The powerful collision of two neutron stars, which formed gravitational waves and which we learned about last fall, led to the birth of a black hole, scientists say. This newly formed black hole has the smallest mass of any black hole ever discovered by researchers.
The new study analyzed data collected by NASA's Chandra X-ray space observatory over the days, weeks, and months following the detection of gravitational waves by the Laser Interferometer Gravitational Wave Observatory (LIGO) and gamma rays by the spacecraft. NASA Fermi Gamma Observatory ("Fermi") August 17, 2017
While almost every telescope at the disposal of professional astronomers has been used to observe this source, officially known as GW170817, X-ray observations from the Chandra Observatory hold clues to understanding the processes following the collision of two neutron stars.
The data obtained with the LIGO observatory allowed astronomers to estimate the mass of an object formed as a result of the collision of these two neutron stars, which was approximately 2.7 times the mass of the Sun. This mass value puts the resulting object exactly on the border between the most massive neutron stars and the least massive black holes.
In a new work, scientists led by Dave Pooley of Trinity University in San Antonio, USA, analyzed data collected by the Chandra observatory after the neutron merger event and found that the X-ray afterglow from this event was significantly less intense. (by several orders of magnitude), compared to its expected intensity under the assumption of the formation of the resulting neutron star. According to the authors, this indicates that the merger of neutron stars apparently formed not a neutron star, but a black hole.
The study is published in the Astrophysical Journal.