A low-amplitude periodicity in the radial velocity and chromospheric emission of Beta Geminorum

Abstract

Using high-quality spectra obtained with the hydrogen fluoride technique at the Canada-France-Hawaii 3.6-m telescope and Dominion Astrophysical Observatory 1.22-m telescope, we have detected a low-amplitude periodicity in both the radial velocity and chromospheric emission of Beta Geminorum. In addition, we have detected a long-term change (greater than 12 yr) in this star's chromospheric emission which is reminiscent of solar-type magnetic cycles believed present in giants of similar spectral type. The radial-velocity variations can be fitted by a sinusoid with amplitude and period of K = 46.23 +/- 3.9 m/s, P = 584.65 +/- 3.3 d. A similar, statistically significant (false-alarm probability of 1 percent) period is found in the residuals from the long-term trend in the chromospheric emission: P = 587.7 +/-12 d. However, because of the weakness of the signal, K = 0.583 +/- 0.19 mA, this detection needs confirmation.