Astronomers discover a strange, catastrophically variable star

Astronomers discover a strange, catastrophically variable star

Top: ATLAS long-term light curve for J1344, consisting of c- and o-band observations. The shaded area indicates the time of the TESS observations. Middle: TESS light curve for J1344. Bottom: energy spectrum of the TESS light curve. Credit: Littlefield et al, 2023

Using NASA’s Transiting Exoplanet Survey Satellite (TESS), astronomers have discovered a strange cataclysmic variable star. The newly discovered system, SDSS J134441.83+204408.3 (or J1344 for short) is a highly asynchronous, short-range magnetic variable, despite its high surface field strength. The finding was reported in a paper published on January 13 in arXiv Prepress server.

Catastrophic variants (CVs) binary star systems It consists of a primary white dwarf accretion from an ordinary companion star. It irregularly increases in brightness by a large factor and then decreases again to a calm state. Polar is a subclass of catastrophic variables that are distinguished from other CVs by the presence of a very strong magnetic field in their white dwarfs.

when white dwarfs In CVs that have field strengths greater than 10 MG, their rotational frequency is expected to coincide with that of the binary orbital, due to the sharp radial dependence of the magnetic field. However, the team Astronomy scientists Led by Colin Littlefield of the Bay Area Environmental Research Institute in Moffett Field, California, he reported the discovery of a catastrophic variable that challenges these predictions, and thus challenges current theoretical models.

“What makes J1344 remarkable is the combination of three parameters: its moderately high magnetic field strength, its short orbital period, and its high degree of desynchronization. Together, these characteristics paint an interesting picture of the magnetic CV that is normally expected to be asynchronous, but is not.” , the researchers explained.

At a distance of about 1950 light yearsJ1344 was initially classified as bipolar. New TESS data indicate that J1344 has a high surface field strength of about 56 MG, a short orbital period of about 114 minutes, and therefore also a relatively short orbital separation. Furthermore, the new observations found that this system exhibits an asynchronous spin as the spin-to-orbit ratio is on the order of 0.893, which is unusual for magnetic CVs.

Astronomers have confirmed that the highly unsynchronized rotation in J1344 presents a challenge to theoretical studies of the evolution of the period of rotation. They noted that it proves that the surface field strength is higher than 10 MG and the short binary separation does not guarantee that the system will synchronize rapidly.

Overall, the researchers hypothesize that a combination of a weak magnetic substar or an unusually massive white dwarf is the most plausible hypothesis that could explain J1344’s failure to achieve a synchronous spin. According to them, the case of J1344 indicates that some other CVs classified as synchronous poles need to be reconsidered as they may be asynchronous systems.

“J1344’s ability to successfully masquerade as a synchronous electrode for a decade suggests that other nominally synchronous systems may also be desynchronous. It will be important to examine the optical TESS curves for all polarities to look for any such systems,” the authors said.

more information:
Colin Littlefield et al., SDSS J134441.83+204408.3: a highly asynchronous, short-range magnetic variable with a field strength of 56 MG, arXiv (2023). doi: 10.48550/arxiv.2301.05723

Journal information:

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