Related papers: AY Peg, a large amplitude Algol-type star
New CCD photometry during 4 successive years from 2005 is presented for the eclipsing binary GW Cep, together with reasonable explanations for the light and period variations. All historical light curves, obtained over a 30-year interval,…
Astronomical data are typically irregular in time, e.g. the space (HIPPARCOS/TYCHO, KEPLER, GAIA, WISE etc.) and ground-based CCD (NSVS, ASAS, CRTS, SuperWASP etc.) and photographic (Harvard, Sonneberg, Odessa etc.) photometrical surveys.…
The atmospheric parameters and chemical abundances of two neglected A-type stars, 28 Peg and HD 202240, were derived using high resolution spectra obtained at the TUBITAK National Observatory. We determined the photospheric abundances of…
Broad Balmer emission lines in active galactic nuclei (AGN) may display dramatic changes in amplitude, even disappearance and re-appearance in some sources. As a nearby galaxy at a redshift of z = 0.0264, Mrk 590 suffered such a cycle of…
We identify the bright Am-type star HD 181793 to be a previously-unknown eclipsing, chemically peculiar heartbeat binary, the second of its kind known. The system carries an orbital period of $P = 11.47578275 \pm 0.00000055$ days. We use…
We present time-resolved spectroscopy and photometry of the bright cataclysmic variable LS Peg (= S193). The Balmer lines exhibit broad, asymmetric wings Doppler-shifted by about 2000 km/s at the edges, while the HeI lines show…
The mysterious 3rd magnitude long period eclipsing binary star system epsilon Aurigae is predicted to be starting its 2 year eclipse in the late summer of 2009. While this is when the real excitement starts, much is to be learned before…
We present an investigation of H-alpha emission line variations observed in the massive Algol binary, RY Per. We give new radial velocity data for the secondary based upon our optical spectra and for the primary based upon high dispersion…
We present the results of a search for short-period variable stars in Leo A. We have found 92 candidate variables, including eight candidate RR Lyrae stars. From the RR Lyraes, we measure a distance modulus of (m-M)_0 = 24.51 +/- 0.12, or…
We investigate the variability properties of main sequence stars in the first month of Kepler data, using a new astrophysically robust systematics correction, and find that 60% of stars are more variable then the active Sun. We define low…
Results of a CCD study of the variability of the cataclysmic variable BG CMi obtained at the Korean 1.8m telescope in 2002-2005 are presented. The "multi-comparison star" method had been applied for better accuracy estimates. The linear…
V2492 Cyg is a young pre-main sequence star presenting repetitive brightness variations of significant amplitude (Delta R > 5 mag) whose physical origin has been ascribed to both extinction (UXor-type) and accretion (EXor-type) variability,…
Two newly identified Ae stars, nu Cyg and kappa UMa, were discovered in the course of the Magnetic Survey of Bright MS stars (Monin et al. 2002). We pre sent their Halpha profiles along with measurements of their equivalent width and…
We present an analysis of the XMM-Newton observation of the symbiotic star AG Peg, obtained after the end of its 2015 outburst. The X-ray emission of AG Peg is soft and of thermal origin. AG Peg is an X-ray source of class beta of the X-ray…
Context: Asteroseismology has great potential for the study of metal-poor stars due to its sensitivity to determine stellar ages. Aims: Our goal was to detect p-mode oscillations in the metal-poor sub-dwarf 85 Peg A and to search for other…
Young A-type stars in the pre--main-sequence (PMS) evolutionary phase are particularly interesting objects since they cover the mass range (1.5-4 solar ma sses) which is most sensitive to the internal conditions inherited during the…
We present a new study of the Algol-type eclipsing binary system AS Eri based on the combination of the MOST and TESS light curves and a collection of very precise radial velocities obtained with the spectrographs HERMES operating at the…
V347 Aurigae is associated with the small dark cloud L1438 and appears to be an isolated pre-main sequence star located at distance $d\approx$200 pc. Multi-epoch, archival photometry reveals periodic brightness variations with amplitude…
The analysis of the available TESS light curves of $\alpha$ Sex (HD 87887) reveals low-frequency pulsations with a period of about 9.1 hours in this spectroscopic A0 III standard star. The IUE observations in December 1992 reveal large flux…
We present both binarity and pulsation of KIC 6220497 from the {\it Kepler} observations. The light curve synthesis shows that the eclipsing system is a semi-detached Algol with parameters of $q$ = 0.243$\pm$0.001, $i$ = 77.3$\pm$0.3 deg,…