The Death of Vulcan: NEID Reveals That the Planet Candidate Orbiting HD 26965 Is Stellar Activity

Abigail Burrows; Samuel Halverson; Jared C. Siegel; Christian Gilbertson; Jacob Luhn; Jennifer Burt; Chad F. Bender; Arpita Roy; Ryan C. Terrien; Selma Vangstein; Suvrath Mahadevan; Jason T. Wright; Paul Robertson; Eric B. Ford; Gumundur Stefánsson; Joe P. Ninan; Cullen H. Blake; Michael W. McElwain; Christian Schwab; Jinglin Zhao

doi:10.3847/1538-3881/ad34d5

The Astronomical Journal (Jan 2024)

The Death of Vulcan: NEID Reveals That the Planet Candidate Orbiting HD 26965 Is Stellar Activity

Abigail Burrows,
Samuel Halverson,
Jared C. Siegel,
Christian Gilbertson,
Jacob Luhn,
Jennifer Burt,
Chad F. Bender,
Arpita Roy,
Ryan C. Terrien,
Selma Vangstein,
Suvrath Mahadevan,
Jason T. Wright,
Paul Robertson,
Eric B. Ford,
Gumundur Stefánsson,
Joe P. Ninan,
Cullen H. Blake,
Michael W. McElwain,
Christian Schwab,
Jinglin Zhao

Affiliations

Abigail Burrows: ORCiD; Department of Physics and Astronomy, Dartmouth College , Hanover, NH 03755, USA; Jet Propulsion Laboratory, California Institute of Technology , 4800 Oak Grove Drive, Pasadena, CA 91109, USA
Samuel Halverson: ORCiD; Jet Propulsion Laboratory, California Institute of Technology , 4800 Oak Grove Drive, Pasadena, CA 91109, USA
Jared C. Siegel: ORCiD; Department of Astrophysical Sciences, Princeton University , 4 Ivy Lane, Princeton, NJ 08540, USA
Christian Gilbertson: ORCiD; Center for Computing Research, Sandia National Laboratories , Albuquerque, NM 87185, USA; Department of Astronomy & Astrophysics, 525 Davey Laboratory, The Pennsylvania State University , University Park, PA 16802, USA; Center for Exoplanets and Habitable Worlds, 525 Davey Laboratory, The Pennsylvania State University , University Park, PA 16802, USA
Jacob Luhn: ORCiD; Department of Physics & Astronomy, The University of California , Irvine, CA 92697, USA
Jennifer Burt: ORCiD; Jet Propulsion Laboratory, California Institute of Technology , 4800 Oak Grove Drive, Pasadena, CA 91109, USA
Chad F. Bender: ORCiD; Steward Observatory, University of Arizona , 933 N. Cherry Avenue, Tucson, AZ 85721, USA
Arpita Roy: ORCiD; Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USA; Department of Physics and Astronomy, Johns Hopkins University , 3400 N. Charles Street, Baltimore, MD 21218, USA
Ryan C. Terrien: ORCiD; Carleton College , One North College Street, Northfield, MN 55057, USA
Selma Vangstein: ORCiD; Carleton College , One North College Street, Northfield, MN 55057, USA
Suvrath Mahadevan: ORCiD; Department of Astronomy & Astrophysics, 525 Davey Laboratory, The Pennsylvania State University , University Park, PA 16802, USA; Center for Exoplanets and Habitable Worlds, 525 Davey Laboratory, The Pennsylvania State University , University Park, PA 16802, USA
Jason T. Wright: ORCiD; Department of Astronomy & Astrophysics, 525 Davey Laboratory, The Pennsylvania State University , University Park, PA 16802, USA; Center for Exoplanets and Habitable Worlds, 525 Davey Laboratory, The Pennsylvania State University , University Park, PA 16802, USA; Penn State Extraterrestrial Intelligence Center, 525 Davey Laboratory, The Pennsylvania State University , University Park, PA 16802, USA
Paul Robertson: ORCiD; Department of Physics & Astronomy, The University of California , Irvine, CA 92697, USA
Eric B. Ford: ORCiD; Department of Astronomy & Astrophysics, 525 Davey Laboratory, The Pennsylvania State University , University Park, PA 16802, USA; Center for Exoplanets and Habitable Worlds, 525 Davey Laboratory, The Pennsylvania State University , University Park, PA 16802, USA; Institute for Computational and Data Sciences, The Pennsylvania State University , University Park, PA 16802, USA; Center for Astrostatistics, 525 Davey Laboratory, The Pennsylvania State University , University Park, PA 16802, USA
Gumundur Stefánsson: ORCiD; Department of Astrophysical Sciences, Princeton University , 4 Ivy Lane, Princeton, NJ 08540, USA
Joe P. Ninan: ORCiD; Department of Astronomy & Astrophysics, 525 Davey Laboratory, The Pennsylvania State University , University Park, PA 16802, USA; Center for Exoplanets and Habitable Worlds, 525 Davey Laboratory, The Pennsylvania State University , University Park, PA 16802, USA
Cullen H. Blake: ORCiD; Department of Physics and Astronomy, University of Pennsylvania , 209 S. 33rd Street, Philadelphia, PA 19104, USA
Michael W. McElwain: ORCiD; Exoplanets and Stellar Astrophysics Laboratory , NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA
Christian Schwab: ORCiD; School of Mathematical and Physical Sciences, Macquarie University , Balaclava Road, North Ryde, NSW 2109, Australia
Jinglin Zhao: ORCiD; Department of Astronomy & Astrophysics, 525 Davey Laboratory, The Pennsylvania State University , University Park, PA 16802, USA

DOI: https://doi.org/10.3847/1538-3881/ad34d5
Journal volume & issue: Vol. 167, no. 5
p. 243

Abstract

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We revisit the long-studied radial velocity (RV) target HD 26965 using recent observations from the NASA-NSF “NEID” precision Doppler facility. Leveraging a suite of classical activity indicators, combined with line-by-line RV analyses, we demonstrate that the claimed 45-day signal previously identified as a planet candidate is most likely an activity-induced signal. Correlating the bulk (spectrally averaged) RV with canonical line activity indicators confirms a multiday “lag” between the observed activity indicator time series and the measured RV. When accounting for this lag, we show that much of the observed RV signal can be removed by a linear detrending of the data. Investigating activity at the line-by-line level, we find a depth-dependent correlation between individual line RVs and the bulk RVs, further indicative of periodic suppression of convective blueshift causing the observed RV variability, rather than an orbiting planet. We conclude that the combined evidence of the activity correlations and depth dependence is consistent with an RV signature dominated by a rotationally modulated activity signal at a period of ∼42 days. We hypothesize that this activity signature is due to a combination of spots and convective blueshift suppression. The tools applied in our analysis are broadly applicable to other stars and could help paint a more comprehensive picture of the manifestations of stellar activity in future Doppler RV surveys.

Radial velocity

Published in The Astronomical Journal

ISSN: 0004-6256 (Print); 1538-3881 (Online)
Publisher: IOP Publishing
Country of publisher: United Kingdom
LCC subjects: Science: Astronomy
Website: https://iopscience.iop.org/journal/1538-3881

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