Colours and TEFF of Main Sequence Stars Covering the Galactic Metallicity Range

Alonso, A.; Arribas, S.; Martinez-Roger, C.

doi:10.1007/978-94-011-0125-7_44

Cited by 460 publications

(917 citation statements)

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“…To compute the zero-point, we used the Hayes (1985) spectrum of Vega with a flux of 3.44 × 10 −9 erg cm −2 s −1Å−1 at 5556Å. The V magnitude of Vega is set to 0.03 mag, which is consistent with the value adopted by Alonso et al (1995), i.e. in agreement with our prescriptions to transform the theoretical parameters of the isochrones to the observational plane.…”

Section: Base Modelsmentioning

confidence: 86%

“…For this purpose we combine these relations and the model atmosphere predictions of Bessell et al (1989Bessell et al ( , 1991 and the library of Fluks et al (1994). We also employ the metal-dependent bolometric corrections given by Alonso, Arribas & Martínez-Roger (1995) and Alonso et al (1999) for dwarfs and giants, respectively. Finally, we adopt BC⊙ = −0.12.…”

Section: Isochronesmentioning

confidence: 99%

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Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models

Vazdekis

Coelho

Cassisi

et al. 2015

Monthly Notices of the Royal Astronomical Society

343

394

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We present models that predict spectra of old-and intermediate-aged stellar populations at 2.51Å (FWHM) with varying [α/Fe] abundance. The models are based on the MILES library and on corrections from theoretical stellar spectra. The models employ recent [Mg/Fe] determinations for the MILES stars and BaSTI scaled-solar and α-enhanced isochrones. We compute models for a suite of IMF shapes and slopes, covering a wide age/metallicity range. Using BASTI, we also compute "base models" matching The Galactic abundance pattern. We confirm that the α-enhanced models show a flux excess with respect to the scaled-solar models blue-ward ∼4500Å, which increases with age and metallicity. We also confirm that both [MgFe] and [MgFe] ′ indices are [α/Fe]-insensitive. We show that the sensitivity of the higher order Balmer lines to [α/Fe] resides in their pseudo-continua, with narrower index definitions yielding lower sensitivity. We confirm that the α-enhanced models yield bluer (redder) colours in the blue (red) spectral range. To match optical colours of massive galaxies we require both α-enhancement and a bottom-heavy IMF. The comparison of Globular Cluster line-strengths with our predictions match the [Mg/Fe] determinations from their individual stars. We obtain good fits to both full spectra and indices of galaxies with varying [α/Fe]. Using thousands of SDSS galaxy spectra we obtain a linear relation between a proxy for the abundance,

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Section: Base Modelsmentioning

confidence: 86%

Section: Isochronesmentioning

confidence: 99%

Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models

Vazdekis

Coelho

Cassisi

et al. 2015

Monthly Notices of the Royal Astronomical Society

343

394

View full text Add to dashboard Cite

show abstract

“…Harris (1996) catalogue. For each star we obtained values for T eff from the two calibrations, Alonso et al (1999) and Ramírez & Meléndez (2005), using the b − y, V − J, V − H and V − K colours (with appropriate transformations from 2MASS to the T CS system using the relations in Alonso et al 1994 andCarpenter 2001). We adopted the average T eff , weighted by the uncertainties for each colour, and note that the mean difference, Alonso et al − Ramírez & Meléndez, is +55 K ± 17 K (σ = 64 K).…”

Section: Discussionmentioning

confidence: 99%

CNO abundances in the globular clusters NGC 1851 and NGC 6752★

Yong¹,

Grundahl²,

Norris³

2014

Monthly Notices of the Royal Astronomical Society

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We measure the C+N+O abundance sum in red giant stars in two Galactic globular clusters, NGC 1851 and NGC 6752. NGC 1851 has a split subgiant branch which could be due to different ages or C+N+O content while NGC 6752 is representative of the least complex globular clusters. For NGC 1851 and NGC 6752, we obtain average values of A(C+N+O) = 8.16 ± 0.10 (σ = 0.34) and 7.62 ± 0.02 (σ = 0.06), respectively. When taking into account the measurement errors, we find a constant C+N+O abundance sum in NGC 6752. The C+N+O abundance dispersion is only 0.06 dex, and such a result requires that the source of the light element abundance variations does not increase the C+N+O sum in this cluster. For NGC 1851, we confirm a large spread in C+N+O. In this cluster, the anomalous RGB has a higher C+N+O content than the canonical RGB by a factor of four (∼0.6 dex). This result lends further support to the idea that the two subgiant branches in NGC 1851 are roughly coeval, but with different CNO abundances.

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“…For example, in the library of stellar spectra assembled by Cohen et al (1999), absolute spectrophotometry has the tendency to return angular diameters systematically smaller by a few percent with respect to interferometry. Smaller angular diameters for cool giants would also explain the dichotomy reported by Alonso et al (1994) when trying to set on the same scale T eff derived for hot and cool stars from interferometry with those determined from the Infrared Flux Method. Recent revision of the latter technique support in fact hotter effective temperatures also for dwarfs and subgiants (Casagrande et al 2006(Casagrande et al , 2010 and the extension to giants is currently under way (Casagrande et al, in prep.).…”

Section: Estimation Of Diameter Correction: 1d Versus 3d Modelsmentioning

confidence: 98%

Three-dimensional hydrodynamical simulations of red giant stars: semi-global models for interpreting interferometric observations

Chiavassa¹,

Collet²,

Casagrande³

et al. 2010

A&A

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Context. Theoretical predictions from models of red giant branch stars are a valuable tool for various applications in astrophysics ranging from galactic chemical evolution to studies of exoplanetary systems. Aims. We use the radiative transfer code Optim3D and realistic 3D radiative-hydrodynamical (RHD) surface convection simulations of red giants to explore the impact of granulation on interferometric observables. We assess how 3D simulations of surface convection can be validated against observations. Methods. We computed intensity maps for the 3D simulation snapshots in two filters, the optical at 5000 ± 300 Å and the K band 2.14±0.26 μm FLUOR filter, corresponding to the wavelength-range of instruments mounted on the CHARA interferometer. From the intensity maps, we constructed images of the stellar disks and account for center-to-limb variations. We then derived interferometric visibility amplitudes and phases. We study their behavior with position angle and wavelength, and compare them with CHARA observations of the red giant star HD 214868. Results. We provide average limb darkening coefficients for different metallicities and wavelengths ranges. We explain prospects for detecting and characterizing granulation and center-to-limb variations of red giant stars with today's interferometers. Regarding interferometric observables, we find that the effect of convective-related surface structures depends on metallicity and surface gravity. We provide theoretical closure-phases that should be incorporated into the analysis of red giant planet companion closure phase signals. We estimate 3D−1D corrections to stellar radii determination: 3D models are ∼3.5% smaller to ∼1% larger in the optical than 1D, and roughly 0.5 to 1.5% smaller in the infrared. Even if these corrections are small, they are needed to properly set the zero point of effective temperature scale derived by interferometry and to strengthen the confidence of existing red giant catalogs of calibrating stars for interferometry. Finally, we show that our RHD simulations provide an excellent fit to the red giant HD 214868 even though more observations are needed at higher spatial frequencies and shorter wavelength.

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Colours and TEFF of Main Sequence Stars Covering the Galactic Metallicity Range

Cited by 460 publications

References 0 publications

Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models

Evolutionary stellar population synthesis with MILES – II. Scaled-solar and α-enhanced models

CNO abundances in the globular clusters NGC 1851 and NGC 6752★

Three-dimensional hydrodynamical simulations of red giant stars: semi-global models for interpreting interferometric observations

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