Successful detection of gravitational waves continues for the collaboration of LIGO-Virgo-KAGRA It has now confirmed two separate “mixed” mergers between a black hole and a neutron star. This caused powerful gravitational waves to ripple across spacetime. Those signals were detected last year by working together, just 10 days apart, a year and a half later. The official event marks the first confirmation of a mixed merger. As described in a new paper published in The Astrophysical Journal Letters.
Astrid Lamberts, co-author of the CNRS, a Virgo collaboration researcher in Nice, said: “With the new discovery of the merger of neutron stars and black holes at outside our galaxy We found the missing binary type. “We finally started to understand how many of these systems exist. combined frequencies And why haven̵7;t we seen an example in the Milky Way?”
LIGO detects gravitational waves through laser interferometry. It uses a high-powered laser to measure tiny changes in the distance between two objects positioned kilometer apart. LIGO has detectors in Hanford, Washington, and in Livingston, Louisiana. Third detector in Italy, Advanced VIRGO online in 2016. In Japan, KAGRA is online and is the first gravitational wave detector in Asia and the first to be built underground. Construction began in LIGO-India earlier this year. And physicists expect construction to begin after 2025.
until now The LIGO collaboration has detected dozens of merger events since its first Nobel Prize-winning discovery. All of which involve two black holes or two neutron stars. last year The collaboration has announced the detection of two more black hole mergers. One of them is the merger of the largest and most distant black hole ever detected. and produces the most powerful signal detected so far. It was shown in the data to be more “bang” than a normal “chick.” The detection was also the first direct observation of a medium-mass black hole.
When the detector sensitivity improves Confirmed events also occur much more frequently. In just one month after the start of the new run on April 1, 2019, LIGO/VIRGO, for example, witnessed five gravitational wave events. Three events are from black hole mergers and one from neutron star mergers. The fifth time might be an elusive black hole. /merger of neutron stars
As previously reported by Ars’ John Timmer, on April 26, 2019, all three detectors came online when an extremely distant event occurred about 1.2 billion light-years away. outlined roughly It is the first possible merger between a 23 solar mass black hole and a 2.6 solar neutron star, the heaviest known neutron star. though another way It might be the lightest black hole known. The detector detects a second possible black hole/neutron star merger. Although that could be interference from the detector.
“Gravitational waves allow us to detect the collision of a black hole and a pair of neutron stars. But the collision of a black hole with a neutron star is an elusively lost piece of the family picture of compact object mergers,” said Chase Kimball, a Northwestern University graduate student who was one of the co-authors of the paper. new “Completing this image is essential to limiting a host of astrophysical models of compact body formation and binary evolution. The nature of these models is to predict the rate at which black holes and neutron stars merge. with these detections Finally we have measurements. The consolidation rate of all three types of compact binary mergers.”
Both LIGO Livingston and Virgo received a signal from the first black hole/neutron star merger on January 5, 2020, designated GW200105, but the signal was very strong only at the Livingston detector, while LIGO-Hanford of all lines at that time Consequently, the synergies cannot accurately determine the location of the merger in the sky. They were able to narrow the area to only about 34,000 times the size of a full moon. However, the team was able to conclude that the signals came from mixed mergers. This involves a black hole with about nine solar masses and a neutron star about 1.9 solar masses located 900 million light-years away.
However, all three detectors were online when the signal from the second black hole/neutron star merger (designated GW200115) arrived on Jan. 15. The event involved a black hole of six solar masses. that combines with a neutron star that has a mass of about 1.5 solar masses. And the team was able to narrow the location of the merger to about 3,000 times the area of the full moon. Analyzing these two events, the LIGO-Virgo researchers think that this mixed merger could happen about once a month. Although not all events can be detected. Due to the current sensitivity of various detectors
“Following the compelling discovery announced in June 2020 regarding the merger of a black hole with a mysterious object, possibly the most massive neutron star known. It is also exciting that our anticipated, well-specified, mixed merger detection. “Theoretical models have been around for decades,” said co-author Vicky Kalogera, Northwestern University. birth”
for how these mixed systems were formed in the first place. One possibility is that two stars already orbit each other. with enough mass to produce a supernova. Left behind the black hole and the neutron star. Alternatively, it is possible that the neutron star and the black hole in such a mixed merger formed separately from the supernova explosion and eventually drifted together to form a binary star system. This is likely to occur in globular clusters, which contain more dense stars. Astrophysicists can study the spin direction of black holes in a given combination of mergers for clues as to which of the two mechanisms led to the merger.
“This is not an incident where a black hole eats a neutron star like a cookie monster and throws it into shreds.”
This is the so-called era of astronomy. multi-messenger So astronomers around the world are hunting for the flashes in their telescopes that could be the electromagnetic signature that comes from those mergers. but it’s useless This may be because the merger takes place so far away, any light produced will be too dim to detect once it reaches our telescope. It may be that there is no light show. Because a black hole swallows a neutron star entirely.
“This is not an event where a black hole chews on a neutron star like Cookie Monster and throws itself into shreds,” said co-author Patrick Brady of the University of Wisconsin-Milwaukee, a spokesman for the LIGO Scientific Collaboration. will cause light And we don’t think this will happen in these cases.”
More such discoveries are likely to be made, as LIGO, Virgo and KAGRA are making further improvements to the detectors in preparation for the next summer’s run. with these upgrades They estimated that they could detect as many gravitational wave events as one per day.
“We have now seen the first example of a black hole merging with a neutron star. So we know they’re out there,” said co-author Maya Fishbach of Northwestern. “But there’s still a lot we don’t know about neutron stars and black holes—big or small. How fast do they spin? How do they pair up as a merger alliance? With future gravitational wave data, we’ll have statistics to answer these questions. and finally learn how the most extreme objects in our universe were created.”
DOI: The Astrophysical Journal, 2021 10.3847/2041-8213/ac082e (about DOI).