The electromagnetic counterpart of the binary neutron star merger LIGO/Virgo GW170817. II. UV, optical, and near-infrared light curves and comparison to kilonova models

Cowperthwaite, P S, Berger, E, Villar, V A, Metzger, B D, Nicholl, M, Chornock, R, Blanchard, P K, Fong, W, Margutti, R, Soares-Santos, M, Alexander, K D, Romer, A K and et al, (2017) The electromagnetic counterpart of the binary neutron star merger LIGO/Virgo GW170817. II. UV, optical, and near-infrared light curves and comparison to kilonova models. Astrophysical Journal Letters, 848 (2). ISSN 2041-8205

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Abstract

We present UV, optical, and near-infrared (NIR) photometry of the first electromagnetic counterpart to a gravitational wave source from Advanced Laser Interferometer Gravitational-wave Observatory (LIGO)/Virgo, the binary neutron star merger GW170817. Our data set extends from the discovery of the optical counterpart at 0.47–18.5 days post-merger, and includes observations with the Dark Energy Camera (DECam), Gemini-South/ FLAMINGOS-2 (GS/F2), and the Hubble Space Telescope (HST). The spectral energy distribution (SED) inferred from this photometry at 0.6 days is well described by a blackbody model with T » 8300 K, a radius of R » 4.5 ´ 1014 cm (corresponding to an expansion velocity of v » 0.3c), and a bolometric luminosity of Lbol » 5 ´ 10 41 erg s−1. At 1.5 days we find a multi-component SED across the optical and NIR, and subsequently we observe rapid fading in the UV and blue optical bands and significant reddening of the optical/ NIR colors. Modeling the entire data set, we find that models with heating from radioactive decay of 56Ni, or those with only a single component of opacity from r-process elements, fail to capture the rapid optical decline and red optical/NIR colors. Instead, models with two components consistent with lanthanide-poor and lanthanide-rich ejecta provide a good fit to the data; the resulting “blue” component has Mej » 0.01 M blue and v » 0.3 c ej blue , and the “red” component has Mej » 0.04 M red and v » 0.1 c ej red . These ejecta masses are broadly consistent with the estimated r-process production rate required to explain the Milky Way r-process abundances, providing the first evidence that binary neutron star (BNS) mergers can be a dominant site of r-process enrichment.

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science > QB Astronomy
Depositing User: Billy Wichaidit
Date Deposited: 16 Feb 2018 09:58
Last Modified: 16 Feb 2018 09:58
URI: http://sro.sussex.ac.uk/id/eprint/73588

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Project NameSussex Project NumberFunderFunder Ref
Astronomy rolling grantG0278STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCILST/I000976/1