The Astrophysical Journal (Jan 2022)

Spinning up the Surface: Evidence for Planetary Engulfment or Unexpected Angular Momentum Transport?

  • Jamie Tayar,
  • Facundo D. Moyano,
  • Melinda Soares-Furtado,
  • Ana Escorza,
  • Meridith Joyce,
  • Sarah L. Martell,
  • Rafael A. García,
  • Sylvain N. Breton,
  • Stéphane Mathis,
  • Savita Mathur,
  • Vincent Delsanti,
  • Sven Kiefer,
  • Sabine Reffert,
  • Dominic M. Bowman,
  • Timothy Van Reeth,
  • Shreeya Shetye,
  • Charlotte Gehan,
  • Samuel K. Grunblatt

DOI
https://doi.org/10.3847/1538-4357/ac9312
Journal volume & issue
Vol. 940, no. 1
p. 23

Abstract

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In this paper, we report the potential detection of a nonmonotonic radial rotation profile in a low-mass lower-luminosity giant star. For most low- and intermediate-mass stars, the rotation on the main sequence seems to be close to rigid. As these stars evolve into giants, the core contracts and the envelope expands, which should suggest a radial rotation profile with a fast core and a slower envelope and surface. KIC 9267654, however, seems to show a surface rotation rate that is faster than its bulk envelope rotation rate, in conflict with this simple angular momentum conservation argument. We improve the spectroscopic surface constraint, show that the pulsation frequencies are consistent with the previously published core and envelope rotation rates, and demonstrate that the star does not show strong chemical peculiarities. We discuss the evidence against any tidally interacting stellar companion. Finally, we discuss the possible origin of this unusual rotation profile, including the potential ingestion of a giant planet or unusual angular momentum transport by tidal inertial waves triggered by a close substellar companion, and encourage further observational and theoretical efforts.

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