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The most important results obtained by the GRB group
(Identification of the first 10 GRBs. Pulsars.)
(A detailed version is here)
- In 1997 as a result of long-term BTA observations in four photometric bands (BVRI) we obtained the first detailed
light curve of the optical source corresponding to the gamma-ray burst of May, 8, 1997 (BeppoSAX GRB 970508).
Our 4-band observations permitted to comprehensively study the light variability in the first days after detection of the source,
to gauge photometric observations with other big telescopes and to determine an exponential brightness fall in 4 bands after
the brightness maximum. The light changes were monitored till the 200th day and then we studied a host galaxy - an object of ~25m -
and other galaxies in the GRB 970508 field which was at that time only the second one from GRBs identified in optical.
- In 1998 faint (host) galaxies were discovered in areas of optical transients of GRB 970508 and GRB 980703. The BTA was used
to discover a host galaxy for GRB 980519 (R~26.5). At that time it was the faintest host galaxy.
- In 2000 the BTA observational data of a distant galaxy of 24m identified with GRB 991208 were used to measure the red shift
z=0.7063+/-0.0017, to trace the brightness evolution of the optical source and then to study galaxies in the field of this burst with
high angular resolution. The work was carried out in collaboration with a group of observers at the Hubble Space Telescope (HST).
- In 2001 on the basis of energy distributions in spectra of GRB host
galaxies obtained from the BTA observations a conclusion which was a
fundamental for interpretation of GRBs nature was made: these galaxies
do not differ from normal "field" galaxies with identical stellar magnitudes
and red shifts. It permits to determine an average frequency of gamma-ray
bursts in galaxies directly from observations ~ 5•10-8 GRB per year
per galaxy.
- In 2003 the first (and the earliest of all at that time) spectra of an optical source related with GRB 030329 were obtained.
In the first hour the optical spectrum is likely to be a mixture of a GRB afterglow spectrum and an early UV spectrum of a "massive"
supernova (SN) of Ib/c type.
- On April, 8, 2005, an optical afterglow of GRB050408 was discovered with SAO telescopes (the BTA and the 1-meter Zeiss).
A variable object was first discovered by our observations in a gamma-ray burst localization area by the space observatory HETE.
The result was considered as one of the best SAO achievements in 2005.
- In 1996 we managed to see stellar-like objects (R~25) with the BTA. These were the first neutron stars (NS) that we started
investigating in collaboration with the Hubble Space Telescope. We continued studying pulsar nebulae - remnants of SN bursts
(PSR B1951+32 in ÑÒÂ 80), the search and investigation of optical radiation of NSs. Fluxes for the object PSR 0656+14 and
Geminga were obtained with the BTA. The wide-band spectra of these NSs were built from UV to IR. The work is being fulfilled
in collaboration with ASC FIAN, IKI, SAI, Mexico National Institute of Astronomy.
- In February 2006 the spectra of GRB 060218/SN 2006aj (z=0.033) were obtained with the BTA.
Like the case of GRB 030329/SN 2003dh (z = 0.1685), our observations turned out again among
the very first spectral observations of these two nearest GRB/SN bursts. These observational
results were obtained under a joint program of Instituto de Astrofisica de Andalucia
(Alberto J. Castro-Tirado, IAA-CSIC, Spain) and SAO RAS. In 2006, the basic result of the program
on identification of GRBs was formulated as follows: the long gamma-ray bursts are a beginning
of an explosion of distant massive SNs. The most probably, during the gamma-ray burst
we observe a relativistic collapse of a star nucleus and the birth of a very dense
compact object - a supernova explosion remnant.
- 2007: Stellar-wind Envelope of Massive Supernova Progenitor Star XRF060218/SN2006aj.
In the early spectra of the supernova SN2006aj related to the gamma-ray burst GRB060218,
H-alpha hydrogen lines with velocities of 28000km/s and 24000km/s were found, which points to
the existence of a stellar-wind envelope in the vicinity of the progenitor star. Such envelope
is formed as a result of massive star's evolution and was observed during the burst as a
powerful thermal component in its X-ray spectrum
- 2008: Optical observation of an isolated neutron star.
In the framework of the international collaboration (Russia, Spain, Germany,
South Africa, Chile) the event SWIFT J195509+261406 was optically observed during
three days. It was discovered that this event is neither a classic gamma-ray burst,
nor a black hole in a binary system, nor a microquasar. It corresponds rather to
a model of an isolated neutron star with an anomalous magnetic field of ~1015 Gauss
(a magnetar in its active phase). A variability of optical radiation of the soft
gamma-repeater was discovered. It was shown that this event is “a bridge” in the
luminosity scale between anomalous X-ray pulsars and faint isolated neutron stars.
The results obtained in SAO turned out finally to be among the very first observational arguments in favor of an increasing
confidence that a space gamma-ray burst is a beginning of an explosion of distant "massive" supernovae. All our results
were cited in literature and were considered as the most important results of SAO in 1997, 1998, 2000, 2001, 2003, 2004, 2005, 2006, 2007, 2008
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