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

TL;DR

This study uses CHEOPS and TESS satellite data to precisely measure the mass, radius, and temperature of low-mass M-dwarf stars, addressing discrepancies between observations and models.

Contribution

First results demonstrating the effectiveness of CHEOPS in measuring fundamental properties of M-dwarfs, with plans to expand the sample significantly.

Findings

Consistent measurements between CHEOPS and TESS data.

Initial measurements of stellar radii and temperatures for low-mass stars.

Projection of obtaining ~24 new measurements in the coming years.

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.