Related papers: The light curves of the short-period variable star…
The re-analysis of the data reported by Mateo et al. (1998) allowed us to obtain a partially different set of frequencies for the 20 short period variable stars discovered in the Carina dSph galaxy. They are subdivided into 6…
Three fields covering the central part of the globular cluster Omega Cen were surveyed in a search for variable stars. We present V-band light curves for 22 periodic variables: 9 SX~Phe stars, 7 contact binaries, 5 detached or semi-detached…
Three fields located close to the center of the globular cluster Omega Cen were surveyed in a search for variable stars. We present V-band light curves for 32 periodic variables. This sample includes 10 SX Phe stars, 19 eclipsing binaries,…
We present results from a comparative study of light curves of Cepheid and RR Lyrae stars in the Galaxy and the Magellanic Clouds with their theoretical models generated from the stellar pulsation codes. Fourier decomposition method is used…
In this paper, we report on the detection of RRab stars with quasi-identical-shape light curves but period differences as large as $0.05-0.21$ d using the Galactic bulge data of the OGLE-IV survey. We have examined stars with shorter…
We present a detailed period analysis of the bright Cepheid-type variable star V1154 Cygni (V =9.1 mag, P~4.9 d) based on almost 600 days of continuous observations by the Kepler space telescope. The data reveal significant cycle-to-cycle…
Context. We investigate small-amplitude light variations in FU Ori occurring in timescales of days and weeks. Aims. We seek to determine the mechanisms that lead to these light changes. Methods. The visual light curve of FU Ori gathered by…
From the Fourier analysis of the catalogue of ~200,000 variable candidates in the OGLE-II Galactic fields, we found a sample of about 230 short-period low-amplitude variable stars. From their position in the colour-magnitude diagram and the…
We present a light curve analysis of fundamental-mode Galactic and Large Magellanic Cloud (LMC) Cepheids based on the Fourier decomposition technique. We have compiled light curve data for Galactic and LMC Cepheids in optical ({\it VI}),…
We present results of a photometric survey for variable stars in the field of the globular cluster Omega Centauri. The observed region was centered roughly on the cluster core and covered 644 arcmin^2. The cluster was monitored on 59 nights…
We report the discovery of a new group of double-periodic stars in the OGLE Galactic bulge photometry. In 38 stars identified as fundamental mode RR~Lyrae and 4 classified as the first-overtone RR~Lyrae, we detected additional shorter…
We present the results of a spectroscopic follow-up of various puzzling variable objects detected in the OGLE-III Galactic disk and bulge fields. The sample includes mainly short-period multi-mode pulsating stars that could not have been…
New CCD photometry of NGC 6366 has lead to the discovery of some variable stars. Two possible Anomalous Cepheids (or Pop II Cepheids), three long period variables, one SX Phe and one eclipsing binary have been found. Also a list of 10…
We present a comparative analysis of theoretical and observed light curves of Cepheid variables using Fourier decomposition. The theoretical light curves at multiple wavelengths are generated using stellar pulsation models for chemical…
The stellar evolution theory of massive stars remains uncalibrated with high-precision photometric observational data mainly due to a small number of luminous stars that are monitored from space. Automated all-sky surveys have revealed…
Light curves of the contact systems visible in the direction of Baade's Window have been analyzed using the first coefficients of the Fourier representation. The results confirm that the geometric contact between components is usually weak.…
CCD photometry in the V band is presented for 7 field RR Lyrae stars selected from a sample of eight variables which, according to data collected in the literature, are expected to be {\it ab}-type pulsators, to have short periods and hence…
FU Orionis-type stars form a small class of variable Young Stellar Objects, defined by an optical outburst of 5-6 mag followed by gradual fading on a timescale of decades. Since the phenomenon is connected to the circumstellar medium the…
Context. X-ray flares are common phenomena in pre-main sequence stars. Their analysis gives insights into the physics at work in young stellar coronae. The Orion Nebula Cluster offers a unique opportunity to study large samples of young low…
We present the discovery of a new, peculiar form of double-periodic pulsation in RR Lyrae stars. In four, long-period ($P>0.6$ d) stars observed by the Optical Gravitational Lensing Experiment, and classified as fundamental mode pulsators…