Stellar p-mode oscillations signal in Procyon a from MOST data

Abstract

Recently, Matthews et al. (2004, Nature, 430, 51) claim a null detection of p-mode oscillations in Procyon A from 32 days of nearly continuous photometric satellite-based observations (MOST). They did not even find evidence in the Fourier amplitude spectrum of Procyon of the uniform frequency spacing signature that solar-like stars acoustic spectrum must show according to asymptotic theory. However, re-analysing his data, we have found a clear evidence of signal fully compatible with what is expected from p-mode oscillations in Procyon A. Using the method developed in Régulo & Roca Cortés (2002, A&A, 396, 745), that allows the analysis of stellar oscillations in the acoustic power spectrum of solar-like stars when the signal is buried in noise, we have found a frequency spacing in the power spectrum of the data of 54.5 μHz, that agrees well with the expectations of the theory of stellar oscillation as well as with previous estimations from ground-based observations. Moreover, our method allows the recovery of the power spectrum of the signal from the knowledge of the frequency spacing present in the data, which yields clear peaks that can be identified as acoustic p-modes. Nonetheless, as the frequency spacing coincides with the second sub-multiple of the orbital frequency of the satellite (164.34 μHz) the above findings must be taken with caution. © ESO 2005.