We have gathered optical photometry data from the literature on a large sample of Swift-era gamma-ray burst (GRB) afterglows including GRBs up to 2009 September, for a total of 76 GRBs, and present ...an additional three pre-Swift GRBs not included in an earlier sample. Furthermore, we publish 840 additional new photometry data points on a total of 42 GRB afterglows, including large data sets for GRBs 050319, 050408, 050802, 050820A, 050922C, 060418, 080413A, and 080810. We analyzed the light curves of all GRBs in the sample and derived spectral energy distributions for the sample with the best data quality, allowing us to estimate the host-galaxy extinction. We transformed the afterglow light curves into an extinction-corrected z = 1 system and compared their luminosities with a sample of pre-Swift afterglows. The results of a former study, which showed that GRB afterglows clustered and exhibited a bimodal distribution in luminosity space, are weakened by the larger sample. We found that the luminosity distribution of the two afterglow samples (Swift-era and pre-Swift) is very similar, and that a subsample for which we were not able to estimate the extinction, which is fainter than the main sample, can be explained by assuming a moderate amount of line-of-sight host extinction. We derived bolometric isotropic energies for all GRBs in our sample, and found only a tentative correlation between the prompt energy release and the optical afterglow luminosity at 1 day after the GRB in the z = 1 system. A comparative study of the optical luminosities of GRB afterglows with echelle spectra (which show a high number of foreground absorbing systems) and those without, reveals no indication that the former are statistically significantly more luminous. Furthermore, we propose the existence of an upper ceiling on afterglow luminosities and study the luminosity distribution at early times, which was not accessible before the advent of the Swift satellite. Most GRBs feature afterglows that are dominated by the forward shock from early times on. Finally, we present the first indications of a class of long GRBs, which form a bridge between the typical high-luminosity, high-redshift events and nearby low-luminosity events (which are also associated with spectroscopic supernovae) in terms of energetics and observed redshift distribution, indicating a continuous distribution overall.
Abstract
The paper proposes an algorithm for choosing the optimal voltage class of a power supply distribution grid of gas well clusters, in which there is a multiple electrical load increase during ...field’s life cycle. Building a mathematical model with considering factors allows to design both a trunk line and a single radial grid and evaluate the magnitude and direction of the influence of individual factors, i.e. to conduct a quantitative analysis of the gas field power supply diagram. An extreme experiment is used to construct mathematical models. The optimization parameter is accepted as economic-the minimum of discounted costs. The paper presents six response functions-regression equations. The distribution grids of a number of operating gas fields in Western Siberia have been investigated taking into account the entire life cycle of the field at “PRON” computer program. The proposed algorithm can be used in the design of the power supply system for new gas fields, which allows to select the optimal voltage class for the power supply system of gas clusters, considering the entire life of the gas field, taking into account the minimum discounted costs. It can improve the efficiency of decisions, reduce funds and design time.
A New Probabilistic Primality Test Moshonkin, A. G.; Khamitov, I. M.
Journal of mathematical sciences (New York, N.Y.),
10/2020, Volume:
249, Issue:
1
Journal Article
Peer reviewed
In this paper, a new general probabilistic primality test is presented. The estimated efficiency of the test turns out to be inferior to that of the Miller–Rabin test. However, some heuristic ...arguments indicate that the estimation of its efficiency is quite rough. This allows one to expect that the actual efficiency of the test is much higher.
