Related papers: VY Scl-Type Star V504 Cen
We report the discovery of the first variable extreme horizontal branch star in a globular cluster (omega Cen). The oscillation uncovered has a period of 114 s and an amplitude of 32 mmags. A comparison between horizontal branch models and…
We combine archival spectral observations of the LBV star V532 (Romano's star) together with the existing photometric data in the B band. Spectroscopic data cover 15 years of observations (from 1992 to 2007). We show that the object in…
We report the discovery of a new 13th magnitude variable in Cassiopeia close to the variable KP Cas. Analysis of 6 days of intensive photometry shows a regular, near sinusoidal modulation with an amplitude of 0.024 magnitudes and a period…
We report optical time-resolved photometry of the CRTS transient CSS091109:035759+102943. Pronounced orbital variability with a 114 min period, large X-ray variability and the IR to X-ray spectral energy distribution suggest a…
The magnetic Ap or CP2 stars are natural atomic and magnetic laboratories and ideal testing grounds for the evaluation of model atmospheres. CP2 stars exhibiting photometric variability are traditionally referred to as alpha2 Canum…
The star V2282 Sgr is positionally consistent with a strong Chandra X-ray and a Spitzer/IRAC MIR source. We derived its long term $I$-band light curve from the photographic archives of the Asiago and Catania Observatories, covering the…
The Quintuplet cluster is one of the most massive star clusters in the Milky Way, situated very close to the Galactic center. We present a new search for variable stars in the vicinity of the cluster, using the five-year database of the…
The R Coronae Borealis (RCB) stars are cool supergiants that display irregular and deep dips in their light curves, caused by dust formation. There are four known hot RCB stars (DY Cen, MV Sgr, V348 Sgr, and HV 2671), with surface…
We have performed a careful investigation of the 74 candidate variable stars presented by Safanova & Stalin (2011). For this purpose we used our data base of imaging and light curves from Arellano Ferro et al. (2011) and Arellano Ferro et…
RV Tauri variable stars are pulsating evolved stars that are identified by a characterizing feature in their light curves: alternating deep and shallow minima. Many RV Tauri variable stars were originally classified decades ago using visual…
The number of known variable stars has increased by several magnitudes over the last decade, and automated classification routines are becoming increasingly important to cope with this development. Here we show that the "upside-down CBH…
The R Coronae Borealis (RCB) Star, V854 Cen, was not discovered until the 1980's even though it is 7th magnitude at maximum light. This is because it was in a faint state due to the presence of thick circumstellar dust clouds for nearly a…
We present results of time series photometry to search for variable stars in the field of metal-poor globular cluster NGC 4590 (M68). Periods have been revised for 40 known variables and no significant changes were found. A considerable…
We present the results of fast spectrophotometry of flares on the RS CVn-type star AR Lac with a time resolution of 34 s and a spectroscopic resolution R $\sim $ 1300. The observations were performed on July 21-22, 2021 with the 2.0 m Karl…
We report on the discovery of a luminous blue variable (LBV) lying ~7 pc in projection from the Quintuplet cluster. This source, which we call LBV G0.120-0.048, was selected for spectroscopy owing to its detection as a strong source of…
We present new BV CCD photometry, light curves, and ephemerides for 9 previously known, 29 newly detected RR Lyrae variables and one newly detected variable of an unknown type in the globular cluster M75. The photometry used for the…
We observed 36 evolved stars in the Small Magellanic Cloud (SMC) using the low-resolution mode of the Infrared Spectrograph (IRS) on the Spitzer Space Telescope. Two of these stars, MSX SMC 014 and 155, have nearly featureless spectral…
We report a $30~\mathrm{ks}$ $Chandra$ ACIS-S survey of the globular cluster M3. Sixteen X-ray sources were detected within the half-light radius ($2.3'$) with $L_X \gtrsim 2.3 \times 10^{31}~\mathrm{erg~s^{-1}}$. We used…
We obtained time-series radial velocity spectroscopy of twenty cataclysmic variable stars, with the aim of determining orbital periods P_orb. All of the stars reported here prove to have P_orb > 3.5 h. For sixteen of the stars, these are…
We report evidence for a new class of variable star, which we dub millimagnitude RR Lyrae (mmRR). From K2 observations of the globular cluster M4, we find that out of 24 horizontal branch stars not previously known to be RR Lyrae variables,…