X-Ray Scattering Echoes and Ghost Halos from the Intergalactic Medium: Relation to the Nature of AGN Variability

The Astrophysical Journal May 2015. Volume 805, Issue 1, article id. 23, 9 pp..

Accretion, accretion disks; dust, extinction; quasars: general; intergalactic medium; X-rays: ISM