SIMBAD references

The ''bump'' is a prominent feature of the red giant branch (RGB) luminosity function of stellar clusters. Through constructing a grid of models with different masses and metallicities to study the feature of the RGB bump luminosity we find that the luminosity increases almost monotonically with increasing mass for a given metallicity and decreases monotonically with increasing metallicity. Moreover, different stars have different shapes of the RGB bump. It is correlated with the sharpness of the H discontinuity, which is left over by the convection envelope during the first dredge-up. Using the periodicity in the small separations d₀₁, d₁₀ to probe the internal structure, we find that, at about half the acoustic radius, the sound speed has a sharp variation that is caused by a local depression of the first adiabatic exponent Γ₁ in the second helium ionization zone. It induces an oscillation modulation in d₀₁, d₁₀with a period of 6.4 µ Hz. Meanwhile, in the same model, the base of the convective envelope is located at a relatively small acoustic radius t_envp/T, which is about 10^–1. It is too deep to detect the exact location of the bottom of the outer convective envelope. In order to discriminate the evolutionary status of different stars, we calculate the asymptotic g-mode period spacing ΔΠ₁. We find that ΔΠ₁ decreases monotonically with evolution. It is a reliable parameter for distinguishing stars in different positions of the RGB bump.