New observational constraints on the winds of M dwarf stars
Abstract
High resolution UV spectra of stellar H I Lyα lines from the Hubble Space Telescope (HST) provide observational constraints on the winds of coronal main sequence stars, thanks to an astrospheric absorption signature created by the interaction between the stellar winds and the interstellar medium. We report the results of a new HST survey of M dwarf stars, yielding six new detections of astrospheric absorption. We estimate mass-loss rates for these detections, and upper limits for nondetections. These new constraints allow us to characterize the nature of M dwarf winds and their dependenceon coronal activity for the first time. For a clear majority of the M dwarfs, we find winds that are weaker or comparable in strength to that of the Sun, i.e. M˙ ≤ 1 M˙⊙. However, two of the M dwarfs have much stronger winds: YZ CMi (M4 Ve; M˙ = 30M˙⊙) and GJ 15AB (M2 V+M3.5 V; M˙ = 10 M˙⊙). Even these winds are much weaker than expectations if the solar relation between flare energy and coronal mass ejection (CME) mass extended to M dwarfs. Thus, the solar flare/CME relation does not appear to apply to M dwarfs, with important ramifications for the habitability of exoplanets around M dwarfs. There is evidence for some increase in M˙ with coronal activity as quantified by X-ray flux, but with much scatter. One or more other factors must be involved in determining wind strength besides spectral type and coronal activity, with magnetic topology being one clear possibility.
Citation
Wood , B E , Muller , H-R , Redfield , S , Konow , F , Vannier , H , Linsky , J L , Youngblood , A , Vidotto , A A , Jardine , M , Alvarado-Gomez , J D & Drake , J J 2021 , ' New observational constraints on the winds of M dwarf stars ' , Astrophysical Journal , vol. 915 , no. 1 , 37 . https://doi.org/10.3847/1538-4357/abfda5
Publication
Astrophysical Journal
Status
Peer reviewed
ISSN
0004-637XType
Journal article
Description
A.A.V. acknowledges funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No 817540, ASTROFLOW).Collections
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