Detection of an Iron Emission Feature from the Lensed Broad Absorption Line QSO H1413+117 at [CLC][ITAL]z[/ITAL][/CLC] = 2.56

We present the X-ray energy spectrum of the lensed BAL QSO H1413+117 (theCloverleaf) at z=2.56 observed with the Chandra X-ray observatory. We detected293 photons in a 40 ks Advanced CCD Imaging Spectrometer (ACIS-S) observation.The X-ray image consists of four lensed image components, thus the photons arefrom the lensed QSO itself. The overall spectrum can be described with apower-law function heavily absorbed by neutral matter at a redshift consistentwith the QSO redshift. This supports the idea that intrinsic absorption issignificant for BAL QSOs. The spectral fit significantly (99% confidence)improves when we include an emission line. The centroid energy and intrinsicwidth (Gaussian \sigma) of the line are 6.21 \pm 0.16 keV and 220^{+270}_{-130} eV (90% errors), respectively, in the QSO rest frame, assumingthe absorbed power-law as the continuum. The equivalent width of the line inthe QSO rest frame is 960 ^{+1400}_{-480} eV. We suggest that the largeequivalent width, the centroid energy, and the line broadness can be explainedby iron K emission arising from X-ray reprocessing in the BAL flow, assuming ithas a conical thin-sheet structure.Comment: 3 figures, Accepted for publication in ApJ Letter