GW150914: The Advanced LIGO Detectors in the Era of First Discoveries

TL;DR

This paper describes the upgraded Advanced LIGO detectors' capabilities, their first observation run, and the groundbreaking detection of GW150914, marking the start of gravitational-wave astronomy.

Contribution

It details the detector enhancements, their first successful observation, and the potential for future sensitivity improvements in gravitational-wave detection.

Findings

Detection of GW150914, the first gravitational-wave event from black hole merger

Advanced LIGO achieved unprecedented sensitivity and volume of observation

Detectors are designed for further sensitivity improvements

Abstract

Following a major upgrade, the two advanced detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) held their first observation run between September 2015 and January 2016. With a strain sensitivity of $10^{-23}/\sqrt{\mathrm{Hz}}$ at 100 Hz, the product of observable volume and measurement time exceeded that of all previous runs within the first 16 days of coincident observation. On September 14th, 2015 the Advanced LIGO detectors observed a transient gravitational-wave signal determined to be the coalescence of two black holes [Phys. Rev. Lett. 116, 061102 (2016)], launching the era of gravitational-wave astronomy. The event, GW150914, was observed with a combined signal-to-noise ratio of 24 in coincidence by the two detectors. Here we present the main features of the detectors that enabled this observation. At full sensitivity, the Advanced LIGO detectors are designed to deliver another factor of three improvement in the signal-to-noise ratio for binary black hole systems similar in masses to GW150914.