The EBLM project – XIV. TESS light curves for eclipsing binaries with very low mass companions

Fitzpatrick, Jay; Maxted, Pierre F L; Freckelton, Alix V; Triaud, A H M J; Martin, D V; Duck, A

Abstract

Accurate limb-darkening models are needed for accurate characterisation of eclipsing binary stars and transiting exoplanets from the analysis of their light curves. The limb-darkening observed in solar-type stars from the analysis of light curves for transiting hot-Jupiter exoplanets are systematically less steep than predicted by stellar model atmospheres that do not account for the stellar magnetic field. Hot-Jupiter host stars tend to be metal rich ([Fe/H] ≈ 0.25) leading to a lack of low- and solar-metallicity targets in previous studies, so we have analysed the TESS light curves for a sample of 19 stars with transiting M-dwarf companions to extend the range of limb-darkening measurements to [Fe/H] values more typical for solar-type stars. We find that the systematic offset between the observed and predicted limb-darkening profiles observed in metal-rich hot-Jupiter systems is also observed for these solar-type stars at lower metallicity. These observations provide additional measurements to explore the impact of magnetic fields on the atmospheres of solar-type stars. We have also used the TESS light curves to make precise estimates of the radius and effective temperature of the M-dwarf companions in these 19 binary systems. We confirm the results from previous studies that find very low mass stars tend to be about 3percnt larger than predicted by stellar models that use a mixing length prescription calibrated on the Sun.

Citation

Fitzpatrick, J., Maxted, P. F. L., Freckelton, A. V., Triaud, A. H. M. J., Martin, D. V., & Duck, A. (in press). The EBLM project – XIV. TESS light curves for eclipsing binaries with very low mass companions. Monthly Notices of the Royal Astronomical Society, 537(4), 3943–3953. https://doi.org/10.1093/mnras/staf268

• Journal Article Type: Article
• Acceptance Date: Feb 4, 2025
• Online Publication Date: Feb 13, 2025
• Deposit Date: Mar 6, 2025
• 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: 537
• Issue: 4
• Pages: 3943–3953
• DOI: https://doi.org/10.1093/mnras/staf268
• Keywords: binaries, eclipsing – stars, fundamental parameters – stars, low-mass – stars, solar-type
• Public URL: https://keele-repository.worktribe.com/output/1080571