ISOCHRONES FOR OLD (&gt;5 GYR) STARS AND STELLAR POPULATIONS. I. MODELS FOR –2.4 ⩽ [Fe/H] ⩽+0.6, 0.25 ⩽<i>Y</i>⩽ 0.33, AND –0.4 ⩽ [α/Fe] ⩽+0.4

VandenBerg, Don A.; Bergbusch, Peter A.; Ferguson, Jason W.; Edvardsson, B.

doi:10.1088/0004-637x/794/1/72

Cited by 107 publications

(97 citation statements)

References 97 publications

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“…As expected, the observed B − V colours of cool, faint stars are more problematic than their V − K S colours. Indeed, the close agreement of the isochrone with the observations on the (V − K S , V)-diagram suggests that the temperatures of the models are quite good (for additional discussion of this issue see VandenBerg et al 2014). If this is correct, then the deviations which are apparent at faint magnitudes in the other CMDs must be telling us something about the MARCS transformations, or the photometric data, or perhaps that the assumed metallicity or metals mixture …”

Section: (Ngc 2682)mentioning

confidence: 68%

“…In what follows, observations of these three systems are compared with the latest Victoria-Regina isochrones (VandenBerg et al 2014) on several different CMDs. Rather than correcting the photometry for the effects of reddening and distance to obtain the intrinsic colours and absolute magnitudes, the model luminosities and temperatures have been converted to the observed magnitudes and colours using the reddening-adjusted transformations presented in this investigation.…”

Section: Open and Globular Clustersmentioning

confidence: 99%

“…At higher luminosities, the predicted colours tend to be too blue, indicating a problem with either the MARCS transformations or the model temperatures or both. (For quite a thorough discussion of this issue, reference may be made to VandenBerg et al 2014.) Although Figs.…”

Section: Ngc 6791mentioning

confidence: 99%

“…In Figures 14 and 15, eight of the possible CMDs that can be produced from these data have been superimposed by the MS segment of the same 4.3 Gyr, [Fe/H] = 0.0 (e.g., Randich et al 2006Randich et al ,Önehag et al 2011, Y = 0.255 isochrone that was compared with observations for the upper MS and RGB stars of M 67 by VandenBerg et al (2014). In all cases, E(B − V) = 0.030 (SF11) and (m − M) 0 = 9.60 has been assumed.…”

Section: (Ngc 2682)mentioning

confidence: 99%

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Synthetic stellar photometry – I. General considerations and new transformations for broad-band systems

Casagrande¹,

VandenBerg²

2014

Monthly Notices of the Royal Astronomical Society

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After a pedagogical introduction to the main concepts of synthetic photometry, colours and bolometric corrections in the Johnson-Cousins, 2MASS, and HST-ACS/WFC3 photometric systems are generated from MARCS synthetic fluxes for various [Fe/H] and [α/Fe] combinations, and virtually any value of E(B − V) 0.7. The successes and failures of model fluxes in reproducing the observed magnitudes are highlighted. Overall, extant synthetic fluxes predict quite realistic broad-band colours and bolometric corrections, especially at optical and longer wavelengths: further improvements of the predictions for the blue and ultraviolet spectral regions await the use of hydrodynamic models where the microturbulent velocity is not treated as a free parameter. We show how the morphology of the colour-magnitude diagram (CMD) changes for different values of [Fe/H] and [α/Fe]; in particular,how suitable colour combinations can easily discriminate between red giant branch and lower main sequence populations with different [α/Fe], due to the concomitant loops and swings in the CMD. We also provide computer programs to produce tables of synthetic bolometric corrections as well as routines to interpolate in them. These colour-T eff -metallicity relations may be used to convert isochrones for different chemical compositions to various bandpasses assuming observed reddening values, thus bypassing the standard assumption of a constant colour excess for stars of different spectral type. We also show how such an assumption can lead to significant systematic errors. The MARCS transformations presented in this study promise to provide important constraints on our understanding of the multiple stellar populations found in globular clusters (e.g., the colours of lower main sequence stars are predicted to depend strongly on [α/Fe]) and of those located towards/in the Galactic bulge.

