Abstract
(abridged) Long-duration gamma-ray bursts (LGRBs) occur in galaxies of generally low metallicity. We aim at a spectroscopic analysis of HG 031203, the host galaxy of a LRGB burst, to obtain its properties. Based on VLT/X-shooter spectroscopic observations in the wavelength range 3200-24000A, we use standard direct methods to evaluate physical conditions and element abundances. The resolving power of the instrument also allowed us to trace the kinematics of the ionised gas. We derive an interstellar oxygen abundance of 12+logO/H=8.20+/-0.03. The observed fluxes of hydrogen lines correspond to the theoretical recombination values after correction for extinction with a single value C(Hbeta)=1.67. We produce the CLOUDY photoionisation HII region model that reproduces observed emission-line fluxes of different ions in the optical range. This model also predicts emission-line fluxes in the near-infrared (NIR) and mid-infrared (MIR) ranges that agree well with the observed ones. This implies that the star-forming region observed in the optical range is the only source of ionisation and there is no additional source of ionisation seen in the NIR and MIR ranges that is hidden in the optical range.We find that the heavy element abundances, Halpha luminosity, stellar mass, star-formation rate and specific star-formation rate of HG 031203 are in the range that is covered by the luminous compact galaxies (LCGs).This implies that the LCGs with extreme star-formation that also comprise green pea galaxies as a subclass may harbour LGRBs.
Highlights
GRB 031203 is one of the two closest (z < 0.2) long-duration gamma-ray bursts (LGRB) known apart from the exceptional GRB 980425.Most soft-spectrum Long-duration gamma-ray bursts (LGRBs) are accompanied by massive stellar explosions (the GRB-supernovae (SNe) connection, see van Paradijs 1999; Woosley & Bloom 2006; Soderberg 2006; Hjorth & Bloom 2011)
We find that the heavy element abundances, extinction-corrected Hα luminosity L(Hα) = 7.27 × 1041 erg s−1, stellar mass M∗ = 2.5 × 108 M, star-formation rate star-formation rates (SFRs)(Hα) = 5.74 M yr−1 and specific star-formation rate specific star-formation rates (SSFRs)(Hα) = 2.3 × 10−8 yr−1 of host galaxies (HG) 031203 are in the range that is covered by the LCGs
We have studied the spectrum of the GRB 031203 host galaxy (HG 031203) with the VLT/X-shooter spectroscopic observations in the wavelength range ∼λλ3200–24 000 Å
Summary
GRB 031203 is one of the two closest (z < 0.2) long-duration gamma-ray bursts (LGRB) known apart from the exceptional GRB 980425. Margutti et al (2007) and Prochaska et al (2004) analysed both the Milky Way and the intrinsic extinction in HG 031203 and derived intrinsic extinction coefficients C(Hβ) = 0.59 and C(Hβ) = 0.46, respectively Their intrinsic host-galaxy extinctions seem higher that usually obtained in star-forming compact dwarf galaxies. We here present high-quality archival VLT/X-shooter spectroscopic observations of HG 031203 over a wide wavelength range, which allows us to derive physical conditions, intrinsic reddening and element abundances in the ionised interstellar medium of the galaxy. The extinction and hidden star formation are discussed, the CLOUDY modelling and the comparison of the observed and predicted emission-line fluxes in the MIR range are discussed, the kinematic structure, the luminosity-metallicity relation in Sect.
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