AN ISO VIEW ON INTERSTELLAR DUST HEATED BY RED GIANT STARS

In order to study the structure and emission of the diffuse interstell ar medium when it is heated by red giant stars, we have obtained ISOPH OT maps centered at proximity of a sample of such objects. The maps ar e 7'x7' with a pixel size of 45 '', and were made at 60 and 90 mu m. H ere we present the preliminary results of this program, based on data from 11 fields recently achieved by ISO. The maps have been centered a t 4.7' from the star but do not contain it to avoid saturation. In 7 c ases out of 11 we observe an infrared emission with a gradient toward the star. This effect is most probably due to radiative heating of gra ins which closely surround the red giant, and not to foreground or bac kground matter. The emission is structured at the level of the map pix el, i.e. 45 '', which corresponds to typical linear sizes of similar t o 0.1-0.3 pc.