Constraining transport of angular momentum in stars

Hartogh, J. W. den; Eggenberger, P.; Hirschi, Raphaël

doi:10.1051/0004-6361/201834330

Cited by 28 publications

(11 citation statements)

References 48 publications

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“…While Beck et al (2012) found that the cores of low-mass stars at the beginning of the red giant phase rotate 10 times faster than the surface, Deheuvels et al (2015) found that the cores of secondary clump stars rotate between one and three times faster than the envelopes. This is significantly closer to solid-body rotation than the subgiants studied in Deheuvels et al (2014) and consistent with limiting case theoretical arguments that strong coreenvelope coupling must be occurring in secondary clump stars (Tayar & Pinsonneault 2013;Cantiello et al 2014;den Hartogh et al 2019, see also Aerts et al 2019 for a more complete discussion of the available constraints on angular momentum evolution). However, due to the size of previous samples and the methods by which they were selected, it has been difficult to determine whether they accurately represent the full underlying distribution of core rotation rates in the secondary clump.…”

Section: Introductionsupporting

confidence: 82%

Core–Envelope Coupling in Intermediate-mass Core-helium Burning Stars

Tayar

Beck

Pinsonneault

et al. 2019

ApJ

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Stars between two and three solar masses rotate rapidly on the main sequence, and the detection of slow core and surface rotation in the core-helium burning phase for these stars places strong constraints on their angular momentum transport and loss. From a detailed asteroseismic study of the mixeddipole mode pattern in a carefully selected, representative sample of stars, we find that slow core rotation rates in the range reported by prior studies are a general phenomenon and not a selection effect. We show that the core rotation rates of these stars decline strongly with decreasing surface gravity during the core He-burning phase. We argue that this is a model-independent indication of significant rapid angular momentum transport between the cores and envelopes of these stars. We see a significant range in core rotation rates at all surface gravities, with little evidence for a convergence towards a uniform value. We demonstrate using evolutionary models that measured surface rotation periods are a biased tracer of the true surface rotation distribution, and argue for using stellar models for interpreting the contrast between core and surface rotation rates. The core rotation rates we measure do not have a strong mass or metallicity dependence. We argue that the emerging data strongly favors a model where angular momentum transport is much more efficient during the core He burning phase than in the shell burning phases which precede and follow it.

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Section: Introductionsupporting

confidence: 82%

Core–Envelope Coupling in Intermediate-mass Core-helium Burning Stars

Tayar

Beck

Pinsonneault

et al. 2019

ApJ

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“…So far, their impact on the rotation evolution of subgiants and red giants has been addressed only under the debated assumption of the Tayler-Spruit dynamo in radiative interi-ors (Spruit 2002), and its revision based on a different saturation process by Fuller et al (2019). Comparisons with asteroseismic measurements have shown that this process is currently unable to correctly account for the internal rotation of subgiants and red giants (Cantiello et al 2014, den Hartogh et al 2019, Eggenberger et al 2019b, den Hartogh et al 2020.…”

Section: Introductionmentioning

confidence: 99%

Seismic evidence for near solid-body rotation in two Kepler subgiants and implications for angular momentum transport

