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.
Results of the spectroscopic observations at the 1.5-m Russian–Turkish telescope for another group of 12 X-ray sources discovered by the eROSITA telescope onboard the SRG space observatory and ...identified by the SRGz machine learning system as candidates for distant X-ray quasars are presented. Ten objects have been confirmed as quasars at redshifts
and two sources have turned out to be active galactic nuclei (AGNs) at
and
.
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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
We present the results of our long-term photometric and spectroscopic monitoring with the 1.5-m telescope RTT-150 for the optical counterpart of the high-mass X-ray binary IGR J21343+4738 discovered ...in 2002 by the INTEGRAL space X-ray observatory. The X-ray source was also repeatedly detected by the telescopes of the SRG observatory during the all-sky surveys in the period 2019–2021. We have investigated the spectroscopic and photometric variabilities of the optical counterpart, a Be star, caused by physical processes in the equatorial disk. The evolution of the equatorial disk parameters over a long time interval of 16 years has been analyzed.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Results of the first spectroscopic observations at the 1.5-m Russian–Turkish telescope for the X-ray sources discovered by the eROSITA telescope onboard the SRG space observatory and identified by ...the SRGz machine learning system as candidates for distant X-ray quasars are presented. Seven objects have been confirmed as quasars at redshifts
and two sources, which were included in the program of optical observations aimed at testing and adjusting SRGz and had a significant uncertainty in the photometric redshift, have turned out to be Seyfert galaxies at
.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We present the results of the optical identification, classification, and analysis of our photometric and spectroscopic observations of the X-ray transient SRGe J214919.3+673634 discovered by the ...eROSITA telescope onboard the Spectrum–Roentgen–Gamma orbital observatory in the summer of 2021 during the fourth sky survey. The photometric observations of the optical counterpart of SRGe J214919.3+673634 performed at the 6-m BTA telescope of SAO RAS, the 1.5-m Russian–Turkish telescope RTT-150, and the 2.5-m telescope of CMO SAI MSU as well the archival data from the 48-inch ZTF telescope have shown that the source is a cataclysmic variable with an orbital period
min and exhibits a long-term photometric variability from
(low state) to
(high state). We show that the light curves in the high state are consistent with the model of an accreting magnetized white dwarf and suggest that SRGe J214919.3+673634 belongs to the AM Her variables. The spectra of the optical counterpart taken in the low state at BTA are consistent with the spectral energy distribution of a white dwarf with a temperature
K.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Abstract
Bacteria and archaea employ dedicated signal transduction systems that modulate gene expression, second-messenger turnover, quorum sensing, biofilm formation, motility, host-pathogen and ...beneficial interactions. The updated MiST database provides a comprehensive classification of microbial signal transduction systems. This update is a result of a substantial scaling to accommodate constantly growing microbial genomic data. More than 125 000 genomes, 516 million genes and almost 100 million unique protein sequences are currently stored in the database. For each bacterial and archaeal genome, MiST 3.0 provides a complete signal transduction profile, thus facilitating theoretical and experimental studies on signal transduction and gene regulation. New software infrastructure and distributed pipeline implemented in MiST 3.0 enable regular genome updates based on the NCBI RefSeq database. A novel MiST feature is the integration of unique profile HMMs to link complex chemosensory systems with corresponding chemoreceptors in bacterial and archaeal genomes. The data can be explored online or via RESTful API (freely available at https://mistdb.com).
In the context of the development of the catalyst regeneration procedure via supercritical fluid CO
2
extraction, some thermodynamic properties of the anthracene–carbon dioxide mixture in ...supercritical fluid state have been studied. Data on anthracene solubility in pure and modified (dimethyl sulfoxide, 5 wt %) supercritical carbon dioxide (SC–CO
2
), the heat capacity of anthracene and its mixtures with carbon dioxide, and the heat of solution of anthracene in SC–CO
2
are presented. Anthracene solubility in SC–CO
2
is described satisfactorily using the Peng–Robinson equation of state.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This article is a survey of covering group theorems and their applications. For a given covering mapping from the topological space onto a topological group, it is natural to pose the following ...question on the lifting of the group structure from the base of the covering mapping to its covering space: do there exist group operations on the covering space that turn this space into a topological group and the original covering mapping into a morphism of topological groups? Each statement giving the positive answer to this question for any class of covering mappings is called a covering group theorem. Here the main stages in the proof of the covering group theorem for finite-sheeted covering mappings from connected topological spaces onto arbitrary compact connected groups are explored. This theorem and the method of its proof have a number of interesting applications in analysis, topology, and topological algebra. The results on the coverings of topological groups obtained by applying this theorem or by using an approximation construction which is built in its proof are discussed. The theorems under study are those establishing a close relationship between the finite-sheeted coverings of compact connected Abelian groups and the polynomials over Banach algebras of continuous functions, i.e., Weierstrass polynomials. Informally speaking, all finite-sheeted coverings of compact connected Abelian groups are defined by zero sets of simple Weierstrass polynomials. Connected coverings of P-adic solenoids are considered. A complete description of such finite-sheeted coverings is provided by using the above-mentioned approximation construction. Applications of the covering group theorems are specified, as well as their corollaries to the study of the structure of coverings and to the problem with the existence of generalized means on topological groups. Particular attention is paid to the applications related to the properties of the solutions of algebraic equations with continuous coefficients.
The article discusses the features of the new version of the "State Program for the Development of Agriculture and Regulation of Agricultural Products, Raw Materials, and Food Markets," which was ...developed as a pilot program based on project management principles. An analysis is given of the shortcomings of the State Program in terms of its target block and structure. A risk assessment of its implementation is provided. The author argues that the systemic deficiencies of the State Program, and of Russia's entire federal program framework, are caused by the frequent revision of the regulatory framework used to develop, implement, and assess the effectiveness of government programs.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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