Related papers: Does the period of BE Lyncis really vary?
Classical Cepheids are a cornerstone class of pulsators, fundamental to testing stellar evolution and pulsation theories. Their secular period changes, characterized through $O-C$ (Observed minus Calculated) diagrams, offer valuable…
A detailed light curve analysis is presented for a first-overtone RR Lyrae star, MACHO* J050918.712-695015.31, based on MACHO and OGLE-III observations. As a foreground object of the Large Magellanic Cloud, it gives an extraordinary…
The LMC star BI 108 is photometrically variable with the unique light curve: Two strong periods are present in a strict 3:2 resonance, staying coherent over several observing seasons. A spectroscopic data collected at VLT/UVES reveals…
We present a new period study and light-curve solutions for the A-Type W UMa binary GSC 3208 1986. Contrary to a previous claim by R.G. Samec et al. of a rapidly decreasing period, the system's period is increasing moderately on a timescale…
We present the results of recent long-term BVRcIc photometric monitoring of the type II Cepheid prototype W Virginis. These new observations, made during the 2006 and 2007 observing season, represent the longest homogeneous, multicolor…
New CCD observations of the pre-cataclysmic binary HW Virginis are presented and discussed. The R-filtered CCD photometry was supplemented with medium-band (Cousins VRI) spectrophotometry based on low-resolution objective-prism spectra. The…
We compared period changes derived from O-C diagrams for 63 classical Cepheids from our Galaxy with model calculations. We found that for Cepheids with log P > 1.0 the observed changes are smaller than predicted values, except variable SZ…
Recent studies have shown that the irregular O-C variations observed in many non-Blazhko RR Lyrae stars may result from random, cycle-to-cycle (C2C) variations in their light curves. However, centuries-long data series reveal that the O-C…
BE Lyncis (BE Lyn) is a well-studied high-amplitude $\delta$ Scuti variable star (HADS). Recently, Niu et al. (2026) analyzed a 39-year baseline of times of maximum light of BE Lyn, reporting that it is the most eccentric binary known ($e…
Secular period variations, $\beta=\dot{P}$, in 76 RR Lyrae stars in the globular cluster M5 are analysed using our most recent CCD $V$ photometry and the historical photometric database available in the literature since 1889. This provides…
We predict the existence of a new defect-lattice phase near the nematic - smectic-C (NC) transition. This tilt- analogue of the blue phase is a lattice of double-tilt cylinders. We discuss the structure and stability of the cone phase. We…
This chapter presents an overview of the properties of a Bose-Einstein condensate (BEC) trapped in a periodic potential. This system has attracted a wide interest in the last years, and a few excellent reviews of the field have already…
Photometric data for 593 Cepheids in the LMC, measured by Udalski et al. in the OGLE survey, augmented by 92 longer period Cepheids from other sources, are analyzed for the P-C and P-L relations, and for the variations of amplitude, light…
We have analysed publicly available MACHO observations of 6833 variable stars in the Large Magellanic Cloud, classified as eclipsing binaries. After finding that a significant fraction of the sample was misclassified, we redetermined…
Multi-color photometric light curves of NO Cam in $V$ $R_C$ and $I_C$ bands are obtained and analyzed simultaneously using the Wilson-Devinney (W-D) program. The solutions suggest that NO Cam is an A-subtype overcontact binary with its mass…
We present the results for orbital period analysis of 9 contact binaries (CBs). The photometric data analyzed in this work is collected using ARIES 1-m and 1.3-m telescopes as well as many ground and space-based photometric surveys. The…
Aims: We present a photometric study of the deeply eclipsing SW Sex-type nova-like cataclysmic variable star BH Lyn Methods: Time-resolved V-band CCD photometry was obtained for seven nights between 1999 and 2004. Results: We determined 11…
Based on photometric data obtained between 1935 and 2017, $O-C$ diagrams were built for 22 RR Lyrae stars in the globular cluster NGC 6171, leading to the discovery of secular period changes in 4 variables for which we have calculated their…
Photometrically and spectroscopically variable chemically peculiar (CP) stars are the optimum laboratories for testing the rotational evolution of main sequence stars. A vast majority of well-studied CP stars have quite steady rotational…
Classical Cepheids are not only excellent standard candles, but also invaluable tools to test stellar evolution and pulsation theories. Rates of their pulsation period change, quantified usually through $O-C$ diagrams, can be confronted…