Spectroscopic surveillance of the variable Herbig Ae star AB Aur

Abstract

AB Aur = HD 31293 = BD + 300741 = MWC 93 = HRC 78n is one of the brightest members of a class of pre-main sequence objects introduced by G. Herbig in 1960. The star is characterized by a spectral type of AOVe, L/L⊙ = 70, mv = 7.2 mag, v sini = 140 km/s, and d = 140 pc. Assuming a stellar radius of a main sequence dwarf R/R⊙ = 3.0, one can estimate the rotational period to be on the order of 28 hours if we see the system edge on. Previous work (Praderie et al. (1985) and Finkenzeller (1983)) has focused on high resolution spectroscopy and shown that AB Aur is subject to short term variations. Finkenzeller's observations have indicated that the emission features can disappear completely within a day. Praderie et al. found evidence of a rotational modulation (45 ± 6 hours) of the MgII λ 2795 and FeII UV lines which is interpreted as due to a non-axisymmetric wind interacting with the outer atmosphere.