Study showed that HD 213258 is a rapidly oscillating magnetic Ap star

(ORDO NEWS) — Using the Canada-France-Hawaii Telescope (CFHT), astronomers observed the chemically peculiar star HD 213258 and found it to be a rapidly oscillating magnetic Ap star.

Chemically peculiar stars (CP stars) are stars with unusual metal abundances that can show strong or weak spectral lines for certain elements.

Some CP stars have stronger magnetic fields than classical class A or B stars, so they are known as magnetic chemically peculiar (mCP) stars (Ap and Bp stars).

HD 213258 is located about 363 light years away in the constellation Lizards. It is a star of spectral type A3E, which is about 2.4 times the size of the Sun.

Its absolute magnitude is 2.39 mag and its effective temperature ranges from 7500 to 10,000 K.

A team of astronomers led by Gauthier Mathis of the European Southern Observatory (ESO) in Chile observed HD 213258 using the CFHT’s ESPaDOnS spectrograph.

The observational campaign allowed scientists to gain more information about the nature of this star.

ESPaDOnS was used to record the Stokes I and V spectra of HD 213258 between November 2020 and October 2022.

The study was supplemented with data from the NASA TESS satellite and the CORAVEL spectrometer.

Observations showed that the average magnetic field modulus of HD 213258 is about 3.8 kG, without significant changes during the observation period. This discovery indicates that HD 213258 is an Ap star.

Astronomers have calculated that HD 213258 has a rotation period of about 50 years, making it one of the slowest-rotating Ap stars.

This star was also found to oscillate rapidly, exhibiting high overtone pulsations with a period of approximately 7.58 minutes.

Consequently, the researchers classified HD 213258 as a rapidly oscillating Ap star (roAp).

The radial velocity of HD 213258 exhibits small amplitude variations, suggesting that it may be a single line spectroscopic binary with a low mass companion.

The researchers suggest that the second object in this system could be a brown dwarf. If confirmed, HD 213258 would be the first known roAp star to have a brown dwarf companion.


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