The black widow pulsar PSR J0952-0607 is gaining 2.4 solar masses, approaching the upper size limit of neutron stars.
U.S. astronomers have estimated the neutron star mass of the pulsar PSR J0952-0607, and it turned out to be a record – almost 2.5 times that of the Sun. It is possible that PSR J0952-0607 is approaching the upper limit, after which the neutron star begins to collapse into a black hole. The scientists write about it in a paper published in the online library of preprints arXiv.
The neutron star PSR J0952-0607, discovered in 2017, is 20,000 light-years from the Sun, in the constellation Sextant. It rotates rapidly, emitting narrow and powerful streams of radiation from its poles. Every 1.41 milliseconds, one of them is pointed in our direction, forming a regularly flaring millisecond pulsar.
Such a high frequency is not too typical for neutron stars, so astronomers have long assumed that it has a small and dim and therefore almost invisible partner – for example, a brown dwarf. The denser and more massive neutron star pulls its matter, gaining additional mass and rotational speed. Such a union will sooner or later end with the complete death of the neighboring neutron star, so such pulsars are called “black widows.
To get a better look at the unusual system, Stanford University professor Roger Romani and his colleagues used a 10-meter telescope at Hawaii’s Keck Observatory. By conducting spectrometric observations, the scientists confirmed that a partner is orbiting the neutron star at high speed (380 km/s), and the star itself has already gained about 2.35 solar masses.
PSR J0952-0607 is noticeably more massive than ordinary neutron stars, which have an average of about 1.4 solar masses. According to the authors of the paper, it is the most massive of the neutron stars whose masses have been established with sufficient reliability. The previous record holder, PSR J0740+6620 in the constellation Giraffe, gained 2.08 solar masses.
These figures are of considerable interest. The point is that, theoretically, gaining more and more matter and mass, the neutron star should collapse into a black hole. However, the boundary at which this happens is not precisely defined – for non-rotating neutron stars, it is estimated at 2.01-2.16 solar masses, although the rotating ones can be much higher. This stimulates the search for the heaviest neutron stars, which will help clarify the upper limit of their masses.
