The Combined Ultraviolet, Optical, and Near-infrared Light Curves of the Kilonova Associated with the Binary Neutron Star Merger GW170817: Unified Data Set, Analytic Models, and Physical Implications

Abstract

We present the first effort to aggregate, homogenize, and uniformly model the combined ultraviolet, optical, and near-infrared dataset for the electromagnetic counterpart of the binary neutron star merger GW170817. By assembling all of the available data from 18 different papers and 46 different instruments, we are able to identify and mitigate systematic offsets between individual datasets, and to identify clear outlying measurements, with the resulting pruned and adjusted dataset offering an opportunity to expand the study of the kilonova. The unified dataset includes 647 individual flux measurements, spanning 0.45 to 29.4 days post-merger, and thus has greater constraining power for physical models than any single dataset. We test a number of semianalytical models and find that the data are well modeled with a three-component kilonova model: a "blue" lanthanide-poor component (κ = 0.5 cm 2 g −1 ) with M ej ≈ 0.020 M and v ej ≈ 0.27c; an intermediate opacity "purple" component (κ = 3 cm 2 g −1 ) with M ej ≈ 0.047 M and v ej ≈ 0.15c; and a "red" lanthanide-rich component (κ = 10 cm 2 g −1 ) with M ej ≈ 0.011 M and v ej ≈ 0.14c. We further explore the possibility of ejecta asymmetry and its impact on the estimated parameters. From the inferred parameters we draw conclusions about the physical mechanisms responsible for the various ejecta components, the properties of the neutron stars, and, combined with an up-to-date merger rate, the implications for r-process enrichment via this channel. To facilitate future studies of this keystone event we make the unified dataset and our modeling code public.

Constraint on the Ejecta Mass for Black Hole–Neutron Star Merger Event Candidate S190814bv

“…The upper limit to the ejecta mass is discussed in Gomez et al (2019) and Andreoni et al (2019) based on the upper limits to the EM counterparts. By employing an 1d analytical model of Villar et al (2017), Gomez et al (2019) explore the ranges of ejecta mass, velocity, and opacity in which the kilonova emission is consistent with the upper limits obtained by their observation (see Figure 4 in Gomez et al (2019)). Andreoni et al (2019) employ an 1d kilonova model of Hotokezaka & Nakar (2019) and a 2d kilonova model of Bulla (2019a); Dhawan et al (2020) and suggest that the total ejecta mass should be less than 0.04 M for the face-on observation or less than 0.03 M for the ejecta opacity 2 cm 2 /g for D = 215 Mpc.…”

Continued Brightening of the Afterglow of GW170817/GRB 170817A as Being Due to a Delayed Energy Injection

“…It also does not conflict with the estimation of M ej ∼10 −3 -10 −2 M e for the dynamical ejecta of GW170817 (Abbott et al 2017d;Utsumi et al 2017;Tanaka et al 2017;Matsumoto et al 2018). In a few recent studies, a more precise ejecta mass of M ej ∼0.05M e was estimated when modeling the GW170817 kilonova (Cowperthwaite et al 2017;Drout et al 2017;Kasliwal et al 2017;Kasen et al 2017;Villar et al 2017;Waxman et al 2017). These studies also support the idea that there is enough material being ejected during the NS-NS merger.…”

A multidimensional implementation of the Advanced Spectral neutrino Leakage scheme

“…The intensity of the EM emission detected in the aftermath of the event decayed with a power-law exponent close to −1.3 Rosswog et al 2018) as expected for a distribution of freshly synthesized rprocess elements (Metzger et al 2010;Korobkin et al 2012). Estimates of the involved ejecta masses point to ∼ 0.02 M for the early blue emission component and ∼ 0.04 M for the later emerging red component (Villar et al 2017;Kasen et al 2017;Perego et al 2017b;Rosswog et al 2018). The early blue component requires lanthanide-free ejecta which, in turn, are the r-process nucleosynthesis result of matter with Y e 0.25 (Korobkin et al 2012;Kasliwal et al 2019) (ejected at velocities of ∼ 0.3c).…”