Related papers: RXJ1313.2-3259, a missing link in CV evolution?
We calculate the heating and cooling of the accreting white dwarf (WD) in the ultracompact AM Canum Venaticorum (AM CVn) binaries and show that the WD can contribute significantly to their optical and ultraviolet emission. We estimate the…
HD 49798/RX J0648.0--4418 is a peculiar X-ray binary with a hot subdwarf (sdO) mass donor. The nature of the accreting compact object is not known, but its spin period $P=13.2$~s and $\dot P =-2.15 \times 10^{-15}$s~s$^{-1}$, prove that it…
We report the discovery and analysis of PTF1 J085713+331843, a new eclipsing post common-envelope detached white-dwarf red-dwarf binary with a 2.5h orbital period discovered by the Palomar Transient Factory. ULTRACAM multicolour photometry…
The presence of ultra-high excitation (UHE) absorption lines (e.g., O VIII) in the optical spectra of several of the hottest white dwarfs poses a decades-long mystery and is something that has never been observed in any other astrophysical…
In recent years there has been much interest in the nature of two stars, V407 Vul and RXJ0806+1527, which are widely thought to be binary white dwarfs of very short orbital period, 570 and 321 seconds respectively. As such they should be…
We present an analysis of high-speed u- and r-band photometry of the eclipsing polar HU Aquarii that was obtained with ULTRACAM mounted on the VLT. The observations were performed during a low state, permitting us for the first time to…
The discovery of two accreting millisecond X-ray pulsars in binaries with 43 minute orbital periods allows for a new probe of the donor's structure. For XTE J1751-305, only a hot white dwarf (WD) can fill the Roche Lobe. A cold He WD is a…
We calculate the stellar evolution of both white dwarfs (WDs) in AM CVn binaries with orbital periods of $P_{\mathrm{orb}} \approx 5-70$ minutes. We focus on the cases where the donor starts as a $M_{\mathrm{He}} < 0.2 \, M_{\odot}$ Helium…
Time-resolved spectra throughout the orbit of EF Eri during its low accretion state were obtained with the Solar Blind Channel on the Advanced Camera for Surveys onboard the Hubble Space Telescope. The overall spectral distribution exhibits…
We present spectroscopy and time-series photometry of the newly discovered dwarf nova 1RXS J232953.9+062814. Photometry in superoutburst reveals a superhump with a period of 66.06(6) minutes. The low state spectrum shows Balmer and HeI…
High-energy data of accreting white dwarfs give access to the regime of the primary accretion-induced energy release and the different proposed accretion scenarios. We perform XMM-Newton observations of polars selected due to their ROSAT…
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…
We present a comprehensive photometric, spectroscopic, and polarimetric study of the intermediate polar (IP) 1RXS J080114.6-462324, using observations from the South African Astronomical Observatory (SAAO) 1.0-m and 1.9-m telescopes and the…
We present imaging circular polarimetry and near-infrared photometry of the suspected ultra-short period white-dwarf binary RX J0806.3+1527 obtained with the ESO VLT and discuss the implications for a possible magnetic nature of the white…
We have carried out a combined Hubble Space Telescope (HST/GHRS) and Far Ultraviolet Spectroscopic Explorer FUSE) analysis of the prototype dwarf nova SS Cygni during quiescence. The FUSE and HST spectra were obtained at comparable times…
Following the suggestion of Schwope et al that the magnetic cataclysmic variable RX J2115-5840 maybe a near-synchronous polar, we obtained optical polarimetry of this system over a 2 week period. From a power spectrum of the circular…
We present a 904-1183 A spectrum of the dwarf nova VW Hydri taken with the Far Ultraviolet Spectroscopic Explorer during quiescence, eleven days after a normal outburst, when the underlying white dwarf accreter is clearly exposed in the far…
Cataclysmic variables (CVs) are binary systems consisting of a white dwarf (WD) accreting matter from a companion star. Observations of CVs provide an opportunity to learn about accretion disks, the physics of compact objects, classical…
An interesting question about ultracool dwarfs recently raised in the literature is whether their emission is purely internally driven or partially powered by external processes similar to planetary aurora known from the solar system. In…
White dwarfs are almost completely degenerate objects that cannot obtain energy from thermonuclear sources, so their evolution is just a gravothermal cooling process. Recent improvements in the accuracy and precision of the luminosity…