Properties of Young Stellar Objects from High Resolution Near Infrared Spectroscopy

Abstract

We analyze high resolution (R = 50,000) spectra at 2.2 mum of 10 Class If young stellar objects in the rho Ophiuchi dark cloud. We measure effective temperatures, continuum veiling, and v sin i rotation from the shapes and strengths of atomic photospheric lines by comparing to spectral synthesis models at 2.2 mum. We measure surface gravities in 2 stars from the integrated line flux ratio of the (CO)-C-12 line region at 2.3 mum and the Na I line region at 2.2 mum. Although the majority (8/10) of the Class II stars have similar effective temperatures (3530 K 100 K), they exhibit a large spread in bolometric luminosities (factor similar to8), as derived from near-IR photometry. In the two stars where we have surface gravity measurements from spectroscopy, the photometrically derived luminosities are systematically higher than the spectroscopic luminosities. The spread in the photometrically derived luminosities in our other sources suggests either a large spread in stellar ages, or nonphotospheric emission in the J-band since anomalous and significant veiling at J has been observed in other T Tauri stars. Our spectroscopic luminosities result in older ages on the H-R diagram than is suggested by photometry at J or K. Most of our sources show a larger amount of continuum excess (F-Kex) than stellar flux at 2.2 mum (F-K*), substantially higher in many cases (r(K) equivalent to F-Kex/F-K* = 0.3-4.5). The derived v sin i rotation is substantial, but systematically less than the rotation measured in class 1.5 (flat) and Class I sources from other studies in Ophiuchus.