According to research, SWIFT J0503.7-2819 is an intermediate polar

TESS light curve of J0503. Inset of the figure shows a close-up of some variability cycles. Credit: Rawat et al., 2022.

Using data from multiple space telescopes, researchers analyzed SWIFT J0503.7-2819, a fluctuating X-ray source. The study's findings indicate that this source is an intermediate polar. The discovery was disclosed in an article published on the arXiv pre-print service on September 22. CVs are binary star systems that consist of a white dwarf accreting material from a normal star partner. They fluctuate in brightness by a huge factor, then return to a quiescent condition. Polars are a kind of cataclysmic variable distinguishable from others by the existence of a strong magnetic field in their white dwarfs.

When the white dwarf is somewhat magnetic, accretion happens through a shortened accretion disk in some CVs. These are referred to as intermediate polars (IPs). Observations demonstrate that in IPs, the magnetic white dwarf spins asynchronously with the system's orbital period, resulting in a fast oscillation with the spin period. As a result, identifying the correct spin period and oscillation ephemeris may be the key to revealing the IP character of some CVs. SWIFT J0503.7-2819 (or J0503 for short) is a variable X-ray source discovered in 2015 at a distance of approximately 2,730 light years. J0503's orbital period is 81.6 minutes, and it may be an IP, according to further observations.

To test this hypothesis, an astronomical team led by Nikita Rawat of India's Aryabhatta Research Institute of Observational SciencES (ARIES) performed X-ray observations of J0503 with NASA's Swift and ESA's XMM-Newton telescopes, as well as optical observations with NASA's Transiting Exoplanet Survey Satellite (TESS). Data from the American Association of Variable Star Observers (AAVSO) database were used to supplement the study. We performed X-ray and optical timing assessments, as well as X-ray spectrum analysis, on a possible IP J0503, the researchers noted in their report.

J0503 has an orbital period of roughly 81.65 minutes, according to the measurements. Furthermore, scientists discovered a 65.5-minute periodicity, which they attribute to the white dwarf's spin cycle. If this is the case, J0503 would be the first almost synchronous IP address below the period gap. Astronomers believe J0503 is not synced because the companion star has a low magnetic moment. As a result, it is unable to synchronize, as are virtually synchronous IPs and EX Hya-like systems. The study discovered that J0503 is most likely accreting via stream-fed accretion. Furthermore, the discovered energy-dependent spin pulsations appear to be caused by photoelectric absorption in the accretion flow, which is one of the IPs' distinguishing features.

The study also derived fundamental parameters of the white dwarf in J0503. According to the paper, this star has a mass of about 0.54 solar masses, a mass accretion rate at a level of 1.44 × 10−10 solar masses per year, and a shocking height of approximately 27.6 kilometers.

Journal Information: Nikita Rawat, J. C. Pandey, Arti Joshi, Simone Scaringi, Umesh Yadava, SWIFT J0503.7-2819: A nearly synchronous intermediate polar below the period gap? arXiv:2209.11141v1 [astro-ph.HE], arxiv.org/abs/2209.11141