On attempting to automate the identification of mixed dipole modes for subgiant stars

Appourchaux, T.

doi:10.1051/0004-6361/202038834

Cited by 14 publications

(10 citation statements)

References 44 publications

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“…The user who would like to use this recipe should be aware that in its current version, apollinaire provides no method to automatically compute guesses for mixed-mode parameters. Such methods were presented, for example, in Mosser et al (2015) or Appourchaux (2020). We provide here an example 9 of such a fit performed on KIC 5723165, a subgiant star observed by Kepler in short cadence in Q1, Q5, and continuously from Q7 to Q13 for a total of ∼760 days (e.g.…”

Section: Appendix A: Psd Resampling For Background Fitmentioning

confidence: 99%

Deciphering stellar chorus: apollinaire, a Python 3 module for Bayesian peakbagging in helioseismology and asteroseismology

Breton

García

Ballot

et al. 2022

A&A

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Since the asteroseismic revolution, the availability of efficient and reliable methods to extract stellar-oscillation mode parameters has been an important part of modern stellar physics. In the fields of helio-and asteroseismology, these methods are usually referred to as peakbagging. Here, we introduce the apollinaire module, a new Python 3 open-source Markov Chain Monte Carlo (MCMC) framework dedicated to peakbagging. We extensively describe the theoretical framework necessary to understand MCMC peakbagging methods for disk-integrated helio-and asteroseismic observations. In particular, we present the models that are used to estimate the posterior probability function in a peakbagging framework. A description of the apollinaire module is then provided. We explain how the module enables stellar background, p-mode global pattern, and individual-mode parameter extraction. By taking into account instrumental specificities, stellar inclination angle, rotational splittings, and asymmetries, the module allows a large variety of p-mode models to be fitted that are suited for solar and stellar data analysis with different instruments. After presenting a validation of the module with a Monte Carlo fitting trial on synthetic data, it is benchmarked by comparing its outputs with results obtained with other peakbagging codes. We present our analysis of the power spectral density (PSD) of 89 one-year subseries of GOLF observations. We also selected six stars from the Kepler LEGACY sample in order to demonstrate the code abilities on asteroseismic data. The parameters we extract with apollinaire are in good agreement with those presented in the literature and demonstrate the precision and reliability of the module.

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Section: Appendix A: Psd Resampling For Background Fitmentioning

confidence: 99%

Deciphering stellar chorus: apollinaire, a Python 3 module for Bayesian peakbagging in helioseismology and asteroseismology

Breton

García

Ballot

et al. 2022

A&A

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show abstract

“…With the aim of defining relevant seismic indicators and relying on a prior modes extraction (e.g. Mosser et al 2015;Gehan et al 2018;Appourchaux 2020), we present a method of automated, consistent, robust, and fast adjust- Evolution of q throughout the binned spectrum presented in Fig. 23 ment of observed and theoretical mixed-mode oscillation spectra.…”

Section: Discussionmentioning

confidence: 99%

“…In the present paper, we considered modes in the range of the width 0.8ν 0.88 max around ν max , determined to include at least ten radial modes for the youngest subgiant models (Mosser et al 2012b;Appourchaux 2020). We immediately see that this range evolves with ν max , both in terms of its central frequency ν max and in the number of modes.…”

Section: Impact Of the Considered Set Of Modesmentioning

confidence: 99%

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Asteroseismology of evolved stars with EGGMiMoSA I. Theoretical mixed-mode patterns from the subgiant to the RGB phase

