Lomonosov Moscow State University | via EurekAlert | 2017 Apr 25
[img3="The slowest spinning X-ray pulsar in a globular star cluster has been discovered in the Andromeda galaxy. This object is a small and very dense neutron star pulling gas from a companion star. Infalling gas forms a bright hot spot on the neutron star surface, which creates a light-house effect, because the neutron star revolves every 1.2 seconds. Artwork by A. Zolotov"]https://media.eurekalert.org/multimedia ... 12_web.jpg[/img3][hr][/hr]The Lomonosov Moscow State University scientists published the results of a study of the unique ultra-slow pulsar XB091D. This neutron star is believed to have captured a companion only a million years ago and since then, has been slowly restoring its rapid rotation. The young pulsar is located in one of the oldest globular star clusters in the Andromeda galaxy, where the cluster may once have been a dwarf galaxy.
Massive young stars die, exploding as bright supernovae. In this process, their outer layers of material are thrown off, and the core shrinks, usually becoming a compact and super-dense neutron star. Strongly magnetized, they rotate rapidly, making hundreds of revolutions per second, but they lose their rotational energy and slow down, emitting narrow beams of particles. They radiate a focused radio emission that periodically passes the Earth, creating the effect of a regularly pulsating source, often with a millisecond period.
In order to "return youth" and again accelerate its rotation, the pulsar can encounter an ordinary star. After teaming up to form a pair or a binary system, the neutron star begins to pull matter from the star, forming a hot accretion disk around itself. Closer to the neutron star, the gaseous disk is torn apart by the magnetic field of the neutron star, and the matter streams onto it, forming a "hot spot" - the temperature here reaches millions of degrees, and the spot radiates in X-ray. A rotating neutron star can then be seen as an X-ray pulsar as a beacon, while the matter that continues to fall on it gives an additional impulse, accelerating the rotation. ...
The Slowest Spinning X-Ray Pulsar in an Extragalactic Globular Cluster - Ivan Zolotukhin et al
- Astrophysical Journal 839(2):125 (2017 Apr 20) DOI: 10.3847/1538-4357/aa689d
arXiv.org > astro-ph > arXiv:1602.05191 > 16 Feb 2016 (v1), 27 Mar 2017 (v2)