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Section: (Ngc 2682)mentioning

confidence: 68%

Section: Open and Globular Clustersmentioning

confidence: 99%

Section: Ngc 6791mentioning

confidence: 99%

Section: (Ngc 2682)mentioning

confidence: 99%

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Synthetic stellar photometry – I. General considerations and new transformations for broad-band systems

Casagrande¹,

VandenBerg²

2014

Monthly Notices of the Royal Astronomical Society

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257

321

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“…This code is described in VandenBerg et al (2012) and references therein. The tracks present here come from the work of VandenBerg et al (2014), and are available for download 9 .…”

Section: Introductionmentioning

confidence: 99%

Confronting uncertainties in stellar physics

Stancliffe

Fossati

Passy

et al. 2016

A&A

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We assess the systematic uncertainties in stellar evolutionary calculations for low-to intermediate-mass, main-sequence stars. We compare published stellar tracks from several different evolution codes with our own tracks computed using the stellar codes stars and mesa. In particular, we focus on tracks of 1 and 3 M at solar metallicity. We find that the spread in the available 1 M tracks (computed before the recent solar composition revision) can be covered by tracks between 0.97−1.01 M computed with the stars code. We assess some possible causes of the origin of this uncertainty, including how the choice of input physics and the solar constraints used to perform the solar calibration affect the tracks. We find that for a 1 M track, uncertainties of around 10% in the initial hydrogen abundance and initial metallicity produce around a 2% error in mass. For the 3 M tracks, there is very little difference between the tracks from the various different stellar codes. The main difference comes in the extent of the main sequence, which we believe results from the different choices of the implementation of convective overshooting in the core. Uncertainties in the initial abundances lead to a 1−2% error in the mass determination. These uncertainties cover only part of the total error budget, which should also include uncertainties in the input physics (e.g., reaction rates, opacities, convective models) and any missing physics (e.g., radiative levitation, rotation, magnetic fields). Uncertainties in stellar surface properties such as luminosity and effective temperature will further reduce the accuracy of any potential mass determinations.

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Metallicity and distance of NGC 6362 from its RR Lyrae and SX Phoenicis stars

et al. 2018

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New time-series VI CCD photometry of the globular cluster NGC 6362 is studied with the aim of estimating the reddening, mean metallicity, and distance of the cluster from its population of RR Lyrae stars. The Fourier decomposition of carefully selected single-mode RR Lyrae light curves, and the use of well-established semiempirical calibrations and revised zero points, lead to the values of [Fe/H] UVES −1.066 ± 0.126 and −1.08 ± 0.16 and distances of 7.93 ± 0.32 and 8.02 ± 0.15 kpc from the RRab and RRc stars, respectively. The distribution of RR Lyrae stars in the horizontal branch shows a neat segregation of pulsating modes about the red edge of the first overtone instability strip, which is not necessarily expected in an OoI-type cluster like NGC 6362. Four RRab stars are found to be likely advanced in their evolution toward the AGB. One new foreground SX Phe star, some 4 kpc in front of the cluster and projected onto the field of our images, is reported. We comment on the heavy light contamination, by a very close neighbouring star, of the peculiar double-mode V37 variable, recently postulated as a non-typical RRc variable. KEYWORDS globular clusters: individual (NGC 6362) -horizontal branch -RR Lyrae starsblue stragglers 1

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ISOCHRONES FOR OLD (>5 GYR) STARS AND STELLAR POPULATIONS. I. MODELS FOR –2.4 ⩽ [Fe/H] ⩽+0.6, 0.25 ⩽Y⩽ 0.33, AND –0.4 ⩽ [α/Fe] ⩽+0.4

Cited by 107 publications

References 97 publications

Synthetic stellar photometry – I. General considerations and new transformations for broad-band systems

Synthetic stellar photometry – I. General considerations and new transformations for broad-band systems

Confronting uncertainties in stellar physics

Metallicity and distance of NGC 6362 from its RR Lyrae and SX Phoenicis stars

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