| Name: AYAN BISWAS |
| Affiliation: National Centre for Radio Astrophysics |
| Conference ID: ASI2026_1073 |
| Title: A Rapidly Evolving Stellar Magnetic Field in YZ Cet & Constraints on the Magnetosphere of Its Planet from Multi-wavelength Study |
| Abstract Type: Oral |
| Abstract Category: Stars, Interstellar Medium, and Astrochemistry in Milky Way |
| Author(s) and Co-Author(s) with Affiliation: Ayan Biswas(National Centre for Radio Astrophysics, Pune-411007, India), Colin P. Folsom(Tartu Observatory, Toravere- 61602, Estonia), James A. Barron(Queen’s University, Kingston-K7L 3N6, Canada), Gregg A. Wade(Royal Military College of Canada, Kingston-K7K 7B4, Canada) |
| Abstract: Magnetic fields are expected to play a central role in shaping the atmospheric evolution and potential habitability of exoplanets, particularly around M dwarfs. In the Solar System, all magnetized planets exhibit aurorae driven by interactions with the solar wind, producing intense polarized radio emission. We have recently detected similar auroral radio emission from the nearby M-dwarf system YZ Cet, modulated with the orbital phase of its innermost planet and interpreted as evidence of star-planet interaction. However, inferring the magnetic properties of the planet from these radio observations critically depends on the strength and geometry of the host star’s magnetic field. To address this, we present a spectropolarimetric study of YZ Cet based on near-infrared observations obtained with SPIRou at the Canada-France-Hawaii Telescope, combined with archival data. We report the discovery of a remarkably rapid evolution of the star’s large-scale magnetic field, with substantial changes in both field strength and topology occurring over only a few stellar rotation cycles. Using Zeeman Doppler Imaging, we reconstruct surface magnetic maps at multiple epochs and reveal a dramatic reconfiguration of the global field, including a transition toward a stronger, more dipole-dominated and highly non-axisymmetric geometry. By linking these magnetic maps with previously reported low-frequency radio detections from the system, we refine constraints on the magnetic field of the innermost planet. Our results demonstrate that short-term stellar magnetic variability can strongly influence interpretations of radio signatures of star-planet interaction. This work highlights the need for coordinated spectropolarimetric and radio monitoring to robustly characterize exoplanet magnetospheres and their space-weather environments. |
