Castro-Tirad 2010 GRB 021004的前身星和宿主星系

主要内容:
通过对谱的观测，得到一些关于前身星和星系的特性。
该暴的宿主星系是一个星暴星系。

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Title:		GRB 021004: Tomography of a gamma-ray burst progenitor and its host galaxy
Authors:		Castro-Tirado, A. J.; Møller, P.; García-Segura, G.; Gorosabel, J.; Pérez, E.; de Ugarte Postigo, A.; Solano, E.; Barrado, D.; Klose, S.; Kann, D. A.; Castro Cerón, J. M.; Kouveliotou, C.; Fynbo, J. P. U.; Hjorth, J.; Pedersen, H.; Pian, E.; Rol, E.; Palazzi, E.; Masetti, N.; Tanvir, N. R.; Vreeswijk, P. M.; Andersen, M. I.; Fruchter, A. S.; Greiner, J.; Wijers, R. A. M. J.; van den Heuvel, E. P. J.
Affiliation:		AA(Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, 18.008 Granada, Spain ajct@iaa.es), ...
Publication:		Astronomy and Astrophysics, Volume 517, id.A61 (A&A Homepage)
Publication Date:		07/2010
Origin:		EDP Sciences
Keywords:		gamma-ray bust: general, techniques: spectroscopic, stars: Wolf-Rayet, galaxies: starburst, cosmology: observations
DOI:		10.1051/0004-6361/200913966
Bibliographic Code:		2010A&A...517A..61C

Abstract

Aims: We analyse the distribution of matter around the progenitor star of gamma-ray burst GRB 021004 and the properties of its host galaxy with high-resolution echelle and near-infrared spectroscopy.
Methods: Observations were taken by the 8.2 m Very Large Telescope with the Ultraviolet and Visual Echelle spectrograph (UVES) and the Infrared Spectrometer And Array Camera (ISAAC) between 10 and 14 h after the onset of the event.
Results: We report the first detection of emission lines from a GRB host galaxy in the near-infrared, detecting Hα and the [O III] doublet. These allow us to independently measure the systemic redshift (z = 2.3304 ± 0.0005), which is not contaminated by absorption as the Lyα line is, and infer the host galaxy properties. From the visual echelle spectroscopy, we find several absorption-line groups spanning a range of about 3000 km s^-1 in velocity relative to the redshift of the host galaxy. The absorption profiles are very complex with both velocity-broadened components extending over several 100 km s^-1 and narrow lines with velocity widths of only ~20 km s^-1. By analogy with QSO absorption line studies, the relative velocities, widths, and degrees of ionization of the lines (“line-locking”, “ionization-velocity correlation”) show that the progenitor had both an extremely strong radiation field and several distinct mass-loss phases (winds).
Conclusions: These results are consistent with GRB progenitors being massive stars, such as luminous blue variables (LBVs) or Wolf-Rayet stars, providing a detailed picture of the spatial and velocity structure of the GRB progenitor star at the time of explosion. The host galaxy is a prolific star-forming galaxy with a SFR of ~40 M_ȯ yr^-1. Based on observations taken with the ESO's 8.2 m Very Large Telescope in Chile.

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