscopic analysis and compare the physical parameters we derive with those of other old novae. We gratefully acknowledge the support of this by NSF grant 0807892 to Villanova University.

  8. T Pyxidis: Death by a Thousand Novae

    CERN Document Server

    Patterson, Joseph; Kemp, Jonathan; Monard, Berto; Rea, Robert; Hambsch, Franz-Josef; McCormick, Jennie; Nelson, Peter; Allen, William; Krajci, Thomas; Lowther, Simon; Dvorak, Shawn; Borgman, Jordan; Richards, Thomas; Myers, Gordon; Harlingten, Caisey; Bolt, Greg

    2016-01-01

    We report a 20-year campaign to track the 1.8 hour photometric wave in the recurrent nova T Pyxidis, using the global telescope network of the Center for Backyard Astrophysics. During 1996-2011, that wave was highly stable in amplitude and waveform, resembling the orbital wave commonly seen in supersoft binaries. The period, however, was found to increase on a timescale P/P-dot=3x10^5 years. This suggests a mass transfer rate in quiescence of ~10^-7 M_sol/yr, in substantial agreement with the accretion rate based on the star's luminosity. This is ~2000x greater than is typical for cataclysmic variables of that orbital period. During the post-eruption quiescence (2012-2016), the star continued on its merry but mysterious way - similar luminosity, similar P/P-dot (2.4x10^5 years). The orbital signal became vanishingly weak (300 years of accretion at the pre-outburst rate, but the time between outbursts was only 45 years. Thus the erupting white dwarf seems to have ejected at least 6x more mass than it accreted....

  9. T Pyxidis: death by a thousand novae

    Science.gov (United States)

    Patterson, Joseph; Oksanen, Arto; Kemp, Jonathan; Monard, Berto; Rea, Robert; Hambsch, Franz-Josef; McCormick, Jennie; Nelson, Peter; Allen, William; Krajci, Thomas; Lowther, Simon; Dvorak, Shawn; Borgman, Jordan; Richards, Thomas; Myers, Gordon; Harlingten, Caisey; Bolt, Greg

    2017-04-01

    We report a 20-yr campaign to track the 1.8 h photometric (and orbital) wave in the recurrent nova T Pyxidis. Before and after the 2011 eruption, the period increased on a time-scale P/dot{P} = 3 × 105 yr. This suggests a mass transfer rate in quiescence of ˜10-7 M⊙ yr-1, in substantial agreement with the accretion rate based on the star's luminosity. During the eruption itself, a rapid period increase of 0.0054(7) per cent occurred. This is probably a measure of the mass ejected in the outburst. For a plausible choice of binary parameters, that mass is at least 3 × 10-5 M⊙, and probably more. This represents >300 yr of accretion at the pre-outburst rate, but the time between outbursts was only 45 yr. Thus, the erupting white dwarf (WD) seems to have ejected at least six times more mass than it accreted. If this eruption is typical, the WD must be eroding, rather than growing, in mass. Unless the present series of eruptions is a short-lived episode, the binary dynamics will evaporate the secondary in ˜105 yr. This could be a major channel by which short-period cataclysmic variables are removed from the population.

  10. BK Lyncis: The Oldest Old Nova?... And a Bellwether for Cataclysmic-Variable Evolution

    CERN Document Server

    Patterson, Joseph; Kemp, Jonathan; de Miguel, Enrique; Krajci, Thomas; Foote, Jerry; Hambsch, Franz-Josef; Campbell, Tut; Roberts, George; Cejudo, David; Dvorak, Shawn; Vanmunster, Tonny; Koff, Robert; Skillman, David; Harvey, David; Martin, Brian; Rock, John; Boyd, David; Oksanen, Arto; Morelle, Etienne; Ulowetz, Joseph; Kroes, Anthony; Sabo, Richard; Jensen, Lasse

    2012-01-01

    We summarize the results of a 20-year campaign to study the light curves of BK Lyncis, a nova-like star strangely located below the 2-3 hour orbital period gap in the family of cataclysmic variables. Two apparent "superhumps" dominate the nightly light curves - with periods 4.6% longer, and 3.0% shorter, than P_orb. The first appears to be associated with the star's brighter states (V~14), while the second appears to be present throughout and becomes very dominant in the low state (V~15.7). Starting in the year 2005, the star's light curve became indistinguishable from that of a dwarf nova - in particular, that of the ER UMa subclass. Reviewing all the star's oddities, we speculate: (a) BK Lyn is the remnant of the probable nova on 30 December 101, and (b) it has been fading ever since, but has taken ~2000 years for the accretion rate to drop sufficiently to permit dwarf-nova eruptions. If such behavior is common, it can explain other puzzles of CV evolution. One: why the ER UMa class even exists (because all...

  11. The Radio Light Curve of the Gamma-Ray Nova in V407 CYG: Thermal Emission from the Ionized Symbiotic Envelope, Devoured from Within by the Nova Blast

    Science.gov (United States)

    Chomiuk, Laura; Krauss, Miriam I.; Rupen, Michael P.; Nelson, Thomas; Roy, Nirupam; Sokoloski, Jennifer L.; Mukai, Koji; Munari, Ulisse; Mioduszewski, Amy; Weston, Jeninfer; O'Brien, Tim J.; Eyres, Steward P. S.; Bode, Michael F.

    2012-01-01

    We present multi-frequency radio observations of the 2010 nova event in the symbiotic binary V407 Cygni, obtained with the Karl G. Jansky Very Large Array (VLA) and spanning 1.45 GHz and 17.770 days following discovery. This nova.the first ever detected in gamma rays.shows a radio light curve dominated by the wind of the Mira giant companion, rather than the nova ejecta themselves. The radio luminosity grewas the wind became increasingly ionized by the nova outburst, and faded as the wind was violently heated from within by the nova shock. This study marks the first time that this physical mechanism has been shown to dominate the radio light curve of an astrophysical transient. We do not observe a thermal signature from the nova ejecta or synchrotron emission from the shock, due to the fact that these components were hidden behind the absorbing screen of the Mira wind. We estimate a mass-loss rate for the Mira wind of .Mw approximately equals 10(exp -6) Solar mass yr(exp -1). We also present the only radio detection of V407 Cyg before the 2010 nova, gleaned from unpublished 1993 archival VLA data, which shows that the radio luminosity of the Mira wind varies by a factor of 20 even in quiescence. Although V407 Cyg likely hosts a massive accreting white dwarf, making it a candidate progenitor system for a Type Ia supernova, the dense and radially continuous circumbinary material surrounding V407 Cyg is inconsistent with observational constraints on the environments of most Type Ia supernovae.

  12. Observations of Classical and Recurrent Novae with X-ray Gratings

    CERN Document Server

    Orio, Marina

    2012-01-01

    X-ray grating spectra have opened a new window on the nova physics. High signal-to-noise spectra have been obtained for 12 novae after the outburst in the last 13 years with the Chandra and XMM-Newton gratings. They offer the only way to probe the temperature, effective gravity and chemical composition of the hydrogen burning white dwarf before it turns off. These spectra also allow an analysis of the ejecta, which can be photoionized by the hot white dwarf, but more often seem to undergo collisional ionization. The long observations required for the gratings have revealed semi-regular and irregular variability in X-ray flux and spectra. Large short term variability is especially evident in the first weeks after the ejecta have become transparent to the central supersoft X-ray source. Thanks to Chandra and XMM-Newton, we have discovered violent phenomena in the ejecta, discrete shell ejection, and clumpy emission regions. As expected, we have also unveiled the white dwarf characteristics. The peak white dwarf...

  13. Juvenile Ultracool Dwarfs

    CERN Document Server

    Rice, Emily L; Cruz, Kelle; Barman, Travis; Looper, Dagny; Malo, Lison; Mamajek, Eric E; Metchev, Stanimir; Shkolnik, Evgenya L

    2011-01-01

    Juvenile ultracool dwarfs are late spectral type objects (later than ~M6) with ages between 10 Myr and several 100 Myr. Their age-related properties lie intermediate between very low mass objects in nearby star-forming regions (ages 1-5 Myr) and field stars and brown dwarfs that are members of the disk population (ages 1-5 Gyr). Kinematic associations of nearby young stars with ages from ~10-100 Myr provide sources for juvenile ultracool dwarfs. The lowest mass confirmed members of these groups are late-M dwarfs. Several apparently young L dwarfs and a few T dwarfs are known, but they have not been kinematically associated with any groups. Normalizing the field IMF to the high mass population of these groups suggests that more low mass (mainly late-M and possibly L dwarf) members have yet to be found. The lowest mass members of these groups, along with low mass companions to known young stars, provide benchmark objects with which spectroscopic age indicators for juvenile ultracool dwarfs can be calibrated and...

  14. Dwarf-Galaxy Cosmology

    CERN Document Server

    Schulte-Ladbeck, Regina; Brinks, Elias; Kravtsov, Andrey

    2010-01-01

    Dwarf galaxies provide opportunities for drawing inferences about the processes in the early universe by observing our "cosmological backyard"-the Local Group and its vicinity. This special issue of the open-access journal Advances in Astronomy is a snapshot of the current state of the art of dwarf-galaxy cosmology.

  15. A nova ordem repressiva

    Directory of Open Access Journals (Sweden)

    Paulo Roberto Ceccarelli

    Full Text Available Segundo o autor, a humanidade sempre foi marcada por alguma forma de controle de acordo com o discurso do momento sociohistórico que atravessa: esse texto discute alguns instrumentos de controle e repressão da contemporaneidade. Se, por séculos, foi a religião que ditou as normas sociais, na modernidade, as verdades religiosas foram substituídas por enunciados científicos que sugeriam uma linearidade histórica e propunham uma compreensão determinista do mundo, baseada na capacidade da ciência em dar respostas. As certezas da modernidade foram radicalmente questionadas na pósmodernidade, fazendo surgir outros mecanismos de controle. Para o autor, a necessidade do ser humano de criar representações e dispositivos para suportar e nomear a angústia inerente ao desamparo que lhe é próprio o leva a submeter-se aos mais variados discursos repressivos. O discurso científico atual vem sendo transformado em instrumento ideológico que, com as inúmeras expressões do politicamente correto, traduzem uma busca de normatização e de padronização de comportamentos, gerando uma nova ordem repressiva. No que diz respeito à saúde psíquica, os manuais de diagnóstico, financiados pela indústria farmacêutica, transformam comportamentos, individualidades e diversidades em patologias: as singularidades tornam-se anormalidades. Qual é o compromisso social dos psicólogos nesse debate?

  16. Serotonin (5-HT) 5-HT2A Receptor (5-HT2AR):5-HT2CR Imbalance in Medial Prefrontal Cortex Associates with Motor Impulsivity.

    Science.gov (United States)

    Anastasio, Noelle C; Stutz, Sonja J; Fink, Latham H L; Swinford-Jackson, Sarah E; Sears, Robert M; DiLeone, Ralph J; Rice, Kenner C; Moeller, F Gerard; Cunningham, Kathryn A

    2015-07-15

    A feature of multiple neuropsychiatric disorders is motor impulsivity. Recent studies have implicated serotonin (5-HT) systems in medial prefrontal cortex (mPFC) in mediating individual differences in motor impulsivity, notably the 5-HT2AR receptor (5-HT2AR) and 5-HT2CR. We investigated the hypothesis that differences in the ratio of 5-HT2AR:5-HT2CR protein expression in mPFC would predict the individual level of motor impulsivity and that the engineered loss of the 5-HT2CR would result in high motor impulsivity concomitant with elevated 5-HT2AR expression and pharmacological sensitivity to the selective 5-HT2AR antagonist M100907. High and low impulsive rats were identified in a 1-choice serial reaction time task. Native protein levels of the 5-HT2AR and the 5-HT2CR predicted the intensity of motor impulsivity and the 5-HT2AR:5-HT2CR ratio in mPFC positively correlated with levels of premature responses in individual outbred rats. The possibility that the 5-HT2AR and 5-HT2CR act in concert to control motor impulsivity is supported by the observation that high phenotypic motor impulsivity associated with a diminished mPFC synaptosomal 5-HT2AR:5-HT2CR protein:protein interaction. Knockdown of mPFC 5-HT2CR resulted in increased motor impulsivity and triggered a functional disruption of the local 5-HT2AR:5-HT2CR balance as evidenced by a compensatory upregulation of 5-HT2AR protein expression and a leftward shift in the potency of M100907 to suppress impulsive behavior. We infer that there is an interactive relationship between the mPFC 5-HT2AR and 5-HT2CR, and that a 5-HT2AR:5-HT2CR imbalance may be a functionally relevant mechanism underlying motor impulsivity.

  17. Non-LTE Luminosity and Abundance Diagnostics of Classical Novae in X-rays

    CERN Document Server

    Németh, Péter

    2013-01-01

    Classical novae are significant sources of interstellar material, especially carbon, nitrogen and oxygen. These standard candles are only behind supernovae and $\\gamma$-ray bursts as the third brightest objects in the sky, and the most probable progenitors of type Ia supernovae. After a nova outburst the system enters into the constant bolometric luminosity phase and the nova maintains a stable hydrogen burning in the surface layers of the white dwarf. As the expanding shell around the nova attenuates, progressively deeper and hotter layers become visible. At the end of the constant bolometric luminosity phase, the hottest layers are exposed and novae radiate X-rays. This work uses the static, plane-parallel model atmosphere code TLUSTY to calculate atmospheric structure and SYNSPEC to calculate synthetic X-ray spectra. It was necessary to incorporate atomic data for the highest ionization stages of elements ranging from hydrogen to iron in both programs. Atomic data on energy levels, bound-free, bound-bound ...

  18. Quark-Novae Ia in the Hubble diagram: Implications For Dark Energy

    CERN Document Server

    Ouyed, Rachid; Leahy, Denis; Staff, Jan E; Cassidy, Daniel T

    2013-01-01

    The accelerated expansion of the Universe was proposed through the use of Type-Ia SNe as standard candles. The standardization depends on an empirical correlation between the stretch/color and peak luminosity of the light curves. The use of Type Ia SN as standard candles rests on the assumption that their properties (and this correlation) do not vary with red-shift. We consider the possibility that the majority of Type-Ia SNe are in fact caused by a Quark-Nova detonation in a tight neutron-star-CO-white-dwarf binary system; a Quark-Nova Ia. The spin-down energy injected by the Quark Nova remnant (the quark star) contributes to the post-peak light curve and neatly explains the observed correlation between peak luminosity and light curve shape. We demonstrate that the parameters describing Quark-Novae Ia are NOT constant in red-shift. Simulated Quark-Nova Ia light curves provide a test of the stretch/color correlation by comparing the true distance modulus with that determined using SN light curve fitters. We d...

  19. Swift observations of the 2015 outburst of AG Peg - from slow nova to classical symbiotic outburst

    Science.gov (United States)

    Ramsay, Gavin; Sokoloski, J. L.; Luna, G. J. M.; Nuñez, N. E.

    2016-10-01

    Symbiotic stars often contain white dwarfs with quasi-steady shell burning on their surfaces. However, in most symbiotics, the origin of this burning is unclear. In symbiotic slow novae, however, it is linked to a past thermonuclear runaway. In 2015 June, the symbiotic slow nova AG Peg was seen in only its second optical outburst since 1850. This recent outburst was of much shorter duration and lower amplitude than the earlier eruption, and it contained multiple peaks - like outbursts in classical symbiotic stars such as Z And. We report Swift X-ray and UV observations of AG Peg made between 2015 June and 2016 January. The X-ray flux was markedly variable on a time-scale of days, particularly during four days near optical maximum, when the X-rays became bright and soft. This strong X-ray variability continued for another month, after which the X-rays hardened as the optical flux declined. The UV flux was high throughout the outburst, consistent with quasi-steady shell burning on the white dwarf. Given that accretion discs around white dwarfs with shell burning do not generally produce detectable X-rays (due to Compton-cooling of the boundary layer), the X-rays probably originated via shocks in the ejecta. As the X-ray photoelectric absorption did not vary significantly, the X-ray variability may directly link to the properties of the shocked material. AG Peg's transition from a slow symbiotic nova (which drove the 1850 outburst) to a classical symbiotic star suggests that shell burning in at least some symbiotic stars is residual burning from prior novae.

  20. Nova LMC 1990 no. 1: The first extragalactic neon nova

    Science.gov (United States)

    Sonneborn, George; Shore, Steven N.; Starrfield, Sumner G.

    1990-01-01

    International Ultraviolet Explorer (IUE) observations of nova LMC (Large Magellanic Cloud) 1990 No. 1, the first neon (or ONeMg) nova observed outside the Galaxy are presented. The observations were obtained from 17 Jan. to Mar. 1990, with especially dense coverage during the first 25 days of the outburst. (The neon nova categorization is based on the detection of forbidden Ne 3-4 lines in optical spectra; the ultraviolet neon lines were not detected.) During the first 30 days of the outburst, the radiative losses were dominated by the N 5 delta 1240 and C 4 delta 1550 lines. The maximum ejection velocity was approximately 8000 km/s, based on the blue absorption edge of the C 4 P-Cygni profile. Early in the outburst of Nova LMC 1990 No. 1 the UV luminosity alone was approximately 3 times 10 to the 38th power erg/sec, implying that the bolometric luminosity was well in excess of the Eddington luminosity for a one solar mass object.

  1. Status for CASA NOVA konsortiet

    DEFF Research Database (Denmark)

    Bonke, Sten

    1997-01-01

    The report reviews the development projects and the results hitherto achieved by the design and build organisation CASA NOVA which is one of four consortia within the R&D programme "Process and Product Development in Building", financed by the Ministry of Industry and the Ministry of Housing....

  2. Status for CASA NOVA konsortiet

    DEFF Research Database (Denmark)

    Bonke, Sten

    1997-01-01

    The report reviews the development projects and the results hitherto achieved by the design and build organisation CASA NOVA which is one of four consortia within the R&D programme "Process and Product Development in Building", financed by the Ministry of Industry and the Ministry of Housing....

  3. Novae in gamma-rays

    CERN Document Server

    Hernanz, M

    2013-01-01

    Classical novae produce radioactive nuclei which are emitters of gamma-rays in the MeV range. Some examples are the lines at 478 and 1275 keV (from 7Be and 22Na) and the positron-electron annihilation emission (511 keV line and a continuum below this energy, with a cut-off at 20-30 keV). The analysis of gamma-ray spectra and light curves is a potential unique and powerful tool both to trace the corresponding isotopes and to give insights on the properties of the expanding envelope determining its transparency. Another possible origin of gamma-rays is the acceleration of particles up to very high energies, so that either neutral pions or inverse Compton processes produce gamma-rays of energies larger than 100 MeV. MeV photons during nova explosions have not been detected yet, although several attempts have been made in the last decades; on the other hand, GeV photons from novae have been detected in some particular novae, in symbiotic binaries, where the companion is a red giant with a wind, instead of a main ...

  4. Irradiated brown dwarfs

    CERN Document Server

    Casewell, S L; Lawrie, K A; Maxted, P F L; Dobbie, P D; Napiwotzki, R

    2014-01-01

    We have observed the post common envelope binary WD0137-349 in the near infrared $J$, $H$ and $K$ bands and have determined that the photometry varies on the system period (116 min). The amplitude of the variability increases with increasing wavelength, indicating that the brown dwarf in the system is likely being irradiated by its 16500 K white dwarf companion. The effect of the (primarily) UV irradiation on the brown dwarf atmosphere is unknown, but it is possible that stratospheric hazes are formed. It is also possible that the brown dwarf (an L-T transition object) itself is variable due to patchy cloud cover. Both these scenarios are discussed, and suggestions for further study are made.

  5. Dwarfs in ancient Egypt.

    Science.gov (United States)

    Kozma, Chahira

    2006-02-15

    Ancient Egypt was one of the most advanced and productive civilizations in antiquity, spanning 3000 years before the "Christian" era. Ancient Egyptians built colossal temples and magnificent tombs to honor their gods and religious leaders. Their hieroglyphic language, system of organization, and recording of events give contemporary researchers insights into their daily activities. Based on the record left by their art, the ancient Egyptians documented the presence of dwarfs in almost every facet of life. Due to the hot dry climate and natural and artificial mummification, Egypt is a major source of information on achondroplasia in the old world. The remains of dwarfs are abundant and include complete and partial skeletons. Dwarfs were employed as personal attendants, animal tenders, jewelers, and entertainers. Several high-ranking dwarfs especially from the Old Kingdom (2700-2190 BCE) achieved important status and had lavish burial places close to the pyramids. Their costly tombs in the royal cemeteries and the inscriptions on their statutes indicate their high-ranking position in Egyptian society and their close relation to the king. Some of them were Seneb, Pereniankh, Khnumhotpe, and Djeder. There were at least two dwarf gods, Ptah and Bes. The god Ptah was associated with regeneration and rejuvenation. The god Bes was a protector of sexuality, childbirth, women, and children. He was a favored deity particularly during the Greco-Roman period. His temple was recently excavated in the Baharia oasis in the middle of Egypt. The burial sites and artistic sources provide glimpses of the positions of dwarfs in daily life in ancient Egypt. Dwarfs were accepted in ancient Egypt; their recorded daily activities suggest assimilation into daily life, and their disorder was not shown as a physical handicap. Wisdom writings and moral teachings in ancient Egypt commanded respect for dwarfs and other individuals with disabilities.

  6. Phthalate SHEDS-HT runs

    Data.gov (United States)

    U.S. Environmental Protection Agency — Inputs and outputs for SHEDS-HT runs of DiNP, DEHP, DBP. This dataset is associated with the following publication: Moreau, M., J. Leonard, K. Phillips, J. Campbell,...

  7. Serotonin (5-HT) regulates neurite outgrowth through 5-HT1A and 5-HT7 receptors in cultured hippocampal neurons.

    Science.gov (United States)

    Rojas, Paulina S; Neira, David; Muñoz, Mauricio; Lavandero, Sergio; Fiedler, Jenny L

    2014-08-01

    Serotonin (5-HT) production and expression of 5-HT receptors (5-HTRs) occur early during prenatal development. Recent evidence suggests that, in addition to its classical role as a neurotransmitter, 5-HT regulates neuronal connectivity during mammalian development by modulating cell migration and neuronal cytoarchitecture. Given the variety of 5-HTRs, researchers have had difficulty clarifying the specific role of each receptor subtype in brain development. Signalling mediated by the G-protein-coupled 5-HT1A R and 5-HT7 R, however, has been associated with neuronal plasticity. Thus, we hypothesized that 5-HT promotes neurite outgrowth through 5-HT1A R and 5-HT7 R. The involvement of 5-HT1A R and 5-HT7 R in the morphology of rat hippocampal neurons was evaluated by treating primary cultures at 2 days in vitro with 5-HT and specific antagonists for 5-HT1A R and 5-HT7 R (WAY-100635 and SB269970, respectively). The stimulation of hippocampal neurons with 100 nM 5-HT for 24 hr produced no effect on either the number or the length of primary neurites. Nonetheless, after 5HT7 R was blocked, the addition of 5-HT increased the number of primary neurites, suggesting that 5HT7 R could inhibit neuritogenesis. In contrast, 5-HT induced secondary neurite outgrowth, an effect inhibited by 1 μM WAY-100635 or SB269970. These results suggest that both serotonergic receptors participate in secondary neurite outgrowth. We conclude that 5-HT1A R and 5-HT7 R regulate neuronal morphology in primary hippocampal cultures by promoting secondary neurite outgrowth.

  8. The formation of Cataclysmic Variables: the influence of nova eruptions

    CERN Document Server

    Nelemans, G; Repetto, S; Toonen, S; Phinney, E S

    2015-01-01

    The theoretical and observed populations of pre-cataclysmic variables (pre-CVs) are dominated by systems with low-mass white dwarfs (WDs), while the WD masses in CVs are typically high. In addition, the space density of CVs is found to be significantly lower than theoretical models. We investigate the influence of nova outbursts on the formation and (initial) evolution of CVs. In particular, we calculate the stability of the mass transfer in case all the material accreted on the WD is lost in classical novae, and part of the energy to eject the material comes from a common-envelope like interaction with the companion. In addition, we study the effect of an asymmetry in the mass ejection, that may lead to small eccentricities in the orbit. We find that a common-envelope like ejection significantly decreases the stability of the mass transfer, in particular for low-mass WD. Similarly, the influence of asymmetric mass loss can be important for short-period systems and even more so for low-mass WD, but likely dis...

  9. Pan-chromatic observations of the remarkable nova LMC 2012

    CERN Document Server

    Schwarz, Greg J; Page, Kim L; Osborne, Julian P; Beardmore, Andrew P; Walter, Frederick M; Bode, Michael F; Drake, Jeremy J; Ness, Jan-Uwe; Starrfield, Sumner; Van Rossum, Daniel R; Woodward, Charles E

    2014-01-01

    We present the results of an intensive multiwavelength campaign on nova LMC 2012. This nova evolved very rapidly in all observed wavelengths. The time to fall two magnitudes in the V band was only 2 days. In X-rays the super soft phase began 13$\\pm$5 days after discovery and ended around day 50 after discovery. During the super soft phase, the \\Swift/XRT and \\Chandra\\ spectra were consistent with the underlying white dwarf being very hot, $\\sim$ 1 MK, and luminous, $\\sim$ 10$^{38}$ erg s$^{-1}$. The UV, optical, and near-IR photometry showed a periodic variation after the initial and rapid fading had ended. Timing analysis revealed a consistent 19.24$\\pm$0.03 hr period in all UV, optical, and near-IR bands with amplitudes of $\\sim$ 0.3 magnitudes which we associate with the orbital period of the central binary. No periods were detected in the corresponding X-ray data sets. A moderately high inclination system, $i$ = 60$\\pm$10$^{\\arcdeg}$, was inferred from the early optical emission lines. The {\\it HST}/STIS ...

  10. The orbital period and system parameters of the recurrent nova T Pyx

    CERN Document Server

    Uthas, Helena; Steeghs, Danny

    2010-01-01

    T Pyx is a luminous recurrent nova that accretes at a much higher rate than is expected for its photometrically determined orbital period of about 1.8 hours. We here provide the first spectroscopic confirmation of the orbital period, P =1.829 hours (f=13.118368(11) c/d), based on time-resolved optical spectroscopy obtained at the VLT and the Magellan telescopes. We also derive an upper limit of the velocity semi-amplitude of the white dwarf, K1 = 17.9 +/- 1.6 km/s, and estimate a mass ratio of q = 0.20 +/- 0.03. If the mass of the donor star is estimated using the period-density relation and theoretical main-sequence mass-radius relation for a slightly inflated donor star, we find M2 = 0.14 +/- 0.03 Msun. This implies a mass of the primary white dwarf M1 = 0.7 +/- 0.2 Msun. If the white-dwarf mass is > 1 Msun, as classical nova models imply, the donor mass must be even higher. We therefore rule out the possibility that T Pyx has evolved beyond the period minimum for cataclysmic variables. We find that the sys...

  11. Nova Scotia offshore renewal plan

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2008-10-15

    Increase in global exploration and production have caused a reduction in offshore exploration licences. This paper outlined the government of Nova Scotia's offshore renewal plan. The plan was designed to clarify the role of the government and the Canada-Nova Scotia Offshore Petroleum Board (CNSOPB) and federal government. The plan was comprised of 4 different sections, including (1) geoscience, (2) new policy, (3) regulation, and (4) investment abstraction. Requests for proposals are now being designed to develop a better understanding of the geology of offshore Nova Scotia, including the shelf slope and deep water areas in the vicinity of Sable Island. A code of practice is currently being developed to minimize the impact of resource development on the marine environment while supporting the economic development of smaller oil and gas discoveries. Resource and analysis packages are currently being developed to help investors compute the risks associated with developing offshore sites. It was concluded that early action is required to address challenges and knowledge gaps related to geological data, regulatory efficiency, policy, and marketing strategies. Success of the plan will require the continued cooperation, and support of various governmental agencies. Details of regulatory renewal initiative projects were included. 1 fig.

  12. Composite Accretion Disk and White Dwarf Photosphere Analyses of the FUSE and HST Observations of EY Cygni

    CERN Document Server

    Sion, E M; Urban, J A; Tovmassian, G H; Zharikov, S; Gänsicke, B T; Orio, M

    2004-01-01

    We explore the origin of FUSE and HST STIS far UV spectra of the dwarf nova, EY Cyg, during its quiescence using \\emph{combined} high gravity photosphere and accretion disk models as well as model accretion belts. The best-fitting single temperature white dwarf model to the FUSE plus HST STIS spectrum of EY Cygni has T$_{eff} = 24,000$K, log $g = 9.0$, with an Si abundance of 0.1 x solar and C abundance of 0.2 x solar but the distance is only 301 pc. The best-fitting composite model consists of white dwarf with T$_{eff} = 22,000$K, log $g = 9$, plus an accretion belt with T$_{belt} = 36,000$K covering 27% of the white dwarf surface with V$_{belt} sin i = 2000$ km/s. The accretion belt contributes 63% of the FUV light and the cooler white dwarf latitudes contribute 37%. This fit yields a distance of 351 pc which is within 100 pc of our adopted distance of 450 pc. EY Cyg has very weak C {\\sc iv} emission and very strong N {\\sc v} emission, which is atypical of the majority of dwarf novae in quiescence. We also ...

  13. CONCURRENT FORMATION OF CARBON AND SILICATE DUST IN NOVA V1280 SCO

    Energy Technology Data Exchange (ETDEWEB)

    Sakon, Itsuki; Onaka, Takashi; Usui, Fumihiko [Department of Astronomy, Graduate Schools of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Sako, Shigeyuki; Takahashi, Hidenori; Ohsawa, Ryou [Institute of Astronomy, University of Tokyo, 2-21-1 Ohsawa, Mitaka, Tokyo 181-0015 (Japan); Nozawa, Takaya [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Kimura, Yuki [Institute of Low Temperature Science, Hokkaido University, Sapporo 060-0819 (Japan); Fujiyoshi, Takuya [Subaru Telescope, National Astronomical Observatory of Japan, 650 North A’ohoku Place, Hilo, HI 96720 (United States); Shimonishi, Takashi [Frontier Research Institute for Interdisciplinary Sciences, Tohoku University, Aramaki aza Aoba 6-3, Aoba-ku, Sendai 980-8578 (Japan); Arai, Akira [Koyama Astronomical Observatory, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto, 603-8555 (Japan); Uemura, Makoto [Hiroshima Astrophysical Science Center, Hiroshima University, Kagamiyama 1-3-1, Higashi-Hiroshima 739-8526 (Japan); Nagayama, Takahiro [Department of Physics and Astronomy, Graduate School of Science and Engineering, Kagoshima University, 1-21-35 Korimoto, Kagoshima 890-0065 (Japan); Koo, Bon-Chul [Department of Physics and Astronomy, Seoul National University , 1 Gwanak-ro, Gwanak-gu, Seoul 151-742 (Korea, Republic of); Kozasa, Takashi, E-mail: isakon@astron.s.u-tokyo.ac.jp [Department of Cosmosciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810 (Japan)

    2016-02-01

    We present infrared multi-epoch observations of the dust-forming nova V1280 Sco over ∼2000 days from the outburst. The temporal evolution of the infrared spectral energy distributions at 1272, 1616, and 1947 days can be explained by the emissions produced by amorphous carbon dust of mass (6.6–8.7) × 10{sup −8} M{sub ⊙} with a representative grain size of 0.01 μm and astronomical silicate dust of mass (3.4–4.3) × 10{sup −7} M{sub ⊙} with a representative grain size of 0.3–0.5 μm. Both of these dust species travel farther away from the white dwarf without apparent mass evolution throughout those later epochs. The dust formation scenario around V1280 Sco suggested from our analyses is that the amorphous carbon dust is formed in the nova ejecta followed by the formation of silicate dust either in the expanding nova ejecta or as a result of the interaction between the nova wind and the circumstellar medium.

  14. The nature of premaximum halts of classical nova outbursts: V723 Cas and V463 Sct

    CERN Document Server

    Hachisu, Izumi

    2004-01-01

    We present a new interpretation of long premaximum halts of nova outbursts. For V723 Cas (Nova Cas 1995) and V463 Sct (Nova Sct 2000), we have reproduced light curves, excluding the brightness maxima, starting from the long premaximum halt through the late decay phase of the outbursts using a steady-state optically thick wind model. When the hydrogen-rich envelope of the white dwarf (WD) is massive enough, the star expands to \\sim 100 R_\\sun or over and its surface temperature decreases to below 7000 K. At this supergiant mimicry stage, the changes of the photospheric radius and temperature are both small against the large increase in the envelope mass. These make a saturation in visual magnitude for a long time before it begins to decline. It is the premaximum halts of classical nova outbursts. The visual magnitude during the saturation is close to the bolometric magnitude, which is an upper limit for a given WD mass. Since the WD masses are estimated to be 0.59 M_\\sun for V723 Cas and 1.1 M_\\sun for V463 Sc...

  15. White Dwarf Mass Distribution

    CERN Document Server

    Kepler, S O; Romero, Alejandra Daniela; Ourique, Gustavo; Pelisoli, Ingrid

    2016-01-01

    We present the mass distribution for all S/N > 15 pure DA white dwarfs detected in the Sloan Digital Sky Survey up to Data Release 12, fitted with Koester models for ML2/alpha=0.8, and with Teff > 10 000 K, and for DBs with S/N >10, fitted with ML2/alpha=1.25, for Teff > 16 000 K. These mass distributions are for log g > 6.5 stars, i.e., excluding the Extremely Low Mass white dwarfs. We also present the mass distributions corrected by volume with the 1/Vmax approach, for stars brighter than g=19. Both distributions have a maximum at M=0.624 Msun but very distinct shapes. From the estimated z-distances, we deduce a disk scale height of 300 pc. We also present 10 probable halo white dwarfs, from their galactic U, V, W velocities.

  16. KQ Mon and the nature of the UX Ursa Majoris Nova-like variables

    Science.gov (United States)

    Sion, E. M.; Guinan, E. F.

    1983-01-01

    The UX Ursa Majoris stars form a group of nova-like variables with common photometric and spectroscopic properties. These objects appear to be related to the cataclysmic variables. However, there is no information that they have undergone major outbursts. The present investigation is concerned with a new object, KQ Mon, which has been included in a program of study conducted with the IUE satellite. A description of observations of KQ Mon is presented, and the relationship of this star to other UX UMa stars is examined. Attention is given to the nature of the UX Ursa Majoris stars. It is argued that the accretion rates of the UX UMa stars are higher than, for example, the dwarf novae during quiescence and that the higher accretion rates of the UX UMa stars are responsible for their lack of major outbursts.

  17. Ultraviolet Faint Object Spectrograph Observations of the Hot Post-Nova GQ MUSCAE

    Science.gov (United States)

    Shanley, L.; Gallagher, J. S.; Orio, M.; Ogelman, H.

    1996-05-01

    Low resolution, time-resolved ultraviolet spectra were obtained with the Hubble Space Telescope for the post--nova GQ Muscae on September 2, 1994. We obtained satisfactory data during 3 HST orbits which together cover about 90% of the GQ Mus 85.5 min binary orbital period. The mean spectrum shows a strong, blue continuum which is only slightly flatter than a Rayleigh-Jeans spectra energy distribution. The UV luminosity is LUV ~10(35) erg s(-1) . Moderately strong emission lines from He II, C IV and possibly other high ionization species are present. No significant variability is found as a function of orbital phase and the random variability is <= 10 % throughout the 1300--2100 Angstroms spectral region. The results from these observations are discussed in terms of a cooling white dwarf model for this post--nova.

  18. ELEMENTAL ABUNDANCES IN THE EJECTA OF OLD CLASSICAL NOVAE FROM LATE-EPOCH SPITZER SPECTRA

    Energy Technology Data Exchange (ETDEWEB)

    Helton, L. Andrew; Vacca, William D. [SOFIA Science Center, USRA, NASA Ames Research Center, M.S. N232-11, Moffett Field, CA 94035 (United States); Gehrz, Robert D.; Woodward, Charles E.; Shenoy, Dinesh P. [Minnesota Institute for Astrophysics, School of Physics and Astronomy, 116 Church Street S.E., University of Minnesota, Minneapolis, MN 55455 (United States); Wagner, R. Mark [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Evans, Aneurin [Astrophysics Group, Keele University, Keele, Staffordshire ST5 5BG (United Kingdom); Krautter, Joachim [Landessternwarte-Zentrum fuer Astronomie der Universitaet, Koenigstuhl, D-69117 Heidelberg (Germany); Schwarz, Greg J. [American Astronomical Society, 2000 Florida Avenue, NW, Suite 400, Washington, DC 20009 (United States); Starrfield, Sumner, E-mail: ahelton@sofia.usra.edu [School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287 (United States)

    2012-08-10

    We present Spitzer Space Telescope mid-infrared IRS spectra, supplemented by ground-based optical observations, of the classical novae V1974 Cyg, V382 Vel, and V1494 Aql more than 11, 8, and 4 years after outburst, respectively. The spectra are dominated by forbidden emission from neon and oxygen, though in some cases, there are weak signatures of magnesium, sulfur, and argon. We investigate the geometry and distribution of the late time ejecta by examination of the emission line profiles. Using nebular analysis in the low-density regime, we estimate lower limits on the abundances in these novae. In V1974 Cyg and V382 Vel, our observations confirm the abundance estimates presented by other authors and support the claims that these eruptions occurred on ONe white dwarfs (WDs). We report the first detection of neon emission in V1494 Aql and show that the system most likely contains a CO WD.

  19. Photometric variability of the nova-like object V380 Oph in 1976-2016

    CERN Document Server

    Shugarov, S; Sokolovsky, K; Chochol, D

    2016-01-01

    We combined photographic, photoelectric and CCD observations of the nova-like variable V380 Oph to get a light curve spanning the time range of 40 years. While the typical high-state brightness of V380 Oph was R~14.5, two low-brightness episodes identified in 1979 (B_pg~17.5) and 2015 (R~19) confirm its classification as a VY Scl-type "anti-dwarf nova". The Fourier period analysis of photoelectric and CCD V and B observations obtained in 2002-16 revealed the presence of two periods 0.148167d and 4.287d, that may be associated with negative superhumps and disc precession. We also compared measurements obtained with the iris micro-photometer and flatbed scanner at the same plates and found an agreement within the expected accuracy of photographic photometry.

  20. Axions and White Dwarfs

    CERN Document Server

    Isern, J; Garcia-Berro, E; Salaris, M; Torres, S

    2010-01-01

    White dwarfs are almost completely degenerate objects that cannot obtain energy from the thermonuclear sources and their evolution is just a gravothermal process of cooling. The simplicity of these objects, the fact that the physical inputs necessary to understand them are well identified, although not always well understood, and the impressive observational background about white dwarfs make them the most well studied Galactic population. These characteristics allow to use them as laboratories to test new ideas of physics. In this contribution we discuss the robustness of the method and its application to the axion case.

  1. The Investigation of Nova-like Variable MV Lyr during the 1999–2001 Years

    Indian Academy of Sciences (India)

    N. A. Katysheva; S. Yu. Shugarov; E. P. Pavlenko; P. V. Abolmasov

    2002-03-01

    A peculiar nova-like MV Lyr was investigated. The CCD-observations ofMVLyr were continued in Crimea during the outbursts and quiescent states. Last year its behavior became non-typical for ``anti-dwarf novae”. The length of its first deep minimum was 10 years. A modern state is characterized by very strong outbursts and very often changes of the stages. The periods 0.d128 and 0.d136 were obtained for 1998 and 1999 years accordingly. Possibly, a relation between the photometric period and the brightness exists.

  2. White Dwarfs in Globular Clusters

    CERN Document Server

    Möhler, S

    2008-01-01

    We review empirical and theoretical findings concerning white dwarfs in Galactic globular clusters. Since their detection is a critical issue we describe in detail the various efforts to find white dwarfs in globular clusters. We then outline the advantages of using cluster white dwarfs to investigate the formation and evolution of white dwarfs and concentrate on evolutionary channels that appear to be unique to globular clusters. We also discuss the usefulness of globular cluster white dwarfs to provide independent information on the distances and ages of globular clusters, information that is very important far beyond the immediate field of white dwarf research. Finally, we mention possible future avenues concerning globular cluster white dwarfs, like the study of strange quark matter or plasma neutrinos.

  3. Lodgepole Pine Dwarf Mistletoe

    Science.gov (United States)

    Frank G. Hawksworth; Oscar J. Dooling

    1984-01-01

    Lodgepole pine dwarf mistletoe (Arceuthobium americanum Nutt. ex Engelm.) is a native, parasitic, seed plant that occurs essentially throughout the range of lodgepole pine in North America. It is the most damaging disease agent in lodgepole pine, causing severe growth loss and increased tree mortality. Surveys in the Rocky Mountains show that the parasite is found in...

  4. Predicting a Luminous Red Nova

    Science.gov (United States)

    Van Noord, Daniel; Molnar, Larry; Kinemuchi, Karen; Steenwyk, Steven; Alexander, Cara; Spedden, Chris; Kobulnicky, Henry

    2016-05-01

    Luminous Red Novae (LRN) are rare transient events believed to be caused by the merger of a main sequence contact binary. Since the discovery of the prototype, V838 Mon, only a handful of LRN events have been observed. Tylenda et al. (2011) analyzed the OGLE data preceding the 2008 Novae of V1309 Sco and found that it exhibited a similar light curve to that of a contact binary with one interesting exception, the orbital period of V1309 Sco showed exponential period change going to zero. Unfortunately the system was discovered to be a binary after the merger, preventing any targeted observations to narrow down how the system entered this unusual state. However the extreme period change observed in V1309 Sco gives us a signature to look for in other contact binaries, allowing the discovery of merger candidates for follow up. We will present an analysis of light curves and spectra of KIC 9832227 (NSVS 5597755) that show it is a contact binary system with a negative period derivative that is becoming more extreme with time. These data span more than 15 years and are taken from the NSVS, ASAS, WASP, and Kepler surveys, with ongoing measurements from the Calvin College Observatory and the Apache Point Observatory. The ongoing period change observed in the system is consistent with the exponential model fit from V1309 Sco and the rate of period change has surpassed that of all other measured contact binaries with the exception of V1309 Sco. If the exponential period decay continues the system will likely merge between 2019 and 2022 resulting in a naked eye nova. If this event occurs, this star will present the unprecedented opportunity to study a LRN progenitor and to follow the evolution of the merger.

