The new gravitational lens system B1030+074

We report the discovery of a new double-image gravitational lens system, B 1030+074, which was found during the Jodrell Bank-VLA Astrometric Survey (JVAS). We have collected extensive radio data on the system using the VLA, MERLIN, the EVN and the VLBA, and optical observations using WFPC2 on the HST. The lensed images are separated by 1.56 arcsec and their flux density ratio at centimetric wavelengths is approximately 14:1, although the ratio is slightly frequency-dependent and the images appear to be time-variable. The HST pictures show both the lensed images and the lensing galaxy close to the weaker image, The lensing galaxy has substructure which could be a spiral arm or an interacting galaxy. We have modelled B1030+074 using a singular isothermal ellipsoid which yields a time delay of 156/h(50) d, This lens is likely to be suitable for the measurement of the Hubble constant.