Ultraviolet and Infrared Monitoring of FG Sagittae during 1982--1989: Evolutionary Status
Fernandez-Castro, Telmo; Cassatella, Angelo; Eiroa, Carlos; Montesinos, Benjamin; Gonzalez-Riestra, Rosario; Jimenez-Fuensalida, Jesus
United Kingdom, Spain, Italy, Netherlands
Abstract
Ultraviolet IUE spectra and infrared JHKL photometry of FG Sge obtained over the period 1982-1989 indicate that the cooling rate of the star observed until about 1980 seems to have stopped and that an increase of the effective temperature may have occurred, this being a significant change in the evolutionary path traced so far. The current spectral type of FG Sge is F6-7 I, as deduced from UV data. There is evidence of the existence of an envelope responsible for the infrared excesses observed at longer wavelengths. The short-term variation period is about 100-110 + or - 15 days, and it has remained stable since 1979, apart from small fluctuations of + or - 15 days.