  5. A transitoriedade: uma nova leitura

    Directory of Open Access Journals (Sweden)

    José Otávio de Vasconcellos Naves

    2008-12-01

    Full Text Available Neste trabalho, o texto de Freud Vergänglichkeit (1916 ganha uma nova perspectiva: é a consciência, transitória, que se ocupa do importante intercâmbio entre o eu e o mundo. Entretanto, ela e a sua transitoriedade adoecem. Na paranóia, ela se perde num futuro aterrador para se reencontrar numa realidade delirante. Na melancolia, a consciência se perde no passado, exaurindo-se na reconstituição de um objeto de desejo impossível de ser considerado como perdido.

  6. The diffusion-induced nova scenario. CK Vul and PB 8 as possible observational counterparts

    CERN Document Server

    Bertolami, Marcelo M Miller; Olano, Carlos; Jimenez, Noelia

    2011-01-01

    We propose a scenario for the formation of DA white dwarfs with very thin helium buffers. For these stars we explore the possible occurrence of diffusion-induced CNO- flashes, during their early cooling stage. In order to obtain very thin helium buffers, we simulate the formation of low mass remnants through an AGB final/late thermal pulse (AFTP/LTP scenario). Then we calculate the consequent white dwarf cooling evolution by means of a consistent treatment of element diffusion and nuclear burning. Based on physically sounding white dwarf models, we find that the range of helium buffer masses for these diffusion-induced novas to occur is significantly smaller than that predicted by the only previous study of this scenario. As a matter of fact, we find that these flashes do occur only in some low-mass (M C>O by mass fractions. Contrary to previous speculations we show that these events are not recurrent and do not change substantially the final H-content of the cool (DA) white dwarf. (Abridged)

  7. On the Progenitors of Galactic Novae

    CERN Document Server

    Darnley, M J; Bode, M F; Hounsell, R A; Williams, R P

    2011-01-01

    Of the approximately 400 known Galactic classical novae, only ten of them, the recurrent novae, have been seen to erupt more than once. At least eight of these recurrents are known to harbor evolved secondary stars, rather than the main sequence secondaries typical in classical novae. In this paper, we propose a new nova classification system, based solely on the evolutionary state of the secondary, and not (like the current schemes) based on the properties of the outbursts. Using archival optical and near-infrared photometric observations of a sample of thirty eight quiescent Galactic novae we show that the evolutionary state of the secondary star in a quiescent system can predicted and several objects are identified for follow-up observations; CI Aql, V2487 Oph, DI Lac and EU Sct.

  8. The white dwarf luminosity function

    Science.gov (United States)

    García-Berro, Enrique; Oswalt, Terry D.

    2016-06-01

    White dwarfs are the final remnants of low- and intermediate-mass stars. Their evolution is essentially a cooling process that lasts for ∼ 10 Gyr. Their observed properties provide information about the history of the Galaxy, its dark matter content and a host of other interesting astrophysical problems. Examples of these include an independent determination of the past history of the local star formation rate, identification of the objects responsible for the reported microlensing events, constraints on the rate of change of the gravitational constant, and upper limits to the mass of weakly interacting massive particles. To carry on these tasks the essential observational tools are the luminosity and mass functions of white dwarfs, whereas the theoretical tools are the evolutionary sequences of white dwarf progenitors, and the corresponding white dwarf cooling sequences. In particular, the observed white dwarf luminosity function is the key manifestation of the white dwarf cooling theory, although other relevant ingredients are needed to compare theory and observations. In this review we summarize the recent attempts to empirically determine the white dwarf luminosity function for the different Galactic populations. We also discuss the biases that may affect its interpretation. Finally, we elaborate on the theoretical ingredients needed to model the white dwarf luminosity function, paying special attention to the remaining uncertainties, and we comment on some applications of the white dwarf cooling theory. Astrophysical problems for which white dwarf stars may provide useful leverage in the near future are also discussed.

  9. M Dwarf Mysteries

    Science.gov (United States)

    Henry, Todd J.; Jao, Wei-Chun; Irwin, Jonathan; Dieterich, Sergio; Finch, Charlie T.; Riedel, Adric R.; Subasavage, John P.; Winters, Jennifer; RECONS Team

    2017-01-01

    During RECONS' 17-year (so far) astrometry/photometry program at the CTIO/SMARTS 0.9m, we have observed thousands of the ubiquitous red dwarfs in the solar neighborhood. During this reconnaissance, a few mysterious characters have emerged ...The Case of the Mercurial Stars: One M dwarf has been fading steadily for more than a decade, at last measure 6% fainter than when it was first observed. Another has grown brighter by 7% over 15 years. Are these brightness changes part of extremely long stellar cycles, or something else entirely?The Case of Identical Stellar Twins that Aren't: Two M dwarfs seem at first to be identical siblings traveling together through the Galaxy. They have virtually identical spectra at optical wavelengths and identical colors throughout the VRIJHK bands. Long-term astrometry indicates that they are, indeed, at the same distance via parallax measurements, and their proper motions match precisely. Yet, one of the twins is FOUR times brighter than the other. Followup work has revealed that the brighter component is a very close spectroscopic double, but no other stars are seen. So, the mystery may be half solved, but why do the close stars remain twice as bright as their widely-separated twin?The Case of the Great Kaboom!: After more than 1000 nights of observing on the reliable 0.9m telescope, with generally routine frames reading out upon the screen, one stellar system comprised of five red dwarfs flared in stunning fashion. Of the two distinct sources, the fainter one (an unresolved double) surpassed the brightness of the brighter one (an unresolved triple), increasing by more than three full magnitudes in the V filter. Which component actually flared? Is this magnificent outburst an unusual event, or in fact typical for this system and other M dwarfs?At the AAS meeting, we hope to probe the cognoscenti who study the Sun's smaller cousins to solve these intriguing M Dwarf Mysteries.This effort has been supported by the NSF through grants

  10. Far Ultraviolet Spectroscopy of Old Novae. II. RR Pic, V533 Her, and DI Lac

    Science.gov (United States)

    Sion, Edward M.; Godon, Patrick; Jones, Liam

    2017-03-01

    The old novae V533 Her (Nova Her 1963), DI Lac (Nova Lac 1910), and RR Pic (Nova Pic 1891) are in (or near) their quiescent stage, following their nova explosions, and continue to accrete at a high rate in the aftermath of their explosions. They exhibit continua that are steeply rising into the FUV, as well as absorption lines and emission lines of uncertain origin. All three have Far Ultraviolet Spectroscopic Explorer (FUSE) spectra that offer not only higher spectral resolution but also wavelength coverage extending down to the Lyman Limit. For DI Lac, we have matched these FUSE spectra with existing archival International Ultraviolet Explorer spectral coverage to broaden the FUV wavelength coverage. We adopted the newly determined interstellar reddening corrections of Selvelli & Gilmozzi. The dereddened FUV spectra have been modeled with our grids of optically thick accretion disks and hot, NLTE white dwarf (WD) photospheres. The results of our modeling analysis indicate that the hot components in RR Pic and V533 Her are likely to be accretion disks with mass accretion rates of 10‑8 M ⊙ yr‑1 and 10‑9 M ⊙ yr‑1 respectively. However, the disk cannot produce the observed absorption lines. For the WD to be the source of the absorption lines in these two systems, it must be very hot, with a radius several times its expected size (because the WD in these systems is massive, it has a smaller radius). For DI Lac, we find the best fit to be a disk with \\dot{M}={10}-10 {M}ȯ {{yr}}-1 with a 30,000 K WD. Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer (FUSE). FUSE was operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985.

  11. The white dwarf luminosity function

    CERN Document Server

    García-Berro, Enrique

    2016-01-01

    White dwarfs are the final remnants of low- and intermediate-mass stars. Their evolution is essentially a cooling process that lasts for $\\sim 10$ Gyr. Their observed properties provide information about the history of the Galaxy, its dark matter content and a host of other interesting astrophysical problems. Examples of these include an independent determination of the past history of the local star formation rate, identification of the objects responsible for the reported microlensing events, constraints on the rate of change of the gravitational constant, and upper limits to the mass of weakly interacting massive particles. To carry on these tasks the essential observational tools are the luminosity and mass functions of white dwarfs, whereas the theoretical tools are the evolutionary sequences of white dwarf progenitors, and the corresponding white dwarf cooling sequences. In particular, the observed white dwarf luminosity function is the key manifestation of the white dwarf cooling theory, although other...

  12. Dwarf Spheroidals in MOND

    CERN Document Server

    Angus, Garry W

    2008-01-01

    We take the line of sight velocity dispersions as functions of radius for 8 Milky Way dwarf spheroidal galaxies and use Jeans analysis to calculate the mass-to-light ratios (M/L) in Modified Newtonian Dynamics (MOND). Using the latest structural parameters, distances and variable velocity anisotropy, we find 6/8 dwarfs have sensible M/L using only the stellar populations. Sextans and Draco, however, have M/L=9.2_{-3.0}^{+5.3} and 43.9_{-19.3}^{+29.0} respectively, which poses a problem. Apart from the need for Sextans' integrated magnitude to be reviewed, we propose tidal effects intrinsic to MOND, testable with numerical simulations, but fully orbit dependant, which are disrupting Draco. The creation of the Magellanic Stream is also re-addressed in MOND, the scenario being the stream is ram pressure stripped from the SMC as it crosses the LMC.

  13. Searching for Brown Dwarf Outflows

    CERN Document Server

    Whelan, E T; Bacciotti, F; Randich, S; Natta, A

    2009-01-01

    As outflow activity in low mass protostars is strongly connected to ac- cretion it is reasonable to expect accreting brown dwarfs to also be driving out- flows. In the last three years we have searched for brown dwarf outflows using high quality optical spectra obtained with UVES on the VLT and the technique of spectro-astrometry. To date five brown dwarf outflows have been discovered. Here the method is discussed and the results to date outlined.

  14. Dwarf Dark Matter Halos

    CERN Document Server

    Colin, Pierre; Valenzuela, O; Gottlöber, S

    2003-01-01

    We use N-body simulations to study properties of dwarf halos with virial masses in the range 10^7-10^9 Msun/h. Unlike recent reported results, we find that the density profiles of relaxed dwarf halos are well fitted by the NFW profile and do not have cores. We estimate the distribution of concentrations for halos in mass range that covers six orders of magnitude from 10^7 Msun/h to 10^13 Msun/h, and find that the data are well reproduced by the model of Bullock et al. (2001). We predict that present-day isolated dwarf halos should have a very large median concentration of ~ 35. For halos with masses that range from 4.6 x 10^9 Msun/h to 10^13 Msun/h we measure the subhalo circular velocity function and find that they are similar when normalized to the circular velocity of the parent halo. We compute the halo mass function and the halo spin parameter distribution and find that the former is very well reproduced by the Sheth and Tormen model while the latter is well fitted by a lognormal distribution with lambda...

  15. The NOvA Technical Design Report

    Energy Technology Data Exchange (ETDEWEB)

    Ayres, D.S.; Drake, G.R.; Goodman, M.C.; Grudzinski, J.J.; Guarino, V.J.; Talaga, R.L.; Zhao, A.; /Argonne; Stamoulis, P.; Stiliaris, E.; Tzanakos, G.; Zois, M.; /Athens U. /Caltech /UCLA /Fermilab /College de France /Harvard U. /Indiana U. /Lebedev Inst. /Michigan State U. /Minnesota U., Duluth /Minnesota U.

    2007-10-08

    Technical Design Report (TDR) describes the preliminary design of the NOvA accelerator upgrades, NOvA detectors, detector halls and detector sites. Compared to the March 2006 and November 2006 NOvA Conceptual Design Reports (CDR), critical value engineering studies have been completed and the alternatives still active in the CDR have been narrowed to achieve a preliminary technical design ready for a Critical Decision 2 review. Many aspects of NOvA described this TDR are complete to a level far beyond a preliminary design. In particular, the access road to the NOvA Far Detector site in Minnesota has an advanced technical design at a level appropriate for a Critical Decision 3a review. Several components of the accelerator upgrade and new neutrino detectors also have advanced technical designs appropriate for a Critical Decision 3a review. Chapter 1 is an Executive Summary with a short description of the NOvA project. Chapter 2 describes how the Fermilab NuMI beam will provide a narrow band beam of neutrinos for NOvA. Chapter 3 gives an updated overview of the scientific basis for the NOvA experiment, focusing on the primary goal to extend the search for {nu}{sub {mu}} {yields} {nu}{sub e} oscillations and measure the sin{sup 2}(2{theta}{sub 13}) parameter. This parameter has not been measured in any previous experiment and NOvA would extend the search by about an order of magnitude beyond the current limit. A secondary goal is to measure the dominant mode oscillation parameters, sin{sup 2}(2{theta}{sub 23}) and {Delta}m{sub 32}{sup 2} to a more precise level than previous experiments. Additional physics goals for NOvA are also discussed. Chapter 4 describes the Scientific Design Criteria which the Fermilab accelerator complex, NOvA detectors and NOvA detector sites must satisfy to meet the physics goals discussed in Chapter 3. Chapter 5 is an overview of the NOvA project. The changes in the design relative to the NOvA CDR are discussed. Chapter 6 summarizes the NOvA

  16. Multiwavelength Photometry and Hubble Space Telescope Spectroscopy of the Old Nova V842 Centaurus

    CERN Document Server

    Sion, Edward M; Mukadam, Anjum; Warner, Brian; Woudt, Patrick; Walter, Frederic; Henden, Arne; Godon, Patrick

    2013-01-01

    We present ground-based optical and near infrared photometric observations and Hubble Space Telescope COS spectroscopic observations of the old nova V842 Cen (Nova Cen 1986). Analysis of the optical light curves reveals a peak at 56.5 +/- 0.3s with an amplitude of 8.9 +/- 4.2 mma, which is consistent with the rotation of a magnetic white dwarf primary in V842 Cen that was detected earlier by Woudt et al., and led to its classification as an intermediate polar.However, our UV lightcurve created from the COS time-tag spectra does not show this periodicity. Our synthetic spectral analysis of an HST COS spectrum rules out a hot white dwarf photosphere as the source of the FUV flux. The best-fitting model to the COS spectrum is a full optically thick accretion disk with no magnetic truncation, a low disk inclination angle, low accretion rate and a distance less than half the published distance that was determined on the basis of interstellar sodium D line strengths.Truncated accretion disks with truncation radii o...

  17. Swift observations of the 2015 outburst of AG Peg -- from slow nova to classical symbiotic outburst

    CERN Document Server

    Ramsay, Gavin; Luna, G J M; Nunez, N E

    2016-01-01

    Symbiotic stars often contain white dwarfs with quasi-steady shell burning on their surfaces. However, in most symbiotics, the origin of this burning is unclear. In symbiotic slow novae, however, it is linked to a past thermonuclear runaway. In June 2015, the symbiotic slow nova AG Peg was seen in only its second optical outburst since 1850. This recent outburst was of much shorter duration and lower amplitude than the earlier eruption, and it contained multiple peaks -- like outbursts in classical symbiotic stars such as Z And. We report Swift X-ray and UV observations of AG Peg made between June 2015 and January 2016. The X-ray flux was markedly variable on a time scale of days, particularly during four days near optical maximum, when the X-rays became bright and soft. This strong X-ray variability continued for another month, after which the X-rays hardened as the optical flux declined. The UV flux was high throughout the outburst, consistent with quasi-steady shell burning on the white dwarf. Given that a...

  18. Multi-mission observations of the old nova GK Per during the 2015 outburst

    CERN Document Server

    Zemko, Polina; Luna, Gerardo Juan Manuel; Mukai, Koji

    2016-01-01

    The remarkable old nova and an intermediate polar (IP) - GK Per was observed with Swift, the Chandra HETG and NuSTAR during its recent dwarf nova (DN) outburst in March - April 2015. Monitoring the outburst, we noticed several processes occurring on different time scales, such as: the slow evolution of the very soft X-ray emission (below 0.6 keV) during the first two weeks of the outburst and the very fast saturation of the X-ray flux above 1 keV. The Swift UVOT lights curves also showed different behaviour, depending on the filter. The broad band X-ray spectra revealed the presence of at least three different emitting sources. The white dwarf (WD) spin was observed even in the very hard X-ray range of NuSTAR, indicating that the modulation is not due to absorption, in contrast to a typical IP. It is also supported by the similarity of the on-pulse and off-pulse X-ray spectra. We propose that the scenario when the inner accretion disk pushed towards the WD by the increased accretion obscures the lower WD pole...

  19. Medium-band photometry of novae

    Energy Technology Data Exchange (ETDEWEB)

    Yao, B.A.; Mo, J.E.

    1975-06-01

    In the early stage of novae, the conventional method of photometric transformation is accepted. When the novae are in a nebular stage, one cannot assign the observed values as U, B, V, whether one reduces them by photometric transformation or not. A quantitative calculation was made by means of spectral datum. It proves that the result of the observation may lead to unexpected differences. Differential extinction also cannot be corrected by the conventional method. Some suggestions for better observation and reduction of novae photometry are given.

  20. Seismology of Rapidly Rotating Accreting White Dwarfs

    CERN Document Server

    Townsley, Dean M; Bildsten, Lars

    2016-01-01

    A number of White Dwarfs (WDs) in cataclysmic binaries have shown brightness variations consistent with non-radial oscillations as observed in isolated WDs. A few objects have been well-characterized with photometric campaigns in the hopes of gleaning information about the mass, spin, and possibly internal structural characteristics. The novel aspect of this work is the possiblity to measure or constrain the interior structure and spin rate of WDs which have spent gigayears accreting material from their companion, undergoing thousands of nova outbursts in the process. In addition, variations in the surface temperature affect the site of mode driving, and provide unique and challenging tests for mode driving theories previously applied to isolated WD's. Having undergone long-term accretion, these WDs are expected to have been spun up. Spin periods in the range 60-100 seconds have been measured by other means for two objects, GW Lib and V455 And. Compared to typical mode frequencies, the spin frequency may be s...

  1. Quark-Novae Ia in the Hubble diagram: implications for dark energy

    Science.gov (United States)

    Ouyed, Rachid; Koning, Nico; Leahy, Denis; Staff, Jan E.; Cassidy, Daniel T.

    2014-05-01

    The accelerated expansion of the Universe was proposed through the use of Type-Ia supernovae (SNe) as standard candles. The standardization depends on an empirical correlation between the stretch/color and peak luminosity of the light curves. The use of Type-Ia SNe as standard candles rests on the assumption that their properties (and this correlation) do not vary with redshift. We consider the possibility that the majority of Type-Ia SNe are in fact caused by a Quark-Nova detonation in a tight neutron-star-CO-white-dwarf binary system, which forms a Quark-Nova Ia (QN-Ia). The spin-down energy injected by the Quark-Nova remnant (the quark star) contributes to the post-peak light curve and neatly explains the observed correlation between peak luminosity and light curve shape. We demonstrate that the parameters describing QN-Ia are NOT constant in redshift. Simulated QN-Ia light curves provide a test of the stretch/color correlation by comparing the true distance modulus with that determined using SN light curve fitters. We determine a correction between the true and fitted distance moduli, which when applied to Type-Ia SNe in the Hubble diagram recovers the ΩM = 1 cosmology. We conclude that Type-Ia SNe observations do not necessitate the need for an accelerating expansion of the Universe (if the observed SNe Ia are dominated by QNe Ia) and by association the need for dark energy.

  2. Mid-infrared Spectroscopic Observations of the Dust-forming Classical Nova V2676 Oph

    Science.gov (United States)

    Kawakita, Hideyo; Ootsubo, Takafumi; Arai, Akira; Shinnaka, Yoshiharu; Nagashima, Masayoshi

    2017-02-01

    The dust-forming nova V2676 Oph is unique in that it was the first nova to provide evidence of C2 and CN molecules during its near-maximum phase and evidence of CO molecules during its early decline phase. Observations of this nova have revealed the slow evolution of its lightcurves and have also shown low isotopic ratios of carbon (12C/13C) and nitrogen (14N/15N) in its envelope. These behaviors indicate that the white dwarf (WD) star hosting V2676 Oph is a CO-rich WD rather than an ONe-rich WD (typically larger in mass than the former). We performed mid-infrared spectroscopic and photometric observations of V2676 Oph in 2013 and 2014 (respectively 452 and 782 days after its discovery). No significant [Ne ii] emission at 12.8 μm was detected at either epoch. These provided evidence for a CO-rich WD star hosting V2676 Oph. Both carbon-rich and oxygen-rich grains were detected in addition to an unidentified infrared feature at 11.4 μm originating from polycyclic aromatic hydrocarbon molecules or hydrogenated amorphous carbon grains in the envelope of V2676 Oph. Based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

  3. The Terra Nova oil field development

    Energy Technology Data Exchange (ETDEWEB)

    Bruce, G.C. [Petro-Canada, Inc., St. John' s, NF (Canada)

    2001-07-01

    Before expanding on the development of the Terra Nova oilfield, the author discussed the overall business strategy of Petro-Canada and identified where the Terra Nova and offshore Newfoundland oil have their place within this strategy. The principal basins and oilfields offshore Newfoundland were reviewed, then the emphasis shifted to rest on the Terra Nova development project. A whole range of topics were brought up, including the Floating Production, Storage and Offloading (FPSO) facility, the modules layout, the FPSO located at Bull Arm, and the floating production systems. The physical environment of the Grand Banks was highlighted, and the next few sections were devoted to the Terra Nova FPSO, FPSO and drill centres, the Turret General Arrangement, and Spider buoy including the disconnect/reconnect. The last four sections dealt with the animation of riser movement, the wellhead protection animation, Henry Goodrich, and operations readiness.

  4. Axion cooling of white dwarfs

    CERN Document Server

    Isern, J; Garcia--Berro, E; Salaris, M; Torres, S

    2013-01-01

    The evolution of white dwarfs is a simple gravothermal process. This process can be tested in two ways, through the luminosity function of these stars and through the secular variation of the period of pulsation of those stars that are variable. Here we show how the mass of the axion can be constrained using the white dwarf luminosity function.

  5. The panchromatic spectroscopic evolution of the classical CO nova V339 Delphini (Nova Del 2013) until X-ray turnoff

    Science.gov (United States)

    Shore, S. N.; Mason, E.; Schwarz, G. J.; Teyssier, F. M.; Buil, C.; De Gennaro Aquino, I.; Page, K. L.; Osborne, J. P.; Scaringi, S.; Starrfield, S.; van Winckel, H.; Williams, R. E.; Woodward, C. E.

    2016-05-01

    Context. Classical novae are the product of thermonuclear runaway-initiated explosions occurring on accreting white dwarfs. Aims: V339 Del (Nova Delphinus 2013) was one of the brightest classical novae of the last hundred years. Spectroscopy and photometry are available from γ-rays through infrared at stages that have frequently not been observed well. The complete data set is intended to provide a benchmark for comparison with modeling and for understanding more sparsely monitored historical classical and recurrent novae. This paper is the first in the series of reports on the development of the nova. We report here on the early stages of the outburst, through the X-ray active stage. Methods: A time sequence of optical, flux calibrated high resolution spectra was obtained with the Nordic Optical Telescope (NOT) using FIES simultaneously, or contemporaneously, with the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope during the early stages of the outburst. These were supplemented with Mercator/HERMES optical spectra. High resolution IUE ultraviolet spectra of OS And 1986, taken during the Fe curtain phase, served as a template for the distance determination. We used standard plasma diagnostics (e.g., [O III] and [N II] line ratios, and the Hβ line flux) to constrain electron densities and temperatures of the ejecta. Using Monte Carlo modeling of the ejecta, we derived the structure, filling factor, and mass from comparisons of the optical and ultraviolet line profiles. Results: We derive an extinction of E(B - V) = 0.23 ± 0.05 from the spectral energy distribution, the interstellar absorption, and H I emission lines. The distance, about 4-4.5 kpc, is in agreement with the inferred distance from near infrared interferometry. The maximum velocity was about 2500 km s-1, measured from the UV resonance and optical profiles. The ejecta showed considerable fine structure in all transitions, much of which persisted as emission knots. The

  6. Control of Amygdala Circuits by 5-HT Neurons via 5-HT and Glutamate Cotransmission.

    Science.gov (United States)

    Sengupta, Ayesha; Bocchio, Marco; Bannerman, David M; Sharp, Trevor; Capogna, Marco

    2017-02-15

    The serotonin (5-HT) system and the amygdala are key regulators of emotional behavior. Several lines of evidence suggest that 5-HT transmission in the amygdala is implicated in the susceptibility and drug treatment of mood disorders. Therefore, elucidating the physiological mechanisms through which midbrain 5-HT neurons modulate amygdala circuits could be pivotal in understanding emotional regulation in health and disease. To shed light on these mechanisms, we performed patch-clamp recordings from basal amygdala (BA) neurons in brain slices from mice with channelrhodopsin genetically targeted to 5-HT neurons. Optical stimulation of 5-HT terminals at low frequencies (≤1 Hz) evoked a short-latency excitation of BA interneurons (INs) that was depressed at higher frequencies. Pharmacological analysis revealed that this effect was mediated by glutamate and not 5-HT because it was abolished by ionotropic glutamate receptor antagonists. Optical stimulation of 5-HT terminals at higher frequencies (10-20 Hz) evoked both slow excitation and slow inhibition of INs. These effects were mediated by 5-HT because they were blocked by antagonists of 5-HT2A and 5-HT1A receptors, respectively. These fast glutamate- and slow 5-HT-mediated responses often coexisted in the same neuron. Interestingly, fast-spiking and non-fast-spiking INs displayed differential modulation by glutamate and 5-HT. Furthermore, optical stimulation of 5-HT terminals did not evoke glutamate release onto BA principal neurons, but inhibited these cells directly via activation of 5-HT1A receptors and indirectly via enhanced GABA release. Collectively, these findings suggest that 5-HT neurons exert a frequency-dependent, cell-type-specific control over BA circuitry via 5-HT and glutamate co-release to inhibit the BA output.SIGNIFICANCE STATEMENT The modulation of the amygdala by serotonin (5-HT) is important for emotional regulation and is implicated in the pathogenesis and treatment of affective disorders

  7. 5-HT(1A) receptors and memory.

    Science.gov (United States)

    Meneses, Alfredo; Perez-Garcia, Georgina

    2007-01-01

    The study of 5-hydroxytryptamine (5-HT) systems has benefited from the identification, classification and cloning of multiple 5-HT receptors (5-HT(1)-5-HT(7)). Increasing evidence suggests that 5-HT pathways, reuptake site/transporter complex and 5-HT receptors represent a strategic distribution for learning and memory. A key question still remaining is whether 5-HT markers (e.g., receptors) are directly or indirectly contributing to the physiological and pharmacological basis of memory and its pathogenesis or, rather, if they represent protective or adaptable mechanisms (at least in initial stages). In the current paper, the major aim is to revise recent advances regarding mammalian 5-HT(1A) receptors in light of their physiological, pathophysiological and therapeutic implications in memory. An attempt is made to identify and discuss sources of discrepancies by employing an analytic approach to examine the nature and degree of difficulty of behavioral tasks used, as well as implicating other factors (for example, brain areas, training time or duration, and drug administration) which might offer new insights into the understanding and interpretation of these data. In this context, 8-OH-DPAT deserves special attention since for many years it has been the more selective 5-HT drug and, hence, more frequently used. As 5-HT(1A) receptors are key components of serotonergic signaling, investigation of their memory mechanisms and action sites and the conditions under which they might operate, could yield valuable insights. Moreover, selective drugs with agonists, neutral antagonists or inverse agonist properties for 5-HT(1A) (and 5-HT(7)) receptors may constitute a new therapeutic opportunity for learning and memory disorders.

  8. Abundance analysis of the recurrent nova RS Ophiuchi (2006 outburst)

    CERN Document Server

    Das, Ramkrishna

    2015-01-01

    We present an analysis of elemental abundances of ejecta of the recurrent nova RS Oph using published optical and near-infrared spectra during the 2006 outburst. We use the CLOUDY photoionization code to generate synthetic spectra by varying several parameters, the model generated spectra are then matched with the observed emission line spectra obtained at two epochs. We obtain the best fit model parameters through the $\\chi^{2}$ minimization technique. Our model results fit well with observed optical and near-infrared spectra. The best-fit model parameters are compatible with a hot white dwarf source with T$_{BB}$ of 5.5 - 5.8 $\\times$ 10$^{5}$ K and roughly constant a luminosity of 6 - 8 $\\times$ 10$^{36}$ ergs s$^{-1}$. From the analysis we find the following abundances (by number) of elements with respect to solar: He/H = 1.8 $\\pm$ 0.1, N/H = 12.0 $\\pm$ 1.0, O/H = 1.0 $\\pm$ 0.4, Ne/H = 1.5 $\\pm$ 0.1, Si/H = 0.4 $\\pm$ 0.1, Fe/H = 3.2 $\\pm$ 0.2, Ar/H = 5.1 $\\pm$ 0.1, and Al/H = 1.0 $\\pm$ 0.1, all other elem...

  9. The orbital ephemeris of the classical nova RR Pictoris: presence of a third body?

    CERN Document Server

    Vogt, N; Hambsch, F -J; Retamales, G; Tappert, C; Schmidtobreick, L; Fuentes-Morales, I

    2016-01-01

    The ex-nova RR Pic presents a periodic hump in its light curve which is considered to refer to its orbital period. Analyzing all available epochs of these hump maxima in the literature, and combining them with those from new light curves obtained in 2013 and 2014, we establish an unique cycle count scheme valid during the past 50 years, and derive an ephemeris with the orbital period 0.145025959(15) days. The O - C diagram of this linear ephemeris reveals systematic deviations which could have different causes. One of them could be a light-travel-time effect caused by the presence of a hypothetical third body near the star/brown dwarf mass limit, with an orbital period of the order of 70 years. We also examine the difficulty of the problematic of detecting sub-stellar or planetary companions of close red-dwarf white-dwarf binaries (including cataclysmic variables), and discuss other possible mechanisms responsible for the observed deviations in O - C. For RR Pic, we propose strategies in order to solve this q...

  10. Habitability of planets around red dwarf stars.

    Science.gov (United States)

    Heath, M J; Doyle, L R; Joshi, M M; Haberle, R M

    1999-08-01

    Recent models indicate that relatively moderate climates could exist on Earth-sized planets in synchronous rotation around red dwarf stars. Investigation of the global water cycle, availability of photosynthetically active radiation in red dwarf sunlight, and the biological implications of stellar flares, which can be frequent for red dwarfs, suggests that higher plant habitability of red dwarf planets may be possible.

  11. Magnetized White Dwarfs

    CERN Document Server

    Terrero, D Alvear; Martínez, A Pérez

    2016-01-01

    The purpose of this thesis is to obtain more realistic equations of state to describe the matter forming magnetized white dwarfs, and use them to solve its structure equations. The equations of state are determined by considering the weak magnetic field approximation $Bdwarfs. Also, we consider the energy and pressure correction due to the Coulomb interaction of the electron gas with the ions located in a crystal lattice. Moreover, spherically symmetric Tolman-Oppenheimer-Volkoff structure equations are solved independently for the perpendicular and parallel pressures, confirming the necessity of using axisymmetric structure equations, more adequate to describe the anisotropic system. Therefore, we study the solutions in cylindrical coordinates. In this case, the mass per longitude unit is obtained instead of the total mass of the whit...

  12. Atmospheric deposition 2000. NOVA 2003; Atmosfaerisk deposition 2000. NOVA 2003

    Energy Technology Data Exchange (ETDEWEB)

    Ellermann, T.; Hertel, O.; Hovmand, M.F.; Kemp, K.; Skjoeth, C.A.

    2001-11-01

    This report presents measurements and calculations from the atmospheric part of NOVA 2003 and covers results for 2000. It summarises the main results concerning concentrations and depositions of nitrogen, phosphorus and sulphur compounds related to eutrophication and acidification. Depositions of atmospheric compounds to Danish marine waters as well as land surface are presented. Measurements: In 2000 the monitoring program consisted of eight stations where wet deposition of ammonium, nitrate, phosphate (semi quantitatively) and sulphate were measured using bulk precipitation samplers. Six of the stations had in addition measurements of atmospheric content of A, nitrogen, phosphorus, and sulphur compounds in gas and particulate phase carried out by use of filter pack samplers. Filters were analysed at the National Environmental Research Institute. Furthermore nitrogen dioxide were measured using nitrogen dioxide filter samplers and monitors. Model calculations: The measurements in the monitoring program were supplemented with model calculations of concentrations and depositions of nitrogen and sulphur compounds to Danish land surface, marine waters, fjords and bays using the ACDEP model (Atmospheric Chemistry and Deposition). The model is a so-called trajectory model and simulates the physical and chemical processes in the atmosphere using meteorological and emission data as input. The advantage of combining measurements with model calculations is that the strengths of both methods is obtained. Conclusions concerning: 1) actual concentration levels at the monitoring stations, 2) deposition at the monitoring stations, 3) seasonal variations and 4) long term trends in concentrations and depositions are mainly based on the direct measurements. These are furthermore used to validate the results of the model calculations. Calculations and conclusions concerning: 1) depositions to land surface and to the individual marine water, 2) contributions from different emission

  13. Novas tecnologias, novas competências New Tecnologies, new skills

    Directory of Open Access Journals (Sweden)

    Geneviève Jacquinot Delaunay

    2008-01-01

    Full Text Available O texto aborda a relação dos jovens e adolescentes com tecnologias, nem "novas" nem "velhas", e sim instrumentos para informar e comunicar, divertir, auxiliar nos trabalhos escolares. Apesar de reconhecer a familiaridade dessa geração com o que há de mais avançado em termos de tecnologia, aponta a necessidade de se compreender a complexidade desse novo cenário de aprendizagem, que envolve o aprofundamento de conceitos como interatividade e interação, linguagem numérica, multimídia, internet e hipertexto. Na seqüência, faz uma análise do contato dos jovens com essa diversidade de meios, suas implicações no processo cognitivo e suas conseqüências comunicacionais. Finalmente, reconhece que a aprendizagem é hipercomplexa e que - apesar de todo avanço científico - a máquina, mesmo interativa, não pode proporcionar ao indivíduo o aprendizado que lhe proporciona a interação com outras pessoas.The paper discusses how young people relate to technology, not seen as new or old, but as an instrument to communicate and keep informed, amuse and to help in school projects. Although it is clear that the new generations are much more familiarized with new technology, the focus is on the need to understand the complexity of the new scenario, which requires a deeper understanding of the concepts of interactivity, multimedia, internet and hypertext. It is discussed how young people enter in contact with this diversity of instruments. It is stressed, however, that no matter how complex the computer can be, nothing can replace the role of interacting with other people in the learning process.

  14. [5-HT1A/5-HT7 receptor interplay: Chronic activation of 5-HT7 receptors decreases the functional activity of 5-HT1A receptor and its сontent in the mouse brain].

    Science.gov (United States)

    Kondaurova, E M; Bazovkina, D V; Naumenko, V S

    2017-01-01

    Serotonin receptors 5-HT1A and 5-HT7 are involved in the development of various psychopathologies. Some data indicate that there is an interplay between 5-HT1A 5-HT7 receptors that could be implicated in the regulation of their function. This work analyzed the effects of chronic 5-HT7 activation on the functional activity of 5-HT7 and 5-HT1A receptors, on the corresponding protein levels, and on the expression of genes encoding 5-HT7 and 5-HT1A receptors in the mouse brain. Chronic administration of the 5-HT7 selective agonist LP44 (20.5 nmol, i.c.v., 14 days) produced considerable desensitization of both 5-HT7 and 5-HT1A receptors. In LP44-treated mice, the hypothermic responses mediated by both 5-HT7 and 5-HT1A receptors were attenuated. Moreover, the levels of 5-HT1A receptor protein in the midbrain and the frontal cortex of LP44-treated mice were significantly decreased. However, the brain levels of 5-HT7 receptor protein did not differ between LP44-treated and control mice. Chronic LP44 treatment did not alter the expression of the 5-HT7 and 5-HT1A receptor genes in all investigated brain structure. These data suggest that 5-HT7 receptors participate in the posttranscriptional regulation of the 5-HT1A receptors functioning.

  15. Pan-Chromatic Observations of the Remarkable Nova Large Magellanic Cloud 2012

    Science.gov (United States)

    Schwarz, Greg J.; Shore, Steven N.; Page, Kim L.; Osborne, Julian P.; Beardmore, Andrew P.; Walter, Frederick M.; Bode, Michael F.; Drake, Jeremy J.; Ness, Jan-Uwe; Starrfield, Sumner; Van Rossum, Daniel R.; Woodward, Charles E.

    2015-03-01

    We present the results of an intensive multiwavelength campaign on nova LMC 2012. This nova evolved very rapidly in all observed wavelengths. The time to fall two magnitudes in the V band was only 2 days. In X-rays the super soft phase began 13 ± 5 days after discovery and ended around day 50 after discovery. During the super soft phase, the Swift/XRT and Chandra spectra were consistent with the underlying white dwarf (WD) being very hot, ˜1 MK, and luminous, ˜1038 erg s-1. The UV, optical, and near-IR photometry showed a periodic variation after the initial and rapid fading had ended. Timing analysis revealed a consistent 19.24 ± 0.03 hr period in all UV, optical, and near-IR bands with amplitudes of ˜0.3 mag which we associate with the orbital period of the central binary. No periods were detected in the corresponding X-ray data sets. A moderately high inclination system, i = 60 ± 10{\\circ{}}, was inferred from the early optical emission lines. The HST/STIS UV spectra were highly unusual with only the N v (1240 Å) line present and superposed on a blue continuum. The lack of emission lines and the observed UV and optical continua from four epochs can be fit with a low mass ejection event, ˜10-6 {{M}⊙ }, from a hot and massive WD near the Chandrasekhar limit. The WD, in turn, significantly illuminated its subgiant companion which provided the bulk of the observed UV/optical continuum emission at the later dates. The inferred extreme WD characteristics and low mass ejection event favor nova LMC 2012 being a recurrent nova of the U Sco subclass. Based on observations 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, Incorporated, under NASA contract NAS5-26555.

  16. Pan-chromatic observations of the remarkable nova Large Magellanic Cloud 2012

    Energy Technology Data Exchange (ETDEWEB)

    Schwarz, Greg J. [American Astronomical Society, 2000 Florida Ave., Nw, Suite 300, DC 20009-1231 (United States); Shore, Steven N. [Dipartimento di Fisica “Enrico Fermi,” Universita di Pisa, and INFN-Sezione Pisa, Largo B. Pontecorvo 3, I-56127, Pisa (Italy); Page, Kim L.; Osborne, Julian P.; Beardmore, Andrew P. [X-Ray and Observational Astronomy Group, Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH (United Kingdom); Walter, Frederick M. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794-3800 (United States); Bode, Michael F. [Astrophysics Research Institute, IC2 Liverpool Science Park, 146 Brownlow Hill, L3 5RF (United Kingdom); Drake, Jeremy J. [Smithsonian Astrophysical Observatory, MS-3, 60 Garden Street, Cambridge, MA 02138 (United States); Ness, Jan-Uwe [European Space Astronomy Centre, P.O. Box 78, E-28691 Villanueva de la Canada, Madrid (Spain); Starrfield, Sumner [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States); Rossum, Daniel R. Van [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States); Woodward, Charles E., E-mail: Greg.Schwarz@aas.org [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church S., SE, Minneapolis, MN 55455 (United States)

    2015-03-01

    We present the results of an intensive multiwavelength campaign on nova LMC 2012. This nova evolved very rapidly in all observed wavelengths. The time to fall two magnitudes in the V band was only 2 days. In X-rays the super soft phase began 13 ± 5 days after discovery and ended around day 50 after discovery. During the super soft phase, the Swift/XRT and Chandra spectra were consistent with the underlying white dwarf (WD) being very hot, ∼1 MK, and luminous, ∼10{sup 38} erg s{sup −1}. The UV, optical, and near-IR photometry showed a periodic variation after the initial and rapid fading had ended. Timing analysis revealed a consistent 19.24 ± 0.03 hr period in all UV, optical, and near-IR bands with amplitudes of ∼0.3 mag which we associate with the orbital period of the central binary. No periods were detected in the corresponding X-ray data sets. A moderately high inclination system, i = 60 ± 10{sup ∘}, was inferred from the early optical emission lines. The HST/STIS UV spectra were highly unusual with only the N v (1240 Å) line present and superposed on a blue continuum. The lack of emission lines and the observed UV and optical continua from four epochs can be fit with a low mass ejection event, ∼10{sup −6} M{sub ⊙}, from a hot and massive WD near the Chandrasekhar limit. The WD, in turn, significantly illuminated its subgiant companion which provided the bulk of the observed UV/optical continuum emission at the later dates. The inferred extreme WD characteristics and low mass ejection event favor nova LMC 2012 being a recurrent nova of the U Sco subclass.

