Ca. Grady et al., Transient infall events in the disk of AB Aurigae: The beta Pictoris phenomenon at 2-4 megayears, ASTROPHYS J, 511(2), 1999, pp. 925-931
Surveys of Herbig Ae/Be stars have indicated that infalling, circumstellar
gas similar to that routinely detected toward beta Pic is preferentially ob
served close to the disk midplane. Recent millimeter interferometry of the
historically prototypical Herbig Ae star, AB Aur, indicates that this star
is viewed slightly above the disk midplane (i = 76 degrees). The wealth of
archival spectroscopic data for this star makes it an ideal test of the geo
metry for infalling or accreting gas in these stars. We present a review of
the extant IUE and Hubble Space Telescope GHRS spectral data for AB Aur an
d find, in contrast to previous studies of this star, which focused on Mg I
I, that infalling gas is detected at all epochs with covering factors simil
ar to those reported for HD 100546 and that an episode of enhanced infall w
as serendipitously detected during the 1990 monitoring run.