Astronomers explore highly variable polar V496 UMa

(ORDO NEWS) — By analyzing data from ESA’s XMM-Newton spacecraft and NASA’s TESS telescope, German astronomers have studied the highly variable polar star known as V496 UMa. The results of the study provide more clues about the properties and nature of this object.

Cataclysmic variables (CVs) are binary star systems consisting of a white dwarf and a normal companion star. They periodically increase the brightness to a large extent, and then return to a dormant state. Polaris are a subclass of cataclysmic variables, distinguished from other CPs by the presence of a very strong magnetic field in their white dwarfs.

The source V496 UMa, located about 2,470 light-years from Earth, was originally identified as CV in 2012 when it changed its brightness by about 2 mag within 30 minutes.

Further observations of this source confirmed that it is a non-exlibrating polar source. The orbital light curve of this system exhibits a structure with two peaks, with the amplitude of the second jump varying greatly.

Now, Samet Ok and Axel Schwope of the Leibniz Institute for Astrophysics in Potsdam, Germany, have decided to review archived data from XMM-Newton and TESS in hopes of gaining more insight into the properties of this highly variable polar star.

The study confirmed that V496 UMa exhibits highly variable optical light curve behavior. The shape of the light curve is characterized by two alternating humps with different brightness. The system exhibits periodic variability with a period of approximately 91.06 minutes, identified as an orbital period.

In addition, the X-ray light curve of V496 UMa has a double hump and a pronounced dip. The source was also found to exhibit a multi-temperature spectrum in X-rays. It has noticeable black body radiation at soft x-ray energy, which is typical of polars.

It has also been found that V496 UMa experiences two distinct states of mass accretion in the spectral energy distribution – an active state at various brightness levels and an inactive or low state.

Trying to determine the fundamental parameters of V496 UMa, the researchers concluded that the system most likely consists of a donor star of the main sequence of the spectral type M5.0 and a white dwarf with a mass of about 0.8 solar masses and an effective temperature of no higher than 9726.85 ° FROM.


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