  17. Throwing Icebergs at White Dwarfs

    Science.gov (United States)

    Kohler, Susanna

    2017-08-01

    Where do the metals come from that pollute the atmospheres of many white dwarfs? Close-in asteroids may not be the only culprits! A new study shows that distant planet-size and icy objects could share some of the blame.Pollution ProblemsArtists impression of rocky debris lying close around a white dwarf star. [NASA/ESA/STScI/G. Bacon]When a low- to intermediate-mass star reaches the end of its life, its outer layers are blown off, leaving behind its compact core. The strong gravity of this white dwarf causes elements heavier than hydrogen and helium to rapidly sink to its center in a process known as sedimentation, leaving an atmosphere that should be free of metallic elements.Therefore its perhaps surprising that roughly 2550% of all white dwarfs are observed to have atmospheric pollution by heavy elements. The short timescales for sedimentation suggest that these elements were added to the white dwarf recently but how did they get there?Bringing Ice InwardIn the generally accepted theory, pre-existing rocky bodies or an orbiting asteroid belt survive the stars evolution, later accreting onto the final white dwarf. But this scenario doesnt explain a few observations that suggest white dwarfs might be accreting larger planetary-size bodies and bodies with ices and volatile materials.Dynamical evolution of a Neptune-like planet (a) and a Kuiper belt analog object (b) in wide binary star systems. Both have large eccentricity excitations during the white dwarf phase. [Stephan et al. 2017]How might you get large or icy objects which would begin on very wide orbits close enough to a white dwarf to become disrupted and accrete? Led by Alexander Stephan, a team of scientists at UCLA now suggest that the key is for the white dwarf to be in a binary system.Influence of a CompanionIn the authors model, the white-dwarf progenitor is orbited by both a distant stellar companion (a common occurrence) and a number of large potential polluters, which could have masses between that

  18. PROPERTIES OF THE COOLEST DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    SAUMON, DIDIER [Los Alamos National Laboratory; LEGGETT, SANDY K. [NON LANL; FREEDMAN, RICHARD S. [NON LANL; GEBALLE, THOMAS R. [NON LANL; GOLIMOWSKI, DAVID A. [NON LANL; LODIEU, NICOLAS [NON LANL; MARLEY, MARK S. [NON LANL; STEPHENS, DENISE [NON LANL; PINFIELD, DAVID J. [NON LANL; WARREN, STEPHEN J. [NON LANL

    2007-01-18

    Eleven years after the discovery of the first T dwarf, we have a population of ultracool L and T dwarfs that is large enough to show a range of atmospheric properties, as well as model atmospheres advanced enough to study these properties in detail. Since the last Cool Stars meeting, there have been observational developments which aid in these studies. they present recent mid-infrared photometry and spectroscopy from the Spitzer Space Telescope which confirms the prevalence of vertical mixing in the atmospheres of L and T dwarfs. Hence, the 700 K to 2200 K L and t dwarf photspheres require a large number of parameters for successful modeling: effective temperature, gravity, metallicity, grain sedimentation and vertical mixing efficiency. They also describe initial results of a search for ultracool dwarfs in the UKIRT Infrared Deep Sky Survey, and present the latest T dwarf found to date. They conclude with a discussion of the definition of the later-than-T spectral type, the Y dwarf.

  19. Pluto and other dwarf planets

    CERN Document Server

    Saxena, Shalini

    2017-01-01

    The reclassification of Pluto in 2006 not only decreased the number of planets in our solar system by one but also introduced the new category of dwarf planet. Readers will come to understand what separates a dwarf planet from a planet-or for that matter from any of the other bodies found within the solar system. They'll learn about Pluto itself, as well as its fellow dwarf planets, Ceres, Makemake, Haumea, and Eris. Full of recent information, this title is sure to inspire an interest in space science among young readers.

  20. A New Benchmark Brown Dwarf

    CERN Document Server

    Tinney, C G; Forveille, T; Delfosse, Xavier

    1997-01-01

    We present optical spectroscopy of three brown dwarf candidates identified in the first 1% of the DENIS sky survey. Low resolution spectra from 6430--9000A show these objects to have similar spectra to the uncertain brown dwarf candidate GD 165B. High resolution spectroscopy shows that one of the objects -- DBD 1228-1547 -- has a strong EW=2.3+-0.05A absorption line of Li I 6708A, and is therefore a brown dwarf with mass below 0.065 Msol. DBD 1228-1547 can now be the considered proto-type for objects JUST below the hydrogen burning limit.

  1. Uma nova forma de Coffea

    Directory of Open Access Journals (Sweden)

    C. A. Krug

    1950-01-01

    Full Text Available Nos extensos trabalhos de melhoramento do cafeeiro, há 18 anos em realização na Subdivisão de Genética do Instituto Agronômico, tem-se dedicado especial atenção à espécie C. arabica L., pelo fato de todos os nossos cafèzais pertencerem a esta espécie que, sem dúvida, fornece o produto de melhor qualidade. Nas regiões de terras extremamente cansadas, um dos principais fatôres levados em consideração no melhoramento é a rusticidade, caráter êsse, entretanto, encontrado de preferência em outras espécies, tais como o C. canephora e C. Dewevrei, cujos cafés são de má qualidade. A hibridação interespecífica, que poderia reunir em uma só planta caraterísticos de rusticidade e boa qualidade de bebida, tem o inconveniente de dar origem a plantas triplóides, que são estéreis. Daí se deduz que a obtenção artificial de formas que combinassem êsses caraterísticos constitui problema, cuja solução é extremamente demorada. No presente trabalho, apresentam-se os caracteres de uma nova forma de Coffea, encontrada em cafèzal da Fazenda Itaporã, em Terra Roxa, município de Viradouro, que, com algumas ressalvas, oferece a desejada combinação de caracteres. Trata-se, provàvelmente, de um híbrido espontâneo entre C. arabica e C. Dewevrei, com 2n = 44 cromosômios, extremamente rústico e produtivo, cujas sementes fornecem uma bebida que pode ser classificada como boa. Apenas apresenta, como principal defeito, uma auto-esterilidade quase completa. Os seus caraterísticos botânicos são descritos em detalhe. Devido ao seu porte elevado, ramos abundantes e folhas grandes e coriáceas, esse cafeeiro se assemelha ao C. Dewevrei. Os frutos são oval-elípticos, de um vermelho bem escuro quando maduros, e as sementes oblongas, constatan-do-se elevada percentagem do tipo "moca" e "chocha". Quanto à constituição citológica, as pesquisas conduziram à hipótese de este cafeeiro possuir 22 cromosômios de C. arabica e 22 (n

  2. Gamma-ray emission from nova outbursts

    CERN Document Server

    Hernanz, M

    2013-01-01

    Classical novae produce radioactive nuclei which are emitters of gamma-rays in the MeV range. Some examples are the lines at 478 and 1275 keV (from 7Be and 22Na) and the positron-electron annihilation emission, with the 511 keV line and a continuum. Gamma-ray spectra and light curves are potential unique tools to trace the corresponding isotopes and to give insights on the properties of the expanding envelope. Another possible origin of gamma-rays is the acceleration of particles up to very high energies, so that either neutral pions or inverse Compton processes produce gamma-rays of energies larger than 100 MeV. MeV photons during nova explosions have not been detected yet, although several attempts have been made in the last decades; on the other hand, GeV photons from novae have been detected with the Fermi satellite in V407 Cyg, a nova in a symbiotic binary, where the companion is a red giant with a wind, instead of a main sequence star as in the cataclysmic variables hosting classical novae. Two more nov...

  3. Gamma-ray Novae: Rare or Nearby?

    CERN Document Server

    Morris, Paul J; Brown, Anthony M; Chadwick, Paula M

    2016-01-01

    Classical Novae were revealed as a surprise source of gamma-rays in Fermi LAT observations. During the first 8 years since the LAT was launched, 6 novae in total have been detected to > 5 sigma in gamma-rays, in contrast to the 69 discovered optically in the same period. We attempt to resolve this discrepancy by assuming all novae are gamma-ray emitters, and assigning peak one-day fluxes based on a flat distribution of the known emitters to a simulated population. To determine optical parameters, the spatial distribution and magnitudes of bulge and disc novae in M31 are scaled to the Milky Way, which we approximate as a disc with a 20 kpc radius and elliptical bulge with semi major axis 3 kpc and axis ratios 2:1 in the xy plane. We approximate Galactic reddening using a double exponential disc with vertical and radial scale heights of r_d = 5 kpc and z_d = 0.2 kpc, and demonstrate that even such a rudimentary model can easily reproduce the observed fraction of gamma-ray novae, implying that these apparently r...

  4. An Accreting White Dwarf near the Chandrasekhar Limit in the Andromeda Galaxy

    CERN Document Server

    Tang, Sumin; Wolf, William M; Li, K L; Kong, Albert K H; Cao, Yi; Cenko, S Bradley; De Cia, Annalisa; Kasliwal, Mansi M; Kulkarni, Shrinivas R; Laher, Russ; Masci, Frank; Nugent, Peter E; Perley, Daniel A; Prince, Thomas A; Surace, Jason

    2014-01-01

    The iPTF detection of the most recent outburst of the recurrent nova system RX J0045.4+4154 in the Andromeda Galaxy has enabled the unprecedented study of a massive (M>1.3 $M_\\odot$) accreting white dwarf (WD). We detected this nova as part of the near daily iPTF monitoring of M31 to a depth of R$\\approx$21 and triggered optical photometry, spectroscopy and soft X-ray monitoring of the outburst. Peaking at an absolute magnitude of M_R$\\approx$-6.6 mag, and with a decay time of 1 mag per day, it is a faint and very fast novae. It shows optical emission lines of He/N and expansion velocities of 1900 to 2600 km/s 1-4 days after the optical peak. The Swift monitoring of the X-ray evolution revealed a supersoft source (SSS) with $kT_{eff}$ $\\approx$ 90-110 eV that appeared within 5 days after the optical peak, and lasted only 12 days. Most remarkably, this is not the first event from this system, rather it is a recurrent nova with a time between outbursts of approximately 1 year, the shortest known. Recurrent X-ra...

  5. Memory time-course: mRNA 5-HT1A and 5-HT7 receptors.

    Science.gov (United States)

    Perez-Garcia, Georgina; Meneses, Alfredo

    2009-08-24

    In an attempt to clarify conflicting results about serotonin (5-hydroxytryptamine, 5-HT) 5-HT(1A) and 5-HT(7) receptors in memory formation, their mRNA expression was determined by RT-PCR in key brain areas for explicit and implicit memory. The time-course (0-120 h) of autoshaped responses was progressive and mRNA 5-HT(1A) or 5-HT(7) receptors expression monotonically augmented or declined in prefrontal cortex, hippocampus and raphe nuclei, respectively. At 24-48 h acutely 8-OH-DPAT (0.062 mg/kg) administration enhanced memory and attenuated mRNA 5-HT(1A)memory; however both combinations suppressed or up-regulated mRNA expression 5-HT(1A) or 5-HT(7) receptors. In contrast, AS19 (5.0 mg/kg) facilitated memory consolidation, decreased or increased hippocampal 5-HT(7) and 5-HT(1A) receptors expression. Together these data revealed that, when both 5-HT(1A) and 5-HT(7) receptors were stimulated by 8-OHDPAT under memory consolidation, subtle changes emerged, not evident at behavioral level though detectable at genes expression. Notably, high levels of efficient memory were maintained even when serotonergic tone, via either 5-HT(1A) or 5-HT(7) receptor, was down- or up-regulated. Nevertheless, WAY100635 plus SB-269970 impaired memory consolidation and suppressed their expression. Considering that serotonergic changes are prominent in AD patients with an earlier onset of disease the present approach might be useful in the identification of functional changes associated to memory formation, memory deficits and reversing or even preventing these deficits.

  6. Asteroseismology of white dwarf stars

    CERN Document Server

    Córsico, A H

    2014-01-01

    Most of low- and intermediate-mass stars that populate the Universe will end their lives as white dwarf stars. These ancient stellar remnants have encrypted inside a precious record of the evolutionary history of the progenitor stars, providing a wealth of information about the evolution of stars, star formation, and the age of a variety of stellar populations, such as our Galaxy and open and globular clusters. While some information like surface chemical composition, temperature and gravity of white dwarfs can be inferred from spectroscopy, the internal structure of these compact stars can be unveiled only by means of asteroseismology, an approach based on the comparison between the observed pulsation periods of variable stars and the periods of appropriate theoretical models. In this communication, we first briefly describe the physical properties of white dwarf stars and the various families of pulsating white dwarfs known up to the present day, and then we present two recent analysis carried out by the La...

  7. NOVA laser facility for inertial confinement fusion

    Energy Technology Data Exchange (ETDEWEB)

    Simmons, W.W.

    1983-11-30

    The NOVA laser consists of ten beams, capable of concentrating 100 to 150 kJ of energy (in 3 ns) and 100 to 150 TW of power (in 100 ps) on experimental targets by 1985. NOVA will also be capable of frequency converting the fundamental laser wavelength (1.05 ..mu..m) to its second (0.525 ..mu..m) or third (0.35 ..mu..m) harmonic. This additional capability (80 to 120 kJ at 0.525 ..mu..m, 40 to 70 kJ at 0.35 ..mu..m) was approved by the US Department of Energy (DOE) in April 1982. These shorter wavelengths are much more favorable for ICF target physics. Current construction status of the NOVA facility, intended for completion in the autumn of 1984, will be presented.

  8. Enquête de satisfaction Novae

    CERN Multimedia

    2014-01-01

    Novae lance une enquête de satisfaction auprès de ses clients. Vous pouvez accéder au questionnaire au sujet des trois restaurants d’entreprise du CERN en utilisant le lien et les codes ci-dessous. Le délai de réponse est fixé au jeudi 29 mai.   https://survey.mis-trend.ch/NOVAE Voici les codes à introduire (en respectant la casse) pour entrer dans le questionnaire, selon le site : CERN Restaurant n°1 : CERN114 CERN Restaurant n°2 : CERN214 CERN Restaurant n°3 : CERN314   Nous attirons votre attention sur le fait que tout questionnaire rempli sera validé. Nous vous prions donc de ne pas utiliser ce lien pour tester le questionnaire. Merci d’avance pour votre collaboration. L'équipe Novae

  9. Um novo paradigma para uma nova antropologia

    Directory of Open Access Journals (Sweden)

    Susin, Luiz Carlos

    2007-01-01

    Full Text Available Este artigo recolhe relativas à identidade humana no contexto das pesquisas científicas e das transformações ocorridas nos últimos tempos, especialmente no século XX. A nova fisica, com um novo desenho do universo, uma nova cosmologia, radicaliza, por um lado, as questões em torno do humano, e, por outro lado, abre novas possibilidades. Um novo paradigma, mais holístico, incluindo a dimensão ecológica, ou ao menos com cenários mais adequados, pode ser vislumbrado, embora ainda não descrito, por estarmos numa "era de transição". Na parte que nos toca no universo - a terra - o futuro da vida depende, em grande parte, de decisões éticas que somente o ser humano é convocado a assumir

  10. X-Ray Flashes in Recurrent Novae: M31N 2008-12a and the Implications of the Swift Non-detection

    CERN Document Server

    Kato, Mariko; Henze, Martin; Ness, Jan-Uwe; Osborne, Julian P; Page, Kim L; Darnley, Matthew J; Bode, Michael F; Shafter, Allen W; Hernanz, Margarita; Gehrels, Neil; Kennea, Jamie; Hachisu, Izumi

    2016-01-01

    Models of nova outbursts suggest that an X-ray flash should occur just after hydrogen ignition. However, this X-ray flash has never been observationally confirmed. We present four theoretical light curves of the X-ray flash for two very massive white dwarfs (WDs) of 1.380 and 1.385 M_sun and for two recurrence periods of 0.5 and 1 years. The duration of the X-ray flash is shorter for a more massive WD and for a longer recurrence period. The shortest duration of 14 hours (0.6 days) among the four cases is obtained for the 1.385 M_sun WD with one year recurrence period. In general, a nova explosion is relatively weak for a very short recurrence period, which results in a rather slow evolution toward the optical peak. This slow timescale and the predictability of very short recurrence period novae give us a chance to observe X-ray flashes of recurrent novae. In this context, we report the first attempt, using the Swift observatory, to detect an X-ray flash of the recurrent nova M31N 2008-12a (0.5 or 1 year recur...

  11. Singing and dancing white dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    Mukadam, Anjum S; Szkody, Paula [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States); Gaensicke, Boris T [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom); Nitta, Atsuko, E-mail: anjum@astro.washington.ed [Gemini Observatory, Hilo, HI 96720 (United States)

    2009-06-01

    Accreting white dwarfs have recently been shown to exhibit non-radial pulsations similar to their non-interacting counterparts. This allows us to probe the interior of the accreting white dwarf using seismology, and may be the only way to determine masses for non-eclipsing cataclysmic variables. Improving our understanding of accreting white dwarfs will have implications for models of supernovae Type Ia. Pulsating white dwarfs in cataclysmic variables are also useful in establishing the effects of accretion on pulsations. A search for nonradial pulsations among suitable candidates has led to the discovery of twelve such systems known to date. With the goal of establishing an instability strip (or strips) for these pulsating accretors, we acquired HST ultra-violet time-series spectroscopy of six pulsating white dwarfs in cataclysmic variables in 2007 and 2008. This approach enables us to measure the effective temperature of the white dwarf using the co-added spectrum, and to simultaneously characterize the pulsations. We also intended to constrain the pulsation mode identification by comparing the ultra-violet amplitudes to those from near-simultaneous ground-based photometry. Our preliminary results indicate a broad instability strip in the temperature range of 10500-15400 K.

  12. Nova variedade de Menta arvensis

    Directory of Open Access Journals (Sweden)

    Abelardo Rodrigues Lima

    1952-09-01

    Full Text Available No quarto ano dos trabalhos de seleção com a menta japonêsa, foi encontrado um "seedling", o M. A. 701, que se destacou pela resistência à ferrugem e pela sua rusticidade. Os caracteres botânicos dessa variedade comercial, principalmente hábito vegetativo, coloração das fôlhas e das hastes, a tornam completa' mente distinta da variedade original. Esta distinção se confirma e acentua quando se compara a natureza dos componentes do óleo essencial da menta "Campinas" M. A. 701, descrita no presente trabalho, com a menta japonêsa comum. A maior produtividade da nova variedade comparada com a da menta japonesa comum foi desde logo também constatada pelos primeiros lavradores, a quem foram enviadas pequenas quantidades de rizomas, para plantio experimental. Foram cultivados em 1949-50 cêrca de 12 hectares; cm 1950-51, cêrca de 900 ha, e o prognóstico é que essa variedade tende a substituir totalmente a menta japonêsa anteriormente cultivada em São Paulo, devido ao seu maior valor econômico.A seedling, designated M.A.701, remarkable for its vigor and resistance to rust, was discovered during the fourth year of selection of Japanese mint (Mentha arvensis L. subsp. haplocalix Briquet var. piperascens Holmes or forma piperascens Malinvaud. The botanical characters of the variety derived from this seedling, especially the vegetative habit and colouring of leaves and stems, make it quite different from the original variety. This difference is enhanced, when we compare the nature of the essential oil components of "Campinas" M.A.701, as described in the present paper, with that of the common Japanese mint. The higher yield of the new variety, compared with that of the common Japanese mint, was soon confirmed by the first cultivators, to whom small quantities of rhizomes were sent for experimental planting. About 12 hectars were cultivated em 1949/50 and about 900 hectars in 1950/51. It is expected that the new variety will, on account

  13. Novas cartas portuguesas: uma abordagem feminista

    OpenAIRE

    Jesus, Isabel Henriques de

    2012-01-01

    Publicado em 1972 e imediatamente confiscado pela censura, Novas cartas portuguesas apresentam uma simultaneidade temporal com o surgimento de movimentos feministas alicerçados, em grande medida, nas questões do corpo e da escrita das mulheres. Exploram-se alguns aspectos do livro à luz dos feminismos de segunda vaga que enformaram os anos 60 e 70 do séc. XX, embora realçando o carácter actual e perforrnativo da escrita de Novas Cartas Portuguesas na construção de outros modelos não dicotómic...

  14. Nova in Centaurus - ASASSN-17gk

    Science.gov (United States)

    Waagen, Elizabeth O.

    2017-05-01

    AAVSO Alert Notice 578 announces the discovery of a galactic nova in Centaurus - ASASSN-17gk - by the ASAS-SN team at magnitude 10.9 V on 2017 May 17.28 UT. Spectroscopy indicating that ASASSN-17gk is a galactic nova was obtained by P. Luckas (International Centre for Radio Astronomy Research, Univ. Western Australia) on 2017 May 18.0598 UT (ATel #10399). Finder charts with sequence may be created using the AAVSO Variable Star Plotter (https://www.aavso.org/vsp). Observations should be submitted to the AAVSO International Database. See full Alert Notice for more details.

  15. Radio Observations as a Tool to Investigate Shocks and Asymmetries in Accreting White Dwarf Binaries

    Science.gov (United States)

    Weston, Jennifer Helen Seng; E-Nova Project

    2017-01-01

    In this dissertation, I use radio observations with the Karl G. Jansky Very Large Array (VLA) to reveal that colliding flows within the ejecta from nova explosions can lead to shocks that accelerate particles and produce radio synchrotron emission. In both novae V1723 Aql and V5589 Sgr, radio emission within the first one to two months deviated strongly from the classic thermal model for radio emission from novae. Three years of radio observations of V1723 Aql show that multiple outflows from the system collided to create non-thermal shocks with a brightness temperature of >106 K. After these shocks faded, the radio light curve became roughly consistent with an expanding thermal shell. However, resolved images of V1723 Aql show elongated material that apparently rotates its major axis over the course of 15 months. In the case of nova V5589 Sgr, I show that the early radio emission is dominated by a shock-powered non-thermal flare that produces strong (kTx > 33 keV) X-rays. These findings have important implications for understanding how normal novae generate GeV gamma-rays.Additionally, I present VLA observations of the symbiotic star CH Cyg and two small surveys of symbiotic binaries. Radio observations of CH Cyg tie the ejection of a collimated jet to a change of state in the accretion disk, strengthening the link between bipolar outflows from accreting white dwarfs and other types of accreting compact objects. Next, I use a survey of eleven accretion-driven symbiotic binaries to determine that the radio brightness of a symbiotic system could potentially be used as an indicator of whether it is powered predominantly by shell burning on the surface of the white dwarf or by accretion. This survey also produces the first radio detections of seven of the target systems. In the second survey of seventeen symbiotic binaries, I spatially resolve extended radio emission in several systems for the first time. The results from these surveys provide some support for the

  16. X-Ray Lines from Hot Flows around White Dwarfs. Application to SS Cygni

    CERN Document Server

    Menou, K; Raymond, J; Menou, Kristen; Perna, Rosalba; Raymond, John

    2001-01-01

    Instead of possessing a boundary layer at the interface between a disk and their stellar surface, White Dwarfs (WDs) in quiescent Dwarf Novae (DN) could accrete via an Advection-Dominated Accretion Flow (ADAF), responsible for the X-ray Bremsstrahlung emission observed. Such a hot accretion flow is also expected to produce characteristic thermal line emission. Using SS Cyg as a specific example, we show that knowing a priori the inclination and the WD mass in quiescent DN makes X-ray line diagnostics powerful probes of the flow structure in these systems. Current X-ray instruments can discriminate, from their width, between lines emitted from a flow with a Keplerian rotation rate and those emitted at a substantially sub-Keplerian rate. This could be used to observationally test the property of energy advection, which is at the origin of the partial radial pressure support by the hot gas and the sub-Keplerian rotation rate in an ADAF.

  17. The peculiar nova V1309 Sco/Nova Sco 2008: A candidate twin of V838 Mon

    CERN Document Server

    Mason, Elena; Williams, Robert E; Preston, George; Bensby, Thomas

    2010-01-01

    Nova Scorpii 2008 was the target of our Directory Discretionary Time proposal at VLT+UVES in order to study the evolution, origin and abundances of the heavy-element absorption system recently discovered in 80% of classical novae in outburst. The early decline of Nova Scorpii 2008 was monitored with high resolution echelle spectroscopy at 5 different epochs. The analysis of the absorption and the emission lines show many unusual characteristics. Nova Scorpii 2008 is confirmed to differ from a common Classical Nova as well as a Symbiotic Recurrent Nova, and it shows characteristics which are common to the so called, yet debated, red-novae. The origin of this new nova remains uncertain.

  18. The Accretion Disk and the Boundary Layer of the Symbiotic Recurrent Nova T Corona Borealis

    Science.gov (United States)

    Mukai, Koji; Luna, Gerardo; Nelson, Thomas; Sokoloski, Jennifer L.; Lucy, Adrian; Nuñez, Natalia

    2017-08-01

    T Corona Borealis is one of four known Galactic recurrent symbiotic novae, red giant-white dwarf binaries from which multiple thermonuclear runaway (TNR) events, or nova eruptions, have been observed. TNR requires high pressure at the base of the accreted envelope, and a recurrence time of less than a century almost certainly requires both high white dwarf mass and high accretion rate. The eruptions of T CrB were observed in 1866 and 1946; if the 80 year interval is typical, the next eruption would be expected within the next decade or two. Optical observations show that T CrB has entered a super-active state starting in 2015, similar to that seen in 1938, 8 years before the last eruption. In quiescence, T CrB is a known, bright hard X-ray source that has been detected in the Swift/BAT all-sky survey. Here we present the result of our NuSTAR observation of T CrB in 2015, when it had started to brighten but had not yet reached the peak of the super-active state. We were able to fit the spectrum with an absorbed cooling flow model with reflection, with a reflection amplitude of 1.0. We also present recent Swift and XMM-Newton observations during the peak of the super-active state, when T CrB had faded dramatically in the BAT band. T CrB is found to be much more luminous in the UV, while the X-ray spectrum became complex including a soft, optically thick component. We present our interpretation of the overall variability as due to instability of a large disk, and of the X-rays as due to emission from the boundary layer. In our view, the NuSTAR observation was performed when the boundary layer was optically thin, and the reflection was only from the white dwarf surface that subtended 2π steradian of the sky as seen from the emission region. With these assumptions, we infer the white dwarf in the T CrB system to have a mass of ~1.2 Msun. During the very active state, the boundary layer had turned partially optically thick and produced the soft X-ray component, while

  19. X-ray Flashes in Recurrent Novae: M31N 2008-12a and the Implications of the Swift Nondetection

    Science.gov (United States)

    Kato, Mariko; Saio, Hideyuki; Henze, Martin; Ness, Jan-Uwe; Osborne, Julian P.; Page, Kim L.; Darnley, Matthew J.; Bode, Michael F.; Shafter, Allen W.; Hernanz, Margarita; Gehrels, Neil; Kennea, Jamie; Hachisu, Izumi

    2016-10-01

    Models of nova outbursts suggest that an X-ray flash should occur just after hydrogen ignition. However, this X-ray flash has never been observationally confirmed. We present four theoretical light curves of the X-ray flash for two very massive white dwarfs (WDs) of 1.380 and 1.385 {M}⊙ and for two recurrence periods of 0.5 and 1 yr. The duration of the X-ray flash is shorter for a more massive WD and for a longer recurrence period. The shortest duration of 14 hr (0.6 days) among the four cases is obtained for the 1.385 {M}⊙ WD with a 1 yr recurrence period. In general, a nova explosion is relatively weak for a very short recurrence period, which results in a rather slow evolution toward the optical peak. This slow timescale and the predictability of very short recurrence period novae give us a chance to observe X-ray flashes of recurrent novae. In this context, we report the first attempt, using the Swift observatory, to detect an X-ray flash of the recurrent nova M31N 2008-12a (0.5 or 1 yr recurrence period), which resulted in the nondetection of X-ray emission during the period of 8 days before the optical detection. We discuss the impact of these observations on nova outburst theory. The X-ray flash is one of the last frontiers of nova studies, and its detection is essential for understanding the pre-optical-maximum phase. We encourage further observations.

  20. Stimulation of 5-HT1A, 5-HT1B, 5-HT2A/2C, 5-HT3 and 5-HT4 receptors or 5-HT uptake inhibition: short- and long-term memory.

    Science.gov (United States)

    Meneses, Alfredo

    2007-11-22

    In order to determine whether short- (STM) and long-term memory (LTM) function in serial or parallel manner, serotonin (5-hydroxtryptamine, 5-HT) receptor agonists were tested in autoshaping task. Results show that control-vehicle animals were modestly but significantly mastering the autoshaping task as illustrated by memory scores between STM and LTM. Thus, post-training administration of 8-OHDPAT (agonist for 5-HT(1A/7) receptors) only at 0.250 and 0.500 mg/kg impaired both STM and LTM. CGS12066 (agonist for 5-HT(1B)) produced biphasic affects, at 5.0 mg/kg impaired STM but at 1.0 and 10.0 mg/kg, respectively, improved or impaired LTM. DOI (agonist for 5-HT(2A/2C) receptors) dose-dependently impaired STM and, at 10.0 mg/kg only impaired LTM. Both, STM and LTM were impaired by either mCPP (mainly agonist for 5-HT(2C) receptors) or mesulergine (mainly antagonist for 5-HT(2C) receptors) lower dose. The 5-HT(3) agonist mCPBG at 1.0 impaired STM and its higher dose impaired both STM and LTM. RS67333 (partial agonist for 5-HT(4) receptors), at 5.0 and 10.0 mg/kg facilitated both STM and LTM. The higher dose of fluoxetine (a 5-HT uptake inhibitor) improved both STM and LTM. Using as head-pokes during CS as an indirect measure of food-intake showed that of 30 memory changes, 21 of these were unrelated to the former. While some STM or LTM impairments can be attributed to decrements in food-intake, but not memory changes (either increase or decreases) produced by 8-OHDPAT, CGS12066, RS67333 or fluoxetine. Except for animals treated with DOI, mCPBG or fluoxetine, other groups treated with 5-HT agonists 6 h following autoshaping training showed similar LTM and unmodified CS-head-pokes scores.

  1. White dwarfs, red dwarfs and halo dark matter

    Energy Technology Data Exchange (ETDEWEB)

    GarcIa-Berro, E; Torres, S; Camacho, J [Departament de Fisica Aplicada, Escola Politecnica Superior de Castelldefels, Universitat Politecnica de Catalunya, Av. del Canal Olimpic, s/n, 08860 Castelldefels (Spain); Isern, J, E-mail: garcia@fa.upc.ed [Institut de Ciencies de l' Espai, CSIC, Campus UAB, Facultat de Ciencies, Torre C-5, 08193 Bellaterra (Spain)

    2009-06-01

    The nature of the microlensing events observed by the MACHO team towards the LMC still remains controversial. Low-mass substellar objects and stars with masses larger than approx 1M{sub o-dot} have been ruled out, while stars of approx 0.5 M{sub o-dot} are the most probable candidates. This means that the microlenses should be either red or white dwarfs. Consequently, we assess jointly the relative contributions of both types of stars to the mass budget of the Galactic halo. We use a Monte Carlo code that incorporates up-to-date evolutionary sequences of both red dwarfs and white dwarfs as well as detailed descriptions of both our Galaxy and the LMC and we compare the synthetic populations obtained with our simulator with the results obtained by the MACHO and EROS experiments. We find that the contribution of the red dwarf population is not enough to explain the number of events measured by the MACHO team. Even though, the optical depth obtained in our simulations almost doubles that obtained when taking into account the white dwarf population alone. Finally, we also find that the contribution to the halo dark matter of the entire population under study is smaller than 10%, at the 95% confidence level.

  2. NOVA Making Stuff Season 2

    Energy Technology Data Exchange (ETDEWEB)

    Leombruni, Lisa; Paulsen, Christine Andrews

    2014-12-12

    Over the course of four weeks in fall 2013, 11.7 million Americans tuned in to PBS to follow host David Pogue as he led them in search of engineering and scientific breakthroughs poised to change our world. Levitating trains, quantum computers, robotic bees, and bomb-detecting plants—these were just a few of the cutting-edge innovations brought into the living rooms of families across the country in NOVA’s four-part series, Making Stuff: Faster, Wilder, Colder, and Safer. Each of the four one-hour programs gave viewers a behind-the-scenes look at novel technologies poised to change our world—showing them how basic research and scientific discovery can hold the keys to transforming how we live. Making Stuff Season 2 (MS2) combined true entertainment with educational value, creating a popular and engaging series that brought accessible science into the homes of millions. NOVA’s goal to engage the public with such technological innovation and basic research extended beyond the broadcast series, including a variety of online, educational, and promotional activities: original online science reporting, web-only short-form videos, a new online quiz-game, social media engagement and promotion, an educational outreach “toolkit” for science educators to create their own “makerspaces,” an online community of practice, a series of nationwide Innovation Cafés, educator professional development, a suite of teacher resources, an “Idealab,” participation in national conferences, and specialized station relation and marketing. A summative evaluation of the MS2 project indicates that overall, these activities helped make a significant impact on the viewers, users, and participants that NOVA reached. The final evaluation conducted by Concord Evaluation Group (CEG) confidently concluded that the broadcast, website, and outreach activities were successful at achieving the project’s intended impacts. CEG reported that the MS2 series and website content were

  3. NOVA making stuff: Season 2

    Energy Technology Data Exchange (ETDEWEB)

    Leombruni, Lisa [WGBH Educational Foundation, Boston, MA (United States); Paulsen, Christine Andrews [Concord Evaluation Group, Concord, MA (United States)

    2014-12-12

    Over the course of four weeks in fall 2013, 11.7 million Americans tuned in to PBS to follow host David Pogue as he led them in search of engineering and scientific breakthroughs poised to change our world. Levitating trains, quantum computers, robotic bees, and bomb-detecting plants—these were just a few of the cutting-edge innovations brought into the living rooms of families across the country in NOVA’s four-part series, Making Stuff: Faster, Wilder, Colder, and Safer. Each of the four one-hour programs gave viewers a behind-the-scenes look at novel technologies poised to change our world—showing them how basic research and scientific discovery can hold the keys to transforming how we live. Making Stuff Season 2 (MS2) combined true entertainment with educational value, creating a popular and engaging series that brought accessible science into the homes of millions. NOVA’s goal to engage the public with such technological innovation and basic research extended beyond the broadcast series, including a variety of online, educational, and promotional activities: original online science reporting, web-only short-form videos, a new online quiz-game, social media engagement and promotion, an educational outreach “toolkit” for science educators to create their own “makerspaces,” an online community of practice, a series of nationwide Innovation Cafés, educator professional development, a suite of teacher resources, an “Idealab,” participation in national conferences, and specialized station relation and marketing. A summative evaluation of the MS2 project indicates that overall, these activities helped make a significant impact on the viewers, users, and participants that NOVA reached. The final evaluation conducted by Concord Evaluation Group (CEG) confidently concluded that the broadcast, website, and outreach activities were successful at achieving the project’s intended impacts. CEG reported that the MS2 series and website content were

  4. Recent observation of Nova SMC 2016 with X-ray grating

    Science.gov (United States)

    Orio, M.; Rauch, Thomas; Zemko, Polina; Behar, Ehud

    2017-01-01

    Nova SMC 2016 (see ATel #9621, #9733) was observed again with the Chandra Low Transmission Grating (LETG) coupled with the High Resolution Camera (HRC-S; see ATel #9810 for the previous exposure) on 2017 January 4 for 28160 s. An average count rate of 11.55+-0.02 counts/s was measured (average of both +1 and -1 orders), although the count rate during the exposure had large oscillations, with variations by up to 45%. The spectrum of the source can be approximately fit with a static white dwarf atmospheric model with a higher effective temperature than in November (ATel #9810), about 750,000 K. Deep absorption features of carbon and nitrogen are measure, blue-shifted by about 2100 km/s.

  5. PTF 11kx: a type Ia supernova with a symbiotic nova progenitor.

    Science.gov (United States)

    Dilday, B; Howell, D A; Cenko, S B; Silverman, J M; Nugent, P E; Sullivan, M; Ben-Ami, S; Bildsten, L; Bolte, M; Endl, M; Filippenko, A V; Gnat, O; Horesh, A; Hsiao, E; Kasliwal, M M; Kirkman, D; Maguire, K; Marcy, G W; Moore, K; Pan, Y; Parrent, J T; Podsiadlowski, P; Quimby, R M; Sternberg, A; Suzuki, N; Tytler, D R; Xu, D; Bloom, J S; Gal-Yam, A; Hook, I M; Kulkarni, S R; Law, N M; Ofek, E O; Polishook, D; Poznanski, D

    2012-08-24

    There is a consensus that type Ia supernovae (SNe Ia) arise from the thermonuclear explosion of white dwarf stars that accrete matter from a binary companion. However, direct observation of SN Ia progenitors is lacking, and the precise nature of the binary companion remains uncertain. A temporal series of high-resolution optical spectra of the SN Ia PTF 11kx reveals a complex circumstellar environment that provides an unprecedentedly detailed view of the progenitor system. Multiple shells of circumstellar material are detected, and the SN ejecta are seen to interact with circumstellar material starting 59 days after the explosion. These features are best described by a symbiotic nova progenitor, similar to RS Ophiuchi.

  6. ULF fluctuations at Terra Nova Bay (Antarctica

    Directory of Open Access Journals (Sweden)

    A. Meloni

    2000-06-01

    Full Text Available ULF geomagnetic field measurements in Antarctica are a very important tool for better understanding the dynamics of the Earth’s magnetosphere and its response to the variable solar wind conditions. We review the results obtained in the last few years at the Italian observatory at Terra Nova Bay

  7. Cinema Interativo: novas possibilidades de ambientes imersivos

    Directory of Open Access Journals (Sweden)

    Natália Aly Menezes

    2011-12-01

    Full Text Available O texto “Cinema Interativo: novas possibilidades de ambientes imersivos”, sintetiza a pesquisa  de-senvolvida pela autora, como projeto de Pós-Graduação no curso Tecnologia da Inteligência e Design Digital – PUC-SP. A pesquisa busca reunir uma análise atenciosa diante da entrada da tecnologia di-gital, tecnologia esta que interfere inevitavelmente na linguagem cinematográfica, e não apenas em sua estética. Com a abertura do mundo dos números binários (código das informações computacionais, e a possibilidade de digitalização da imagem, o que era matéria se desmaterializa e infinitas possibilidades criacionais surgem, inclusive, abrindo portas para experimentar o cinema de maneira expandida. No-vas formas de construção narrativa, nova relação espectador-cinema, um novo tempo e espaço, novas formas de significações; tudo pode sofrer alterações. O texto parte de estudos feitos com base em teóri-cos como Peter Weibel, Jeffrey Shaw, Lev Manovich, entre outros.

  8. 5-HT1A and 5-HT7 receptors contribute to lurasidone-induced dopamine efflux.

    Science.gov (United States)

    Huang, Mei; Horiguchi, Masakuni; Felix, Anna R; Meltzer, Herbert Y

    2012-05-09

    Lurasidone is a novel, atypical antipsychotic drug with serotonin [5-hydroxytryptamine (5-HT)]2A, 5-HT7, dopamine (DA) D2 antagonist, and 5-HT1A receptor partial agonist properties. The ability of lurasidone to reverse the effects of subchronic administration phencyclidine, to impair novel object recognition in rats, an animal model of cognitive impairment in schizophrenia, is dependent, in part, on its 5-HT1A agonist and 5-HT7 receptor antagonist properties. We tested whether 5-HT1A partial agonism or 5-HT7 antagonism, or both, contributed to the ability of lurasidone to enhance cortical and hippocampal DA efflux, which may be related to its ability to improve cognition. Here, we report that lurasidone, 0.25 and 0.5, but not 0.1 mg/kg, subcutaneously, significantly increased DA efflux in the prefrontal cortex and hippocampus in a dose-dependent manner. Lurasidone, 0.5 mg/kg, also produced a smaller increase in DA efflux in the nucleus accumbens. Pretreatment with the 5-HT1A receptor antagonist, WAY100635 (0.2 mg/kg, subcutaneously), partially blocked the lurasidone-induced cortical and hippocampal DA efflux. Further, subeffective doses of the 5-HT1A receptor agonist, tandospirone (0.2 mg/kg), or the 5-HT7 antagonist, SB269970 (0.3 mg/kg), potentiated the ability of a subeffective dose of lurasidone (0.1 mg/kg) to increase DA efflux in the prefrontal cortex. These findings suggest that the effects of lurasidone on the prefrontal cortex and hippocampus, DA efflux are dependent, at least partially, on its 5-HT1A agonist and 5-HT7 antagonist properties and may contribute to its efficacy to reverse the effects of subchronic phencyclidine treatment and improve schizophrenia.

  9. Brown dwarfs as close companions to white dwarfs

    Science.gov (United States)

    Stringfellow, Guy S.; Bodenheimer, Peter; Black, David C.

    1990-01-01

    The influence of the radiation flux emitted by a white dwarf primary on the evolution of a closely orbiting brown dwarf (BD) companion is investigated. Full stellar evolutionary calculations are presented for both isolated and thermal bath cases, including effects of large variations in the atmospheric grain opacities. High grain opacities significantly increase the radii of the BDs, but the thermal bath does not. The major influence of the thermal bath is to increase substantially the surface temperature and luminosity of the BD at a given age. These results are compared with the observational properties of the possible BD companion of the white dwarf G29-38. Inclusion of both physical effects, high grain opacities and thermal bath, increases the mass range (0.034-0.063 solar masses) of viable models significantly, yet the final determination of whether the object is indeed a BD requires improvements in the observations of the system's properties.

  10. Multimission observations of the old nova GK Per during the 2015 outburst

    Science.gov (United States)

    Zemko, P.; Orio, M.; Luna, G. J. M.; Mukai, K.; Evans, P. A.; Bianchini, A.

    2017-07-01

    GK Per, a classical nova of 1901, is thought to undergo variable mass accretion on to a magnetized white dwarf (WD) in an intermediate polar system. We organized a multimission observational campaign in the X-ray and ultraviolet energy ranges during its dwarf nova outburst in 2015 March-April. Comparing data from quiescence and near outburst, we have found that the maximum plasma temperature decreased from about 26 to 16.2^{+0.5}_{-0.4} keV. This is consistent with the previously proposed scenario of increase in mass accretion rate while the inner radius of the magnetically disrupted accretion disc shrinks, thereby lowering the shock temperature. A NuSTAR observation also revealed a high-amplitude WD spin modulation of the very hard X-rays with a single-peaked profile, suggesting an obscuration of the lower accretion pole and an extended shock region on the WD surface. The X-ray spectrum of GK Per measured with the Swift X-Ray Telescope varied on time-scales of days and also showed a gradual increase of the soft X-ray flux below 2 keV, accompanied by a decrease of the hard flux above 2 keV. In the Chandra observation with the High Energy Transmission Gratings, we detected prominent emission lines, especially of Ne, Mg and Si, where the ratios of H-like to He-like transition for each element indicate a much lower temperature than the underlying continuum. We suggest that the X-ray emission in the 0.8-2 keV range originates from the magnetospheric boundary.

