X-Ray and Infrared Observations of Embedded Young Stars in L1630

Abstract

The HH 24-26 star-forming region within the L1630 dark cloud in Orion contains a remarkable collection of rare Class 0 and Class I protostars, collimated molecular and ionized jets, and a luminous but spatially unresolved ASCA X-ray source. To study the X-ray properties of the embedded protostar population of that region, we have obtained a deep X-ray image with the ACIS-S camera on board the Chandra X-Ray Observatory. A number of H-alpha emission-line objects were detected in the areas surrounding HH 24-26, of which the weak-line T Tauri star SSV 61 was the brightest source, at a steady luminosity of 10^31.9 erg/s (0.3-10 keV). Two Class I protostars aligned with optical jets in HH 24, SSV 63E and SSV 63W, were also detected, as was the continuum radio source SSV 63NE, which is very likely an extreme Class I or Class 0 object. We observed no X rays from the Class 0 protostars HH 24-MMS and HH 25-MMS, nor any from regions of the cloud bounded by HH 25 and HH 26, at a 2-sigma upper limit of 10^30.0 erg/s. HH 26-IR, the Class I object thought to be the origin of the HH 26 flow, was not detected. Near-infrared spectroscopy obtained at the NASA IRTF reveals 3 micron ice bands in the spectra of SSV 59, 63E, 63W, and HH 26-IR, and 2.3 micron CO overtone absorption bands for SSV 61. SSV 60, which lies astride one end of the great arc of nebulosity forming HH 25, exhibits a deep infrared ice band and CO absorption, but is not an X-ray source, and is most likely a distant background giant of late spectral type.