Chandra and XMM-Newton Results on the Hubble Constant from Gravitational Lensing

Abstract

We report the first detection of time-delayed flares in single X-ray observations of the gravitationally lensed quasar PG 1115+080 performed with the Chandra and XMM observatories. By combining our observed short time-delay between images A1 and A2 of PG 1115+080 of Δt_A1A2 = 0.149 ±0.006 days with recent constraints on the mass fraction and slope of the dark matter component of the lensing galaxy (Treu & Koopmans 2002) we are able to narrow the allowable set of lens models for PG 1115+080 and thus obtain a tighter limit on the Hubble constant via the lensing method of H₀ = 67_-8⁺¹³ ±3 km s^-1 Mpc^-1 (random + systematic errors).