Using data from various space telescopes, astronomers investigated SWIFT J0503.7-2819, a variable X-ray source. The study’s findings indicate that this source is an intermediate polar. The discovery was detailed in a paper published on the arXiv pre-print server on September 22.
CVs are binary star systems that consist of a white dwarf accreting material from a normal star companion. They fluctuate in brightness by a large factor, then return to a quiescent state. Polars are a type of cataclysmic variable distinguished from others by the presence of a powerful magnetic field in their white dwarfs.
When the white dwarf is moderately magnetic, accretion occurs through a truncated accretion disc in some CVs. These are referred to as intermediate polars (IPs). Observations show that in IPs, the magnetic white dwarf spins asynchronously with the system’s orbital period, resulting in a rapid oscillation with the spin period. As a result, determining the precise spin period and oscillation ephemeris may be the key to revealing the IP nature 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 additional 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) catalogue were used to supplement the study.
“We performed X-ray and optical timing analyses, as well as X-ray spectral analysis of a likely IP J0503,” the researchers wrote in their paper.
J0503 has an orbital period of approximately 81.65 minutes, according to the observations. Furthermore, astronomers discovered a 65.5-minute periodicity, which they attribute to the white dwarf’s spin period. If this is the case, J0503 would be the first nearly synchronous IP address below the period gap.
Astronomers believe J0503 is not synchronised because the secondary star has a low magnetic moment. As a result, it is unable to synchronise, as are nearly synchronous IPs and EX Hya-like systems.
The study discovered that J0503 is most likely accreting via stream-fed accretion. Furthermore, the identified 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 determined the fundamental parameters of J0503’s white dwarf. This star has a mass of about 0.54 solar masses, a mass accretion rate of 1.44 1010 solar masses per year, and a shock height of about 27.6 kilometres, according to the paper.