Related papers: The Continuing Slow Decline of AG Pegasi
We analyze $\sim$32 years of optical spectra and photometry for the symbiotic binary PU Vul. Light curves for the He I $\lambda$4471, He II $\lambda$4686 and H$\beta$ $\lambda$4861 emission lines reveal an illumination effect, where the hot…
The UV and optical spectra from the HST FOS and from the FAST spectrograph at the Whipple Observatory at different phases are analysed, leading to new results about the configuration of AG Peg. Consistent modelling by the code SUMA, which…
We describe a non-LTE photoionization code to calculate the wind structure and emergent spectrum of a red giant wind illuminated by the hot component of a symbiotic binary system. We consider spherically symmetric winds with several…
The star EZ Peg, long ago classified as cataclysmic variable, has been shown to be a chromospherically active binary system of the RS CVn-type. In this paper we have analysed, using the spectral subtraction technique, simultaneous…
We present the results of an extensive campaign of coordinated X-ray (ROSAT) and UV (IUE) observations of the symbiotic star AG Dra during a long period of quiescence (1990-1993) followed by two optical outbursts in 1994 and 1995. The hot…
We present an analysis of spectrophotometric observations of the latest cycle of activity of the symbiotic binary Z And from 2006 to 2010. We estimate the temperature of the hot component of Z And to be \approx 150000 - 170000 K at minimum…
Long slit spectra of the region around the Luminous Blue Variable AG Car obtained in June 1990, just before the onset of its new brightening phase, indicate that AG Car was in the hottest phase so far recorded. The spectrum shows strong…
We present the results of new CCD photometry for the contact binary BX Peg, made during three successive months beginning on September 2008. As do historical light curves, our observations display an O'Connell effect and the November data…
We analyze a roughly 20 yr set of spectroscopic observations for the symbiotic binary EG And. Radial velocities derived from echelle spectra are best-fit with a circular orbit having orbital period P = 483.3 +- 1.6 days and semi-amplitude K…
In the optical, the spectrum of symbiotic binaries consists of contributions from the cool giant, symbiotic nebula and the hot star. Strong emission lines are superposed on the continuum. In this paper we introduce a simple method to…
In the summer and fall of 2000 the yellow hypergiant Rho Cassiopeiae dimmed by more than a visual magnitude, while its effective temperature decreased from \~7000 K to below 4000 K over ~200 d. We observed the highest mass-loss rate of ~5 %…
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…
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…
Betelgeuse is a pulsating red supergiant whose brightness is semi periodically variable and in February 2020 reached a historical minimum, the Great Dimming. The aims of this study are to characterize Betelgeuse's variability based on…
Optical spectroscopy study of the recent AG Peg outburst observed during the second half of 2015 is presented. Considerable variations of the intensity and the shape of the spectral features as well as the changes of the hot component…
OO Peg is a detached eclipsing binary system containing two late-A-type stars in a circular orbit with a period of 2.985 d. Using published spectroscopic results and a light curve from the Transiting Exoplanet Survey Satellite (TESS) we…
The recent 1994-1995 active phase of AG Draconis has given us for the first time the opportunity to follow the full X-ray behaviour of a symbiotic star during two successive outbursts and to compare with its quiescence X-ray emission. With…
Variations of the emission lines in the spectrum of the yellow symbiotic star AG Dra have been studied for over 14 years (1997 - 2011), using more than 500 spectra obtained on the 1.5-metre telescope at Tartu Observatory, Estonia. The time…
We present a detailed spectroscopic analysis of the luminous blue variable AG Carinae during the last two visual minimum phases of its S-Dor cycle (1985-1990 and 2000-2003). The analysis reveals an overabundance of He, N, and Na, and a…
We have obtained high resolution X-ray spectra of the coronally active binary, II Pegasi (HD 224085), covering the wavelength range of 1.5-25 Angstroms. For the first half of our 44 ksec observation, the source was in a quiescent state with…