paper

The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. II. UV, Optical, and Near-IR Light Curves and Comparison to Kilonova Models

arXiv:1710.05840 · doi:10.3847/2041-8213/aa8fc7

Abstract

We present UV, optical, and NIR photometry of the first electromagnetic counterpart to a gravitational wave source from Advanced LIGO/Virgo, the binary neutron star merger GW170817. Our data set extends from the discovery of the optical counterpart at days to days post-merger, and includes observations with the Dark Energy Camera (DECam), Gemini-South/FLAMINGOS-2 (GS/F2), and the {\it Hubble Space Telescope} ({\it HST}). The spectral energy distribution (SED) inferred from this photometry at days is well described by a blackbody model with K, a radius of cm (corresponding to an expansion velocity of ), and a bolometric luminosity of erg s. At 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 Ni, or those with only a single component of opacity from -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 M and c, and the "red" component has M and c. These ejecta masses are broadly consistent with the estimated -process production rate required to explain the Milky Way -process abundances, providing the first evidence that BNS mergers can be a dominant site of -process enrichment.

13 Pages, 3 Figures, 2 Tables. ApJL, In Press. Keywords: GW170817, LVC

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