Seismic constraints on the internal structure of evolved stars: From high-luminosity RGB to AGB stars

Abstract

The space-borne missions CoRoT and Kepler opened up a new opportunity for better understanding stellar evolution by probing stellar interiors with unrivalled high-precision photometric data. Kepler has observed stellar oscillation for four years, which gave access to excellent frequency resolution that enables deciphering the oscillation spectrum of evolved red giant branch and asymptotic giant branch stars. The internal structure of stars in the upper parts of the red and asymptotic giant branches is poorly constrained, which makes the distinction between red and asymptotic giants difficult. We perform a thorough seismic analysis to address the physical conditions inside these stars and to distinguish them. We studied the oscillation mode properties of about 2.000 evolved giants in a model described by the asymptotic pressure-mode pattern of red giants, which includes the signature of the helium second-ionisation zone. We extracted the mode properties up to the degree l = 3 and investigated their dependence on stellar mass, metallicity, and evolutionary status. We identify a clear difference in the signature of the helium second-ionisation zone between red and asymptotic giants. We also detect a clear shortage of the energy of l = 1 modes after the core-He-burning phase. Furthermore, we note that the mode damping observed on the asymptotic giant branch is similar to that observed on the red giant branch. We highlight that the signature of the helium second-ionisation zone varies with stellar evolution. This provides us with a physical basis for distinguishing red giant branch stars from asymptotic giants. Here, our investigation of stellar oscillations allows us to constrain the physical processes and the key events that occur during the advanced stages of stellar evolution, with emphasis on the ascent along the asymptotic giant branch, including the asymptotic giant branch bump.

20 pages, 12 figures, accepted in A&A

References in corpus (29)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
• The K2 Mission: Characterization and Early results
• The connection between stellar granulation and oscillation as seen by the Kepler mission
• Standing on the shoulders of Dwarfs: the $Kepler$ asteroseismic LEGACY sample I - oscillation mode parameters
• Mixed modes in red giants: a window on stellar evolution
• An asteroseismic signature of helium ionization
• NGC 6819: testing the asteroseismic mass scale, mass loss, and evidence for products of non-standard evolution
• Accurate p-mode measurements of the G0V metal-rich CoRoT target HD 52265
• Bayesian peak bagging analysis of 19 low-mass low-luminosity red giants observed with Kepler
• Non-radial oscillations in M-giant semi-regular variables: Stellar models and Kepler observations
• Visibilities and bolometric corrections for stellar oscillation modes observed by Kepler
• Asteroseismic estimate of helium abundance of a solar analog binary system
• Angular momentum redistribution by mixed modes in evolved low-mass stars. II. Spin-down of the core of red giants induced by mixed modes
• Dipole modes with depressed amplitudes in red giants are mixed modes
• Theoretical power spectra of mixed modes in low mass red giant stars
• On the surface physics affecting solar oscillation frequencies
• A New Method for the Asteroseismic Determination of the Evolutionary State of Red-Giant Stars
• Period spacings in red giants; III. Coupling factors of mixed modes
• Oscillation mode linewidths and heights of 23 main-sequence stars observed by Kepler
• Damping rates of solar-like oscillations across the HR diagram. Theoretical calculations confronted to CoRoT and Kepler observations
• Prospects for asteroseismic inference on the envelope helium abundance in red giant stars
• Helium signature in red giant oscillation patterns observed by Kepler
• Asteroseismology of luminous red giants with Kepler I: Long Period Variables with radial and non-radial modes
• On the asymptotic acoustic-mode phase in red-giant stars and its dependence on evolutionary state
• A closure model with plumes II. Application to the stochastic excitation of stellar p modes
• Seismic performance
• On using dipolar modes to constrain the helium glitch in red-giant stars
• Release note: Massive peak bagging of red giants in the Kepler field

Cited by in corpus (10)

• APOKASC-3: The Third Joint Spectroscopic and Asteroseismic catalog for Evolved Stars in the Kepler Fields
• A prescription for the asteroseismic surface correction
• Integrated Mass Loss of Evolved Stars in M4 using Asteroseismology
• Revised extinctions and radii for 1.5 million stars observed by APOGEE, GALAH, and RAVE
• HD-TESS: An Asteroseismic Catalog of Bright Red Giants within TESS Continuous Viewing Zones
• Red giants evolutionary status determination: the complete Kepler catalog
• Advancing accuracy in age determinations of old-disk stars using an oscillating red giant in an eclipsing binary
• Characterising the AGB bump and its potential to constrain mixing processes in stellar interiors
• Evolutionary and Observational Properties of Red Giant Acoustic Glitch Signatures
• Physical interpretation of the oscillation spectrum on the RGB and AGB