Swift follow-up of the Gravitational Wave source GW150914

TL;DR

This paper reports on Swift satellite follow-up observations of the GW150914 gravitational wave event, finding no electromagnetic counterparts in X-ray, optical, UV, or hard X-ray bands within the observed region.

Contribution

It demonstrates a rapid, automated follow-up methodology for gravitational wave events and highlights the importance of early GW data for electromagnetic observations.

Findings

No electromagnetic counterparts detected in follow-up observations.

Rapid response and automated analysis proved effective.

Coverage was limited to 2% of the GW error region.

Abstract

The Advanced LIGO observatory recently reported the first direct detection of gravitational waves (GW) which triggered ALIGO on 2015 September 14. We report on observations taken with the Swift satellite two days after the trigger. No new X-ray, optical, UV or hard X-ray sources were detected in our observations, which were focussed on nearby galaxies in the GW error region and covered 4.7 square degrees (~2% of the probability in the rapidly-available GW error region; 0.3% of the probability from the final GW error region, which was produced several months after the trigger). We describe the rapid Swift response and automated analysis of the X-ray telescope and UV/Optical Telescope data, and note the importance to electromagnetic follow up of early notification of the progenitor details inferred from GW analysis.