Precise radial velocities. I - A preliminary search for oscillations in Arcturus

The 6300 wavelength region of Arcturus was observed through a coude spectrometer of a 107 inch telescope in a search for analogs of the solar five-minute oscillations. Small, apparent shifts of stellar lines were referenced against those of telluric O2 interspersed throughout the spectrum. The technique gives high quality (90-95 percent) results with negligible photometric errors. The observed errors arise from atmospheric air currents caused by passing clouds, thermal convection cells, and g-mode waves. Even when velocity excursions occur from these events, adjacent measurements maintain a scatter of plus/minus six to plus/minus eight m/s. Observations of Arcturus gave negative results suggesting that any nonradial oscillations must have a semiamplitude less than or equal to five m/s, if its dominant period is between 15 minutes and half a day.