Related papers: Ellipsoidal Variability and the Difference between…

Long-term variations are well-known in Be X-ray binaries, and are attributed to non-orbital changes in the structure of the Be circumstellar (equatorial) disc. However, the timescales involved are so long (tens of days, to years) that…

Blue supergiants (BSGs) mediate between the main sequence and the late stages of massive stars, which makes them valuable for assessing the physics that drives the stars across the diverse evolutionary channels. By exploring correlations…

Excitation of radial pulsations in red supergiants of Magellanic Clouds is investigated using the stellar evolution calculations and the self-consistent solution of the equations of radiation hydrodynamics and turbulent convection. The…

The first catalog of chromospherically active and ellipsoidal variable stars in the OGLE database is presented. The periods, the observed magnitudes and colors, their values free of interstellar extinction, and Fourier coefficients of light…

We analyze the historical light curve of the symbiotic star YY Her, from 1890 up to December 2005. A secular declining trend is detected, at a rate of ~.01 magn in 1000 d, suggesting that the system could belong to the sub-class of…

There are three important aspects concerning the study of the red giant and in particular of the asymptotic giant branch (AGB) stars in the Magellanic Clouds. These are: the surface distribution, the luminosity function and the variability.…

We present ten years of new photometric monitoring of the light variability of five evolved stars with strong mid-infrared emission from surrounding dust. Three are known carbon-rich proto-planetary nebulae (PPNe) with F$-$G spectral types;…

There is a long-acknowledged deficiency of bright red giants relative to fainter old stars within a few arc seconds of Sgr A*. We explore whether this could be due to tidal stripping by the central black hole. This requires putting the…

Positions of High-Mass X-ray Binaries are often known precisely enough to unambiguously identify the optical component, and a number of those stars are monitored by the OGLE and MACHO collaborations. The light curves of two such candidates…

We present an analysis of the long-term optical/IR behavior of 111 high-mass X-ray binaries (HMXBs) in the Small Magellanic Cloud based on data from the OGLE collaboration. Most systems exhibit variability on a range of time scales. This…

We analyze the K band luminosities of a sample of galactic long-period variables using parallaxes measured by the Hipparcos mission. The parallaxes are in most cases re-computed from the Hipparcos Intermediate Astrometric Data using…

M giants are among the longest-period pulsating stars which is why their studies were traditionally restricted to analyses of low-precision visual observations, and more recently, accurate ground-based data. Here we present an overview of M…

The VMC survey is obtaining multi-epoch photometry in the Ks band of the Magellanic System down to a limiting magnitude of Ks ~ 19.3 for individual epoch data. The observations are spaced in time such as to provide optimal sampling of the…

Observations of Cepheids in the Large Magellanic Cloud, made over the last several decades, allow us to search for evolutionary period changes. None of the Cepheid from our sample of 378 stars stopped pulsating. Also none of them showed a…

Among 19 red-giant stars belonging to eclipsing binary systems that have been identified in Kepler data, 15 display solar-like oscillations. We study whether the absence of mode detection in the remaining 4 is an observational bias or…

We have used visual and Johnson V observations from the American Association of Variable Star Observers (AAVSO) International Database, and the AAVSO VSTAR time-series package, and (O-C) analysis to investigate possible changes in the…

Several classes of pulsating stars are now known to undergo slow changes in amplitude; these include pulsating red giants and supergiants, and yellow supergiants. We have used visual observations from the AAVSO International Database, and…

A single-lined spectroscopic orbit for the M giant in the X-ray binary IGR J16194-2810 is determined from a time-series of optical spectra. The spectroscopic orbital period of 192.5 days is twice that of the photometric period, confirming…

The aim of this work is to create a complete list of sources exhibiting a long secondary period (LSP) in the ASAS-SN catalog of variable stars, and analyze the properties of this sample compared to other long period variables without LSP.…

The 222~000 I-band light curves of variable stars detected by the OGLE-II survey in the direction of the Galactic Bulge have been searched for eclipsing binaries (EBs). A previously developed code to analyze lightcurve shapes and identify…