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

By P. Cowperthwaite, E. Berger, V. Villar, B. Metzger, M. Nicholl, Ryan Chornock, P. Blanchard, W. Fong, Raffaella Margutti, M. Soares-Santos and 134 more. 2017

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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 × 10 14 cm (corresponding to an expansion velocity of v ≈ 0.3 c ), and a bolometric luminosity of L bol ≈ 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 M ej blue ≈ 0.01 M ⊙ and v ej blue ≈ 0.3 c , and the “red” component has M ej red ≈ 0.04 M ⊙ and v ej red ≈ 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 binary neutron star (BNS) mergers can be a dominant site of r-process enrichment.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/8dbe5c068ad58997b4322fb6323cb094ce428aed

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In Astronomy and Astrophysics

1. B. Metzger
2. E. Berger
3. Bing Zhang
4. E. Quataert
5. David Radice
6. Michela Mapelli
7. D. Kasen
8. N. Giacobbo

Citations in the corpus

• Three-dimensional GRMHD Simulations of Neutrino-cooled Accretion Disks from Neutron Star Mergers (2017, background): “0.25) expanding at a lower velocity v ≈ 0.1 c (e.g. Kasen et al. 2017; Cowperthwaite et al. 2017; Tanvir et al. 2017; Shappee et al. 2017; Kilpatrick et al. 2017; Kasliwal et al. 2017; Nicholl et al. 2017; Chornock et al. 2017; Drout et al. 2017; Mc- Cully et al. 2017; Tanvir et al. 2017; Villar et…”
• Constraining the Maximum Mass of Neutron Stars from Multi-messenger Observations of GW170817 (2017, methodology): “…Kasen 2013; Tanaka & Hotokezaka 2013) at late times requires at least two distinct ejecta components consisting, respectively, of light and heavy r-process nuclei (e.g. Cowperthwaite et al. 2017; Nicholl et al. 2017; Chornock et al. 2017; Kasen et al. 2017; Drout et al. 2017; Kasliwal et al. 2017).”
• Binary Black Hole Population Properties Inferred from the First and Second Observing Runs of Advanced LIGO and Advanced Virgo (2018, background): “…was observed across the electromagnetic spectrum, from radio(Alexander et al. 2017), to near-IR/optical(Chornock et al. 2017; Coulter et al. 2017; Cowperthwaite et al. 2017; Nicholl et al. 2017; Pian et al. 2017; Soares-Santos et al. 2017), to X-ray(Margutti et al. 2017; Troja et al. 2017), to…”
• Long-term GRMHD simulations of neutron star merger accretion discs: implications for electromagnetic counterparts (2018, methodology): “Evidence for the r-process comes from the photometric and spectroscopic properties of the observed kilonova (e.g., Cowperthwaite et al. 2017; Chornock et al. 2017; Drout et al. 2017; Tanaka et al. 2017; Tanvir et al. 2017).”
• The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. IV. Detection of Near-infrared Signatures of r-process Nucleosynthesis with Gemini-South (2017, methodology): “This may be similar to the intermediate, or “purple”, kilonova component inferred from the photometry by Cowperthwaite et al. (2017).”
• Mass Ejection from the Remnant of a Binary Neutron Star Merger: Viscous-radiation Hydrodynamics Study (2017, background): “…with macronova/kilonova were indeed observed simultaneously with GW170817(e.g., Abbott et al. 2017b; Arcavi et al. 2017; Coulter et al. 2017; Cowperthwaite et al. 2017; Drout et al. 2017; Kasliwal et al. 2017; Nicholl et al. 2017; Pian et al. 2017; Shappee et al. 2017; Smartt et al. 2017;…”
• AT 2017gfo: An Anisotropic and Three-component Kilonova Counterpart of GW170817 (2017, background): “Two or even three component models are necessary (Cowperthwaite et al. 2017; Tanvir et al. 2017; Tanaka et al. 2017).”
• The Binary Neutron Star Event LIGO/Virgo GW170817 160 Days after Merger: Synchrotron Emission across the Electromagnetic Spectrum (2018, background): “A long-lived magnetar remnant is already disfavored by the KN emission (e.g. Cowperthwaite et al. 2017; Drout et al. 2017; Kasliwal et al. 2017; Nicholl et al. 2017; Pian et al. 2017; Smartt et al. 2017; Tanvir et al. 2017; Villar et al. 2017), particularly the inferred presence of lanthanide-rich…”