  11. The NOvA software testing framework

    Science.gov (United States)

    Tamsett, M.; C Group

    2015-12-01

    The NOvA experiment at Fermilab is a long-baseline neutrino experiment designed to study vε appearance in a vμ beam. NOvA has already produced more than one million Monte Carlo and detector generated files amounting to more than 1 PB in size. This data is divided between a number of parallel streams such as far and near detector beam spills, cosmic ray backgrounds, a number of data-driven triggers and over 20 different Monte Carlo configurations. Each of these data streams must be processed through the appropriate steps of the rapidly evolving, multi-tiered, interdependent NOvA software framework. In total there are greater than 12 individual software tiers, each of which performs a different function and can be configured differently depending on the input stream. In order to regularly test and validate that all of these software stages are working correctly NOvA has designed a powerful, modular testing framework that enables detailed validation and benchmarking to be performed in a fast, efficient and accessible way with minimal expert knowledge. The core of this system is a novel series of python modules which wrap, monitor and handle the underlying C++ software framework and then report the results to a slick front-end web-based interface. This interface utilises modern, cross-platform, visualisation libraries to render the test results in a meaningful way. They are fast and flexible, allowing for the easy addition of new tests and datasets. In total upwards of 14 individual streams are regularly tested amounting to over 70 individual software processes, producing over 25 GB of output files. The rigour enforced through this flexible testing framework enables NOvA to rapidly verify configurations, results and software and thus ensure that data is available for physics analysis in a timely and robust manner.

  12. Terra Nova development : challenges and lessons learned

    Energy Technology Data Exchange (ETDEWEB)

    Lever, G. [Petro-Canada, Inc. (Canada)

    2001-07-01

    The major oil and gas fields in Canada's east coast were illustrated for this power point presentation which focused on the development concept of the Terra Nova. Terra Nova is the first floating production system (FPSO) development and only the second offshore oil development on the challenging Grand Banks of Newfoundland. It is also the first offshore facility in Canada to be certified to both offshore petroleum and shipping regulations. In addition, it represents the first fully-automated disconnectable turret, riser and mooring system on an FPSO, and the first to have glory holes for protecting subsea equipment from iceberg damage. The FPSO can withstand an impact with a 100,000 tonne iceberg. The Terra Nova project also represents the first attempt at trenching in stiff hard pan soil conditions which are typical of the Grand Banks. The physical environment design criteria for the Terra Nova in terms of water depth, air temperature, water temperature, icebergs, current, wind and waves were provided along with the functional requirements in terms of oil production, gas compression, total fluids, water injection, produced water, gas injection and water injection. An illustration of the FPSO topsides modules layout was also provided. The alliance-based contracting approach was adopted in 1995 and gave Petro-Canada access to the collective capability of major contractors that were able to face the technical challenges on Terra Nova. Some of the lessons learned from this contracting approach are that a strong central technical integration team should be implemented early and maintained through to project completion and that interfaces must be identified early and managed in a manner according to risk associated with the cost and schedule. tabs., figs.

  13. Interplay between serotonin 5-HT1A and 5-HT7 receptors in depressive disorders.

    Science.gov (United States)

    Naumenko, Vladimir S; Popova, Nina K; Lacivita, Enza; Leopoldo, Marcello; Ponimaskin, Evgeni G

    2014-07-01

    Serotonin (5-hydroxytryptamine or 5-HT) is an important neurotransmitter regulating a wide range of physiological and pathological functions via activation of heterogeneously expressed 5-HT receptors. Besides the important role of 5-HT receptors in the pathogenesis of depressive disorders and in their clinical medications, underlying mechanisms are far from being completely understood. This review focuses on possible cross talk between two serotonin receptors, 5-HT1A and the 5-HT7 . Although these receptors are highly co-expressed in brain regions implicated in depression, and most agonists developed for the 5-HT1A or 5-HT7 receptors have cross-reactivity, their functional interaction has not been yet established. It has been recently shown that 5-HT1A and 5-HT7 receptors form homo- and heterodimers both in vitro and in vivo. From the functional point of view, heterodimerization has been shown to play an important role in regulation of receptor-mediated signaling and internalization, suggesting the implication of heterodimerization in the development and maintenance of depression. Interaction between these receptors is also of clinical interest, because both receptors represent an important pharmacological target for the treatment of depression and anxiety.

  14. Memory formation and memory alterations: 5-HT6 and 5-HT7 receptors, novel alternative.

    Science.gov (United States)

    Meneses, Alfredo

    2014-01-01

    Agonists and antagonists of the 5-hydroxytryptamine (serotonin) receptor6 (5-HT6) or receptor7 (5-HT7) might improve memory and/or reverse amnesia, although the mechanisms involved are poorly understood. Hence, the current work summarizes recent reviews and findings involving these receptors. Evidence indicates that diverse 5-HT6 receptor antagonists produce promnesic and/or antiamnesic effect in conditions, such as memory formation, age-related cognitive impairments and memory deficit in preclinical studies, as well as in diseases such as schizophrenia, Parkinson's, and Alzheimer's disease (AD). Memory, aging, and AD modify 5-HT6 receptors and signaling cascades; likewise, the modulation of 5-HT6 drugs on memory seems to be accompanied with neural changes. Moreover, 5-HT7 receptors are localized in brain areas mediating memory, including the cortex, hippocampus (e.g., Zola-Morgan and Squire, 1993) and raphe nuclei; however, the role of these receptors on memory has yet to be fully explored. Hence, findings and reviews are summarized in this work. Evidence suggests that both 5-HT7 receptor agonists and antagonists might have promnesic and anti-amnesic effects. These effects seem to be dependent on the basal level of performance, i.e., normal or impaired. Available evidence suggests that a potential utility of 5-HT6 and 5-HT7 receptor in mild-to-moderate AD patients and other memory dysfunctions as therapeutic targets.

  15. Expression of mRNAs encoding for 5-HT2C,5-HT3,5-HT6 and 5-HT7 receptor subtypes in rat spinal cord%大鼠脊髓内5-HT2C,5-HT3,5-HT6和5-HT7受体亚型mRNAs的表达

    Institute of Scientific and Technical Information of China (English)

    武胜昔; 王亚云; 刘翔宇; 王文; 李云庆

    2003-01-01

    Objective:To examine the expression of mRNAs encoding for serotonin (5-HT) 5-HT2c, 5-HT3, 5-HT6and 5-HT7 receptor subtypes within different segments of the rat spinal cord. Methods: Reverse transcriptase-polymerasechain reaction (RT-PCR) technique was used. Results: Strong expression of 5-HT2C receptor mRNA was observed inboth dorsal horn (DH) and ventral horn (VH) of the cervical, thoracic, lumbar and sacral segments of the spinal cord.The 5-HT3 receptor mRNA was present at high expression level in the DH and at slightly lower expression level in the Vhof all spinal cord segments. In contrast, the VH generally contained higher expression level of 5-HT6 receptor subtype mR-NA when compared to the DH. Similar to 5-HT3 receptor, the 5-HT7 receptor mRNA was also found at high expressionlevel in the DH. The differences in the expression level among these 5-HT receptor subtypes at the same level of the spinalcord or the same receptor subtype in different segments of the spinal cord were also observed. Conclusion: Four serotoninreceptor subtypes show a distinct expression pattern in the spinal cord. The present results indicate that these 5-HT recep-tor subtypes might have different physiological roles at the spinal level and provide further evidence for 5-HT receptor un-derlying the mechanism of nociception and movement.%目的:观察5-HT2C,5-HT3,5-HT6和5-HT7受体亚型mRNAs在大鼠脊髓不同节段的表达.方法:反转录PCR方法.结果:5-HT2C受体亚型mRNA在颈、胸、腰、骶段脊髓的背角(DH)和前角(VH)均有较强的表达;5-HT3受体mRNA在各节段脊髓DH的表达水平较高,而在VH则较低;与5-HT3受体亚型相反,5-HT6受体亚型mR-NA在脊髓VH的表达水平高于DH;5-HT7受体mRNA在脊髓的表达则与5-HT3受体相似,在各节段的DH均有较高水平的表达.不同的受体亚型在脊髓同一节段以及同一受体亚型在不同脊髓节段的表达水平存在差异.结论:本研究结果表明,上述四种5-HT受体亚

  16. Serotonergic 5-HT7 receptors and cognition.

    Science.gov (United States)

    Gasbarri, Antonella; Pompili, Assunta

    2014-01-01

    The abundant distribution of serotonin (5-HT) in different areas of the central nervous system can explain the involvement of this neurotransmitter in the regulation of several functions, such as sleep, pain, feeding, and sexual and emotional behaviors. Moreover, the serotonergic system is also involved in other more complex roles, such as cognition, including learning and memory processes. Recent studies led to the discovery of various types and subtypes of receptors differentially associated to cognitive mechanisms. 5-HT7 is the most recently discovered receptor for 5-HT; therefore, it is also one of the least well characterized. Studies exist hypothesizing the role of 5-HT7 on the modulation of learning and memory processes and other cognitive functions. Moreover, much attention has been devoted to the possible role of 5-HT7 receptors in psychiatric disorders. Therefore, the aim of this review is to clarify the behavioral role of the recently discovered 5-HT7 type receptor and highlight its involvement in the cognitive functions, with particular attention to the modulation of learning and memory processes, thus providing a basis to obtain new therapeutic agents and strategies for the treatment of cognitive disorders.

  17. Liverpool Telescope Spectrum of TCP J01375892+4951055 - A Dwarf Nova in the Andromeda Constellation

    Science.gov (United States)

    Darnley, M. J.; Williams, S. C.; Bode, M. F.

    2016-10-01

    We obtained an optical spectrum of TCP J01375892+4951055 (see CBAT TOCP) with the FRODOSpec spectrograph (Barnsley et al. 2012) on the 2.0m Liverpool Telescope (Steele et al. 2004) on 2016 October 20.06 UT. The spectrum was taken using the lower resolution mode of FRODOSpec, which gives a wavelength coverage of 3900 to 5700 Å and 5800 to 9400 Å, with a resolution of R ~ 2400.

  18. Influence of tidal effects on the structure of accretion discs in dwarf novae

    Energy Technology Data Exchange (ETDEWEB)

    Kriz, S. (Ceskoslovenska Akademie Ved, Ondrejov. Astronomicky Ustav)

    1982-05-01

    The equations for the structure of steady-state accretion discs are solved taking into account the angular momentum loss via tidal effects. It is demonstrated that the surface density is substantially reduced in comparison with the standard model without tides. If the disc is optically thick the spectrum of radiation emerging from it due to the dissipation of potential energy is nearly the same as in the case of the standard model. The theoretical radius of the outer edge of the disc is also derived and this tidal radius is compared with observations.

  19. Multiple time scales in cataclysmic binaries. The low-field magnetic dwarf nova DO Draconis

    CERN Document Server

    Andronov, I L; Han, W; Kim, Y; Yoon, J -N

    2008-01-01

    We study the variability of the cataclysmic variable DO Dra, on time-scales of between minutes and decades. The characteristic decay time dt/dm=0.902(3) days/mag was estimated from our 3 nights of CCD R observations. The quiescent data show a photometric wave with a cycle about 303(15)d. We analyzed the profile of the composite (or mean) outburst. We discovered however, that a variety of different outburst heights and durations had occurred, contrary to theoretical predictions. With increasing maximum brightness, we find that the decay time also increases; this is in contrast to the model predictions, which indicate that outbursts should have a constant shape. This is interpreted as representing the presence of outburst-to-outburst variability of the magnetospheric radius. A presence of a number of missed weak narrow outbursts is predicted from this statistical relationship. A new type of variability is detected, during 3 subsequent nights in 2007: periodic (during one nightly run) oscillations with rapidly-d...

  20. VizieR Online Data Catalog: New OGLEIII dwarf novae in Galactic disk (Mroz+, 2013)

    Science.gov (United States)

    Mroz, P.; Pietrukowicz, P.; Poleski, R.; Udalski, A.; Soszynski, I.; Szymanski, M. K.; Kubiak, M.; Pietrzynski, G.; Wyrzykowski, L.; Ulaczyk, K.; Kozlowski, S.; Skowron, J.

    2016-05-01

    All data presented in this paper were collected between 2001 and 2009 during the third phase of the Optical Gravitational Lensing Experiment (OGLE-III). The observations were obtained with the 1.3-m Warsaw Telescope located at Las Campanas Observatory, Chile, which is operated by Carnegie Institution for Science. A CCD camera attached to the telescope consisted of eight chips with the total field of view of 35'x35' and the scale of 0.26arcsec/pixel. More (1 data file).

  1. SALT spectroscopic classification of transient Gaia17bur as a likely dwarf nova

    Science.gov (United States)

    Gromadzki, M.; Wyrzykowski, L.; Mroz, P.; Hamanowicz, A.; Kostrzewa-Rutkowska, Z.; Buckley, D. A. H.; Romero-Colmenero, E.

    2017-08-01

    The optical transient Gaia17bur (13:44:00.73, -40:28:44.22) was discovered on 2017-07-19 with G=18.8 by Gaia Science Alerts programme. Archival observations of this object by the Gaia mission shows brightness variations around G=20.

  2. Determination of the basic parameters of the dwarf nova EY Cygni

    CERN Document Server

    Echevarria, J; Costero, R; Zharikov, S

    2006-01-01

    High-dispersion spectroscopy of EY Cyg obtained from data spanning twelve years show, for the first time, the radial velocity curves from both emission and absorption line systems, yielding semi-amplitudes K_{em}=24+/- 4 km s^-1 and K_{abs}=54+/- 2 km s^-1. The orbital period of this system is found to be 0.4593249(1)d. The masses of the stars, their mass ratio and their separation are found to be M_1 sin^3 i = 0.015+/-0.002 M_sun, M_2 sin^3 i = 0.007+/-0.002 M_sun, q = K_1/K_2 = M_2/M_1 = 0.44+/-0.02 and a sin i = 0.71+/-0.04 R_sun. We also found that the spectral type of the secondary star is around K0,consistent with an early determination by Kraft(1962). From the spectral type of the secondary star and simple comparisons with single main sequence stars, we conclude that the radius of the secondary star is about 30 per cent larger than a main sequence star of the same mass. We also present VRI CCD photometric observations, some of them simultaneous with the spectroscopic runs. The photometric data shows se...

  3. Quark-Novae in Low-Mass X-ray Binaries as a model for G87-7 and for GRB 110328A

    CERN Document Server

    Ouyed, Rachid; Jaikumar, Prashanth

    2011-01-01

    We propose a simple model explaining two outstanding astrophysical problems related to compact objects: (1) that of stars such as G87-7 (alias EG 50) that constitute a class of relatively low-mass white dwarfs which nevertheless fall away from the C/O composition and (2) that of GRB 110328A/Swift J164449.3+57345 which showed spectacularly long-lived strong X-ray flaring, posing a challenge to standard GRB models. We argue that both these observations may have an explanation within the unified framework of a Quark-Nova occurring in a low-mass X-ray binary (neutron star-white dwarf). For LMXBs where the binary separation is sufficiently tight, ejecta from the Neutron Star triggers nuclear burning in the white dwarf on impact, leading to alpha-rich and Fe-rich composition compact white dwarfs reminiscent of G87-7. Under slightly different conditions, the white dwarf is ablated and its ashes raining down on the Quark star leads to accretion-driven X-ray luminosity with energetics and duration reminiscent of GRB 1...

  4. The evolution of iron white dwarf stars

    Directory of Open Access Journals (Sweden)

    J. A. Panei

    2001-01-01

    Full Text Available Recent measurements by Hipparcos provide strong observational evidence supporting the existence of white dwarf stars with iron-rich core composition. Here we examine the evolution of iron-rich white dwarfs, for which the cooling is substancially accelerated as compared with the standard carbon-oxigen white dwarfs.

  5. Photometric evolution of the 2016 outburst of recurrent Nova LMC 1968: the first three weeks

    CERN Document Server

    Munari, U; Hambsch, F -J; Frigo, A

    2016-01-01

    Optical (BVRI) photometry of the first three weeks of the 2016 outburst of the recurrent Nova LMC 1968 is presented and discussed. The 2016 I-band light-curve is an exact replica, even in the most minute details, of that for the 2010 eruption. The maximum is inferred to have occurred on 2016 Jan 21.2 at I=11.5 mag, corresponding to an absolute magnitude M(I)=-7.15. A ~1 day plateau is present in all bands about six days past optical maximum, simultaneous with the emergence of super-soft X-ray emission in Swift observations, signalling the widespread ionization of the ejecta. The nova entered a much longer plateau about 9 days past maximum, governed by the brightness of the white dwarf, now directly visible and still nuclearly burning on its surface. An outburst recurrence mean period of ~955 days (2.6 yrs) would fit both the OGLE inter-season gaps and the observed intervals between previous outburts.

  6. Short-period X-ray oscillations in super-soft novae and persistent SSS

    CERN Document Server

    Ness, J -U; Osborne, J P; Kuulkers, E; Henze, M; Piro, A L; Drake, J J; Dobrotka, A; Schwarz, G; Starrfield, S; Kretschmar, P; Hirsch, M; Wilms, J

    2015-01-01

    Transient short-period <100s oscillations have been found in the X-ray light curves of three novae during their SSS phase and in one persistent SSS. We pursue an observational approach to determine possible driving mechanisms and relations to fundamental system parameters such as the white dwarf mass. We performed a systematic search for short-period oscillations in all available XMM-Newton and Chandra X-ray light curves of persistent SSS and novae during their SSS phase. To study time evolution, we divided each light curve into short time segments and computed power spectra. We then constructed dynamic power spectra from which we identified transient periodic signals even when only present for a short time. From all time segments of each system, we computed fractions of time when periodic signals were detected. In addition to the previously known systems with short-period oscillations, RS Oph (35s), KT Eri (35s), V339 Del (54s), and Cal 83 (67s), we found one additional system, LMC 2009a (33s), and also c...

  7. Nova V1425 Aquilae 1995 The Early Appearance of Accretion Processes in An Intermediate Polar Candidate

    CERN Document Server

    Retter, A; Kovo-Kariti, O

    1997-01-01

    Continuous CCD photometry of Nova Aquilae 1995 was performed through the standard B,V,R and I filters during three nights in 1995 and with the I filter during 18 nights in 1996. The power spectrum of the 1996 data reveals three periodicities in the light curve: 0.2558 d, 0.06005 d and 0.079 d, with peak-to-peak amplitudes of about 0.012, 0.014 and 0.007 mag. respectively. The two shorter periods are absent from the power spectrum of the 1995 light curve, while the long one is probably already present in the light curve of that year. We propose that V1425 Aql should be classified as an Intermediate - Polar CV. Accordingly the three periods are interpreted as the orbital period of the underlying binary system, the spin period of the magnetic white dwarf and the beat period between them. Our results suggest that no later than 15 months after the outburst of the nova, accretion processes are taking place in this stellar system. Matter is being transferred from the cool component, most likely through an accretion ...

  8. A nova re-accretion model for J-type carbon stars

    CERN Document Server

    Sengupta, S; Lau, H H B

    2013-01-01

    The J-type carbon (J)-stars constitute 10-15% of the observed carbon stars in both our Galaxy and the Large Magellanic Cloud (LMC). They are characterized by strong 13C absorption bands with low 12C/13C ratios along with other chemical signatures peculiar for typical carbon stars, e.g. a lack of s-process enhancement. Most of the J-stars are dimmer than the N-type carbon stars some of which, by hot-bottom burning, make 13C only in a narrow range of masses. We investigate a binary-star formation channel for J-stars involving re-accretion of carbon-rich nova ejecta on main-sequence companions to low-mass carbon-oxygen white-dwarfs. The subsequent evolution of the companion stars in such systems is studied with a rapid binary evolutionary code to predict chemical signatures of nova pollution in systems which merge into giant single stars. A detailed population synthesis study is performed to estimate the number of these mergers and compare their properties with observed J-stars. Our results predict that such nov...

  9. The slow decline of the Galactic recurrent novae T Pyxidis, IM Normae, and CI Aquilae

    CERN Document Server

    Caleo, Andrea

    2015-01-01

    A distinguishing trait of the three known Galactic recurrent novae with the shortest orbital periods, T Pyx, IM Nor, and CI Aql, is that their optical decline time-scales are significantly longer than those of the other recurrent systems. On the other hand, some estimates of the mass of the ejecta, the velocity of the ejecta, and the duration of the soft X-rays emission of these systems are of the order of those of the other recurrent systems and the fast classical novae. We put forth a tentative explanation of this phenomenon. We propose that in these systems part of the material transferred from the companion during the first few days of the eruption remains within the Roche lobe of the white dwarf, preventing the radiation from ionizing the ejecta of the system and increasing the optical decline time-scale. We explain why this phenomenon is more likely in systems with a high mass transfer rate and a short orbital period. Finally, we present a schematic model that shows that the material transferred from th...

  10. Morphological Mutations of Dwarf Galaxies

    CERN Document Server

    Hensler, Gerhard

    2012-01-01

    Dwarf galaxies (DGs) are extremely challenging objects in extragalactic astrophysics. They are expected to originate as the first units in Cold Dark-Matter cosmology. They are the galaxy type most sensitive to environmental influences and their division into multiple types with various properties have invoked the picture of their variant morphological transformations. Detailed observations reveal characteristics which allow to deduce the evolutionary paths and to witness how the environment has affected the evolution. Here we review peculiarities of general morphological DG types and refer to processes which can deplete gas-rich irregular DGs leading to dwarf ellipticals, while gas replenishment implies an evolutionary cycling. Finally, as the less understood DG types the Milky Way satellite dwarf spheroidal galaxies are discussed in the context of transformation.

  11. The rotation of brown dwarfs

    CERN Document Server

    Scholz, Aleks

    2016-01-01

    One of the characteristic features of low-mass stars is their propensity to shed large amounts of angular momentum throughout their evolution. This distinguishs them from brown dwarfs which remain fast rotators over timescales of gigayears. Brown dwarfs with rotation periods longer than a couple of days have only been found in star forming regions and young clusters. This is a useful constraint on the mass dependency of mechanisms for angular momentum regular in stars. Rotational braking by disks and winds become highly inefficient in the substellar regime. In this short review I discuss the observational evidence for the fast rotation in brown dwarfs, the implications, and the link to the spin-mass relation in planets.

  12. Faint Dwarfs in Nearby Groups

    CERN Document Server

    Speller, Ryan

    2013-01-01

    The number and distribution of dwarf satellite galaxies remain a critical test of cold dark matter-dominated structure formation on small scales. Until recently, observational information about galaxy formation on these scales has been limited mainly to the Local Group. We have searched for faint analogues of Local Group dwarfs around nearby bright galaxies, using a spatial clustering analysis of the photometric catalog of the Sloan Digital Sky Survey (SDSS) Data Release 8. Several other recent searches of SDSS have detected clustered satellite populations down to $\\Delta m_r \\equiv ({m}_{r,\\, {\\rm sat}} -\\, {m}_{r,\\, {\\rm main}}) \\sim 6$-$8$, using photometric redshifts to reduce background contamination. SDSS photometric redshifts are relatively imprecise, however, for faint and nearby galaxies. Instead we use angular size to select potential nearby dwarfs, and consider only the nearest isolated bright galaxies as primaries. As a result, we are able to detect an excess clustering signal from companions down...

  13. Branes constrictions with White Dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    García-Aspeitia, Miguel A., E-mail: aspeitia@fisica.uaz.edu.mx [Consejo Nacional de Ciencia y Tecnología, Av, Insurgentes Sur 1582, Colonia Crédito Constructor, Del. Benito Juárez, C.P. 03940, Mexico, D.F. (Mexico); Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad esquina con Paseo a la Bufa S/N, C.P. 98060, Zacatecas (Mexico)

    2015-11-06

    We consider here a robust study of stellar dynamics for white dwarf stars with polytropic matter in the weak-field approximation using the Lane–Emden equation from the brane-world scenario. We also derive an analytical solution to the nonlocal energy density and show the behavior and sensitivity of these stars to the presence of extra dimensions. Similarly, we analyze stability and compactness, in order to show whether it is possible to agree with the conventional wisdom of white dwarfs dynamics. Our results predict an average value of the brane tension of <λ>≳84.818 MeV{sup 4}, with a standard deviation σ≃82.021 MeV{sup 4}, which comes from a sample of dwarf stars, being weaker than other astrophysical observations but remaining higher than cosmological results provided by nucleosynthesis among others.

  14. Branes constrictions with White Dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Aspeitia, Miguel A. [Consejo Nacional de Ciencia y Tecnologia, Mexico (Mexico); Unidad Academica de Fisica, Universidad Autonoma de Zacatecas (Mexico)

    2015-11-15

    We consider here a robust study of stellar dynamics for white dwarf stars with polytropic matter in the weak-field approximation using the Lane-Emden equation from the brane-world scenario. We also derive an analytical solution to the nonlocal energy density and show the behavior and sensitivity of these stars to the presence of extra dimensions. Similarly, we analyze stability and compactness, in order to show whether it is possible to agree with the conventional wisdom of white dwarfs dynamics. Our results predict an average value of the brane tension of left angle λ right angle >or similar 84.818 MeV{sup 4}, with a standard deviation σ ≅ 82.021 MeV{sup 4}, which comes from a sample of dwarf stars, being weaker than other astrophysical observations but remaining higher than cosmological results provided by nucleosynthesis among others. (orig.)

  15. HST and Optical Data Reveal White Dwarf Cooling, Spin and Periodicities in GW Librae 3-4 Years after Outburst

    CERN Document Server

    Szkody, Paula; Gaensicke, Boris T; Henden, Arne; Sion, Edward M; Townsley, Dean; Chote, Paul; Harmer, Diane; Harpe, Eric J; Hermes, J J; Sullivan, Denis J; Winget, D E

    2012-01-01

    Since the large amplitude 2007 outburst which heated its accreting, pulsating white dwarf, the dwarf nova system GW Librae has been cooling to its quiescent temperature. Our Hubble Space Telescope ultraviolet spectra combined with ground-based optical coverage during the 3rd and 4th year after outburst show that the fluxes and temperatures are still higher than quiescence (T=19,700K and 17,300K vs 16,000K pre-outburst for a log g=8.7 and d=100 pc). The K{wd} of 7.6+/-0.8 km/s determined from the CI1463 absorption line, as well as the gravitational redshift implies a white dwarf mass of 0.79+/-0.08 Msun. The widths of the UV lines imply a white dwarf rotation velocity vsin i of 40 km/s and a spin period of 209 s (for an inclination of 11 deg and a white dwarf radius of 7x10^{8} cm). Light curves produced from the UV spectra in both years show a prominent multiplet near 290 s, with higher amplitude in the UV compared to the optical, and increased amplitude in 2011 vs 2010. As the presence of this set of periods...

  16. Satellite Dwarf Galaxies in a Hierarchical Universe: The Prevalence of Dwarf-Dwarf Major Mergers

    CERN Document Server

    Deason, Alis; Garrison-Kimmel, Shea

    2014-01-01

    Mergers are a common phenomenon in hierarchical structure formation, especially for massive galaxies and clusters, but their importance for dwarf galaxies in the Local Group remains poorly understood. We investigate the frequency of major mergers between dwarf galaxies in the Local Group using the ELVIS suite of cosmological zoom-in dissipationless simulations of Milky Way- and M31-like host halos. We find that ~10% of satellite dwarf galaxies with M_star > 10^6 M_sun that are within the host virial radius experienced a major merger of stellar mass ratio closer than 0.1 since z = 1, with a lower fraction for lower mass dwarf galaxies. Recent merger remnants are biased towards larger radial distance and more recent virial infall times, because most recent mergers occurred shortly before crossing within the virial radius of the host halo. Satellite-satellite mergers also occur within the host halo after virial infall, catalyzed by the large fraction of dwarf galaxies that fell in as part of a group. The merger ...

  17. The SW Sex-type star 2MASS J01074282+4845188: an unusual bright accretion disk with non-steady emission and a hot white dwarf

    CERN Document Server

    Khruzina, T; Kjurkchieva, D; 10.1051/0004-6361/201220385

    2013-01-01

    We present new photometric and spectral observations of the newly discovered nova-like eclipsing star 2MASS J01074282+4845188. To obtain a light curve solution we used model of a nova-like star whose emission sources are a white dwarf surrounded by an accretion disk, a secondary star filling its Roche lobe, a hot spot and a hot line. 2MASS J01074282+4845188 shows the deepest permanent eclipse among the known nova-like stars. It is reproduced by covering the very bright accretion disk by the secondary component. The luminosity of the disk is much bigger than that of the rest light sources. The determined high temperature of the disk is typical for that observed during the outbursts of CVs. The primary of 2MASS J01074282+4845188 is one of the hottest white dwarfs in CVs. The temperature of 5090 K of its secondary is also quite high and more appropriate for a long-period SW Sex star. It might be explained by the intense heating from the hot white dwarf and the hot accretion disk of the target. The high mass accr...

  18. Structure of accretion flows in nova-like cataclysmic variables: RW Sextantis and 1RXS J064434.5+334451

    Science.gov (United States)

    Hernandez, M. S.; Zharikov, S.; Neustroev, V.; Tovmassian, G.

    2017-09-01

    New time-resolved optical spectroscopic echelle observations of the nova-like cataclysmic variable RW Sextantis were obtained, with the aim of studying the properties of emission features in the system. The profile of the H α emission line can be clearly divided into two ('narrow' and 'wide') components. Similar emission profiles are observed in another nova-like system, 1RXS J064434.5+33445, for which we also reanalysed the spectral data and redetermined the system parameters. The source of the 'narrow', low-velocity component is the irradiated face of the secondary star. We disentangled and removed the 'narrow' component from the H α profile to study the origin and structure of the region emitting the wide component. We found that the 'wide' component is not related to the white dwarf or the wind from the central part of the accretion disc, but is emanated from the outer side of the disc. Inspection of literature on similar systems indicates that this feature is common for some other long-period nova-like variables. We propose that the source of the 'wide' component is an extended, low-velocity region in the outskirts of the opposite side of the accretion disc, with respect to the collision point of the accretion stream and the disc.

  19. Search for Soft X-ray Flashes at Fireball Phase of Classical/Recurrent Novae using MAXI/GSC data

    CERN Document Server

    Morii, Mikio; Mihara, Tatehiro; Matsuoka, Masaru; Kawai, Nobuyuki

    2016-01-01

    We searched for precursive soft X-ray flashes (SXFs) associated with optically-discovered classical or recurrent novae in the data of five-years all-sky observations with Gas Slit Camera (GSC) of the Monitor of All-sky X-ray Image (MAXI). We first developed a tool to measure fluxes of point sources by fitting the event distribution with the model that incorporates the point-spread function (PSF-fit) to minimize the potential contamination from nearby sources. Then we applied the PSF-fit tool to 40 classical/recurrent novae that were discovered in optical observations from 2009 August to 2014 August. We found no precursive SXFs with significance above $3 \\sigma$ level in the energy range of 2$-$4 keV between $t_{d}-10$d and $t_{d}$, where $t_{d}$ is the date when each nova was discovered. We obtained the upper limits for the bolometric luminosity of SXFs, and compared them with the theoretical prediction and that observed for MAXI J0158$-$744. This result could constrain the population of massive white dwarfs ...

  20. On mixing at the core-envelope interface during classical nova outbursts

    CERN Document Server

    Casanova, Jordi; Garcia-Berro, Enrique; Calder, Alan; Shore, Steven N; 10.1051/0004-6361/201014178

    2010-01-01

    Classical novae are powered by thermonuclear runaways that occur on the white dwarf component of close binary systems. During these violent stellar events, whose energy release is only exceeded by gamma-ray bursts and supernova explosions, about 10-4 10-5 Msun of material is ejected into the interstellar medium. Because of the high peak temperatures attained during the explosion, Tpeak ~ (1-4)x10+8 K, the ejecta are enriched in nuclear-processed material relative to solar abundances, containing significant amounts of 13C, 15N, and 17O and traces of other isotopes. The origin of these metal enhancements observed in the ejecta is not wellknown and has puzzled theoreticians for about 40 years. In this paper, we present new 2-D simulations of mixing at the core-envelope interface. We show that Kelvin-Helmholtz instabilities can naturally lead to self-enrichment of the solar-like accreted envelopes with material from the outermost layers of the underlying white dwarf core, at levels that agree with observations.

  1. Assisted stellar suicide: the wind-driven evolution of the recurrent nova T Pyxidis

    Science.gov (United States)

    Knigge, Ch.; King, A. R.; Patterson, J.

    2000-12-01

    We show that the extremely high luminosity of the short-period recurrent nova T Pyx in quiescence can be understood if this system is a wind-driven supersoft x-ray source (SSS). In this scenario, a strong, radiation-induced wind is excited from the secondary star and accelerates the binary evolution. The accretion rate is therefore much higher than in an ordinary cataclysmic binary at the same orbital period, as is the luminosity of the white dwarf primary. In the steady state, the enhanced luminosity is just sufficient to maintain the wind from the secondary. The accretion rate and luminosity predicted by the wind-driven model for T Pyx are in good agreement with the observational evidence. X-ray observations with Chandra or XMM may be able to confirm T Pyx's status as a SSS. T Pyx's lifetime in the wind-driven state is on the order of a million years. Its ultimate fate is not certain, but the system may very well end up destroying itself, either via the complete evaporation of the secondary star, or in a Type Ia supernova if the white dwarf reaches the Chandrasekhar limit. Thus either the primary, the secondary, or both may currently be committing assisted stellar suicide.

  2. M31N 2008-12a - The Remarkable Recurrent Nova in M31

    CERN Document Server

    Darnley, M J

    2016-01-01

    M31N 2008-12a is a remarkable recurrent nova within the Andromeda Galaxy. With eleven eruptions now identified, including eight in the past eight years, the system exhibits a recurrence period of one year, and possibly just six months. This short inter eruption period is driven by the combination of a high mass white dwarf ($1.38\\,\\mathrm{M}_\\odot$) and high mass accretion rate ($\\sim1.6\\times10^{-7}\\,\\mathrm{M}_\\odot\\,\\mathrm{yr}^{-1}$). Such a high accretion rate appears to be provided by the stellar wind of a red giant companion. Deep H$\\alpha$ observations have revealed the presence of a vastly extended nebula around the system, which could be the `super-remnant' of many thousands of past eruptions. With a prediction of the white dwarf reaching the Chandrasekhar mass in less than a mega-year, M31N 2008-12a has become the leading pre-explosion type Ia supernova candidate. The 2016 eruption - to be the twelfth detected eruption - is expected imminently, and a vast array of follow-up observations are already...

  3. Microlensing Binaries with Candidate Brown Dwarf Companions

    DEFF Research Database (Denmark)

    Shin, I.-G; Han, C.; Gould, A.

    2012-01-01

    Brown dwarfs are important objects because they may provide a missing link between stars and planets, two populations that have dramatically different formation histories. In this paper, we present the candidate binaries with brown dwarf companions that are found by analyzing binary microlensing...... masses of the brown dwarf companions are 0.02 ± 0.01 M⊙ and 0.019 ± 0.002 M⊙ for MOA-2011-BLG-104/OGLE-2011-BLG-0172 and MOA-2011-BLG-149, respectively, and both companions are orbiting low-mass M dwarf host stars. More microlensing brown dwarfs are expected to be detected as the number of lensing events...

  4. Design and synthesis of dual 5-HT1A and 5-HT7 receptor ligands.

    Science.gov (United States)

    Ofori, Edward; Zhu, Xue Y; Etukala, Jagan R; Peprah, Kwakye; Jordan, Kamanski R; Adkins, Adia A; Bricker, Barbara A; Kang, Hye J; Huang, Xi-Ping; Roth, Bryan L; Ablordeppey, Seth Y

    2016-08-15

    5-HT1A and 5-HT7 receptors have been at the center of discussions recently due in part to their major role in the etiology of major central nervous system diseases such as depression, sleep disorders, and schizophrenia. As part of our search to identify dual targeting ligands for these receptors, we have carried out a systematic modification of a selective 5HT7 receptor ligand culminating in the identification of several dual 5-HT1A and 5-HT7 receptor ligands. Compound 16, a butyrophenone derivative of tetrahydroisoquinoline (THIQ), was identified as the most potent agent with low nanomolar binding affinities to both receptors. Interestingly, compound 16 also displayed moderate affinity to other clinically relevant dopamine receptors. Thus, it is anticipated that compound 16 may serve as a lead for further exploitation in our quest to identify new ligands with the potential to treat diseases of CNS origin.

  5. Tycho Brahe and the Nova of 1572

    Science.gov (United States)

    Gingerich, O.

    2005-12-01

    The brilliant Nova of 1572 marked the beginning of the end of Aristotelian cosmology and provided the defining moment when the young Tycho Brahe became a professional astronomer. He received more than a ton of gold from the Danish king to build his Uraniborg Observatory. His instruments, the finest produced in the pre-telescopic age, enabled him to establish that both the nova and the Comet of 1577 lay beyond the moon, contrary to Aristotle's teaching. His major attempt to establish the distance to Mars (in order to distinguish between the Ptolemaic and Copernican cosmologies) failed, but left in its wake a magnificently accurate set of data that enabled Kepler to make the greatest advance in celestial mechanics since Copernicus himself.

  6. Quark Nova Model for Fast Radio Bursts

    CERN Document Server

    Shand, Zachary; Koning, Nico; Ouyed, Rachid

    2015-01-01

    FRBs are puzzling, millisecond, energetic radio transients with no discernible source; observations show no counterparts in other frequency bands. The birth of a quark star from a parent neutron star experiencing a quark nova - previously thought undetectable when born in isolation - provides a natural explanation for the emission characteristics of FRBs. The generation of unstable r-process elements in the quark nova ejecta provides millisecond exponential injection of electrons into the surrounding strong magnetic field at the parent neutron star's light cylinder via $\\beta$-decay. This radio synchrotron emission has a total duration of hundreds of milliseconds and matches the observed spectrum while reducing the inferred dispersion measure by approximately 200 cm$^{-3}$ pc. The model allows indirect measurement of neutron star magnetic fields and periods in addition to providing astronomical measurements of $\\beta$-decay chains of unstable neutron rich nuclei. Using this model, we can calculate expected FR...

  7. Neutrino Oscillation Results from NOvA

    CERN Document Server

    CERN. Geneva

    2016-01-01

    NOvA is an accelerator long-baseline neutrino oscillation experiment optimised to measure electron neutrino appearance in a high-purity beam of muon neutrinos from Fermilab. The exciting discovery of the theta13 neutrino mixing angle in 2012 has opened a door to making multiple new measurements of neutrinos. These include leptonic CP violation, the neutrino mass ordering and the octant of theta23. NOvA with its 810km baseline and higher energy beam has about triple the matter effect of T2K which opens a new window on the neutrino mass ordering. With about 20% of our design beam exposure and significant analysis improvements we have recently released updated results. I will present both our disappearance and appearance measurements.

  8. The SuperNova Early Warning System

    OpenAIRE

    Scholberg, K.

    2008-01-01

    A core collapse in the Milky Way will produce an enormous burst of neutrinos in detectors world-wide. Such a burst has the potential to provide an early warning of a supernova's appearance. I will describe the nature of the signal, the sensitivity of current detectors, and SNEWS, the SuperNova Early Warning System, a network designed to alert astronomers as soon as possible after the detected neutrino signal.

  9. Nova pulse power system description and status

    Energy Technology Data Exchange (ETDEWEB)

    Holloway, R.W.; Whitham, K.; Merritt, B.T.; Gritton, D.G.; Oicles, J.A.

    1981-06-01

    The Nova laser system is designed to produce critical data in the nation's inertial confinement fusion effort. It is the world's largest peak power laser and presents various unique pulse power problems. In this paper, pulse power systems for this laser are described, the evolutionary points from prior systems are pointed out, and the current status of the hardware is given.

  10. The 5-HT hypothesis of schizophrenia.

    Science.gov (United States)

    Akhondzadeh, S

    2001-03-01

    Schizophrenia is a serious psychiatric illness that is responsible for a substantial proportion of mental illness worldwide. Symptoms include hallucination, delusions, thought disorder and negative symptoms, including poverty of thought and emotion, and social withdrawal. Early theories of schizophrenia implicated disturbed serotonin (5-HT) neurotransmission, but these were largely overshadowed by the dopamine theory of schizophrenia, which became established after the introduction of chlorpromazine. However, the importance of 5-HT in CNS function is once again being recognized. The ability of antipsychotic drugs to diminish positive symptoms has been correlated with their ability to block dopamine D(2) receptors, although negative symptoms are not as effectively treated by typical neuroleptics. There is increasing interest in the correlation between negative symptoms of schizophrenia and 5-HT(2) receptors. The rationale for these studies is the hypothesis that abnormal neurotransmission at 5-HT(2) receptors may be involved in the pathophysiology of schizophrenia. This review highlights recent pharmacological and clinical advances in the understanding of the potential use of serotonin 5-HT(2) receptor antagonists in the treatment of schizophrenia.

  11. PHP-HT (VitaResc Biotech).

    Science.gov (United States)

    Baldwin, A; Wiley, E

    2001-04-01

    VitaResc (formerly Apex) is developing PHP-HT, pyridoxalated hemoglobin polyoxyethylene conjugate, for the potential treatment of nitric oxide-induced shock (characterized by hypotension), associated with various etiologies, initially in septic shock. A phase I safety study and an initial phase I/II patient trial for NO-induced shock have been completed, and VitaResc has enrolled patients in three of five planned cohorts in a continuation of these trials to include a protocol of continuous infusion and dose escalation [330680,349187,390918]. The results from the dose escalation trials are expected to provide the basis for a randomized, controlled phase II/III pivotal trial of PHP-HT [390918]. VitaResc has licensed PHP-HT exclusively from Ajinomoto for all indications, worldwide, except Japan [275263]. Ajinomoto originally developed the human derived and chemically modified hemoglobin preparation as a blood substitute, but no development has been reported by the company since 1997 [275277,303577]. The other potential indications of PHP-HT include shock associated with burns, pancreatitis, hemodialysis and cytokine therapies [275277]. VitaResc expects the annual market potential of PHP-HT to exceed 1 billion dollars [330680].

