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@article{2253754,
author = {Mikulášek, Zdeněk and Semenko, Evgeniy and Paunzen, Ernst and Huemmerich, Stefan and North, Pierre L. and Bernhard, Klaus and Krtička, Jiří and Janík, Jan},
article_location = {LES ULIS CEDEX A},
article_number = {December},
doi = {http://dx.doi.org/10.1051/0004-6361/202243622},
keywords = {stars: chemically peculiar; stars: variables: general; stars: rotation},
language = {eng},
issn = {0004-6361},
journal = {Astronomy and Astrophysics},
title = {HD 60431, the CP2 star with the shortest rotational period Physical parameters and period analysis},
url = {https://www.aanda.org/articles/aa/full_html/2022/12/aa43622-22/aa43622-22.html},
volume = {668},
year = {2022}
}
TY - JOUR
ID - 2253754
AU - Mikulášek, Zdeněk - Semenko, Evgeniy - Paunzen, Ernst - Huemmerich, Stefan - North, Pierre L. - Bernhard, Klaus - Krtička, Jiří - Janík, Jan
PY - 2022
TI - HD 60431, the CP2 star with the shortest rotational period Physical parameters and period analysis
JF - Astronomy and Astrophysics
VL - 668
IS - December
SP - 1-13
EP - 1-13
PB - EDP Sciences
SN - 00046361
KW - stars: chemically peculiar
KW - stars: variables: general
KW - stars: rotation
UR - https://www.aanda.org/articles/aa/full_html/2022/12/aa43622-22/aa43622-22.html
N2 - Context. CP2 stars show periodic photometric, spectroscopic, and magnetic variations with the rotational period. They are generally slow rotators, with rotational periods exceeding half a day, except for the late B-type star HD 60431, which has an unusually short rotational period of 0.4755 days. As slow rotation is deemed a necessary criterion for the establishment of chemical peculiarities, this characteristic renders HD 60431 a special object that might o ffer valuable insight into, and constraints on, the formation and evolution of CP2 stars. Aims. The aims of our study are to analyse the light variability, derive atmospheric abundances, and determine the detailed physical parameters of HD 60431 to confirm its status as the CP2 star with the shortest known rotational period, with special emphasis on the rotational period evolution. Methods. Photometric indices and high-resolution spectroscopy were employed to derive the physical parameters, evolutionary status, and atmospheric abundances of our target star. A light variability study was carried out using combined sets of photometric data from ground- and space-based facilities. A circularly polarised spectrum was employed to check the presence of a longitudinal magnetic field in the star. Results. With an age of only 10 Myr, an e ffective temperature of T-eff = 13 000 +/- 300 K, surface gravity log g = 4:10 +/- 0:10, radius R = 1:97 +/- 0:09 R-circle dot, and mass M = 3:1 +/- 0:1 M-circle dot, HD 60431 is situated close to the zero age main sequence; it is a member of the open cluster NGC 2547 in the Vela OB2 complex. We confirm its status as a classical late B-type CP2 star showing strong overabundances of Mg (1.8 dex), Si (1.9 dex), Ca (1.6 dex), Ti (2.2 dex), and Fe (1.8 dex). No conclusive evidence for the presence of a strong magnetic field was found in the available spectroscopic data. The light curve of HD 60431 has remained constant over the last four decades. The available photometric time series data confirm the short rotational period and indicate a slight secular increase in the rotational period of <(P)over dot> = 2:36(19) x 10(-10) = 7:5 (6) ms yr(-1). The following quadratic ephemeris has been derived: HJD(min)(E) = 2 459 212:969 35 + 0(d).475 516 64 E + 5(d).62 x 10(-11)E(2). Conclusions. HD 60431 is indeed the CP2 star with the shortest known rotational period. Theory needs to explain the establishment and maintenance of chemical peculiarities in such a young and fast-rotating object. Our results furthermore raise the question of whether period variability on timescales significantly shorter than stellar evolution is inherent to all magnetic chemically peculiar stars.
ER -
MIKULÁŠEK, Zdeněk, Evgeniy SEMENKO, Ernst PAUNZEN, Stefan HUEMMERICH, Pierre L. NORTH, Klaus BERNHARD, Jiří KRTIČKA and Jan JANÍK. HD 60431, the CP2 star with the shortest rotational period Physical parameters and period analysis. \textit{Astronomy and Astrophysics}. LES ULIS CEDEX A: EDP Sciences, 2022, vol.~668, December, p.~1-13. ISSN~0004-6361. Available from: https://dx.doi.org/10.1051/0004-6361/202243622.
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