C. Bradaschia

TL;DR: The squeezing injection was fully automated and over the first 5 months of the third joint LIGO-Virgo observation run O3 squeezing was applied for more than 99% of the science time, and several gravitational-wave candidates have been recorded.

Abstract: A transient gravitational-wave signal, GW150914, was identified in the twin Advanced LIGO detectors on September 14, 2015 at 09:50:45 UTC. To assess the implications of this discovery, the detectors remained in operation with unchanged configurations over a period of 39 d around the time of the signal. At the detection statistic threshold corresponding to that observed for GW150914, our search of the 16 days of simultaneous two-detector observational data is estimated to have a false alarm rate (FAR) of < 4.9 × 10^(−6) yr^(−1), yielding a p-value for GW150914 of < 2 × 10^(−7). Parameter estimation followup on this trigger identifies its source as a binary black hole (BBH) merger with component masses (m_1, m_2) = (36^(+5)_(−4), 29^(+4)_(−4)) M_⊙ at redshift z = 0.09^(+0.03)_(−0.04) (median and 90\% credible range). Here we report on the constraints these observations place on the rate of BBH coalescences. Considering only GW150914, assuming that all BBHs in the Universe have the same masses and spins as this event, imposing a search FAR threshold of 1 per 100 years, and assuming that the BBH merger rate is constant in the comoving frame, we infer a 90% credible range of merger rates between 2--53 Gpc^(−3) yr^(−1) (comoving frame). Incorporating all search triggers that pass a much lower threshold while accounting for the uncertainty in the astrophysical origin of each trigger, we estimate a higher rate, ranging from 13--600 Gpc^(−3) yr^(−1) depending on assumptions about the BBH mass distribution. All together, our various rate estimates fall in the conservative range 2--600 Gpc^(−3) yr^(−1).

TL;DR: The sensitivity of the LIGO network to transient gravitational-wave signals is estimated, and the capability of the network to determine the sky location of the source is studied, to facilitate planning for multi-messenger astronomy with gravitational waves.

TL;DR: In this article, a cross-correlation analysis on the data from Advanced LIGO's second observing run (O2) is presented, which combines with the results of the first observing run, and upper limits on the normalized energy density in gravitational waves at the 95% credible level of ΩGW < 6.0 × 10−8 at 25 Hz for a background of compact binary coalescences.

TL;DR: The Virgo detector has now finished its first science run; a science mode duty cycle of more than 80% and a 4.5 Mpc horizon distance for binary neutron star inspiral sources were achieved.