J/A+A/699/A148 Multi-mode pulsations with CO5BOLD (Ahmad+, 2025)
Multi-mode pulsations in AGB stars: Insights from 3D RHD CO5BOLD simulations.
Ahmad A., Freytag B., Hoefner S.
<Astron. Astrophys. 699, A148 (2025)>
=2025A&A...699A.148A 2025A&A...699A.148A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, variable ; Models, atmosphere
Keywords: convection - shock waves - methods: numerical -
stars: AGB and post-AGB - stars: atmospheres - stars: oscillations
Abstract:
Stars on the asymptotic giant branch (AGB) can exhibit acoustic
pulsation modes of different radial orders, along with non-radial
modes, throughout their evolution. These pulsations are essential to
the mass-loss process and influence the evolutionary pathways of AGB
stars. Period-luminosity (P-L) relations serve as a valuable
diagnostic for understanding stellar evolution along the AGB.
Three-dimensional (3D) radiation-hydrodynamic (RHD) simulations
provide a powerful tool for investigating pulsation phenomena driven
by convective processes and their non-linear coupling with stellar
oscillations.
We investigate multi-mode pulsations in AGB stars using advanced 3D
'star-in-a-box' simulations with the CO5BOLD RHD code. Signatures
of these multi-mode pulsations were weak in our previous 3D models.
Our focus is on identifying and characterising the various pulsation
modes, examining their persistence and transitions, and comparing the
results with one-dimensional (1D) model predictions and observational
data where applicable.
We produced a new model grid comprising AGB stars with current masses
of 0.7, 0.8, and 1M☉. Fourier analysis was applied to dynamic,
time-dependent quantities to extract dominant pulsation modes and
their corresponding periods. Additionally, wavelet transforms were
employed to identify mode-switching behaviour over time.
The simulations reveal radial, non-radial, fundamental, and overtone
modes, with their transitions and dominance depending on stellar
parameters. The models successfully reproduce the P-L sequences
found in AGB stars. Mode-switching phenomena are found in both the
models and wavelet analyses of observational data, allowing us to
infer similarities in the underlying pulsation dynamics. The results
confirm the dependence of pulsation periods on mean stellar density
and underscore the significant role of convection for the amplitude of
multi-mode pulsations.
These 3D simulations highlight the natural emergence of multi-mode
pulsations, including both radial and non-radial modes, driven by the
self-consistent interplay of convection and oscillations. Our
findings underscore the value of 3D RHD models in capturing the
non-linear behaviour of AGB pulsations, providing insights into mode
switching, envelope structures, and potential links to episodic
mass-loss events.
Description:
The catalog contains the global stellar parameters of all
models analysed in the article, together with the derived pulsation
periods.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
models.dat 983 65 Global stellar parameters of all models analysed
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Byte-by-byte Description of file: models.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Model Model name
14- 16 F3.1 Msun Mass Current stellar mass
18- 35 F18.14 Rsun Radius Mean stellar radius, determined
at the entropy minimum
37- 53 F17.12 K Teff Mean effective temperature
55- 72 F18.13 Lsun Lum Mean stellar luminosity
74- 85 F12.9 [cm/s2] logg Base-10 logarithm of the mean
surface gravity
87- 91 F5.1 --- xpoints Number of grid points along one
Cartesian axis; total spatial
resolution is xpoints3
93-111 F19.14 Rsun x3gridRad Edge length of the cubic
computational domain
113-119 F7.1 --- tpoints Number of snapshots in the
temporal dimension