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The Russian–Turkish 1.5-m telescope (hereafter RTT-150) takes an active part in the work on the ground optical support of observations by the Russian Spectrum–Röntgen–Gamma (SRG) observatory (with ...the participation of Germany) aimed at the identification and classification of new X-ray sources detected by the SRG telescopes. The instrumental capabilities of RTT-150 (occasionally, without any significant usage of telescope time and detriment for astrophysical programs) are used in astrometric observations to control the correction of the orbit of the SRG space observatory itself. In these cases, RTT-150 provides the Ballistic Center of the Keldysh Institute of Applied Mathematics of the Russian Academy of Sciences with high-precision astrometric measurements of the SRG position, which have been used to successfully keep it in its operational orbit for more than three years of its exploitation. Beginning from the stage of flight to the zone of the Lagrange point
in July 2019 and at the main phase of the all-sky survey mission until March 2023, 96 sets (with a duration of about 30 min each) of high-precision positional observations with more than 5000 astrometric and photometric measurements were carried out at the RTT-150 observing facility. In most cases, the positional accuracy of the measurements dependent on seeing and apparent SRG brightness agrees with the accuracy of the provided ephemerides,
and
in declination and right ascension, respectively. In the summer months in projection onto the central region of the Galaxy in fields extremely rich in sources, the astrometric accuracy is
, sufficient for the SRG detection after the corrections and subsequent refinements of its trajectory. Geographically, RTT-150 is the southernmost instrument among the Russian telescopes for the ground astrophysical support of SRG. This fact is also extremely important in positional SRG observations at the lowest positions in declination
. We present the results of our astrometric and photometric observations with RTT-150 and our astrometric data reduction technique in various fields up to those extremely rich in sources.
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Gas fields differ from industrial enterprises by long power transmission lines with low electrical loads (low density), which grow many times during the life cycle. Power supply to gas well clusters ...is carried out according to the scheme - "main circuit with one through line with transformer substations distributed along the line". The distribution of transformer substations along the transmission line affects the voltage loss, and, consequently, the choice of voltage class. The purpose of the research is to quantify the distribution of transformer substations along the power line to develop a mathematical model for calculating the optimal voltage class. To achieve this goal, the following tasks are solved: five power supply schemes are built for gas well clusters; electric moments are calculated for each scheme; the load distribution coefficient is determined. The problems were solved using an experimental-theoretical method (analysis and synthesis) and a software product - Mathcad. As a result, the coefficient is calculated in the work - for even load distribution, when placing the entire load at the end of the line and when placing the load at the beginning of the line.
This paper is an extension of the study by Khamitov et al. (2022) with regard to the catalog and the astrophysical interpretation of the imitation of significant proper motions in active galactic ...nuclei (AGNs) and quasars based on data from the Gaia space observatory. We present a sample of SRG/eROSITA X-ray sources in the eastern Galactic hemisphere (
) having significant proper motions in the Gaia EDR3 measurements with the confirmed extragalactic nature of the objects. The catalog consists of 248 extragalactic sources with spectroscopically measured redshifts. The catalog includes all of the objects available in the SIMBAD database and coincident with the identified optical counterpart within 0.5 arcsec. Eighteen sources with spectroscopically measured redshifts from observations with the Russian–Turkish 1.5-m telescope RTT-150 (Khamitov et al. 2022) have been additionally included in the catalog. The sources in the catalog are AGNs of various types (Sy1, Sy2, LINER), quasars, radio galaxies, and star-forming galaxies. The imitation of significant proper motions can be explained (by the VIM effect previously known in astrometry) by the presence of transient events on the line of sight in the vicinity of AGNs and quasars (within the Gaia optical resolution element). Among such astrophysical events are supernova outbursts, tidal disruption events in binary AGNs, the variability of high-mass supergiants, the presence of OB associations against the background of AGNs with a variable brightness, etc. The model of outbursts with a fast rise–exponential decay profile allows the variable positional parameters of most sources observed in Gaia to be described. This approach can be used as an independent way of detecting transient events in the vicinity of AGNs (on scales of several hundred parsecs in the plane of the sky) based on data from the SRG/eROSITA catalogs of X-ray sources and the optical Gaia catalog.
