Astronomers investigate spectral evolution of XTE J1810–189

Utilizing the Neutron star Inside Composition Explorer (NICER) onboard the Worldwide Area Station (ISS), European astronomers have carried out spectral evaluation of a low-mass X-ray binary often called XTE J1810–189. Outcomes of the examine, accessible in a analysis paper revealed September 13 on the preprint server arXiv, shed extra mild on the spectral evolution of this method.

X-ray binaries (XRBs) are composed of a traditional star or a white dwarf transferring mass onto a compact neutron star or a black hole. Primarily based on the mass of the companion star, astronomers divide them into low-mass X-ray binaries (LMXBs) and high-mass X-ray binaries (HMXBs).

XTE J1810–189 is a neutron star LMXB estimated to be positioned between 11,400 and 28,400 mild years away. It’s a transient supply, which alternates between quiescent phases and intervals of elevated X-ray emission as a consequence of accretion on the neutron star.

In September 2020, an X-ray outburst of XTE J1810–189 began and lasted about three months. A workforce of astronomers led by Arianna Manca of the College of Cagliari in Italy, has noticed XTE J1810–189 throughout this outburst in an effort to higher perceive its spectral evolution.

“On this paper, we studied the spectral evolution of the NS LMXB XTE J1810–189 throughout its newest outburst. We analyzed NICER knowledge within the 1–10 keV power vary, modeling the emission with an absorbed, thermally Comptonized part, and with a unique mannequin composed by a chilly, Comptonized disk and black body,” the researchers wrote within the paper.

The astronomers managed to conduct 33 NICER observations of XTE J1810–189 in the course of the 2020 outburst, and 23 of them had an publicity lengthy sufficient to supply enough statistics for spectral evaluation. The examine discovered that 22 of those observations may be nicely match by an absorbed, thermally Comptonized part whose photon index barely varies in time, reaching its highest worth in the direction of the top of the outburst.

The temperature of the Comptonized black body was discovered to be about 0.6 keV, which, in keeping with the authors of the paper, can both be a scorching disk or the neutron star floor. Due to this fact, they famous that additional investigation is required to find out whether or not the seed photons for the Comptonization part are coming from the accretion disk or the neutron star.

Primarily based on the collected knowledge, the researchers concluded that XTE J1810–189 didn’t attain a full excessive/comfortable state in the course of the three-months lengthy outburst and its highest luminosity was measured to be about one undecillion erg/s. NICER observations additionally revealed the presence of thermonuclear bursts in the course of the outburst phase of XTE J1810–189. The astronomers famous that the length of those bursts means that the system incorporates a hydrogen-rich important sequence star.

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