Highly extinguished host galaxy of the dark GRB 020819

Abstract

We analyse the properties of the host galaxy of the optically dark gamma-ray burst (GRB) 020819 (z = 0.41) and discuss the possible implications in the context of _s15dark_s15 GRBs. We present g_s14r_s14i_s14z_s14JHK photometry of the host galaxy and fit the broad spectral energy distribution including the public Spitzer IRAC data using stellar population models. The broad spectral energy distribution (SED) indicates a high extinction, A_V ~ 1.8 - 2.6 mag, for this relatively massive galaxy. This is the highest global extinction for a GRB host galaxy with a robust spectroscopic redshift. The properties of the host galaxy are indicative of dusty, intense star-formation, which differ from those of the current sample of GRB hosts. This implies that the dust extinction is one of the main reasons for the darkness of low-redshift bursts and that the long GRB host population is far more diverse than previously anticipated.