  12. Shocks in nova outflows. I. Thermal emission

    CERN Document Server

    Metzger, Brian D; Vurm, Indrek; Beloborodov, Andrei M; Chomiuk, Laura; Sokoloski, J L; Nelson, Thomas

    2014-01-01

    Evidence for shocks in nova outflows include (1) multiple velocity components in the optical spectra; (2) keV X-ray emission weeks to months after the outburst; (3) early radio flare on timescales of months, in excess of that predicted from the freely expanding photo-ionized gas; and (4) ~ GeV gamma-rays. We present a 1D model for the shock interaction between the fast nova outflow and a dense external shell (DES) and its associated thermal X-ray, optical, and radio emission. The forward shock is radiative initially when the density of shocked gas is highest, at which times radio emission originates from the dense cooling layer immediately downstream of the shock. The radio light curve is characterized by sharper rises to maximum and later peak times at progressively lower frequencies, with a peak brightness temperature that is approximately independent of frequency. We apply our model to the recent gamma-ray classical nova V1324 Sco, obtaining an adequate fit to the early radio maximum for reasonable assumpt...

  13. Introduction to the Nova technical contract

    Energy Technology Data Exchange (ETDEWEB)

    Lindl, J.D.; Kilkenny, J.D.

    1996-06-01

    The 1990 National Academy of Sciences (NAS) final report recommended proceeding with the construction of a 1-to 2-MJ Nd-doped glass laser designed to achieve ignition in the laboratory (a laser originally called the Nova Upgrade, but now called the National Ignition Facility, or NIF, and envisioned as a national user facility). As a prerequisite, the report recommended completion of a series of target physics objectives on the Nova laser in use at the Lawrence Livermore National Laboratory (LLNL). Meeting these objectives, which were called the Nova Technical Contract (NTC), would demonstrate (the Academy committee believed) that the physics of ignition targets was understood well enough that the laser requirements could be accurately specified. Completion of the NTC objectives was given the highest priority (it was Recommendation 1.1) in the NAS report. The NAS committee also recommended a concentrated effort on advanced target design for ignition. As recommended in the report, completion of these objectives has been the joint responsibility of LLNL and the Los Alamos National Laboratory. Most of the articles in this issue of the ICF Quarterly were written jointly by scientists from both institutions. The original NTC objectives have been largely met. This Introduction summarizes those objectives and their motivation in the context of the requirements for ignition.

  14. Antagonism of 5-HT1A receptors uncovers an excitatory effect of SSRIs on 5-HT neuronal activity, an action probably mediated by 5-HT7 receptors

    NARCIS (Netherlands)

    Bosker, Fokko J.; Folgering, Joost H. A.; Gladkevich, Anatoliy V.; Schmidt, Anne; van der Hart, Marieke C. G.; Sprouse, Jeffrey; den Boer, Johan A.; Westerink, Ben H. C.; Cremers, Thomas I. F. H.

    2009-01-01

    Both microdialysis and electrophysiology were used to investigate whether another serotonin (5-HT) receptor subtype next to the 5-HT1A autoreceptor is involved in the acute effects of a selective serotonin reuptake inhibitor on 5-HT neuronal activity. On the basis of a previous study, we decided to

  15. White dwarfs in cataclysmic variables

    Science.gov (United States)

    Gaensicke, Boris

    2016-07-01

    Cataclysmic variables (CVs) provide excellent laboratories to study the effect that the accretion of matter, energy and angular momentum has on the structure of white dwarfs, with important implications on the evolution of these compact binaries, the ignition of thermonuclear surface burning, and potentially their explosion as SNIa. I will provide an overview of our current understanding of CV white dwarfs, with a particular emphasis on the results of a recent large HST program. I will review our knowledge regarding the mass distribution of CV white dwarfs, as well as the secular mean accretion rates that can be inferred from their effective temperatures, and compare those statistics with predictions from CV population models. I will also discuss a sub-set of CVs which underwent thermal-time scale mass transfer, one of the channels that is often discussed as a pathway to SN Ia, and I will illustrate how the study of these "failed SNIa" can contribute to the discussion of SNIa progenitors. Finally, I will discuss the occurrence of non-radial pulsations in white dwarfs, both in CVs and their detached progenitors.

  16. Manganese in dwarf spheroidal galaxies

    NARCIS (Netherlands)

    North, P.; Cescutti, G.; Jablonka, P.; Hill, V.; Shetrone, M.; Letarte, B.; Lemasle, B.; Venn, K. A.; Battaglia, G.; Tolstoy, E.; Irwin, M. J.; Primas, F.; Francois, P.

    We provide manganese abundances (corrected for the effect of the hyperfine structure) for a large number of stars in the dwarf spheroidal galaxies Sculptor and Fornax, and for a smaller number in the Carina and Sextans dSph galaxies. Abundances had already been determined for a number of other

  17. THREE NEW ECLIPSING WHITE-DWARF-M-DWARF BINARIES DISCOVERED IN A SEARCH FOR TRANSITING PLANETS AROUND M-DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Law, Nicholas M. [Dunlap Institute for Astronomy and Astrophysics, University of Toronto, 50 St. George St., Toronto, ON M5S 3H4 (Canada); Kraus, Adam L. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Street, Rachel; Fulton, Benjamin J.; Shporer, Avi; Lister, Tim [Las Cumbres Observatory Global Telescope Network, Inc., 6740 Cortona Dr. Suite 102, Santa Barbara, CA 93117 (United States); Hillenbrand, Lynne A.; Baranec, Christoph; Bui, Khanh; Davis, Jack T. C.; Dekany, Richard G.; Kulkarni, S. R.; Ofek, Eran O. [Cahill Center for Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Bloom, Joshua S.; Cenko, S. Bradley; Filippenko, Alexei V. [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States); Burse, Mahesh P.; Das, H. K. [Inter-University Centre for Astronomy and Astrophysics, Ganeshkhind, Pune-411007 (India); Kasliwal, Mansi M. [Carnegie Institution for Science, 813 Santa Barbara St., Pasadena, CA 91101 (United States); Nugent, Peter [Computational Cosmology Center, Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); and others

    2012-10-01

    We present three new eclipsing white-dwarf/M-dwarf binary systems discovered during a search for transiting planets around M-dwarfs. Unlike most known eclipsing systems of this type, the optical and infrared emission is dominated by the M-dwarf components, and the systems have optical colors and discovery light curves consistent with being Jupiter-radius transiting planets around early M-dwarfs. We detail the PTF/M-dwarf transiting planet survey, part of the Palomar Transient Factory (PTF). We present a graphics processing unit (GPU)-based box-least-squares search for transits that runs approximately 8 Multiplication-Sign faster than similar algorithms implemented on general purpose systems. For the discovered systems, we decompose low-resolution spectra of the systems into white-dwarf and M-dwarf components, and use radial velocity measurements and cooling models to estimate masses and radii for the white dwarfs. The systems are compact, with periods between 0.35 and 0.45 days and semimajor axes of approximately 2 R{sub Sun} (0.01 AU). The M-dwarfs have masses of approximately 0.35 M{sub Sun }, and the white dwarfs have hydrogen-rich atmospheres with temperatures of around 8000 K and have masses of approximately 0.5 M{sub Sun }. We use the Robo-AO laser guide star adaptive optics system to tentatively identify one of the objects as a triple system. We also use high-cadence photometry to put an upper limit on the white-dwarf radius of 0.025 R{sub Sun} (95% confidence) in one of the systems. Accounting for our detection efficiency and geometric factors, we estimate that 0.08%{sub -0.05%}{sup +0.10%} (90% confidence) of M-dwarfs are in these short-period, post-common-envelope white-dwarf/M-dwarf binaries where the optical light is dominated by the M-dwarf. The lack of detections at shorter periods, despite near-100% detection efficiency for such systems, suggests that binaries including these relatively low-temperature white dwarfs are preferentially found at

  18. Cataclysmic Variables and a Candidate Helium White Dwarf in the Globular Cluster NGC 6397

    CERN Document Server

    Edmonds, P D; Cool, A M; Cohn, H N; Lugger, P M; Bailyn, C D; Edmonds, Peter D.; Grindlay, Jonathan E.; Cool, Adrienne M.; Cohn, Haldan N.; Lugger, Phyllis N.; Bailyn, Charles D.

    1999-01-01

    We have used HST/FOS to study faint UV stars in the core of the nearby globular cluster NGC 6397. We confirm the presence of a 4th cataclysmic variable (CV) in NGC 6397 (CV 4), and we use the photometry of Cool et al. (1998) to present evidence that CVs 1--4 all have faint disks and probably low accretion rates. By combining these results with new UV spectra of CV 1 and the published spectra of Grindlay et al. (1995) we present new evidence that CVs 1--3 may be DQ Her systems, and we show that CV 4 may either be a dwarf nova or another magnetic system. Another possibility is that the CVs could be old novae in hibernation between nova eruptions. We also present the first spectrum of a member of a new class of UV bright stars in NGC 6397. These faint, hot stars do not vary, unlike the CVs, and are thus denoted as ``non-flickerers'' (NFs). Like the CVs, their spatial concentration is strongly concentrated toward the cluster center. Using stellar atmosphere models we have determined log g = 6.25, and T_eff = 17,5...

  19. High trait aggression in men is associated with low 5-HT levels, as indexed by 5-HT4 receptor binding

    DEFF Research Database (Denmark)

    da Cunha-Bang, Sofi; Mc Mahon, Brenda; Fisher, Patrick MacDonald;

    2016-01-01

    Impulsive aggression has commonly been associated with a dysfunction of the serotonin (5-HT) system: many, but not all, studies point to an inverse relationship between 5-HT and aggression. As cerebral 5-HT4 receptor (5-HT4R) binding has recently been recognized as a proxy for stable brain levels...... of 5-HT, we here test the hypothesis in healthy men and women that brain 5-HT levels, as indexed by cerebral 5-HT4R, are inversely correlated with trait aggression and impulsivity. Sixty-one individuals (47 men) underwent positron emission tomography scanning with the radioligand [(11)C]SB207145...... for quantification of brain 5-HT4R binding. The Buss-Perry Aggression Questionnaire (BPAQ) and the Barratt Impulsiveness Scale were used for assessment of trait aggression and trait impulsivity. Among male subjects, there was a positive correlation between global 5-HT4R and BPAQ total score (P = 0.037) as well...

  20. Experimental study of the {sup 22}Ne(p,{gamma}){sup 23}Na reaction and its implications for novae scenarios

    Energy Technology Data Exchange (ETDEWEB)

    Menzel, Marie-Luise

    2013-08-01

    The {sup 22}Ne(p,{gamma}){sup 23}Na reaction belongs to the catalytic neon-sodium cycle and has an important role in the explosive hydrogen burning. The neon-sodium cycle takes place at temperatures of T = 0.1 - 0.5 GK and is assumed to occur in different astrophysical systems: e.g. in novae, in super novae of type Ia and during the shell-burning of red giant branch stars. The implications of {sup 22}Ne(p,{gamma}){sup 23}Na and the neon-sodium cycle in a nova scenario have been studied by using the nuclear network code libnucnet at GSI in Darmstadt. A nova is an outburst of matter in a binary system consisting of a white dwarf and a red giant star. It is therefore a representative phenomenon for explosive hydrogen burning. For the calculation of the nucleosynthesis during the nova outburst, the code libnucnet requires the initial mass composition of the novae partners, the temperature and density profiles of the nova explosion and the thermonuclear reaction rates of the participating reactions. In the following, the code determined the flow and the final atomic abundance in the neon-sodium cycle during the entire nova process. Additionally, the influence of the temperature profile of the novae outburst as well as the thermonuclear reaction rate of the {sup 22}Ne(p,{gamma}){sup 23}Na reaction on the final atomic abundance in the outburst has been studied. A characteristic measure for the reactions in astrophysical environments is the thermonuclear reaction rate. The reaction rate of {sup 22}Ne(p,{gamma}){sup 23}Na has still strong uncertainties in the temperature range of T = 0.03 - 0.3 GK. These uncertainties are based on insufficient upper limits of the resonance strengths as well as the possible existence of tentative states that are populated in the energy range of E{sup lab}{sub p} = 30 - 300 keV. The research presented in this thesis is dedicated to the experimental study of the {sup 22}Ne(p,{gamma}){sup 23}Na reaction for an improved determination of the

  1. AR Sco: A White Dwarf Synchronar

    CERN Document Server

    Katz, J I

    2016-01-01

    The emission of the white dwarf-M dwarf binary AR Sco is driven by the rapid synchronization of its white dwarf, rather than by accretion. This requires a comparatively large magnetic field $\\sim 100$ gauss at the M dwarf and $\\sim 10^8$ gauss on the white dwarf, larger than the fields of most intermediate polars but within the range of fields of known magnetic white dwarfs. The spindown power is dissipated in the atmosphere of the M dwarf by magnetic reconnection, accelerating particles that produce the observed synchrotron radiation. The displacement of the optical maximum from conjunction may be explained either by dissipation in a bow wave as the white dwarf's magnetic field sweeps past the M dwarf or by a misaligned white dwarf's rotation axis and oblique magnetic moment. In the latter case the rotation axis precesses with a period of decades, predicting a drift in the orbital phase of maximum. Binaries whose emission is powered by synchronization may be termed synchronars, in analogy to magnetars.

  2. Model of the Recurrent Nova CI Aql

    Science.gov (United States)

    Lederle, C.; Kimeswenger, S.

    CI Aql was observed with the Innsbruck 60cm telescope in VRIC from June to October 2001. To reproduce the resulting light curves, a geometrical model of the double star system was realized in MATLAB-code. Already existing and rather basic routines were used to implement difficult ray-tracing and rendering tasks. For the geometrical model itself an extended rim of the accretion disk and the illumination of the other components by the white dwarf turned out to be very important.

  3. Rapid Oscillations in Cataclysmic Variables. XV. HT Camelopardalis (= RX J0757.0+6306)

    CERN Document Server

    Kemp, J; Thorstensen, J R; Fried, R E; Skillman, D R; Billings, G W; Kemp, Jonathan; Patterson, Joseph; Thorstensen, John; Fried, Robert; Skillman, David; Billings, Gary

    2002-01-01

    We present photometry and spectroscopy of HT Camelopardalis, a recently discovered X-ray-bright cataclysmic variable. The spectrum shows bright lines of H, He I, and He II, all moving with a period of 0.059712(1) d, which we interpret as the orbital period. The star's brightness varies with a strict period of 515.0592(2) s, and a mean full amplitude of 0.11 mag. These properties qualify it as a /bona fide/ DQ Herculis star (intermediate polar) -- in which the magnetism of the rapidly rotating white dwarf channels accretion flow to the surface. Normally at V=17.8, the star shows rare and very brief outbursts to V=12-13. We observed one in December 2001, and found that the 515 s pulse amplitude had increased by a factor of ~100 (in flux units). A transient orbital signal may also have appeared.

  4. Evolution of Cataclysmic Variables and Related Binaries Containing a White-Dwarf

    CERN Document Server

    Kalomeni, B; Rappaport, S; Molnar, M; Quintin, J; Yakut, K

    2016-01-01

    We present a binary evolution study of cataclysmic variables (CVs) and related systems with white dwarf accretors, including for example, AM CVn systems, classical novae, supersoft X-ray sources, and systems with giant donor stars. Our approach intentionally avoids the complications associated with population synthesis algorithms thereby allowing us to present the first truly comprehensive exploration of all of the subsequent binary evolution pathways that ZACVs might follow (assuming fully non-conservative, Roche-lobe overflow onto an accreting WD) using the sophisticated binary stellar evolution code MESA. The grid consists of 56,000 initial models, including 14 white dwarf accretor masses, 43 donor-star masses ($0.1-4.7$ $M_{\\odot}$), and 100 orbital periods. We explore evolution tracks in the orbital period and donor-mass ($P_{\\rm orb}-M_{\\rm don}$) plane in terms of evolution dwell times, masses of the white dwarf accretor, accretion rate, and chemical composition of the center and surface of the donor s...

  5. Next generation population synthesis of accreting white dwarfs: I. Hybrid calculations using BSE + MESA

    CERN Document Server

    Chen, Hai-Liang; Yungelson, L R; Gilfanov, M; Han, Zhanwen

    2014-01-01

    Accreting, nuclear-burning white dwarfs have been deemed to be candidate progenitors of SNe Ia, and to account for supersoft X-ray sources, novae, etc. We have carried out a binary population synthesis (BPS) study of hydrogen-accreting WDs. First, we use the BPS code \\textsf{BSE} as a baseline for the commonly used "rapid" approach. Second, we apply a "hybrid" approach: we use \\textsf{BSE} to generate a population of WDs with non-degenerate companions on the verge of mass transfer. We then follow their evolution using the detailed stellar evolutionary code \\textsf{MESA}. We investigate the evolution of the number of rapidly accreting white dwarfs (RAWDs), stably nuclear-burning white dwarfs (SNBWDs), and the SNe Ia rate produced by "single-degenerate" systems (SD). The two algorithms differ significantly in the predicted numbers of SNBWDs at early and late times, and also in the delay time distribution (DTD) of SD SNe Ia. The differences in the treatment of mass transfer may partially account for differences ...

  6. Bossa Nova: Introducing modularity into the Bossa Nova domain-specific language

    DEFF Research Database (Denmark)

    Lawall, Julia Laetitia; Duschene, Hervé; Muller, Gilles;

    2005-01-01

    Domain-specific languages (DSLs) have been proposed as a solution to ease the development of programs within a program family. Sometimes, however, experience with the use of a DSL reveals the presence of subfamilies within the family targeted by the language. We are then faced with the question...... modular language, Bossa Nova, and assess the language quantitatively and qualitatively....

  7. Nova como sistema operativo embebido para hardware cubano Nova as embedded operating system for cuban hardware

    Directory of Open Access Journals (Sweden)

    José Ernesto Torres Sánchez

    2012-05-01

    Full Text Available Este trabajo expone los resultados de construir un sistema operativo embebido basado en Nova, el cual brinda las funcionalidades necesarias para crear el Cliente Ligero Cubano, utilizando como componente de hardware, la Computadora en una Tarjeta CID 300/9 diseñada por el Instituto Central de Investigación Digital. Obteniéndose la primera versión de Nova para la arquitectura de computadora Advanced RISC Machine y el primer sistema operativo base, estable y de propósito general para la CID 300/9. Se expone un estado del arte de los sistemas operativos embebidos más utilizados actualmente; la estructura de la solución, los métodos y herramientas empleados para obtenerla.This paper presents the results of the construction a an embedded operating system based on Nova, which provides the needed features to create the Cuban Thin Client, using as hardware component the Computer on a CID 300/9 Board designed by the Central Institute for Digital Research, obtaining the first version of Nova for the Advance RISC Machine  computer architecture and the first base operating system, stable and for general purposes for the CID 300/9. A state of the art of the currently most used embedded operating systems, the solution's structure, the methods and tools used for its development are presented.

  8. Nova as embedded operating system for cuban hardware Nova como sistema operativo embebido para hardware cubano

    Directory of Open Access Journals (Sweden)

    Mijail Hurtado Fedorovich

    2012-05-01

    Full Text Available This paper presents the results of the construction a an embedded operating system based on Nova, which provides the needed features to create the Cuban Thin Client, using as hardware component the Computer on a CID 300/9 Board designed by the Central Institute for Digital Research, obtaining the first version of Nova for the Advance RISC Machine  computer architecture and the first base operating system, stable and for general purposes for the CID 300/9. A state of the art of the currently most used embedded operating systems, the solution's structure, the methods and tools used for its development are presented. Este trabajo expone los resultados de construir un sistema operativo embebido basado en Nova, el cual brinda las funcionalidades necesarias para crear el Cliente Ligero Cubano, utilizando como componente de hardware, la Computadora en una Tarjeta CID 300/9 diseñada por el Instituto Central de Investigación Digital. Obteniéndose la primera versión de Nova para la arquitectura de computadora Advanced RISC Machine y el primer sistema operativo base, estable y de propósito general para la CID 300/9. Se expone un estado del arte de los sistemas operativos embebidos más utilizados actualmente; la estructura de la solución, los métodos y herramientas empleados para obtenerla.

  9. Explosive lithium production in the classical nova V339 Del (Nova Delphini 2013)

    CERN Document Server

    Tajitsu, Akito; Naito, Hiroyuki; Arai, Akir; Aoki, Wako

    2015-01-01

    The origin of lithium (Li) and its production process have long been an unsettled question in cosmology and astrophysics. Candidates environments of Li production events or sites suggested by previous studies include big bang nucleosynthesis, interactions of energetic cosmic rays with interstellar matter, evolved low mass stars, novae, and supernova explosions. Chemical evolution models and observed stellar Li abundances suggest that at least half of the present Li abundance may have been produced in red giants, asymptotic giant branch (AGB) stars, and novae. However, no direct evidence for the supply of Li from stellar objects to the Galactic medium has yet been found. Here we report on the detection of highly blue-shifted resonance lines of the singly ionized radioactive isotope of beryllium, $^{7}$Be, in the near ultraviolet (UV) spectra of the classical nova V339 Del (Nova Delphini 2013). Spectra were obtained 38 to 48 days after the explosion. $^{7}$Be decays to form $^{7}$Li within a short time (half-li...

  10. Magnetic fields in Local Group dwarf irregulars

    CERN Document Server

    Chyzy, Krzysztof T; Beck, Rainer; Bomans, Dominik J

    2011-01-01

    We clarify whether strong magnetic fields can be effectively generated in typically low-mass dwarf galaxies and what is the role of dwarf galaxies in the magnetization of the Universe. We performed a search for radio emission and magnetic fields in an unbiased sample of 12 Local Group (LG) irregular and dwarf irregular galaxies with the 100m Effelsberg telescope at 2.64 and 4.85GHz. Magnetic fields in LG dwarfs are three times weaker than in the normal spirals (6muG) are observed only in dwarfs of extreme characteristics while typical LG dwarfs are not suitable objects for efficient supply of magnetic fields to the intergalactic medium.

  11. High trait aggression in men is associated with low 5-HT levels, as indexed by 5-HT4 receptor binding.

    Science.gov (United States)

    da Cunha-Bang, Sofi; Mc Mahon, Brenda; Fisher, Patrick MacDonald; Jensen, Peter Steen; Svarer, Claus; Knudsen, Gitte Moos

    2016-04-01

    Impulsive aggression has commonly been associated with a dysfunction of the serotonin (5-HT) system: many, but not all, studies point to an inverse relationship between 5-HT and aggression. As cerebral 5-HT4 receptor (5-HT4R) binding has recently been recognized as a proxy for stable brain levels of 5-HT, we here test the hypothesis in healthy men and women that brain 5-HT levels, as indexed by cerebral 5-HT4R, are inversely correlated with trait aggression and impulsivity. Sixty-one individuals (47 men) underwent positron emission tomography scanning with the radioligand [(11)C]SB207145 for quantification of brain 5-HT4R binding. The Buss-Perry Aggression Questionnaire (BPAQ) and the Barratt Impulsiveness Scale were used for assessment of trait aggression and trait impulsivity. Among male subjects, there was a positive correlation between global 5-HT4R and BPAQ total score (P = 0.037) as well as BPAQ physical aggression (P = 0.025). No main effect of global 5-HT4R on trait aggression or impulsivity was found in the mixed gender sample, but there was evidence for sex interaction effects in the relationship between global 5-HT4R and BPAQ physical aggression. In conclusion we found that low cerebral 5-HT levels, as indexed by 5-HT4R binding were associated with high trait aggression in males, but not in females.

  12. ECONOMIA SOCIAL INCORPORATIVA (e as novas linguagens

    Directory of Open Access Journals (Sweden)

    Welinton dos Santos

    2017-05-01

    Full Text Available A inovação tecnológica aliada à interação de comunicação sem limites, chamada de “Economia Social Incorporativa”, sendo uma rede integrada e sociável as populações do mundo. Baseada em uma pesquisa bibliográfica de caráter qualitativo e documental mostrando que a comunicação, informações e tecnologias evoluem surgindo novos materiais em destaque o grafeno, composto por átomos de carbono com alta condutividade térmica e elétrica, flexível e resistente, material que pode substituir o silício e permitir a segunda revolução tecnológica e levando consigo a economia. Com esses feitos tecnológicos a humanidade tende a estar mais do que nunca com uma ligação inseparável das novas tecnologias que vem aparecendo de forma exponencial no mercado estimulando assim mais do que nunca a economia social. O futuro visa uma nova economia que está em transformação, provocando mudanças significativas na política econômica mundial, e por isso, todos os esforços nesta nova dinâmica de conscientização do comportamento social integrativo auxilia numa política estratégica global mais justa e igualitária.

  13. The Experiment of Modulated Toroidal Current on HT-7 and HT-6M Tokamak

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The Experiments of Modulated Toroidal Current were done on the HT-6M tokamakand HT-7 superconducting tokamak. The toroidal current was modulated by programming theOhmic heating field. Modulation of the plasma current has been used successfully to suppressMHD activity in discharges near the density limit where large MHD m = 2 tearing modes weresuppressed by sufficiently large plasma current oscillations. The improved Ohmic confinementphase was observed during modulating toroidal current (MTC) on the Hefei Tokamak-6M (HT-6M) and Hefei superconducting Tokamak-7 (HT-7). A toroidal frequency-modulated current,induced by a modulated loop voltage, was added on the plasma equilibrium current. The ratio ofA.C. amplitude of plasma current to the main plasma current △Ip/Ip is about 12% ~ 30%. Thedifferent formats of the frequency-modulated toroidal current were compared.

  14. Parametric Dwarf Spheroidal Tidal Interaction

    CERN Document Server

    Fleck, J J; Fleck, Jean-Julien; Kuhn, Jeff R.

    2003-01-01

    The time dependent tidal interaction of the Local Group Dwarf Spheroidal (dS) Galaxies with the Milky Way (MW) can fundamentally affect their dynamical properties. The model developed here extends earlier numerical descriptions of dS-MW tidal interactions. We explore the dynamical evolution of dS systems in circular or elliptical MW orbits in the framework of a parametric oscillator. An analytic model is developed and compared with more general numerical solutions and N-body simulation experiments.

  15. Dark matter in dwarf galaxies

    OpenAIRE

    Roos, Matts

    2017-01-01

    Although the cusp-core controversy for dwarf galaxies is seen as a problem, I argue that the cored central profiles can be explained by flattened cusps because they suffer from conflicting measurements and poor statistics and because there is a large number of conventional processes that could have flattened them since their creation, none of which requires new physics. Other problems, such as "too big to fail", are not discussed.

  16. Supernova hydrodynamics experiments using the Nova laser

    Energy Technology Data Exchange (ETDEWEB)

    Remington, B.A.; Glendinning, S.G.; Estabrook, K.; Wallace, R.J.; Rubenchik, A. [Lawrence Livermore National Lab., CA (United States); Kane, J.; Arnett, D. [Arizona Univ., Tucson, AZ (United States). Stewart Observatory; Drake, R.P. [Michigan Univ., Ann Arbor, MI (United States); McCray, R. [Colorado Univ., Boulder, CO (United States)

    1997-04-01

    We are developing experiments using the Nova laser to investigate two areas of physics relevant to core-collapse supernovae (SN): (1) compressible nonlinear hydrodynamic mixing and (2) radiative shock hydrodynamics. In the former, we are examining the differences between the 2D and 3D evolution of the Rayleigh-Taylor instability, an issue critical to the observables emerging from SN in the first year after exploding. In the latter, we are investigating the evolution of a colliding plasma system relevant to the ejecta-stellar wind interactions of the early stages of SN remnant formation. The experiments and astrophysical implications are discussed.

  17. As novas estruturas organizacionais das bolsas

    OpenAIRE

    Marcos Galileu Lorena Dutra

    2008-01-01

    O presente trabalho investiga as novas estruturas organizacionais das bolsas de valores e das bolsas de mercadorias e futuros, implementadas após os processos de desmutualização. É feita uma análise da importância das bolsas para o desenvolvimento econômico, bem como do seu papel de entidades auto-reguladoras. São ainda apresentados os principais fatores que motivaram a conversão das bolsas de associações mutualísticas para sociedades anônimas, bem como as conseqüências dessa alteração organi...

  18. 10% discount at Novae restaurants for students

    CERN Multimedia

    2016-01-01

    A 10% discount will be granted for students dining in restaurants 1 and 2 (on the Meyrin site) during the summer from 15 June 2016 to 15 September 2016.   A special badge will be issued by the respective secretariats if the student fulfils the following criteria:  Is under 25 years old; Is in possession of a student card issued by a University or college; Has a CERN contract > 1 month (Users, Summer Students, Trainees, etc). This badge and the CERN access card will have to be shown at the Novae restaurants in order to benefit from this discount.

  19. As novas estruturas organizacionais das bolsas

    OpenAIRE

    Marcos Galileu Lorena Dutra

    2008-01-01

    O presente trabalho investiga as novas estruturas organizacionais das bolsas de valores e das bolsas de mercadorias e futuros, implementadas após os processos de desmutualização. É feita uma análise da importância das bolsas para o desenvolvimento econômico, bem como do seu papel de entidades auto-reguladoras. São ainda apresentados os principais fatores que motivaram a conversão das bolsas de associações mutualísticas para sociedades anônimas, bem como as conseqüências dessa alteração organi...

  20. The Structure of Brown Dwarf Circumstellar Disks

    OpenAIRE

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

    2004-01-01

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

  1. Magnetars and White Dwarf Pulsars

    CERN Document Server

    Lobato, Ronaldo V; Coelho, Jaziel G

    2016-01-01

    The Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs) are a class of pulsars understood as neutron stars (NSs) with super strong surface magnetic fields, namely $B\\gtrsim10^{14}$ G, and for that reason are known as Magnetars. However, in the last years some SGRs/AXPs with low surface magnetic fields $B\\sim(10^{12}-10^{13})$ G have been detected, challenging the Magnetar description. Moreover, some fast and very magnetic white dwarfs (WDs) have also been observed, and at least one showed X-Ray energy emission as an ordinary pulsar. Following this fact, an alternative model based on white dwarfs pulsars has been proposed to explain this special class of pulsars. In this model, AXPs and SGRs as dense and magnetized white dwarfs can have surface magnetic field $B\\sim 10^{7}-10^{10}$ G and rotate very fast with frequencies $\\Omega\\sim 1$ rad/s, consistent with the observed rotation periods $P\\sim (2-12)$ s.

  2. Microlensing, Brown Dwarfs and GAIA

    CERN Document Server

    Evans, N W

    2014-01-01

    The GAIA satellite can precisely measure the masses of nearby brown dwarfs and lower main sequence stars by the microlensing effect. The scientific yield is maximised if the microlensing event is also followed with ground-based telescopes to provide densely sampled photometry. There are two possible strategies. First, ongoing events can be triggered by photometric or astrometric alerts by GAIA. Second, events can be predicted using known high proper motion stars as lenses. This is much easier, as the location and time of an event can be forecast. Using the GAIA source density, we estimate that the sample size of high proper motion ($>300$ mas yr$^{-1}$) brown dwarfs needed to provide predictable events during the 5 year mission lifetime is surprisingly small, only of the order of a hundred. This is comparable to the number of high proper motion brown dwarfs already known from the work of the UKIDSS Large Area Survey and the all-sky WISE satellite. Provided the relative parallax of the lens and the angular Ein...

  3. Lopsidedness in dwarf irregular galaxies

    CERN Document Server

    Heller, A B; Almoznino, E; Van Zee, L; Salzer, J J; Heller, Ana B.; Brosch, Noah; Almoznino, Elchanan; Zee, Liese van; Salzer, John J.

    2000-01-01

    We quantify the amplitude of the lopsidedness, the azimuthal angular asymmetry index, and the concentration of star forming regions, as represented by the distribution of the H$\\alpha$ emission, in a sample of 78 late-type irregular galaxies. We bin the observed galaxies in two groups representing blue compact galaxies (BCDs) and low surface brightness dwarf galaxies (LSBs). The light distribution is analysed with a novel algorithm, which allows detection of details in the light distribution pattern. We find that while the asymmetry of the underlying continuum light, representing the older stellar generations, is relatively small, the H$\\alpha$ emission is very asymmetric and is correlated in position angle with the continuum light. We test a model of random star formation over the extent of a galaxy by simulating HII regions in artificial dwarf galaxies. The implication is that random star formation over the full extent of a galaxy may be generated in LSB dwarf-irregular galaxies but not in BCD galaxies.

  4. Aryl biphenyl-3-ylmethylpiperazines as 5-HT7 receptor antagonists.

    Science.gov (United States)

    Kim, Jeeyeon; Kim, Youngjae; Tae, Jinsung; Yeom, Miyoung; Moon, Bongjin; Huang, Xi-Ping; Roth, Bryan L; Lee, Kangho; Rhim, Hyewhon; Choo, Il Han; Chong, Youhoon; Keum, Gyochang; Nam, Ghilsoo; Choo, Hyunah

    2013-11-01

    The 5-HT7 receptor (5-HT7 R) is a promising therapeutic target for the treatment of depression and neuropathic pain. The 5-HT7 R antagonist SB-269970 exhibited antidepressant-like activity, whereas systemic administration of the 5-HT7 R agonist AS-19 significantly inhibited mechanical hypersensitivity and thermal hyperalgesia. In our efforts to discover selective 5-HT7 R antagonists or agonists, aryl biphenyl-3-ylmethylpiperazines were designed, synthesized, and biologically evaluated against the 5-HT7 R. Among the synthesized compounds, 1-([2'-methoxy-(1,1'-biphenyl)-3-yl]methyl)-4-(2-methoxyphenyl)piperazine (28) was the best binder to the 5-HT7 R (pKi =7.83), and its antagonistic property was confirmed by functional assays. The selectivity profile of compound 28 was also recorded for the 5-HT7 R over other serotonin receptor subtypes, such as 5-HT1 R, 5-HT2 R, 5-HT3 R, and 5-HT6 R. In a molecular modeling study, the 2-methoxyphenyl moiety attached to the piperazine ring of compound 28 was proposed to be essential for the antagonistic function.

  5. White Dwarf Critical Tests for Modified Gravity

    CERN Document Server

    Jain, Rajeev Kumar; Nielsen, Niklas Grønlund

    2015-01-01

    Scalar-tensor theories of gravity can lead to modifications of the gravitational force inside astrophysical objects. We exhibit that compact stars such as white dwarfs provide a unique set-up to test such deviations from Newtonian gravitational physics inside the stars. We obtain stringent and independent constraints on the parameter $\\Upsilon$ characterizing the deviations from gravity using the mass-radius relation, the Chandrasekhar mass limit and the maximal rotational frequency of white dwarfs. We find that white dwarfs impose stronger constraints on $\\Upsilon$ than the red and brown dwarfs.

  6. White dwarf cooling sequences and cosmochronology

    CERN Document Server

    Isern, J; Garcia-Berro, E

    2012-01-01

    The evolution of white dwarfs is a simple gravothermal process. This means that their luminosity function, i.e. the number of white dwarfs per unit bolometric magnitude and unit volume as a function of bolometric magnitude, is a monotonically increasing function that decreases abruptly as a consequence of the finite age of the Galaxy. The precision and the accuracy of the white dwarf luminosity functions obtained with the recent large surveys together with the improved quality of the theoretical models of evolution of white dwarfs allow to feed the hope that in a near future it will be possible to reconstruct the history of the different Galactic populations.

  7. The Blue Straggler Population in Dwarf Galaxies

    CERN Document Server

    Momany, Yazan

    2014-01-01

    In this chapter I review the recent developments regarding the study of Blue Stragglers (BSS) in dwarf galaxies. The loose density environment of dwarf galaxies resembles that of the Galactic Halo, hence it is natural to compare their common BSS properties. At the same time, it is unescapable to compare with the BSS properties in Galactic Globular clusters, which constitute the reference point for BSS studies. Admittedly, the literature on BSS in dwarf galaxies is not plentiful. The limitation is mostly due to the large distance to even the closest dwarf galaxies. Nevertheless, recent studies have allowed a deeper insight on the BSS photometric properties that are worth examining.

  8. Conservation of 5-HT1A receptor-mediated autoinhibition of serotonin (5-HT neurons in mice with altered 5-HT homeostasis

    Directory of Open Access Journals (Sweden)

    Naozumi eAraragi

    2013-08-01

    Full Text Available Firing activity of serotonin (5-HT neurons in the dorsal raphe nucleus (DRN is controlled by inhibitory somatodendritic 5-HT1A autoreceptors. This autoinhibitory mechanism is implicated in the etiology of disorders of emotion regulation, such as anxiety disorders and depression, as well as in the mechanism of antidepressant action. Here, we investigated how persistent alterations in brain 5-HT availability affect autoinhibition in two genetically modified mouse models lacking critical mediators of serotonergic transmission: 5-HT transporter knockout (Sert -/- and tryptophan hydroxylase-2 knockout (Tph2 -/- mice. The degree of autoinhibition was assessed by loose-seal cell-attached recording in DRN slices. First, application of the 5-HT1A-selective agonist R(+-8-hydroxy-2-(di-n-propylaminotetralin showed mild sensitization and marked desensitization of 5-HT1A receptors in Tph2 -/- mice and Sert -/- mice, respectively. While 5-HT neurons from Tph2 -/- mice did not display autoinhibition in response to L-tryptophan, autoinhibition of these neurons was unaltered in Sert -/- mice despite marked desensitization of their 5-HT1A autoreceptors. When the Tph2-dependent 5-HT synthesis step was bypassed by application of 5-hydroxy-L-tryptophan (5-HTP, neurons from both Tph2 -/- and Sert -/- mice decreased their firing rates at significantly lower concentrations of 5-HTP compared to wildtype controls. Our findings demonstrate that, as opposed to the prevalent view, sensitivity of somatodendritic 5-HT1A receptors does not predict the magnitude of 5-HT neuron autoinhibition. Changes in 5-HT1A receptor sensitivity may rather be seen as an adaptive mechanism to keep autoinhibition functioning in response to extremely altered levels of extracellular 5-HT resulting from targeted inactivation of mediators of serotonergic signaling.

  9. Cyclic guanidines as dual 5-HT5A/5-HT7 receptor ligands: structure-activity relationship elucidation.

    Science.gov (United States)

    Peters, Jens-Uwe; Lübbers, Thomas; Alanine, Alexander; Kolczewski, Sabine; Blasco, Francesca; Steward, Lucinda

    2008-01-01

    The optimisation of affinity and selectivity in a novel series of dual 5-HT5A/5-HT7 receptor ligands is described. Brain penetrant 2-aminodihydroquinazolines with low nanomolar affinities were identified.

  10. The Nova Rate in M94 (NGC4736)

    CERN Document Server

    Gueth, T; Misselt, K A

    2010-01-01

    A multi-epoch H$\\alpha$ survey of the early-type spiral galaxy M94 (NGC 4736) has been completed as part of a program to establish the galaxy's nova rate. A total of 4 nova candidates were discovered in 7 epochs of observation during the period from 2005 to 2007. After making corrections for temporal coverage and spatial completeness, a global nova rate of 5.0$^{+1.8}_{-1.4}$ yr$^{-1}$ was determined. This rate corresponds to a specific-luminosity nova rate of 1.4 $\\pm$ 0.5 novae per year per 10$^{10} L_{\\odot,K}$ when the K luminosity is determined from the B - K color, or 1.5 $\\pm$ 0.4 novae per year per 10$^{10} L_{\\odot,K}$ when the K luminosity is derived from the Two Micron All Sky Survey. These values are slightly lower than that of other galaxies with measured nova rates, which typically lie in the range of 2-3 novae per year per 10$^{10} L_{\\odot}$ in the K band.

  11. A Spectroscopic and Photometric Survey of Novae in M31

    CERN Document Server

    Shafter, A W; Hornoch, K; Filippenko, A V; Bode, M F; Ciardullo, R; Misselt, K A; Hounsell, R A; Chornock, R; Matheson, T

    2011-01-01

    We report the results of a multi-year spectroscopic and photometric survey of novae in M31 that resulted in a total of 53 spectra of 48 individual nova candidates. Two of these, M31N 1995-11e and M31N 2007-11g, were revealed to be long-period Mira variables, not novae. These data double the number of spectra extant for novae in M31 through the end of 2009 and bring to 91 the number of M31 novae with known spectroscopic classifications. We find that 75 novae (82%) are confirmed or likely members of the Fe II spectroscopic class, with the remaining 16 novae (18%) belonging to the He/N (and related) classes. These numbers are consistent with those found for Galactic novae. We find no compelling evidence that spectroscopic class depends sensitively on spatial position or population within M31 (i.e., bulge vs. disk), although the distribution for He/N systems appears slightly more extended than that for the Fe II class. We confirm the existence of a correlation between speed class and ejection velocity (based on l...

  12. The progenitor of Nova Cygni 2006 (=V2362 Cyg)

    NARCIS (Netherlands)

    Steeghs, D.; Greimel, R.; Drew, J.; Irwin, M.; Gaensicke, B.; Groot, P.J.; Knigge, C.

    2006-01-01

    We report on the detection of the likely progenitor to Nova Cygni 2006 = V2362 Cyg (IAUC #8697, #8698, ATel #792) using images from the INT Photometric H-Alpha Survey (IPHAS; http://www.iphas.org). The field containing the classical nova was observed as part of our galactic plane survey on Aug. 3rd

  13. Some misapplied nomina nova in reef coral taxonomy (Scleractinia)

    NARCIS (Netherlands)

    Hoeksema, B.W.

