GRB 041219A: its host galaxy and its broad‐band prompt optical‐to‐gamma‐ray emission

Abstract

GRB 041219A is one of the longest and brightest gamma‐ray bursts (GRBs) ever observed. It was discovered by the INTEGRAL satellite, and, thanks to a precursor happening about 300 s before the bulk of the burst, ground based telescopes were able to catch the rarely‐observed prompt emission in the optical and in the near‐infrared bands. Here we present the late‐time multi‐band near‐infrared imaging data, collected at the CFHT, that allowed us to identify the host galaxy of the GRB as an under‐luminous, irregular galaxy of -5*10(9) M at best-fit redshift of z= 0.31 - 0.26 (+0.54). In addition we model the broad‐band prompt optical to γ‐ray emission of GRB 041219A within the internal shock model, where we were able to reproduce the spectra and light curve invoking the synchrotron emission of relativistic electrons accelerated by a series of propagating shock waves inside a relativistic outflow.