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1.
We analyze short-duration gamma-ray bursts (T
90<2 s) recorded in the SPI-ACS experiment of the INTEGRAL observatory. We found an extended emission in the averaged light
curve of both short-duration gamma-ray bursts and unidentified short-duration events. We show that the fraction of short-duration
gamma-ray bursts among all the gamma-ray bursts recorded in the SPI-ACS experiment may be as high as 30 to 45%. We find the
fraction of short gamma-ray bursts to augment while increasing the lower energy threshold. We report evidence for the absence
of the class of very short gamma-ray bursts. 相似文献
2.
P. Yu. Minaev S. A. Grebenev A. S. Pozanenko S. V. Molkov D. D. Frederiks S. V. Golenetskii 《Astronomy Letters》2012,38(10):613-628
The detection of GRB 070912 recorded in the field of view of the SPI, IBIS/ISGRI, and JEMX telescope on September 12, 2007, at 07h32m19s (UT) when analyzing the INTEGRAL archival data is reported. The burst is one of the well-localized events closest to the direction toward the Galactic center (less than from the source Sgr A*) over the entire history of burst observations. Since it was not promptly revealed by the INTEGRAL Burst Alert System (IBAS), no information about its coordinates was disseminated and no search for optical and soft X-ray afterglows was conducted. The 3–200 keV fluence was 2.8 × 10?6 erg cm?2 and the peak flux was 1.8 × 10?7 erg cm?2 s?1 (1.9 ph cm?2 s?1). The burst was also observed in the KONUS/WIND experiment in the background mode, although it was not included in the list of recorded bursts. GRB 070912 is among a limited number of events for which a broadband (3 keV-2 MeV) spectrum of X-ray and gamma-ray emission has been obtained and their evolution from the first instants to complete decay has been traced. It shows how the fast evolution of its spectrum gives rise to absorption features at energies of ～100 keV.Within the first seconds after the onset of the burst, its spectrum was a power law with a photon index of ～0.8, but it exhibited a noticeable deficit of photons at energies below 20 keV. Such an initial deficit (a delay in appearance) of X-ray photons can be explained by their “high-latitude” origin relative to the line of sight. The spectrum rapidly softened and at the decay phase was well described by a blackbody (or Wien) law. This allows the distance (redshift) to the burst source to be estimated. 相似文献
3.
4.
The short duration (T
90 < 2 s) gamma-ray bursts (GRBs) detected in the SPI-ACS experiment onboard the INTEGRAL observatory are investigated. Averaged
light curves have been constructed for various groups of events, including short GRBs and unidentified short events. Extended
emission has been found in the averaged light curves of both short GRBs and unidentified short events. It is shown that the
fraction of the short GRBs in the total number of SPI-ACS GRBs can range from 30 to 45%, which is considerably larger than
has been thought previously. 相似文献
5.
N. A. Skvortsov E. A. Avvakumova D. O. Bryukhov A. E. Vovchenko A. A. Vol’nova O. B. Dluzhnevskaya P. V. Kaigorodov L. A. Kalinichenko A. Yu. Kniazev D. A. Kovaleva O. Yu. Malkov A. S. Pozanenko S. A. Stupnikov 《Astrophysical Bulletin》2016,71(1):114-124
New technical capabilities have brought about the sweeping growth of the amount of data acquired by the astronomers from observations with different instruments in various parts of the electromagnetic spectrum. We consider conceptual approach to be a promising tool to efficiently deal with these data. It uses problem domain knowledge to formulate the tasks and develop problem-solving algorithms and data analysis methods in terms of domain concepts without reference to particular data sources, and thereby allows solving certain problems in general form. We demonstrate the benefits of conceptual approach by using it to solve problems related to search for secondary photometric standard candidates, determination of galaxy redshifts, creation of a binary and multiple star repository based on inhomogeneous databases, and classification of eclipsing binaries.We formulate and solve these problems over specifications of astronomical knowledge units such as photometric systems, astronomical objects, multiple stars, etc., and define them in terms of the corresponding problem domains independently of the existing data resources. 相似文献
6.
We have analyzed the light curves of 519 short gamma-ray bursts (GRBs) detected in the SPI-ACS/INTEGRAL experiment from December 2002 toMay 2014 to search for precursors (a possible activity of the GRB source before the beginning of themain episode). Both the light curves of 519 individual events and the averaged light curve of 372 brightest bursts have been analyzed. In several cases, we have found and thoroughly studied precursor candidates based on SPI-ACS/INTEGRAL, GBM/Fermi, and LAT/Fermi data. A statistical analysis of the averaged light curve for the entire sample of short bursts has revealed no regular precursor. Upper limits for the relative intensity of precursors have been estimated. We have compared our results with those of other authors; no convincing evidence for the existence of precursors of short GRBs has been found. We show that the fraction of short GRBs with precursors is less than 0.4% of all short bursts. 相似文献
7.