    1993-01-01

    Nomina nova should be used only to denote replacement names for preoccupied names, i.e. in the case of homonymy. Three examples of incorrect applications of nomina nova in scleractinian taxonomy are given. Coincidentally, in the cases discussed each wrongly proposed nomen novum concerns a new specie

  14. Results of Statewide TerraNova Testing, Fall 1998.

    Science.gov (United States)

    La Marca, Paul M.

    This summary provides key findings about state, district, and school level performance on the TerraNova examinations (CTB/McGraw Hill) in Nevada in 1998-1999. The TerraNova tests are used to assess students in grades 4, 8, and 10 as stipulated by Nevada law. Within this summary, a description of performance as measured by national percentile…

  15. NOVA: a software to analyze complexome profiling data

    NARCIS (Netherlands)

    Giese, H.; Ackermann, J.; Heide, H.; Bleier, L.; Drose, S.; Wittig, I.; Brandt, U.; Koch, I.

    2015-01-01

    SUMMARY: We introduce nova, a software for the analysis of complexome profiling data. nova supports the investigation of the composition of complexes, cluster analysis of the experimental data, visual inspection and comparison of experiments and many other features. AVAILABILITY AND IMPLEMENTATION:

  16. 5-HT2A and 5-HT2C receptors as hypothalamic targets of developmental programming in male rats

    Directory of Open Access Journals (Sweden)

    Malgorzata S. Martin-Gronert

    2016-04-01

    Full Text Available Although obesity is a global epidemic, the physiological mechanisms involved are not well understood. Recent advances reveal that susceptibility to obesity can be programmed by maternal and neonatal nutrition. Specifically, a maternal low-protein diet during pregnancy causes decreased intrauterine growth, rapid postnatal catch-up growth and an increased risk for diet-induced obesity. Given that the synthesis of the neurotransmitter 5-hydroxytryptamine (5-HT is nutritionally regulated and 5-HT is a trophic factor, we hypothesised that maternal diet influences fetal 5-HT exposure, which then influences development of the central appetite network and the subsequent efficacy of 5-HT to control energy balance in later life. Consistent with our hypothesis, pregnant rats fed a low-protein diet exhibited elevated serum levels of 5-HT, which was also evident in the placenta and fetal brains at embryonic day 16.5. This increase was associated with reduced levels of 5-HT2CR, the primary 5-HT receptor influencing appetite, in the fetal, neonatal and adult hypothalamus. As expected, a reduction of 5-HT2CR was associated with impaired sensitivity to 5-HT-mediated appetite suppression in adulthood. 5-HT primarily achieves effects on appetite by 5-HT2CR stimulation of pro-opiomelanocortin (POMC peptides within the arcuate nucleus of the hypothalamus (ARC. We show that 5-HT2ARs are also anatomically positioned to influence the activity of ARC POMC neurons and that mRNA encoding 5-HT2AR is increased in the hypothalamus of in utero growth-restricted offspring that underwent rapid postnatal catch-up growth. Furthermore, these animals at 3 months of age are more sensitive to appetite suppression induced by 5-HT2AR agonists. These findings not only reveal a 5-HT-mediated mechanism underlying the programming of susceptibility to obesity, but also provide a promising means to correct it, by treatment with a 5-HT2AR agonist.

  17. 5-HT2A and 5-HT2C receptors as hypothalamic targets of developmental programming in male rats

    Science.gov (United States)

    Martin-Gronert, Malgorzata S.; Stocker, Claire J.; Wargent, Edward T.; Cripps, Roselle L.; Garfield, Alastair S.; Jovanovic, Zorica; D'Agostino, Giuseppe; Yeo, Giles S. H.; Cawthorne, Michael A.; Arch, Jonathan R. S.; Heisler, Lora K.; Ozanne, Susan E.

    2016-01-01

    ABSTRACT Although obesity is a global epidemic, the physiological mechanisms involved are not well understood. Recent advances reveal that susceptibility to obesity can be programmed by maternal and neonatal nutrition. Specifically, a maternal low-protein diet during pregnancy causes decreased intrauterine growth, rapid postnatal catch-up growth and an increased risk for diet-induced obesity. Given that the synthesis of the neurotransmitter 5-hydroxytryptamine (5-HT) is nutritionally regulated and 5-HT is a trophic factor, we hypothesised that maternal diet influences fetal 5-HT exposure, which then influences development of the central appetite network and the subsequent efficacy of 5-HT to control energy balance in later life. Consistent with our hypothesis, pregnant rats fed a low-protein diet exhibited elevated serum levels of 5-HT, which was also evident in the placenta and fetal brains at embryonic day 16.5. This increase was associated with reduced levels of 5-HT2CR, the primary 5-HT receptor influencing appetite, in the fetal, neonatal and adult hypothalamus. As expected, a reduction of 5-HT2CR was associated with impaired sensitivity to 5-HT-mediated appetite suppression in adulthood. 5-HT primarily achieves effects on appetite by 5-HT2CR stimulation of pro-opiomelanocortin (POMC) peptides within the arcuate nucleus of the hypothalamus (ARC). We show that 5-HT2ARs are also anatomically positioned to influence the activity of ARC POMC neurons and that mRNA encoding 5-HT2AR is increased in the hypothalamus of in utero growth-restricted offspring that underwent rapid postnatal catch-up growth. Furthermore, these animals at 3 months of age are more sensitive to appetite suppression induced by 5-HT2AR agonists. These findings not only reveal a 5-HT-mediated mechanism underlying the programming of susceptibility to obesity, but also provide a promising means to correct it, by treatment with a 5-HT2AR agonist. PMID:26769798

  18. Legislating Interprofessional Regulatory Collaboration in Nova Scotia

    Directory of Open Access Journals (Sweden)

    William Lahey

    2013-10-01

    Full Text Available To shift health professions regulation from traditional to ‘collaborative’ self-regulation, Nova Scotia has adopted legislation which will: make all self-regulating health professions members of the Regulated Health Professions Network; mandate the Network to facilitate voluntary collaboration among its members; and enable regulators to work together on investigations of patient complaints, to adjust scopes of practice on an ongoing basis and to adjudicate appeals of unsuccessful applicants for registration. The goals are to give health professions regulation the capacity to enable and support the functioning of interprofessional teams. The legislation was adopted primarily for two reasons: collaborative development and unanimous support by all of the province’s self-regulating professions; and alignment with the government’s health care reform agenda and its emphasis on collaborative team-based care. Contrary to the approach of several other provinces, the legislation will enable but not require regulators to collaborate on the premise that consensual collaboration is more likely to happen, to be meaningful and to yield tangible benefits. Support for this approach can be taken from the impressive collaborative work on which the legislation is based. Evaluation will be critical, and the five-year review required by the legislation will give Nova Scotia the opportunity to test not only the legislation but the ideas on which it is based. The extent of the legislation’s reliance on voluntary process will prove to be either its greatest strength or its greatest weakness.

  19. The nature and evolution of Nova Cygni 2006

    CERN Document Server

    Munari, U; Henden, A; Cardarelli, G; Cherini, G; Dallaporta, S; Via, G Dalla; Frigo, A; Jurdana-Sepic, R; Moretti, S; Ochner, P; Tomaselli, S; Tomasoni, S; Valisa, P; Navasardyan, H; Valentini, M

    2008-01-01

    AIMS: Nova Cyg 2006 has been intensively observed throughout its full outburst. We investigate the energetics and evolution of the central source and of the expanding ejecta, their chemical abundances and ionization structure, and the formation of dust. METHOD: We recorded low, medium, and/or high-resolution spectra (calibrated into accurate absolute fluxes) on 39 nights, along with 2353 photometric UBVRcIc measures on 313 nights, and complemented them with IR data from the literature. RESULTS: The nova displayed initially the normal photometric and spectroscopic evolution of a fast nova of the FeII-type. Pre-maximum, principal, diffuse-enhanced, and Orion absorption systems developed in a normal way. After the initial outburst, the nova progressively slowed its fading pace until the decline reversed and a second maximum was reached (eight months later), accompanied by large spectroscopic changes. Following the rapid decline from second maximum, the nova finally entered the nebular phase and formed optically ...

  20. Role of 5-HT1B, 5-HT2A and 5-HT2C receptors in learning.

    Science.gov (United States)

    Meneses, A; Hong, E

    1997-08-01

    The effects of post-training (i.p.) injection of TFMPP, mCPP, DOI or 1-NP in the autoshaping learning task was explored. Furthermore, the post-training effects of these agonists after treatment with the antagonists (+/-)-pindolol, (+/-)-propranolol, NAN-190, ketanserin, ritanserin, mesulergine, MDL-72222 or p-chloroamphetamine (5-HT depleter) were studied. Rats were individually trained with a lever-press response (conditioned response; CR) on the autoshaping task and tested 24 h later. The results showed that the injection of TFMPP (1-10 mg/kg), mCPP (1-10 mg/kg), 1-NP (0.1-1.0 mg/kg) or mesulergine (0.4 mg/kg) decreased the rate of CR, while DOI (0.01-0.1 mg/kg) and ritanserin (0.5 mg/kg) and ketanserin (0.001-0.1 mg/kg) increased it. However, the effect induced by TFMPP was reversed by (+/-)-pindolol, ketanserin, ritanserin and PCA; the mCPP-induced effect was antagonized by (+/-)-propranolol, ketanserin, ritanserin and MDL-72222; and the effect produced by 1-NP was reversed by ketanserin, ritanserin and PCA. In addition, the increment in CR provoked by DOI was enhanced by ketanserin, and reversed by ritanserin, mesulergine and PCA. These findings suggest that TFMPP, 1-NP and DOI exerted their effects via stimulation of presynaptic 5-HT receptors. The effects of mCPP most probably reflect activation of postsynaptic receptors. The present data suggest that both 5-HT1B and 5-HT2A-2C receptors play a significant role in the consolidation of learning.

  1. Role of 5-HT6 receptors in memory formation.

    Science.gov (United States)

    Meneses, A

    2001-09-01

    Mice lacking the 5-HT(6) receptor presented neither gross anatomical or behavioral abnormalities nor obvious changes in microscopic brain morphology, and their performance in rotarod, open field and novel object testing paradigms revealed no differences compared with wild-type animals. Nevertheless, an association between the 5-HT(6) receptor polymorphism C267T and Alzheimer's disease has been reported. Interestingly, the 5-HT(6) antisense oligonucleotide decreased 5-HT(6) gene expression and enhanced spatial learning acquisition in the water maze. Similarly, injection of the 5-HT(6) receptor antagonist Ro-04-6790 improved learning consolidation in an autoshaping task, while mCPP, scopolamine and dizocilpine decreased performance. The effect induced by scopolamine or dizocilpine, but not that induced by mCPP, was completely or partially reversed by Ro-04-6790. Ro-04-6790 did not modify the 8-OH-DPAT facilitatory effects on learning consolidation. Since Ro-04-6790 facilitatory effect was unaffected by 5-HT(1A), 5-HT(2A/2B/2C), 5-HT(3), 5-HT(4) or 5-HT(7) receptor blockade, the facilitatory effect induced by Ro-04-6790 involved specifically 5-HT6 receptors. Similarly, the 5-HT(6) receptor antagonist SB-271046 improved retention in the water maze and produced a significant performance improvement in aged rats in an operant-delayed alternation task. A series of Ro-04-6790 analogues that penetrate the brain and specifically bind to 5-HT(6) receptors reversed scopolamine-induced retention deficit in a passive avoidance learning test. Collectively, these data provide further support to the notion that 5-HT systems, via 5-HT(6) receptors, also play a significant role in memory formation under normal and dysfunctional memory conditions.

  2. Review: 5-Ht1, 5-Ht2, 5-Ht3, And 5-Ht7 Receptors And Their Role In The Modulation Of Pain Response In The Central Nervous System.

    Science.gov (United States)

    Cortes-Altamirano, José Luis; Olmos-Hernández, Adriana; Bonilla-Jaime, Herlinda; Carrillo-Mora, Paul; Bandala, Cindy; Reyes-Long, S; Alfaro-Rodríguez, Alfonso

    2017-09-11

    The aim of this review was to identify the mechanisms by which serotonin receptors involved at the central level are able to modulate the nociceptive response. Pain is a defense mechanism of the body that entails physiological, anatomical, neurochemical, and psychological changes, and is defined as an unpleasant sensory and emotional experience with potential risk of tissue damage, comprising the leading cause of appointments with Physicians worldwide. Treatment for this symptom has generated several neuropharmacological lines of research, due to the different types of pain and the various drugs employed to treat this condition. Serotonin [5-HydroxyTryptamine (5-HT)] is a neurotransmitter with seven families (5-HT1–5-HT7) and approximately 15 receptor subtypes. Serotonin modulates neuronal activity; however, this neurotransmitter is related with a number of physiological processes, such as cardiovascular function, gastric motility, renal function, etc. On the other hand, several researches reported that serotonin modulates nociceptive response through 5-HT1, 5-HT2, 5-HT3, and 5-HT7 receptors in the Central Nervous System (CNS). In this review, a search was conducted on PubMed, ProQuest, EBSCO, and the Science Citation Index for studies evaluating the effects of 5-HT1, 5-HT2, 5-HT3, and 5-HT7 receptors in the CNS on the modulation of different types of pain. Conclusions We concluded that 5-HT1, 5-HT2, 5-HT3, and 5-HT7 receptors in the CNS modulate the pain, but this depends on the distribution of the receptors, dose of agonists or antagonists, administration route, pain type and duration to order to inhibit, to excite, or even maintain the nociceptive response. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

  3. ULTRACAM photometry of the eclipsing cataclysmic variables GY Cnc, IR Com and HT Cas

    CERN Document Server

    Feline, W J; Marsh, T R; Watson, C A; Littlefair, S P

    2005-01-01

    We present high-speed, three-colour photometry of the eclipsing cataclysmic variables GY Cnc, IR Com and HT Cas. We find that the sharp eclipses in GY Cnc and IR Com are due to eclipses of the white dwarf. There is some evidence for a bright spot on the edge of the accretion disc in GY Cnc, but not in IR Com. Eclipse mapping of HT Cas is presented which shows changes in the structure of the quiescent accretion disc. Observations in 2002 show the accretion disc to be invisible except for the presence of a bright spot at the disc edge. 2003 observations, however, clearly show a bright inner disc and the bright spot to be much fainter than in 2002. Although no outburst was associated with either set of quiescent observations, the system was ~0.6 mJy brighter in 2003, mainly due to the enhanced emission from the inner disc. We propose that these changes are due to variations in the mass transfer rate from the secondary star and through the disc. The disc colours indicate that it is optically thin in both its inne...

  4. Observations and simulations of nova Vul 1984 no. 2: A nova with ejecta rich in oxygen, neon, and magnesium

    Science.gov (United States)

    Starrfield, S.; Sonneborn, G.; Stryker, L. L.; Sparks, Warren M.; Truran, James W.; Ferland, Gary; Wagner, R. M.; Gallagher, J. S.; Wade, R.; Williams, R. E.

    1988-01-01

    Nova Vul 1984 no. 2 was observed with IUE from Dec. 1984 through Nov. 1987. The spectra are characterized by strong lines from Mg, Ne, C, Si, O, N, and other elements. Data obtained in the ultraviolet, infrared, and optical show that this nova is ejecting material rich in oxygen, neon, and magnesium.

  5. A brown dwarf orbiting an M-dwarf

    DEFF Research Database (Denmark)

    Bachelet, E.; Fouqué, P.; Albrow, M.D.

    2012-01-01

    -Collaboration. Alerted as a high-magnification event, it was sensitive to planets. Suspected anomalies in the light curve were not confirmed by a real-time model, but further analysis revealed small deviations from a single lens extended source fit. Methods. Thanks to observations by all the collaborations, this event...... gives two local minima, which correspond to the theoretical degeneracy s ≡ s-1. We find that the lens is composed of a brown dwarf secondary of mass MS = 0.05 M⊙ orbiting a primary M-star of mass MP = 0.18 M⊙. We also reveal a new mass-ratio degeneracy for the central caustics of close binaries...

  6. 5-HT3 and 5-HT4 antagonists inhibit peristaltic contractions in guinea-pig distal colon by mechanisms independent of endogenous 5-HT

    Directory of Open Access Journals (Sweden)

    Tiong Cheng Sia

    2013-08-01

    Full Text Available Recent studies have shown that endogenous serotonin is not required for colonic peristalsis in vitro, nor gastrointestinal (GI transit in vivo. However, antagonists of 5-Hydroxytryptamine (5-HT receptors can inhibit peristalsis and GI-transit in mammals, including humans. This raises the question of how these antagonists inhibit GI-motility and transit, if depletion of endogenous 5-HT does not cause any significant inhibitory changes to either GI-motility or transit ? We investigated the mechanism by which 5-HT3 and 5-HT4 antagonists inhibit distension-evoked peristaltic contractions in guinea-pig distal colon. In control animals, repetitive peristaltic contractions of the circular muscle were evoked in response to fixed fecal pellet distension. Distension-evoked peristaltic contractions were unaffected in animals with mucosa and submucosal plexus removed, that were also treated with reserpine (to deplete neuronal 5-HT. In control animals, peristaltic contractions were blocked temporarily by ondansetron (1-10µM and SDZ-205-557 (1-10µM in many animals. Interestingly, after this temporary blockade, and whilst in the continued presence of these antagonists, peristaltic contractions recovered, with characteristics no different from controls. Surprisingly, similar effects were seen in mucosa-free preparations, which had no detectable 5-HT, as detected by mass spectrometry. In summary, distension-evoked peristaltic reflex contractions of the circular muscle layer of the guinea-pig colon can be inhibited temporarily, or permanently, in the same preparation by selective 5-HT3 and 5-HT4 antagonists, depending on the concentration of the antagonists applied. These effects also occur in preparations that lack any detectable 5-HT. We suggest caution should be exercised when interpreting the effects of 5-HT3 and 5-HT4 antagonists; and the role of endogenous 5-HT, in the generation of distension-evoked colonic peristalsis.

  7. Estimating the dose from atmospheric releases of HT

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, C.E. Jr.

    1990-11-13

    Measurements of uptake of tritium by humans and laboratory animals following exposure to tritiated hydrogen gas, HT, suggest that the radiotoxicity of HT is four orders of magnitude less than that of tritiated water, HTO. However, this analysis does not take into account the conversion of HT into HTO following release into the environment. Experimental releases of HT have demonstrated that HT release to the environment is converted to HTO by soil microorganisms. In this report two methods are used to estimate the effect of HT to HTO conversion on the inhalation dose of individuals exposed to tritium downwind of a release of HT. From this analysis it is predicted that the ratio of dose from inhalation of tritium following an atmospheric release of HT, as compared to inhalation of HTO, is closer to 0.01 than the 0.0001 attributed to simple HT inhalation. Under meteorologic conditions which keep the HT release near the surface and promote optimum soil microbial activity, the analysis suggests that the ratio of dose from an atmospheric HT release could be as high as 25% of that from an atmospheric HTO release.

  8. Diagnostics of Internal Inductance in HT-7

    Institute of Scientific and Technical Information of China (English)

    曾立; 万宝年; 钱金平; 范恒玉

    2001-01-01

    Two arrays of Mirnov coils and a pair of concentric loops have been installed to superconducting tokamak HT-7. Software compensation and digital Fourier series expansion are the two techniques that have been applied successfully in measuring diamagnetic flux of concentric loops and internal inductance. The internal inductance of plasma li, poloidal beta β-, Grad Shafranov parameter A, plasma minor radius ap and the center of the outermost magnetic flux surface △g are determined.

  9. On the role of brain 5-HT7 receptor in the mechanism of hypothermia: comparison with hypothermia mediated via 5-HT1A and 5-HT3 receptor.

    Science.gov (United States)

    Naumenko, Vladimir S; Kondaurova, Elena M; Popova, Nina K

    2011-12-01

    Intracerebroventricular administration of selective agonist of serotonin 5-HT(7) receptor LP44 (4-[2-(methylthio)phenyl]-N-(1,2,3,4-tetrahydro-1-naphthalenyl)-1-pyperasinehexanamide hydrochloride; 10.3, 20.5 or 41.0 nmol) produced considerable hypothermic response in CBA/Lac mice. LP44-induced (20.5 nmol) hypothermia was significantly attenuated by the selective 5-HT(7) receptor antagonist SB 269970 (16.1 fmol, i.c.v.) pretreatment. At the same time, intraperitoneal administration of LP44 in a wide range of doses 1.0, 2.0 or 10.0 mg/kg (2.0, 4.0, 20.0 μmol/kg) did not cause considerable hypothermic response. These findings indicate the implication of central, rather than peripheral 5-HT(7) receptors in the regulation of hypothermia. The comparison of LP44-induced (20.5 nmol) hypothermic reaction in eight inbred mouse strains (DBA/2J, CBA/Lac, C57BL/6, BALB/c, ICR, AKR/J, C3H and Asn) was performed and a significant effect of genotype was found. In the same eight mouse strains, functional activity of 5-HT(1A) and 5-HT(3) receptors was studied. The comparison of hypothermic responses produced by 5-HT(7) receptor agonist LP44 (20.5 nmol, i.c.v.) and 5-HT(1A) receptor agonist 8-OH-DPAT 1.0 mg/kg, i.p. (3.0 μmol/kg), 5-HT(3) receptor agonist m-CPBG (40.0 nmol, i.c.v.) did not reveal considerable interstrain correlations between 5-HT(7) and 5-HT(1A) or 5-HT(3) receptor-induced hypothermia. The selective 5-HT(7) receptor antagonist SB 269970 (16.1 fmol, i.c.v.) failed to attenuate the hypothermic effect of 8-OH-DPAT 1.0 mg/kg, i.p. (3.0 μmol/kg) and m-CPBG (40.0 nmol, i.c.v.) indicating that the brain 5-HT(7) receptor is not involved in the hypothermic effects of 8-OH-DPAT or m-CPBG. The obtained results suggest that the central 5-HT(7) receptor plays an essential role in the mediation of thermoregulation independent of 5-HT(1A) and 5-HT(3) receptors.

  10. The Accretion of Solar Material onto White Dwarfs: No Mixing with Core Material Implies that the Mass of the White Dwarf is Increasing

    CERN Document Server

    Starrfield, Sumner

    2015-01-01

    Cataclysmic Variables (CVs) are close binary star systems with one component an accreting white dwarf (WD) and the other a larger cooler star that fills its Roche Lobe. One consequence of the WDs accreting material, is the possibility that they are growing in mass and will eventually reach the Chandrasekhar Limit. This evolution could result in a Supernova Ia (SN Ia) explosion and is designated the Single Degenerate Progenitor (SD) scenario. One problem with the single degenerate scenario is that it is generally assumed that the accreting material mixes with WD core material at some time during the accretion phase of evolution and, since the typical WD has a carbon-oxygen (CO) core, the mixing results in large amounts of carbon and oxygen being brought up into the accreted layers. The presence of enriched carbon causes enhanced nuclear fusion and a Classical Nova (CN)explosion. Thus, the WD in a Classical Nova system is decreasing in mass and cannot be a SN Ia progenitor. In new calculations reported here, th...

  11. Vortioxetine, but not escitalopram or duloxetine, reverses memory impairment induced by central 5-HT depletion in rats: evidence for direct 5-HT receptor modulation

    DEFF Research Database (Denmark)

    Jensen, Jesper Bornø; du Jardin, Kristian Gaarn; Song, Dekun

    2014-01-01

    Depressed patients suffer from cognitive dysfunction, including memory deficits. Acute serotonin (5-HT) depletion impairs memory and mood in vulnerable patients. The investigational multimodal acting antidepressant vortioxetine is a 5-HT3, 5-HT7 and 5-HT1D receptor antagonist, 5-HT1B receptor par...

  12. AR Sco: A Precessing White Dwarf Synchronar?

    Science.gov (United States)

    Katz, J. I.

    2017-02-01

    The emission of the white dwarf–M dwarf binary AR Sco is driven by the rapid synchronization of its white dwarf, rather than by accretion. Synchronization requires a magnetic field ∼100 Gauss at the M dwarf and ∼ {10}8 Gauss at the white dwarf, larger than the fields of most intermediate polars but within the range of fields of known magnetic white dwarfs. The spindown power is dissipated in the atmosphere of the M dwarf, within the near zone of the rotating white dwarf’s field, by magnetic reconnection, accelerating particles that produce the observed synchrotron radiation. The displacement of the optical maximum from conjunction may be explained either by dissipation in a bow wave as the white dwarf’s magnetic field sweeps past the M dwarf or by a misaligned white dwarf rotation axis and oblique magnetic moment. In the latter case the rotation axis precesses with a period of decades, predicting a drift in the orbital phase of the optical maximum. Binaries whose emission is powered by synchronization may be termed synchronars, in analogy to magnetars.

  13. Stars at Low Metallicity in Dwarf Galaxies

    NARCIS (Netherlands)

    Tolstoy, Eline; Battaglia, Giuseppina; Cole, Andrew; Hunt, LK; Madden, S; Schneider, R

    2008-01-01

    Dwarf galaxies offer an opportunity to understand the properties of low metallicity star formation both today and at the earliest times at the, epoch of the formation of the first stars. Here we concentrate on two galaxies in the Local Group: the dwarf irregular galaxy Leo A, which has been the rece

  14. Radial Velocity Variability of Field Brown Dwarfs

    CERN Document Server

    Prato, L; Rice, E L; McLean, I S; Kirkpatrick, J D; Burgasser, A J; Kim, S S

    2015-01-01

    We present paper six of the NIRSPEC Brown Dwarf Spectroscopic Survey, an analysis of multi-epoch, high-resolution (R~20,000) spectra of 25 field dwarf systems (3 late-type M dwarfs, 16 L dwarfs, and 6 T dwarfs) taken with the NIRSPEC infrared spectrograph at the W. M. Keck Observatory. With a radial velocity precision of ~2 km/s, we are sensitive to brown dwarf companions in orbits with periods of a few years or less given a mass ratio of 0.5 or greater. We do not detect any spectroscopic binary brown dwarfs in the sample. Given our target properties, and the frequency and cadence of observations, we use a Monte Carlo simulation to determine the detection probability of our sample. Even with a null detection result, our 1 sigma upper limit for very low mass binary frequency is 18%. Our targets included 7 known, wide brown dwarf binary systems. No significant radial velocity variability was measured in our multi-epoch observations of these systems, even for those pairs for which our data spanned a significant ...

  15. Metals and ionizing photons from dwarf galaxies

    NARCIS (Netherlands)

    Salvadori, S.; Tolstoy, E.; Ferrara, A.; Zaroubi, S.

    2014-01-01

    We estimate the potential contribution of M <10(9)M(circle dot) dwarf galaxies to the reionization and early metal enrichment of the Milky Way environment, or circum-Galactic medium. Our approach is to use the observed properties of ancient stars ()under tilde>12 Gyr old) measured in nearby dwarf ga

  16. Magnetic White Dwarfs with Heavy Elements

    CERN Document Server

    Hardy, François; Jordan, Stefan

    2016-01-01

    Using our newly developed model atmosphere code appropriate for magnetic white dwarfs with metal lines in the Paschen-Back regime, we study various magnetic white dwarfs and explore the effects of various parameters such as the field geometry and the convective efficiency

  17. Microlensing Binaries with Candidate Brown Dwarf Companions

    DEFF Research Database (Denmark)

    Shin, I.-G; Han, C.; Gould, A.;

    2012-01-01

    Brown dwarfs are important objects because they may provide a missing link between stars and planets, two populations that have dramatically different formation histories. In this paper, we present the candidate binaries with brown dwarf companions that are found by analyzing binary microlensing ...

  18. Nova Scotia Power response to Hurricane Juan

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2003-10-01

    Hurricane Juan hit the Halifax Regional Municipality on September 28, 2003, creating the largest outage in Nova Scotia Power's history. This detailed report documents the extensive damage that Hurricane Juan caused to the power transmission and distribution system in Nova Scotia. It also reviews the massive power restoration effort, with reference to numerous interviews, computer records and data logs which offer a wide range of observations, statistics and insights into the preparation and performance of Nova Scotia Power Inc. (NSPI) and the efforts of other key organizations following the storm. NSPI organized a recovery effort that matched the intensity of the hurricane. A fire in the Scotia Square Office Tower caused the evacuation of the company's call centre. The Tufts Cove station in Dartmouth, which generates 400 megawatts of power, was forced to shut down. Excess electricity was moved into New Brunswick and other jurisdictions to maintain system stability. The main priority was to restore customers back to service. Within 5 days of the hurricane, 95 per cent of those who lost power had service restored. Hurricane Juan caused the most damage to the transmission and distribution system in NSPI's history. Three out of five high capacity transmission lines were put out of service. Three 120-foot high transmission towers fell, and 17 main transmission lines were damaged and put out of service. Forty-five major substations were affected and 145 distribution feeders were damaged or tripped off, including 106 in the Halifax Regional Municipality. Large portions of 4,500 kilometres of local distribution lines in the Halifax Regional Municipality were damaged, including thousands of kilometers across the Northeast. The power crew, consisting of 2,000 individuals from the region and neighbouring utilities in New Brunswick and Maine, worked for 15 consecutive days to replace 275 transformers, 760 power poles, and 125,000 metres of conductor wire. NSPI

  19. FROM X-RAY DIPS TO ECLIPSE: WITNESSING DISK REFORMATION IN THE RECURRENT NOVA U Sco

    Energy Technology Data Exchange (ETDEWEB)

    Ness, J.-U.; Talavera, A.; Gonzalez-Riestra, R. [XMM-Newton Science Operations Centre, ESA, P.O. Box 78, 28691 Villanueva de la Canada, Madrid (Spain); Schaefer, B. E. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Dobrotka, A. [Department of Physics, Institute of Materials Science, Faculty of Materials Science and Technology, Slovak University of Technology, Jana Bottu 25, 91724 Trnava (Slovakia); Sadowski, A. [N. Copernicus Astronomical Center, Polish Academy of Sciences, Bartycka 18, 00-716 Warszawa (Poland); Drake, J. J.; Barnard, R. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Page, K. L. [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); Hernanz, M. [Institut de Ciencies de l' Espai (CSIC-IEEC), Campus UAB, Facultat de Ciencies, C5 parell 2on, 08193 Bellaterra (Barcelona) (Spain); Sala, G. [Departament Fisica i Enginyeria Nuclear, EUETIB (UPC-IEEC), Comte d' Urgell 187, 08036 Barcelona (Spain); Starrfield, S., E-mail: juness@sciops.esa.int [School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287-1404 (United States)

    2012-01-20

    The tenth recorded outburst of the recurrent eclipsing nova U Sco was observed simultaneously in X-ray, UV, and optical by XMM-Newton on days 22.9 and 34.9 after the outburst. Two full passages of the companion in front of the nova ejecta were observed, as was the reformation of the accretion disk. On day 22.9, we observed smooth eclipses in UV and optical but deep dips in the X-ray light curve that disappeared by day 34.9, yielding clean eclipses in all bands. X-ray dips can be caused by clumpy absorbing material that intersects the line of sight while moving along highly elliptical trajectories. Cold material from the companion could explain the absence of dips in UV and optical light. The disappearance of X-ray dips before day 34.9 implies significant progress in the formation of the disk. The X-ray spectra contain photospheric continuum emission plus strong emission lines, but no clear absorption lines. Both continuum and emission lines in the X-ray spectra indicate a temperature increase from day 22.9 to day 34.9. We find clear evidence in the spectra and light curves for Thompson scattering of the photospheric emission from the white dwarf. Photospheric absorption lines can be smeared out during scattering in a plasma of fast electrons. We also find spectral signatures of resonant line scattering that lead to the observation of the strong emission lines. Their dominance could be a general phenomenon in high-inclination systems such as Cal 87.

  20. The 26gAl(p,g)27Si reaction in Novae

    Science.gov (United States)

    Ruiz, Chris; Parikh, A.; José, J.; Buchmann, L.; Caggiano, J. A.; Chen, A. A.; Clark, J. A.; Crawford, H.; Davids, B.; D'Auria, J. M.; Davis, C.; Deibel, C.; Erikson, L.; Fogarty, L.; Frekers, D.; Greife, U.; Hussein, A.; Hutcheon, D. A.; Huyse, M.; Jewett, C.; Laird, A. M.; Lewis, R.; Mumby-Croft, P.; Olin, A.; Ottewell, D. F.; Ouellet, C. V.; Parker, P.; Pearson, J.; Ruprecht, G.; Trinczek, M.; Vockenhuber, C.; Wrede, C.

    The 26gAl(p,γ)27Si Reaction in Novae PoS(NIC-IX)004 1 TRIUMF, 4004 Wesbrook Mall, Vancouver, BC V6T 2A3, Canada 2 Wright Nuclear Structure Laboratory, Yale University, New Haven, Conneticut 06520-8124, USA 3 Dept. de Física í Enginyeria Nuclear, Universitat Politécnica de Catalunya, Barcelona, Spain 4 Institut d'Estudis Espacials de Catalunya (IEEC), Barcelona, Spain 5 McMaster University, Hamilton, ON L8S 481, Canada 6 Simon Fraser University, Burnaby, BC V5A 1S6, Canada 7 Department of Physics, Colorado School of Mines, Golden, Colorado 80401, USA 8 National University of Ireland, Maynooth, Co. Kildare, Ireland 9 Institut für Kernphysik, Westfälische Willhelms-Universität Münster, 48149 Münster, Germany 10 University of Northern British Columbia, Prince George, BC V2N 4Z9, Canada 11 Katholieke Universiteit Leuven, 3000 Leuven, Belgium 12 Department of Physics, University of York, York YO10 5DD, United Kingdom The 184 keV resonance strength in the 26gAl(p,γ)27Si reaction was measured in inverse kinematics using the DRAGON facility at TRIUMF-ISAC. We obtain a value of ωγ=35±7 μeV for the strength and ER=184±1 keV for the resonance energy. These values are consistent with p-wave capture into the 7652(3) keV state in 27Si. We discuss the implications of these results for 26gAl nucleosynthesis in a typical O-Ne white dwarf nova.

  1. Ciberespaço: nova realidade, novos perigos, novas formas de defesa

    Directory of Open Access Journals (Sweden)

    Ana Maria Nicolaci-da-Costa

    Full Text Available A mídia, nacional e internacional, vem divulgando à exaustão vários tipos de perigo que supostamente rondam a utilização da Internet. Por trás dessa divulgação, parece estar um pressuposto que desafia a Psicologia: o de que somos indefesos para lidar com a nova realidade do ciberespaço. Resultados inesperados de uma pesquisa sobre o uso intensivo da Internet, no entanto, mostram o contrário. A partir destes, novas estratégias de auto-proteção online, que visam principalmente à preservação da intimidade, puderam ser identificadas. Essas estratégias envolvem diferentes formas de utilização, por parte dos usuários, dos próprios programas e recursos tecnológicos disponíveis.

  2. Equilibrium figures of dwarf planets

    Science.gov (United States)

    Rambaux, Nicolas; Chambat, Frederic; Castillo-Rogez, Julie; Baguet, Daniel

    2016-10-01

    Dwarf planets including transneptunian objects (TNO) and Ceres are >500 km large and display a spheroidal shape. These protoplanets are left over from the formation of the solar System about 4.6 billion years ago and their study could improve our knowledge of the early solar system. They could be formed in-situ or migrated to their current positions as a consequence of large-scale solar system dynamical evolution. Quantifying their internal composition would bring constraints on their accretion environment and migration history. That information may be inferred from studying their global shapes from stellar occultations or thermal infrared imaging. Here we model the equilibrium shapes of isolated dwarf planets under the assumption of hydrostatic equilibrium that forms the basis for interpreting shape data in terms of interior structure. Deviations from hydrostaticity can shed light on the thermal and geophysical history of the bodies. The dwarf planets are generally fast rotators spinning in few hours, so their shape modeling requires numerically integration with Clairaut's equations of rotational equilibrium expanded up to third order in a small parameter m, the geodetic parameter, to reach an accuracy better than a few kilometers depending on the spin velocity and mean density. We also show that the difference between a 500-km radius homogeneous model described by a MacLaurin ellipsoid and a stratified model assuming silicate and ice layers can reach several kilometers in the long and short axes, which could be measurable. This type of modeling will be instrumental in assessing hydrostaticity and thus detecting large non-hydrostatic contributions in the observed shapes.

  3. A white dwarf with an oxygen atmosphere

    Science.gov (United States)

    Kepler, S. O.; Koester, Detlev; Ourique, Gustavo

    2016-04-01

    Stars born with masses below around 10 solar masses end their lives as white dwarf stars. Their atmospheres are dominated by the lightest elements because gravitational diffusion brings the lightest element to the surface. We report the discovery of a white dwarf with an atmosphere completely dominated by oxygen, SDSS J124043.01+671034.68. After oxygen, the next most abundant elements in its atmosphere are neon and magnesium, but these are lower by a factor of ≥25 by number. The fact that no hydrogen or helium are observed is surprising. Oxygen, neon, and magnesium are the products of carbon burning, which occurs in stars at the high-mass end of pre-white dwarf formation. This star, a possible oxygen-neon white dwarf, will provide a rare observational test of the evolutionary paths toward white dwarfs.

  4. Disks, accretion and outflows of brown dwarfs

    CERN Document Server

    Joergens, V; Liu, Y; Pascucci, I; Whelan, E; Alcala, J; Biazzo, K; Costigan, G; Gully-Santiago, M; Henning, Th; Natta, A; Rigliaco, E; Rodriguez-Ledesma, V; Sicilia-Aguilar, A; Tottle, J; Wolf, S

    2012-01-01

    Characterization of the properties of young brown dwarfs are important to constraining the formation of objects at the extreme low-mass end of the IMF. While young brown dwarfs share many properties with solar-mass T Tauri stars, differences may be used as tests of how the physics of accretion/outflow and disk chemistry/dissipation depend on the mass of the central object. This article summarizes the presentations and discussions during the splinter session on 'Disks, accretion and outflows of brown dwarfs' held at the CoolStars17 conference in Barcelona in June 2012. Recent results in the field of brown dwarf disks and outflows include the determination of brown dwarf disk masses and geometries based on Herschel far-IR photometry (70-160 um), accretion properties based on X-Shooter spectra, and new outflow detections in the very low-mass regime.

  5. The Brown Dwarf-Exoplanet Connection

    CERN Document Server

    Burgasser, Adam J

    2009-01-01

    Brown dwarfs are commonly regarded as easily-observed templates for exoplanet studies, with comparable masses, physical sizes and atmospheric properties. There is indeed considerable overlap in the photospheric temperatures of the coldest brown dwarfs (spectral classes L and T) and the hottest exoplanets. However, the properties and processes associated with brown dwarf and exoplanet atmospheres can differ significantly in detail; photospheric gas pressures, elemental abundance variations, processes associated with external driving sources, and evolutionary effects are all pertinent examples. In this contribution, I review some of the basic theoretical and empirical properties of the currently known population of brown dwarfs, and detail the similarities and differences between their visible atmospheres and those of extrasolar planets. I conclude with some specific results from brown dwarf studies that may prove relevant in future exoplanet observations.

  6. Double White Dwarf Merger Rates

    Science.gov (United States)

    Toonen, Silvia; Nelemans, Gijs; Portegies Zwart, Simon

    2013-01-01

    Type Ia supernovae (SNe Ia) are very successfully used as standard candles on cosmological distance scales, but so far the nature of the progenitor(s) is unclear. A possible scenario for SNe Ia are merging carbon/oxygen white dwarfs with a combined mass exceeding the Chandrasekhar mass. We determine the theoretical rates and delay time distribution of these mergers for two different common envelope prescriptions and metallicities. The shape of the delay time distributions is rather insensitive to the assumptions. The normalization is a factor ~3-13 too low compared to observations.

  7. Laying the foundation for a digital Nova Scotia

    Science.gov (United States)

    Bond, J.

    2016-04-01

    In 2013, the Province of Nova Scotia began an effort to modernize its coordinate referencing infrastructure known as the Nova Scotia Coordinate Referencing System (NSCRS). At that time, 8, active GPS stations were installed in southwest Nova Scotia to evaluate the technology's ability to address the Province's coordinate referencing needs. The success of the test phase helped build a business case to implement the technology across the entire Province. It is anticipated that by the end of 2015, 40 active GPS stations will be in place across Nova Scotia. This infrastructure, known as the Nova Scotia Active Control Stations (NSACS) network, will allow for instantaneous, centimetre level positioning across the Province. Originally designed to address the needs of the surveying community, the technology has also proven to have applications in mapping, machine automation, agriculture, navigation, emergency response, earthquake detection and other areas. In the foreseeable future, all spatial data sets captured in Nova Scotia will be either directly or indirectly derived from the NSACS network. The technology will promote high accuracy and homogenous spatial data sets across the Province. The technology behind the NSACS and the development of the system are described. Examples of how the technology is contributing to a digital Nova Scotia are presented. Future applications of the technology are also considered.

  8. OGLE Atlas of Classical Novae II. Magellanic Clouds

    CERN Document Server

    Mroz, P; Poleski, R; Soszynski, I; Szymanski, M K; Pietrzynski, G; Wyrzykowski, L; Ulaczyk, K; Kozlowski, S; Pietrukowicz, P; Skowron, J

    2016-01-01

    The population of classical novae in the Magellanic Clouds was poorly known because of a lack of systematic studies. There were some suggestions that nova rates per unit mass in the Magellanic Clouds were higher than in any other galaxy. Here, we present an analysis of data collected over sixteen years by the OGLE survey with the aim of characterizing nova population in the Clouds. We found twenty eruptions of novae, half of them are new discoveries. We robustly measure the nova rates of $2.4 \\pm 0.8$ yr$^{-1}$ (LMC) and $0.9 \\pm 0.4$ yr$^{-1}$ (SMC) and confirm that K-band luminosity-specific nova rates in both Clouds are 2-3 times higher than in other galaxies. This can be explained by the star formation history in the Magellanic Clouds, specifically a re-ignition of the star formation rate a few Gyr ago. We also present the discovery of an intriguing system OGLE-MBR133.25.1160 which mimics recurrent nova eruptions.

