Gravitational waves from a binary black hole merger observed by LIGO and Virgo

27 September, 2017


The LIGO Scientific Collaboration and the Virgo collaboration report the first joint detection of gravitational waves with both the LIGO and Virgo detectors. This is the fourth announced detection of a binary black hole system and the first significant gravitational-wave signal recorded by the Virgo detector, and highlights the scientific potential of a three-detector network of gravitational-wave detectors.

The three-detector observation was made on August 14, 2017 at 10:30:43 UTC. The two Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington, and funded by the National Science Foundation (NSF), and the Virgo detector, located near Pisa, Italy, detected a transient gravitational-wave signal produced by the coalescence of two stellar mass black holes.

A paper about the event, known as GW170814, has been accepted for publication in the journal Physical Review Letters.

The detected gravitational waves—ripples in space and time—were emitted during the final moments of the merger of two black holes with masses about 31 and 25 times the mass of the sun and located about 1.8 billion light-years away. The newly produced spinning black hole has about 53 times the mass of our sun, which means that about 3 solar masses were converted into gravitational-wave energy during the coalescence.

The new discovery is particularly important for the Spanish gravitational-wave community, as a research group from the University of Valencia, lead by Prof. José Antonio Font, has recently joined the Virgo Collaboration. With this new group, the Spanish efforts in the LIGO-VirgoCollaboration, thus far only conducted by a group at the University of the Balearic Islands,who joined the LIGO collaboration in 2002 under the leadership of Prof. Alicia Sintes, have significantly increased.

Prof. José Antonio Font, leader of the UV Virgo Group, points out that "there is no doubt that for the Virgo Collaboration, joining LIGO in the ongoing second Observing Run has been a major challenge, successfully achieved on the 1st of August 2017. The commissioning team of Advanced Virgo did a fantastic job, delivering the detector in record time with the required sensitivity to fully collaborate with LIGO in possible future detections, as the new detection GW170814 wonderfully proves". Font adds that "for the UV Virgo Group it has been a great honour to witness such a major organizational effort and to have actively participated in some of the Virgo detector characterization activities."

A key contribution of the UIB group have been models of the gravitational wave signals of black holes. Such models are compared to the data recorded by the LIGO and Virgo detectors, and are necessary to identify the sources of the signals, e.g. whether they are black holes or neutron stars, or to determine their masses. “We have a very busy year ahead of us” says Prof. Sascha Husa of the UIB group. “The next observing run is planned to start in the Fall of 2018 with significantly improved sensitivity. We are expecting several detections every month, and much more detailed models of the gravitational wave signal are needed to extract all the information from these events.”

Prof. Alicia Sintes, the leader of the UIB LIGO group is excited about the prospects for the future. Spain already has a very active community in astronomy, the improved source localization makes gravitational wave observations even more interesting for astronomers, and we hope for diverse interactions in this field between different Spanish groups.” She adds that “the observation of the signal by a detector spurs the efforts in developing a European next generation detector, and intensify the collaboration between the European LIGO and Virgo groups even more.”