Red Giant Branch Stars: The Theoretical Framework

By Maurizio Salaris, Santi Cassisi, A. Weiss. 2002

160 citations recorded by the source corpus.

Theoretical predictions of red giant branch stars’ effective temperatures, colors, luminosities, and surface chemical abundances are a necessary tool for the astrophysical interpretation of the visible–near‐infrared integrated light from unresolved stellar populations, the color‐magnitude diagrams of resolved stellar clusters and galaxies, and spectroscopic determinations of red giant chemical abundances. On the other hand, the comparison with empirical constraints provides a stringent test for the accuracy of present generations of red giant models. We review the current status of red giant star modeling, discussing in detail the still‐existing uncertainties affecting the model input physics (e.g., electron conduction opacity, treatment of the superadiabatic convection) and the adequacy of the physical assumptions built into the model computations. We compare theory with several observational features of the red giant branch in Galactic globular clusters, such as the luminosity function “bump,” the luminosity of the red giant branch tip, and the envelope chemical abundance patterns, to show the level of agreement between current stellar models and empirical data concerning the stellar luminosities, star counts, and surface chemical abundances.

Subfields: Astronomy and Astrophysics, Education, Instrumentation

View Paper: https://www.semanticscholar.org/paper/71f49809126826102f4eaa48d772186bdec0340a

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Citations in the corpus

ON THE SHOULDERS OF GIANTS: PROPERTIES OF THE STELLAR HALO AND THE MILKY WAY MASS DISTRIBUTION (2014, background): “The theoretical (Salaris et al. 2002) and observational evidence (Langer et al. 2000) suggests that the luminosity functioof the giants follow a power law.”
A Large Stellar Evolution Database for Population Synthesis Studies. I. Scaled Solar Models and Isochrones (2004, methodology): “…we think these effective temperature discrepancies along the RGB may be due to a combination of different boundary conditions and EOS, we note that Salaris et al. (2002) have shown how different boundary conditions [e.g., the gray vs. Krishna Swamy T( ) relationship] produce different solar…”
Updated Electron-Conduction Opacities: The Impact on Low-Mass Stellar Models (2007, background): “The whole thermal stratification inside the He-core and the temperature at the base of the surrounding H-burning shell depend strongly on the efficiency of electron conduction (for a detailed discussion on this issue see Catelan et al. 1996; Salaris et al. 2002, and references therein).”
Tip of the Red Giant Branch Distances. II. Zero-Point Calibration (2007, methodology): “…is very bright, MI 4; (2) the physical processes behind the use of this method are well understood (Salaris & Cassisi 1997; Madore et al. 1997; Salaris et al. 2002); (3) the measurements are extremely efficient, considering it is possible to get a distance with only two observations; (4) the…”
THE GHOSTS SURVEY. I. HUBBLE SPACE TELESCOPE ADVANCED CAMERA FOR SURVEYS DATA (2011, background): “As this process occurs at a constant critical mass, the maximum luminosity of the RGB sequence is theoretically well defined, particularly in the I band where the bolometric luminosity peaks (Lee et al. 1993; Salaris & Cassisi 1997; Salaris et al. 2002).”
CHEMICAL ABUNDANCES FOR 855 GIANTS IN THE GLOBULAR CLUSTER OMEGA CENTAURI (NGC 5139) (2010, background): “In stars with normal helium abundances, it is not believed that this can occur until the hydrogen burning shell erases the molecular weight barrier left behind by the convective envelope after first dredge–up (e.g., see review by Salaris et al. 2002).”
GYRE: An open-source stellar oscillation code based on a new Magnus Multiple Shooting Scheme (2013, background): “This reversal shows up in the Hertzsprung-Russell diagram (HRD) as a narrow zig-zag in a single star’s evolutionary track, and it causes a bump in the luminosity function of cluster members on the RGB, hence the name (see Salaris et al. 2002, for a more detailed discussion).”
Population effects on the red giant clump absolute magnitude: The K-band (2002, background): “…the different values of the helium core mass at the flash (see, e.g., Castellani et al. 2000; Salaris, Cassisi & Weiss 2002); however, the variation of their brightness with respect to age and metallicity is much more consistently predicted by theory (Castellani et al. 2000; Salaris et al. 2002).”
The Adequacy of Stellar Evolution Models for the Interpretation of the Color-Magnitude Diagrams of Resolved Stellar Populations (2005, methodology): “We refer the reader to Salaris et al. (2002) for a recent review on the current status of RGB modeling.”
Age and Metallicity Distribution of the Galactic Bulge from Extensive Optical and Near-IR Stellar Photometry (2002, background): “All in all, Salaris et al. (2002) estimate an uncertainty of ∼0.10–0.15 mag in the range of optical colors spanned by theoretical RGBs, which can also be taken as indicative of the uncertainty in the range of the near-IR colors.”
Mixed modes in red giants: a window on stellar evolution (2014, background): “When the helium core of a low-mass star on the RGB reaches about 0.47 M , runaway ignition in degenerate conditions produces the helium flash, which very rapidly transports the star from the tip of the RGB to the red clump (Salaris et al. 2002).”