Farnir,

Pinçon,

Dupret

et al. 2021

Preprint

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Context. In the context of an ever increasing amount of highly precise data, thanks to the numerous space-borne missions, came a revolution in stellar physics. This data allowed asteroseismology to thrive and improve our general knowledge of stars. Important results were obtained about giant stars owing to the presence of 'mixed modes' in their oscillation spectra. These modes carry information about the whole stellar interior, enabling the comprehensive characterisation of their structure. Aims. The current study is part of a series of papers that provide a technique to coherently and robustly analyse the mixed-modes frequency spectra and characterise the stellar structure of stars on both the subgiant branch and red-giant branch (RGB). In this paper we aim at defining seismic indicators, relevant of the stellar structure, as well as studying their evolution along a grid of models. Methods. The proposed method, EGGMiMoSA, relies on the asymptotic description of mixed modes. It defines appropriate initial guesses for the parameters of the asymptotic formulation and uses a Levenberg-Marquardt minimisation scheme in order to adjust the complex mixed-modes pattern in a fast and robust way. Results. We are able to follow the evolution of the mixed-modes parameters along a grid of models from the subgiant phase to the RGB bump, therefore extending previous works. We show the impact of the stellar mass and composition on the evolution of these parameters. We observe that the evolution of the period spacing ∆π1, pressure offset p, gravity offset g , and coupling factor q as a function of the large frequency separation ∆ν is little affected by the chemical composition and that it follows two different regimes depending on the evolutionary stage. On the subgiant branch, the stellar models display a moderate core-envelope density contrast. Therefore, the evolution of ∆π1, p, g , and q significantly changes with the stellar mass. Furthermore, we demonstrate that, for a given metallicity and with proper measurements of the period spacing ∆π1 and large frequency separation ∆ν, we may unambiguously constrain the stellar mass, radius and age of a subgiant star. Conversely, as the star reaches the red-giant branch, the core-envelope density contrast becomes very large. Consequently, the evolution of p, g and q as a function of ∆ν becomes independent of the stellar mass. This is also true for ∆π1 in stars with masses 1.8M because of core electron degeneracy. This degeneracy in ∆π1 is lifted for higher masses, again allowing for a precise measurement of the stellar age. Overall, our computations qualitatively agree with previous observed and theoretical studies. Conclusions. The method provides automated measurements of the adjusted parameters along a grid of models and opens the way to the precise seismic characterisation of both subgiants and red giants. In the following papers of the series, we will explore further refinements to the technique as well as its application to observed stars.

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“…The exploitation of such an amount of information and its physical interpretation have greatly relied on analytical descriptions of the linear stellar oscillations. In particular, theoretical expressions of the eigenfrequency patterns appeared to be crucial for extracting the prevailing features of the observed oscillation power spectra, defining seismic indicators that are relevant of the stellar structure, and enabling statistical studies on large samples of stars via automated methods (e.g., see Farnir et al 2019;Appourchaux 2020;Gehan et al 2021, for recent examples).…”

Section: Introductionmentioning

confidence: 99%

Multi-cavity gravito-acoustic oscillation modes in stars

Pinçon

Takata²

2022

A&A

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Context. Over recent decades, asteroseismology has proven to be a powerful method for probing stellar interiors. Analytical descriptions of the global oscillation modes, in combination with pulsation codes, have provided valuable help in processing and interpreting the large amount of seismic data collected, for instance, by space-borne missions CoRoT, Kepler, and TESS. These prior results have paved the way to more in-depth analyses of the oscillation spectra of stars in order to delve into subtle properties of their interiors. This purpose conversely requires innovative theoretical descriptions of stellar oscillations. Aims. In this paper, we aim to analytically express the resonance condition of the adiabatic oscillation modes of spherical stars in a very general way that is applicable at different evolutionary stages. Methods. In the present formulation, a star is represented as an acoustic interferometer composed of a multitude of resonant cavities where waves can propagate and the short-wavelength JWKB approximation is met. Each cavity is separated from the adjacent ones by barriers, which correspond to regions either where waves are evanescent or where the JWKB approximation fails. Each barrier is associated with a reflection and transmission coefficient. The stationary modes are then computed using two different physical representations: (1) studying the infinite-time reflections and transmissions of a wave energy ray through the ensemble of cavities or (2) solving the linear boundary value problem using the progressive matching of the wave function from one barrier to the adjacent one between the core and surface. Results. Both physical pictures provide the same resonance condition, which ultimately turns out to depend on a number of parameters: the reflection and transmission phase lags introduced by each barrier, the coupling factor associated with each barrier, and the wave number integral over each resonant cavity. Using such a formulation, we can retrieve, in a practical way, the usual forms derived in previous works in the case of mixed modes with two or three cavities coupled though evanescent barriers, low- and large-amplitude glitches, and the simultaneous presence of evanescent regions and glitches. Conclusions. The resonance condition obtained in this work provides a new tool that is useful in predicting the oscillation spectra of stars and interpreting seismic observations at different evolutionary stages in a simple way. Practical applications require more detailed analyses to make the link between the reflection-transmission parameters and the internal structure. These aspects will be the subject of a future paper.

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On attempting to automate the identification of mixed dipole modes for subgiant stars

Cited by 14 publications

References 44 publications

Deciphering stellar chorus: apollinaire, a Python 3 module for Bayesian peakbagging in helioseismology and asteroseismology

Deciphering stellar chorus: apollinaire, a Python 3 module for Bayesian peakbagging in helioseismology and asteroseismology

Asteroseismology of evolved stars with EGGMiMoSA I. Theoretical mixed-mode patterns from the subgiant to the RGB phase

Multi-cavity gravito-acoustic oscillation modes in stars

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