GRB 110715A: Multiwavelength study of the first gamma-ray burst observed with ALMA

Abstract

GRB 110715A had a bright afterglow that was obscured inthe optical by a high Galactic extinction. We discovered the submillimetercounterpart with APEX and followed it in radio with ATCAfor over 2 months. Additional submm observations were performedwith ALMA as a test of the ToO procedures during commissioning,becoming the first GRB afterglow to be detected by the observatory.UV, optical and NIR observations were performed with Swift/UVOTand 2.2 m/GROND in La Silla and X-ray data were obtained bySwift/XRT. The dataset is complemented with spectroscopic data fromthe VLT/X-shooter spectrograph. The absorption features presentin the intermediate resolution optical/nIR spectra reveal a redshiftof 0.8224 and a host galaxy environment with low ionization. We fit inthe host galaxy absorption features two velocity components separatedby 30 km/s, implying a host galaxy with low dynamical activity.