Astronomers have found the fastest-rotating white dwarf known to date. It completes one revolution around its axis in 29.6 seconds and is part of the intermediate polar — a type of cataclysmic binary system. A Preprint of the paper is published on the website arXiv.org.
Cataclysmic variables are tight binary systems consisting of a white dwarf and an ordinary star or giant that exhibit uneven strong changes in their brightness. In such systems, the white dwarf actively selects the substances of its companion star, forming an accretion disk around itself. Cataclysmic variables are divided into several classes, one of them being polars, in which a white dwarf, possessing a sufficiently powerful magnetic field, is able to destroy the accretion disk around itself. However there are so-called intermediate polars in which the outer part of the accretion disk may exist, however, as it approaches the white dwarf, the substance will follow the force lines of its dipole magnetic field, hitting the regions of the dwarf's poles and creating a stream of x-ray radiation.
A team of astronomers led by Raimundo Lopes de Oliveira from the Federal University of Sergipe published the results of observations of the CTCV J2056-3014 system using the XMM-Newton x-ray space telescope. The system is located at a distance of about 853 light-years from the Sun and was considered a candidate for intermediate polars with a period of rotation of the components around each other in 1.76 hours. The total luminosity of the system in the energy range of x-ray quanta of 0.3-12 kilo electronvolts was about 1.8×1031 erg per second, in addition, there is no significant absorption of x-ray radiation. This allowed astronomers to classify CTCV J2056-3014 as an intermediate low-luminosity polar in which there is a moderate (6×10-12 mass of the Sun per year) accretion of matter from a companion star to a white dwarf with a not very large magnetic field. A unique feature of this system was the speed of rotation of the white dwarf, determined by the radiation pulsations, — it makes one revolution around its axis in 29.6 seconds, which is a record value for today. Astronomers assume that there may be quite a lot of systems like CTCV J2056-3014, and the eROSITA telescope installed at the Russian-German space Observatory Spektr-RG should help find them.
Earlier, we talked about how a new x-ray Eclipse pole was a found-an unusual and rare type of cataclysmic variable system.
Photo: Mark A.Garlick