Please use this identifier to cite or link to this item: http://hdl.handle.net/2381/39731
Title: Steep extinction towards GRB 140506A reconciled from host galaxy observations: Evidence that steep reddening laws are local
Authors: Heintz, K. E.
Fynbo, J. P. U.
Jakobsson, P.
Krühler, T.
Christensen, L.
Watson, D.
Ledoux, C.
Noterdaeme, P.
Perley, D. A.
Rhodin, H.
Selsing, J.
Schulze, S.
Tanvir, N. R.
Møller, P.
Goldoni, P.
Xu, D.
Milvang-Jensen, B.
First Published: 2017
Publisher: EDP Sciences for European Southern Observatory (ESO), Springer Verlag
Citation: Astronomy and Astrophysics, 2017
Abstract: We present the spectroscopic and photometric late-time follow-up of the host galaxy of the long-duration Swift gamma-ray burst GRB 140506A at z = 0.889. The optical and near-infrared afterglow of this GRB had a peculiar spectral energy distribution (SED) with a strong flux-drop at 8000 {\AA} (4000 {\AA} rest-frame) suggesting an unusually steep extinction curve. By analyzing the contribution and physical properties of the host galaxy, we here aim at providing additional information on the properties and origin of this steep, non-standard extinction. We find that the strong flux-drop in the GRB afterglow spectrum at < 8000 {\AA} and rise at < 4000 {\AA} is well explained by the combination of a steep extinction curve along the GRB line of sight and contamination by the host galaxy light so that the scenario with an extreme 2175 {\AA} extinction bump can be excluded. We localise the GRB to be at a projected distance of approximately 4 kpc from the centre of the host galaxy. Based on emission-line diagnostics of the four detected nebular lines, Halpha, Hbeta, [O II] and [O III], we find the host to be a modestly star forming (SFR = 1.34 +/- 0.04 Msun yr^-1) and relatively metal poor (Z = 0.35^{+0.15}_{-0.11} Zsun) galaxy with a large dust content, characterized by a measured visual attenuation of A_V = 1.74 +/- 0.41 mag, thus unexceptional in all its physical properties. We model the extinction curve of the host-corrected afterglow and show that the standard dust properties causing the reddening seen in the Local Group are inadequate in describing the steep drop. We conclude that the steep extinction curve seen in the afterglow towards the GRB is of exotic origin, is sightline-dependent only and thus solely a consequence of the circumburst environment.
DOI Link: 10.1051/0004-6361/201730702
ISSN: 0004-6361
eISSN: 1432-0746
Links: https://www.aanda.org/component/article?access=doi&doi=10.1051/0004-6361/201730702
http://hdl.handle.net/2381/39731
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © 2017, EDP Sciences for European Southern Observatory (ESO), Springer Verlag. Deposited with reference to the publisher’s open access archiving policy.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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