T. Giannini 1, D. Lorenzetti 2, E. Tommasi 3, B. Nisini 4, M. Benedettini 4, M. Barlow 5, P. Clegg 6, M. Cohen 7, R. Liseau 8, S. Molinari 9, F. Palla 10, S. Pezzuto 4, P. Saraceno 4, H. Smith 11, L. Spinoglio 4, F. Strafella 12, & G.J. White 6
1 Università La Sapienza - Roma, Italy
2 Osservatorio Astronomico di Roma - Monte Porzio, Italy
3 ASI - Roma, Italy
4 Istituto di Fisica dello Spazio Interplanetario CNR - Roma, Italy
5 University College - London, UK
6 Queen Mary 
Westfield College - London, UK
7 Radio Astronomy Laboratory - Berkeley, USA
8 Stockholm Observatory - Salsjobaden, Sweden
9 IPAC - Berkeley, USA
10 Osservatorio Astrofisico di Arcetri - Firenze, Italy
11 Harvard Smithsonian Centre for Astrophysics - Cambridge, USA
12 Dipartimento di Fisica Università di Lecce - Lecce, Italy
We present the first ISO-LWS observations of the molecular emission in three
Herbig AeBe
stars, namely IRAS12496-7650, RCrA and LkH
234. On the three
sources high-J pure rotational CO lines (from Jup 19 to Jup 14) have
been
observed. In addition, on RCrA and LkH234 OH emission has been detected
(71,79
and 84 
m lines).
The CO emission is likely originated by non dissociative C-type shocks, as
expected in
the circumstellar enviroments of sources driving molecular outflows. However,
current
C-shocks models predict water vapour to be the main coolant of the gas; this
circumstance
seems to be not confirmed by our observations, since we do not detect any water
vapour line.
In this communication we derive, using an LVG model, the physical parameters of the emitting regions and discuss the possible alternatives that could explain the observed data.