A detailed spectral study of GRB 041219A and its host galaxy

TL;DR

This paper provides a comprehensive spectral analysis of GRB 041219A, combining gamma-ray, X-ray, and infrared data to understand its emission mechanisms and host galaxy characteristics.

Contribution

It offers the first detailed multi-wavelength spectral modeling of GRB 041219A, linking prompt emission to internal shock processes and identifying its host galaxy at a specific redshift.

Findings

The host galaxy is an under-luminous, irregular galaxy at z≈0.3.

The prompt emission spectra are consistent with synchrotron radiation from internal shocks.

Infrared data pose challenges to the current emission models.

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 detailed analysis of its prompt gamma-ray emission, as observed with IBIS on board INTEGRAL, and of the available X-ray afterglow data collected by XRT on board Swift. We then present the late-time multi-band near infrared imaging data, collected at the TNG, and the CFHT, that allowed us to identify the host galaxy of the GRB as an under-luminous, irregular galaxy of about 5x10^9 M_Sun at best fit redshift of z=0.31 -0.26 +0.54. We model the broad-band prompt optical to gamma-ray emission of GRB 041219A within the internal shock model. 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. On the other hand, it is less easy to simultaneously reproduce the temporal and spectral properties of the infrared data.