Visibilities and bolometric corrections for stellar oscillation modes observed by Kepler: (Research note)

Abstract

Context.Kepler produces a large amount of data used for asteroseismological analyses, particularly of solar-like stars and red giants. The mode amplitudes observed in the Kepler spectral band have to be converted into bolometric amplitudes to be compared to models. Aims. We give a simple bolometric correction for the amplitudes of radial modes observed with Kepler, as well as the relative visibilities of non-radial modes. Methods. We numerically compute the bolometric correction cK-bol and mode visibilities for different effective temperatures Teff within the range 4000-7500 K, using a similar approach to a recent one from the literature. Results. We derive a law for the correction to bolometric values: cK - bol = 1 + a 1(Teff - To) + a2(Teff - To)2, with To = 5934 K, a1 = 1.349 × 10-4 K-1, and a2 = -3.120 × 10-9 K-2 or, alternatively, as the power law c K - bol = (Teff/To)α with α = 0.80. We give tabulated values for the mode visibilities based on limb-darkening (LD), computed from ATLAS9 model atmospheres for Teff [4000,7500] K, log g [2.5,4.5], and [M/H] [- 1.0, + 1.0]. We show that using LD profiles already integrated over the spectral band provides quick and good approximations for visibilities. We point out the limits of these classical visibility estimations. © 2011 ESO.