Astronomers discover a rare eclipsing X-ray binary

A global crew of astronomers reviews the detection of a uncommon eclipsing Be/X-ray binary system as a part of the Swift Small Magellanic Cloud (SMC) Survey (S-CUBED). The discovering was detailed in a research paper revealed March 12 on the preprint server arXiv.

X-ray binaries are composed of a standard 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).

Be/X-ray binaries (BeXRBs) are the most important subgroup of HMXBs. These methods include Be stars and, normally, neutron stars, together with pulsars. Observations have discovered that the majority of those methods showcase weak persistent X-ray emission that’s interrupted by outbursts lasting a number of weeks.

Now, a bunch of astronomers led by Thomas M. Gaudin of the Pennsylvania State College (PSU) has recognized a brand new BeXRB, which acquired designation Swift J010902.6-723710, throughout S-CUBED monitoring observations aimed primarily at detecting X-ray outbursts.

“This paper reviews the detection of a beforehand unknown BeXRB through weekly observations of the SCUBED survey. This new system, Swift J010902.6-723710, was recognized through a transient X-ray outburst and adopted up through multi-wavelength observations,” the researchers wrote.

Swift J010902.6-723710 began an X-ray outburst on October 10, 2023, which showcased traits of Kind I and II outbursts. Deep follow-up X-ray observations performed by Gaudin’s crew recognized a proposed spin interval of 182 seconds for the neutron star on this system.

The astronomers have analyzed the light curve of each ultraviolet and infrared emission. Because of this, they detected robust eclipse-like options that reappear each 60.623 days, which is adopted because the proposed orbital interval of the system. This makes Swift J010902.6-723710 the third eclipsing BeXRB recognized thus far.

Spectroscopic observations have revealed that the companion star in Swift J010902.6-723710 is a B0-0.5 star of spectral class Ve. Primarily based on the spectroscopy, the researchers additionally recognized a strongly double-peaked hydrogen-alpha emission line, which means that Swift J010902.6-723710 is a highly-inclined system with an inclination of 72–90 levels.

Moreover, the examine confirmed the presence of a big accretion disk surrounding the neutron star in Swift J010902.6-723710, which was prompt by earlier observations. The authors of the paper discovered that the detected eclipsing habits is attributable to this disk, which has a radius of roughly 3.3 solar radii.

Summing up the outcomes, the researchers underlined the necessity for additional monitoring of Swift J010902.6-723710 because it represents the uncommon class of eclipsing BeXRBs.

“We word that this uncommon habits offers an vital alternative to constrain the bodily parameters of a Be/X-ray binary with higher accuracy than is feasible in non-eclipsing methods,” the scientists concluded.

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