The Redshift and the Ordinary Host Galaxy of GRB 970228


The gamma-ray burst of 1997 February 28 (GRB 970228) ushered in the discovery of the afterglow phenomenon. Despite intense study of the nearby galaxy, however, the nature of this galaxy and the distance to the burst eluded the community. Here we present the measurement of the redshift of the galaxy, the putative host galaxy of GRB 970228, and, based on its spectroscopic and photometric properties, identify the galaxy as a subluminous but otherwise normal galaxy at redshift z=0.695 undergoing a modest level of star formation. At this redshift, the GRB released an isotropic-equivalent energy of (1.4+/-0.3)×10$^52$ ergs (20-2000 keV rest frame). We find no evidence that the host is significantly bluer or is forming stars more vigorously than the general field population. In fact, by all accounts in our analysis (color- magnitude, magnitude-radius, star formation rate, and Balmer- break amplitude), the host properties appear typical for faint blue field galaxies at comparable redshifts. Partially based on the observations obtained at the W. M. Keck Observatory, which is operated by the California Association for Research in Astronomy, a scientific partnership among California Institute of Technology, the University of California, and the National Aeronautics and Space Administration.

Astrophysical Journal