From the Main Sequence to the Red Giant Branch: Asteroseismology of Solar-like Oscillators
Abstract
Asteroseismology of solar-like oscillators has undergone a remarkable transformation over the past decade, propelled by high-precision photometric data from Kepler, K2, and TESS, alongside significant advances in stellar modeling. These developments have enabled detailed investigations of stellar interiors across a broad range of evolutionary stages - from the main sequence, through the subgiant phase, to the red giant branch. In this talk, I will present the fundamental methods of asteroseismology applied to solar-like oscillators and highlight recent breakthroughs based on both global seismic parameters and individual oscillation mode frequencies. I will emphasize how these tools have deepened our understanding of stellar structure, evolution, and internal dynamics, particularly in evolved stars. Key results include constraints on internal dynamics, mixing processes, and stellar binarity. I will also discuss insights gained from ensemble asteroseismology across diverse Galactic populations. Ongoing challenges will be addressed, such as the calibration and limitations of scaling relations, the phenomenon of mode suppression, and the integration of seismic diagnostics with spectroscopic and astrometric data. Finally, I will outline how upcoming missions and surveys, in particular ESA’s PLATO that are expected to shape the next era of solar-like asteroseismology.
Full text
Paul Gerhard Beck Ramón y Cajal Fellow From the Main Sequence to the Red Giant Branch: Asteroseismology of Solar-like Oscillators Universidad de la Laguna, Tenerife, Spain Instituto de Astrofísica de Canarias, Tenerife, Spain www.paul-beck.com, @elAustrofisico
The evolution of a solar-like star Density map calculated from Yu+ 2018, Mathur+ 2022 1.5-0.8Mo F, G, K The Sun (1Ro)1 Mass range
The evolution of a solar-like star Density map calculated from Yu+ 2018, Mathur+ 2022 Sub-giant star (~3Ro) 1.b 1.5-0.8Mo F, G, K
The evolution of a solar-like star Density map calculated from Yu+ 2018, Mathur+ 2022 Star at the Tip of the RGB (200Ro ≈ 1AU) 1.b 1.5-0.8Mo F, G, K ≳3Mo à Then open up to mention H-shell and helium core burnign
The evolution of a solar-like star Mirror principle: envelope expands, while core shrinks •Hekker+ (2020): Entropy •Miller Bertolami (2022): the steep density gradient in the radiative zone Density map calculated from Yu+ 2018, Mathur+ 2022 Red Clump Star (~10Ro) 2 1.5-0.8Mo F, G, K ≳3Mo
Asteroseismology allows sounding the internal structure & dynamics of stars Atmosphere: Photosphere (90%) & Chromosphere àAll measurements from the thin, luminous atmosphere Teff, logg, [M/H], vsini, turbulences & RV •Stellar modeling (1D) Based on boundary conditions from the atmosphere. 2 The Key to Evolution is a hidden one Enjoy some typical Austrian Sweets 3
ESA SoHo : ~30 years of data Recent VIRGO / GOLF data from the ESA SOHO (provided by R.A.Garcia and J.Jimenez) •Rotation & Spots: weeks •Convection: hours & days •Oscillations: minutes •Photom. Noise: constant Stellar Noise is signal Each datapoint is the superposition of: 4
Rotation Spots Convection Granulation The solar oscillation spectrum Image courtesy: Hans Kjeldsen 5
Photon Noise Rotation Spots Convection Granulation Oscillations GREGOR at Teide Observatory, Tenerife HiFI+3, TiO 7078Å, 1arcsec = 725km, Diameter earth: 17.6 arcsec Image courtesy: C. Cuckein; Size of Earth The solar oscillation spectrum 5.b
Modulation of the ridge structure Glitches: sudden changes in the oscillation cavity Houdayer+ 2021, A&A 655, A85 •Helium ionization zones Vrard+ 2015, Verma+ 2019 •Discontinuities in the buoyancy frequency Vrard+ 2022, Cunha+ 2024 Surface corrections: FreqObs – FreqModel à Result of imperfect modeling of the outermost layers: non-adiabatic effects, turbulent convection, 3D vs 1D Correction, typically through relations Kjeldsen+ 2008, Ball & Gizon 2014, Sonoi+ 2015 à using frequency and mode inertia à Complication on mixed modes (Ball et al. 2018) Li+ 2023: Empirical approach Kallinger 2025: Bayesian forward modelling 1. What Are Glitches? Definition: Localised, rapid structural variations inside the star that cause modulations in the otherwise regular seismic frequency patterns. KIC 6775098, Grossmann+ (in prep, #26) 10
Surface corrections Wang+ (2023) from asteroseismic modeling of 1153 RGB stars KIC 6775098, Grossmann+ (in prep, #26) 11
Ensemble seismology: Kepler & TESS Providing masses, radii and ages for different galactic latitudes APOKASC-3 (Pinsonneault+ 2025): •~12k giants + APOGEE spectroscopy •Fract. uncertainties: mass (~4%), radius (~2%), age (~11%) •àScaling relations accurate on lower RGB, deviations at higher Lum APO-K2 (I: Zinn 2022 , II: Warfield 2024) •~7.5k stars+ APOGEE spectroscopy •Fract. uncertainties: mass (∼11%), radius (∼7%), age (∼20%). Super-Nyquist Seismology (Liagre+ 2025, subm) •First ensemble study of supernyquist/close-to-nyquist osc. •masses, radii, ages for ~900 stars 20sec TESS Cadence: is better suited for dwarfs: Huber+ (2022) TESS continuous viewing zone: 6.4k stars; Mackereth+ (2021) AI use of seismic parameters: 160k stars; Hon+ (2021) Mackereth Hon Beck (2025) all-sky mosaic (S1-60) by Ethan Kruse 12
