GRB110715A: Multifrequency study of the first gamma-ray burst observed with ALMA

GRB 110715A had a bright afterglow that was obscured by a high Galactic extinction. We discovered the submillimetre counterpart with APEX and followed it in radio with ATCA for over 2 months. Additional submillimetre observations were performed with ALMA as a test of the ToO procedures during commissioning. UV, optical and NIR observations were performed with UVOT/Swift and GROND at the 2.2 m telescope in La Silla and X-ray data was obtained by XRT/Swift. The dataset is complemented with spectroscopic data from the X-shooter spectrograph at the VLT. From a broadband model we derive a peculiar density profile in the environment of the progenitor, with a discontinuity that produces a break in the light curve at ∼ 1 day after the burst onset. The absorption features present in the intermediate resolution optical/nIR spectra reveal a redshift of 0.8224 and a host galaxy environment with low ionisation and no velocity components beyond 30 km s−1 . These preliminary results will be published elsewhere