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.