Related papers: EX Draconis: Using Eclipses to Separate Outside-In…
We present new eclipse observations of the polar (i.e. semi-detached magnetic white dwarf + M-dwarf binary) HU Aqr, and mid-egress times for each eclipse, which continue to be observed increasingly early. Recent eclipses occurred more than…
We study the dynamical behaviour of the galactic black hole source GX 339-4 during 2002-2011 outbursts using RXTE, Swift(XRT), XMM-Newton(PN) archival data. We present the spectral evolution of the source using four outbursts data and…
We report the detection of a dwarf nova (DN) in the core region of the globular cluster M55. Six outbursts were observed during 8 observing seasons spanning the period 1997-2004. The variable has an X-ray counterpart detected on images…
Understanding how material accretes onto the rotationally supported disk from the surrounding envelope of gas and dust in the youngest protostellar systems is important for describing how disks are formed. Magnetohydrodynamic simulations of…
In recent years, luminous X-ray outbursts with variability amplitudes as high as ~ 400 have been serendipitously detected from a small number of active and inactive galaxies. These outbursts may result from the tidal disruptions of stars by…
The flux and spectrum of the black hole candidate GX339-4 has been monitored by the Burst and Transient Source Experiment (BATSE) on the Compton Gamma-ray Observatory (CGRO) since the observatory became operational in May 1991. Between the…
New eclipse timings of the Z Cam-type dwarf nova AY Psc were measured and the orbital ephemeris was revised. Based on the long-term AAVSO data, moreover, the outburst behaviors were also explored. Our analysis suggests that the normal…
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…
In order to study the growth and evolution of circumstellar disks around classical Be stars, we analyze optical time-series photometry from the KELT survey with simultaneous infrared and visible spectroscopy from the APOGEE survey and BeSS…
GK Dra is a detached eclipsing binary system containing two early-F stars, one evolved, in an orbit with a period of 9.974 d and a small eccentricity. Its eclipsing nature was discovered using Hipparcos data, and pulsations were found in…
U Sco is a recurrent nova which showed recorded outbursts in 1863, 1906, 1936, 1979, 1987, and most recently in 1999. The eclipsing nature of the object was discovered after the 1987 outburst. We examined our time-series photographic…
We study the timing and spectral properties of the X-ray pulsar 2S 1417--624 during the recent outburst in January 2021 based on the Neutron Star Interior Composition Explorer (NICER) observation. We also used some early data from the 2018…
While accreting through a circumstellar disk, young stellar objects are observed to undergo sudden and powerful accretion events known as FUor or EXor outbursts. Although such episodic accretion is considered to be an integral part of the…
The neutron star X-ray binary, EXO 0748--676, was observed regularly by the Rossi X-ray Timing Explorer (RXTE) and XMM-Newton during its first detected outburst (1985 - 2008). These observations captured hundreds of asymmetric,…
EX Lup-type objects (EXors) are low-mass pre-main sequence objects characterized by outbursts attributed to highly enhanced disk accretion. The trigger mechanism of EXor outbursts is still debated. One theory requires a close (sub)stellar…
We analyse how drag forces modify the orbits of objects moving through extended gaseous distributions. We consider how hydrodynamic (surface area) drag forces and dynamical friction (gravitational) drag forces drive the evolution of orbital…
Accreting white dwarfs are known to show signatures of wind-type outflows in the ultraviolet. At optical wavelengths, however, wind detections have only been reported for a few sources. We present GTC-10.4m optical spectroscopy of four…
Following the pulsation spectrum of a white dwarf through the heating and cooling involved in a dwarf nova outburst cycle provides a unique view of the changes to convective driving that take place on timescales of months versus millenia…
We present here, for the first time, a 2D study of the overshoot convective mechanism in nova outbursts for a wide range of possible compositions of the layer underlying the accreted envelope. Previous surveys studied this mechanism only…
We observed the deeply eclipsing SU UMa-type dwarf nova V4140 Sgr and established the very short supercycle of 69.7(3) d. There were several short outbursts between superoutbursts. These values, together with the short orbital period…