  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 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 year.
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+5225 into the IGM in the form of
kinetic energy to be epsilon_k = 0.64(-0.40,+0.52) (68% confidence), and
epsilon_k =0.09(-0.05,+0.07), respectively. According to recent theoretical
studies this range of efficiencies is large enough to influence significantly
the formation of the host galaxy and to regulate the growth of the central
black hole.
