Long-Term Aspects of Multi-Site Campaigns

Abstract

Organizing worldwide multi-site campaigns utilizing a large number of participating observatories can be difficult. For some types of multi-periodic pulsating variables, concentrated campaigns from only two carefully selected observatories can be just as valuable. This is demonstrated with new data for the S Scuti star FG Vir, where the nine frequencies of pulsation can be correctly identified from the measurements originating in only two time zones. Major long-term applications of multi-site campaigns require that the multi-site data be analyzed together with previously existing data. This raises the problem of the proper frequency sampling, which is examined by a numerical experiment. Although the photometric frequencies of pulsation for δ Scuti stars are found in the range of 4 to 50 cycles per day, we give evidence for the existence of additional frequencies outside this range. These additional frequencies include combinations and harmonics of the main frequencies. In order to include these very low and very high frequencies, the observing and reduction techniques for multi-site campaigns need to be revised.