An M Dwarf Companion to an F-Type Star in a Young Main-Sequence Binary

Abstract

Only a few well characterized very low-mass M dwarfs are known today. Our understanding of M dwarfs is vital as these are the most common stars in our solar neighborhood. We aim to characterize the properties of a rare F+dM stellar system for a better understanding of the low-mass end of the Hertzsprung-Russel diagram. We used photometric light curves and radial velocity follow-up measurements to study the binary. Spectroscopic analysis was used in combination with isochrone fitting to characterize the primary star. The primary star is an early F-type main-sequence star with a mass of (1.493 ± 0.073) M e and a radius of (1.474 ± 0.040) R e . The companion is an M dwarf with a mass of (0.188 ± 0.014) M e and a radius of (0.234 ± 0.009) R e . The orbital period is (1.35121±0.00001) days. The secondary star is among the lowest-mass M dwarfs known to date. The binary has not reached a 1:1 spin-orbit synchronization. This indicates a young main-sequence binary with an age below ∼250 Myr. The mass-radius relation of both components are in agreement with this finding.

The Transit and Light Curve Modeller

“…Similar studies support these findings (e.g. Vida et al 2009;Eigmüller et al 2016, and references therein). These findings were later further confirmed by using the first data release of Gaia measurements: Jackson et al (2016) highlighted that main-sequence stars in open clusters of age 5-140 Myr have radii bigger by 10 per cent than those predicted by standard evolutionary models (the difference is even larger for pre-MS stars according to them).…”

“…7b,11b,18b,19b,20b), a complete description has never been published. TLCM has a long list of further applications, including Kepler-90's seven transiting planet systems (Cabrera et al 2014) and other K2-objects (Eigmüller et al 2016(Eigmüller et al , 2017, Korth et al 2019 among other space-based and groundbased photometric results (Rauer et al 2009(Rauer et al , 2010Bordé et al 2010;Cabrera et al 2010Cabrera et al , 2015Csizmadia et al 2010Csizmadia et al , 2011Csizmadia et al , 2013Csizmadia et al , 2015Deeg et al 2010;Fridlund et al 2010;Gandolfi et al 2010Gandolfi et al , 2013Bouchy et al 2011;Hébrard et al 2011;Guenther et al 2012;Ollivier et al 2012;Paetzold et al 2012;Rouan et al 2012;Klagyivik et al 2016). The agreement between TLCM and JKTEBOP was found to be excellent in Soutworth (2012) for the checked cases.…”

A low-mass eclipsing binary within the fully convective zone from the Next Generation Transit Survey

“…There are additional systems known such as AD2615 which is a young (age ∼ 800 Myr) system reported to be a member of the Praesepe open star cluster (Gillen et al 2017), JW 380, which is a pre-main sequence binary of age 2-3 Myr with masses 0.26±0.02 and 0.15±0.01 M (Irwin et al 2007) and 2MASS02405152+5245066, a 250 Myr F star+ low mass M dwarf (0.188± 0.014 M ) system (Eigmüller et al 2016). However, these young systems are expected to have faster rotation and more activity than older, field age systems such as NGTS J052218.2-250710.4 and so we limit our discussion to field age M dwarfs only.…”

Revising the properties of low mass eclipsing binary stars using TESS light curves

“…Comparisons to theoretical models by the previous authors indicate that the secondary has an inflated radius even when correcting the isochrones for 5% of the discrepancy observed among low-mass stars. This might be due to the fact that the system is young; Eigmüller et al (2016) estimate a synchronization factor of P rot /P orb = 0.43 ± 0.05 leading to an upper limit to the age of this system of 120-250 Myr via synchronization timescales. Those authors also derive a statistically insignificant value for the eccentricity, e = 0.070 ± 0.063, in agreement with our value (Table 3).…”