K Dwarf Radius Inflation and a 10 Gyr Spin-down Clock Unveiled through Asteroseismology of HD 219134 from the Keck Planet Finder

Creators: Li 李, Yaguang 亚光¹; Huber, Daniel¹; Ong 王, J. M. Joel 加冕¹; van Saders, Jennifer¹; Costa, R. R.²; Larsen, Jens Reersted³; Basu, Sarbani⁴; Bedding, Timothy R.⁵; Dai 戴, Fei 飞¹; Chontos, Ashley⁶; Carmichael, Theron W.¹; Hey, Daniel¹; Kjeldsen, Hans³; Hon, Marc⁷; Campante, Tiago L.²; Monteiro, Mário J. P. F. G.²; Lundkvist, Mia Sloth³; Saunders, Nicholas¹; Isaacson, Howard⁸; Howard, Andrew W.⁹; Gibson, Steven R.⁹; Halverson, Samuel¹⁰; Rider, Kodi⁸; Roy, Arpita¹¹; Baker, Ashley D.⁹; Edelstein, Jerry⁸; Smith, Chris⁸; Fulton, Benjamin J.⁹; Walawender, Josh¹²

1. University of Hawaii at Manoa
2. University of Porto
3. Aarhus University
4. Yale University
5. University of Sydney
6. Princeton University
7. Massachusetts Institute of Technology
8. University of California, Berkeley
9. California Institute of Technology
10. Jet Propulsion Lab
11. Schmidt Sciences
12. W.M. Keck Observatory

Abstract

We present the first asteroseismic analysis of the K3 V planet host HD 219134 based on four consecutive nights of radial velocities collected with the Keck Planet Finder. We apply Gold deconvolution to the power spectrum to disentangle modes from side lobes in the spectral window and extract 25 mode frequencies with spherical degrees 0 ≤ ℓ ≤ 3. We derive the fundamental properties using five different evolutionary-modeling pipelines and report a mass of 0.763 ± 0.020 (stat) ± 0.007 (sys) M_⊙, a radius of 0.748 ± 0.007 (stat) ± 0.002 (sys) R_⊙, and an age of 10.151 ± 1.520 (stat) ± 0.810 (sys) Gyr. Compared to the interferometric radius 0.783 ± 0.005 R_⊙, the asteroseismic radius is 4% smaller at the 4σ level—a discrepancy not easily explained by known interferometric systematics, modeling assumptions on atmospheric boundary conditions and mixing lengths, magnetic fields, or tidal heating. HD 219134 is the first main-sequence star cooler than 5000 K with an asteroseismic age estimate and will serve as a critical calibration point for stellar spin-down relations. We show that existing calibrated prescriptions for angular momentum loss, incorporating weakened magnetic braking with asteroseismically constrained stellar parameters, accurately reproduce the observed rotation period. Additionally, we revised the masses and radii of the super-Earths in the system, which support their having Earth-like compositions. Finally, we confirm that the oscillation amplitude in radial velocity scales as (L/M)^1.5 in K dwarfs, in contrast to the (L/M)^0.7 relation observed in G dwarfs. These findings provide significant insights into the structure and angular momentum loss of K-type stars.

Copyright and License

Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

Acknowledgement

The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Y.L. acknowledges support from the Beatrice Watson Parrent Fellowship and a NASA Keck PI Data Award, which is administered by the NASA Exoplanet Science Institute. Data presented herein were obtained at the W. M. Keck Observatory from telescope time allocated to the National Aeronautics and Space Administration through the agency's scientific partnership with the California Institute of Technology and the University of California. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. D.H. acknowledges support from the Alfred P. Sloan Foundation, the National Aeronautics and Space Administration (80NSSC22K0781), and the Australian Research Council (FT200100871). J.M.J.O. acknowledges support from NASA through the NASA Hubble Fellowship grant HST-HF2-51517.001, awarded by STScI. STScI is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. T.R.B. acknowledges support from the Australian Research Council through Laureate Fellowship FL220100117. T.L.C. is supported by Fundação para a Ciência e a Tecnologia (FCT) in the form of a work contract (CEECIND/00476/2018). M.S.L. is supported by a research grant (42101) from VILLUM FONDEN. N.S. acknowledges support by the National Science Foundation Graduate Research Fellowship Program under grant Nos. 1842402 and 2236415 and NASA's Interdisciplinary Consortia for Astrobiology Research (NNH19ZDA001N-ICAR) under award number 19-ICAR19 2-0041. We thank the reviewer for helpful comments.

Files

Li_2025_ApJ_984_125.pdf

Files (1.9 MB)

Name	Size	Download all
Li_2025_ApJ_984_125.pdf md5:f6ac7e7a8f4c80c23ce4be79d6febef7	1.9 MB	Preview Download

Additional details

	All versions	This version
Views	0	0
Downloads	0	0
Data volume	0 Bytes	0 Bytes