J/MNRAS/508/5757 Synthetic spectra of red supergiants with winds (Davies+, 2021)
The impact of winds on the spectral appearance of red supergiants.
Davies B., Plez B.
<Mon. Not. R. Astron. Soc. 508, 5757 (2021)>
=2021MNRAS.508.5757D 2021MNRAS.508.5757D (SIMBAD/NED BibCode)
ADC_Keywords: Stars, supergiant ; Models ; Spectroscopy
Keywords: stars: evolution - stars: massive - supergiants - stars: late-type
Abstract:
The rate at which mass is lost during the Red Supergiant 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 which
include a wind, and use these models to compute synthetic spectra from
the optical to the mid-infrared. The inclusion of a wind has two
important effects. Firstly, 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 infrared. 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.
Description:
Spectra of Red Supergiants with a fixed effective temperature of
3800K, log(g)=0.0, and Solar metallicity, at five different mass-loss
rates (log(M☉/yr) = {-7.0, -6.0, -5.5, -5.0, -4.5} ). The
wavelength range spans 0.2um to 25um. Spectra are flux-sampled
following the MARCS convention (Gustafsson+, 2008A&A...486..951G 2008A&A...486..951G,),
and as such should not be used for equivalent width analysis of
individual lines as they are unresolved. Broad-band fluxes and
equivalent widths of molecular bands are accurate at the ∼percent
level.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 15 5 Details of spectra
sp/* . 5 Individual synthetic spectra
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 4 F4.1 [Msun/yr] log(dM/dt) Mass-loss rate
6- 15 A10 --- FileName Name of file containing the spectrum in
subdirectory sp
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Byte-by-byte Description of file: sp/*
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Bytes Format Units Label Explanations
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1- 10 F10.3 0.1nm lambda Wavelength in Angstroms
13- 25 E13.7 10mW/m2/nm Flux Flux in cgs units (erg/cm2/s/Å)
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Acknowledgements:
Ben Davies, b.davies(at)ljmu.ac.uk
References:
Gustafsson et al., 2008A&A...486..951G 2008A&A...486..951G,
A grid of MARCS model atmospheres for late-type stars.
I. Methods and general properties.
(End) Ben Davies [LJMU, United Kingdom], Patricia Vannier [CDS] 07-Sep-2021