Mon-735: a new low-mass pre-main-sequence eclipsing binary in NGC 2264

• Published in: Monthly notices of the Royal Astronomical Society Vol. 495; no. 2; pp. 1531 - 1548
• Main Authors: Gillen, Edward, Hillenbrand, Lynne A, Stauffer, John, Aigrain, Suzanne, Rebull, Luisa, Cody, Ann Marie
• Format: Journal Article
• Language: English
• Published: Oxford University Press 01.06.2020
• Subjects: binaries: eclipsing; stars: fundamental parameters; binaries: spectroscopic; stars: low-mass; stars: pre-main-sequence; open clusters and associations: individual: NGC 2264
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/staa1016

ABSTRACT We present Mon-735, a detached double-lined eclipsing binary (EB) member of the ∼3 Myr old NGC 2264 star-forming region, detected by Spitzer. We simultaneously model the Spitzer light curves, follow-up Keck/HIRES radial velocities, and the system’s spectral energy distribution to determine self-consistent masses, radii, and effective temperatures for both stars. We find that Mon-735 comprises two pre-main-sequence M dwarfs with component masses of M = 0.2918 ± 0.0099 and 0.2661 ± 0.0095 M⊙, radii of R = 0.762 ± 0.022 and 0.748 ± 0.023 R⊙, and effective temperatures of Teff = 3260 ± 73 and 3213 ± 73 K. The two stars travel on circular orbits around their common centre of mass in P = 1.9751388 ± 0.0000050 d. We compare our results for Mon-735, along with another EB in NGC 2264 (CoRoT 223992193), to the predictions of five stellar evolution models. These suggest that the lower mass EB system Mon-735 is older than CoRoT 223992193 in the mass–radius diagram (MRD) and, to a lesser extent, in the Hertzsprung–Russell diagram (HRD). The MRD ages of Mon-735 and CoRoT 223992193 are ∼7–9 and 4–6 Myr, respectively, with the two components in each EB system possessing consistent ages.