A Low-Mass Pre-Main-Sequence Eclipsing Binary in Lower Centaurus Crux Discovered with TESS

Abstract

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$\pm$2.2 Myr. The broadband spectral energy distribution (SED) shows clear excess at ~10 um indicative of a circumbinary disk, and new speckle-imaging observations reveal a faint, tertiary companion separated by ~100 AU. H-alpha emission is modulated on the orbital period, consistent with theoretical models of orbitally pulsed accretion streams reaching from the inner disk edge to the central stars. From a joint analysis of spectroscopically determined radial velocities and TESS light curves, together with additional tight constraints provided by the SED and the Gaia parallax, we measure masses for the eclipsing stars of 0.74 Msun and 0.67 Msun; radii of 0.98 Rsun and 0.94 Rsun; and effective temperatures of 3750 K and 3645 K. The masses and radii of both stars are measured to an accuracy of ~1%. The measured radii are inflated, and the temperatures suppressed, relative to predictions of standard PMS evolutionary models at the age of LCC; also, the Li abundances are ~2 dex less depleted than predicted by those models. However, models that account for the global and internal effects of surface magnetic fields are able to simultaneously reproduce the measured radii, temperatures, and Li abundances at an age of 17.0$\pm$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.

23 pages, 19 figures, accepted by ApJ

References in corpus (36)

• The Transiting Exoplanet Survey Satellite
• The Dartmouth Stellar Evolution Database
• New evolutionary models for pre-main sequence and main sequence low-mass stars down to the hydrogen-burning limit
• Gaia Early Data Release 3: Parallax bias versus magnitude, colour, and position
• A million binaries from Gaia eDR3: sample selection and validation of Gaia parallax uncertainties
• Tertiary companions to close spectroscopic binaries
• Evolution of low-mass star and brown dwarf eclipsing binaries
• Parallax Systematics and Photocenter Motions of Benchmark Eclipsing Binaries in Gaia EDR3
• Eclipsing Binary Stars as Benchmarks for Trigonometric Parallaxes in the Gaia Era
• Older and Colder: The impact of starspots on pre-main sequence stellar evolution
• A Surprising Reversal of Temperatures in the Brown-Dwarf Eclipsing Binary 2MASS J05352184-0546085
• Empirical Tests of Pre-Main-Sequence Stellar Evolution Models with Eclipsing Binaries
• Untangling the Galaxy. II. Structure within 3 kpc
• Age Determination in Upper Scorpius with Eclipsing Binaries
• CSI 2264: Characterizing Young Stars in NGC 2264 with Short-Duration, Periodic Flux Dips in their Light Curves
• Rotation, inflation, and lithium in the Pleiades
• Periodic accretion from a circumbinary disk in the young binary UZ Tau E
• Empirical Bolometric Correction Coefficients for Nearby Main-Sequence Stars in Gaia Era
• Cluster Difference Imaging Photometric Survey. I. Light Curves of Stars in Open Clusters from TESS Sectors 6 & 7
• Orbiting Clouds of Material at the Keplerian Co-Rotation Radius of Rapidly Rotating Low Mass WTTs in Upper Sco
• A Measurement of Radius Inflation in the Pleiades and its Relation to Rotation and Lithium Depletion
• Self-consistent evolution of accreting low-mass stars and brown dwarfs
• Surprising dissimilarities in a newly formed pair of 'identical twin' stars
• Microarcsecond Astrometry: Science Highlights from Gaia
• Accretion and Magnetic Reconnection in the Classical T Tauri Binary DQ Tau
• The Elusive Majority of Young Moving Groups. I. Young Binaries and Lithium-Rich Stars in the Solar Neighborhood
• Measuring the Density Structure of an Accretion Hot Spot
• Untangling the Galaxy III: Photometric Search for Pre-main Sequence Stars with Deep Learning
• Pulsed Accretion in the T Tauri Binary TWA 3A
• Fundamental effective temperature measurements for eclipsing binary stars I. Development of the method and application to AI Phoenicis
• The effect of accretion on the pre-main-sequence evolution of low-mass stars and brown dwarfs
• The Inner Disk and Accretion Flow of the Close Binary DQ Tau
• Assessing Spectroscopic-Binary Multiplicity Properties Using Robo-AO Imaging
• Even More Rapidly Rotating Pre-Main Sequence M Dwarfs with Highly Structured Light Curves: An Initial Survey in the Lower Centaurus-Crux and Upper Centaurus-Lupus Associations
• THOR 42: A touchstone $\sim$24 Myr-old eclipsing binary spanning the fully-convective boundary
• Accretion Kinematics in the T Tauri Binary TWA 3A: Evidence for Preferential Accretion onto the TWA 3A Primary

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