Tomasz Nowakowski is a member of the physics.org community.
The recent eruption of an X-ray pulsar known as SAX J1808.43658 has been inspected by an international team of astronomy using the Neutron Star Interior Composition Explorer (NICER) onboard the International Space Station. The results of the study were published on the arXiv server.
The X-ray intensity can be as short as a fraction of a second. A millisecond X-ray pulsar is a peculiar type of X-ray pulsar in which short spin periods are caused by long- lasting mass transfer from a low-mass companion star through an accretion disk onto a slow- rotating neutron star.
Astronomers think that AMXPs are important in furthering our knowledge about thermonuclear burst processes. Only a few dozen objects of this type have been identified using the space observatory.
During an X-ray eruption in 1996, SAX J1808 was discovered. When X-ray pulsations were detected from this source, it was classified as a millisecond X-ray pulsar. The object is 11,400 light years away and has a brown dwarf companion. The system had an elapsed time of 2.01 hours.
Since it's discovery, SAX J1808 has gone through a period of about ten months. The Monitor of All-sky X-ray Image (MAXI) instrument onboard the International Space Station spotted another eruption of this pulsar. The astronomer group led by Giulia Illiano of Rome Observatory in Italy began to monitor SAX J1808 after the eruption began.
SAX J1808 entered a reflaring stage after decaying from a peak of about one undecillion erg/s. In the past, similar behavior was seen.
The astronomer confirmed that the spin frequencies of SAX J1808 decreased at an average rate of 0.001 pHz/s. The result is in line with the expected energy losses.
The study found that for the first time in the last twenty years, the orbital phase evolution showed signs of contracting. The long-term behavior of the orbit can be described by an 11 second change with a 21 year period.
SAX J1808 is expected to have a new eruption in the year 2025. The authors of the paper stressed the importance of observing this upcoming outburst in order to confirm their findings.
Giulia Illiano et al, Timing analysis of the millisecond X-ray pulsar SAX J1808.43658 hints of an Orbital Shrinking. There is a book titled "arxiv.2212.09778."
Journal information: arXiv
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