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We present ASCA observations of the dwarf nova Z Camelopardalis during outburst and during a transition from quiescence to another outburst. At the beginning of the transition the X-ray count rate was an order of magnitude higher and the…

Astrophysics · Physics 2009-11-07 D. S. Baskill , P. J. Wheatley , J. P. Osborne

We present a study of the eclipses in the accreting white dwarf EX Dra during TESS Cycles 14 and 15. During both of the two outbursts present in this dataset, the eclipses undergo a hysteretic loop in eclipse-depth/out-of-eclipse-flux…

We report optical CCD photometry of the recently identified symbiotic star EF Aql. Our observations in Johnson V and B bands clearly show the presence of stochastic light variations with an amplitude of about 0.2 mag on a time scale of…

Solar and Stellar Astrophysics · Physics 2017-09-06 R. K. Zamanov , S. Boeva , Y. M. Nikolov , B. Petrov , R. Bachev , G. Y. Latev , V. A. Popov , K. A. Stoyanov , M. F. Bode , J. Marti , T. Tomov , A. Antonova

Although during the last decade new observations and new theoretical results have brought better understanding of the physics of accretion onto compact objects, many old and several new questions and problems await answers and solutions. I…

High Energy Astrophysical Phenomena · Physics 2024-01-24 Jean-Pierre Lasota

The eruptive cycles of dwarf novae (DN) are thought to be due to a thermal-viscous instability in the accretion disk surrounding the white dwarf (WD). This model has long been known to imply a stress to pressure ratio \alpha ~0.1 in…

Solar and Stellar Astrophysics · Physics 2018-01-17 N. Scepi , G. Lesur , G. Dubus , M. Flock

In order to provide an explanation for the unexpected radial brightness distribution of the steady accretion discs seen in nova-like variables, Nixon & Pringle (2019) proposed that the accretion energy is redistributed outwards by means of…

High Energy Astrophysical Phenomena · Physics 2020-04-15 C. J. Nixon , J. E. Pringle

As an eclipsing polar with 3.39 hrs orbital period, MN Hya was going through state change when we observed it during 2009-2016. 10 new mid-eclipse times, along with others obtained from literature, allow us to give a new ephemeris. The…

Solar and Stellar Astrophysics · Physics 2018-07-25 Qi-Shan Wang , Sheng-Bang Qian , Zhong-Tao Han , Miloslav Zejda , Eduardo Fernández-Lajus , Li-Ying Zhu

T Aurigae is an eclipsing old nova which exploded in 1891. At a Gaia EDR3 distance of 815-871 pc, it is a relatively nearby old nova. Through ultraviolet spectral modeling and using the new precise Gaia distance, we find that the HST/STIS…

Solar and Stellar Astrophysics · Physics 2022-06-08 Conor Larsen , Patrick Godon , Edward Sion

We have detected coherent oscillations, at multiple frequencies, in the line and continuum emission of the eclipsing dwarf nova V2051 Ophiuchi using the 10m Keck II telescope. Our own novel data acquisition system allowed us to obtain very…

Astrophysics · Physics 2009-10-31 D. Steeghs , K. O'Brien , K. Horne , R. Gomer , J. B. Oke

Observations of heavy metal pollution in white dwarf stars indicate that metal-rich planetesimals are frequently scattered into star-grazing orbits, tidally disrupted, and accreted onto the white dwarf surface, offering direct insight into…

Solar and Stellar Astrophysics · Physics 2018-02-21 E. Dennihy , J. C. Clemens , B. H. Dunlap , S. M. Fanale , J. T. Fuchs , J. J. Hermes

Here we show that in the case when double peaked emission lines originate from outer parts of accretion disk, their variability could be caused by perturbations in the disk emissivity. In order to test this hypothesis, we introduced a model…

Astrophysics of Galaxies · Physics 2015-05-19 P. Jovanović , L. Č. Popović , M. Stalevski , A. I. Shapovalova

The outbursts of low mass X-ray binaries are prolonged relative to those of dwarf nova cataclysmic variables as a consequence of X-ray irradiation of the disc. We show that the time-scale of the decay light curve and its luminosity at a…

Astrophysics · Physics 2008-11-26 Craig R. Powell , Carole A. Haswell , Maurizio Falanga

We show that the Keplerian thin disk in quiescent Soft X-ray Transients cannot extend down to the last stable orbit around the central black hole. We analyse the properties of the Narayan, McClintock & Yi (1996) model of quiescent Soft…

Astrophysics · Physics 2007-05-23 J. -P. Lasota , R. Narayan , I. Yi

SS Cyg has long been recognized as the prototype of a group of dwarf novae that show only outbursts. However, this object has entered a quite anomalous event in 2021, which at first appeared to be standstill, i.e., an almost constant…

We report on high-speed eclipse photometry of the dwarf nova V2051 Oph while it was in a low brightness state, at B ~ 16.2 mag. In comparison to the average IUE spectra, the ultraviolet continuum and emission lines appear reduced by factors…

Astrophysics · Physics 2009-10-30 Raymundo Baptista , M. S. Catalan , Keith Horne , D. Zilli

The observed properties of novae before and after eruption are discussed. The distribution of orbital periods of novae shows a concentration near 3.2 h, which resembles that of magnetic cataclysmic variables, and there is some evidence that…

Astrophysics · Physics 2009-11-07 Brian Warner

In this paper we present high time-resolution observations of GW Librae and SDSS J161033.64-010223.3 -- two cataclysmic variables which have shown periodic variations attributed to non-radial pulsations of the white dwarf. We observed both…

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…

Solar and Stellar Astrophysics · Physics 2014-07-02 Albert Bruch

CH Cygni began producing rapid, stochastic optical variations with the onset of symbiotic activity in 1963. We use changes in this flickering between 1997 and 2000 to diagnose the state of the accretion disk during this time. In the 1998…

Astrophysics · Physics 2009-11-07 J. L. Sokoloski , S. J. Kenyon

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…

High Energy Astrophysical Phenomena · Physics 2015-05-25 D. I. Sahman , V. S. Dhillon , C. Knigge , T. R. Marsh