  9. OGLE Atlas of Classical Novae. II. Magellanic Clouds

    Science.gov (United States)

    Mróz, P.; Udalski, A.; Poleski, R.; Soszyński, I.; Szymański, M. K.; Pietrzyński, G.; Wyrzykowski, Ł.; Ulaczyk, K.; Kozłowski, S.; Pietrukowicz, P.; Skowron, J.

    2016-01-01

    The population of classical novae in the Magellanic Clouds was poorly known because of a lack of systematic studies. There were some suggestions that nova rates per unit mass in the Magellanic Clouds were higher than in any other galaxy. Here, we present an analysis of data collected over 16 years by the OGLE survey with the aim of characterizing the nova population in the Clouds. We found 20 eruptions of novae, half of which are new discoveries. We robustly measure nova rates of 2.4 ± 0.8 yr-1 (LMC) and 0.9 ± 0.4 yr-1 (SMC) and confirm that the K-band luminosity-specific nova rates in both Clouds are 2-3 times higher than in other galaxies. This can be explained by the star formation history in the Magellanic Clouds, specifically the re-ignition of the star formation rate a few Gyr ago. We also present the discovery of the intriguing system OGLE-MBR133.25.1160, which mimics recurrent nova eruptions.

  10. CLIP Identifies Nova-Regulated RNA Networks in the Brain

    Science.gov (United States)

    Ule, Jernej; Jensen, Kirk B.; Ruggiu, Matteo; Mele, Aldo; Ule, Aljaž; Darnell, Robert B.

    2003-11-01

    Nova proteins are neuron-specific antigens targeted in paraneoplastic opsoclonus myoclonus ataxia (POMA), an autoimmune neurologic disease characterized by abnormal motor inhibition. Nova proteins regulate neuronal pre-messenger RNA splicing by directly binding to RNA. To identify Nova RNA targets, we developed a method to purify protein-RNA complexes from mouse brain with the use of ultraviolet cross-linking and immunoprecipitation (CLIP). Thirty-four transcripts were identified multiple times by Nova CLIP. Three-quarters of these encode proteins that function at the neuronal synapse, and one-third are involved in neuronal inhibition. Splicing targets confirmed in Nova-/- mice include c-Jun N-terminal kinase 2, neogenin, and gephyrin; the latter encodes a protein that clusters inhibitory γ-aminobutyric acid and glycine receptors, two previously identified Nova splicing targets. Thus, CLIP reveals that Nova coordinately regulates a biologically coherent set of RNAs encoding multiple components of the inhibitory synapse, an observation that may relate to the cause of abnormal motor inhibition in POMA.

  11. Nova abordagem no tratamento da esquizofrenia

    Directory of Open Access Journals (Sweden)

    Walter Speltri

    1966-12-01

    Full Text Available Foram tratados 11 casos de esquizofrenia com a guanetidina, substância considerada, do ponto de vista farmacodinâmico, como simpaticoplégica. Na opinião do autor, os surpreendentes e significativos resultados obtidos autorizam uma nova abordagem nas pesquisas à procura da etiopatogenia da esquizofrenia e, a partir dos elementos colhidos, considera plausível uma "teoria psicossomática da esquizofrenia". Recusa-se, entretanto, a cair no atraente, mas inútil, terreno especulativo. Prefere aguardar que os farmacologistas e fisiologistas forneçam dados pais precisos sobre o mecanismo de ação da guanetidina e que novos estudos confirmem seus resultados para, depois, dar publicidade à sua teoria.

  12. Novas tecnologias: Novos Professores? Novos Saberes?

    Directory of Open Access Journals (Sweden)

    Daniele Cristina Mendes

    2008-11-01

    Full Text Available RESUMO:A integração da educação com a informação-comunicação precisa ter seu lugar repensado dentro das escolas. Neste artigo tento instigar reflexões no trato das questões referentes às novas tecnologias e suas implicações na leitura, na linguagem e na formação dos professores.PALAVRAS-CHAVE: Leitura, Internet, Formação DocenteABSTRACT:The integration of education with the information and communication, must have rethought its place within the schools. In this article I try to instigate reflections on issues concerning the treatment of new technologies and their implications for reading, in language and training of teachers.KEYWORDS: Reading, Internet, Teacher educationRecebido: 30/10/2008     Aceito:30/11/2008

  13. La nova identitat visual de la EAP

    Directory of Open Access Journals (Sweden)

    Dario D. Aguillón Gutiérrez

    2015-01-01

    Full Text Available L'Escola d'Arts Plàstiques de la Universitat Autònoma de Coahuila, a Mèxic, ha estat durant dècades una de les institucions d'ensenyament d'art i disseny més importants al nord del país. Les seves necessitats de comunicació actuals, així com la seva constant creixement, van fer necessari el disseny d'una nova identitat visual, coherent amb la seva personalitat i conscient de l'entorn en què es desenvolupa. Aquest projecte va ser realitzat entre directius, docents i estudiants de l'Escola d'Arts Plàstiques, amb l'objectiu de dotar la institució d'una identitat pròpia i professional.

  14. Influence of P3HT concentration on morphological, optical and electrical properties of P3HT/PS and P3HT/PMMA binary blends

    Energy Technology Data Exchange (ETDEWEB)

    Nicho, M.E., E-mail: menicho@uaem.mx [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, Col. Chamilpa, C.P. 62209, Cuernavaca, Morelos (Mexico); Garcia-Escobar, C.H. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, Col. Chamilpa, C.P. 62209, Cuernavaca, Morelos (Mexico); Arenas, M.C. [Centro de Fisica Aplicada y Tecnologia Avanzada, UNAM, Boulevard Juriquilla No. 3001, Juriquilla, Queretaro, C.P. 76230 (Mexico); Altuzar-Coello, P. [Centro de Investigacion en Energia, UNAM, C.P. 62580, Temixco, Morelos (Mexico); Cruz-Silva, R.; Gueizado-Rodriguez, M. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, Col. Chamilpa, C.P. 62209, Cuernavaca, Morelos (Mexico)

    2011-10-25

    Poly(3-hexylthiophene) (P3HT) has interesting optoelectronic properties and a wide variety of applications such as solar cells and O-FET devices. It is a soluble conductive polymer but their mechanical properties are poor and its conductivity is unstable in environmental condition. With the finality of overcome these disadvantages, P3HT binary blends with two insulating polymers, polystyrene (PS) and polymethylmetacrilate (PMMA), have been synthesized by direct oxidation of 3-hexylthiophene with FeCl{sub 3} as oxidant inside the insulator polymers. Molecular weight and polydispersity of P3HT polymer were measured by size exclusion chromatography and the degree of regioregularity by {sup 1}H RMN. P3HT/PS and P3HT/PMMA thin films were prepared by spin-coating technique from toluene solution at different P3HT concentrations. The doped films were obtained by immersion during 30 s in a 0.3 M ferric chloride (FeCl{sub 3}) solution in nitromethane. A classical percolation phenomenon was observed in the electrical properties of the binary blends, it was smaller than 4 wt.% of P3HT in the blend. Atomic force microscopy and confocal microscopy showed a phase-separated morphology. Variation in the surface morphology of the blends was observed, which was a function of the polymer concentration and the type of insulator polymer used in the blends. The insulator polymer was segregated on the surface of the films and showed pit and island-like topography. The pit and island size changed as a function of the polymer concentration. Optical absorption properties as a function of the P3HT concentration in the undoped and doped state were analyzed. In doped state, the bipolaron bands in the PS/P3HT and PMMA/P3HT blends were observed from a P3HT concentration of 1 wt.% and 3 wt.%, respectively. Finally, the polymers were analyzed by thermogravimetric analysis and infrared spectroscopy.

  15. Formation of ultra-compact blue dwarf galaxies and their evolution into nucleated dwarfs

    CERN Document Server

    Bekki, Kenji

    2015-01-01

    We propose that there is an evolutionary link between ultra-compact blue dwarf galaxies (UCBDs) with active star formation and nucleated dwarfs based on the results of numerical simulations of dwarf-dwarf merging. We consider the observational fact that low-mass dwarfs can be very gas-rich, and thereby investigate the dynamical and chemical evolution of very gas-rich, dissipative dwarf-dwarf mergers. We find that the remnants of dwarf-dwarf mergers can be dominated by new stellar populations formed from the triggered starbursts and consequently can have blue colors and higher metallicities (Z~[0.2-1]Z_sun). We also find that the remnants of these mergers can have rather high mass-densities (10^4 M_sun pc^-3) within the central 10 pc and small half-light radii (40-100 pc). The radial stellar structures of some merger remnants are similar to those of nucleated dwarfs. Star formation can continue in nuclear gas disks (R<100 pc) surrounding stellar galactic nuclei (SGNs) so that the SGNs can finally have multi...

  16. Distributed computer control system in the Nova Laser Fusion Test Facility

    Energy Technology Data Exchange (ETDEWEB)

    1985-09-01

    The EE Technical Review has two purposes - to inform readers of various activities within the Electronics Engineering Department and to promote the exchange of ideas. The articles, by design, are brief summaries of EE work. The articles included in this report are as follows: Overview - Nova Control System; Centralized Computer-Based Controls for the Nova Laser Facility; Nova Pulse-Power Control System; Nova Laser Alignment Control System; Nova Beam Diagnostic System; Nova Target-Diagnostics Control System; and Nova Shot Scheduler. The 7 papers are individually abstracted.

  17. Throwing Icebergs at White Dwarfs

    Science.gov (United States)

    Stephan, Alexander P.; Naoz, Smadar; Zuckerman, B.

    2017-08-01

    White dwarfs (WDs) have atmospheres that are expected to consist nearly entirely of hydrogen and helium, since heavier elements will sink out of sight on short timescales. However, observations have revealed atmospheric pollution by heavier elements in about a quarter to a half of all WDs. While most of the pollution can be accounted for with asteroidal or dwarf planetary material, recent observations indicate that larger planetary bodies, as well as icy and volatile material from Kuiper belt analog objects, are also viable sources of pollution. The commonly accepted pollution mechanisms, namely scattering interactions between planetary bodies orbiting the WDs, can hardly account for pollution by objects with large masses or long-period orbits. Here we report on a mechanism that naturally leads to the emergence of massive body and icy and volatile material pollution. This mechanism occurs in wide binary stellar systems, where the mass loss of the planets’ host stars during post main sequence stellar evolution can trigger the Eccentric Kozai-Lidov mechanism. This mechanism leads to large eccentricity excitations, which can bring massive and long-period objects close enough to the WDs to be accreted. We find that this mechanism readily explains and is consistent with observations.

  18. Milliarcsecond N-Band Observations of the Nova RS Ophiuchi: First Science with the Keck Interferometer Nuller

    CERN Document Server

    Barry, R K; Traub, W A; Sokoloski, J L; Wisniewski, J P; Serabyn, E; Kuchner, M J; Akeson, R; Appleby, E; Bell, J; Booth, A; Brandenburg, H; Colavita, M; Crawford, S; Creech-Eakman, M; Dahl, W; Felizardo, C; García, J; Gathright, J; Greenhouse, M A; Herstein, J; Hovland, E; Hrynevych, M; Koresko, C; Ligon, R; Mennesson, B; Millan-Gabet, R; Morrison, D; Palmer, D; Panteleeva, T; Ragland, S; Shao, M; Smythe, R; Summers, K; Swain, M; Tsubota, K; Tyau, C; Vasisht, G; Wetherell, E; Wizinowich, P; Woillez, J

    2008-01-01

    We report observations of the nova RS Ophiuchi (RS Oph) using the Keck Interferometer Nuller (KIN), approximately 3.8 days following the most recent outburst that occurred on 2006 February 12. These observations represent the first scientific results from the KIN, which operates in N-band from 8 to 12.5 microns in a nulling mode. By fitting the unique KIN data, we have obtained an angular size of the mid-infrared continuum of 6.2, 4.0, or 5.4 mas for a disk profile, gaussian profile (FWHM), and shell profile respectively. The data show evidence of enhanced neutral atomic hydrogen emission and atomic metals including silicon located in the inner spatial regime near the white dwarf (WD) relative to the outer regime. There are also nebular emission lines and evidence of hot silicate dust in the outer spatial region, centered at ! 17 AU from the WD, that are not found in the inner regime. Our evidence suggests that these features have been excited by the nova flash in the outer spatial regime before the blast wav...

  19. Discovery of $^{34g,m}$Cl$(p,\\gamma)^{35}$Ar resonances activated at classical nova temperatures

    CERN Document Server

    Fry, C; Bishop, S; Brown, B A; Chen, A A; Faestermann, T; Hertenberger, R; Parikh, A; Pérez-Loureiro, D; Wirth, H -F; García, A; Ortez, R

    2015-01-01

    Background: The thermonuclear $^{34g,m}$Cl($p,\\gamma$)$^{35}$Ar reaction rates are unknown due to a lack of experimental nuclear physics data. Uncertainties in these rates translate to uncertainties in $^{34}$S production in models of classical novae on oxygen-neon white dwarfs. $^{34}$S abundances have the potential to aid in the classification of presolar grains. Purpose: Determine resonance energies for the $^{34g,m}$Cl($p,\\gamma$)$^{35}$Ar reactions within the region of astrophyical interest for classical novae to a precision of a few keV as an essential first step toward constraining their thermonuclear reaction rates. Method: $^{35}$Ar excited states were populated by the $^{36}$Ar($d,t$)$^{35}$Ar reaction at $E$(d)=22~MeV and reaction products were momentum analyzed by a high resolution quadrupole-dipole-dipole-dipole (Q3D) magnetic spectrograph. Results: Seventeen new $^{35}$Ar levels have been detected at a statistically significant level in the region $E_x\\approx$~5.9-6.7~MeV ($E_r$ \\textless~800~ k...

  20. Cyclic guanidines as dual 5-HT5A/5-HT7 receptor ligands: optimising brain penetration.

    Science.gov (United States)

    Peters, Jens-Uwe; Lübbers, Thomas; Alanine, Alexander; Kolczewski, Sabine; Blasco, Francesca; Steward, Lucinda

    2008-01-01

    The optimisation of molecular properties within a series of 2-amino dihydroquinazoline 5-HT5A/5-HT7 receptor ligands resulted in a significantly improved brain-to-plasma ratio, enhancing the pharmacological utility of these compounds. By modulating the lipophilicity and pKa, a 20-fold increase in brain-to-plasma ratio could be achieved, leading to micromolar brain concentrations after oral administration. The enantiomers of one representative of this series of improved compounds were separated, and the configuration of the eutomer was determined by X-ray crystallography.

  1. LHS 2803B: A VERY WIDE MID-T DWARF COMPANION TO AN OLD M DWARF IDENTIFIED FROM PAN-STARRS1

    Energy Technology Data Exchange (ETDEWEB)

    Deacon, Niall R. [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Liu, Michael C.; Magnier, Eugene A.; Bowler, Brendan P.; Mann, Andrew W.; Burgett, William S.; Chambers, Ken C.; Kaiser, Nick; Kudritzki, Rolf-Peter; Morgan, Jeff S.; Tonry, John L.; Wainscoat, Richard J. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Redstone, Joshua A. [Facebook, 1601 Willow Road, Menlo Park, CA 94025 (United States); Hodapp, Klaus W. [Institute for Astronomy, University of Hawaii, 640 North Aohoku Place, Hilo, HI 96720 (United States); Price, Paul A., E-mail: deacon@mpia.de [Princeton University Observatory, 4 Ivy Lane, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States)

    2012-09-20

    We report the discovery of a wide ({approx}1400 AU projected separation), common proper motion companion to the nearby M dwarf LHS 2803 (PSO J207.0300-13.7422). This object was discovered during our census of the local T dwarf population using Pan-STARRS1 and Two Micron All Sky Survey data. Using the Infrared Telescope Facility/SpeX near-infrared spectroscopy, we classify the secondary to be spectral type T5.5. University of Hawaii 2.2 m/SuperNova Integral Field Spectrograph optical spectroscopy indicates that the primary has a spectral type of M4.5, with approximately solar metallicity and no measurable H{alpha} emission. We use this lack of activity to set a lower age limit for the system of 3.5 Gyr. Using a comparison with chance alignments of brown dwarfs and nearby stars, we conclude that the two objects are unlikely to be a chance association. The primary's photometric distance of 21 pc and its proper motion implies thin disk kinematics. Based on these kinematics and its metallicity, we set an upper age limit for the system of 10 Gyr. Evolutionary model calculations suggest that the secondary has a mass of 72{+-}{sup 4}{sub 7} M{sub Jup}, temperature of 1120 {+-} 80 K, and log g = 5.4 {+-} 0.1 dex. Model atmosphere fitting to the near-IR spectrum gives similar physical parameters of 1100 K and log g = 5.0.

  2. SDSS DR7 White Dwarf Catalog

    CERN Document Server

    Kleinman, S J; Koester, D; Pelisoli, Ingrid; Peçanha, Viviane; Nitta, A; Costa, J E S; Krzesinski, J; Dufour, P; Lachapelle, F -R; Bergeron, P; Yip, Ching-Wa; Harris, Hugh C; Eisenstein, Daniel J; Althaus, L; Córsico, A

    2012-01-01

    We present a new catalog of spectroscopically-confirmed white dwarf stars from the Sloan Digital Sky Survey Data Release 7 spectroscopic catalog. We find 20,407 white dwarf spectra, representing 19,712 stars, and provide atmospheric model fits to 14,120 DA and 1011 DB white dwarf spectra from 12,843 and 923 stars, respectively. These numbers represent a more than factor of two increase in the total number of white dwarf stars from the previous SDSS white dwarf catalog based on DR4 data. Our distribution of subtypes varies from previous catalogs due to our more conservative, manual classifications of each star in our catalog, supplementing our automatic fits. In particular, we find a large number of magnetic white dwarf stars whose small Zeeman splittings mimic increased Stark broadening that would otherwise result in an overestimated log(g) if fit as a non-magnetic white dwarf. We calculate mean DA and DB masses for our clean, non-magnetic sample and find the DB mean mass is statistically larger than that for...

  3. SDSS DR7 WHITE DWARF CATALOG

    Energy Technology Data Exchange (ETDEWEB)

    Kleinman, S. J.; Nitta, A. [Gemini Observatory, 670 North A' ohoku Place, Hilo, HI 96720 (United States); Kepler, S. O.; Pelisoli, Ingrid; Pecanha, Viviane; Costa, J. E. S. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS (Brazil); Koester, D. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Kiel, D-24098 Kiel (Germany); Krzesinski, J. [Mt. Suhora Observatory, Pedagogical University of Cracow, ul. Podchorazych 2, 30-084 Cracow (Poland); Dufour, P.; Lachapelle, F.-R.; Bergeron, P. [Departement de Physique, Universite de Montreal, C. P. 6128, Succ. Centre-Ville, Montreal, Quebec H3C 3J7 (Canada); Yip, Ching-Wa [Department of Physics and Astronomy, The Johns Hopkins University, 3701 San Martin Drive, Baltimore, MD 21218 (United States); Harris, Hugh C. [United States Naval Observatory, Flagstaff Station, 10391 West Naval Observatory Road, Flagstaff, AZ 86001-8521 (United States); Eisenstein, Daniel J. [Harvard Smithsonian Center for Astrophysics, 60 Garden Street, MS 20, Cambridge, MA 02138 (United States); Althaus, L.; Corsico, A., E-mail: hch@nofs.navy.mil [Facultad de Ciencias Astronomicas y Geofisicas, Paseo del Bosque S/N, (1900) La Plata (Argentina)

    2013-01-15

    We present a new catalog of spectroscopically confirmed white dwarf stars from the Sloan Digital Sky Survey (SDSS) Data Release 7 spectroscopic catalog. We find 20,407 white dwarf spectra, representing 19,712 stars, and provide atmospheric model fits to 14,120 DA and 1011 DB white dwarf spectra from 12,843 and 923 stars, respectively. These numbers represent more than a factor of two increase in the total number of white dwarf stars from the previous SDSS white dwarf catalogs based on DR4 data. Our distribution of subtypes varies from previous catalogs due to our more conservative, manual classifications of each star in our catalog, supplementing our automatic fits. In particular, we find a large number of magnetic white dwarf stars whose small Zeeman splittings mimic increased Stark broadening that would otherwise result in an overestimated log g if fit as a non-magnetic white dwarf. We calculate mean DA and DB masses for our clean, non-magnetic sample and find the DB mean mass is statistically larger than that for the DAs.

  4. White dwarf constraints on a varying $G$

    CERN Document Server

    García-Berro, Enrique; Althaus, Leandro G; Córsico, Alejandro H; Lorén-Aguilar, Pablo; Romero, Alejandra D; Isern, Jordi

    2013-01-01

    A secular variation of $G$ modifies the structure and evolutionary time scales of white dwarfs. Using an state-of-the-art stellar evolutionary code, an up-to-date pulsational code, and a detailed population synthesis code we demonstrate that the effects of a running $G$ are obvious both in the properties of individual white dwarfs, and in those of the white dwarf populations in clusters. Specifically, we show that the white dwarf evolutionary sequences depend on both the value of $\\dot G/G$, and on the value of $G$ when the white dwarf was born. We show as well that the pulsational properties of variable white dwarfs can be used to constrain $\\dot G/G$. Finally, we also show that the ensemble properties of of white dwarfs in clusters can also be used to set upper bounds to $\\dot G/G$. Precisely, the tightest bound --- $\\dot G/G \\sim -1.8 10^{-12}$ yr$^{-1}$ --- is obtained studying the population of the old, metal-rich, well populated, open cluster NGC 6791. Less stringent upper limits can be obtained compari...

  5. The Luminosities of the Coldest Brown Dwarfs

    CERN Document Server

    Tinney, C G; Kirkpatrick, J Davy; Cushing, Mike; Morley, Caroline V; Wright, Edward L

    2014-01-01

    In recent years brown dwarfs have been extended to a new Y-dwarf class with effective temperatures colder than 500K and masses in the range 5-30 Jupiter masses. They fill a crucial gap in observable atmospheric properties between the much colder gas-giant planets of our own Solar System (at around 130K) and both hotter T-type brown dwarfs and the hotter planets that can be imaged orbiting young nearby stars (both with effective temperatures of in the range 1500-1000K). Distance measurements for these objects deliver absolute magnitudes that make critical tests of our understanding of very cool atmospheres. Here we report new distances for nine Y dwarfs and seven very-late T dwarfs. These reveal that Y dwarfs do indeed represent a continuation of the T dwarf sequence to both fainter luminosities and cooler temperatures. They also show that the coolest objects display a large range in absolute magnitude for a given photometric colour. The latest atmospheric models show good agreement with the majority of these ...

  6. Peripheral 5-HT1A and 5-HT7 Serotonergic Receptors Modulate Parasympathetic Neurotransmission in Long-Term Diabetic Rats

    Science.gov (United States)

    Restrepo, Beatriz; Martín, María Luisa; San Román, Luis; Morán, Asunción

    2010-01-01

    We analyzed the modulation of serotonin on the bradycardia induced in vivo by vagal electrical stimulation in alloxan-induced long-term diabetic rats. Bolus intravenous administration of serotonin had a dual effect on the bradycardia induced either by vagal stimulation or exogenous Ach, increasing it at low doses and decreasing it at high doses of 5-hydroxytryptamine (5-HT), effect reproduced by 5-carboxamidotryptamine maleate (5-CT), a 5-HT1/7 agonist. The enhancement of the bradycardia at low doses of 5-CT was reproduced by 5-HT1A agonist 8-hydroxy-2-dipropylaminotetralin hydrobromide (8-OH-DPAT) and abolished by WAY-100,635, 5-HT1A antagonist. Pretreatment with 5-HT1 antagonist methiothepin blocked the stimulatory and inhibitory effect of 5-CT, whereas pimozide, 5-HT7 antagonist, only abolished 5-CT inhibitory action. In conclusion, long-term diabetes elicits changes in the subtype of the 5-HT receptor involved in modulation of vagally induced bradycardia. Activation of the 5-HT1A receptors induces enhancement, whereas attenuation is due to 5-HT7 receptor activation. This 5-HT dual effect occurs at pre- and postjunctional levels. PMID:21403818

  7. Peripheral 5-HT 1A and 5-HT 7 Serotonergic Receptors Modulate Parasympathetic Neurotransmission in Long-Term Diabetic Rats

    Directory of Open Access Journals (Sweden)

    Beatriz Restrepo

    2010-01-01

    Full Text Available We analyzed the modulation of serotonin on the bradycardia induced in vivo by vagal electrical stimulation in alloxan-induced long-term diabetic rats. Bolus intravenous administration of serotonin had a dual effect on the bradycardia induced either by vagal stimulation or exogenous Ach, increasing it at low doses and decreasing it at high doses of 5-hydroxytryptamine (5-HT, effect reproduced by 5-carboxamidotryptamine maleate (5-CT, a 5-HT1/7 agonist. The enhancement of the bradycardia at low doses of 5-CT was reproduced by 5-HT1A agonist 8-hydroxy-2-dipropylaminotetralin hydrobromide (8-OH-DPAT and abolished by WAY-100,635, 5-HT1A antagonist. Pretreatment with 5-HT1 antagonist methiothepin blocked the stimulatory and inhibitory effect of 5-CT, whereas pimozide, 5-HT7 antagonist, only abolished 5-CT inhibitory action. In conclusion, long-term diabetes elicits changes in the subtype of the 5-HT receptor involved in modulation of vagally induced bradycardia. Activation of the 5-HT1A receptors induces enhancement, whereas attenuation is due to 5-HT7 receptor activation. This 5-HT dual effect occurs at pre- and postjunctional levels.

  8. Effects of the 5-HT(4) receptor agonist RS67333 and paroxetine on hippocampal extracellular 5-HT levels

    DEFF Research Database (Denmark)

    Licht, Cecilie Löe; Knudsen, Gitte Moos; Sharp, Trevor

    2010-01-01

    The 5-HT(4) receptor modulates activity of serotonergic neurons and is a new potential target for antidepressant treatment. This microdialysis study evaluated the effect of the 5-HT(4) receptor agonist, RS67333, on extracellular serotonin (5-hydroxytryptamine, 5-HT) and 5-HIAA levels in rat ventral...... on extracellular 5-HT or 5-HIAA levels, while acute paroxetine (0.5mg/kg i.v.) increased 5-HT levels by 299+/-16% and decreased 5-HIAA levels by 25+/-4%. Administration of RS67333 80 min after paroxetine caused an additional transient increase in 5-HT levels (to 398+/-52% of baseline). Subchronic RS67333...... administration (1.5mg/kg i.p.) increased basal 5-HT levels by 73+/-15% and decreased 5-HIAA levels by 27+/-13%. In conclusion, the 5-HT(4) receptor agonist RS67333 augmented the acute effect of paroxetine on extracellular 5-HT levels in the ventral hippocampus, and after 3 days increased basal hippocampal 5-HT...

  9. ENHANCEMENT OF DNA SYNTHESIS IN CULTURED ADULT RAT HEPATOCYTES BY 5-HT THROUGH STIMULATION OF 5-HT2 RECEPTOR

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    Hepatocytes were isolated from livers of adult male Sprague-Dawley rats and cultured in Williams'E Medium with [3 H] thymidine. The effect of 5-hydroxytryptamine (5-HT) was investigated through adding various concentrations (10-8~10-3 mol/L) of 5-HT to the hepatocyte cultures in the presence or absence of epidermal growth factor (EGF) and insulin. The involvement of 5-HT2 receptor was examined by adding a 5-HT2 receptor antagonist, ketanserin (10-6 mol/L), to some of the cultures containing 5-HT. The increment of DNA synthesis was measured by [3 H] thymidine incorporation. The results showed that 5-HT2 (≥10-6 mol/L) significantly (P<0.05) increased the amount of DNA synthesis induced by EGF and insulin in the cultured adult rat hepaptocytes. The effect of 5-HT in enhancing DNA synthesis began to appear at a concentration between 10-7 and 10-6 mol/L and reached maximum at concentrations of ≥10-4 mol/L. The enhancement of DNA synthesis by 5-HT was significantly (P<0.05) antagonized by ketanserin, suggesting that this effect of 5-HT was mediated by 5-HT2 receptor subtype.

  10. The rapid recovery of 5-HT cell firing induced by the antidepressant vortioxetine involves 5-HT(3) receptor antagonism.

    Science.gov (United States)

    Bétry, Cécile; Pehrson, Alan L; Etiévant, Adeline; Ebert, Bjarke; Sánchez, Connie; Haddjeri, Nasser

    2013-06-01

    The therapeutic effect of current antidepressant drugs appears after several weeks of treatment and a significant number of patients do not respond to treatment. Here, we report the effects of the multi-modal antidepressant vortioxetine (Lu AA21004), a 5-HT(3) and 5-HT(7) receptor antagonist, 5-HT(1B) receptor partial agonist, 5-HT(1A) receptor agonist and 5-HT transporter (SERT) inhibitor, on rat 5-HT neurotransmission. Using in vivo electrophysiological recordings in the dorsal raphe nucleus of anaesthetized rats, we assessed the acute and subchronic effects of vortioxetine and/or the selective 5-HT(3) receptor agonist, SR57227 or the selective 5-HT(1A) receptor agonist flesinoxan, on 5-HT neuronal firing activity. Using ex-vivo autoradiography, we correlated SERT occupancy and presumed 5-HT firing activity. The selective serotonin reuptake inhibitor, fluoxetine, was used as comparator. Importantly, the recovery of 5-HT neuronal firing was achieved after 1 d with vortioxetine and 14 d with fluoxetine. SR57227 delayed this recovery. In contrast, vortioxetine failed to alter the reducing action of 3 d treatment of flesinoxan. Acute dosing of vortioxetine inhibited neuronal firing activity more potently than fluoxetine. SR57227 prevented the suppressant effect of vortioxetine, but not of fluoxetine. In contrast, flesinoxan failed to modify the suppressant effect of vortioxetine acutely administered. Differently to fluoxetine, vortioxetine suppressed neuronal firing without saturating occupancy at the SERT. Vortioxetine produced a markedly faster recovery of 5-HT neuronal firing than fluoxetine. This is at least partly due to 5-HT(3) receptor antagonism of vortioxetine in association with its reduced SERT occupancy.

  11. The spectroscopic evolution of the $\\gamma$-ray emitting classical nova Nova Mon 2012. I. Implications for the ONe subclass of classical novae

    CERN Document Server

    Shore, S N; Schwarz, G J; Augusteijn, T; Cheung, C C; Walter, F M; Starrfield, S

    2013-01-01

    Nova Mon 2012 was the first classical nova to be detected as a high energy $\\gamma$-ray transient, by Fermi-LAT, before its optical discovery. We study a time sequence of high resolution optical echelle spectra (Nordic Optical Telescope) and contemporaneous NOT, STIS UV, and CHIRON echelle spectra (Nov 20/21/22). We use [O III] and H$\\beta$ line fluxs to constrain the properties of the ejecta. We derive the structure from the optical and UV line profiles and compare our measured line fluxes for with predictions using Cloudy with abundances from other ONe novae. Mon 2012 is confirmed as an ONe nova. We find E(B-V)=0.85$\\pm$0.05 and hydrogen column density $\\approx 5\\times 10^{21}$ cm$^{-2}$. The corrected continuum luminosity is nearly the same in the entire observed energy range as V1974 Cyg, V382 Mon, and Nova LMC 2000 at the same epoch after outburst. The distance, about 3.6 kpc, is quite similar to V1974 Cyg. The line profiles can be modeled using an axisymmetric bipolar geometry for the ejecta with variou...

  12. Effects of the 5-HT receptor antagonists GR127935 (5-HT1B/1D) and MDL100907 (5-HT2A) in the consolidation of learning.

    Science.gov (United States)

    Meneses, A; Terrón, J A; Hong, E

    1997-12-01

    We have previously reported that 5-HT1B/1D and 5-HT2A/2B/2C receptors play a role in learning and memory. The present investigation was devoted to analyze further in the autoshaping learning task: (1) the effects of the 5-HT1A/1B/1D receptor agonist, GR46611, the 5-HT1B/1D receptor antagonist, GR127935, and the selective 5-HT2A receptor antagonist, MDL100907. Consistent with a role of 5-HT1B/1D receptors in learning, the post-training injection of GR46611 (1-10 mg/kg) decreased the consolidation of learning whereas GR127935 (10 mg/kg) increased it; the effects of both drugs were reversed by PCA pretreatment. GR127935 abolished the decrease induced by GR46611, TFMPP and mCPP, whereas MDL100907 (0.1-3.0 mg/kg) had no effect by itself but abolished the effects of DOI, ketanserin and TFMPP and moderately inhibited the effects elicited by mCPP, 1-NP and mesulergine. Neither did GR127935 nor MDL100907 significantly modify the increase in the consolidation of learning induced by 8-OH-DPAT. Thus, the present findings suggest that stimulation of presynaptic 5-HT1B/1D receptors impairs the consolidation of learning whilst stimulation of 5-HT2A/2C receptors enhances it; the blockade of 5-HT2A receptors has no effects. In addition, 5-HT2 receptors seem to modulate this cognitive stage.

  13. New Light on Dark Stars Red Dwarfs, Low-Mass Stars, Brown Dwarfs

    CERN Document Server

    Reid, I. Neill

    2005-01-01

    There has been very considerable progress in research into low-mass stars, brown dwarfs and extrasolar planets during the past few years, particularly since the fist edtion of this book was published in 2000. In this new edtion the authors present a comprehensive review of both the astrophysical nature of individual red dwarf and brown dwarf stars and their collective statistical properties as an important Galactic stellar population. Chapters dealing with the observational properies of low-mass dwarfs, the stellar mass function and extrasolar planets have been completely revised. Other chapters have been significantly revised and updated as appropriate, including important new material on observational techniques, stellar acivity, the Galactic halo and field star surveys. The authors detail the many discoveries of new brown dwarfs and extrasolar planets made since publication of the first edition of the book and provide a state-of-the-art review of our current knowledge of very low-mass stars, brown dwarfs a...

  14. Ocean and Coastal Acidification off New England and Nova Scotia

    Science.gov (United States)

    New England coastal and adjacent Nova Scotia shelf waters have a reduced buffering capacity because of significant freshwater input, making the region’s waters potentially more vulnerable to coastal acidification. Nutrient loading and heavy precipitation events further acid...

  15. Gamma-ray emission from individual classical novae

    CERN Document Server

    Gómez-Gomar, J; José, J; Isern, J

    1997-01-01

    Classical novae are important producers of radioactive nuclei, such as be7, n13, f18, na22 and al26. The disintegration of these nuclei produces positrons (except for be7) that through annihilation with electrons produce photons of energies 511 keV and below. Furthermore, be7 and na22 decay producing photons with energies of 478 keV and 1275 keV, respectively, well in the gamma-ray domain. Therefore, novae are potential sources of gamma-ray emission. The properties of gamma-ray spectra and gamma-ray light curves (for the continuum and for the lines at 511, 478 and 1275 keV) have been analyzed, with a special emphasis on the difference between carbon-oxygen and oxygen-neon novae. Predictions of detectability of individual novae by the future SPI spectrometer on board the INTEGRAL satellite are made.

  16. Ocean and Coastal Acidification off New England and Nova Scotia

    Science.gov (United States)

    New England coastal and adjacent Nova Scotia shelf waters have a reduced buffering capacity because of significant freshwater input, making the region’s waters potentially more vulnerable to coastal acidification. Nutrient loading and heavy precipitation events further acid...

  17. A Comprehensive Review of Nova-Like Variable Stars

    Science.gov (United States)

    Sion, Edward

    2016-07-01

    A comprehensive review of nova-like variable stars of the VY Sculptoris and UX Ursa Majoris subtypes is presented. All that has been learned, up to the present time, from observations in the X-ray, far ultraviolet, optical and infrared bandpasses will be discussed. Spectroscopic analyses of high optical brightness states and low optical brightness states of nova-like variables will be summarized. The application of standard and non-standard accretion disk models as well as boundary layer structure will be discussed. The results of searches for nova shells, the evolutionary state of nova-likes as well as new spectroscopic results on BZ Cam (the bow shock CV) and BB Dor will also be included. This work is supported by NASA ADP grants NNX13AF12G and NNX13AF11G to Villanova University.

  18. Quark nova inside supernova: Application to GRBs and XROs

    CERN Document Server

    Staff, Jan

    2010-01-01

    In this paper we consider a quark nova occurring inside an exploding star. The quark nova ejecta will shock when interacting with the stellar envelope. When this shock reaches the surface of the star, the energy is radiated away. We suggest that this energy may be seen in X-rays, and show here that this may explain some flares seen in the X-ray afterglow of long gamma ray bursts (GRBs). A quark nova inside an exploding star need not be followed by a GRB, or the GRB may not be beamed towards us. However, the shock breakout is likely not beamed and could be seen even in the absence of a GRB. We suggest that XRO 080109 is such an event in which a quark nova occurs inside an exploding star. No GRB is formed, but the break out of the shock leads to the XRO.

  19. The Gobbling Dwarf that Exploded

    Science.gov (United States)

    2007-07-01

    A unique set of observations, obtained with ESO's VLT, has allowed astronomers to find direct evidence for the material that surrounded a star before it exploded as a Type Ia supernova. This strongly supports the scenario in which the explosion occurred in a system where a white dwarf is fed by a red giant. ESO PR Photo 31a/07 ESO PR Photo 31a/07 Evolution of SN 2006X Spectrum Because Type Ia supernovae are extremely luminous and quite similar to one another, these exploding events have been used extensively as cosmological reference beacons to trace the expansion of the Universe. However, despite significant recent progress, the nature of the stars that explode and the physics that governs these powerful explosions have remained very poorly understood. In the most widely accepted models of Type Ia supernovae the pre-explosion white dwarf star orbits another star. Due to the close interaction and the strong attraction produced by the very compact object, the companion star continuously loses mass, 'feeding' the white dwarf. When the mass of the white dwarf exceeds a critical value, it explodes. The team of astronomers studied in great detail SN 2006X, a Type Ia supernova that exploded 70 million light-years away from us, in the splendid spiral Galaxy Messier 100 (see ESO 08/06). Their observations led them to discover the signatures of matter lost by the normal star, some of which is transferred to the white dwarf. The observations were made with the Ultraviolet and Visual Echelle Spectrograph (UVES), mounted at ESO's 8.2-m Very Large Telescope, on four different occasions, over a time span of four months. A fifth observation at a different time was secured with the Keck telescope in Hawaii. The astronomers also made use of radio data obtained with NRAO's Very Large Array as well as images extracted from the NASA/ESA Hubble Space Telescope archive. ESO PR Photo 31b/07 ESO PR Photo 31b/07 SN 2006X, before and after the Type Ia Supernova explosion "No Type Ia

  20. Dwarf spheroidal galaxies keystones of galaxy evolution

    CERN Document Server

    Gallagher, S C; Gallagher, S; Wyse, F G

    1994-01-01

    Dwarf spheroidal galaxies are the most insignificant extragalactic stellar systems in terms of their visibility, but potentially very significant in terms of their role in the formation and evolution of much more luminous galaxies. We discuss the present observational data and their implications for theories of the formation and evolution of both dwarf and giant galaxies. The putative dark matter content of these low-surface-brightness systems is of particular interest, as is their chemical evolution. Surveys for new dwarf spheroidals hidden behind the stars of our Galaxy and those which are not bound to giant galaxies may give new clues as to the origins of this unique class of galaxy.

  1. Young Brown Dwarfs as Giant Exoplanet Analogs

    CERN Document Server

    Faherty, Jacqueline K; Rice, Emily L; Riedel, Adric

    2013-01-01

    Young brown dwarfs and directly-imaged exoplanets have enticingly similar photometric and spectroscopic characteristics, indicating that their cool, low gravity atmospheres should be studied in concert. Similarities between the peculiar shaped H band, near and mid-IR photometry as well as location on color magnitude diagrams provide important clues about how to extract physical properties of planets from current brown dwarf observations. In this proceeding we discuss systems newly assigned to 10-150 Myr nearby moving groups, highlight the diversity of this uniform age-calibrated brown dwarf sample, and reflect on their implication for understanding current and future planetary data.

  2. AAS Nova and Astrobites: Making current astronomy research accessible

    Science.gov (United States)

    Kohler, Susanna; Astrobites Team

    2016-10-01

    AAS Nova and Astrobites are two resources available for astronomers, astronomy students, and astronomy enthusiasts to keep up with some of the most recent research published across the field of astronomy. Both supported by the AAS, these two daily astrophysical literature blogs provide accessible summaries of recent publications on the arXiv and in AAS journals. We present the goals, content, and readership of AAS Nova and Astrobites, and discuss how they might be used as tools in the undergraduate classroom.

  3. Activity and Kinematics of White Dwarf-M Dwarf Binaries from the SUPERBLINK Proper Motion Survey

    Science.gov (United States)

    Skinner, Julie N.; Morgan, Dylan P.; West, Andrew A.; Lépine, Sébastien; Thorstensen, John R.

    2017-09-01

    We present an activity and kinematic analysis of high proper motion white dwarf-M dwarf binaries (WD+dMs) found in the SUPERBLINK survey, 178 of which are new identifications. To identify WD+dMs, we developed a UV–optical–IR color criterion and conducted a spectroscopic survey to confirm each candidate binary. For the newly identified systems, we fit the two components using model white dwarf spectra and M dwarf template spectra to determine physical parameters. We use Hα chromospheric emission to examine the magnetic activity of the M dwarf in each system, and investigate how its activity is affected by the presence of a white dwarf companion. We find that the fraction of WD+dM binaries with active M dwarfs is significantly higher than their single M dwarf counterparts at early and mid-spectral types. We corroborate previous studies that find high activity fractions at both close and intermediate separations. At more distant separations, the binary fraction appears to approach the activity fraction for single M dwarfs. Using derived radial velocities and the proper motions, we calculate 3D space velocities for the WD+dMs in SUPERBLINK. For the entire SUPERBLINK WD+dMs, we find a large vertical velocity dispersion, indicating a dynamically hotter population compared to high proper motion samples of single M dwarfs. We compare the kinematics for systems with active M dwarfs and those with inactive M dwarfs, and find signatures of asymmetric drift in the inactive sample, indicating that they are drawn from an older population. Based on observations obtained at the MDM Observatory operated by Dartmouth College, Columbia University, The Ohio State University, and the University of Michigan.

