Abundances of carbon, nitrogen, oxygen, and other elements in the atmospheres of the giants 15 ori and 22 ɛ sex

Abstract

We have used high-resolution spectra to study the giants 15 Ori and 22 ɛ Sex. The effective temperature T _eff = 7060 K, gravity log g = 3.16, and microturbulence velocity ξ _t = 3.5 km/s were determined for 15 Ori, with T _eff = 7350 K and log g = 3.90 for 22 ɛ Sex (the microturbulence velocity for 22 ɛ Sex was assumed to be ξ _t = 2.7 km/s). We estimated the abundances of C, N, O, Na, Si, Ca, Fe, and Ba (N and Ba, for 15 Ori only). The abundances of carbon, iron, and oxygen in 22 ɛ Sex are higher than the solar values by +0.31 dex, +0.33 dex, and +0.18 dex, respectively, while the calcium abundance is −0.19 dex below the solar level. For 15 Ori, we find a slight carbon excess (+0.19 dex), a slight nitrogen deficiency (−0.13 dex), and a considerable deficiency of silicon (−0.42 dex). The abundances of the remaining elements in both stars are near-solar. We find no substantial differences between the abundances derived for 15 Ori and 22 ɛ Sex and the results of earlier studies of giants by both ourselves and Erspamer and North. A comparison of the atmospheric elemental abundances of giants and δ Scuti stars indicates that the abundances of some lighter elements (oxygen, sodium, silicon, and possibly nitrogen) are somewhat lower for δ Scuti stars than for A-F giants. We determined the masses, radii, luminosities, and ages for 15 Ori and 22 ɛ Sex.