Related papers: The Everchanging Pulsating White Dwarf GD358
Aims. We use the Kepler data accumulated on the pulsating DB white dwarf KIC 08626021 to explore in detail the stability of its oscillation modes, searching in particular for evidences of nonlinear behaviors. Methods. We analyse nearly two…
The {\it Microvariability and Oscillations of Stars (MOST)} satellite observed the B supergiant HD 163899 (B2 Ib/II) for 37 days as a guide star and detected 48 frequencies $\la$ 2.8 c d$^{-1}$ with amplitudes of a few milli-magnitudes…
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…
For many years, astronomers have promised that the study of pulsating white dwarfs would ultimately lead to useful information about the physics of matter under extreme conditions of temperature and pressure. In this paper we finally make…
We present here optical I-band photometric variability study down to $\simeq$ 19 mag of a young ($\sim$2-3 Myr) star-forming region IC 348 in the Perseus molecular cloud. We aim to explore the fast rotation (in the time-scales of hours) in…
Globular clusters contain a unique pulsar population, with many exotic systems that can form only in their dense stellar environments. The leap in sensitivity of the upgraded Giant Metrewave Radio Telescope (uGMRT) in India, especially at…
WD 1145+017 was observed from 2015 November to 2016 July for the purpose of characterizing transit behavior of the white dwarf by dust clouds thought to be produced by fragments of an asteroid in close orbit with the star. Fortuitously,…
We report the discovery of a detached 20 min orbital period binary white dwarf. WD0931+444 (SDSS J093506.93+441106.9) was previously classified as a WD + M dwarf system based on its optical spectrum. Our time-resolved optical spectroscopy…
We report the results of photometry of the intermediate polar V647 Aur. Observations were obtained over 42 nights in 2012 and 2013. The total duration of the observations was 246 h. We clearly detected three oscillations with periods of…
We present the results of the first theoretical non-radial non-adiabatic pulsational study of M dwarf stellar models with masses in the range 0.1 to 0.5M_solar. We find the fundamental radial mode to be unstable due to an \epsilon mechanism…
We have discovered periodic variations in the light curves of two hot DQ stars from the Sloan Digital Sky Survey, SDSS J220029.08-074121.5 and SDSS J234843.30-094245.3. These are the second and third variables detected among the hot DQs and…
The RApid Temporal Survey (RATS) is a survey to detect objects whose optical intensity varies on timescales of less than ~70 min. In our pilot dataset taken with the INT and the Wide Field Camera in Nov 2003 we discovered nearly 50 new…
We have conducted a long-term V-band photometric monitoring of M33 on 95 nights during four observing seasons (2000 - 2003). A total number of 6418 lightcurves of bright objects in the range of 14 - 21 mag have been obtained. All…
Recent re-determination of stellar atmospheric parameters for a sample of stars observed during the {\it Kepler} mission allowed to enlarge the number of {\it Kepler} B-type stars. We present the detailed frequency analysis for all these…
We made photometric and spectroscopic observations of the rapidly pulsating subdwarf B star EC 09582-1137 with the aim of determining the target's fundamental structural parameters from asteroseismology. The new data comprise ~ 30 hours of…
We report high resolution optical speckle observations of 336 M dwarfs which result in 113 measurements of relative position of 80 systems and 256 other stars with no indications of duplicity. These are the first measurements for two of the…
We present time-resolved spectroscopy and photometry of the cataclysmic variable (CV) SDSSJ133941.11+484727.5 (SDSS1339) which has been discovered in the Sloan Digital Sky Survey Data Release 4. The orbital period determined from radial…
We discuss here the pulsation properties of the $\delta$ Scuti star BV Circini on the basis of data obtained during a simultaneous photometric and spectroscopic campaign in 1996 and a spectroscopic one in 1998, and taking also advantage of…
We present a total of 57 days of contiguous, high-cadence photometry (14 days in 2004 and 43 in 2005) of the star BD+18 4914 obtained with the MOST satellite. We detect 16 frequencies down to a signal-to-noise of 3.6 (amplitude \~ 0.5…
Rotational modulations of brown dwarfs have recently provided powerful constraints on the properties of ultra-cool atmospheres, including longitudinal and vertical cloud structures and cloud evolution. Furthermore, periodic light curves…