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A Low-mass Pre-main-sequence Eclipsing Binary in Lower Centaurus Crux Discovered with TESS

Stassun, Keivan G. and Torres, Guillermo and Kounkel, Marina and Feliz, Dax L. and Bouma, Luke G. and Howell, Steve B. and Gnilka, Crystal L. and Furlan, E. (2022) A Low-mass Pre-main-sequence Eclipsing Binary in Lower Centaurus Crux Discovered with TESS. Astrophysical Journal, 941 (2). Art. No. 125. ISSN 0004-637X. doi:10.3847/1538-4357/aca32e.

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We report the discovery of 2M1222−57 as a low-mass, pre-main-sequence (PMS) eclipsing binary (EB) in the Lower Centaurus Crux (LCC) association for which, using Gaia parallaxes and proper motions with a neural net age estimator, we determine an age of 16.2 ± 2.2 Myr. The broadband spectral energy distribution (SED) shows clear excess at ≳10 μm indicative of a circumbinary disk, and new speckle imaging observations reveal a faint, tertiary companion separated by ∼100 au. Hα emission is modulated on the orbital period, consistent with theoretical models of orbitally pulsed accretion streams reaching from the inner disk edge to the central stars. From a joint analysis of spectroscopically determined radial velocities and TESS light curves, together with additional tight constraints provided by the SED and the Gaia parallax, we measure masses for the eclipsing stars of 0.74 M_⊙ and 0.67 M_⊙; radii of 0.98 R_⊙ and 0.94 R_⊙; and effective temperatures of 3750 K and 3645 K. The masses and radii of both stars are measured to an accuracy of ∼1%. The measured radii are inflated, and the temperatures suppressed, relative to predictions of standard PMS evolutionary models at the age of LCC; also, the Li abundances are ∼2 dex less depleted than predicted by those models. However, models that account for the global and internal effects of surface magnetic fields are able to simultaneously reproduce the measured radii, temperatures, and Li abundances at an age of 17.0 ± 0.5 Myr. Altogether, the 2M1222−57 system presents very strong evidence that magnetic activity in young stars alters both their global properties and the physics of their interiors.

Item Type:Article
Related URLs:
URLURL TypeDescription
Stassun, Keivan G.0000-0002-3481-9052
Torres, Guillermo0000-0002-5286-0251
Kounkel, Marina0000-0002-5365-1267
Feliz, Dax L.0000-0002-2457-7889
Bouma, Luke G.0000-0002-0514-5538
Howell, Steve B.0000-0002-2532-2853
Gnilka, Crystal L.0000-0003-2519-6161
Furlan, E.0000-0001-9800-6248
Additional Information:K.G.S. acknowledges support from NASA ADAP grant 80NSSC20K0447. CHIRON observations were conducted at CTIO through time allocated by NSF's OIR Lab (NOIRLab Proposal ID 2020A-0146; PI: Bouma). Other observations used the High-Resolution Imaging instrument Zorro, under Gemini LLP Proposal No. GN/S-2021A-LP-105. Zorro was funded by the NASA Exoplanet Exploration Program and built at the NASA Ames Research Center by S.B. Howell, N. Scott, E.P. Horch, and E. Quigley. The international Gemini Observatory is a program of NSF's OIR Lab, managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF on behalf of the Gemini partnership: NSF (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). All of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute. The specific observations analyzed can be accessed via 10.17909/t9-nmc8-f686, 10.17909/3y7c-wa45, and 10.17909/fwdt-2x66.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Gemini PartnershipUNSPECIFIED
Issue or Number:2
Record Number:CaltechAUTHORS:20230105-911538600.2
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:118739
Deposited By: Research Services Depository
Deposited On:08 Feb 2023 02:24
Last Modified:08 Feb 2023 02:24

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