Positions of pulsars and positions of X-ray sources in Messier 15. Credit: arXiv (2023). DOI: 10.48550/arxiv.2312.06067
Using China’s Five Hundred Meter Aperture Spherical Radio Telescope (FAST), astronomers have discovered three new pulsars in an ancient galactic globular cluster known as Messier 15. Two of them turned out to be long-range pulsars. period, while the last turns like this. quickly that it was classified as a millisecond pulsar. The discovery was reported in a paper published Dec. 11 on the preprint server. arXiv.
Pulsars are highly magnetized rotating neutron stars that emit a beam of electromagnetic radiation. The fastest rotating pulsars, with rotation periods less than 30 milliseconds, are called millisecond pulsars (MSP). Astronomers assume that they form in binary systems when the initially more massive component transforms into a neutron star that then rotates due to accretion of material from the secondary star.
Located approximately 35,700 light years from Earth, Messier 15 (also known as NGC 7078) is a collapsed core GC with a radius of approximately 88 light years and an estimated mass of 560,000 solar masses. It is one of the oldest (around 12 billion years old) and most metal-poor (with a metallicity of around −2.25) galactic GCs, and one of the most densely populated GCs in our galaxy.
Previous observations of Messier 15 detected nine pulsars and the first was identified in 1989. According to simulations, Messier 15 is perhaps one of the GCs with the largest number of pulsars. This is why a team of astronomers led by Yuxiao Wu from Chongqing University of Posts and Telecommunications in China, decided to conduct a search for pulsars in this cluster using FAST.
The new pulsars received the designations PSR J2129+1210J, PSR J2129+1210K and PSR J2129+1210L. Observations revealed that PSR J2129+1210J is an MSP, while the other two are long-period pulsars.
According to the study, PSR J2129+1210J is an isolated pulsar with a rotation period of approximately 11.84 milliseconds and its dispersion measurement was calculated to be 66.68 pc/cm.3. As for the PSR J2129+1210K, it has a rotation period of approximately 1.93 seconds and a dispersion measurement of 68.01 pc/csm.3.
With a rotation period of 3.96 seconds, PSR J2129+1210L is the longest rotating pulsar known to date in a GC. The dispersion measurement of this pulsar was found to be approximately 67.1 pc/cm3.
The researchers noted that the precise position of PSR J2129+1210K and PSR J2129+1210L remains unknown, but they are likely not too far from the core of Messier 15. Therefore, additional observations are needed in order to find their location correct, which will help determine whether these are young or recycled pulsars.
More information:
Yuxiao Wu et al, Three pulsars discovered in the globular cluster M15 (NGC 7078) with FAST, arXiv (2023). DOI: 10.48550/arxiv.2312.06067
Journal information:
arXiv
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