The EBLM project – VIII. First results for M-dwarf mass, radius, and effective temperature measurements using CHEOPS light curves

M Swayne , P Maxted (1) , A Triaud , S Sousa (2) , C Broeg , H-G Florén , P Guterman (3) , A Simon , I Boisse (3) , A Bonfanti , D Martin , A Santerne , S Salmon , M Standing , V Van grootel , T Wilson , Y Alibert , R Alonso , G Anglada escudé , J Asquier , T Bárczy , D Barrado , S Barros , M Battley , W Baumjohann , M Beck , T Beck , A Bekkelien , W Benz , Xavier Bonfils (4) , N Billot , A Brandeker , M-D Busch , J Cabrera , S Charnoz , A Collier cameron , Sz Csizmadia , M Davies , M Deleuil , A Deline , L Delrez , O Demangeon , B-O Demory , G Dransfield , D Ehrenreich , A Erikson , A Fortier , L Fossati , M Fridlund , D Futyan , D Gandolfi , M Gillon , M Guedel , G Hébrard , N Heidari , C Hellier , K Heng , M Hobson , S Hoyer , K Isaak , L Kiss , V Kunovac hodžić , S Lalitha , J Laskar (5) , A Lecavelier des etangs , M Lendl , C Lovis , D Magrin , L Marafatto , J Mccormac , N Miller , V Nascimbeni , G Olofsson , R Ottensamer , I Pagano , E Pallé , G Peter , G Piotto , D Pollacco , D Queloz , R Ragazzoni , N Rando , H Rauer , I Ribas , N Santos , G Scandariato , D Ségransan , A Smith , M Steinberger , M Steller , Gy Szabó , N Thomas , S Udry , I Walter , N Walton , E Willett

1 Keele University [Keele]
2 IASTRO - Instituto de Astrofísica e Ciências do Espaço
3 LAM - Laboratoire d'Astrophysique de Marseille
4 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble
5 IMCCE - Institut de Mécanique Céleste et de Calcul des Ephémérides

ABSTRACT The accuracy of theoretical mass, radius, and effective temperature values for M-dwarf stars is an active topic of debate. Differences between observed and theoretical values have raised the possibility that current theoretical stellar structure and evolution models are inaccurate towards the low-mass end of the main sequence. To explore this issue, we use the CHEOPS satellite to obtain high-precision light curves of eclipsing binaries with low-mass stellar companions. We use these light curves combined with the spectroscopic orbit for the solar-type companion to measure the mass, radius, and effective temperature of the M-dwarf star. Here, we present the analysis of three eclipsing binaries. We use the pycheops data analysis software to fit the observed transit and eclipse events of each system. Two of our systems were also observed by the TESS satellite – we similarly analyse these light curves for comparison. We find consistent results between CHEOPS and TESS, presenting three stellar radii and two stellar effective temperature values of low-mass stellar objects. These initial results from our on-going observing programme with CHEOPS show that we can expect to have ∼24 new mass, radius, and effective temperature measurements for very low-mass stars within the next few years.

Keywords: techniques: photometric; techniques: spectroscopic; binaries: eclipsing; stars: fundamental parameters; stars: low-mass; Astrophysics - Solar and Stellar Astrophysics; Astrophysics - Earth and Planetary Astrophysics

Domains: Astrophysics [astro-ph]

M Swayne, P Maxted, A Triaud, S Sousa, C Broeg, et al.. The EBLM project – VIII. First results for M-dwarf mass, radius, and effective temperature measurements using CHEOPS light curves. Monthly Notices of the Royal Astronomical Society, 2021, 506 (1), pp.306-322. ⟨10.1093/mnras/stab1687⟩. ⟨insu-03458355⟩