Infrared Velocities of Long Period Variables: CO delta(upsilon)=3 in Four Miras and Five SR Variables

Abstract

Time series of high resolution spectra have been obtained for a set of 9 long period variables (LPVs), 4 Miras, and 5 semiregular variables (SRVs) in the 1.6-1.8μm infrared. The vibration-rotational lines of CO Δν=3 in this spectral interval have previously been shown to be good probes of the pulsational properties of cool variable stars. We use these spectral lines to show the differences and similarities in the radial velocity amplitude and excitation temperature among the Mira, SRa-, and SRb-type variables. All Miras of our sample show similar radial velocity variations and similar amplitudes independent of their period. The SRVs differ from the Miras by significantly lower amplitudes. All the LPVs show random velocity changes at the few km s<SUP>-1 level. We find a correlation between radial velocity amplitude and visual amplitude.</SUP>