The IGRINS YSO Survey III: Stellar parameters of pre-main sequence stars in Ophiuchus and Upper Scorpius

TL;DR

This study uses high-resolution infrared spectroscopy to determine fundamental stellar parameters for young stars in star-forming regions, revealing evolutionary differences and similarities among various stellar groups.

Contribution

It presents a homogeneous method to derive stellar parameters for pre-main sequence stars using IGRINS spectra, including magnetic fields and veiling, across multiple star-forming regions.

Findings

Class II YSOs have lower surface gravity and rotational velocity than Class III.

Ophiuchus and Taurus stars have similar ages, indicating comparable evolutionary stages.

Upper Scorpius and TWA stars are more evolved and older.

Abstract

We used the Immersion GRating Infrared Spectrometer (IGRINS) to determine fundamental parameters for 61 K- and M-type young stellar objects (YSOs) located in the Ophiuchus and Upper Scorpius star-forming regions. We employed synthetic spectra and a Markov chain Monte Carlo approach to fit specific K-band spectral regions and determine the photospheric temperature ($T_{\rm eff}$), surface gravity ($\log$ g), magnetic field strength (B), projected rotational velocity ($v \sin i$), and K-band veiling ($r_{\rm K}$). We determined B for $\sim$46% of our sample. Stellar parameters were compared to the results from Taurus-Auriga and the TW Hydrae Association (TWA) presented in Paper I of this series. We classified all the YSOs in the IGRINS survey with infrared spectral indices from 2MASS and WISE photometry between 2 and 24~$\mu$m. We found that Class II YSOs typically have lower $\log$ g and $v\sin i$, similar B, and higher K-band veiling than their Class III counterparts. Additionally, we determined the stellar parameters for a sample of K and M field stars also observed with IGRINS. We have identified intrinsic similarities and differences at different evolutionary stages with our homogeneous determination of stellar parameters in the IGRINS YSO Survey. Considering $\log$ g as a proxy for age, we found that the Ophiuchus and Taurus samples have a similar age. We also find that Upper Scorpius and TWA YSOs have similar ages, and are more evolved than Ophiuchus/Taurus YSOs.