1998A&A...335..287L

In order to study the structure and emission of the diffuse interstellar medium when it is heated by red giant stars, we have obtained ISOPHOT maps centered at proximity of a sample of such objects. The maps are 7'x7' with a pixel size of 45'', and were made at 60 and 90µm. Here we present the preliminary results of this program, based on data from 11 fields recently achieved by ISO. The maps have been centered at 4.7' from the star but do not contain it to avoid saturation. In 7 cases out of 11 we observe an infrared emission with a gradient toward the star. This effect is most probably due to radiative heating of grains which closely surround the red giant, and not to foreground or background matter. The emission is structured at the level of the map pixel, i.e. 45'', which corresponds to typical linear sizes of ∼0.1-0.3pc.