2004AJ....127.2969G

We report centimeter continuum observations with the Very Large Array (VLA) and the Very Long Baseline Array (VLBA), as well as mid-infrared observations with the Cooled Mid-Infrared Camera and Spectrometer on the Subaru Telescope toward the components of the YLW 15 very young binary system, VLA 1 and VLA 2. The centimeter emission of the two components traces partially thick free-free emission, likely due to collimated, ionized winds. VLA 1 is an embedded protostar, undetected in the near-IR, and possibly in the Class 0 to Class I transition and powering a Herbig-Haro outflow. Its mid-IR emission appears slightly resolved with a diameter of ∼16 AU, possibly tracing circumstellar material from both the envelope and the disk. VLA 2 is a typical Class I object, unresolved in the mid-IR, and is responsible for the strong X-ray emission associated with YLW 15. The expected centimeter ``peristellar'' emission associated with the X-ray emission is not detected with the VLBA at 6 cm, likely because of the high optical depth of the free-free emission. Strikingly, the near- to mid-IR properties of YLW 15 suggest that VLA 1 is a more embedded young stellar object (YSO), or alternatively, less luminous than VLA 2, whereas orbital proper motions of this binary system indicate that VLA 1 is more massive than VLA 2. This result is apparently against the expected evolutionary scenario, in which one expects that the more massive YSO in a binary system is the more evolved and luminous YSO. Finally, the nearby source YLW 16A is detected with the VLA; its position coincides with reported near-IR and X-ray sources.