Stellar Envelopes as Sources of Broad Line Region Emission: New   Possibilities Allowed
  In Active Galactic Nuclei (AGNs) the presence of a star cluster around the central black hole can have several effects on the dynamics and the emission of the global system. In this paper we analyze the interaction of stellar atmospheres with a wind outflowing from the central region of the AGN nucleus. Even a small mass loss from stars, as well as possible star collisions, can give a non-negligible contribution in feeding matter into the AGN nuclear wind. Moreover, stellar mass loss can produce envelopes surrounding stars that turn out to be suitable for reproducing the observed emission from the Broad Line Region (BLR). In this framework, the envelope can be confined by the bow shock arising from the interaction between the expanding stellar atmosphere and the AGN nuclear wind. 
Guidetta Torricelli-Ciamponi (1), Paola Pietrini (2) ((1) Osservatorio   Astrofisico di Arcetri, (2) Universita' di Firenze)