Related papers: Discovery of optical flickering from the symbiotic…

White dwarf symbiotic binaries are detected in X-rays with luminosities in the range of 10$^{30}$ to 10$^{34}$ lumcgs. Their X-ray emission arises either from the accretion disk boundary layer, from a region where the winds from both…

The recently discovered system J0651 is the tightest known detached white dwarf (WD) binary. Since it has not yet initiated Roche-lobe overflow, it provides a relatively clean environment for testing our understanding of tidal interactions.…

We obtained time-resolved optical photometry and spectroscopy of the nova-like variable KR Aurigae in the low state. The spectrum reveals a DAB white dwarf and a mid-M dwarf companion. Using the companion star's $i$-band ellipsoidal…

Most known white dwarfs in multiple systems with main sequence stars have been discovered with M-type companions, because the white dwarf causes detectable UV excess and bluer colors than expected from a single M star. Surveys have shown…

We have identified a star in the WASP archive photometry with an unusual lightcurve due to the total eclipse of a small, hot star by an apparently normal A-type star and with an orbital period of only 0.668d. From an analysis of the WASP…

Taking advantage of the now available Gaia EDR3 parallaxes, we carry out an archival {\it Hubble Space Telescope} (HST) far ultraviolet spectroscopic analysis of 10 cataclysmic variable systems, including 5 carefully selected eclipsing…

We present deep and accurate photometry (F435W, F625W, F658N) of the Galactic Globular Cluster Omega Cen collected with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope (HST). We identified ~ 6,500 white dwarf…

We present optical high-speed photometry of three millisecond pulsars with low-mass ($< 0.3 M_{\odot}$) white dwarf companions, bringing the total number of such systems with follow-up time-series photometry to five. We confirm the…

We have conducted a 1.5 year-long variability study of the stars in the Cygnus OB2 association, the region in the northern hemisphere with the highest density of optically visible massive stars. The survey was conducted using four pointings…

We report the discovery of ZTF J0127+5258, a compact mass-transferring binary with an orbital period of 13.7 minutes. The system contains a white dwarf accretor, which likely originated as a post-common envelope carbon-oxygen (CO) white…

Use of the highly sensitive Hokupa'a/Gemini curvature wavefront sensor has allowed for the first time direct adaptive optics (AO) guiding on M8-M9 very low mass (VLM) stars. An initial survey of 20 such objects (SpT=M8-M9) discovered 4…

Symbiotic binaries are long period interacting binaries consisting of a white dwarf (WD) accreting material from a cool evolved giant star via stellar winds. In this paper we study the symbiotic binary LIN 358 located in the SMC. We have…

White dwarfs are among the most common objects in the stellar halo; however, due to their low luminosity and low number density compared to the stars in the discs of the Milky Way, they are scarce in the observable volume. Hence, they are…

The hot subdwarf HD 49798 has an X-ray emitting compact companion with a spin-period of 13.2 s and a dynamically measured mass of 1.28+/-0.05 M_sun, consistent with either a neutron star or a white dwarf. Using all the available XMM-Newton…

R Aqr is a symbiotic binary system consisting of a mira variable, a hot companion with a spectacular jet outflow, and an extended emission line nebula. We have used R Aqr as test target for the visual camera subsystem ZIMPOL, which is part…

We describe the first results from a program of multi-wavelength monitoring of symbiotic binary stars in outburst. The prototypical symbiotic star Z Andromedae was observed extensively at radio, optical, far-UV, and X-ray wavelengths during…

The Extremely Low Mass White Dwarfs (ELM WDs) and pre-ELM WDs are helium core white dwarfs with mass $<\sim 0.3M_{\odot}$. Evolution simulations show that a lower mass limit for ELM WDs exists at $\approx0.14M_{\odot}$ and no one is…

This work presents the first large-scale photometric variability survey of the intermediate age (~200 Myr) open cluster M11. Thirteen nights of data over two observing seasons were analyzed (using crowded field and ensemble photometry…

Stellar activity cycles reveal continuous relaxation and induction of magnetic fields. The activity cycle is typically traced through the observation of cyclic variations in total brightness or Ca H&K emission flux of stars, as well as…

White-light superflares from ultra cool stars are thought to be resulted from magnetic reconnection, but the magnetic dynamics in a fully convective star is not clear yet. In this paper, we report a stellar superflare detected with the…