Stellar and Circumstellar Properties of Class I Protostars

TL;DR

This study uses low-resolution near-infrared spectroscopy to analyze the stellar and circumstellar properties of Class I protostars, revealing insights into their extinction, binarity, and evolutionary status.

Contribution

It provides a detailed analysis of Class I protostars using low-resolution spectroscopy, highlighting the importance of multi-method extinction measurements and challenging previous assumptions about obscuration.

Findings

Extinction does not dominate over K-band excess in obscuration.

Some properties differ from published values, prompting re-evaluation.

Estimated ages of <2 Myr suggest these protostars are very young.

Abstract

We present a study of the stellar and circumstellar properties of Class I sources using low-resolution (R~1000) near-infrared K- and L-band spectroscopy. We measure prominent spectral lines and features in 8 objects and use fits to standard star spectra to determine spectral types, visual extinctions, K-band excesses, and water ice optical depths. Four of the seven systems studied are close binary pairs; only one of these systems, Haro 6-10, was angularly resolvab le. For certain stars some properties found in our analysis differ substantially from published values; we analyze the origin of these differences. We determine extinction to each source using three different methods and compare and discuss the resulting values. One hypothesis that we were testing, that extinction dominates over the K-band excess in obscuration of the stellar photospheric absorption lines, appears not to be true. Accretion luminosities and mass accretion rates calculated for our targets are highly uncertain, in part the result of our inexact knowledge of extinction. For the six targets we were able to place on an H-R diagram, our age estimates, <2 Myr, are somewhat younger than those from comparable studies. Our results underscore the value of low-resolution spectroscopy in the study of protostars and their environments; however, the optimal approach to the study of Class I sources likely involves a combination of high- and low-resolution near-infrared, mid-infrared, and millimeter wavelength observations. Accurate and precise measurements of extinction in Class I protostars will be key to improving our understanding of these objects.