Related papers: SDSS J134441.83+204408.3: A highly asynchronous, s…

We present time-resolved photometry of six faint (V>17mag) cataclysmic variables (CVs); one of them is V849 Oph and the others are identified from the Sloan Digital Sky Survey (SDSS J0920+0042, SDSS J1327+6528, SDSS J1227+5139, SDSS…

We model the structure of the surface magnetic fields of the hydrogen-rich white dwarfs in the SDSS. We have calculated a grid of state-of-the-art theoretical optical spectra of hydrogen-rich magnetic white dwarfs with magnetic field…

We present optical photometric and spectroscopic observations of two Cataclysmic Variables (CVs), namely RBS 0490 and SDSS J075939.79+191417.3. The optical variations of RBS 0490 have been found to occur at the period of 1.689$\pm$0.001 hr…

[abridged] We report four years of radial velocity monitoring observations of SDSS J080531.84+481233.0 that reveal significant and periodic variability, confirming the binary nature of the source. We infer an orbital period of 2.02$\pm$0.03…

White dwarfs represent the last stage of evolution of stars with mass less than about eight times that of the Sun and, like other stars, are often found in binaries. If the orbital period of the binary is short enough, energy losses from…

M dwarfs are the most abundant stars in the Galaxy and exhibit diverse magnetic behaviours. Understanding their large-scale magnetic fields is essential to study stellar dynamos and assess the impact of magnetic activity on planetary…

WD J005311 is the peculiar stellar remnant of the Galactic supernova from 1181, and appears to have been the merger of two white dwarfs. We present time-resolved spectroscopy of WD J005311 showing emission line variability on a wide range…

We have carried out detailed time-resolved timing analyses of three cataclysmic variables (CVs) namely LS Cam, V902 Mon, and SWIFT J0746.3-1608, using the long-baseline, high-cadence optical photometric data from the Transiting Exoplanet…

Rapidly rotating late M dwarfs are observed in two different branches of magnetic activity, although they operate in the same stellar parameter range. Current empirical evidence indicates that M dwarfs with spectral types ranging from M3 /…

We report our discovery of an extremely rare, low mass, quadruple-lined spectroscopic binary BD-22 5866 (=NLTT 53279, integrated spectral type = M0 V), found during an ongoing search for the youngest M dwarfs in the solar neighborhood. From…

We present phase-resolved spectroscopy of the short period cataclysmic variable WZ Sge obtained with the Hubble Space Telescope. We were able to resolve the orbital motion of a number of absorption lines that likely probe the environment…

Magnetic cataclysmic variables are close binary systems containing a strongly magnetized white dwarf that accretes matter coming from an M-dwarf companion. High-energy radiation coming from those objects is emitted from the accretion column…

We present high-speed, three-colour photometry of the eclipsing cataclysmic variable SDSS J170213.26+322954.1 (hereafter SDSS J1702+3229). This system has an orbital period of 2.4 hours, placing it within the ``period gap'' for cataclysmic…

We present simultaneous UV-G-R-I monitoring of 19 M dwarfs that revealed a huge flare on the M9 dwarf 2MASSW J1707183+643933 with an amplitude in the UV of at least 6 magnitudes. This is one of the strongest detections ever of an optical…

We present spectroscopy of the optical counterpart to 1RXS J162848.1-41524, also known as the microquasar candidate MCQC J162847-4152. All the data indicate that this X-ray source is not a microquasar, and that it is a single-lined…

We report the discovery of spectroscopic variations in the magnetic DBA white dwarf SDSS J091016.43+210554.2. Follow-up time-resolved spectroscopy at the Apache Point Observatory (APO) and the MMT show significant variations in the H…

Double white dwarf (DWD) mergers are possibly the leading formation channel of massive, rapidly rotating, high-field magnetic white dwarfs (HFMWDs). However, the direct link connecting a DWD merger to any observed HFMWD is still missing. We…

We present a catalog of periodic stellar variability in the "Stripe 82" region of the Sloan Digital Sky Survey (SDSS). After aggregating and recalibrating catalog-level data from the survey, we ran a period-finding algorithm (Supersmoother)…

Red optical and near-infrared spectroscopy are presented for SDSS J125637.13-022452.4, one of only four L subdwarfs reported to date. These data confirm the low-temperature, metal-poor nature of this source, as indicated by prominent…

AR Scorpii, the so called white dwarf pulsar, contains a rapidly rotating magnetic white dwarf (WD; Pspin = 117.0564 s) interacting with a cool, red dwarf (RD) companion in a 3.56 hour orbit. It is a strong radio source with an inverted…