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

Abstract

We present the X-ray energy spectrum of the lensed broad absorption line QSO H1413+117 (the Cloverleaf) at z = 2.56 observed with the Chandra X-ray observatory. We detected 293 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 are from the lensed QSO itself. The overall spectrum can be described with a power-law function heavily absorbed by neutral matter at a redshift consistent with the QSO redshift. This supports the idea that intrinsic absorption is significant for BAL QSOs. The spectral fit significantly (99% confidence) improves when we include an emission line. The centroid energy and intrinsic width (Gaussian σ) of the line are 6.21 ± 0.16 keV and 220 eV (90% errors), respectively, in the QSO rest frame, assuming the absorbed power law as the continuum. The equivalent width of the line in the QSO rest frame is 960 eV. We suggest that the large equivalent width, the centroid energy, and the line broadness can be explained by iron K emission arising from X-ray reprocessing in the BAL flow, assuming it has a conical thin-sheet structure.