The space weather around the exoplanet GJ 436b
S. Bellotti, R. Fares, A. A. Vidotto, J. Morin, P. Petit, G. A. J., Hussain, V. Bourrier, J.F. Donati, C. Moutou, E. Hebrard

TL;DR
This study characterizes the magnetic environment of the exoplanet host star GJ 436 using spectropolarimetry, revealing a predominantly poloidal, dipolar magnetic field and providing insights into star-planet interactions affecting planetary atmospheres.
Contribution
The paper applies spectropolarimetric techniques to map GJ 436's magnetic field, offering new detailed magnetic topology data for this star and its implications for exoplanet atmospheric evolution.
Findings
Average longitudinal magnetic field of -12 G
Stellar rotation period of ~46 days
Magnetic field is mainly poloidal and dipolar
Abstract
The space environment in which planets are embedded depends mainly on the host star and impacts the evolution of the planetary atmosphere. The quiet M dwarf GJ 436 hosts a close-in hot Neptune which is known to feature a comet-like tail of hydrogen atoms escaped from its atmosphere due to energetic stellar irradiation. Understanding such star-planet interactions is essential to shed more light on planet formation and evolution theories, in particular the scarcity of Neptune-size planets below 3 d orbital period, also known as ``Neptune desert''. We aimed at characterising the stellar environment around GJ 436, which requires an accurate knowledge of the stellar magnetic field. The latter is studied efficiently with spectropolarimetry, since it is possible to recover the geometry of the large-scale magnetic field by applying tomographic inversion on time series of circularly polarised…
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Taxonomy
TopicsAstro and Planetary Science · Stellar, planetary, and galactic studies · Astronomical and nuclear sciences
