An international group of astronomers has reported the discovery of a rare Be/X-ray binary system as part of the Swift Small Magellanic Cloud (SMC) (S-CUBED) survey. The discovery was detailed in a research paper published on the preprint server on March 12. arXiv.

X-ray binaries consist of a normal star or white dwarf that sheds mass into a compact neutron star or black hole. Depending 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 (BeXRB) are the largest subgroup of HMXBs. These systems consist of Be stars and typically neutron stars, including pulsars. Observations revealed that most of these systems exhibited weak, persistent X-ray emission punctuated by bursts lasting several weeks.

Now, a team of astronomers led by Thomas M. Gauden of Pennsylvania State University (PSU) has identified the new BeXRB, designated Swift J010902.6-723710, during S-CUBED tracking observations aimed primarily at detecting the X-ray. explosions. .

“This paper reports the discovery of a previously unknown BeXRB using weekly observations from the SCUBED probe. This new system, named Swift J010902.6-723710, was identified by a transient X-ray burst and tracked by multiwavelength observations, the report said. The researchers wrote .

Swift J010902.6-723710 launched an X-ray flare on October 10, 2023, exhibiting characteristics of Type I and Type II flares. Deep X-ray observations made by Godin’s team revealed that the proposed neutron star rotation period in this system is 182 seconds.

Astronomers analyzed the light curve of both ultraviolet and infrared radiation. As a result, they found strong eclipses occurring every 60,623 days, taken as the system’s suggested orbital period. This makes Swift J010902.6-723710 the third known BeXRB eclipse to date.

Spectroscopic observations have shown that the companion star in Swift J010902.6-723710 is a star of spectral class B0-0.5 Ve. The researchers also identified a double-peaked hydrogen emission line based on spectroscopy; this suggests that Swift J010902.6-723710 is a highly inclined system with a slope of 72-90 degrees.

Additionally, the study confirmed the existence of a large accretion disk surrounding the neutron star in Swift J010902.6-723710, as noted in previous observations. The authors of the paper found that the observed dimming behavior is due to this disk, which has a radius of about 3.3 solar radii.

As a result, the researchers emphasized that Swift J010902.6-723710 should be monitored further as it represents a rare class of shadowed BeXRBs.

“We note that this rare behavior provides an important opportunity to constrain the physical parameters of the Be/X-ray binary to a higher precision than is possible in noneclipsing systems,” the scientists concluded.