A study of the F-giant star θ Scorpii A: a post-merger rapid rotator?
Article
Article Title | A study of the F-giant star θ Scorpii A: a post-merger rapid rotator? |
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ERA Journal ID | 1074 |
Article Category | Article |
Authors | Lewis, Fiona, Bailey, Jeremy, Cotton, Daniel V., Howarth, Ian D., Kedziora-Chudczer, Lucyna and van Leeuwen, Floor |
Journal Title | Monthly Notices of the Royal Astronomical Society |
Journal Citation | 513 (1), pp. 1129-1140 |
Number of Pages | 12 |
Year | 2022 |
Publisher | Oxford University Press |
Place of Publication | United Kingdom |
ISSN | 0035-8711 |
1365-2966 | |
Digital Object Identifier (DOI) | https://doi.org/10.1093/mnras/stac991 |
Web Address (URL) | https://academic.oup.com/mnras/article/513/1/1129/6565806 |
Abstract | We report high-precision observations of the linear polarization of the F1III star θ Scorpii. The polarization has a wavelength dependence of the form expected for a rapid rotator, but with an amplitude several times larger than seen in otherwise similar main-sequence stars. This confirms the expectation that lower-gravity stars should have stronger rotational-polarization signatures as a consequence of the density dependence of the ratio of scattering to absorption opacities. By modelling the polarization, together with additional observational constraints (incorporating a revised analysis of Hipparcos astrometry, which clarifies the system's binary status), we determine a set of precise stellar parameters, including a rotation rate ω (= Ω/Ωc ≥ 0.94, polar gravity log (gp)= 2.091 +0.042-0.039 (dex cgs), mass 3.10 +0.37-0.32 M⊙, and luminosity log (L/L⊙) =3.149+0.041-0.028. These values are incompatible with evolutionary models of single rotating stars, with the star rotating too rapidly for its evolutionary stage, and being undermassive for its luminosity. We conclude that θ Sco A is most probably the product of a binary merger. |
Keywords | binaries: Close; polarization; stars: Evolution; stars: Rotation; techniques: Polarimetric |
ANZSRC Field of Research 2020 | 5101. Astronomical sciences |
Public Notes | This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2022 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. |
Byline Affiliations | University of New South Wales |
Monterey Institute for Research in Astronomy, United States | |
Australian National University | |
Western Sydney University | |
Centre for Astrophysics | |
University College London, United Kingdom | |
University of Cambridge, United Kingdom |
https://research.usq.edu.au/item/wz7x0/a-study-of-the-f-giant-star-scorpii-a-a-post-merger-rapid-rotator
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