YSOVAR: Six pre-main-sequence eclipsing binaries in the Orion Nebula Cluster

TL;DR

This paper reports the discovery and characterization of six new pre-main-sequence eclipsing binaries in the Orion Nebula Cluster, significantly increasing the known sample and providing valuable data for testing stellar evolution models.

Contribution

The study identifies six new PMS EBs in the ONC, including the highest mass and longest period systems, and provides detailed system parameters to aid stellar evolution research.

Findings

Six new PMS EBs confirmed in the ONC.

One system has the highest mass among known PMS EBs.

Another system has the longest period among known PMS EBs.

Abstract

Eclipsing binaries (EBs) provide critical laboratories for empirically testing predictions of theoretical models of stellar structure and evolution. Pre-main-sequence (PMS) EBs are particularly valuable, both due to their rarity and the highly dynamic nature of PMS evolution, such that a dense grid of PMS EBs is required to properly calibrate theoretical PMS models. Analyzing multi-epoch, multi-color light curves for 2400 candidateOrion Nebula Cluster (ONC) members from our Warm Spitzer Exploration Science Program YSOVAR, we have identified 12 stars whose light curves show eclipse features. Four of these 12 EBs are previously known. Supplementing our light curves with follow-up optical and near-infrared spectroscopy, we establish two of the candidates as likely field EBs lying behind the ONC. We confirm the remaining six candidate systems, however, as newly identified ONC PMS EBs. These systems increase the number of known PMS EBs by over 50% and include the highest mass (Theta1 Ori E, for which we provide a complete set of well-determined parameters including component masses of 2.807 and 2.797 solar masses) and longest period (ISOY J053505.71-052354.1, P \sim 20 days) PMS EBs currently known. In two cases (Theta1 Ori E and ISOY J053526.88-044730.7), enough photometric and spectroscopic data exist to attempt an orbit solution and derive the system parameters. For the remaining systems, we combine our data with literature information to provide a preliminary characterization sufficient to guide follow-up investigations of these rare, benchmark systems.