The scatter of the M dwarf mass–radius relationship
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Published version
Date
2018-11-21
Authors
Parsons, S.G.
Gänsicke, B.T.
Marsh, T.R.
Ashley, R.P.
Breedt, Elmé
Burleigh, M.R.
Copperwheat, C.M.
Green, M.J.
Hermes, James J.
Version
Published version
OA Version
Citation
S.G. Parsons, B.T. Gänsicke, T.R. Marsh, R.P. Ashley, E. Breedt, M.R. Burleigh, C.M. Copperwheat, V.S. Dhillon, M.J. Green, J.J. Hermes, P. Irawati, P. Kerry, S.P. Littlefair, A. Rebassa-Mansergas, D.I. Sahman, M.R. Schreiber, M. Zorotovic. 2018. "The scatter of the M dwarf mass–radius relationship." Monthly Notices of the Royal Astronomical Society, Volume 481, Issue 1, pp. 1083 - 1096. https://doi.org/10.1093/mnras/sty2345
Abstract
M dwarfs are prime targets in the hunt for habitable worlds around other stars. This is due to
their abundance as well as their small radii and low masses and temperatures, which facilitate
the detection of temperate, rocky planets in orbit around them. However, the fundamental
properties of M dwarfs are difficult to constrain, often limiting our ability to characterize the
planets they host. Here we test several theoretical relationships for M dwarfs by measuring
23 high-precision, model-independent masses and radii for M dwarfs in binaries with white
dwarfs.We find a large scatter in the radii of these low-mass stars, with 25 per cent having radii
consistent with theoretical models while the rest are up to 12 per cent overinflated. This scatter
is seen in both partially and fully convective M dwarfs. No clear trend is seen between the
overinflation and age or metallicity, but there are indications that the radii of slowly rotating
M dwarfs are more consistent with predictions, albeit with a similar amount of scatter in the
measurements compared to more rapidly rotating M dwarfs. The sample of M dwarfs in close
binaries with white dwarfs appears indistinguishable from other M dwarf samples, implying
that common envelope evolution has a negligible impact on their structure. We conclude that
theoretical and empirical mass–radius relationships lack the precision and accuracy required
to measure the fundamental parameters of M dwarfs well enough to determine the internal
structure and bulk composition of the planets they host.
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This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society, Volume 481, Issue 1, pp. 1083 - 1096. © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.