paper

Dramatic X-ray Spectral Variability of the Broad Absorption Line Quasar PG2112+059

arXiv:astro-ph/0311401 · doi:10.1086/381494

Abstract

With a 1999 ASCA observation, PG2112+059 became notable as the first Broad Absorption Line (BAL) quasar found to exhibit a typical radio-quiet quasar X-ray continuum underlying a large amount of intrinsic absorption. We present a recent Chandra ACIS-S3 observation of PG2112+059 that demonstrates remarkable spectral and luminosity variability since that time. In addition to a decrease in the continuum normalization by a factor of ~3.5, the absorption column density has apparently increased substantially, and a strong feature in the Fe K alpha region has appeared. Concurrent HST STIS data compared with archival HST data from earlier epochs show evidence for variability of the continuum (up to a factor of ~1.7 in the ultraviolet), and in some absorption features of the CIV 1549 BAL since 1992; however, the OVI BAL structure is consistent with a 1995 observation. We also present evidence for Ly beta--OVI 1037.62 and Ly alpha--NV 1242.80 line-locked absorption systems, supporting the assumption that ultraviolet line pressure is driving the BAL outflow. Whereas ultraviolet BALs typically exhibit only modest equivalent-width variability over timescales of years, the dramatic X-ray variability of PG2112+059 suggests that X-ray spectral variability studies of BAL quasars have great potential for probing the physics of quasar winds.

arXiv comment30 pages, 10 figures, uses AASTeX. Accepted for publication in the Astrophysical Journal

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