The gravitational lens J1131-1231 - How to avoid missing an opportunity

So far the lens J1131-1231 has been studied only at optical and X-ray wavelengths. A detection in the radio was almost missed as a result of an incorrect position and archive problems. A direct analysis of NVSS uv data - in contrast to the catalogue or images alone - provided sufficient evidence of a detection to justify further radio investigations. The system was subsequently observed with MERLIN and the EVN in e-VLBI mode. Even though MERLIN seems to show the lensed star-forming regions and the compact cores, a preliminary analysis of the EVN data only shows an AGN in the lens itself but not the lensed cores. Additional VLA observations will be carried out soon.