We analyze uncertainties in the cosmic X-ray background measurements performed by the INTEGRAL observatory. We find that the
most important effect limiting the accuracy of the measurements is related to the intrinsic background variation in detectors.
Taking into account all of the uncertainties arising during the measurements we conclude that the X-ray background intensity
obtained in the INTEGRAL observations is compatible with the historic X-ray background observations performed by the HEAO-1
satellite. 相似文献
8.
A. S. Pozanenko V. V. Rumyantsev V. M. Loznikov A. A. Volnova A. P. Shulga 《Astronomy Letters》2008,34(3):141-144
GRB 920925C is probably the first cosmic gamma-ray burst with an optical afterglow detected from archival data. We present the results of our observations with the Shajn mirror telescope of the Crimean Astrophysical Observatory aimed at searching for the host galaxy at the afterglow location; we have determined the boundaries of distances to the possible host galaxy. 相似文献
9.
A. Melandri C. Guidorzi S. Kobayashi D. Bersier C. G. Mundell P. Milne A. Pozanenko W. Li A. V. Filippenko Y. Urata M. Ibrahimov I. A. Steele A. Gomboc R. J. Smith N. R. Tanvir E. Rol K. Huang 《Monthly notices of the Royal Astronomical Society》2009,395(4):1941-1949
We present a comprehensive multiwavelength temporal and spectral analysis of the 'fast rise exponential decay' GRB 070419A. The early-time emission in the γ-ray and X-ray bands can be explained by a central engine active for at least 250 s, while at late times the X-ray light curve displays a simple power-law decay. In contrast, the observed behaviour in the optical band is complex (from 102 up to 106 s). We investigate the light-curve behaviour in the context of the standard forward/reverse shock model; associating the peak in the optical light curve at ∼450 s with the fireball deceleration time results in a Lorenz factor Γ≈ 350 at this time. In contrast, the shallow optical decay between 450 and 1500 s remains problematic, requiring a reverse shock component whose typical frequency is above the optical band at the optical peak time for it to be explained within the standard model. This predicts an increasing flux density for the forward shock component until t ∼ 4 × 106 s , inconsistent with the observed decay of the optical emission from t ∼ 104 s . A highly magnetized fireball is also ruled out due to unrealistic microphysic parameters and predicted light-curve behaviour that is not observed. We conclude that a long-lived central engine with a finely tuned energy injection rate and a sudden cessation of the injection is required to create the observed light curves, consistent with the same conditions that are invoked to explain the plateau phase of canonical X-ray light curves of γ-ray bursts. 相似文献
10.
Pozanenko A. S. Minaev P. Yu. Grebenev S. A. Chelovekov I. V. 《Astronomy Letters》2019,45(11):710-727
The results of observations of the gravitational-wave (GW) event S190425z recorded by the LIGO/Virgo detectors with the anti-coincidence shield (ACS) of the SPI gamma-ray spectrometer onboard the INTEGRAL observatory are presented. With a high probability (>99%) it was associated with a neutron star (NS) merger in a close binary system. This is only the second event of such a type in the history of gravitational-wave observations (after GW170817). A weak gamma-ray burst, GRB190425, consisting of two pulses ～0.5 and ～5.9 s after the NS merger in the event S190425z with an a priori significance of 3.5 and 4.4σ (taken together 5.5σ) was detected by SPI-ACS. Analysis of the SPI-ACS count rate history recorded on these days (a total of ～125 ks of observations) has shown that the rate of random occurrence of two close spikes with the characteristics of GRB190425 does not exceed 6.4 × 10?5 s?1 (i.e., such events occur by chance, on average, every ～4.3 hours). Note that the time profile of GRB190425 has much in common with the profile of GRB170817A accompanying the event GW170817, that both NS mergers were the nearest (≤150 Mpc) of all the events recorded by the LIGO/Virgo detectors, and that no significant excesses of the gamma-ray flux above the background were detected in any of ～30 black hole merger events recorded to date by these detectors. No bursts of hard radiation were detected in the field of view of the SPI and IBIS/ISGRI gamma-ray telescopes onboard INTEGRAL. This, along with the absence of detection of gamma-ray emission from GRB190425 by the GBM gamma-ray burst monitor of the Fermi observatory suggesting its occultation by the Earth, allows the localization region for the source of this GWevent to be reduced significantly. The parameters Eiso and Ep for GRB190425 are estimated and compared with those for GRB170817A.
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