arXiv subjects

S. V. Zharikov

Publications and source records attributed to S. V. Zharikov.

58 records · Page 4Linked to original sources

arXiv1998

BVRcIc photometry of GRB970508 optical remnant: May-August, 1997

We present the results of photometric observations of the variable optical source associated to the remnant of the gamma-ray burst GRB970508 performed at SAO RAS (Russia) from May to August 1997. The observations were carried out with the standard (Johnson-Kron-Cousins) photometric BVRcIc system using the 1-meter and 6-meter telescopes. The brightness of the optical source increased from Rc=21.19 (May 9.75 UT) to Rc=19.70 (May 10.77 UT), whereupon it was decaying in all the four BVRcIc bands during about one month after the burst. Between the 3rd and the 6th night after the GRB970508 event, the flux decrease of the optical source follows an exponential law in all the four bands. In that period the broad-band spectrum of the object does not change and can be approximately described by a power with index -1.1. The subsequent observations showed a reduction of the source brightness decrease rate in all bands. The source flux decay after the maximum in the Rc band is well described by a single power-law with index -1.171 for the whole set of observations during 86 days. In the other bands the decay seems to slow down from the 31th day onwards. In particular, in the Ic band the source magnitude is about 23.1 from the 36th day after the GRB to the end of the observations (August 4, 1997).

astro-ph↗

arXiv1997

BVRI observations of PSR B0656+14 with the 6-meter telescope

We observed the middle-aged radio pulsar 0656+14 with a CCD detector at the 6-m telescope. Broadband BVRI images show the following magnitudes of the pulsar counterpart: B = 24.85 (+0.19, -0.16), V = 24.90 (+0.16, -0.14), R = 24.52 (+0.12, -0.11), I = 23.81 (+0.27, -0.21). We fitted the UV-optical (space + ground-based) data with a two-component model which combines a power law (non-thermal component) with a thermal spectrum emitted by the neutron star surface. The power law component, with the energy power-law index α=1.5 (+1.1,-1.2), dominates in the observed range. Constraints on the thermal component correspond to the Rayleigh-Jeans parameter G\equiv T_6(R_{10}/d_{500})^2=4.1 (+2.1, -4.1), where $T=10^6T_6$ K is the brightness temperature, R_\infty = 10 R_{10}$ km is the neutron star radius as seen by a distant observer, and $d=500 d_{500}$ pc is the distance. The shape of the optical-UV spectrum of PSR 0656+14 differs considerably from those observed from other pulsars: the middle-aged Geminga and young Crab, Vela.

astro-ph↗

arXiv1997

Multicolor photometry of the GRB970508 optical remnant

We report results of follow-up multicolor photometry of the optical variable source that is a probable remnant of the gamma-ray burst GRB970508 discovered by the BeppoSAX satellite (IAUC 6649). Observations were carried out in Johnson-Kron-Cousins $ BVR_cI_c system with the 1-m and 6-m telescopes of SAO RAS. Between the 2nd and the 5th day after the burst a fading of the remnant is well fitted with an exponential law in all four bands. During this period the `broadband spectrum' of the object was unchanged and can be approximated by a power-law, F_ν\proptoν^{-1.1}. After the 5th day the decline of brightness is slowed down. In the R_c band until the 32nd day, the light curve can be described by a power-law relation, F_t \propto t^{-1.2}.

astro-ph↗

arXiv1997

Deep photometric study of the region of the gamma-ray burst localization of June 13, 1979

In the framework of the hypothesis on potential sources of some gamma-ray bursts being single compact objects of neutron star type with finite surface temperature in the vicinity of the Sun a method of search in the optical range for a corresponding candidate in the region of a powerful short burst localization is considered. The localization region of the GRB790613 event is studied in the B, V and R filters. B-V and V-R colors of 196 objects with a S/N > 4 are measured up to the average practical photometric limit B < 25.7, V < 25.7 and R < 25.6 for the whole obtained mosaic of CCD images. No blue objects with B-V < 0 and V-R <0 were found up to B \approx 25.2, which can be interpreted as the absence of a compact object with a temperature > 1.5 10^{5}, K in this direction up to a distance \approx 40, pc. A probable common upper limit to the temperature of the supposed compact objects in the vicinity of the Sun is indicated based on the accumulated optical and X--ray data. The study of blue (B-V < 0) objects in the smallest (in the northern sky) gamma-ray box GRB790613, in view of the results of the search for point-like sources in the soft X--ray in the localization regions of bright gamma-ray bursts, does not exclude the existence of such ``cold'' (<= 10^{5} K) objects, which could give an essential contribution to the observed density of hidden matter close to the Sun and some of them could be related with the closest sources of gamma-ray bursts. Several interesting objects were also found in (or near) the localization region of the GRB790613 event.

astro-ph↗