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The EBLM project X. benchmark masses, radii and temperatures for two fully convective M-dwarfs using K2

Duck, Alison; Martin, David V; Gill, Sam; Armitage, Tayt; Rodríguez Martínez, Romy; Maxted, Pierre F L; Sebastian, Daniel; Sethi, Ritika; Swayne, Matthew I; Cameron, Andrew Collier; Dransfield, Georgina; Gaudi, B Scott; Gillon, Michael; Hellier, Coel; Kunovac, Vedad; Lovis, Christophe; McCormac, James; Pepe, Francesco A; Pollacco, Don; Sairam, Lalitha; Santerne, Alexandre; Ségransan, Damien; Standing, Matthew R; Southworth, John; Triaud, Amaury H M J; Udry, Stephane

The EBLM project X. benchmark masses, radii and temperatures for two fully convective M-dwarfs using K2 Thumbnail


Alison Duck

David V Martin

Sam Gill

Tayt Armitage

Romy Rodríguez Martínez

Daniel Sebastian

Ritika Sethi

Matthew I Swayne

Andrew Collier Cameron

Georgina Dransfield

B Scott Gaudi

Michael Gillon

Vedad Kunovac

Christophe Lovis

James McCormac

Francesco A Pepe

Don Pollacco

Lalitha Sairam

Alexandre Santerne

Damien Ségransan

Matthew R Standing

John Southworth

Amaury H M J Triaud

Stephane Udry


M-dwarfs are the most abundant stars in the galaxy and popular targets for exoplanet searches. However, their intrinsic faintness and complex spectra inhibit precise characterisation. We only know of dozens of M-dwarfs with fundamental parameters of mass, radius and effective temperature characterised to better than a few per cent. Eclipsing binaries remain the most robust means of stellar characterisation. Here we present two targets from the Eclipsing Binary Low Mass (EBLM) survey that were observed with K2: EBLM J0055-00 and EBLM J2217-04. Combined with HARPS and CORALIE spectroscopy, we measure M-dwarf masses with precisions better than 5%, radii better than 3% and effective temperatures on order 1%. However, our fits require invoking a model to derive parameters for the primary star and fitting the M-dwarf using the transit and radial velocity observations. By investigating three popular stellar models, we determine that the model uncertainty in the primary star is of similar magnitude to the statistical uncertainty in the model fits of the secondary M-dwarf. Therefore, whilst these can be considered benchmark M-dwarfs, we caution the community to consider model uncertainty when pushing the limits of precise stellar characterisation.


Duck, A., Martin, D. V., Gill, S., Armitage, T., Rodríguez Martínez, R., Maxted, P. F. L., …Udry, S. (2023). The EBLM project X. benchmark masses, radii and temperatures for two fully convective M-dwarfs using K2. Monthly Notices of the Royal Astronomical Society, 521(4), 6305-6317.

Journal Article Type Article
Acceptance Date Jan 27, 2023
Online Publication Date Feb 24, 2023
Publication Date 2023-06
Publicly Available Date May 30, 2023
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Oxford University Press
Peer Reviewed Peer Reviewed
Volume 521
Issue 4
Pages 6305-6317
Keywords techniques; photometric - techniques; spectroscopic - binaries eclipsing - stars; fundamental parameters - stars; low-mass
Publisher URL


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