The p-mode spectrum of γ Equ (HR 8097)

We present new high-speed photometric observations of the rapidly oscillating Ap (roAp) star γ Equ acquired on 26 nights during 1992. A frequency analysis of these observations reveals the presence of four p modes with frequencies of 1339, 1366, 1397 and 1427 μHz. These frequencies are all roughly equally spaced by about 30 μHz, which we interpret as the spacing of alternating even and odd ℓ modes for a slightly evolved A-type star. This interpretation leads to an asteroseismological luminosity estimate for γ Equ of MV(Δv) = 1.8, which is in good agreement with the parallax luminosity MV(π) = 1.9.