ABSTRACT
We present the first sample of tidal disruption events (TDEs) discovered during the SRG all-sky survey. These 13 events were selected among X-ray transients detected in the 0° < l < 180° ...hemisphere by eROSITA during its second sky survey (2020 June 10 to December 14) and confirmed by optical follow-up observations. The most distant event occurred at z = 0.581. One TDE continued to brighten at least 6 months. The X-ray spectra are consistent with nearly critical accretion on to black holes of a few ×103 to $10^8\, \mathrm{ M}_\odot$, although supercritical accretion is possibly taking place. In two TDEs, a spectral hardening is observed 6 months after the discovery. Four TDEs showed an optical brightening apart from the X-ray outburst. The other nine TDEs demonstrate no optical activity. All 13 TDEs are optically faint, with Lg/LX < 0.3 (Lg and LX being the g band and 0.2–6 keV luminosity, respectively). We have constructed a TDE X-ray luminosity function, which can be fit by a power law with a slope of −0.6 ± 0.2, similar to the trend observed for optically selected TDEs. The total rate is estimated at (1.1 ± 0.5) × 10−5 TDEs per galaxy per year, an order of magnitude lower than inferred from optical studies. This suggests that X-ray bright events constitute a minority of TDEs, consistent with models predicting that X-rays can only be observed from directions close to the axis of a thick accretion disc formed from the stellar debris. Our TDE detection threshold can be lowered by a factor of ∼2, which should allow a detection of ∼700 TDEs by the end of the SRG survey.
ABSTRACT
The examination of long-term (1979–2020) photometric observations of SS433 enabled us to discover a non-zero orbital eccentricity of e = 0.05 ± 0.01. We have also found evidence for a ...secular increase in the orbital period at a rate of $\dot{P}_\mathrm{b}=(1.0\pm 0.3)\times 10^{-7}$ s s−1. The binary orbital period increase rate makes it possible to improve the estimate of the binary mass ratio q = MX/MV > 0.8, where MX and MV are the masses of the relativistic object and the optical star, respectively. For an optical star mass of 10 M⊙, the mass of the relativistic object (a black hole) is MX > 8 M⊙. A neutron star in SS433 is reliably excluded because in that case the orbital period should decrease, in contradiction to observations. The derived value of $\dot{P}_\mathrm{b}$ sets a lower limit on the mass-loss rate in the Jeans mode from the binary system ≳7 × 10−6 M⊙ yr−1. The discovered orbital ellipticity of SS433 is consistent with the model of the slaved accretion disc tracing the precession of the misaligned optical star’s rotational axis.
The discovery in 1962 of the compact source Sco X-1, the first X-ray source located outside the Solar System, marked a new (“golden”) era in the study of close binary systems (CBSs). Soon after, ...accreting neutron stars and first black hole candidates in CBSs were discovered. The ability to “weigh” neutron stars and black holes in CBSs made it possible to distinguish accreting black holes from neutron stars. The theory of accretion onto relativistic objects in CBSs has been developed, as well as the theory of the evolution of CBSs with mass exchange up to the latest stages, including binary black holes and neutron stars. CBSs have become the cutting edge of astrophysics. Subsequent observations of gravitation waves and observations with the EHT intercontinental radio interferometer with an angular resolution of ~10
–5
arcsec made it possible to finally prove the existence of black holes in the Universe. Thus, the modern triumph of black holes has largely been due to the development of the science of CBSs. This paper is based on a presentation made in the astrophysical memorial seminar “Novelties in Understanding the Evolution of Binary Stars”, dedicated to the 90th anniversary of Professor M.A. Svechnikov.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A review of close binary systems (CBSs) in the late stages of evolution is presented. High-mass and low-mass CBSs are described separately: WR+OB systems, “quiet” X-ray binaries, massive transient ...X-ray binaries with Be stars, X-ray novae and bursters, cataclysmic and symbiotic binaries. Luminous blue variables (LBV objects) and radio pulsars in binary systems are discussed. Black holes in binary stellar systems, methods for their search, and black hole masses in X-ray binary systems are described. A number of specific systems are analyzed. The mass distribution of relativistic objects, WR stars, and their CO cores in binary systems is described. The masses of stellar black holes and the possibility of testing the theories of gravity are discussed. Possible variations in the orbital periods of X-ray binaries due to enhanced quantum evaporation of black holes are presented.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The paper analyzes observations of close binary systems (CBSs), their radial velocity curves, and light curves. Various methods are described for fitting the light curve of eclipsing systems that ...consist of two spherical stars in a circular or elliptical orbit, as well as methods for considering the third light and the influence of a third body on the times of minima, and rectifying the light curves of eclipsing systems. The rotation of the apsidal line in a CBS is considered, as well as its use for determining the concentration of matter in the star’s body. Possible mechanisms for variation in the orbital eccentricity in CBSs, the causes of variation in their orbital periods, and the effects of the mutual proximity of the components are discussed.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The paper gives an overview of parametric models in inverse problems of astrophysics. The statistical formulation of the finite-parametric inverse problem, the testing of statistical hypotheses, and ...the construction of confidence regions are described. The cases of linear and nonlinear parameters are considered. Astrophysical applications of the methods and practical recommendations for their application are given. Estimation of parameter errors is described for the case of a classical close binary system. A numerical experiment for assessing the reliability of the differential correction method, Monte Carlo method, and confidence region method is analyzed. The observed light curve is analyzed using the classical eclipsing system YZ Cas as an example. The determination of the limb darkening coefficient for the components of this system is described. The error intervals obtained using the
and
statistics are compared with the differential correction method.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The article considers a variety of close binary systems (CBSs) and describes their classification. Statistical dependences between the main parameters of the CBS stellar components are presented. The ...star formation function for binary stars in the Galaxy is described, and the question of the formation of binary and multiple systems is discussed. Studies of CBSs in star clusters are presented.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The article presents an overview of eclipsing systems that contain stars with extended atmospheres. The characteristics of Wolf–Rayet stars are described. A method for interpreting the light curves ...of eclipsing systems with extended atmospheres is analyzed. The light curve of the eclipsing system V 444 Cyg is analyzed on a set of convex-concave functions. The reconstruction of the velocity field in the stellar wind of the WN5 star in the V 444 Cyg system is described using a parametric model. The light curve and characteristics of the components of the eclipsing binary WN3(h)+O5V BAT 99-129 are analyzed. The parameters of the WR star in the peculiar X-ray binary Cyg X-3, as well as the parameters and evolutionary stage of WR stars in the very massive eclipsing system WR20a (WN6ha+WN6ha) are described.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The article considers various aspects of the evolution of close binary systems (CBSs). The variation in the orbital parameters of a CBS during its evolution, including the evolution of the CBS under ...the influence of the magnetic stellar wind and the gravitational wave radiation, is analyzed. The evolution of CBSs with mass transfer is considered. Evolutionary scenarios for CBSs and population synthesis are discussed. Modern three-dimensional models of gas flow in interacting CBSs are presented. The collision of supersonic stellar winds in CBSs is discussed.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
PDF
