Astronomers working with the Spektr-RG X-ray space observatory compiled the first catalog of events of the tidal disruption of stars by supermassive black holes. It includes 13 events that are interpreted as the formation of an accretion disk with a near-critical or supercritical regime of accretion of stellar matter onto black holes with masses from 103 to 108 solar masses.
Astronomers compiled a catalog of 13 tidal disruption events
Tidal Disruption Events
Tidal disruption events occur when a star flies close enough to a black hole for tidal forces to destroy it. In this case, some of the star’s matter is thrown away, and the rest forms an accretion disk around the black hole.
What does an observer of such events see?
An observer of such events first sees a flash of soft X-ray radiation, and then in the optical spectrum. Events of this kind make it possible to understand the modes of accretion of matter onto black holes and the properties of supermassive black holes with masses of up to 10 8 solar masses in the nuclei of galaxies.
Catalog of tidal disruption events
A group of astronomers from Russia, Germany, the Netherlands, and the United States, led by Sergei Sazonov from the Laboratory of Experimental Astrophysics of the Institute for Space Research, RAS, has published the first catalog of events of tidal disruption of stars by supermassive black holes.
Timeline of the study
The events were detected by the eROSITA X-ray telescope of the Spektr-RG space observatory at the time of its second (from scheduled eight) sky surveys from June 10 to December 14, 2020. The data from the space observatory are confirmed by ground-based optical observations.
The most distant tidal disruption event, SRG J163831.7 + 534020, has a redshift of 0.581, and the maximum glow duration among the events found is for SRGE J144738.4 + 671821, it is at least six months.
The X-ray spectra of the observed events can be described in terms of the model of a typical accretion disk with a near-critical or supercritical regime of accretion of matter onto black holes with masses from 10 3 to 10 8 solar masses.
Scientists estimate that the overall frequency of occurrence of X-ray events of tidal disruption of stars by supermassive black holes is 1.1 × 10-five events per galaxy per year, which is an order of magnitude lower than earlier estimates for optical events of tidal destruction.
If this discrepancy is due to the fact that bright X-ray events of this kind constitute a minority of all observed events, then this is proved by theoretical models that predict a strong dependence of the properties of tidal disruption events on the viewing angle – X-rays can be observed only from directions close to the axis of a thick accretion a disk formed from the matter of a destroyed star.
Further observations of Spectra-RG will make it possible to clarify the constraints both on the properties of populations of supermassive black holes and intermediate-mass black holes and on the model of near-critical and supercritical accretion onto such objects.
More about Spectr-RG
Spectr-RG has been observing since October 2019 and is to compile record-breaking detailed maps of the sky in the soft and hard X-ray ranges. The device is equipped with two telescopes: the Russian ART-XC and the German eROSITA, which are installed on the Russian Navigator platform.
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• Nowakowski, T. (2021, August 12). Spektr-RG spacecraft detects its first tidal DISRUPTION EVENTS. Phys.org.
• Sazonov, S., Gilfanov, M., Medvedev, P., Yao, Y., Khorunzhev, G., Semena, A., Sunyaev, R., Burenin, R., Lyapin, A., Mescheryakov, A., Uskov, G., Zaznobin, I., Postnov, K. A., Dodin, A. V., Belinski, A. A., Cherepashchuk, A. M., Eselevich, M., Dodonov, S. N., Grokhovskaya, A. A., … Kulkarni, S. (2021, August 5). First tidal DISRUPTION Events discovered BY SRG/eROSITA: X-ray/optical properties and X-ray luminosity function at z<0.6. arXiv.org.