Iron Emission Lines in the Spectra of Herbig Ae/Be Stars \\Viewed Through Their Proto-Planetary Disks
Session 41 -- Circumstellar Disks
Display presentation, Thursday, January 13, 9:30-6:45, Salons I/II Room (Crystal Gateway)

## [41.09] Iron Emission Lines in the Spectra of Herbig Ae/Be Stars \\Viewed Through Their Proto-Planetary Disks

C.A. Grady (ARC), M.R. P\'erez (IUE Observatory/CSC, ARC), A. Talavera (ESA IUE Observatory), P.S. Th\'e, D. de Winter (Univ. Amsterdam), V.P. Grinin (Crimean Astrophysical Observatory), N. Calvet (CIDA)

Recent studies of Herbig Ae/Be stars suggest that the systems with large amplitude photometric variability coupled with polarimetric variations are PMS stars viewed through their circumstellar disks, with essentially the same orientation as for the $\beta$ Pic system. Irregular, Algol-type photometric minima have been interpreted in terms of intermitted obscuration of the star by dense, circumstellar dust clouds acting as \char'134 natural" coronagraphs. UV observations, made when the star is heavily obscured provide an unparalleled opportunity to probe the immediate vicinity of a number of systems which are too faint for conventional coronagraphic studies with current or planned instrumentation. We present the results of an on-going UV survey of these systems. The available data suggest that prominent Fe II and Mg II emission, visible at the 9 \AA ~resolution of the IUE low dispersion mode, is routinely detectable in Herbig Ae/Be stars when heavily obscured by the dust in the disk, and not when the systems are less heavily obscured. The emission line fluxes do not show any trend with stellar spectral type, but instead appear to correlate with infrared excess, suggesting a relation similar to that seen in CTTS. The available data, while preliminary, suggest that the emission line regions are accretion powered. The relation between the emission line detections, the presence of a FUV flux excess associated with the optical \char'134 blueing effect" at minimum light, and the available data on maximum observed accretion velocity will be discussed.