The host-galaxy response to the afterglow of GRB 100901A★
- Olga E. Hartoog1,2,†,
- Klaas Wiersema3,
- Paul M. Vreeswijk4,
- Lex Kaper1,
- Nial R. Tanvir3,
- Sandra Savaglio5,
- Edo Berger6,
- Ryan Chornock5,
- Stefano Covino7,
- Valerio D’Elia8,9,
- Hector Flores10,
- Johan P. U. Fynbo11,
- Paolo Goldoni12,
- Andreja Gomboc13,14,
- Andrea Melandri7,15,
- Alexei Pozanenko16,
- Joop Schaye2,
- Antonio de Ugarte Postigo17 and
- Ralph A. M. J. Wijers1
- 1Astronomical Institute Anton Pannekoek, University of Amsterdam, PO Box 94249, NL-1090 GE Amsterdam, the Netherlands
- 2Leiden Observatory, Leiden University, PO Box 9513, NL-2300 RA Leiden, the Netherlands
- 3Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
- 4Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhaga 5, IS-107 Reykjavik, Iceland
- 5Max Planck Institute for Extraterrestrial Physics, D-85748 Garching bei München, Germany
- 6Harvard–Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA
- 7INAF – Osservatorio Astronomico di Brera, Via E. Bianchi 46, I-23807 Merate (LC), Italy
- 8INAF – Osservatorio Astronomico di Roma, Via Frascati 33, I-00040 Monteporzio Catone, Italy
- 9ASI Science Data Centre, Via Galileo Galilei, I-00044 Frascati, Italy
- 10Laboratoire GEPI, Observatoire de Paris, CNRS-UMR8111, Univ Paris Diderot, 5 place Jules Janssen, F-92195 Meudon, France
- 11Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen, Denmark
- 12APC, Astroparticules et Cosmologie, Universite Paris Diderot, CNRS/IN2P3, CEA/Irfu, Observatoire de Paris, Sorbonne Paris Cite, 10, rue Alice Domon et Leonie Duquet, F-75205 Paris Cedex 13, France
- 13Faculty of Mathematics and Physics, University of Ljubljana, Jadranska 19, SI-1000 Ljubljana, Slovenia
- 14Centre of Excellence SPACE-SI, Aškerčeva cesta 12, SI-1000 Ljubljana, Slovenia
- 15Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead, CH41 1LD, United Kingdom
- 16Space Research Institute (IKI), 8432 Profsoyuznaya str., 117997 Moscow, Russia
- 17Instituto de Astrofísica de Andalucía (IAA-CSIC), Glorieta de la Astronomía s/n, E-18008 Granada, Spain
- ↵†E-mail: O.E.Hartoog{at}uva.nl
- Accepted 2013 January 10.
- Received 2013 January 4.
- In original form 2012 July 20.
- First published online February 12, 2013.
Abstract
For gamma-ray burst 100901A, we have obtained Gemini-North and Very Large Telescope optical afterglow spectra at four epochs: 1 h, 1 d, 3 d and 1 week after the burst, thanks to the afterglow remaining unusually bright at late times. Apart from a wealth of metal resonance lines, we also detect lines arising from fine-structure levels of the ground state of Fe ii, and from metastable levels of Fe ii and Ni ii at the host redshift (z = 1.4084). These lines are found to vary significantly in time. The combination of the data and modelling results shows that we detect the fall of the Ni ii 4F9/2 metastable level population, which to date has not been observed. Assuming that the population of the excited states is due to the ultraviolet radiation of the afterglow, we estimate an absorber distance of a few hundred pc. This appears to be a typical value when compared to similar studies. We detect two intervening absorbers (z = 1.3147, 1.3179). Despite the wide temporal range of the data, we do not see significant variation in the absorption lines of these two intervening systems.
Key words
- gamma-ray burst: individual: GRB 100901A
- galaxies: abundances
- galaxies: distances and redshifts
- galaxies: ISM
- © 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
