The observational signatures of convectively excited gravity modes in main-sequence stars

We predict the flux and surface velocity perturbations produced by convectively excited gravity modes (g-modes) in main-sequence stars. Core convection in massive stars can excite g-modes to sufficient amplitudes to be detectable with high-precision photometry by Kepler and Convection, Rotation and planetary Transits (CoRoT), if the thickness of the convective overshoot region is less than or similar to 30 per cent of a pressure scale height. The g-modes manifest as excess photometric variability, with amplitudes of similar to 10 mu mag at frequencies similar to 10 mu Hz (0.8 d(-1)) near the solar metallicity zero-age main sequence. The flux variations are largest for stars with M greater than or similar to 5M(circle dot), but are potentially detectable down to M similar to 2-3M(circle dot). During the main-sequence evolution, radiative damping decreases such that ever lower frequency modes reach the stellar surface and flux perturbations reach up to similar to 100 mu mag at the terminal-age main sequence. Using the same convective excitation model, we confirm previous predictions that solar g-modes produce surface velocity perturbations of less than or similar to 0.3mm s(-1). This implies that stochastically excited g-modes are more easily detectable in the photometry of massive main-sequence stars than in the Sun.