BVRcIc photometry of GRB 980703 and GRB 990123 host galaxies

Abstract

We present a photometry of GRB 980703 and GRB 990123 host galaxies which was performed about 20 days and a half year after gamma-ray bursts occured, respectively. The contributions of the optical transiets (OT) were negligible in both cases. We derived broad band BVR_cI_c spectra of the host galaxies and compared them to continuum spectra of different Hubble-type galaxies and averaged spectra of starburst galaxies. For H_0=60 km s^{-1} Mpc^{-1} and three Friedmann cosmological models with matter density and cosmological constant parameters (Omega_m,Omega_Lambda) = (1,0),(0,0),(0,1) we estimated M_Brest and star-forming rates (SFRs) using the fluxes in photometric bands for the host galaxies. Within the range of cosmological parameters our estimates of the absolute magnitudes are: M_Brest = -20.60 .. -21.73 for the GRB 980703 host galaxy and M_Brest = -20.20 .. -21.82 for the GRB 990123 host galaxy. We obtained estimates of K-correction values and absolute magnitudes of the host galaxies using SEDs for star-forming galaxies.