Limits to CCD ensemble photometry precision, and prospects for asteroseismology

Abstract

We report results of CCD ensemble, time-resolved photometry with the KPNO 2.1-m telescope yielding precision of 400 umag per minute of integration. Previous experience on 1-m class telescopes and well-known scaling laws for the limiting noise sources indicate that current 4-m class telescopes and existing detectors, operated as a network for about five days, would allow detection of coherent (solar-like) oscillations at an amplitude of 15 umag. We provide detailed stellar-evolution modeling and eigenfrequency-analysis results for the stars of the old open cluster M67. Using observed amplitudes of solar p-mode oscillations, and published scaling laws with spectral type, we show that direct detection of solar-analog oscillations on 13th-magnitude M67 stars is possible with a several-night 4-m network campaign. Asteroseismology on a substantial ensemble of cluster stars promises to allow fundamental new tests of stellar structure and evolution theory.