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We present the results of optical identifications and spectroscopic redshift measurements for galaxy clusters from the second Planck catalogue of Sunyaev–Zeldovich sources (PSZ2) located at high ...redshifts,
z
≈ 0.7−0.9. We used the data of optical observations with the Russian–Turkish 1.5-mtelescope (RTT-150), the Sayan Observatory 1.6-m telescope, the Calar Alto 3.5-m telescope, and the 6-m SAO RAS telescope (BTA). The spectroscopic redshift measurements were obtained for seven galaxy clusters, including one cluster, PSZ2 G126.57+51.61, from the cosmological sample of the PSZ2 catalogue. In the central regions of two clusters, PSZ2 G069.39+68.05 and PSZ2 G087.39−34.58, we detected arcs of strong gravitational lensing of background galaxies, one of which is at redshift
z
= 4.262. The data presented below roughly double the number of known galaxy clusters in the second Planck catalogue of Sunyaev–Zeldovich sources at high redshifts,
z
≈ 0.8.
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Abstract
The paper outlines the issue of correctly choosing the voltage class for power supply of the gas well clusters considering all periods of the life cycle of the Western Siberia gas fields. ...The voltage class incorrectly chosen at the design stage hinders the life cycle of a gas field. The paper considers the gas field process flow sheet for each period of its life cycle. Using the experimental design theory, mathematical models have been developed for calculating the optimal voltage class and discounted costs for the gas well cluster power supply system. An algorithm for choosing the optimal voltage has been developed, and an example of calculating the optimal voltage for the distribution networks of the Western Siberia gas fields is given. A progressive voltage class for the distribution networks has been proposed. Conclusions have been drawn.
Based on a comparison of the SRG/eROSITA catalog of X-ray active stars and the Gaia catalog, we have obtained a sample of 502 peculiar objects for which Gaia, on the one hand, detects statistically ...significant parallaxes or proper motions and, on the other hand, records signs of a nonzero optical extent. On the
–color diagram these objects are significantly separated from the bulk of the stars and are located in the region typical for active galactic nuclei (AGNs). According to the SIMBAD database,
of them are AGNs and galaxies with spectroscopic redshifts and only
are confirmed objects in our Galaxy. Our spectroscopic observations of 19 unidentified objects with the RTT-150 telescope have shown that 18 of them are AGNs at redshifts
0.01–0.3 and one object is an M star in our Galaxy. We discuss various scenarios for the appearance of such peculiar objects.
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We describe the methods of the SRGz system for the physical identification of eROSITA point X-ray sources from photometric data in the DESI Legacy Imaging Surveys footprint. We consider the models ...included in the SRGz system (version 2.1) that have allowed us to obtain accurate measurements of the cosmological redshift and class of an X-ray object (quasar/galaxy/star) from multiwavelength photometric sky surveys (DESI LIS, SDSS, Pan-STARRS, WISE, eROSITA) for 87
of the entire eastern extragalactic region (
,
). An important feature of the SRGz system is that its data handling model (identification, classification, photo-z algorithms) is based entirely on heuristic machine learning approaches. For a standard choice of SRGz parameters the optical counterpart identification completeness (recall) in the DESI LIS footprint is
(with an optical counterpart selection precision of
); the classification completeness (recall) of X-ray sources without optical counterparts in DESI LIS is
(
precision). A high quality of the photometric classification of X-ray source optical counterparts is achieved in SRGz:
photometric classification completeness (recall) for extragalactic objects (a quasar or a galaxy) and stars on a test sample of sources with SDSS spectra and GAIA astrometric stars. We present an analysis of the importance of various photometric features for the optical identification and classification of eROSITA X-ray sources. We have shown that the infrared (IR) magnitude
, the X-ray/optical(IR) ratios, the optical colors (for example,
), and the IR color (
) as well as the color distances introduced by us play a significant role in separating the classes of X-ray objects. We use the most important photometric features to interpret the SRGz predictions in this paper. The accuracy of the SRGz photometric redshifts (from DESI LIS, SDSS, Pan-STARRS, and WISE photometric data) has been tested in the Stripe82X field on a sample of 3/4 of the optical counterparts of eROSITA point X-ray sources (for which spectroscopic measurements are available in Stripe82X):
(the normalized median absolute deviation of the prediction) and
(the fraction of catastrophic outliers). The presented photo-z results for eROSITA X-ray sources in the Stripe82X field are more than a factor of 2 better in both metrics (
and
) than the photo-z results of other groups published in the Stripe82X catalog.
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