Age uncertainties for stellar model for HD52265 by Lebreton & Goupil, 2014, A&A 569, A21 Teff & logg spectroscopy & Global seism. spectroscopy & Boutique mod. Modeling individual frequencies HRD position ~50% HRD + global ~50% Boutique modelling ~10% Search for best-fitting model, by comparing resonant frequencies computed from a model to observations Mathur+(2012), Appourchaux+(2012), Metcalfe+(2014), Davis+ (2015), Silva Aguirre+ (2015,2017), Creevey+ (2017), Chaplin+(2020), Montalban+ (2021) àMass: ±5%, Radius: ±3%, àAge: MS:≳10%, Giants: 30-50% àInternal structure & dynamics àExploring the low-metallicity regime Huber+ 2024, Larsen+ 2025, Lindsey+ 2025 Peak bagging codes: (Talk by Bhattacharya) e.g. Pbjam (Nilsen 2025), Diamonds (Corsaro & De Ridder 2014), Apollinaire (Breton et al. 2021), TACO (Heidelberg) Fitting of large samples: e.g. Lund+ (2017), Davis+ (2015), Kallinger (2018) 13
Mixed modes Beck+ 2011, Science 332; Bedding+ Nature 471; Mosser+ 2012, A&A 540
Mixed modes Cavity: Core Envelope Mixed Equidistant: in Period in frequency Modes g p #v ∝ c Large frequency separation p&g #v ∝ N2 Aymptotic period spacing of g-modes Observed mixed modes frequency patter Beck+ 2011, Science 332; Bedding+ Nature 471; Mosser+ 2012, A&A 540 14
Evolutionary States •Period spacings: core density àDistinguish between H-shell and He-core burning giants Bedding+ (2011), Mosser+ (2012) Vrard+ 2025, A&A, 697, A165: •Largest catalog for evolutionary states in evolved stars. •Compilation of 6 different seismic techniques to distinguish between RGB and RC/2RC •~19 000 stars have consensual determination •AGB determination is still uncertain Fig. calculated from the values Vrard+ 2025, A&A, 697, A165 Poster #98 by Nic Muntean 15
Rotational Splitting of Oscillation Modes Rotation lifts the degeneracy (W<<nmax) dƒ = m × W × (1-Cnℓ) ℓ=1, m=-1 ℓ=1, m=0 ℓ=1, m=+1 dƒ Azimutal oder m 16 Gizon 2003
Rotational Splitting of Oscillation Modes Rotation lifts the degeneracy (W<<nmax) dƒ = m × W × (1-Cnℓ) ℓ=1, m=-1 ℓ=1, m=0 ℓ=1, m=+1 dƒ Azimutal oder m Red Giant Core rotation: ~10x Beck+ 2012 Spin up on the Sub-giant branch: Deheuvels et al. 2012 Numerous large sample studies: Mosser+ 2012, Kuszlewicz+ 2023, Ahlborn+ 2025 Rigid rotation for >2Mo Deheuvels+ 2015, Tayar+ 2019 Angular momentum transport still challenging puzzle àtalk by Mayano (yesterday) àThis session: Gaira, Buchele, Deheuvels, Leclerc 17 Gizon 2003
Rotational Splitting of Oscillation Modes Rotation lifts the degeneracy (W<<nmax) dƒ = m × W × (1-Cnℓ) ℓ=1, m=-1 ℓ=1, m=0 ℓ=1, m=+1 dƒ Azimutal oder m Red Giant Core rotation: ~10x Beck+ 2012 Spin up on the Sub-giant branch: Deheuvels et al. 2012 Numerous large sample studies: Mosser+ 2012, Kuszlewicz+ 2023, Ahlborn+ 2025 Rigid rotation for >2Mo Deheuvels+ 2015, Tayar+ 2019 Angular momentum transport still challenging puzzle àtalk by Mayano (yesterday) àThis session: Gaira, Buchele, Deheuvels, Leclerc 17 Gizon 2003 Power [ppm2] 100 80 60 40 20 0 Power [ppm2/bin] 196194192190188186 Frequency [µhz] Frequency [µHz] ℓ=0 ℓ=2 ℓ=1
Science Validation and Calibration: 25k Giants SCV1: Binary Systems P. M a x t e d , P. B e c k , T.Morel, P.G a u l m e •SCV1a –Detached eclipsing binaries •SCV1b –Astrometric binaries ○~1000 systems with known inclination from Gaia DR3 ○Validation of stellar masses ○Combined modelling of two coeval stars SCV4: Solar-like Oscillators B.Mosser, A.Miglio, J.Montalban, P.Ve n t u ra ○24 000 dwarfs, Subgiants & Red Giants that are not in P-samples ○will be used to backtrack in time to the main sequence stage à core science SCV Lead: Zwintz 24
Big Questions Ultimate goal to reduce the age accuracy •for main-sequence stars to 10%, and further to 1% with data from the ESA PLATO and proposed HAYDN mission. •Improve the age accuracy for red-giants. Non-exclusive list of important questions to advance: àUnderstand the mechanisms transport angular momentum and how the rotational profile evolves? àHow accurate are our models of internal chemical composition and mixing processes? àHow does stellar magnetic activity affect oscillations and stellar structure? àHow to efficiently compute stellar evolution and internal dynamics in higher dimensions than 1D? 25
From the Main Sequence to the Red Giant Branch: Asteroseismology of Solarlike Oscillators Paul Gerhard Beck Ramón y Cajal Fellow Universidad de la Laguna, Tenerife, Spain Instituto de Astrofísica de Canarias, Tenerife, Spain www.paul-beck.com, @elAustrofisico
Solar-like oscillators have been a success story 35