A KELT-TESS Eclipsing Binary in a Young Triple System Associated with a "Stellar String" Theia 301

TL;DR

This paper reports the discovery of an eclipsing binary within a young triple system associated with the stellar string Theia 301, providing valuable data on young stellar evolution and system dynamics.

Contribution

It identifies a new young eclipsing binary in a wide system, estimates its age, and links it to the stellar string Theia 301, enhancing understanding of young stellar populations.

Findings

HD 54236A is an eclipsing binary with 2.4-day orbit.

The system's age is estimated at 225 +/- 50 Myr.

HD 54236 is associated with the stellar string Theia 301.

Abstract

HD 54236 is a nearby, wide common-proper-motion visual pair that has been previously identified as likely being very young by virtue of strong X-ray emission and lithium absorption. Here we report the discovery that the brighter member of the wide pair, HD~54236A, is itself an eclipsing binary (EB), comprising two near-equal solar-mass stars on a 2.4 d orbit. It represents a potentially valuable opportunity to expand the number of benchmark-grade EBs at young stellar ages. Using new observations of Ca2H&K emission and lithium absorption in the wide K-dwarf companion, HD 54236B, we obtain a robust age estimate of 225 +/- 50 Myr for the system. This age estimate and Gaia proper motions show HD 54236 is associated with Theia~301, a newly discovered local "stellar string", which itself may be related to the AB Dor moving group through shared stellar members. Applying this age estimate to AB~Dor itself alleviates reported tension between observation and theory that arises for the luminosity of the 90M_Jup star/brown dwarf AB Dor C when younger age estimates are used.