121-138 F18.12 d SimTime Total time-span over which the
above quantities have been
averaged
140-158 F19.15 d puls-per-l0-n0 Period l0-n0 (1)
160-178 F19.15 d e_puls-per-l0-n0 Uncertainty in period l0-n0
180-198 F19.15 d puls-per-l0-n1 ?=-1 Period l0-n1 (1)
200-218 F19.16 d e_puls-per-l0-n1 ?=-1 Uncertainty in
period l0-n1 (1)
220-237 F18.15 d puls-per-l0-n2 ?=-1 Period l0-n2 (1)
239-257 F19.16 d e_puls-per-l0-n2 ?=-1 Uncertainty in
period l0-n2 (1)
259-276 F18.15 d puls-per-l0-n3 ?=-1 Period l0-n3 (1)
278-296 F19.16 d e_puls-per-l0-n3 ?=-1 Uncertainty in
period l0-n3 (1)
298-315 F18.14 d puls-per-l1-n0 Period l1-n0 (1)
317-336 F20.16 d e_puls-per-l1-n0 Uncertainty in period l1-n0 (1)
338-356 F19.15 d puls-per-l1-n1 ?=-1 Period l1-n1 (1)
358-376 F19.16 d e_puls-per-l1-n1 ?=-1 Uncertainty in
period l1-n1 (1)
378-395 F18.15 d puls-per-l1-n2 ?=-1 Period l1-n2 (1)
397-415 F19.16 d e_puls-per-l1-n2 ?=-1 Uncertainty in
period l1-n2 (1)
417-434 F18.15 d puls-per-l1-n3 ?=-1 Period l1-n3 (1)
436-454 F19.16 d e_puls-per-l1-n3 ?=-1 Uncertainty in
period l1-n3 (1)
456-473 F18.14 d puls-per-l2-n0 Period l2-n0 (1)
475-493 F19.15 d e_puls-per-l2-n0 Uncertainty in period l2-n0 (1)
495-513 F19.15 d puls-per-l2-n1 ?=-1 Period l2-n1 (1)
515-533 F19.16 d e_puls-per-l2-n1 ?=-1 Uncertainty in
period l2-n1 (1)
535-552 F18.15 d puls-per-l2-n2 ?=-1 Period l2-n2 (1)
554-572 F19.16 d e_puls-per-l2-n2 ?=-1 Uncertainty in
period l2-n2 (1)
574-591 F18.15 d puls-per-l2-n3 ?=-1 Period l2-n3 (1)
593-611 F19.16 d e_puls-per-l2-n3 ?=-1 Uncertainty in
period l2-n3 (1)
613-631 F19.17 --- puls-pfrac-l0-n0overn Power over n: l0-n0 (2)
633-653 F21.19 --- puls-pfrac-l0-n1overn Power over n: l0-n1 (2)
655-674 F20.18 --- puls-pfrac-l0-n2overn Power over n: l0-n2 (2)
676-694 F19.17 --- puls-pfrac-l1-n0overn Power over n: l1-n0 (2)
696-714 F19.17 --- puls-pfrac-l1-n1overn Power over n: l1-n1 (2)
716-735 F20.18 --- puls-pfrac-l1-n2overn Power over n: l1-n2 (2)
737-755 F19.17 --- puls-pfrac-l2-n0overn Power over n: l2-n0 (2)
757-775 F19.17 --- puls-pfrac-l2-n1overn Power over n: l2-n1 (2)
777-796 F20.18 --- puls-pfrac-l2-n2overn Power over n: l2-n2 (2)
798-816 F19.17 --- puls-pfrac-l0-n0overl Power over l: l0-n0 (3)
818-836 F19.17 --- puls-pfrac-l1-n0overl Power over l: l1-n0 (3)
838-856 F19.17 --- puls-pfrac-l2-n0overl Power over l: l2-n0 (3)
858-878 F21.18 --- puls-pfrac-l0-n1overl ?=-1 Power over l: l0-n1 (3)
880-899 F20.17 --- puls-pfrac-l1-n1overl ?=-1 Power over l: l1-n1 (3)
901-920 F20.17 --- puls-pfrac-l2-n1overl ?=-1 Power over l: l2-n1 (3)
922-941 F20.17 --- puls-pfrac-l0-n2overl ?=-1 Power over l: l0-n2 (3)
943-962 F20.17 --- puls-pfrac-l1-n2overl ?=-1 Power over l: l1-n2 (3)
964-983 F20.17 --- puls-pfrac-l2-n2overl ?=-1 Power over l: l2-n2 (3)
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Note (1): Columns beginning with puls-per-* and e_puls-per-* give, respectively,
the mode period and its uncertainty, both in days.
The suffix l-n encodes the spherical-harmonic degree l = x and
radial overtone order n = y. For example:
- puls-per-l0-n0 - fundamental radial mode (l = 0, n = 0) period
- e_puls-per-l2-n1 - uncertainty in the quadrupole (l = 2) first-overtone
(n = 1) period
Note (2): Columns prefixed with powerfrac-* quantify the fractional power in
selected modes:
- powerfrac_l-novern - at fixed degree l, the fraction contributed by
overtone n relative to the total power at that l.
Note (3): Columns prefixed with powerfrac-* quantify the fractional power in
selected modes:
- powerfrac_l-noverl - at fixed overtone n, the fraction contributed by
degree l relative to the total power at that n.
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Acknowledgements:
Arief Ahmad, arief.ahmad(at)physics.uu.se
(End) Patricia Vannier [CDS] 13-May-2025