Albert Einstein Institute | Max Planck Institute for Gravitational Physics | 2020 Apr 20
LIGO and Virgo detectors catch first gravitational wave from binary black hole merger with unequal masses
The expectations of the gravitational-wave research community have been fulfilled: gravitational-wave discoveries are now part of their daily work as they have identified in the past observing run, O3, new gravitational-wave candidates about once a week. But now, the researchers have published a remarkable signal unlike any of those seen before: GW190412 is the first observation of a binary black hole merger where the two black holes have distinctly different masses of about 8 and 30 times that of our Sun. This not only has allowed more precise measurements of the system’s astrophysical properties, but it has also enabled the LIGO/Virgo scientists to verify a so far untested prediction of Einstein’s theory of general relativity.Numerical simulation of a black-hole binary merger
with asymmetric masses and orbital precession (GW190412)
Credits: N. Fischer, H. Pfeiffer, A. Buonanno (MPG), SXS Project
“For the very first time we have ‘heard’ in GW190412 the unmistakable gravitational-wave hum of a higher harmonic, similar to overtones of musical instruments,” explains Frank Ohme ... “In systems with unequal masses like GW190412 – our first observation of this type – these overtones in the gravitational-wave signal are much louder than in our usual observations. This is why we couldn’t hear them before, but in GW190412, we finally can.” This observation once again confirms Einstein’s theory of general relativity, which predicts the existence of these higher harmonics, i.e. gravitational waves at two or three times the fundamental frequency observed so far.
“The black holes at the heart of GW190412 have 8 and 30 times the mass of our Sun, respectively. This is the first binary black-hole system we have observed for which the difference between the masses of the two black holes is so large!” says Roberto Cotesta ... “This big mass difference means that we can more precisely measure several properties of the system: its distance to us, the angle we look at it, and how fast the heavy black hole spins around its axis.” ...
GW190412: Observation of a Binary-Black-Hole Coalescence
with Asymmetric Masses ~ LIGO Scientific Collaboration, Virgo Collaboration
- arXiv.org > astro-ph > arXiv:2004.08342 > 17 Apr 2020