Chromospheres of T Tauri-type stars.

Summary. The observed total fluxes of H cc emission for some 20 T Tauri stars in the Taurus-Auriga cloud are used to test the hypothesis that the observed emission features can be produced by a chromosphere without recourse to an extended envelope. Under the assumption that the Balmer continuum emission is produced in the chromosphere and that H cc is photoionization dominated, we obtain total emission fluxes that are in good agreement with the observed values. However the predicted profiles have a necessary central reversal which is not always present in the observed ones. It is suggested that the agreement can be improved by the introduction of a velocity gradient as required by our present ideas on the existence of chromospheres. This point will be investigated in detail in a later paper Key words: T Tauri stars - chromosphere - H cc emission line