Evidence for Granulation and Oscillations in Procyon from Photometry with the WIRE satellite

Abstract

We report evidence for the granulation signal in the star Procyon A, based on two photometric time series from the star tracker on the WIRE satellite. The power spectra show evidence of excess power around 1 milliHz, consistent with the detection of p-modes reported from radial velocity measurements. We see a significant increase in the noise level below 3 milliHz, which we interpret as the granulation signal. We have made a large set of numerical simulations to constrain the amplitude and timescale of the granulation signal and the amplitude of the oscillations. We find that the timescale for granulation is T(gran) = 750(200) s, the granulation amplitude is 1.8(0.3) times solar, and the amplitude of the p-modes is 8(3) ppm. We found the distribution of peak heights in the observed power spectra to be consistent with that expected from p-mode oscillations. However, the quality of the data is not sufficient to measure the large separation or detect a comb-like structure, as seen in the p-modes of the Sun. Comparison with the recent negative result from the MOST satellite reveal that the MOST data must have an additional noise source that prevented the detection of oscillations.

arXiv comment23 pages, 12 figures, submitted to ApJ; v2 revisions: one reference corrected and a comment in Figure 7 corrected

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• Asteroseismic analysis of the roAp star alpha Circini: 84 days of high-precision photometry from the WIRE satellite
• Eclipsing binaries observed with the WIRE satellite I. Discovery and photometric analysis of the new bright A0IV eclipsing binary Psi Centauri
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• Oscillator Strength Measurements of Atomic Absorption Lines from Stellar Spectra
• Seismology of Procyon A: determination of mode frequencies, amplitudes, lifetimes, and granulation noise
• Amplitude variability in satellite photometry of the non-radially pulsating O9.5V star zeta Oph
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• Astrophysics in 2006
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• Searching for p-modes in MOST Procyon data: Another view
• Oscillations in Procyon A: First results from a multi-site campaign
• Recent MOST space photometry