SCIENTIFIC AIM
The evolutionary status of several YSO categories of is best known by studying the SED inclination, due to infrared excess. Basically it is found in the literature two different models to explain the circumstellar dust distribution:
1. spherically symmetric (Rowan-Robinson 1980; Ivezic & Elitzur 1997)
2. accretion disc (Lynden-Bell & Pringle 1974; Adams & Shu 1986, Hartmann et al 1998)
In a previous work we developed a simple model assuming that the circumstellar material is distributed in a spherical envelope and wecould reproduce the observed SED of a sample of stars associated to the Cha I and ? Oph clouds, in order to study their Luminosity Function (Gregorio-Hetem et al. 1990).
The best SED's fit could not be obtained for some objects from that sample motivating us to include a disc in the stellar structure. More recently our model was updated by considering a better extinction law and new statistical tests to improve the fit quality.