Previous
abstract 
Next
abstract
The periodic line profile variations in the photospheric lines of Be stars could result from spots on a rotating star or photospheric nonradial pulsations (NRP). Here I present spectroscopic results on ten Be stars ($o$~And, $\lambda$~Eri, $\omega$~Ori, 28~Cyg, $\eta$~Cen, 48~Lib, $\zeta$~Tau, $\psi$~Per, 2~Vul, and KY~And) targeted in recent multiwavelength observing campaigns designed to test these competing models.
The profiles of H$\beta$ and He~I $\lambda 4921$ were analyzed using the time series methods described by Gies \& Kullavanijaya (1988, ApJ, 326, 813) to determine the periodic signals and the number of cycles of variation across the profile. Periodic signals were detected in seven of these stars, and six of these display variability consistent with an $l=-m=2$ NRP mode with periods on the order of a day. The remaining star, $o$~And, shows variability consistent with $m=0$. The same periods are found in simultaneous FUV and optical photometry, and there is a general correlation between the strength of the profile variations and the photometric amplitude. The signal power distribution across the profile is generally flat or peaked in the line wings in accordance with the expectation that horizontal motions will dominate over vertical motions for $g$-mode pulsations; the power distribution is inconsistent with the spot model. The NRP periods are also found in variations of the C~IV $\lambda 1550$ P~Cygni line which indicates that the wind properties are modulated by the photospheric temperature variations associated with NRP.
There is no evidence of higher order modes, but non-periodic narrow features are observed that cross the profiles on time scales similar to the NRP variations. Since these features also appear narrow in the Stark-broadened H$\beta$ line, they probably have a circumstellar origin.
This work was supported by the National Science Foundation grant AST-9115121.
