On the rotational velocity of Sirius A
Abstract
With an aim of getting information on the equatorial rotation velocity (v_{e}) of Sirius A separated from the inclination effect (sin=i), a detailed profile analysis based on the Fourier transform technique was carried out for a large number of spectral lines, while explicitly taking into account the linebyline differences in the centrelimb behaviours and the gravity darkening effect (which depend on the physical properties of each line) based on model calculations. The simulations showed that how the firstzero frequencies (q_{1}) of Fourier transform amplitudes depends on v_{e} is essentially determined by the temperaturesensitivity parameter (K) differing from line to line, and that Fe=I lines (especially those of very weak ones) are more sensitive to v_{e} than Fe=II lines. The following conclusions were drawn by comparing the theoretical and observed q_{1} values for many Fe=I and Fe=II lines: (1) The projected rotational velocity (v_{e}sin=i) for Sirius A is fairly well established at 16.3(±0.1) km s^{1} by requiring that both Fe=I and Fe=II lines yield consistent results. (2) Although precise separation of v_{e} and i is difficult, v_{e} is concluded to be in the range of $16 \le v_{\rm e} \lesssim$ 3040 km s^{1}, which corresponds to $25^{\circ } \lesssim i \le 90^{\circ }$ . Accordingly, Sirius A is an intrinsically slow rotator for an Atype star, being consistent with its surface chemical peculiarity.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 November 2020
 DOI:
 10.1093/mnras/staa2869
 arXiv:
 arXiv:2009.07143
 Bibcode:
 2020MNRAS.499.1126T
 Keywords:

 stars: atmospheres;
 stars: chemically peculiar;
 stars: earlytype;
 stars: individual: Sirius;
 stars: rotation;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 17 pages, 11 figures, with online supplementary data