XMM-Newton and Chandra Spectroscopy of the Variable High-Energy Absorption of PG 1115+080: Refined Outflow Constraints

We present results from multi-epoch spectral analysis of XMM-Newton and Chandra observations of the mini-broad absorption line (BAL) quasar PG 1115+080. This is one of the few X-ray-detected mini-BAL quasars to date that is bright enough in the X-ray band, mostly due to large gravitational-lensing magnifications, to allow in-depth spectral analysis. The present XMM-Newton observations of PG 1115+080 have provided the highest signal-to-noise ratio X-ray spectra of a mini-BAL quasar obtained to date. By modeling the spectra of PG 1115+080 we have obtained constraints on the column density and ionization state of its outflowing absorbing gas. A comparison between these constraints over several epochs indicates significant variability in the properties of the outflowing absorbers in PG 1115+080. The depths of the high-energy broad absorption features in PG 1115+080 show a significant decrease between the first two observation epochs separated by a rest-frame timescale of ~1 yr. This variability supports the intrinsic nature of these absorbers. Assuming the interpretation that the high-energy absorption features arise from highly ionized Fe XXV, we constrain the fraction of the total bolometric energy released by quasars PG 1115+080 and APM 08279+5255 into the intergalactic medium in the form of kinetic energy to be ɛ_k=0.64^+0.52_-0.40 (68% confidence) and 0.09^+0.07_-0.05, respectively. According to recent theoretical studies this range of efficiencies is large enough to significantly influence the formation of the host galaxy and to regulate the growth of the central black hole.