Bump Cepheids in the Magellanic Clouds: Metallicities, the Distances to the LMC and SMC, and the Pulsation-Evolution Mass Discrepancy

By S. Keller, P. R. Wood. 2006

193 citations recorded by the source corpus.

We use nonlinear pulsation models to reproduce the observed light and color curves for two samples of bump Cepheid variables, 19 from the Large Magellanic Cloud and 9 from the Small Magellanic Cloud. This analysis determines the fundamental parameters mass, luminosity, effective temperature, metallicity, distance, and reddening for the sample of stars. The use of the light-curve shape alone to determine metallicity is a new modeling technique introduced here. The metallicity, distance, and reddening distributions for the two samples are in agreement with those of similar stellar populations in the literature. The distance modulus of the Large Magellanic Cloud is determined to be 18.54 ± 0.018, and the distance modulus of the Small Magellanic Cloud is determined to be 18.93 ± 0.024. The mean Cepheid metallicities are Z = 0.0091 ± 0.0007 and 0.0050 ± 0.0005 for the LMC and SMC, respectively. The masses derived from pulsation analysis are significantly less than those predicted by stellar evolutionary models with no or mild convective core overshoot. We show that this discrepancy cannot be accounted for by uncertainties in our input opacities or in mass-loss physics. We interpret the observed mass discrepancy in terms of enhanced internal mixing in the vicinity of the convective core during the main-sequence lifetime and find that the overshoot parameter Λc rises from 0.688 ± 0.009Hp at the mean LMC metallicity to 0.746 ± 0.009Hp in the SMC.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/aae51fb7827ef7e668138244dcade956c5f00610

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Citations in the corpus

Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation (2019, background): “…of light and radial velocity curves of classical pulsators (e.g., Feuchtinger et al. 2000; Marconi et al. 2015), features of specific objects (e.g., Keller & Wood 2006; Marconi et al. 2013; Smolec et al. 2013), and dynamical phenomena such as the Hertzsprung progression (e.g., Hertzsprung 1926a;…”
THE STATE OF THE GAS AND THE RELATION BETWEEN GAS AND STAR FORMATION AT LOW METALLICITY: THE SMALL MAGELLANIC CLOUD (2011, background): “Located scarcely 61 kpc away (Hilditch et al. 2005; Keller & Wood 2006; Szewczyk et al. 2009), the SMC is the nearest gas-rich low metallicity dwarf galaxy with active star-formation (ZSMC ∼ Z⊙/5, Dufour 1984; Kurt et al. 1999; Pagel 2003).”
DIRECT DETECTION OF THE CLOSE COMPANION OF POLARIS WITH THE HUBBLE SPACE TELESCOPE (2005, background): “However, recent evolutionary and pulsation constraints for Galactic (Bono et al. 2001b; Caputo et al. 2005; Keller 2008; Natale et al. 2008) and Magellanic (Bono et al. 2002; Keller & Wood 2006) Cepheids still imply a discrepancy in masses at the ∼15–20% level.”
CLUSTERING OF LOCAL GROUP DISTANCES: PUBLICATION BIAS OR CORRELATED MEASUREMENTS? III. THE SMALL MAGELLANIC CLOUD (2014, methodology): “The single bumpCepheid measurement yields (m−M)bumpCeph0 = 18.93± 0.06 mag (Keller & Wood 2006), where we determined the uncertainty ourselves based on the published data, because the authors only provided the uncertainty on the mean rather than the standard deviation of the distribution (see the…”
Modeling the Panchromatic Spectral Energy Distributions of Galaxies (2013, background): “With regards to the convective core, a wide body of observational evidence favors the existence of a moderate amount of overshooting in the mass range 1.1 M/M⊙ 7 (Stothers 1991, Nordstroem, Andersen & Andersen 1997, VandenBerg & Stetson 2004, Keller & Wood 2006).”
Escape of Ionizing Radiation from High-Redshift Galaxies (2007, background): “Note that emission line studies (Peimbert et al. 2000; Keller & Wood 2006) usually indicate somewhat larger values for both metallicities than the absorption line metallicities that we adopt.”