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<p>Close companions influence stellar evolution through tidal interactions, mass transfer and mass-loss effects. While such companions are detected around young stellar objects, main-sequence stars, red giants and compact objects, direct observational evidence of close-in companions around asymptotic giant branch (AGB) stars has remained elusive. Here we present (sub)millimetre time-domain imaging spectroscopy revealing the Keplerian motion of a close-in companion around the AGB star π<sup>1</sup> Gruis. The companion, slightly more massive than the AGB star, is likely a main-sequence star. Unlike more evolved stars with companions at comparable distances, the companion of π<sup>1</sup> Gruis follows a circular orbit, suggesting an eccentricity-generating mechanism during the late- or post-AGB phase. Our analysis suggests that model-predicted circularization rates may be underestimated. Our results highlight the potential of multi-epoch (sub)millimetre interferometry in detecting the Keplerian motion of close companions to giant stars and open avenues for our understanding of tidal interaction physics and binary evolution.</p>

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Evidence for the Keplerian orbit of a close companion around a giant star

  • 期刊论文

  • 发表日期：

    2025年11月13日

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  • Mats Esseldeurs,
  • Leen Decin,
  • Joris De Ridder,
  • Yoshiya Mori,
  • Amanda I. Karakas,
  • Jolien Malfait,
  • Taíssa Danilovich,
  • Stéphane Mathis,
  • Anita M. S. Richards,
  • Raghvendra Sahai,
  • Jeremy Yates,
  • Marie Van de Sande,
  • Maarten Baes,
  • Alain Baudry,
  • Jan Bolte,
  • Thomas Ceulemans,
  • Frederik De Ceuster,
  • Ileyk El Mellah,
  • Sandra Etoka,
  • Carl Gottlieb,
  • Fabrice Herpin,
  • Pierre Kervella,
  • Camille Landri,
  • Louise Marinho,
  • Iain McDonald,
  • Karl Menten,
  • Tom Millar,
  • Zara Osborn,
  • Bannawit Pimpanuwat,
  • John Plane,
  • Daniel J. Price,
  • Lionel Siess,
  • Owen Vermeulen,
  • Ka Tat Wong

摘要

Close companions influence stellar evolution through tidal interactions, mass transfer and mass-loss effects. While such companions are detected around young stellar objects, main-sequence stars, red giants and compact objects, direct observational evidence of close-in companions around asymptotic giant branch (AGB) stars has remained elusive. Here we present (sub)millimetre time-domain imaging spectroscopy revealing the Keplerian motion of a close-in companion around the AGB star π1 Gruis. The companion, slightly more massive than the AGB star, is likely a main-sequence star. Unlike more evolved stars with companions at comparable distances, the companion of π1 Gruis follows a circular orbit, suggesting an eccentricity-generating mechanism during the late- or post-AGB phase. Our analysis suggests that model-predicted circularization rates may be underestimated. Our results highlight the potential of multi-epoch (sub)millimetre interferometry in detecting the Keplerian motion of close companions to giant stars and open avenues for our understanding of tidal interaction physics and binary evolution.