  4. HT-ATTENDING: Critiquing the Pharmacologic Management of Essential Hypertension

    OpenAIRE

    Miller, Perry L.; Black, Henry R.

    1983-01-01

    HT-ATTENDING is a computer system being developed to critique a physician's approach to the pharmacologic management of essential hypertension. The concept of having a computer critique a physician's plan of management (Medical Plan-Analysis) has already been implemented in ATTENDING, a system whose domain is anesthesia management. HT-ATTENDING extends this approach to a new medical domain. HT-ATTENDING's goal is 1) to assist a physician in formulating his approach to the hypertensive patient...

  5. Epiminocyclohepta[b]indole analogs as 5-HT6 antagonists

    DEFF Research Database (Denmark)

    Henderson, Alan J; Guzzo, Peter R; Ghosh, Animesh;

    2012-01-01

    A new series of epiminocyclohepta[b]indoles with potent 5-HT(6) antagonist activity were discovered and optimized using in vitro protocols. One compound from this series was progressed to advanced pharmacokinetic (PK) studies followed by 5-HT(6) receptor occupancy studies. The compound was found...... to have excellent oral absorption, a highly favorable PK profile and demonstrated pharmacodynamic interaction with the 5-HT(6) receptor as shown by ex vivo autoradiography....

  6. The serotonin 5-HT3 receptor: a novel neurodevelopmental target

    Directory of Open Access Journals (Sweden)

    Mareen eEngel

    2013-05-01

    Full Text Available Serotonin (5-HT, next to being an important neurotransmitter, recently gained attention as a key regulator of pre- and postnatal development in the mammalian central nervous system (CNS. Several receptors for 5-HT are expressed in the developing brain including a ligand-gated ion channel, the 5-HT3 receptor. Over the past years, evidence has been accumulating that 5-HT3 receptors are involved in the regulation of neurodevelopment by serotonin.Here, we review the spatial and temporal expression patterns of 5-HT3 receptors in the pre- and early postnatal rodent brain and its functional implications. First, 5-HT3 receptors are expressed on GABAergic interneurons in neocortex and limbic structures derived from the caudal ganglionic eminence. Mature inhibitory GABAergic interneurons fine-tune neuronal excitability and thus are crucial for the physiological function of the brain. Second, 5-HT3 receptors are expressed on specific glutamatergic neurons, Cajal-Retzius cells in the cortex and granule cells in the cerebellum, where they regulate morphology, positioning and connectivity of the local microcircuitry. Taken together, the 5-HT3 receptor emerges as a potential key-regulator of network formation and function in the CNS, which could have a major impact on our understanding of neurodevelopmental disorders in which 5-HT plays a role.

  7. FORMATION OF ULTRA-COMPACT BLUE DWARF GALAXIES AND THEIR EVOLUTION INTO NUCLEATED DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Bekki, Kenji [ICRAR, M468, The University of Western Australia 35 Stirling Highway, Crawley Western Australia, 6009 (Australia)

    2015-10-10

    We propose that there is an evolutionary link between ultra-compact blue dwarf galaxies (UCBDs) with active star formation and nucleated dwarfs based on the results of numerical simulations of dwarf–dwarf merging. We consider the observational fact that low-mass dwarfs can be very gas-rich, and thereby investigate the dynamical and chemical evolution of very gas-rich, dissipative dwarf–dwarf mergers. We find that the remnants of dwarf–dwarf mergers can be dominated by new stellar populations formed from the triggered starbursts and consequently can have blue colors and higher metallicities (Z ∼ [0.2–1]Z{sub ⊙}). We also find that the remnants of these mergers can have rather high mass densities (10{sup 4} M{sub ⊙} pc{sup −3}) within the central 10 pc and small half-light radii (40−100 pc). The radial stellar structures of some merger remnants are similar to those of nucleated dwarfs. Star formation can continue in nuclear gas disks (R < 100 pc) surrounding stellar galactic nuclei (SGNs) so that the SGNs can finally have multiple stellar populations with different ages and metallicities. These very compact blue remnants can be identified as UCBDs soon after merging and as nucleated dwarfs after the young stars fade. We discuss these results in the context of the origins of metal-rich ultra-compact dwarfs and SGNs.

  8. A phenomenological model for the X-ray spectrum of Nova V2491 Cygni

    CERN Document Server

    Pinto, Ciro; Verbunt, Frank; Kaastra, Jelle S; Costantini, Elisa; Detmers, Rob G

    2012-01-01

    The X-ray flux of Nova V2491 Cyg reached a maximum some forty days after optical maximum. The X-ray spectrum at that time, obtained with the RGS of XMM-Newton, shows deep, blue-shifted absorption by ions of a wide range of ionization. We show that the deep absorption lines of the X-ray spectrum at maximum, and nine days later, are well described by the following phenomenological model with emission from a central blackbody and from a collisionally ionized plasma (CIE). The blackbody spectrum (BB) is absorbed by three main highly-ionized expanding shells; the CIE and BB are absorbed by cold circumstellar and interstellar matter that includes dust. The outflow density does not decrease monotonically with distance. The abundances of the shells indicate that they were ejected from an O-Ne white dwarf. We show that the variations on time scales of hours in the X-ray spectrum are caused by a combination of variation in the central source and in the column density of the ionized shells. Our phenomenological model gi...

  9. The Curious Case of ASAS J174600-2321.3: an Eclipsing Symbiotic Nova in Outburst?

    CERN Document Server

    Huemmerich, Stefan; Tisserand, Patrick; Bernhard, Klaus

    2015-01-01

    The star ASAS J174600-2321.3 was found to exhibit peculiar photometric variability (conspicuous brightening of about 4 magnitudes (V), fast luminosity declines, intrinsic pulsations). It was rejected as an RCB candidate in recent investigations on spectroscopic grounds. We have collected and present all available data from public sky surveys, photometric catalogues, and the literature. From an analysis of these data, we have identified ASAS J174600-2321.3 as a long-period eclipsing binary (Porb = 1011.5 days). The primary star, which is probably a white dwarf, is currently in outburst and exhibits the spectral characteristics of a reddened, early F-type supergiant; the secondary star is a giant of spectral type late M. We discuss the possible origin of the observed brightening, which is related to the primary component. ASAS J174600-2321.3 is most certainly an eclipsing symbiotic binary - probably a symbiotic nova of GCVS type NC - that is currently in outburst. However, further photometric and spectroscopic ...

  10. Active phases and flickering of a symbiotic recurrent nova T CrB

    CERN Document Server

    Ilkiewicz, Krystian; Stoyanov, Kiril; Manousakis, Antonios; Miszalski, Brent

    2016-01-01

    T CrB is a symbiotic recurrent nova known to exhibit active phases, characterised by apparent increases in the hot component temperature and the appearance of flickering, i.e. changes in the observed flux on the time-scale of minutes. Historical UV observations have ruled out orbital variability as an explanation for flickering and instead suggest flickering is caused by variable mass transfer. We have analysed optical and X-ray observations to investigate the nature of the flickering as well as the active phases in T CrB. The spectroscopic and photometric observations confirm that the active phases follow two periods of ~1000d and ~5000d. Flickering in the X-rays is detected and follows an amplitude-flux relationship similar to that observed in the optical. The flickering is most prominent at harder X-ray energies, suggesting that it originates in the boundary layer between the accretion disc and the white dwarf. The X-ray radiation from the boundary layer is then reprocessed by a thick accretion disc or a n...

  11. Assisted stellar suicide the wind-driven evolution of the recurrent nova T Pyxidis

    CERN Document Server

    Knigge, C; Patterson, J

    2000-01-01

    We show that the extremely high luminosity of the short-period recurrent nova T Pyx in quiescence can be understood if this system is a wind-driven supersoft x-ray source (SSS). In this scenario, a strong, radiation-induced wind is excited from the secondary star and accelerates the binary evolution. The accretion rate is therefore much higher than in an ordinary cataclysmic binary at the same orbital period, as is the luminosity of the white dwarf primary. In the steady state, the enhanced luminosity is just sufficient to maintain the wind from the secondary. The accretion rate and luminosity predicted by the wind-driven model for T Pyx are in good agreement with the observational evidence. X-ray observations with Chandra or XMM may be able to confirm T Pyx's status as a SSS. T Pyx's lifetime in the wind-driven state is on the order of a million years. Its ultimate fate is not certain, but the system may very well end up destroying itself, either via the complete evaporation of the secondary star, or in a Ty...

  12. Ultraviolet spectroscopy of symbiotic nova V1016 Cyg with IUE and HST

    Science.gov (United States)

    Sanad, M. R.

    2017-04-01

    We present International Ultraviolet Explorer (IUE) & Hubble Space Telescope Space Telescope Imaging Spectrograph (HST STIS) observations of the symbiotic nova V1016 Cyg through the period 1978 - 2000. Four spectra at different times revealing the changes in line fluxes are presented. The outflow velocity of the emitting region was calculated to be 900-2000 km s-1 (FWHM). The reddening of V1016 Cyg was determined from 2200 Å absorption feature to be E (B-V) = 0.36 ± 0.02. We calculated the fluxes of CIV 1550 Å & CIII] 1909 Å emission lines produced in a stellar wind from the hot white dwarf. We determined the average wind mass loss rate to be ∼2.3 × 10-6 M⊙, the average temperature of the emitting region to be ∼1.3 × 105 K, and an average ultraviolet luminosity to be ∼2 × 1035 erg s-1. The results show that there are modulations of line fluxes with time. We attributed these spectral modulations to the changes of density and temperature in the emitting region as a result of the variable stellar wind.

  13. Magnetars and white dwarf pulsars

    Science.gov (United States)

    Lobato, Ronaldo V.; Malheiro, Manuel; Coelho, Jaziel G.

    2016-07-01

    The anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) are a class of pulsars understood as neutron stars (NSs) with super strong surface magnetic fields, namely B ≳ 1014G, and for that reason are known as magnetars. However, in the last years, some SGRs/AXPs with low surface magnetic fields B ˜ (1012-1013)G have been detected, challenging the magnetar description. Moreover, some fast and very magnetic white dwarfs (WDs) have also been observed, and at least one showed X-ray energy emission as an ordinary pulsar. Following this fact, an alternative model based on WDs pulsars has been proposed to explain this special class of pulsars. In this model, AXPs and SGRs as dense and magnetized WDs can have surface magnetic field B ˜ 107-1010 G and rotate very fast with frequencies Ω ˜ 1rad/s, consistent with the observed rotation periods P ˜ (2-12)s.

  14. Dyson Spheres around White Dwarfs

    CERN Document Server

    Semiz, İbrahim

    2015-01-01

    A Dyson Sphere is a hypothetical structure that an advanced civilization might build around a star to intercept all of the star's light for its energy needs. One usually thinks of it as a spherical shell about one astronomical unit (AU) in radius, and surrounding a more or less Sun-like star; and might be detectable as an infrared point source. We point out that Dyson Spheres could also be built around white dwarfs. This type would avoid the need for artificial gravity technology, in contrast to the AU-scale Dyson Spheres. In fact, we show that parameters can be found to build Dyson Spheres suitable --temperature- and gravity-wise-- for human habitation. This type would be much harder to detect.

  15. Pluto: Planet or "Dwarf Planet"?

    Science.gov (United States)

    Voelzke, M. R.; de Araújo, M. S. T.

    2010-09-01

    In August 2006 during the XXVI General Assembly of the International Astronomical Union (IAU), taken place in Prague, Czech Republic, new parameters to define a planet were established. According to this new definition Pluto will be no more the ninth planet of the Solar System but it will be changed to be a "dwarf planet". This reclassification of Pluto by the academic community clearly illustrates how dynamic science is and how knowledge of different areas can be changed and evolves through the time, allowing to perceive Science as a human construction in a constant transformation, subject to political, social and historical contexts. These epistemological characteristics of Science and, in this case, of Astronomy, constitute important elements to be discussed in the lessons, so that this work contributes to enable Science and Physics teachers who perform a basic education to be always up to date on this important astronomical fact and, thereby, carry useful information to their teaching.

  16. The accretion of solar material onto white dwarfs: No mixing with core material implies that the mass of the white dwarf is increasing

    Directory of Open Access Journals (Sweden)

    Sumner Starrfield

    2014-02-01

    Full Text Available Cataclysmic Variables (CVs are close binary star systems with one component a white dwarf (WD and the other a larger cooler star that fills its Roche Lobe. The cooler star is losing mass through the inner Lagrangian point of the binary and some unknown fraction of this material is accreted by the WD. One consequence of the WDs accreting material, is the possibility that they are growing in mass and will eventually reach the Chandrasekhar Limit. This evolution could result in a Supernova Ia (SN Ia explosion and is designated the Single Degenerate Progenitor (SD scenario. This paper is concerned with the SD scenario for SN Ia progenitors. One problem with the single degenerate scenario is that it is generally assumed that the accreting material mixes with WD core material at some time during the accretion phase of evolution and, since the typical WD has a carbon-oxygen CO core, the mixing results in large amounts of carbon and oxygen being brought up into the accreted layers. The presence of enriched carbon causes enhanced nuclear fusion and a Classical Nova explosion. Both observations and theoretical studies of these explosions imply that more mass is ejected than is accreted. Thus, the WD in a Classical Nova system is losing mass and cannot be a SN Ia progenitor. However, the composition in the nuclear burning region is important and, in new calculations reported here, the consequences to the WD of no mixing of accreted material with core material have been investigated so that the material involved in the explosion has only a Solar composition. WDs with a large range in initial masses and mass accretion rates have been evolved. I find that once sufficient material has been accreted, nuclear burning occurs in all evolutionary sequences and continues until a thermonuclear runaway (TNR occurs and the WD either ejects a small amount of material or its radius grows to about 1012 cm and the evolution is ended. In all cases where mass ejection occurs

  17. Another neon nova - Early infrared photometry and spectroscopy of Nova Cygni 1992

    Science.gov (United States)

    Hayward, T. L.; Gehrz, R. D.; Miles, J. W.; Houck, J. R.

    1992-01-01

    Infrared photometry and spectrophotometry of Nova Cygni 1992 taken within 54 days of its eruption show a strong 12.8-micron Ne II forbidden emission line as well as hydrogen recombination lines. Spectra with lambda/Delta lambda of about 2000 resolve the Ne II forbidden and 12.37-micron Hu-alpha lines with about 2200 km/s (FWHM). The Ne II forbidden line shows multiple velocity components. The amount of forbidden Ne II required to produce the observed emission feature exceeds the solar abundance of neon by at least a factor of 4.

  18. Inflammation and peripheral 5-HT7 receptors: the role of 5-HT7 receptors in carrageenan induced inflammation in rats.

    Science.gov (United States)

    Albayrak, Abdulmecit; Halici, Zekai; Cadirci, Elif; Polat, Beyzagul; Karakus, Emre; Bayir, Yasin; Unal, Deniz; Atasoy, Mustafa; Dogrul, Ahmet

    2013-09-05

    The aim of this study was: (1) to investigate possible role for 5-HT7 receptors in carrageenan induced inflammatory paw oedema in rats; (2) to determine the presence of 5-HT7 receptors in rat paw tissue; (3) to observe the effects of 5-HT7 receptor agonist and antagonist administration on inflammation; and (4) to determine a unique mechanism for inflammatory processes via 5-HT7 receptors. Effects of 5-HT7 receptor agonist, antagonist and indomethacin were investigated in carrageenan induced paw oedema in rats. Blood and tissue samples were collected and evaluated biochemically for serum cytokine levels, tissue oxidant-antioxidant balance and histopathologically for inflammatory cell accumulation. We performed Real Time PCR analyses for tissue 5-HT7 receptor and COX mRNA expressions. The 5-HT7 receptor agonist AS-19 exerted significant anti-inflammatory effect both alone and in combination with indomethacin. Antagonist, SB269970, did not affect inflammation alone but decreased the effects of agonist when co-administered. 5-HT7 mRNA levels were higher in the carrageenan group than healthy control. Carrageenan+indometacin group decreased the mRNA expression of 5-HT7 when compared to carrageenan group. While agonist administration decreased 5-HT7 mRNA expression when compared to carrageenan group. Agonist decreased paw COX expression. Agonist also decreased serum cytokine levels and tissue oxidative stress. In conclusion, this study demonstrated for the first time that 5-HT7 receptors are expressed in rat paw tissue and that this expression responds to inflammatory stimuli. The 5-HT7 receptor may be a promising new therapeutic target for prevention of inflammation and inflammatory disorders and may also provide a new glimpse into inflammation pathophysiology.

  19. Shuyu Capsules Relieve Premenstrual Syndrome Depression by Reducing 5-HT3AR and 5-HT3BR Expression in the Rat Brain

    Science.gov (United States)

    Li, Fang; Feng, Jizhen; Gao, Dongmei; Wang, Jieqiong; Song, Chunhong; Wei, Sheng

    2016-01-01

    The effects of the Shuyu capsule on 5-HT3AR and 5-HT3BR expression in a rat model of premenstrual syndrome (PMS) depression and on 5-HT3AR and 5-HT3BR expression and hippocampal neuron 5-HT3 channel current were investigated, to elucidate its mechanism of action against PMS depression. PMS depression model rats were divided into depression and Shuyu- and fluoxetine-treated groups, which were compared to control rats for frontal lobe and hippocampal 5-HT3AR and 5-HT3BR expression and behavior. The depressed model rats displayed symptoms of depression, which were reduced in treated and normal control rats. Frontal lobe and hippocampal 5-HT3AR and 5-HT3BR levels were significantly higher in the model versus the control group and were significantly lower in the Shuyu group. As compared to control rats, the 5-HT3R channel current in the model group was significantly higher; the 5-HT3R channel current in hippocampal neurons treated with serum from Shuyu group rats was significantly lower than that in those treated with model group serum. Thus, PMS depression may be related to 5-HT3AR and 5-HT3BR expression and increased 5-HT3 channel current. Shuyu capsules rectified abnormal 5-HT3AR and 5-HT3BR expression and 5-HT3 channel current changes in a rat model; this finding may provide insight into treating PMS depression.

  20. Shell Galaxies, Dynamical Friction, and Dwarf Disruption

    CERN Document Server

    Ebrova, Ivana; Canalizo, Gabriela; Bennert, Nicola; Jilkova, Lucie

    2009-01-01

    Using N-body simulations of shell galaxies created in nearly radial minor mergers, we investigate the error of collision dating, resulting from the neglect of dynamical friction and of gradual disruption of the cannibalized dwarf.

  1. Merging White Dwarfs and Thermonuclear Supernovae

    CERN Document Server

    van Kerkwijk, Marten H

    2012-01-01

    Thermonuclear supernovae result when interaction with a companion reignites nuclear fusion in a carbon-oxygen white dwarf, causing a thermonuclear runaway, a catastrophic gain in pressure, and the disintegration of the whole white dwarf. It is usually thought that fusion is reignited in near-pycnonuclear conditions when the white dwarf approaches the Chandrasekhar mass. I briefly describe two long-standing problems faced by this scenario, and our suggestion that these supernovae instead result from mergers of carbon-oxygen white dwarfs, including those that produce sub-Chandrasekhar mass remnants. I then turn to possible observational tests, in particular those that test the absence or presence of electron captures during the burning.

  2. Magnetic white dwarfs with debris disks

    CERN Document Server

    Külebi, Baybars; Lorén-Aguilar, Pablo; Isern, Jordi; García-Berro, Enrique

    2012-01-01

    It has long been accepted that a possible mechanism for explaining the existence of magnetic white dwarfs is the merger of a binary white dwarf system, as there are viable mechanisms for producing sustainable magnetism within the merger product. However, the lack of rapid rotators in the magnetic white dwarf population has been always considered a problematic issue of this scenario. In order to explain this discrepancy we build a model in which the interaction between the magnetosphere of the star and the disk induces angular momentum transfer. Our model predicts that the magnetospheric interaction of magnetic white dwarfs with their disks results in a significant spin down, and we show that the observed rotation period of REJ 0317-853, which is suggested to be a product of a double degenerate merger, can be reproduced.

  3. Building Magnetic Fields in White Dwarfs

    Science.gov (United States)

    Kohler, Susanna

    2017-03-01

    White dwarfs, the compact remnants left over at the end of low- and medium-mass stars lifetimes, are often found to have magnetic fields with strengths ranging from thousands to billions of times that of Earth. But how do these fields form?MultiplePossibilitiesAround 1020% of white dwarfs have been observed to have measurable magnetic fields with a wide range of strengths. There are several theories as to how these fields might be generated:The fields are fossil.The original weak magnetic fields of the progenitor stars were amplified as the stars cores evolved into white dwarfs.The fields are caused by binary interactions.White dwarfs that formed in the merger of a binary pair might have had a magnetic field amplified as a result of a dynamo that was generated during the merger.The fields were produced by some other internal physical mechanism during the cooling of the white dwarf itself.In a recent publication, a team of authors led by Jordi Isern (Institute of Space Sciences, CSIC, and Institute for Space Studies of Catalonia, Spain) explored this third possibility.Dynamos from CrystallizationThe inner and outer boundaries of the convective mantle of carbon/oxygen white dwarfs of two different masses (top vs. bottom panel) as a function of luminosity. As the white dwarf cools (toward the right), the mantle grows thinner due to the crystallization and settling of material. [Isern et al. 2017]As white dwarfs have no nuclear fusion at their centers, they simply radiate heat and gradually cool over time. The structure of the white dwarf undergoes an interesting change as it cools, however: though the object begins as a fluid composed primarily of an ionized mixture of carbon and oxygen (and a few minor species like nickel and iron), it gradually crystallizes as its temperature drops.The crystallized phase of the white dwarf is oxygen-rich which is denser than the liquid, so the crystallized material sinks to the center of the dwarf as it solidifies. As a result, the

  4. Giant planet and brown dwarf formation

    CERN Document Server

    Chabrier, G; Janson, M; Rafikov, R

    2014-01-01

    Understanding the dominant brown dwarf and giant planet formation processes, and finding out whether these processes rely on completely different mechanisms or share common channels represents one of the major challenges of astronomy and remains the subject of heated debates. It is the aim of this review to summarize the latest developments in this field and to address the issue of origin by confronting different brown dwarf and giant planet formation scenarios to presently available observational constraints. As examined in the review, if objects are classified as "Brown Dwarfs" or "Giant Planets" on the basis of their formation mechanism, it has now become clear that their mass domains overlap and that there is no mass limit between these two distinct populations. Furthermore, while there is increasing observational evidence for the existence of non-deuterium burning brown dwarfs, some giant planets, characterized by a significantly metal enriched composition, might be massive enough to ignite deuterium bur...

  5. White Dwarfs, Neutron Stars and Black Holes

    Science.gov (United States)

    Szekeres, P.

    1977-01-01

    The three possible fates of burned-out stars: white dwarfs, neutron stars and black holes, are described in elementary terms. Characteristics of these celestial bodies, as provided by Einstein's work, are described. (CP)

  6. Pulsating White Dwarf Stars and Precision Asteroseismology

    CERN Document Server

    Winget, D E

    2008-01-01

    Galactic history is written in the white dwarf stars. Their surface properties hint at interiors composed of matter under extreme conditions. In the forty years since their discovery, pulsating white dwarf stars have moved from side-show curiosities to center stage as important tools for unraveling the deep mysteries of the Universe. Innovative observational techniques and theoretical modeling tools have breathed life into precision asteroseismology. We are just learning to use this powerful tool, confronting theoretical models with observed frequencies and their time rate-of-change. With this tool, we calibrate white dwarf cosmochronology; we explore equations of state; we measure stellar masses, rotation rates, and nuclear reaction rates; we explore the physics of interior crystallization; we study the structure of the progenitors of Type Ia supernovae, and we test models of dark matter. The white dwarf pulsations are at once the heartbeat of galactic history and a window into unexplored and exotic physics.

  7. Pulsating White Dwarf Stars and Precision Asteroseismology

    Science.gov (United States)

    Winget, D. E.; Kepler, S. O.

    2008-09-01

    Galactic history is written in the white dwarf stars. Their surface properties hint at interiors composed of matter under extreme conditions. In the forty years since their discovery, pulsating white dwarf stars have moved from side-show curiosities to center stage as important tools for unraveling the deep mysteries of the Universe. Innovative observational techniques and theoretical modeling tools have breathed life into precision asteroseismology. We are just learning to use this powerful tool, confronting theoretical models with observed frequencies and their time rate-of-change. With this tool, we calibrate white dwarf cosmochronology; we explore equations of state; we measure stellar masses, rotation rates, and nuclear reaction rates; we explore the physics of interior crystallization; we study the structure of the progenitors of Type Ia supernovae, and we test models of dark matter. The white dwarf pulsations are at once the heartbeat of galactic history and a window into unexplored and exotic physics.

  8. Carnaval da Nova Consciência

    Directory of Open Access Journals (Sweden)

    Elisete Schwade

    2011-06-01

    Full Text Available Neste artigo faço uma descrição etnográfica do "Encontro Para a Nova Consciência" - ENC, que acontece anualmente em Campina Grande-PB, no período do carnaval, desde 1992. Um evento que promove o contato inter-religioso, ao mesmo tempo em que divulga uma "leitura" de realidades com conotação terapêutica. Propõe o diálogo de práticas religiosas com temas de amplo interesse na atualidade, tais como tolerância, paz, diversidade, questões ambientais, entre outros. Um espaço aberto que incorpora a cada edição novos diálogos, o que contribui para sua permanência. O texto sublinha interações e diálogos entre atores no ENC, por meio de referências associadas à religiosidade, enquanto vivência e partilha, num horizonte de produção e difusão de práticas e conteúdos que ganham expressividade pelo reconhecimento coletivo.

  9. 5-HT reuptake inhibitors with 5-HT(1B/1D) antagonistic activity: a new approach toward efficient antidepressants.

    Science.gov (United States)

    Matzen, L; van Amsterdam, C; Rautenberg, W; Greiner, H E; Harting, J; Seyfried, C A; Böttcher, H

    2000-03-23

    As part of our research program toward new, potential antidepressants, a series of unsymmetrical ureas has been prepared and evaluated as 5-HT reuptake inhibitors with 5-HT(1B/1D) antagonistic activities. The design of these compounds was based on coupling of various indole derivatives, previously shown to inhibit 5-HT reuptake, to three different aniline moieties, which are part of known 5-HT(1B/1D) ligands. Binding experiments in rat frontal cortex using [(125)I]iodocyanopindolol, in calf striatum using [(3)H]5-HT, and in rat hippocampus using [(3)H]8-OH-DPAT as radioligands, respectively, revealed significantly higher affinity at the 5-HT(1B) receptor as compared to the affinities for the 5-HT(1A) and 5-HT(1D) receptors for a number of compounds, among them 4-(5-fluoro-1H-indol-3-yl)piperidine-1-carboxylic acid [4-methoxy-3-(4-methylpiperazin-1-yl)phenyl]amide (5), the corresponding 4-fluoro-1H-indol-3-yl analogue 21a, and the corresponding 6-fluoro-1H-indol-3-yl analogue 21b. Conformational restriction of the aniline moiety in 5 only slightly enhanced the 5-HT(1B) affinity, whereas introduction of an aniline moiety with higher conformational flexibility resulted in a less potent 5-HT(1B) receptor ligand as compared to 5. The functional 5-HT(1B/1D) antagonistic activity was investigated using the rabbit saphenous vein model as well as the [(3)H]5-HT release from guinea pig cortical slices. All new compounds tested in the rabbit saphenous vein model were shown to antagonize the sumatriptan-evoked contractile responses with pA(2) values ranging from 7.3 to 8.7. These observations were consistent with the results of the cortical slice model, in which the ureas were found to block the sumatriptan-induced inhibition of potassium-evoked [(3)H]5-HT release. The 5-HT reuptake inhibition of the ureas determined in rat brain synaptosomes was found to be either increased or decreased as compared to the uncoupled indole derivatives indicating that the reuptake inhibition

  10. Cellular resilience: 5-HT neurons in Tph2(-/-) mice retain normal firing behavior despite the lack of brain 5-HT.

    Science.gov (United States)

    Montalbano, Alberto; Waider, Jonas; Barbieri, Mario; Baytas, Ozan; Lesch, Klaus-Peter; Corradetti, Renato; Mlinar, Boris

    2015-11-01

    Considerable evidence links dysfunction of serotonin (5-hydroxytryptamine, 5-HT) transmission to neurodevelopmental and psychiatric disorders characterized by compromised "social" cognition and emotion regulation. It is well established that the brain 5-HT system is under autoregulatory control by its principal transmitter 5-HT via its effects on activity and expression of 5-HT system-related proteins. To examine whether 5-HT itself also has a crucial role in the acquisition and maintenance of characteristic rhythmic firing of 5-HT neurons, we compared their intrinsic electrophysiological properties in mice lacking brain 5-HT, i.e. tryptophan hydroxylase-2 null mice (Tph2(-/-)) and their littermates, Tph2(+/-) and Tph2(+/+), by using whole-cell patch-clamp recordings in a brainstem slice preparation and single unit recording in anesthetized animals. We report that the active properties of dorsal raphe nucleus (DRN) 5-HT neurons in vivo (firing rate magnitude and variability; the presence of spike doublets) and in vitro (firing in response to depolarizing current pulses; action potential shape) as well as the resting membrane potential remained essentially unchanged across Tph2 genotypes. However, there were subtle differences in subthreshold properties, most notably, an approximately 25% higher input conductance in Tph2(-/-) mice compared with Tph2(+/-) and Tph2(+/+) littermates (presilience to complete brain 5-HT deficiency.

  11. Fabrication of P3HT/gold nanoparticle LB films by P3HT templating Langmuir monolayer

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Liang-Huei [Department of Medicinal Chemistry, Chia-Nan University of Pharmacy and Science, Tainan, Taiwan (China); Hsu, Wen-Ping, E-mail: mjkr.hsu@msa.hinet.net [Department of Chemical Engineering, National United University, Miao-Li, Taiwan 36063 (China); Chan, Han-Wen [Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan 70101 (China); Lee, Yuh-Lang, E-mail: yllee@mail.ncku.edu.tw [Department of Chemical Engineering, National Cheng Kung University, Tainan, Taiwan 70101 (China)

    2014-11-30

    Highlights: • Addition of ODA into the P3HT monolayer can significantly improve the dispersion ability of P3HT molecules. • The adsorption ability of the P3HT monolayer to the dispersed AuNPs can also be enhanced by the presence of ODA. - Abstract: Regioregular poly(3-hexyl thiophene) (rr-P3HT) and mixed P3HT/octadecyl amine (ODA) were used as template monolayers to adsorb the gold nanoparticles (AuNPs) dispersed in subphase. The behaviors of P3HT and P3HT/ODA monolayers were investigated by surface pressure area per molecule (π–A) isotherms, transmission electron microscopy (TEM) and atomic force microscopy (AFM). The experimental results show that P3HT does not form a homogeneous film and tends to aggregate at the air/water interface. Meanwhile, the amount of AuNPs adsorbed by the P3HT monolayers is low, attributable to the weak interaction between AuNPs and P3HT. By introduction of ODA molecules into the P3HT monolayer, the spreading of P3HT molecules at the air/water interface is improved and the aggregation of P3HT is significantly inhibited. A nearly uniform and homogeneously mixed P3HT/ODA monolayer can be obtained when 50% of ODA is introduced. It is also found that the introduction of ODA can significantly increase the adsorption of AuNPs. For the mixed monolayer with low ratio of ODA (P3HT/ODA = 1/0.2), a higher concentration of adsorbed AuNPs was observed on the corresponding monolayer. However, when the ODA/P3HT ratio increases to 1/1, the AuNPs tend to form three-dimensional (3D) aggregates and the AuNPs cannot distribute well as a homogeneous monolayer. This result is ascribed to the increasing hydrophobicity of the adsorbed AuNPs because of capping of more ODA molecules.

  12. Identifying Dwarfs Workloads in Big Data Analytics

    OpenAIRE

    Gao, Wanling; Luo, Chunjie; Zhan, Jianfeng; Ye, Hainan; He, Xiwen; Wang, Lei; Zhu, Yuqing; Tian, Xinhui

    2015-01-01

    Big data benchmarking is particularly important and provides applicable yardsticks for evaluating booming big data systems. However, wide coverage and great complexity of big data computing impose big challenges on big data benchmarking. How can we construct a benchmark suite using a minimum set of units of computation to represent diversity of big data analytics workloads? Big data dwarfs are abstractions of extracting frequently appearing operations in big data computing. One dwarf represen...

  13. Abundance analysis of DAZ white dwarfs

    CERN Document Server

    Kawka, Adela; Dinnbier, Frantisek; Cibulkova, Helena; Nemeth, Peter

    2010-01-01

    We present an abundance analysis of a sample of 33 hydrogen-rich (DA) white dwarfs. We have used archival high-resolution spectra to measure abundances of calcium, magnesium and iron in a set of 30 objects. In addition, we present preliminary calcium abundances in three new white dwarfs based on low-dispersion spectra. We investigate some abundance ratios (Mg/Ca, Fe/Ca) that may help uncover the composition of the accretion source.

  14. Morphological transformations of Dwarf Galaxies in the Local Group

    CERN Document Server

    Carraro, Giovanni

    2014-01-01

    In the Local Group there are three main types of dwarf galaxies: Dwarf Irregulars, Dwarf Spheroidals, and Dwarf Ellipticals. Intermediate/transitional types are present as well. This contribution reviews the idea that the present day variety of dwarf galaxy morphologies in the Local Group might reveal the existence of a transformation chain of events, of which any particular dwarf galaxy represents a manifestation of a particular stage. In other words, all dwarf galaxies that now are part of the Local Group would have formed identically in the early universe, but then evolved differently because of morphological transformations induced by dynamical processes like galaxy harassment, ram pressure stripping, photo-evaporation, and so forth. We start describing the population of dwarf galaxies and their spatial distribution in the LG. Then, we describe those phenomena that can alter the morphology of a dwarf galaxies, essentially by removing, partially or completely, their gas content. Lastly, we discuss morpholo...

  15. A radio pulsing white dwarf binary star

    CERN Document Server

    Marsh, T R; Hümmerich, S; Hambsch, F -J; Bernhard, K; Lloyd, C; Breedt, E; Stanway, E R; Steeghs, D T; Parsons, S G; Toloza, O; Schreiber, M R; Jonker, P G; van Roestel, J; Kupfer, T; Pala, A F; Dhillon, V S; Hardy, L K; Littlefair, S P; Aungwerojwit, A; Arjyotha, S; Koester, D; Bochinski, J J; Haswell, C A; Frank, P; Wheatley, P J

    2016-01-01

    White dwarfs are compact stars, similar in size to Earth but ~200,000 times more massive. Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, but when in close orbits with less dense stars, white dwarfs can strip material from their companions, and the resulting mass transfer can generate atomic line and X-ray emission, as well as near- and mid-infrared radiation if the white dwarf is magnetic. However, even in binaries, white dwarfs are rarely detected at far-infrared or radio frequencies. Here we report the discovery of a white dwarf / cool star binary that emits from X-ray to radio wavelengths. The star, AR Scorpii (henceforth AR Sco), was classified in the early 1970s as a delta-Scuti star, a common variety of periodic variable star. Our observations reveal instead a 3.56 hr period close binary, pulsing in brightness on a period of 1.97 min. The pulses are so intense that AR Sco's optical flux can increase by a factor of four within 30 s, and they are detectable a...

  16. Comparison of theoretical white dwarf cooling timescales

    CERN Document Server

    Salaris, Maurizio; García-Berro, Enrique

    2013-01-01

    An accurate assessment of white dwarf cooling times is paramount to place white dwarf cosmochronology of Galactic populations on more solid grounds. This issue is particularly relevant in view of the enhanced observational capabilities provided by the next generation of Extremely Large Telescopes, that will offer more avenues to employ white dwarfs as probes of Galactic evolution and test-beds of fundamental physics. We estimate for the first time the consistency of results obtained from two independent and widely used evolutionary codes (BaSTI and LPCODE) for white dwarf models with fixed mass and chemical stratification, when the same input physics is employed in both codes. We considered 0.55Msun white dwarf models with both pure carbon and uniform carbon-oxygen (50/50 mass fractions) core. We have assessed for the first time the maximum possible accuracy in the current estimates of white dwarf cooling times, resulting only from the different implementations of the stellar evolution equations and homogeneo...

  17. ON THE EVOLUTION OF MAGNETIC WHITE DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Tremblay, P.-E. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Fontaine, G.; Brassard, P. [Département de Physique, Université de Montréal, C. P. 6128, Succursale Centre-Ville, Montréal, QC H3C 3J7 (Canada); Freytag, B. [Department of Physics and Astronomy at Uppsala University, Regementsvägen 1, Box 516, SE-75120 Uppsala (Sweden); Steiner, O. [Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, D-79104 Freiburg (Germany); Ludwig, H.-G. [Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, D-69117 Heidelberg (Germany); Steffen, M. [Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany); Wedemeyer, S., E-mail: tremblay@stsci.edu [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo (Norway)

    2015-10-10

    We present the first radiation magnetohydrodynamic simulations of the atmosphere of white dwarf stars. We demonstrate that convective energy transfer is seriously impeded by magnetic fields when the plasma-β parameter, the thermal-to-magnetic-pressure ratio, becomes smaller than unity. The critical field strength that inhibits convection in the photosphere of white dwarfs is in the range B = 1–50 kG, which is much smaller than the typical 1–1000 MG field strengths observed in magnetic white dwarfs, implying that these objects have radiative atmospheres. We have employed evolutionary models to study the cooling process of high-field magnetic white dwarfs, where convection is entirely suppressed during the full evolution (B ≳ 10 MG). We find that the inhibition of convection has no effect on cooling rates until the effective temperature (T{sub eff}) reaches a value of around 5500 K. In this regime, the standard convective sequences start to deviate from the ones without convection due to the convective coupling between the outer layers and the degenerate reservoir of thermal energy. Since no magnetic white dwarfs are currently known at the low temperatures where this coupling significantly changes the evolution, the effects of magnetism on cooling rates are not expected to be observed. This result contrasts with a recent suggestion that magnetic white dwarfs with T{sub eff} ≲ 10,000 K cool significantly slower than non-magnetic degenerates.

  18. Spectroscopy of Hyades L dwarf candidates

    CERN Document Server

    Lodieu, N; Bejar, V J S

    2014-01-01

    We present the results of photometric, astrometric, and spectroscopic follow-up of L dwarf candidates identified in the Hyades cluster by Hogan et al. (2008). We obtained low-resolution optical spectroscopy with the OSIRIS spectrograph on the Gran Telescopio de Canarias for all 12 L dwarf candidates as well as new J-band imaging for a subsample of eight to confirm their proper motion. We also present mid-infrared photometry from the Wise Field Infrared Survey Explorer (WISE) for the Hyades L and T dwarf candidates and estimate their spectroscopic distances, effective temperatures, and masses. We confirm the cool nature of several L dwarf candidates and confirm astrometrically their membership, bridging the gap between the coolest M dwarfs and the two T dwarfs previously reported in the Hyades cluster. These members represent valuable spectral templates at an age of 625 Myr and slightly super solar metallicity (Fe/H=+0.13). We update the Hyades mass function across the hydrogen-burning limit and in the substel...

  19. Flickering of accreting white dwarfs: the remarkable amplitude - flux relation and disc viscocity

    CERN Document Server

    Zamanov, R K; Latev, G; Sokoloski, J L; Stoyanov, K A; Genkov, V; Tsvetkova, S V; Tomov, T; Antov, A; Bode, M F

    2015-01-01

    We analyze optical photometric data of short term variability (flickering) of accreting white dwarfs in cataclysmic variables (KR Aur, MV Lyr, V794 Aql, TT Ari, V425 Cas), recurrent novae (RS Oph and T CrB) and jet-ejecting symbiotic stars (CH Cyg and MWC 560). We find that the amplitude-flux relationship is visible over four orders of magnitude, in the range of fluxes from $10^{29}$ to $10^{33}$ erg s$^{-1}$ \\AA$^{-1}$, as a "statistically perfect" correlation with correlation coefficient 0.96 and p-value $ \\sim 10^{-28}$. In the above range, the amplitude of variability for any of our 9 objects is proportional to the flux level with (almost) one and the same factor of proportionality for all 9 accreting white dwarfs with $\\Delta F = 0.36 (\\pm 0.05) F_{av}$, $\\sigma_{rms} = 0.086(\\pm 0.011) F_{av}$, and $\\sigma_{rms} / \\Delta F = 0.24 \\pm 0.02$. Over all, our results indicate that the viscosity in the accretion discs is practically the same for all 9 objects in our sample, in the mass accretion rate range $2...

  20. Supersoft X-ray Light Curve of RS Oph -- The White Dwarf Mass is Now Increasing

    CERN Document Server

    Kato, Mariko; Luna, Gerardo Juan Manuel

    2008-01-01

    The recurrent nova RS Ophiuchi, one of the candidates for Type Ia supernova progenitors, underwent the sixth recorded outburst in February 2006. We report a complete light curve of supersoft X-ray that is obtained for the first time. A numerical table of X-ray data is provided. The supersoft X-ray flux emerges about 30 days after the optical peak and continues until about 85 days when the optical flux shows the final decline. Such a long duration of supersoft X-ray phase can be naturally understood by our model in which a significant amount of helium layer piles up beneath the hydrogen burning zone during the outburst, suggesting that the white dwarf mass is effectively growing up. We have estimated the white dwarf mass in RS Oph to be 1.35 \\pm 0.01 M_\\sun and its growth rate to be about (0.5-1) \\times 10^{-7} M_\\sun yr^{-1} in average.