The impact of an updated14N(p,γ)15O reaction rate on advanced evolutionary stages of low-mass stellar models

Pietrinferni, A.; Cassisi, S.; Salaris, Maurizio

doi:10.1051/0004-6361/201015065

Cited by 18 publications

(19 citation statements)

References 44 publications

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“…More specifically, for this comparison the PGPUC SEC uses the F04 rate, whereas BaSTI uses the NACRE one. Pietrinferni et al (2010) pointed out that two ZAHB loci created with these rates have a difference in luminosity of the order presented here at log T eff = 3.85, the ZAHB determined with the NACRE reaction rate being brighter (at this metallicity). As far as the predicted temperatures are concerned, we do not find any significant differences.…”

Section: Comparison With Other Codesmentioning

confidence: 51%

Effects of helium enrichment in globular clusters

Valcarce

Catelan

Sweigart

2012

A&A

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Aims. Recently, the study of globular cluster (GC) color−magnitude diagrams (CMDs) has shown that some of them harbor multiple populations with different chemical compositions and/or ages. In the first case, the most common candidate is a spread in the initial helium abundance, but this quantity is difficult to determine spectroscopically due to the fact that helium absorption lines are not present in cooler stars, whereas for hotter GC stars gravitational settling of helium becomes important. As a consequence, indirect methods to determine the initial helium abundance among populations are necessary. For that reason, in this series of papers, we investigate the effects of a helium enrichment in populations covering the range of GC metallicities. Methods. In this first paper, we present the theoretical evolutionary tracks, isochrones, and zero-age horizontal branch (ZAHB) loci calculated with the Princeton-Goddard-PUC (PGPUC) stellar evolutionary code, which has been updated with the most recent input physics and compared with other theoretical databases. The chemical composition grid covers 9 metallicities ranging from Z = 1.60 × 10 −4 to 1.57 × 10 −2 (−2.25 < ∼ [Fe/H] < ∼ −0.25), 7 helium abundances from Y = 0.230 to 0.370, and an alpha-element enhancement of [α/Fe] = 0.3. Results. The effects of different helium abundances that can be observed in isochrones are: splits in the main sequence (MS), differences in the luminosity (L) and effective temperature (T eff ) of the turn off point, splits in the sub giant branch being more prominent for lower ages or higher metallicities, splits in the lower red giant branch (RGB) being more prominent for higher ages or higher metallicities, differences in L of the RGB bump (with small changes in T eff ), and differences in L at the RGB tip. At the ZAHB, when Y is increased there is an increase of L for low T eff , which is affected in different degrees depending on the age of the GC being studied. Finally, the ZAHB morphology distribution depending on the age explains how for higher GC metallicities a population with higher helium abundance could be hidden at the red ZAHB locus.

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Section: Comparison With Other Codesmentioning

confidence: 51%

Effects of helium enrichment in globular clusters

Valcarce

Catelan

Sweigart

2012

A&A

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“…Pietrinferni et al (2010) found that the LUNA reaction rate leads to a larger value for M He c , of the order of ≈ 0.002 − 0.003M ⊙ , with respect to the results obtained by using the NACRE rate. Despite the larger He core mass of the models based on the LUNA rate, their TRGB brightness is lower by about ∆ log(L TRGB /L ⊙ ) = 0.02.…”

Section: Nuclear Reaction Ratesmentioning

confidence: 59%

“…The impact of the LUNA rate on the He core mass and brightness at the RGB tip of low-mass stars has been investigated by Weiss et al (2005) and Pietrinferni et al (2010). Pietrinferni et al (2010) found that the LUNA reaction rate leads to a larger value for M He c , of the order of ≈ 0.002 − 0.003M ⊙ , with respect to the results obtained by using the NACRE rate.…”

Section: Nuclear Reaction Ratesmentioning

confidence: 99%

The brightness of the red giant branch tip

Serenelli

Weiß

Cassisi

et al. 2017

A&A

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107

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Context. The brightness of the tip of the Red Giant Branch is a useful reference quantity for several fields of astrophysics. An accurate theoretical prediction is needed for such purposes. Aims. We intend to provide a solid theoretical prediction for it, valid for a reference set of standard physical assumptions, and mostly independent of numerical details. Methods. We examine the dependence on physical assumptions and numerical details, for a wide range of metallicities and masses, and based on two different stellar evolution codes. We adjust differences between the codes to treat the physics as identical as possible. After we have succeeded in reproducing the tip brightness between the codes, we present a reference set of models based on the most up to date physical inputs, but neglecting microscopic diffusion, and convert theoretical luminosities to observed infrared colours suitable for observations of resolved populations of stars and include analytic fits to facilitate their use. Results. We find that consistent use of updated nuclear reactions, including an appropriate treatment of the electron screening effects, and careful time-stepping on the upper red giant branch are the most important aspects to bring initially discrepant theoretical values into agreement. Small, but visible differences remain unexplained for very low metallicities and mass values at and above 1.2 M ⊙ , corresponding to ages younger than 4 Gyr. The colour transformations introduce larger uncertainties than the differences between the two stellar evolution codes. Conclusions. We demonstrate that careful stellar modeling allows an accurate prediction for the luminosity of the Red Giant Branch tip. Differences to empirically determined brightnesses may result either from insufficient colour transformations or from deficits in the constitutional physics. We present the best-tested theoretical reference values to date.

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“…Note that revisions to energetically important reaction rates can have a significant impact on stellar ages. Revisions of the 14 N(p, γ) 15 O rate by Formicola et al (2004) led to an increase in the predicted age of the oldest globular clusters , in addition to altering the lifetimes and luminosities of advanced evolutionary phases of low-mass stars (Pietrinferni et al 2010). When utilising a given set of tracks, one should always check that the reaction rates used are up-to-date.…”

Section: Discussionmentioning

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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The impact of an updated¹⁴N(p,γ)¹⁵O reaction rate on advanced evolutionary stages of low-mass stellar models

Cited by 18 publications

References 44 publications

Effects of helium enrichment in globular clusters

Effects of helium enrichment in globular clusters

The brightness of the red giant branch tip

Confronting uncertainties in stellar physics

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