2006AJ....131..501S

An X-ray image of the L1251 dark cloud in Cepheus was obtained with the XMM-Newton telescope. More than three dozen sources were detected above a 3 σ limit in X-ray luminosity of L_X=10^29.0 ergs/s. Among the detections are eight optically visible T Tauri stars, which had been identified in earlier work from their emission at Hα. The two strongest X-ray sources have steady luminosities of L_X∼10³¹ ergs/s and are at the saturation limit for X-ray activity in late-type stars, L_X/L_bol∼10^–3. X-ray emission was also observed from two CO emission cores in L1251, core C (L1251A) and core E (L1251B). Both regions contain high-velocity molecular gas, bright IRAS sources (Class I protostars), thermal radio sources, and Herbig-Haro (HH) jets. In L1251A strong X-ray emission was discovered in close proximity to the near-infrared and radio source IRS A/VLA 7 and to IRAS 22343+7501. IRS A/VLA 7 thus appears to be the most likely source of the molecular and HH outflows in L1251A. In L1251B X-ray emission was observed from a visible T Tauri star, KP2-44, which is thought to be the driving source for HH 189. Also reported is the tentative detection of X-ray emission from VLA 3, a thermal radio continuum source in L1251B that is closely associated with the extreme Class I protostar IRAS 22376+7455.