Using the NASA space telescope and the NICER onboard the International Space Station (ISS), astronomers have examined the properties of an ultra-light X-ray pulsar known as NGC 300 ULX1. The results of this study, presented in a report published on May 9 at the arXiv preprint server, show that this object has experienced an unprecedented evolution of rotation since the rotation period has declined significantly over a period of four years.
Ultra-light X-ray sources (ULXs) are point sources in the sky that are so bright in X-rays that each radiates more radiation than 1 million suns emitted at all wavelengths. Although they are less bright than the active galactic nuclei (AGN), they are more consistent than all known star processes.
Some ULXs show consistent ripple. These sources, known as ultra-light X-ray pulsars (ULXPs), are neutron stars, which are usually less massive than black holes. The list of known ULPs is still relatively short, so detailed observations of previously affected objects in this class are essential for researchers studying the universe in X-rays.
NGC 300 ULX1 is ULXP located at 6.13 million light years in the spiral galaxy NGC 300. Discovered in 2010 The source was originally classified as supernova but later reclassified as a possible X-ray binary signal. However, a study published in November 2018 reveals the ripple of the NGC 300 ULX1 that confirms its ULXP character.
After its discovery, NGC 300 ULX1 was observed by a group of astronomers led by Yale University's George Vassilopoulos to get information on the pulsar properties. They used the Neil Gehrels Swift and Neutron Star Interior Composition ExploreR (NICER) observatories attached to the ISS. The data from these two tools allows them to get important information about the spin of this object.
Analyzing the new data and the results of other observations of the NGC 300 ULX1, astronomers have found that the spinal period of this pulsar decreases from 126 seconds to less than 20 seconds in just four years. They added that such behavior is consistent with a steady mass accumulation rate, noting that the neutron star continues to grow at a rate indicating a constant rate of mass increase in 2018.
In addition, the study found that the observed X-ray flux of NGC 300 ULX1 has dropped by a factor of about 20 to 30 of its peak value in 2018. However, although this value is reduced, researchers note that the spin speed of the neutron star remained approximately constant.
Trying to explain the decline in the observed X-ray flow, the authors of the article assume that this may be the result of increased absorption and eclipse.
"One possible explanation is that the reduction in the observed flux is a result of increased absorption of a blurring material due to leakage or precessive accretion disc … Output streams of a predominantly radiation accretion disc can provide an optically thick structure that can be responsible for increased absorption, "astronomers conclude.
A new ultra-light X-ray pulsar has been discovered
G. Vasilopoulos, et al. NGC 300 ULX1: Spin evolution, over-uniform accumulations and outflows. arXiv: 1905.03740v1 [astro-ph.HE], arxiv.org/abs/1905.03740
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X-ray Ultra-Light Pulser NGC 300 ULX1 has experienced unprecedented evolution of rotation, according to a study (2019, May 22)
drawn up on 22 May 2019
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