Related papers: AM CVn -- System Parameters and Gravitational Wave…
We study the gravitational wave emission from the first stars which are assumed to be Very Massive Objects (VMOs). We take into account various feedback (both radiative and stellar) effects regulating the collapse of objects in the early…
We present new multiband CCD photometry for AA UMa made on 8 nights between January and March 2009; the $R$ light curves are the first ever compiled. Historical light curves, as well as ours, display partial eclipses and inverse O'Connell…
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…
Binary post-asymptotic giant branch (post-AGB) stars are thought to be the products of a strong but poorly-understood interaction during the AGB phase. The aim of this contribution is to update the orbital elements of a sample of galactic…
We report observational upper limits on the mass-energy of the cosmological gravitational-wave background, from limits on proper motions of quasars. Gravitational waves with periods longer than the time span of observations produce a simple…
We present the analysis of the spectroscopic observations of a newly discovered cataclysmic variable HS0551+7241. In 1995 the star's brightness dropped by Delta(B)~2.5 mag and HS0551+7241 entered a low state lasting for ~2 yr. The H-alpha,…
We used very long baseline interferometry to constrain the orbit of the binary system 2MASS J05082729-2101444. We observed the system with the VLBA in three epochs at a frequency of 4.85 GHz, which provides an angular resolution of about 3…
We present results obtained from a series of 5~\AA\ resolution spectra of the X-ray Nova GRO~J0422+32 obtained in 1993~October, when the system was approximately 2 magnitudes above quiescence, with ${\rm R \sim 19}$. The data were obtained…
New photometry, including TESS data, have been combined with recent spectroscopic observations of the Orion Ib pulsating triple-star system VV Ori. This yields a revised set of absolute parameters with increased precision. Two different…
In a well-aimed search based on the recently published Gaia~DR2 radial velocity data and performed with the robotic TIGRE telescope, we have discovered 19 bright ($m_V<7.66$~mag) spectroscopic binary stars. We present the radial velocity…
We report the detection of eclipses in LSPM J1112+7626, which we find to be a moderately bright (I_C = 12.14 +/- 0.05) very low-mass binary system with an orbital period of 41.03236 +/- 0.00002 days, and component masses M_1 = 0.395 +/-…
Recent papers published in the last years contributed to resolve the enigma on the hypothetical Be nature of the hot pulsating star $\beta$ Cep. This star shows variable emission in the H$\alpha$ line, typical for Be stars, but its…
New high-resolution spectra, of the chromospherically active binary system CF Tuc, taken at the Mt. John University Observatory in 2007, were analyzed using two methods: cross-correlation and Fourier--based disentangling. As a result, new…
We present results of a 2014-2018 campaign of radial velocity measurements of $\delta$ Ceti. Combining our determination of pulsation period with historical data we conclude that the most likely explanation of observed changes is the…
Close white dwarf - red dwarf binaries must have gone through a common-envelope phase during their evolution. DE CVn is a detached white dwarf - red dwarf binary with a relatively short (~8.7 hours) orbital period. Its brightness and the…
The rate of gravitational-wave energy loss from inspiralling binary systems of compact objects of arbitrary mass is derived through second post-Newtonian (2PN) order $O[(Gm/rc^2)^2]$ beyond the quadrupole approximation. The result has been…
A careful investigation of a CCD spectrum of the SB1 system kappa Cnc in the spectral region 3800 A - 8000 A resulted in the discovery of the lines of the secondary star. We then analyzed several short-wavelength range Reticon spectra…
We present results of our analysis of up to 15 years of photometric data from eight AM CVn systems with orbital periods between 22.5 and 26.8 min. Our data has been collected from the GOTO, ZTF, Pan-STARRS, ASAS-SN and Catalina all-sky…
Previous heat-capacity measurements of our group had shown the possible existence of an anomalous quantum phase containing the zero-point vacancies (ZPVs) in 2D $^{3}$He. The system is monolayer $^{3}$He adsorbed on graphite preplated with…
More than 20 pre-cataclysmic variable (pre-CV) systems have now been discovered with very short orbital periods ranging from 250 min down to 68 min. A pre-CV consists of a white dwarf or hot subdwarf primary and a low-mass companion star,…