Detection of X-ray emission from gravitationally lensed submillimeter sources in the field of Abell 370

We report the detection by Chandra of SMM J02399-0134 and SMM J02399-0136, two distant (z = 1.06 and z = 2.81, respectively) submillimeter sources gra vitationally magnified by the galaxy cluster Abell 370. These are high-sign ificance (>7 sigma) X-ray detections of the high-redshift submillimeter sou rce population. The Xray positions are coincident with the optical position s to within 1 ". The X-ray spectra, while of low signal-to-noise ratio, are quite hard. Absorbed power-law models with fixed photon indices of Gamma = 2.0 imply local absorbing columns greater than 2 x 10(23) cm(-2) and unabs orbed luminosities greater than 10(44) ergs s(-1) in both sources. These re sults imply that nuclear activity is responsible for the bulk of the lumino sity in SMM J02399-0134 and for at least 20% of the luminosity of SMM J0239 9-0136, consistent with previous optical observations. We also place an upp er limit on the X-ray flux of a third submillimeter source, SMM J02400-0134 . Considered together with previously published Chandra upper limits on the X-ray flux from submillimeter sources, our results imply that 20(-16)(+30) % of submillimeter sources exhibit X-ray emission from active galactic nucl ei (with 90% confidence), consistent with expectations of their contributio n to the diffuse X-ray background.