An Association in the Aquila Star‐forming Region: High‐Resolution Infrared Spectroscopy of T Tauri Stars

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We present the properties of a group of young stars associated with the well-studied T Tauri star system AS 353, located in the Aquila star-forming region. The association is identified using radial velocity measurements of sample objects selected from the Herbig and Bell Catalog based on their spatial proximity to AS 353. Radial velocities of nine objects were measured from multiepoch high-resolution (R ~ 30,000) H-band spectra obtained with NIRSPEC on Keck II. High-resolution K-band spectra were also obtained for most of the sample objects. Spectral types and rotational velocities are determined for all objects in the sample. The multiepoch H-band spectra were examined for radial velocity variations to detect possible spectroscopic binaries. Eight of the nine objects have radial velocities that are consistent within the 1 σ scatter of the sample. From their mean of -8 km s-1, these eight objects have a standard deviation of 2 km s-1, which suggests that the sample stars are related. The ninth object shows significant radial velocity variations between epochs, characteristic of a spectroscopic binary. The overall multiplicity of the sample is high; we observed 13 stars in seven systems, identifying three new candidate binary components in this project. Many of the spectra reveal hydrogen emission lines typical of strong accretion processes, indicating that most of these objects harbor circumstellar disks and are less than a few million years old. Based on previous estimates, we adopt a distance of 200 ± 30 pc to the young stars in Aquila in order to calculate luminosities and place the stars on an H-R diagram. We discuss possible interpretations of the enigmatic pure emission line spectrum of HBC 684. This work represents the highest spectral resolution infrared observations to date of these intriguing, nearby young stars.