INTEGRAL and XMM-Newton observations of GRB 040106^*

¹ Department of Experimental Physics, University College Dublin, Dublin 4, Ireland
² School of Physics and Astronomy, University of Southampton, Southampton, UK e-mail: lmoran@astro.soton.ac.uk
³ Istituto di Astrofisica Spaziale e Fisica Cosmica - CNR, via Bassini 15, 20133 Milano, Italy
⁴ Max-Planck-Institut für extraterrestrische Physik, 85748 Garching, Germany
⁵ Department of Physics, University of Alabama at Huntsville, USA
⁶ Science Operations and Data Systems Division of ESA/ESTEC,SCI-SDG, 2200 AG Noordwijk, The Netherlands
⁷ Space and Remote Sensing Sciences, Los Alamos National Laboratory, USA

Received: 10 May 2004
Accepted: 15 November 2004

Abstract

On January 6th 2004, the IBAS burst alert system triggered the 8th gamma-ray burst (GRB) to be located by the INTEGRAL satellite. The position was determined and publicly distributed within 12 s, prompting ESA's XMM-Newton to execute a ToO observation just 5 h later, during which an X-ray afterglow was detected. The GRB had a duration ~52 s with two distinct pulses separated by ~42 s. Here we present the results of imaging and spectral analyses of the prompt emission from INTEGRAL data and the X-ray afterglow from XMM-Newton data. The γ-ray spectrum is consistent with a single power-law of photon index -1.72 ± 0.15. The fluence (20–200 keV) was 8.2  10^-7 erg cm^-2. The X-ray afterglow () was extremely hard with  ± 0.01 and  ± 0.04. The 2–10 keV flux 11 h after the burst was 1.1  10^-12 erg cm^-2 s^-1. The time profile of the GRB is consistent with the observed trends from previous analysis of BATSE GRBs. We find that the X-ray data are not well-fit by either a simple spherical fireball or by a speading jet, expanding into a homogeneous medium or a wind environment. Based on previously determined correlations between GRB spectra and redshift, we estimate a redshift of ~0.9 (1σ) and a lower limit on the isotropic radiated energy of ~5  10⁵¹ erg in this burst.