Reduction of matrix effect in determination of rare elements by atomic emission method

From an analysis of 115-day variations of the IR brightness of FG Sge it follows that these variations are mainly due to the stellar photospheric temperature variations. From the energy distribution in the spectrum of FG Sge in the range 1.25-3.5 μm that star is classified as G2 I and F5 I near the minimum and maximum of the 115-day variations respectively. The luminosity of FG Sge at the maximum of the 115-day cycle is almost by a factor of 2 larger than at the minimum. The radius variations do not exceed 10 percent. By the character of the IR brightness variations FG Seg is at present similar to the variables of the δ Cep or SRd types