Observational studies of the Herbig Ae/Be stars. III - Spectrophotometry

Spectrophotometry from 3400 to 8300 A is presented for 18 of the pre-main-sequence Herbig Ae/Be stars. Two observational features are readily noted in many of these stars: a Balmer discontinuity smaller than that exhibited by main-sequence stars of similar spectral type, and very heavy reddening. The observations are de-reddened through the use of model atmospheres appropriate to the spectral type, and an excess flux in the near-infrared is apparent also. A simple optically thin model is developed which ascribes the small Balmer jump to free-bound emission in the Balmer continuum arising in a circumstellar region; the same model parameters also reproduce the near-infrared excess when free-free and Paschen free-bound emission are invoked. The model produces a volume emission measure for the circumstellar region. Estimates of mass-flow rates are made, and some implications of the model for the infrared excess past 1 micron are discussed.

Перевод пока недоступен