Seismic inversion of the solar entropy

Buldgen, G.; Salmon, Sébastien; Noels, A.; Scuflaire, R.; Reese, D. R.; Dupret, M.-A.; Colgan, J.; Fontes, Christopher J.; Eggenberger, P.; Hakel, P.; Kilcrease, D. P.; Turck‐Chièze, S.

doi:10.1051/0004-6361/201731354

Cited by 20 publications

(22 citation statements)

References 36 publications

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“…The sound-speed discrepancy becomes slightly smaller using the new LANL OPLIB opacities instead of the LLNL OPAL opacities [7,14]. Inversions for solar entropy [15] and the Ledoux discriminant [16] give additional constraints on the solar interior, highlighting further the effects of opacity differences between OPAL and OPLIB.…”

Section: Introductionmentioning

confidence: 97%

Opacity Effects on Pulsations of Main-Sequence A-Type Stars

Guzik¹,

Fontes²,

Fryer³

2018

Atoms

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Opacity enhancements for stellar interior conditions have been explored to explain observed pulsation frequencies and to extend the pulsation instability region for B-type main-sequence variable stars [see, e.g., 1-6]. For these stars, the pulsations are driven in the region of the opacity bump of Fe-group elements at ∼200,000 K in the stellar envelope. Here we explore effects of opacity enhancements for the somewhat cooler main-sequence A-type stars, in which p-mode pulsations are driven instead in the second helium ionization region at ∼50,000 K. We compare models using the new LANL OPLIB [7] vs. LLNL OPAL [8] opacities for the AGSS09 [9] solar mixture. For models of 2 solar masses and effective temperature 7600 K, opacity enhancements have only a mild effect on pulsations, shifting mode frequencies and/or slightly changing kinetic-energy growth rates. Increased opacity near the bump at 200,000 K can induce convection that may alter composition gradients created by diffusive settling and radiative levitation. Opacity increases around the hydrogen and 1st He ionization region (13,000 K) can cause additional higher-frequency p modes to be excited, raising the possibility that improved treatment of these layers may result in prediction of new modes that could be tested by observations. New or wider convective zones and higher convective velocities produced by opacity increases could also affect angular momentum transport during evolution. More work needs to be done to quantify the effects of opacity on the boundaries of the pulsation instability regions for A-type stars.

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Section: Introductionmentioning

confidence: 97%

Opacity Effects on Pulsations of Main-Sequence A-Type Stars

Guzik¹,

Fontes²,

Fryer³

2018

Atoms

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“…The CLES evolutionary code was developed in the early 2000s by the asteroseismology group of the University of Liège, and has been continuously updated. We present here only the main input physics used for UCDs, and refer to Scuflaire et al (2008) for the main numerical features (see also Buldgen et al 2016Buldgen et al , 2017a, for CLES in the context of the Sun and solar-like stars). CLES includes different choices for EOS, opacity and atmosphere tables but here we mention only those relevant for the study of UCDs.…”

Section: Input Physicsmentioning

confidence: 99%

Evolutionary Models for Ultracool Dwarfs

Fernandes

Grootel²,

Salmon³

et al. 2019

ApJ

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Ultracool dwarfs have emerged as key targets for searches of transiting exoplanets. Precise estimates of the host parameters (including mass, age, and radius) are fundamental to constrain the physical properties of orbiting exoplanets. We have extended our evolutionary code CLES (Code Liégeois d'Evolution Stellaire) to the ultracool dwarf regime. We include relevant equations of state for H, He, as well as C and O elements to cover the temperature-density regime of ultracool dwarf interiors. For various metallicities, we couple the interior models to two sets of model atmospheres as surface boundary conditions. We show that including C and O in the EOS has a significant effect close the H-burning limit mass. The typical systematic error associated with uncertainties in input physics in evolutionary models is ∼ 0.0005M . We test model results against observations for objects whose parameters have been determined from independent techniques. We are able to reproduce dynamical mass measurements of LSPM J1314+1320AB within 1σ with the condition of varying the metallicity (determined from calibrations) up to 2.5σ. For GJ 65AB, a 2σ agreement is obtained between individual masses from differential astrometry and those from evolutionary models. We provide tables of ultracool dwarf models for various masses and metallicities that can be used as reference when estimating parameters for ultracool objects.

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“…Recently, we presented in Buldgen et al (2017b) approaches to change the structural variables of the variational equations which could in turn be used in helio-and asteroseismology. In Buldgen et al (2017e), we presented inversion results of an entropy proxy, denoted S 5/3 = P ρ 5/3 which provides interesting insights on the solar structure. In Fig.…”

Section: Entropy Proxy Inversionsmentioning

confidence: 99%

“…These inversions were already presented in Gough and Kosovichev (1993b); Elliott (1996); Takata and Montgomery (2002); Kosovichev (1999) but have not been exploited to analyse the discrepancies found for models built with the recent abundance tables of Asplund et al (2009). This analysis was carried out in Buldgen et al (2017e) and Buldgen et al (2018), where in this last paper, an extended set of models is analysed.…”

Section: Ledoux Discriminant Inversionsmentioning

confidence: 99%

Progress in Global Helioseismology: A New Light on the Solar Modeling Problem and Its Implications for Solar-Like Stars

Buldgen

Salmon

Noels

2019

Front. Astron. Space Sci.

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Since the first observations of solar oscillations in 1960, helioseismology has probably been one of the most successful fields of astrophysics. Data of unprecedented quality were obtained through the implementation of networks of ground-based observatories such as the GONG project or the BiSON network, coupled with space-based telescopes such as SOHO and SDO missions and more data is expected from the Solar Orbiter mission. Besides the improvement of observational data, solar seismologists developed sophisticated techniques to infer the internal structure of the Sun from its eigenfrequencies. These methods, then already extensively used in the field of Geophysics, are called inversion techniques. They allowed to precisely determine the position of the solar convective envelope, the helium abundance in this region and the internal radial profiles of given thermodynamic quantities. Back in 1990s these comparisons showed a very high agreement between solar models and the Sun. However, the downward revision of the CNO surface abundances in the Sun in 2005, confirmed in 2009, induced a drastic reduction of this agreement leading to the so-called solar modelling problem. More than ten years later, in the era of the space-based photometry missions which have established asteroseismology of solar-like stars as a standard approach to obtain their masses, radii and ages, the solar modelling problem still awaits a solution. In this paper, we will present the results of new helioseismic inversions, discuss the current uncertainties of solar models as well as some possible solutions to the solar modelling problem. We will show how helioseismology can help us grasp what is amiss in our solar models. We will also show that, far from being an argument about details of solar models, the solar problem has significant implications for seismology of solar-like stars, on the main sequence and beyond, impacting asteroseismology as a whole as well as the fields requiring precise and accurate knowledge of stellar masses, radii and ages, such as Galactic archaeology and exoplanetology.

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Seismic inversion of the solar entropy

Cited by 20 publications

References 36 publications

Opacity Effects on Pulsations of Main-Sequence A-Type Stars

Opacity Effects on Pulsations of Main-Sequence A-Type Stars

Evolutionary Models for Ultracool Dwarfs

Progress in Global Helioseismology: A New Light on the Solar Modeling Problem and Its Implications for Solar-Like Stars

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