Keywords :
accretion, accretion disks - black hole physics - quasars absorption lines - quasars: supermassive black holes - quasars: individual: APM 08279+5255 - X-rays: general
Abstract:We present new joint XMM-Newton and NuSTAR observations of APM 08279+5255, a gravitationally-lensed, broad-absorption line quasar (z=3.91). After showing a fairly stable flux (f_2-10_~=4-5.5x10^-13^erg/s) from 2000 to 2008, APM 08279+5255 was found in a fainter state in the latest X-ray exposures (f_2-10_~=2.7x10^-13^erg/s), which can likely be ascribed to a lower X-ray activity. Moreover, the 2019 data present a prominent Fe K{alpha} emission line and do not show any significant absorption line. This fainter state, coupled to the first hard X-ray sampling of APM 08279+5255, allowed us to measure X-ray reflection and the high-energy cutoff in this source for the first time. From the
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