RV photometry phase difference

Forums Spectroscopy Model-based Interpretation of Cepheid spectra RV photometry phase difference

Robin Leadbeater

Nice work detecting pulsations at this RV level with the LHIRES and separating them out from the orbital component (I was slightly worried when I saw your RV and light curves in phase as The RV curve in Cepheids is normally approximately antiphase but then I noticed your light curve  Y is plotted in increasing magnitude)

RV measurements can be tricky with the H alpha line because of its width.   Narrow metal lines are easier, particularly if you can measure a few of them but then in the absence of telluric lines, a stable reference is difficult to arrange. I used two Si II lines with lamp lines superimposed on the spectrum during the exposure to follow pulsations in Deneb for example. 


at 18:30 

which suggested a long term sigma precision of 0.5km/s  is possible