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The impact of winds on the spectral appearance of red supergiants

Davies, B and Plez, B (2021) The impact of winds on the spectral appearance of red supergiants. Monthly Notices of the Royal Astronomical Society, 508 (4). pp. 5757-5765. ISSN 0035-8711

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The rate at which mass is lost during the red supergiant (RSG) evolutionary stage may strongly influence how the star appears. Though there have been many studies discussing how RSGs appear in the mid- and far-infrared (IR) as a function of their mass-loss rate, to date, there have been no such investigations at optical and near-IR wavelengths. In a preliminary study, we construct model atmospheres for RSGs that include a wind, and use these models to compute synthetic spectra from the optical to the mid-IR. The inclusion of a wind has two important effects. First, higher mass-loss rates result in stronger absorption in the TiO bands, causing the star to appear as a later spectral type despite its effective temperature remaining constant. This explains the observed relation between spectral type, evolutionary stage, and mid-IR excess, as well as the mismatch between temperatures derived from the optical and IR. Secondly, the wind mimics many observed characteristics of a 'MOLsphere', potentially providing an explanation for the extended molecular zone inferred to exist around nearby RSGs. Thirdly, we show that wind fluctuations can explain the spectral variability of Betelgeuse during its recent dimming, without the need for dust.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2021 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Uncontrolled Keywords: Science & Technology; Physical Sciences; Astronomy & Astrophysics; stars: evolution; stars: massive; supergiants; stars: late-type; STARS ALPHA-ORIONIS; MASS-LOSS RATES; COOL; EVOLUTION; ATMOSPHERE; MODEL; AGB; ABUNDANCES; PROBES; astro-ph.SR; astro-ph.SR; 0201 Astronomical and Space Sciences; Astronomy & Astrophysics
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Divisions: Astrophysics Research Institute
Publisher: Oxford University Press
SWORD Depositor: A Symplectic
Date Deposited: 09 May 2022 11:23
Last Modified: 09 May 2022 11:30
DOI or ID number: 10.1093/mnras/stab2645
URI: https://researchonline.ljmu.ac.uk/id/eprint/16778
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