Two intermediate polars investigated by astronomers

By analyzing the long-term, high-cadence steady photometry from NASA’s Transiting Exoplanet Survey Satellite tv for pc (TESS), astronomers have investigated UU Columbae and Swift J0939.7-3224—two intermediate polars. Outcomes of the research, offered July 24 on the preprint server arXiv, yield essential insights into the properties of those two techniques.

Cataclysmic variables (CVs) are binary star techniques consisting of a white dwarf accreting materials from a traditional star companion. They irregularly improve in brightness by a big issue, then drop again right down to a quiescent state. Polars are a subclass of cataclysmic variables distinguished from different CVs by the presence of a really sturdy magnetic discipline of their white dwarfs.

In some CVs, accretion happens by means of a truncated accretion disk when the white dwarf is reasonably magnetic. These techniques are generally known as intermediate polars (IPs). Observations have proven that in IPs, the magnetic white dwarf spins asynchronously with the orbital interval of the system and subsequently produces a fast oscillation with the spin interval. Due to this fact, figuring out exact spin interval and exact oscillation ephemeris might be the important thing to disclose the IP nature of some CVs.

UU Columbae, or UU Col for brief (discovery identify: RX J0512.2-3241) was recognized as a delicate X-ray intermediate polar in 1996, at a distance of some 8,300 light years. Its orbital and spin intervals had been measured to be 3.45 hours and 863 seconds, respectively. The system showcases polarized variability, which is probably because of the cyclotron emission from two poles.

Swift J0939.7-3224, or J0939 for brief, is a candidate IP detected in 2015. Earlier research of this supply have provisionally advised that its orbital and spin intervals are roughly 8.5 hours and a pair of,670 seconds, respectively.

Lately, a group of astronomers led by Nikita Rawat of the Aryabhatta Analysis Institute of observational sciencES (ARIES) in India, determined to discover UU Col and J0939 with TESS, with the intention to shed extra mild on their nature.

The observations UU Col revealed short-term variations superimposed on long-term variability. The collected knowledge allowed the astronomers to revise orbital and spin intervals of this IP as 3.46 hours and 863.74 seconds, respectively. The beat interval of UU Col was discovered to be about 928 seconds. The researchers famous that their findings on the whole point out that this method is a disk-fed dominated disk-overflow accretor.

With regards to J0939, its TESS mild curve showcases a transparent variability sample. The orbital and spin intervals had been refined as 8.49 hours and 2671.8 seconds, respectively. Furthermore, the presence of spin period within the TESS energy spectrum of J0939 confirmed its IP nature.

The authors of the paper additionally report the absence of beat frequency in J0939, which means that it could be a pure disk-fed accretor. Nonetheless, X-ray observations of this method are required with the intention to verify this assumption.

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