A Comparison of Some Quantities in Spectral Type G2 Giants and Dwarfs

A Comparison of Some Quantities in Spectral Type G2 Giants and Dwarfs
Quantity	Dwarfs (Luminosity Class V)	Giants (Luminosity Class III)
Electron Pressure, P_e [dyn cm^-2]	37.2	5.13
Effective Temperature, T [K]	5720	5200
N₁/N₀ for Fe	7.86	9.08
N₁/N₀ for Sr	696	1364

A Comparison of Some Quantities Characterizing Fe and Sr in G2 V and III
Quantity	I [ev]	Θ_IIII	Θ_VI	u₀(T_V)	u₀(T_III)	u₁(T_V)	u₁(T_III)	log(2u₁(T_V)/u0(T_V)	log(2u₁(T_III)/u0(T_III)
Fe	7.87	7.63	6.93	31.09	28.86	47.08	44.77	0.481	0.492
Sr	5.69	5.52	5.01	1.42	1.24	2.30	2.22	0.510	0.554

Note that:
     (1) N(SrII)/N(SrI) increases much more rapidly with luminosity than does N(FeII)/N(FeI). This is mostly because of the
          smaller ionization potential of Sr which makes it less sensitive to the small T decline with increasing luminosity. Fe is
          more T sensitive. (Note: I_I(Fe) = 7.87 eV, I_I(Sr) = 5.695 eV.)
     (2) In Fe the small drop in T with increasing luminosity, almost cancels the increase in N(FeII)/N(FeI) which results from
          decreasing P_e.
     (3) Therefore the line strength ratio λ4077(SrII)/λ4045(FeI) increases significantly with luminosity class in F, G and K
           stars, since λ4077 increases appreciably with increasing luminosity class, while λ4045 slightly decreases.