NGTS-EB-7, an eccentric, long-period, low-mass eclipsing binary

Rodel, Toby; Watson, Christopher A; Ulmer-Moll, Solène; Gill, Samuel; Maxted, Pierre F L; Casewell, Sarah L; Brahm, Rafael; Wilson, Thomas G; Costes, Jean C; Eschen, Yoshi Nike Emilia; Doyle, Lauren; Freckelton, Alix V; Alves, Douglas R; Apergis, Ioannis; Bayliss, Daniel; Bouchy, Francois; Burleigh, Matthew R; Dumusque, Xavier; Eberhardt, Jan; Fernández, Jorge Fernández; Gillen, Edward; Goad, Michael R; Hawthorn, Faith; Helled, Ravit; Henning, Thomas; Hobbs, Katlyn L; Jenkins, James S; Jordán, Andrés; Kendall, Alicia; Lendl, Monika; McCormac, James; de Mooij, Ernst J W; O’Brien, Sean M; Saha, Suman; Pinto, Marcelo Tala; Trifonov, Trifon; Udry, Stéphane; Wheatley, Peter J

Abstract

Despite being the most common types of stars in the Galaxy, the physical properties of late M dwarfs are often poorly constrained. A trend of radius inflation compared to evolutionary models has been observed for earlier type M dwarfs in eclipsing binaries, possibly caused by magnetic activity. It is currently unclear whether this trend also extends to later type M dwarfs below the convective boundary. This makes the discovery of lower-mass, fully convective, M dwarfs in eclipsing binaries valuable for testing evolutionary models – especially in longer-period binaries where tidal interaction between the primary and secondary is negligible. With this context, we present the discovery of the NGTS-EB-7 AB system, an eclipsing binary containing a late M dwarf secondary and an evolved G-type primary star. The secondary star has a radius of 0.125 ± 0.006 R⊙, a mass of $0.096^{+0.003}_{-0.004}$ M⊙ and follows a highly eccentric (e=0.71436 ± 0.00085) orbit every 193.35875 ± 0.00034 days. This makes NGTS-EB-7 AB the third longest-period binary system with a secondary smaller than 200 MJ with the mass and radius constrained to better than 5 %. In addition, NGTS-EB-7 is situated near the centre of the proposed LOPS2 southern field of the upcoming PLATO mission, allowing for detection of the secondary eclipse and measurement of the companion’s temperature. With its long-period and well-constrained physical properties - NGTS-EB-7 B will make a valuable addition to the sample of M dwarfs in eclipsing binaries and help in determining accurate empirical mass/radius relations for later M dwarf stars.

Citation

Rodel, T., Watson, C. A., Ulmer-Moll, S., Gill, S., Maxted, P. F. L., Casewell, S. L., …Wheatley, P. J. (in press). NGTS-EB-7, an eccentric, long-period, low-mass eclipsing binary. Monthly Notices of the Royal Astronomical Society, 1-22. https://doi.org/10.1093/mnras/stae2799

• Journal Article Type: Article
• Acceptance Date: Dec 20, 2024
• Online Publication Date: Dec 20, 2024
• Deposit Date: Jan 27, 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
• Article Number: stae2799
• Pages: 1-22
• DOI: https://doi.org/10.1093/mnras/stae2799
• Keywords: stars: binaries: eclipsing, stars: fundamental properties, stars: late type, stars: low mass, planets and satellites: detection, planets and satellites: fundamental properties
• Public URL: https://keele-repository.worktribe.com/output/1043961
• Publisher URL: https://academic.oup.com/mnras/article/537/1/35/7929888?login=true