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Properties of the host galaxy of the gamma-ray burst 970508 and local star-forming galaxies

V. V. Sokolov·S. V. Zharikov·Yu. V. Baryshev·M. O. Hanski·K. Nilsson·P. Teerikorpi·L. Nicastro·E. Palazzi
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Abstract

Late-time observations of GRB970508 with the SAO-RAS 6-m telescope in July-August 1998 show that the optical transient (OT) varies very little since November 1997. Here we report the $BVR_cI_c$ light-curves behaviour up to 470 days from the GRB occurence with independent $BVR_cI_c$ power-law fits. After ~=200 days the power-law decay has ceased and the OT contamination to the host galaxy flux is already less than the observational errors of the brightness estimates. Spectral energy distribution for the host galaxy alone (without OT) and comparison of its broad-band spectrum to the average continuum spectra of different Hubble types galaxies are shown. The best fits to the BVR_cI_c spectral energy distribution of the GRB host with local starburst galaxies are found for the blue compact S0 dwarf galaxy NGC1510, the Scd starburst HII galaxy NGC7793 and the blue compact galaxy Mrk 1267. Position of the host galaxy in the M_B vs. log(D_25) diagram for local late-type LEDA galaxies allows us to attribute GRB970508 host galaxy to the blue compact galaxies.

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V. V. Sokolov, S. V. Zharikov, Yu. V. Baryshev, M. O. Hanski, K. Nilsson, P. Teerikorpi, L. Nicastro, E. Palazzi. 1998-11-27. Properties of the host galaxy of the gamma-ray burst 970508 and local star-forming galaxies. https://arxiv.org/abs/astro-ph/9809111

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