Electromagnetic Evidence that SSS17a is the Result of a Binary Neutron Star Merger

TL;DR

This paper presents electromagnetic observations of SSS17a, confirming it as a kilonova resulting from a binary neutron star merger, thus independently supporting gravitational wave data.

Contribution

It provides comprehensive optical and near-infrared data analysis that confirms SSS17a as a kilonova from a neutron star merger, reinforcing gravitational wave findings.

Findings

SSS17a is unlike other known transients.

Best described by kilonova models involving r-process elements.

Electromagnetic data independently confirm binary neutron star merger.

Abstract

11 hours after the detection of gravitational wave source GW170817 by the Laser Interferometer Gravitational-Wave Observatory and Virgo Interferometers, an associated optical transient SSS17a was discovered in the galaxy NGC 4993. While the gravitational wave data indicate GW170817 is consistent with the merger of two compact objects, the electromagnetic observations provide independent constraints of the nature of that system. Here we synthesize all optical and near-infrared photometry and spectroscopy of SSS17a collected by the One-Meter Two-Hemisphere collaboration. We find that SSS17a is unlike other known transients. The source is best described by theoretical models of a kilonova consisting of radioactive elements produced by rapid neutron capture (the r-process). We find that SSS17a was the result of a binary neutron star merger, reinforcing the gravitational wave result.