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4 results on '"stars : novae, cataclysmic variables"'

1. Cyclic brightening in the short-period WZ Sge-type cataclysmic variable SDSS J080434.20+510349.2

Author

G. G. Valyavin, Young Beom Jeon, V. V. Neustroev, Sergey Zharikov, Juan Echevarria, Ángel Benigno González Avilés, Elena P. Pavlenko, Raul Michel, Gaghik H. Tovmassian, I. F. Bikmaev, and C. Zurita

Subjects
stars, stars : novae, cataclysmic variables, Period (periodic table), humps, FOS: Physical sciences, Cataclysmic variable star, Astrophysics, sagittae, techniques : photometric, superoutburst, superhumps, Physics, accretion disks, Astrophysics (astro-ph), stars : dwarf novae, Astronomy and Astrophysics, Light curve, Orbital period, dwarf novae, Amplitude, Space and Planetary Science, Magnitude (astronomy), methods : observational, discovery, radius
Abstract

We have observed a new cataclysmic variable (CV) SDSS J080434.20+510349.2 and study the origin of a long-term variability found in its light curve. Multi-longitude time-resolved photometric observations were carried out to analyze the uncommon behavior also found recently in two newly discovered CVs. This study of SDSS J080434.20+510349.2 mainly concerns the understanding of the nature of the observed double-humped light curve and its relation to a cyclic brightening occurring during quiescence. The observations were obtained early in 2007, when the object was at about V~17.1, 0.4 mag brighter than the pre-outburst magnitude. The light curve shows a sinusoidal variability with an amplitude of about 0.07 mag and a periodicity of 42.48 min, which is half of the orbital period of the system. In addition, we have observed two "mini-outbursts" of the system up to 0.6 mag, with a duration of about 4 days each. The "mini-outburst" had a symmetric profile and repeated in about 32 days. Subsequent monitoring of the system shows a cyclical behaviour of such "mini-outbursts" with a similar recurrence period. The origin of the double-humped light curve and the periodic brightening is discussed in the light of the evolutionary state of SDSS J080434.20+510349.2., 7 pages, 6 figures, Accepted by A&A, typos added, figure corrected

Published
2008
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2. The OGLE-II event sc5_2859 : a Classical Nova outburst?

Author

C. Afonso, J. F. Glicenstein, A. Gould, M. C. Smith, R. M. Wagner, J. N. Albert, J. Andersen, R. Ansari, É. Aubourg, P. Bareyre, J. P. Beaulieu, G. Blanc, X. Charlot, C. Coutures, R. Ferlet, P. Fouqué, B. Goldman, D. Graff, M. Gros, J. Haissinski, C. Hamadache, J. de Kat, L. LeGuillou, É. Lesquoy, C. Loup, C. Magneville, J. B. Marquette, É. Maurice, A. Maury, A. Milsztajn, M. Moniez, N. Palanque-Delabrouille, O. Perdereau, L. Prévot, Y. R. Rahal, J. Rich, M. Spiro, P. Tisserand, A. Vidal-Madjar, L. Vigroux, S. Zylberajch, Département d'Astrophysique, de physique des Particules, de physique Nucléaire et de l'Instrumentation Associée (DAPNIA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire de l'Accélérateur Linéaire (LAL), Université Paris-Sud - Paris 11 (UP11)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS), AstroParticule et Cosmologie (APC (UMR_7164)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS), Institut d'Astrophysique de Paris (IAP), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Laboratoire d'Astrophysique de Marseille (LAM), Aix Marseille Université (AMU)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Services communs OMP (UMS 831), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), EROS, Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Université Paris-Sud - Paris 11 (UP11), Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris Diderot - Paris 7 (UPD7)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Pierre et Marie Curie - Paris 6 (UPMC), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS), Astronomy, Institut National de Physique Nucléaire et de Physique des Particules du CNRS (IN2P3)-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Université Paris Diderot - Paris 7 (UPD7), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Aix Marseille Université (AMU)-Centre National d'Études Spatiales [Toulouse] (CNES), Services communs OMP - UMS 831 (UMS 831), Centre National de la Recherche Scientifique (CNRS)-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Toulouse III - Paul Sabatier (UT3), and Université Fédérale Toulouse Midi-Pyrénées

