NGTS clusters survey – III. A low-mass eclipsing binary in the Blanco 1 open cluster spanning the fully convective boundary. Issue 4 (7th September 2021)

• Record Type: Journal Article
• Authors: Smith, Gareth D; Gillen, Edward; Queloz, Didier; Hillenbrand, Lynne A; Acton, Jack S; Alves, Douglas R; Anderson, David R; Bayliss, Daniel; Briegal, Joshua T; Burleigh, Matthew R; Casewell, Sarah L; Delrez, Laetitia; Dransfield, Georgina; Ducrot, Elsa; Gill, Samuel; Gillon, Michaël; Goad, Michael R; Günther, Maximilian N; Henderson, Beth A; Jenkins, James S; Jehin, Emmanuël; Moyano, Maximiliano; Murray, Catriona A; Pedersen, Peter P; Sebastian, Daniel; Thompson, Samantha; Tilbrook, Rosanna H; Triaud, Amaury H M J; Vines, Jose I; Wheatley, Peter J
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 507:Issue 4(2021)
• Page Start: 5991
• Page End: 6011
• Publication Date: 2021-09-07
• Subjects: binaries: eclipsing -- binaries: spectroscopic -- stars: evolution -- stars: fundamental parameters -- stars: low mass -- open clusters and associations: individual: Blanco 1; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab2374
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We present the discovery and characterization of an eclipsing binary identified by the Next Generation Transit Survey in the ∼115-Myr-old Blanco 1 open cluster. NGTS J0002−29 comprises three M dwarfs: a short-period binary and a companion in a wider orbit. This system is the first well-characterized, low-mass eclipsing binary in Blanco 1. With a low mass ratio, a tertiary companion, and binary components that straddle the fully convective boundary, it is an important benchmark system, and one of only two well-characterized, low-mass eclipsing binaries at this age. We simultaneously model light curves from NGTS, TESS, SPECULOOS, and SAAO, radial velocities from VLT/UVES and Keck/HIRES, and the system's spectral energy distribution. We find that the binary components travel on circular orbits around their common centre of mass in P orb = 1.098 005 24 ± 0.000 000 38 d, and have masses M pri = 0.3978 ± 0.0033 M⊙ and M sec = 0.2245 ± 0.0018 M⊙, radii R pri = 0.4037 ± 0.0048 R⊙ and R sec = 0.2759 ± 0.0055 R⊙, and effective temperatures $T_{\rm pri}=\mbox{$3372\, ^{+44}_{-37}$}$ K and $T_{\rm sec}=\mbox{$3231\, ^{+38}_{-31}$}$ K. We compare these properties to the predictions of seven stellar evolution models, which typically imply an inflated primary. The system joins a list of 19 well-characterized, low-mass, sub-Gyr, stellar-mass eclipsing binaries, which constitute some of the strongest observational tests of stellar evolution theory at low masses and young ages.