2021ApJ...919...22M

We present new observations of the odd z = 0.96 weak-line quasar PG1407+265, and report the discovery of CXOU J140927.9+261813, a z = 0.68 X-ray cluster. Archival X-ray photometry spanning nearly four decades reveals that PG1407+265 is variable at the 1 dex level on a timescale of years. V-band variability is observed with an amplitude less than 0.1 mag. The emission-line properties of PG1407+265 also reveal clear evidence for a powerful inflow or outflow due to near- or super-Eddington accretion, having a mechanical luminosity of order 10⁴⁸ erg s^–1. Our follow-up Chandra exposure centered on this object reveals a foreground z = 0.68 cluster roughly 1' x 1.'5 in extent, offset to the east of PG1407+265, roughly coincident with the z = 0.68 radio galaxy FIRST J140927.8+261818. This non-cool-core cluster contributes about 10% of the X-ray flux of PG1407+265, has a mass of (0.6-5.5) x 10¹⁴ M_☉, and an X-ray gas temperature of 2.2-4.3 keV. Because the projected position of the quasar lies at about twice that of the cluster's inferred Einstein radius, lensing by the cluster is unlikely to explain the quasar's unusual properties. We also discuss the evidence for a second cluster centered on and at the redshift of the quasar.