When neutron stars collide, it’s very dense, hot and extreme. Physicists believe that under such extreme conditions, processes could be taking place that would put us on the trail of dark matter. They tried to look for axions, still among the leading candidates for dark matter, in observations of the GW170817 neutron star collision. To no avail.
Axion hunting. Credit: Dev et al. (2024), Physical Review Letters.
The summer day of August 17, 2017 went down in the history of astrophysics. The ground-based gravitational observatory LIGO has detected the collision of neutron stars for the first time. It was the first time that the same event was captured by gravity detectors and simultaneously observed by ground-based and space-based telescopes of a more classical type.
Bhupal Dev. Credit: Washington University in St. Lewis.
Physicist Bhupal Dev from the American Washington University in St. Louis and his colleagues used observations of this event, designated GW170817, in their search for dark matter. They’re looking for axions and similar particles, which remain dark matter candidates, but their stock hasn’t been doing too well lately.
As Dev says, when two already very extreme neutron stars collide, a hyperextreme dense and hot thing is created for a certain period of time, which can serve as a factory for exotic particles. Such an object is transiently much hotter than neutron stars, and after a second or so it cools down again to form either a large neutron star or a small black hole, depending on the masses of the neutron stars that collided.
Logo. Kredit: Washington University in St. Louis.
Exotic particles could be created on the mentioned extreme objects, if they exist, and after some time and far from the collision site, they would decay into known particles, for example photons. Dev et al. found that such particles, in their view dark matter axions, could produce unique electromagnetic signals that could be detected by gamma-ray telescopes such as Fermi-LAT.
The researchers used data from the Fermi-LAT gamma-ray telescope related to the neutron star collision GW170817. As has always been the rule, they did not find the axion signal, but defined the parameter region, given by observation, where axions cannot be. It’s not a very dazzling result, but when it comes down to it, nobody has a better one. In any case, Dev is convinced that extreme cosmic phenomena, such as neutron star collisions, represent a promising ecosystem where we can still search for dark matter.
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Literature
Washington University in St. Louis. 3. 2024.
Physical Review Letters 132: 101003.
2024-03-08 23:17:31
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