HST CONFIRMATION OF THE LENSED QUASAR J03.13

In order to definitely prove the claim by Claeskens et al. (1996) that J03.13 is a doubly imaged quasar, WFPC2 direct imaging and FOS spectr oscopy of this compact system have been obtained with HST These textbo ok case observations clearly show that J03.13 consists of two point-li ke images separated by 0.849 '' +/- 0.001 '' with a magnitude differen ce of 2.14 +/- 0.03 in V and I. We see no trace of a lensing galaxy. F rom the FOS observations, we find that J03.13 A and B have identical s pectra within the measurement uncertainties. The data also show that s pectroscopic contamination of B by A is negligi ble. We do confirm the redshift z = 2.545 for J03.13 A and B (emission-lines due to Ly-beta lambda 1025 and OVI lambda lambda 1031, 1037 are also detected), first derived from an unresolved ground-based spectrum of the two component s by Claeskens et al. We also find that the absorption line system at z = 2.344 (CIV and Ly-alpha) is present in the spectra of A and B. On the contrary, the absorption line system at z = 1.085 (MgII) is only p resent in the spectrum of J03.13 A. If this latter system is associate d with the lens, we may expect that image A consists of two radially m erging images with a very small angular separation. From the WFPC2 ima gery, we can rule out the presence of a third component fainter than A by up to 5.2 mag. with an angular separation greater than or equal to 0.13 ''.