• DOI:10.3847/1538-3881/ac0057
• Corpus ID: 234741985

Stellar Activity Manifesting at a One-year Alias Explains Barnard b as a False Positive

@article{Lubin2021StellarAM,
  title={Stellar Activity Manifesting at a One-year Alias Explains Barnard b as a False Positive},
  author={Jack Lubin and Paul Robertson and Gudmundur Stef{\'a}nsson and Joe P. Ninan and Suvrath Mahadevan and Michael Endl and Eric B. Ford and Jason T. Wright and Corey Beard and Chad F. Bender and William D. Cochran and Scott A. Diddams and Connor Fredrick and Samuel Halverson and Shubham Kanodia and Andrew J. Metcalf and Lawrence W. Ramsey and Arpita Roy and Christian Schwab and Ryan C. Terrien},
  journal={The Astronomical Journal},
  year={2021},
  volume={162}
}

• J. Lubin, P. Robertson, +17 authors R. Terrien
• Published 14 May 2021
• Physics, Geology
• The Astronomical Journal

Barnard’s star is among the most studied stars given its proximity to the Sun. It is often considered the radial velocity (RV) standard for fully convective stars due to its RV stability and equatorial decl. Recently, an Msini=3.3M⊕ super-Earth planet candidate with a 233 day orbital period was announced by Ribas et al. New observations from the near-infrared Habitable-zone Planet Finder (HPF) Doppler spectrometer do not show this planetary signal. We ran a suite of experiments on both the original data and a combined original + HPF data set. These experiments include model comparisons, periodogram analyses, and sampling sensitivity, all of which show the signal at the proposed period of 233 days is transitory in nature. The power in the signal is largely contained within 211 RVs that were taken within a 1000 day span of observing. Our preferred model of the system is one that features stellar activity without a planet. We propose that the candidate planetary signal is an alias of the 145 day rotation period. This result highlights the challenge of analyzing long-term, quasi-periodic activity signals over multiyear and multi-instrument observing campaigns.