(ORDO NEWS) — Astronomers have figured out the nature of the mysterious Cow megaflare: most likely, we observed the birth of an ultra-compact object – a neutron star or even a black hole.
In 2018, dozens of telescopes detected a sudden flare that was visible from 200 million light-years away. This might look like a super bright supernova, but the process was developing faster than it should, was much larger than an ordinary supernova, and the spectrum lacked their characteristic lines. Since then, the nature of the AT2018cow outbreak – or simply Cow (translated from English – “cow”) – has remained a mystery.
After lengthy discussions and calculations, two hypotheses about the nature of Cow appeared on the “home stretch”. According to the first, a super-powerful flare could occur at the time of the death of a star, a white dwarf that was torn apart when it approached a black hole.
The second option is a supernova explosion, leaving behind an ultra-compact object, a neutron star, or even a black hole. The second version is supported by the authors of a new article – astronomers from the Massachusetts Institute of Technology – published in the journal Nature Astronomy .
To determine the origin of Cow, Dheeraj Pasham and his colleagues studied X-rays coming from the source. In it, they noticed a signal – a faint “ripple” that occurred at a frequency of 224 hertz for more than 60 days. Such oscillations can be created by a rapidly rotating supercompact object no more than 1000 kilometers in size and weighing up to 850 times the mass of the Sun – that is, a black hole or an incredibly dense neutron star.
This process can be called “classical”, it is described in many details, but Cow may be the first time when we actually managed to observe how the birth of black holes and neutron stars occurs in supernova explosions. “I think Cow is just the beginning,” said Dhiraj Pasham. “More observations like this will help us understand how these extreme explosions happen.”
It is worth adding that the name Cow was the result of a coincidental coincidence of a series of three letters describing the observation of the outbreak. However, since then there have been several more such events – ” fast blue optical variable sources “, and after the “cow” they are named after animals: for example, Koala (ZTF18abvkwla) and Camel (AT2020xnd). Perhaps their observations will test the conclusions drawn from Cow’s example and better understand how black holes and neutron stars are born.
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