B Stars in the Milky Way

Fitzpatrick and D. Massa (Emergent IT) successfully proposed a Cycle 4 Observing Program with the Far-Ultraviolet Spectroscopic Explorer (FUSE) satellite, entitled ''Temperature Variations in Slowly Pulsating B Stars'' As a class, these stars are seen to exhibit low-amplitude, multi-periodic photometric variability on time scales of 0.5 - 2.0 days. They also display low-amplitude radial velocity variations (i.e., a few $\times 10$ km/sec). The variability has been shown to result from non-radial g-modes excited by the $\kappa$-mechanism, due to the presence of a relative maximum in the metal opacity below the atmosphere. These stars are prime candidates for astroseismology studies since the g-modes penetrate deeply into the stellar interior. Far-UV spectra (912 - 1180 Å) will be obtained for several candidate stars to determine their level of flux variability in the very temperature-sensitive FUV spectral domain. The most extreme variable will be chosen for detailed monitoring, to determine whether surface temperature variations contribute to the photometric variability. Robust measures of temperature variability throughout a pulsation cycle would provide a strong constraint on theoretical models which seek to explain the pulsation process