Deheuvels

Ballot

Eggenberger

et al. 2020

A&A

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Context. Asteroseismic measurements of the internal rotation of subgiants and red giants all show the need for invoking a more efficient transport of angular momentum than theoretically predicted. Constraints on the core rotation rate are available starting from the base of the red giant branch (RGB) and we are still lacking information on the internal rotation of less evolved subgiants. Aims. We identify two young Kepler subgiants, KIC8524425 and KIC5955122, whose mixed modes are clearly split by rotation. We aim to probe their internal rotation profile and assess the efficiency of the angular momentum transport during this phase of the evolution. Methods. Using the full Kepler data set, we extracted the mode frequencies and rotational splittings for the two stars using a Bayesian approach. We then performed a detailed seismic modeling of both targets and used the rotational kernels to invert their internal rotation profiles using the MOLA inversion method. We thus obtained estimates of the average rotation rates in the g-mode cavity (Ω g) and in the p-mode cavity (Ω p). Results. We found that both stars are rotating nearly as solid bodies, with core-envelope contrasts of Ω g/ Ω p = 0.68 ± 0.47 for KIC8524425 and Ω g/ Ω p = 0.72 ± 0.37 for KIC5955122. This result shows that the internal transport of angular momentum has to occur faster than the timescale at which differential rotation is forced in these stars (between 300 Myr and 600 Myr). By modeling the additional transport of angular momentum as a diffusive process with a constant viscosity ν add , we found that values of ν add > 5 × 10 4 cm 2 .s −1 are required to account for the internal rotation of KIC8524425, and ν add > 1.5 × 10 5 cm 2 .s −1 for KIC5955122. These values are lower than or comparable to the efficiency of the core-envelope coupling during the main sequence, as given by the surface rotation of stars in open clusters. On the other hand, they are higher than the viscosity needed to reproduce the rotation of subgiants near the base of the RGB. Conclusions. Our results yield further evidence that the efficiency of the internal redistribution of angular momentum decreases during the subgiant phase. We thus bring new constraints that will need to be accounted for by mechanisms that are proposed as candidates for angular momentum transport in subgiants and red giants.

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“…These models that account for rotational and magnetic effects are able to correctly reproduce the internal rotation of the Sun together with the observations of surface velocities of stars in open clusters (Eggenberger et al 2005(Eggenberger et al , 2019a. However, we note that the same models do not provide sufficient coupling to correctly reproduce the asteroseismic core rotation rates of red giants (Cantiello et al 2014;den Hartogh et al 2019), which indicates that an unknown efficient additional AM transport process is needed for subgiant (Eggenberger et al 2019b) and red giant stars (Eggenberger et al 2012(Eggenberger et al , 2017.…”

Section: Orbital Historymentioning

confidence: 72%

Coralie radial-velocity search for companions around evolved stars (CASCADES) III. A new Jupiter host-star: in-depth analysis of HD 29399 using TESS data

Pezzotti,

Ottoni,

Buldgen

et al. 2022

Preprint

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Context. Increasing the number of detected exoplanets is far from anecdotal, especially for long-period planets that require a long duration of observation. More detections imply a better understanding of the statistical properties of exoplanet populations, and detailed modelling of their host stars also enables thorough discussions of star-planet interactions and orbital evolution of planetary systems. Aims. In the context of the discovery of a new planetary system, we aim to perform a complete study of HD 29399 and its companion by means of radial-velocity measurements, seismic characterisation of the host-star, and modelling of the orbital evolution of the system. Methods. High-resolution spectra of HD 29399 were acquired with the CORALIE spectrograph mounted on the 1.2-m Swiss telescope located at La Silla Observatory (Chile) as part of the CASCADES survey. We used the moments of the cross-correlation function profile as well as the photometric variability of the star as diagnostics to distinguish between stellar and planetary-induced signals. To model the host star we combined forward modelling with global and local minimisation approaches and inversion techniques. We also studied the orbital history of the system under the effects of both dynamical and equilibrium tides. Results. We present the detection of a long-period giant planet. Combining these measurements with photometric observations by TESS, we are able to thoroughly model the host star and study the orbital evolution of the system. We derive stellar and planetary masses of 1.17 ± 0.10 M and 1.59 ± 0.08 M Jup , respectively, and an age for the system of 6.2 Gyr. We show that neither dynamical nor equilibrium tides have been able to affect the orbital evolution of the planet. Moreover, no engulfment is predicted for the future evolution of the system.

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Constraining transport of angular momentum in stars

Cited by 28 publications

References 48 publications

Core–Envelope Coupling in Intermediate-mass Core-helium Burning Stars

Core–Envelope Coupling in Intermediate-mass Core-helium Burning Stars

Seismic evidence for near solid-body rotation in two Kepler subgiants and implications for angular momentum transport

Coralie radial-velocity search for companions around evolved stars (CASCADES) III. A new Jupiter host-star: in-depth analysis of HD 29399 using TESS data

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