Evaluating Star–Planet Interactions with Zeeman Doppler Imaging: Case Study in YZ Ceti

The Astrophysical Journal, vol. 997, pp. 172

Abstract

Abstract The recent detections of radio emission from the nearby exoplanet host, YZ Ceti, suggest that the star is possibly interacting with its rocky innermost planet. These radio emissions are characterized by strong circular polarization, and appear to repeat within consistent orbital phase windows dictated by the orbital position of YZ Ceti b. If confirmed, this interaction would provide a first means to concretely assess the magnetic field of a close-in rocky exoplanet. This kind of magnetic star–planet interaction (SPI) should depend on both the exoplanetary orbit and the geometry of the stellar magnetic field. In this article, we report measurements of the large-scale magnetic field topology of the star YZ Ceti for the first time, and interpret the cumulative radio data sets in that context to evaluate the plausibility of magnetic SPIs. We find evidence both against and in support of the SPI hypothesis, but crucially that the measured magnetic field does not rule out SPI scenarios. However, clear evaluation of these possibilities requires more accurate assessments of the magnetic field evolution across time. We additionally suggest that YZ Ceti may be exhibiting planet-induced flaring, potentially triggered by exoplanet crossings of the Alfvén surface as the planet’s orbit approaches the stellar magnetic equator, and YZ Ceti b experiences dramatic shifts in the ambient field, its polarity, and connectivity to the host star.

Authors 6

1. J. Sebastian Pineda corresponding

   University of Colorado Boulder · Laboratory for Atmospheric and Space Physics

   Affiliation as printed

   University of Colorado Boulder, Laboratory for Atmospheric and Space Physics, 3665 Discovery Drive, Boulder, CO 80303, USA; sebastian.pineda@lasp.colorado.edu

2. S. Bellotti Aachen Leiden Observatory

   Leiden University · Centre National de la Recherche Scientifique · Institut de Recherche en Astrophysique et Planétologie · Leiden Observatory · Université de Toulouse

   Affiliation as printed

   Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, CNRS, IRAP/UMR 5277, 14 avenue Edouard Belin, F-31400, Toulouse, France

   Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands

3. Jackie Villadsen

   Bucknell University

   Affiliation as printed

   Bucknell University, One Dent Drive, Lewisburg, PA 17837, USA

4. A. A. Vidotto Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands

5. J. Morin

   Centre National de la Recherche Scientifique · Université de Montpellier · Laboratoire Univers et Particules de Montpellier

   Affiliation as printed

   Laboratoire Univers et Particules de Montpellier, Université de Montpellier, CNRS, F-34095, Montpellier, France

6. C. P. Folsom

   Tartu Observatory · University of Tartu

   Affiliation as printed

   Tartu Observatory, University of Tartu, Observatooriumi 1, 61602, Toravere, Estonia