ВИЗНАЧЕННЯ ЕФЕКТИВНИХ ТЕМПЕРАТУР ТА ПОВЕРХНЕВИХ ГРАВІТАЦІЙ ДЕКІЛЬКОХ ЗІР ТИПУ А НА ОСНОВІ ФОТОМЕТРИЧНИХ ПАРАМЕТРІВ

The fundamental parameters – effective temperatures (Teff) and surface gravities (g) – have been determined for of A-type stars: HD 6364 (A5/7III), HD 6365 (A3III/IV), HD 6492 (A9V), HD 6723 (A8V), HD 25093 (A7II/III), HD 123798 (A8/9V), HD 129175 (A6V), HD 129433 (A0IV), HD 129660 (A7V), and HD 209124 (A0III-IV). In order to determine the chemical composition of stars using the model or synthetic spectrum method, it is essential to know their fundamental parameters – effective temperatures (Teff) and surface gravity (g). Teff and log g are the basic parameters of stellar atmosphere models – determining these parameters is necessary to compute stellar atmosphere models. On the other hand, by knowing the effective temperature (Teff) and surface gravity (g), it is possible to calculate the evolutionary parameters of stars – their masses (M), luminosities (L), radii (R), and ages (t). Thus, the accurate determination of the chemical composition of stars through the model or synthetic spectrum method depends on the precision of the Teff and log g parameters. The effective temperatures (Teff) and surface gravities (log g) of stars were determined using photometric method. The method employed is based on comparing observed and theoretical values of the photometric indices [c₁], Q, and β. This method is a simple and accurate method. The Q index in the UBV photometric system is defined as Q = (U – B) - 0.72(B – V), while the [c₁] index in the uvby photometric system is defined as [c₁] = c₁ - 0.2(b - y). These indices are free from the effects of absorption in the interstellar medium. The following values of Teff and log g were obtained for the studied stars: HD 6364: Teff = 7610 K, log g = 4.25; HD 6365: Teff = 7880 K, log g = 4.35; HD 6492: Teff = 7390 K, log g = 3.70; HD 6723: Teff = 7380 K, log g = 4.00; HD 25093: Teff = 7780 K, log g = 4.10; HD 123798: Teff = 7090 K, log g = 3.65; HD 129175: Teff = 8220 K, log g = 4.35; HD 129433: Teff = 9960 K, log g = 4.00; HD 129660: Teff = 7710 K, log g = 3.65; HD 209124: Teff = 9820 K, log g = 3.80.