ISO-LWS Grating Spectroscopy: The Case of R CrA Star Forming Region

We present the far infrared spectra of the R CrA star forming region obtained with ISO-LWS. We collected a pointed observation on the Herbig Ae star R CrA and a raster scan covering the surrounding region, where HH100 (with its exciting source) and the pre-Main Sequence star T CrA are located. The OI 63 microns and the CII 158 microns lines have been detected in all the pointed positions, with a ratio consistent with PDR excitation. CO rotational lines (between J_up=14 and J_up=19) are detected on R CrA; from their intensities we derived, using a LVG model, the density and temperature of the emitting region. Other molecular transitions (OH and H₂O) have been detected on the investigated objects; the derived cooling of all the molecular species is in agreement with C-shock as the likely excitation mechanism. The continuum emission of R CrA peaks around 100 microns (as expected for a Herbig star) while the other sources (T CrA, HH100) show increasing continua up to ~200 microns, indicating that they are probably less evolved sources.