TIC 43152097. The first eclipsing binary in NGC 2232

TL;DR

This paper reports the discovery and detailed analysis of the first eclipsing binary in the young open cluster NGC 2232, providing precise stellar parameters and insights into stellar evolution models for pre-main-sequence stars.

Contribution

It presents the first detailed characterization of an eclipsing binary in NGC 2232, including measurements of stellar parameters and testing of advanced stellar models.

Findings

Secondary star shows radius inflation of 7-11% over standard models.

Magnetic activity and starspots significantly affect stellar structure.

The system confirms the presence of pre-main-sequence stars in NGC 2232.

Abstract

We report the discovery of a low-mass totally eclipsing system in the young (age$\simeq$28 Myr) open cluster NGC2232, during a scrutiny of their TESS light curves. The follow-up study of this detached system, TIC 43152097, is based on photometry and high-resolution spectra from the literature and purposely collected. The radial velocity of the center of mass, as well as the photospheric lithium abundance of the binary components, confirm its membership to NGC2232. By analyzing the existing photometric and spectroscopic data, we obtain orbital elements and fundamental stellar parameters for the two stars. The primary component of TIC 43152097 is a late F-type dwarf (Teff = 6070 K), while the lower-mass secondary results to be a late K-type star (Teff = 4130 K) that is still in the pre-main-sequence phase. The precise measurements of radii, masses, and effective temperatures, enabled by the simultaneous solution of light and radial velocity curves, indicate radius inflation for the K-type component, which turns out to be 7-11 % larger than predicted by standard evolutionary models. More sophisticated models incorporating both inhibition of convective energy transport caused by sub-photospheric magnetic fields and the effects by cool starspots covering a substantial fraction of the stellar surface (30-60 %) allow reproducing the position of the secondary component in the Hertzsprung-Russell and Mass-Radius diagrams.