ОСОБЛИВОСТІ ФОТОМЕТРИЧНОЇ ЗМІННОСТІ FI SGE НА ОСНОВІ СПОСТЕРЕЖЕНЬ TRANSITING EXOPLANET SURVEY SATELLITE

We present the result of the analysis of the FI Sge individual light curves constructed on Transiting Exoplanet Survey Satellite (TESS) observations. FI Sge the RR Lyrae pulsating variable star with bicyclicity effects and possible Blazhko effect. In the present study, we analyzed 3603 photometric data obtained by the Transiting Exoplanet Survey Satellite (TESS) in the special TESS IR bandpass with a time resolution of about 10 minutes. The observations covered a 27-day interval (BJD 2459769.90 − 2459796.12) with a small gap of about a day. The full data set contains 52 minima and 51 maxima of the seasonal light curve. We suppose that for this data set, the analysis of the light curve shapes in minima provides more reliable results. We studied the variations of the minima’ shapes of the individual light curves at common and for the separate affinity groups. The last one allowed us to detect not only classical bicyclicity, but also secondary bicyclicity for FI Sge. This result was obtained at first and it is atypical behavior of light curves for pulsating variable stars.