Observational limits on companions to g29-38

Abstract

Recent interest in the variable (DAV) white dwarf G29-38 has been stirred by a tentative report of a radial velocity variation that may be due to an unseen companion. Earlier evidence for a brown dwarf in the system has come from an observed infrared excess in the star's spectrum. For asteroseismological reasons, we have accumulated more than five seasons of high-speed photometric data on the star. By measuring the phase of an isolated, stable frequency in the power spectrum, we show the measured variation is not due (at least in its entirety) to an orbital companion. Because any orbital radial velocity variation must result in a systematic phase variation, the data we present can be used to place stringent limits on the types of companions the system may contain.