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Published February 2015 | Published
Journal Article Open

Detailed afterglow modelling and host galaxy properties of the dark GRB 111215A


Gamma-ray burst (GRB) 111215A was bright at X-ray and radio frequencies, but not detected in the optical or near-infrared (nIR) down to deep limits. We have observed the GRB afterglow with the Westerbork Synthesis Radio Telescope and Arcminute Microkelvin Imager at radio frequencies, with the William Herschel Telescope and Nordic Optical Telescope in the nIR/optical, and with the Chandra X-ray Observatory. We have combined our data with the Swift X-Ray Telescope monitoring, and radio and millimetre observations from the literature to perform broad-band modelling, and determined the macro- and microphysical parameters of the GRB blast wave. By combining the broad-band modelling results with our nIR upper limits we have put constraints on the extinction in the host galaxy. This is consistent with the optical extinction we have derived from the excess X-ray absorption, and higher than in other dark bursts for which similar modelling work has been performed. We also present deep imaging of the host galaxy with the Keck I telescope, Spitzer Space Telescope, and Hubble Space Telescope (HST), which resulted in a well-constrained photometric redshift, giving credence to the tentative spectroscopic redshift we obtained with the Keck II telescope, and estimates for the stellar mass and star formation rate of the host. Finally, our high-resolution HST images of the host galaxy show that the GRB afterglow position is offset from the brightest regions of the host galaxy, in contrast to studies of optically bright GRBs.

Additional Information

© 2014 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2014 November 12. Received 2014 October 21; in original form 2014 August 18. First published online December 10, 2014. We would like to thank Alexander Kann for useful discussions, and Alex Filippenko, Shri Kulkarni, Josh Bloom, Brad Cenko, and Jeff Silverman for enabling or performing the Keck telescope observations presented in this paper. AJvdH and RAMJW acknowledge support from the European Research Council via Advanced Investigator Grant no. 247295. KW acknowledges support from the Science and Technology Facilities Council (STFC). Support for DAP was provided by NASA through Hubble Fellowship grant HST-HF-51296.01-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. RLCS is supported by a Royal Society Fellowship. PAC acknowledges support from Australian Research Council grant DP120102393. The Westerbork Synthesis Radio Telescope is operated by Netherlands Institute for Radio Astronomy (ASTRON) with support from the Netherlands Foundation for Scientific Research. The Arcminute Microkelvin Imager arrays are supported by the University of Cambridge and the STFC. The William Herschel Telescope and Nordic Optical Telescope are operated on the island of La Palma by the Isaac Newton Group and Nordic Optical Telescope Scientific Association, respectively, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration (NASA); the Observatory was made possible by the generous financial support of the W.M. Keck Foundation. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA; Spitzer observations were undertaken as part of large program 90062. Some observations were made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555; HST observations were undertaken as part of program 12378. The scientific results reported in this paper are based in part on observations made by the Chandra X-ray Observatory, under ObsID 14052. This work made use of data supplied by the UK Swift Science Data Centre at the University of Leicester.

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Published - MNRAS-2015-van_der_Horst-4116-25.pdf


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August 20, 2023
August 20, 2023