Optical Observations of LIGO Source GW 170817 by the Antarctic Survey Telescopes at Dome A, Antarctica

TL;DR

This paper reports optical observations of the GW 170817 event using Antarctic telescopes, capturing a rapidly fading transient consistent with neutron star merger models and providing insights into the ejected radioactive material.

Contribution

First optical observations of GW 170817 from Dome A, Antarctica, demonstrating rapid transient detection and analysis aligned with neutron star merger predictions.

Findings

Detected a transient fading within 1.8 hours after GW trigger

Estimated ejected radioactive mass of about 0.01 solar masses

Observed brightness decline consistent with neutron star merger models

Abstract

The LIGO detection of gravitational waves (GW) from merging black holes in 2015 marked the beginning of a new era in observational astronomy. The detection of an electromagnetic signal from a GW source is the critical next step to explore in detail the physics involved. The Antarctic Survey Telescopes (AST3), located at Dome A, Antarctica, is uniquely situated for rapid response time-domain astronomy with its continuous night-time coverage during the austral winter. We report optical observations of the GW source (GW~170817) in the nearby galaxy NGC 4993 using AST3. The data show a rapidly fading transient at around 1 day after the GW trigger, with the $i$-band magnitude declining from $17.23\pm0.13$ magnitude to $17.72\pm0.09$ magnitude in $\sim 1.8$ hour. The brightness and time evolution of the optical transient associated with GW~170817 are broadly consistent with the predictions of models involving merging binary neutron stars. We infer from our data that the merging process ejected about $\sim 10^{-2}$ solar mass of radioactive material at a speed of up to $30\%$ the speed of light.