Cataclysmic variables (CVs) are binary star systems with a white dwarf and a normal star as a companion. The white dwarf is often referred to as the “Primary” star and the normal star as the “Companion” or “Secondary” star. These star systems are typically small, about the size of the Earth and moon system. The companion star loses material onto the white dwarf via accretion. Due to the white dwarf’s immense gravity, some of this material is converted into X-rays.
These binaries irregularly increase in brightness by a large factor, then drop down to a quiescent state. There are probably millions of CVs in our galaxy; however, only a few hundred have been studied in X-rays do far.
An international team of astronomers led by Richard Ashley from the University of Warwick, U.K., conducted spectroscopic and photometric observations of a cataclysmic variable (CV) known as V1460 Her after its latest outburst in 2016. The study’s main goal was to shed more light on the parameters of V1460 Her and the nature of the companion star in the system. The findings are published in arXiv.org.
The astronomers used the Warwick 1-meter telescope and the William Herschel Telescope (WHT), located on the island of La Palma. With data from the Hubble Space Telescope (HST) and surveys like SuperWASP or ASAS-SN complementing their study.
Based on the observation, the V1460 Her is an eclipsing CV with an orbital period of 4.99 hours, containing an over-luminous K5-type donor star. Past observations of this binary have shown that the companion star dominates the flux in the visible and near-infrared part of the spectrum and that it experienced two outbursts in the last 14 years.
The white dwarf and the companion star have masses of about 0.87 and 0.28 solar masses, with the latter having a radius of 0.43 solar radii. The results indicate the companion star to be 50% oversized as expected for a K5-type star of this mass.
The astronomers assume that the companion star’s derived parameters in V1460 Her suggest that it is probably the remnant of a high-rate mass transfer phase. The mass loss has happened on a timescale shorter than the donor’s Kelvin-Helmholtz (thermal) timescale of around 70 million years.
Further observations revealed that the V1460 Her exhibits strong pulsations on a period of 39 seconds. Making it one of the fastest-spinning white dwarfs in CVs studied so far.
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