Primordial Black Hole Capture by Neutron Stars:

[oldpaddoboy]

An Interesting article and paper, that may explain PBH's that were theoretically formed at the big bang. 

https://phys.org/news/2024-04-neutron-stars-capturing-primordial-black.html

Neutron stars could be capturing primordial black holes:

"The Milky Way has a missing pulsar problem in its core. Astronomers have tried to explain this for years. One of the more interesting ideas comes from a team of astronomers in Europe and invokes dark matter, neutron stars, and primordial black holes (PBHs).

 

Astronomer Roberto Caiozzo, of the International School for Advanced Studies in Trieste, Italy, led a group examining the missing pulsar problem. "We do not observe pulsars of any kind in this inner region (except for the magnetar PSR J1745-2900)," he wrote in an email.

"This was thought to be due to technical limitations, but the observation of the magnetar seems to suggest otherwise." That magnetar orbits Sagittarius A*, the black hole at the core of the Milky Way.

The team examined other possible reasons why pulsars don't appear in the core and looked closely at magnetar formation as well as disruptions of neutron stars. One intriguing idea they examined was the cannibalization of primordial black holes by neutron stars."

more at link.

Interesting extract from above article follows...

"Dark matter makes up about 27% of the universe, but beyond suggesting that PBH could be part of the dark matter content, astronomers still don't know exactly what it is. There does seem to be a large amount of it in the core of our galaxy. However, it hasn't been directly observed, so its presence is inferred. Is it bound up in those midrange PBHs? No one knows.

The third player in this missing pulsar mystery is neutron stars. They're huge, quivering balls of neutrons left over after the death of a supergiant star of between 10 and 25 solar masses. Neutron stars start out very hot (in the range of 10 million K) and cool down over time."

"The process works like this: a millisecond pulsar interacts in some way with a primordial black hole that has less than one stellar mass. Eventually, the neutron star (which has a strong enough gravitational pull to attract the PBH) captures the black hole. Once that happens, the PBH sinks to the core of the neutron star. Inside the core, the black hole begins to accrete matter from the neutron star.

Eventually, all that's left is a black hole with about the same mass as the original neutron star. If this occurs, that could help explain the lack of pulsars in the inner parsecs of the Milky Way."

The paper:

https://arxiv.org/pdf/2404.08057

Revisiting Primordial Black Hole Capture by Neutron Stars:

Abstract:

"A sub-solar mass primordial black hole (PBH) passing through a neutron star, can lose enough energy through interactions with the dense stellar medium to become gravitationally bound to the star. Once captured, the PBH would sink to the core of the neutron star, and completely consume it from the inside. In this paper, we improve previous energy-loss calculations by considering a realistic solution for the neutron star interior, and refine the treatment of the interaction dynamics and collapse likelihood. We then consider the effect of a sub-solar PBH population on neutron stars near the Galactic center. We find that it is not possible to explain the lack of observed pulsars near the galactic center through dynamical capture of PBHs, as the velocity dispersion is too high. We then show that future observations of old neutron stars close to Sgr A* could set stringent constraints on the PBHs abundance. These cannot however be extended in the currently unconstrained asteroid-mass range, since PBHs of smaller mass would lose less energy in their interaction with the neutron star and end up in orbits that are too loosely bound and likely to be disrupted by other stars in the Galactic center"