PMN J1838-3427: A new gravitationally lensed quasar

We report the discovery of a new double-image quasar that was found during a search for gravitational lenses in the southern sky. Radio source PMN J18 38-3427 is composed of two flat-spectrum components with separation 1."0, f lux density ratio 14:1, and matching spectral indices in VLA and VLBA image s. Ground-based BRI images show the optical counterpart (total I = 18.6) is also double, with the same separation and position angle as the radio comp onents. An HST/WFPC2 image reveals the lens galaxy. The optical flux ratio (27: 1) is higher than the radio value, probably because of differential ex tinction of the components by the lens galaxy. An optical spectrum of the b right component contains quasar emission lines at z = 2.78 and several abso rption features, including prominent Ly alpha absorption. The lens galaxy r edshift could not be measured, but it is estimated to be z = 0.36 +/- 0.08. The image configuration is consistent with the simplest plausible models f or the lens potential. The flat radio spectrum and observed variability of PMN J1838-3427 suggest that the time delay between flux variations of the c omponents is measurable and could thus provide an independent measurement o f H-o.