P. Corporon 1, C. Ceccarelli 2, & A.-M. Lagrange 2
1 Université de Montreal, Departement de Physique, Canada
2 Laboratoire d'Astrophysique de l'Observatoire de Grenoble, France
We report ISO observations of the star TY Corona Australis with LWS and SWS instruments. TY CrA belongs to the class of Herbig Ae/Be stars (HAeBe), intermediate mass pre-Main Sequence objects. It is in fact a spectroscopic triple system, two T Tauri stars orbiting the HAeBe primary. Furthermore, non-periodic photometric variations in visible, caused by dust clumps circulating around TY CrA, are observed.
In order to better study the dusty as well as the gazeous matter
surrounding TY CrA, we have obtained in October 1996 full-scan spectra
covering the 2.4-197 
domain with both ISO spectrographs
LWS and SWS.
Emission bands detected at 3.3, 6.2, 7.7, 8.8, 11.3 and 12.5 mic. are
attributed to small carbon-rich particles, PAH. [O I] 63 and
146
and [C II] 158
emission lines are
clearly present.
A compact H II region and a photo-dissociation region (PDR) may explain
respectively the presence of the PAH and forbidden emissions. A
temperature of 100 K and a density
nH = 105-106 cm-3 have been
estimated for the PDR.
Unlike two others Ae/Be Herbig stars, HD 100546 and HD 142527, TY CrA shows no crystalline silicates in its circumstellar medium ; this may suggest an earlier stage of evolution for the system.