Related papers: A New Small-Amplitude Variable Hot DQ White Dwarf

We have calculated optical spectra of hydrogen-rich (DA) white dwarfs with magnetic field strengths between 1 MG and 1000 MG for temperatures between 7000 K and 50000 K. Through a least-squares minimization scheme with an evolutionary…

We present follow-up spectroscopy of 711 white dwarfs within 100 pc, and present a detailed model atmosphere analysis of the 100 pc white dwarf sample in the SDSS footprint. Our spectroscopic follow-up is complete for 83% of the white…

White dwarfs carry information on the structure and evolution of the Galaxy, especially through their luminosity function and initial-to-final mass relation. Very cool white dwarfs provide insight into the early ages of each population.…

SDSS 1355+0856 was identified as a hot white dwarf (WD) with a binary companion from time-resolved SDSS spectroscopy as part of the ongoing SWARMS survey. Follow-up observations with the ARC 3.5m telescope and the MMT revealed weak emission…

We present the analysis of 71 hours of high quality time-series CCD photometry of the helium atmosphere pulsating white dwarf (DBV) EC 04207-4748 obtained using the facilities at Mt John University Observatory in New Zealand. The…

We found that ZTF J185139.81+171430.3 = ZTF18abnbzvx shows a very short [0.00858995(3) d = 12.37 min] and large-amplitude (0.8 mag) coherent variations using Public Data Release of Zwicky Transient Facility observations. The only known…

We present a detailed model atmosphere analysis of hot white dwarfs in the Dark Energy Spectroscopic Instrument (DESI) Data Release 1. Our sample includes 19,321 unique targets with $G_{\rm BP}-G_{\rm RP}\leq0$. We use the DESI spectra…

We report the occurrence of a deep low state in the eclipsing short-period cataclysmic variable IR Com, lasting more than two years. Spectroscopy obtained in this state shows the system as a detached white dwarf plus low-mass companion,…

We present a near-infrared spectrum of the hot ($T_{\rm eff}$ $\approx$ 55,000 K) DA white dwarf PG 1234+482. We confirm that a very low mass companion is responsible for the previously recognised infrared photometric excess. We compare…

We report a photometric and spectroscopic study of the peculiar cataclysmic variable SDSS 1507+52. The star shows very deep eclipses on the 67 minute orbital period, and those eclipses are easily separable into white-dwarf and hot-spot…

We report the discovery of a new detached, double white dwarf system with an orbital period of 39.8 min. We targeted SDSS J163030.58+423305.8 (hereafter J1630) as part of our radial velocity program to search for companions around low-mass…

When the accreting white dwarf in a magnetic cataclysmic variable star (mCV) has a field strength in excess of 10 MG, it is expected to synchronize its rotational frequency to the binary orbit frequency, particularly at small binary…

In the light of the recent and unexpected discovery of a brand new type of white dwarfs, those with carbon-dominated atmospheres, we examine the asteroseismological potential of such stars. The motivation behind this is based on the…

We present results of observations and analysis of five WZ-type dwarf novae: SDSS J080434.20+510349.2, SDSS J102146.44+234926.3, V1108 Her, ASAS J0025 and WZ Sge in 3 - 7 years after their outbursts. We found: 1) the observational evidences…

Intermediate resolution spectroscopy of the white dwarf SDSSJ104341.53+085558.2 contains double-peaked emission lines of CaII8498,8542,8662 and identifies this object to be the second single white dwarf to be surrounded by a gaseous disc of…

White dwarf stars are traditionally found to have surface compositions made primarily of hydrogen or helium. However, a new family has recently been uncovered, the so-called Hot DQ white dwarfs, which have surface compositions dominated by…

We use the new ZZ Ceti stars (hydrogen atmosphere white dwarf variables; DAVs) discovered within the Sloan Digital Sky Survey (Mukadam et al. 2004) to re-define the empirical ZZ Ceti instability strip. This is the first time since the…

Extremely low mass white dwarfs are very rare objects likely formed in compact binary systems. We present MMT optical spectroscopy of 42 low mass white dwarf candidates serendipitously discovered in a survey for hypervelocity B-type stars.…

Little observational data are available on the weak stellar winds of hot subdwarf stars of B spectral type (sdB). Close binary systems composed of an sdB star and a compact object (white dwarf, neutron star or black hole) could be detected…

We present the direct-imaging discovery of a substellar companion (a massive planet or low-mass brown dwarf) to the young, $\gamma$ Doradus-type variable star, HIP 39017 (HD 65526). The companion's SCExAO/CHARIS JHK ($1.1-2.4\mu$m) spectrum…