2002ApJ...564..405R

We present moderate-resolution optical spectra of the highly variable Herbig Ae star RR Tauri over 12 epochs spanning ∼2.5 mag in V. Combining normalized spectra with contemporaneous photometry from two databases, we analyze both equivalent width and flux behavior as a function of system brightness for lines from the Ca II K line in the blue to the Paschen lines in the far red. The wings (Δv>400 km.s^–1) of the Balmer lines and the equivalent widths of several weak metal lines are essentially constant, indicating very little change in the underlying photosphere over a factor of 10 change in brightness. We detect no measurable change in spectral type. Variability is apparent in the cores of Hα and Hβ, but the total flux in these lines is not correlated with photometric variability. Forbidden oxygen ([O I] λ6300) has essentially constant flux, indicating a stable low-density wind component. The low-ionization permitted lines of Fe II, Ca II, O I, and Na I are seen strongly in absorption for V≤12.2 in these normalized spectra but change dramatically from absorption to emission during deep minima (V≳12.6). Analysis of the Fe II (42) triplet indicates that these lines originate in circumstellar gas that is partially affected by the photometric minima, in that the absorbing gas changes with the stellar continuum (conserving equivalent width), while a weak emitting region is unaffected (roughly constant flux). Our results are consistent with a model in which the stellar minima are caused by an occulting screen of size such that it obscures the stellar surface and the innermost region of circumstellar gas producing permitted metal absorption lines but not the outer parts or the wind. The circumstellar hydrogen, while variable, is not strongly affected by the occultations.