Three Pre-Main-Sequence Eclipsing Binaries in the Orion Nebula Cluster

There is still much that is not known about the earliest stages of stellar evolution. Pre-main-sequence (PMS) stars are highly dynamic objects, and their internal structures change rapidly as they accrete material and contract towards the main sequence. To ensure that theoretical PMS models are properly calibrated, it is important to test them against a dense grid of PMS objects with well-measured properties. Eclipsing binaries (EBs) are especially useful probes of stellar evolution models because their high inclination and close separation allow for the radii, masses, and effective temperatures of both stars to be constrained via photometric and spectroscopic analysis. Previous work by Morales-Calderón+2012 contributed to PMS model calibration efforts by providing an initial characterization of six PMS EBs in the Orion Nebula Cluster via multi-color Spitzer light curves and single-epoch spectroscopy. We present follow-up multi-epoch Keck/HIRES spectroscopy and derived radial velocities for three of these systems. ISOY J053526.88-044730.7 (Brun 691) is a single-lined system with an orbital period of 3.905625d, which we find may include a low-mass component in the brown dwarf regime. ISOY J053505.71-052354.1 and ISOY J053515.55-052514.1 (V* V1501 Ori) are double-lined systems with unusually long orbital periods, estimated at about 20d and 24d, respectively. We derive constraints on the physical properties of these systems by simultaneously modeling their light curves, radial velocities, and spectral energy distributions. We also discuss implications for theoretical PMS models.