THE MID INFRARED-SPECTRUM OF THE HYPERLUMINOUS GALAXIES IRAS F15307+3252 AND THE CLOVERLEAF

We report the detections of the hyperluminous galaxy IRAS F15307 +3252 at z = 0.93 and of the Cloverleaf quasar, H 1413+117 at z = 2.56, in the mid infrared using ISOCAM. The spectrum near 10 mu m (observed wav elength) joins smoothly with the data taken from the ground or with th e IRAS satellite. We have detected none of the infrared features attri buted to PAHs. For F15307 +3252, the mid-IR emission (9-16 mu m observ ed wavelength) is 8 x 10(45) erg s(-1) (q(0) = 0.5, H-0 = 75 km s(-1) Mpc(-1)). This represents 10% of the total infrared emission from 5 to 200 mu m (7.5 x 10(46) erg s(-1)). The shape of the mid-IR spectrum c an be fitted by the emission of warm dust grains at a temperature of a bout 400 K. For the Cloverleaf QSO, H 1413+117, the grain temperature is even larger, similar or equal to 1000K. This intense near infrared emission can be used to put a lower limit on the size of the emitting regions of 5.7 pc for F15307 +3252 and 5/root(m) pc for the Cloverleaf where m is the magnification factor.