[en] It is shown that the secondary components of cataclysmic binaries with orbital periods of less than 10 hours are indistinguishable from ordinary low-mass main-sequence stars and that, therefore, they are essentially unevolved. On the other hand, it is shown that, depending on the mass ratio of the progenitor system, the secondary of a cataclysmic binary could be significantly evolved. The fact that nevertheless most of the observed secondaries are essentially unevolved can be accounted for by assuming that the probability distribution for the initial mass ratio is not strongly peaked towards unity mass ratio. (Auth.)

[en] New photometric and spectroscopic observations of the nova-like variable V795 Her are reported. A period of 0.1164865(4) days for the light curve variation, and a 0.1082648(3) day period with an amplitude of 70 + or - 20 km/s for the radial velocity variation were established, which leads to the conclusion that the photometric and spectroscopic periods are different. It is argued that V795 Her is an intermediate polar and that one period is the orbital, identified as spectroscopic, and the other is associated with the rotation of the magnetized, accreting white dwarf. It is suggested that the photometric period is the beat period between the orbital period and the rotation period of the white dwarf. The orbital period of V795 Her is near the middle of the gap in the orbital period distribution for cataclysmic variables. Two possibilities for the evolutionary state of V795 Her are examined. 33 refs

No abstract available

[en] A sample of stars which are either known or are good candidates for being halo cataclysmic variables has been isolated. This sample consists of 84 stars of which 57 are dwarf novae (two of these are probable DQ Her systems), 12 are novalike stars, seven are AM Her objects, and eight are classical novae. Periodicities are known for 27 of the systems. If these stars are indeed halo members, then their distances range from 350 pc to 8 kpc and they represent objects that should be significantly older than their disk counterparts. If they do not represent true halo members, then they are intrinsically very faint systems (Mv greater than +10). Comparing the gross properties of this sample to those for the disk cataclysmic variables, it is found that below the period gap, the mean outburst amplitude for the halo dwarf novae is 3 mag greater than for the disk dwarf novae. For systems with periods less than 4 h, the halo cataclysmic variables have a higher percentage of systems below the period gap than the disk cataclysmic variables. The implications of these findings are discussed, as well as possible sample biases and selection effects. 48 refs

[en] LIGO’s third observing run (O3) has reported several neutron star–black hole (NSBH) merger candidates. From a theoretical point of view, NSBH mergers have received less attention in the community than either binary black holes, or binary neutron stars. Here we examine single–single (sin–sin) gravitational wave (GW) captures in different types of star clusters—galactic nuclei, globular clusters, and young stellar clusters—and compare the merger rates from this channel to other proposed merger channels in the literature. There are currently large uncertainties associated with every merger channel, making a definitive conclusion about the origin of NSBH mergers impossible. However, keeping these uncertainties in mind, we find that sin–sin GW capture is unlikely to significantly contribute to the overall NSBH merger rate. In general, it appears that isolated binary evolution in the field or in clusters, and dynamically interacting binaries in triple configurations, may result in a higher merger rate.

[en] We present a brief summary of the outburst for a nova that was discovered in November 1987 and has been followed since that time. Although we were able to observe it with the IUE at maximum, its ultraviolet energy faded rapidly and after the first two weeks we were no longer able to observe it at IUE wavelengths. It was observed to form a thick dust shell and currently is in the nebular stage

[en] We present preliminary results ol the optical photometric and spectroscopic monitoring ol the young eruptive variable star PV Cephei, performed during its recent conspicuous lading in 2008-2009, and try to find the reasons of the observed variations.

[en] Many B and V plates have been exposed in the past at Asiago on the field of Nova Cygni 1970. We have used this material to investigate the photometric properties of 36 ascertained or suspected variable stars. Amplitudes, types and ephemerides are derived from 85 B and 47 V plates

[en] Important progress has been made in the last few years in the understanding of the complex phenomena occurring in cataclysmic variables. An outstanding contribution to these advances has been provided by observations with the International Ultraviolet Explorer. The most recent results obtained in the specific cases of classical nove, old novae and recurrent novae are reviewed

[en] We present observations and analysis of the August 1987 outburst of the recurrent nova V394 CrA. This nova was extremely fast and its outburst characteristics closely resembled those of the Recurrent Nova U Sco. In addition to the observations, we have performed hydrodynamic simulations of the outbursts of recurrent novae and present a summary of these results as applied to the outbursts of V394 CrA and U Sco