Hubble Space Telescope imaging of the large-redshift gravitational lens candidate 1208+1011

Four-color photometry obtained with the Hubble Space Telescope is consistent with the hypothesis that the light from the quasar 1208+1011 (z = 3.8) is gravitationally lensed. Guided exposures taken with the HST Planetary Camera resolve the quasar image into two point-source components separated by 0″.476 ± 0″.004. The intensity ratio of the components is approximately 4:1 in each of four broad-band HST filters with mean wavelengths of 4352, 5416, 6898, and 8922 Å. The HST photometry, when combined with high-resolution ground-based spectroscopy, rules out the possibility that the secondary component is a Galactic star. The limit on additional point sources is 3% of the brighter image for separations greater than 0″.5 from the primary component and 5% of the brighter component for separations between 0″.1 and 0″.5. If the gravitational lens is an ordinary galaxy, it would not have been detected on the HST images.