@article{bed12c9de2af48e7afb2610ee6bc54e2,
title = "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",
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 $0.47$ days to $18.5$ 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 $0.6$ days is well described by a blackbody model with $T\approx 8300$ K, a radius of $R\approx 4.5\times 10^{14}$ cm (corresponding to an expansion velocity of $v\approx 0.3c$), and a bolometric luminosity of $L_{\rm bol}\approx 5\times10^{41}$ 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 $^{56}$Ni, 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 $M_\mathrm{ej}^\mathrm{blue}\approx 0.01$ M$_\odot$ and $v_\mathrm{ej}^\mathrm{blue}\approx 0.3$c, and the {"}red{"} component has $M_\mathrm{ej}^\mathrm{red}\approx 0.04$ M$_\odot$ and $v_\mathrm{ej}^\mathrm{red}\approx 0.1$c. 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 BNS mergers can be a dominant site of $r$-process enrichment. ",
keywords = "astro-ph.HE",
author = "{The LIGO Scientific Collaboration} and Cowperthwaite, {P. S.} and E. Berger and Villar, {V. A.} and Metzger, {B. D.} and M. Nicholl and R. Chornock and Blanchard, {P. K.} and W. Fong and R. Margutti and M. Soares-Santos and Alexander, {K. D.} and S. Allam and J. Annis and D. Brout and Brown, {D. A.} and Butler, {R. E.} and Chen, {H. -Y.} and Diehl, {H. T.} and Z. Doctor and Drout, {M. R.} and T. Eftekhari and B. Farr and Finley, {D. A.} and Foley, {R. J.} and Frieman, {J. A.} and Fryer, {C. L.} and J. Garc{\'i}a-Bellido and Gill, {M. S. S.} and J. Guillochon and K. Herner and Holz, {D. E.} and D. Kasen and R. Kessler and J. Marriner and T. Matheson and {E. H. Neilsen}, Jr and E. Quataert and A. Palmese and A. Rest and M. Sako and Scolnic, {D. M.} and N. Smith and Tucker, {D. L.} and Williams, {P. K. G.} and E. Balbinot and Carlin, {J. L.} and Cook, {E. R.} and F. Durret and Li, {T. S.} and Lopes, {P. A. A.}",
note = "13 Pages, 3 Figures, 2 Tables. ApJL, In Press. Keywords: GW170817, LVC",
year = "2017",
month = oct,
day = "16",
doi = "10.3847/2041-8213/aa8fc7",
language = "English",
volume = "848",
journal = "Astrophysical Journal Letters",
issn = "2041-8205",
publisher = "Institute of Physics Publishing Ltd",
number = "2",
}