THE NEW GRAVITATIONAL LENS SYSTEM B1030+074

We report the discovery of a new double-image gravitational lens syste m, B 1030+074, which was found during the Jodrell Bank-VLA Astrometric Survey (JVAS). We have collected extensive radio data on the system u sing the VLA, MERLIN, the EVN and the VLBA, and optical observations u sing WFPC2 on the HST. The lensed images are separated by 1.56 arcsec and their flux density ratio at centimetric wavelengths is approximate ly 14:1, although the ratio is slightly frequency-dependent and the im ages 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 ellipso id which yields a time delay of 156/h(50) d, This lens is likely to be suitable for the measurement of the Hubble constant.