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Title: The unpolarized macronova associated with the gravitational wave event GW170817
Authors: Covino, S.
Wiersema, K.
Fan, Y. Z.
Toma, K.
Higgins, A. B.
Melandri, A.
D'Avanzo, P.
Mundell, C. G.
Palazzi, E.
Tanvir, N. R.
Bernardini, M. G.
Branchesi, M.
Brocato, E.
Campana, S.
Alighieri, S. D. S.
Götz, D.
Fynbo, J. P. U.
Gao, W.
Gomboc, A.
Gompertz, B.
Greiner, J.
Hjorth, J.
Jin, Z. P.
Kaper, L.
Klose, S.
Kobayashi, S.
Kopac, D.
Kouveliotou, C.
Levan, A. J.
Mao, J.
Malesani, D.
Pian, E.
Rossi, A.
Salvaterra, R.
Starling, R. L. C.
Steele, I.
Tagliaferri, G.
Troja, E.
Horst, A. J. V. D.
Wijers, R. A. M. J.
First Published: 16-Oct-2017
Publisher: Nature Publishing Group
Citation: Nature Astronomy 2017, 1, pp. 791–794
Abstract: The merger of two dense stellar remnants including at least one neutron star (NS) is predicted to produce gravitational waves (GWs) and short duration gamma ray bursts (GRBs). In the process, neutron-rich material is ejected from the system and heavy elements are synthesized by r-process nucleosynthesis. The radioactive decay of these heavy elements produces additional transient radiation termed "kilonova" or "macronova". We report the detection of linear optical polarization P = (0.50 +/- 0.07)% at 1.46 days after detection of the GWs from GW170817, a double neutron star merger associated with an optical macronova counterpart and a short GRB. The optical emission from a macronova is expected to be characterized by a blue, rapidly decaying, component and a red, more slowly evolving, component due to material rich of heavy elements, the lanthanides. The polarization measurement was made when the macronova was still in its blue phase, during which there is an important contribution from a lanthanide-free outflow. The low degree of polarization is consistent with intrinsically unpolarized emission scattered by Galactic dust, suggesting a symmetric geometry of the emitting region and low inclination of the merger system. Stringent upper limits to the polarization degree from 2.45 - 9.48 days post-burst are consistent with the lanthanides-rich macronova interpretation.
DOI Link: 10.1038/s41550-017-0285-z
ISSN: 2397-3366
Version: Post-print
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © 2017, Nature Publishing Group. Deposited with reference to the publisher’s open access archiving policy.
Description: The file associated with this record is under embargo until 6 months after publication, in accordance with the publisher's self-archiving policy. The full text may be available through the publisher links provided above.
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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