Detectability of the solar cycle in the average travel times in a case of Sun-as-a-Kepler-star observations. (A, C, E) Simulated travel times for distant solar analogs obtained by adding photon noise to the VIRGO observations. The apparent Kepler magnitude m_K is indicated on each panel. (B, D, F) Photometric variability (rms) from the same simulated time series. (G–I) Cycle parameters extracted from fits to the travel times (orange curves in panels A, C, E), . The means and the error bars are estimated from 20 independent realizations. The green curve shows the standard deviation of the cycle amplitude a, denoted by σ_a. (J) S/N for the activity cycle amplitude, a/σ_a, versus Kepler magnitude.