GRB 071028B, a burst behind large amounts of dust in an unabsorbed galaxy
Max-Planck-Institut für extraterrestrische Physik, Giessenbachstraße 1, 85748 Garching, Germany
2 Universe Cluster, Technische Universität München, Boltzmannstraße 2, 85748 Garching, Germany
3 Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
4 European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany
5 Department of Physics and Astronomy, Clemson University, Clemson, SC 29634-0978, USA
Received: 1 July 2010
Accepted: 12 January 2011
Aims. We report on the discovery and properties of the fading afterglow and underlying host galaxy of GRB 071028B, thereby facilitating a detailed comparison between these two.
Methods. Observations were performed with the Gamma-ray Burst Optical and Near-infrared Detector at the 2.2 m telescope on the La Silla Paranal Observatory in Chile. We conducted five observations from 1.9 d to 227.2 d after the trigger and obtained deep images in the g′r′i′z′ and JHKs bands.
Results. Based on accurate seven-channel photometry covering the optical to near-infrared wavelength range, we derive a photometric redshift of for the unabsorbed host galaxy of GRB 071028B. In contrast, we show that the afterglow with an intrinsic extinction of is moderately absorbed and requires a relatively flat extinction curve. According to the reported Swift/BAT observations, the energetics yield an isotropic energy release of .
Key words: x-rays: bursts / galaxies: starburst / galaxies: photometry / techniques: photometric
© ESO, 2011