The spectroscopic variability ofTeffand log gin the hot pulsating star β Cephei

Time resolved spectra of β Cep yield the following average results: Teff= 24 000 ± 250 K, log g= 3.91 ± 0.05 and ξ= 8.1 ± 0.9 km s−1. Nitrogen, oxygen, neon, aluminium, silicon and sulfur abundances are solar while carbon, magnesium and iron are slightly underabundant. Pulsational amplitudes of ΔTeff∼ 700 K and Δlog g∼ 0.2 dex are found from Hβ. The metal lines give similar amplitudes but centred on Teff∼ 25 000 K. An upper limit of 1.0 km s−1 to the variability of the microturbulence is derived from the Si iii triplet at 455 nm. The radial-velocity amplitude derived from the core of Hβ is ∼15 per cent greater than that from the metal lines.