Subjects
stars : novae, cataclysmic variables, MACHO PROJECT, 010504 meteorology & atmospheric sciences, Event (relativity), GRAVITATIONAL LENSING EXPERIMENT, Gravitational lensing, FOS: Physical sciences, Astrophysics, Gravitational microlensing, 01 natural sciences, Galaxy : stellar contents, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], 0103 physical sciences, Galaxy:stellar contents, Emission spectrum, 010303 astronomy & astrophysics, BLACK-HOLES, 0105 earth and related environmental sciences, Physics, cataclysmic variables, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], MICROLENSING OPTICAL DEPTH, Astrophysics (astro-ph), Astronomy and Astrophysics, Light curve, DIFFERENCE IMAGE-ANALYSIS, CATALOG, Nova (rocket), GALACTIC BULGE FIELDS, Space and Planetary Science, stars : novae, novæ
Abstract

The OGLE-II event sc5_2859 was previously identified as the third longest microlensing event ever observed. Additional photometric observations from the EROS (Experience de Recherche d'Objets Sombres) survey and spectroscopic observations of the candidate star are used to test the microlensing hypothesis.The combined OGLE and EROS data provide a high quality coverage of the light curve. The colour of the sc5_2859 event is seen to change with time. A spectrum taken in 2003 exhibits a strong Halpha emission line. The additionnal data show that the OGLE-II sc5_2859 event is actually a classical nova outburst., Comment: Accepted for publication in Astronomy and Astrophysics

Published
2006
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3. On the mass transfer in AE Aquarii

Author

V. V. Neustroev, N. R. Ikhsanov, and N. G. Beskrovnaya

Subjects
stars : novae, cataclysmic variables, stars : individual : ae aqr, Magnetosphere, Binary number, FOS: Physical sciences, Astrophysics, magnetic fields, intermediate polars, Luminosity, magnetic propeller, symbols.namesake, accretion, Mass transfer, emission, white-dwarf, Roche lobe, Physics, cataclysmic variables, spin-down, x-rays : binaries, Astrophysics (astro-ph), White dwarf, stars : pulsars : general, Astronomy and Astrophysics, stars : white dwarfs, neutron-stars, flares, Space and Planetary Science, rosat observations, symbols, Alpha decay, Doppler effect
Abstract

The observed properties of the close binary AE Aqr indicate that the mass transfer in this system operates via the Roche lobe overflow mechanism, but the material transferred from the normal companion is neither accreted onto the surface of the white dwarf nor stored in a disk around its magnetosphere. As previously shown, such a situation can be realized if the white dwarf operates as a propeller. At the same time, the efficiency of the propeller action by the white dwarf is insufficient to explain the rapid braking of the white dwarf, which implies that the spin-down power is in excess of the bolometric luminosity of the system. To avoid this problem we have simulated the mass-transfer process in AE Aqr assuming that the observed braking of the white dwarf is governed by a pulsar-like spin-down mechanism. We show that the expected H_alpha Doppler tomogram in this case resembles the tomogram observed from the system. We find that the agreement between the simulated and the observed tomograms is rather good provided the mean value of the mass-transfer rate ~5x10^16 g/s. Three spatially separated sources of H_alpha emission can be distinguished within this approach. The structure of the tomogram depends on the relative contributions of these sources to the H_alpha emission and is expected to vary from night to night., Comment: 12 pages, 3 figures (6 eps files). Published in A&A. The paper with high resolution images can be downloaded from http://urania.it.nuigalway.ie/papers/ae_aqr.ps.gz

Published
2004
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4. EROS VARIABLE STARS: Discovery of beat Cepheids in the Small Magellanic Cloud and the effect of metallicity on pulsation

Author

de Laverny, P, Beaulieu, JP, Asplund, M, Kilkenny, D, Renault, C, Ferlet, R, Marquette, JB, Vidal-Madjar, A, Maurice, E, Prevot, L, Aubourg, E, Bareyre, P, Bauer, F, Brehin, S, Coutures, C, de Kat, J, Gros, M, Laurent, B, Lachieze-Rey, M, Lesquoy, E, Magneville, C, Milsztajn, A, Moscoso, L, Queinnec, F, Rich, J, Spiro, M, Vigroux, L, Zylberajch, S, Ansari, R, Cavalier, F, Moniez, M, and Kapteyn Astronomical Institute

Subjects
stars : novae, cataclysmic variables, EXTINCTION, surveys, galaxies : Magellanic Clouds, SPECTRAL EVOLUTION
Abstract

We report the discovery of a slow nova found in the core of the Small Magellanic Cloud by the EROS microlensing survey. Nova SMC 1994 is a classical nova with a DQ Her type lightcurve characterized by a deep minimum. Low amplitude variations occurring on time-scales of hours and days are also detected at maximum light. Spectra collected during the nebular phase indicate that Nova SMC 1994 is similar to Galactic novae of the same class. Large helium enhancement in the shell is found and O and N enrichments are suspected.

Published
1998

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