Utilizing the Canada-France-Hawaii Telescope (CFHT), astronomers have noticed a chemically peculiar star referred to as HD 213258. In consequence, they discovered that HD 213258 is a quickly oscillating, strongly magnetic Ap star. The discovering is reported in a paper printed December 24 on the arXiv pre-print server.
Chemically peculiar (CP) stars are these with uncommon steel abundances, thus exhibiting sturdy or weak spectral traces for sure parts. Some CP stars are noticed to have stronger magnetic fields than classical A- or B-type stars, various from few tens of Gauss (G) to tens of kiloGauss (kG), and are therefore referred to as magnetic chemically peculiar (mCP) stars (Ap and Bp stars). This class of objects is perceived by astronomers as a pure atomic and magnetic laboratory to check stellar formation and evolution.
Situated some 363 light years away within the constellation of Lacerta, HD 213258 (also called BD+35 4815) is CP star of spectral kind A3E, estimated to be some 2.4 instances greater than the sun. The star’s absolute magnitude is 2.39 magazine and its effective temperature is estimated to be between 7,500 and 10,000 Ok.
Just lately, a gaggle of astronomers led by Gautier Mathys of European Southern Observatory (ESO) in Chile, has noticed HD 213258 with the ESPaDOnS spectrograph at CFHT. The observational campaign allowed them to unveil extra insights into the character of this star.
“We report about HD 213258, an Ap star that we not too long ago recognized as presenting a singular mixture of uncommon, outstanding properties,” the researchers wrote within the paper.
ESPaDOnS was used to report Stokes I and V spectra of HD 213258 at seven epochs between November 2020 and October 2022. The examine was complemented by information from NASA’s Transiting Exoplanet Survey Satellite tv for pc (TESS) and from the CORrelation-RAdial-VELocities (CORAVEL) spectrometer.
The observations discovered that the imply magnetic field modulus of HD 213258 is about 3.8 kG, with no vital variations over the observing interval of two years. This discovering signifies that HD 213258 is a strongly magnetic Ap star.
The astronomers estimated that the stellar rotation interval of HD 213258 is of the order of fifty years, making it one of many slowest rotating Ap stars identified up to now. It was additionally discovered that this star is quickly oscillating, exhibiting excessive overtone pulsations with a interval of roughly 7.58 minutes. Therefore, the researchers categorised HD 213258 as a roAp—quickly oscillating Ap star.
Moreover, it turned out that the radial velocity of HD 213258 exhibits low amplitude variations, which means that it might be a single-line spectroscopic binary system with a low-mass companion. The researchers assume that the secondary object on this system could also be a brown dwarf. If confirmed, it will make HD 213258 the primary roAp star identified to have a brown dwarf companion.
Extra data:
Gautier Mathys et al, HD 213258: a brand new quickly oscillating, super-slowly rotating, strongly magnetic Ap star in a spectroscopic binary, arXiv (2022). DOI: 10.48550/arxiv.2212.12752
Journal data:
arXiv
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