Constraining the Rotation Profile in a Low-Luminosity Subgiant with a Surface Rotation Measurement

Abstract

Rotationally-induced mode splitting frequencies of low-luminosity subgiants suggest that angular momentum transport mechanisms are 1-2 orders of magnitude more efficient in these stars than predicted by theory. Constraints on the rotation profile of low-luminosity subgiants could be used to identify the dominant mechanism for angular momentum transport. We develop a forward model for the rotation profile given observed rotational splittings, assuming a step-like rotation profile. We identify a consistent degeneracy between the position of the profile discontinuity and the surface rotation rate. We perform mock experiments that show the discontinuity position can be better constrained with a prior on the surface rotation rate, which is informed by star spot modulations. We finally apply this approach to KIC 12508433, a well-studied low-luminosity subgiant, as an example case. With the observed surface rotation prior, we obtain a factor of two increase in precision of the position of strong rotation gradient. We recover the literature values of the core and surface rotation rates and find the highest support for a discontinuity in the radiative zone. Auxiliary measurements of surface rotation could substantially improve inferences on the rotation profile of low-luminosity subgiants with already available data.

arXiv comment9 pages, 11 figures, 2 table

References in corpus (40)

• Modules for Experiments in Stellar Astrophysics (MESA)
• Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
• Modules for Experiments in Stellar Astrophysics (MESA): Binaries, Pulsations, and Explosions
• The No-U-Turn Sampler: Adaptively Setting Path Lengths in Hamiltonian Monte Carlo
• Modules for Experiments in Stellar Astrophysics (MESA): Pulsating Variable Stars, Rotation, Convective Boundaries, and Energy Conservation
• The evolution of rotating stars
• Rotation Periods of 34,030 Kepler Main-Sequence Stars: The Full Autocorrelation Sample
• An absolutely calibrated effective temperature scale from the InfraRed Flux Method
• ADIPLS -- the Aarhus adiabatic oscillation package
• Influence of gravity waves on the internal rotation and Li abundance of solar-type stars
• Seismic constraints on the radial dependence of the internal rotation profiles of six Kepler subgiants and young red giants
• Seismic diagnostics for transport of angular momentum in stars 1. Rotational splittings from the PMS to the RGB
• Angular momentum transport within evolved low-mass stars
• Rotation and magnetism of Kepler pulsating solar-like stars. Towards asteroseismically calibrated age-rotation relations
• A new correction of stellar oscillation frequencies for near-surface effects
• Angular momentum transport in stellar interiors constrained by rotational splittings of mixed modes in red giants
• Asteroseismology Can Reveal Strong Internal Magnetic Fields in Red Giant Stars
• Seismic evidence for a weak radial differential rotation in intermediate-mass core helium burning stars
• Core rotation braking on the red giant branch for various mass ranges
• Surface rotation and photometric activity for Kepler targets. II. G and F main-sequence stars, and cool subgiant stars
• Understanding angular momentum transport in red giants: the case of KIC 7341231
• Magnetic confinement of the solar tachocline: II. Coupling to a convection zone
• Angular momentum transport efficiency in post-main sequence low-mass stars
• Can plume-induced internal gravity waves regulate the core rotation of subgiant stars?
• Seismic evidence for near solid-body rotation in two Kepler subgiants and implications for angular momentum transport
• Modeling of Magneto-Rotational Stellar Evolution I. Method and first applications
• Asteroseismology of evolved stars to constrain the internal transport of angular momentum. I. Efficiency of transport during the subgiant phase
• Properties of oscillation modes in subgiant stars observed by Kepler
• Surface-effect corrections for oscillation frequencies of evolved stars
• Rotation of Giant Stars
• A deep test of radial differential rotation in a helium-atmosphere white dwarf: I. Discovery of pulsations in PG 0112+104
• Asteroseismology of 36 \emph{Kepler} subgiants -- I. Oscillation frequencies, linewidths and amplitudes
• The rotational shear layer inside the early red-giant star KIC 4448777
• Probing core overshooting using subgiant asteroseismology: the case of KIC10273246
• On rotationally driven meridional flows in stars
• Differential rotation decay in the radiative envelopes of CP stars
• Asteroseismology of evolved stars to constrain the internal transport of angular momentum. IV. Internal rotation of Kepler 56 from an MCMC analysis of the rotational splittings
• Asteroseismic inversions for radial differential rotation of Sun-like stars: Sensitivity to uncertainties
• Some glimpses from helioseismology at the dynamics of the deep solar interior
• Magneto-Rotational Transport in the Early Sun