A Deep Radio Limit for the TRAPPIST-1 System

Abstract

The first nearby very-low mass star planet-host discovered, TRAPPIST-1, presents not only a unique opportunity for studying a system of multiple terrestrial planets, but a means to probe magnetospheric interactions between a star at the end of the main sequence and its close-in satellites. This encompasses both the possibility of persistent coronal solar-like activity, despite cool atmospheric temperatures, and the presence of large-scale magnetospheric currents, similar to what is seen in the Jovian system. Significantly, the current systems include a crucial role for close-in planetary satellites analogous to the role played by the Galilean satellites around Jupiter. We present the first radio observations of the seven-planet TRAPPIST-1 system using the Karl G. Jansky Very Large Array, looking for both highly circularly polarized radio emission and/or persistent quiescent emissions. We measure a broadband upper flux density limit of <8.1 $\mu$Jy across 4-8 GHz, and place these observations both in the context of expectations for stellar radio emission, and the possible electrodynamic engines driving strong radio emissions in very-low mass stars and brown dwarfs, with implications for future radio surveys of TRAPPIST-1 like planet-hosts. We conclude that magnetic activity of TRAPPIST-1 is predominantly coronal and does not behave like the strong radio emitters at the stellar/sub-stellar boundary. We further discuss the potential importance of magnetic field topology and rotation rates, demonstrating that a TRAPPIST-1 like planetary system around a rapidly rotating very-low mass star can generate emission consistent with the observed radio luminosities of very-low mass stars and brown dwarfs.

9 pages, accepted by AAS Journals

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Cited by in corpus (11)

• Coherent radio bursts from known M-dwarf planet host YZ Ceti
• Resolved imaging of an extrasolar radiation belt around an ultracool dwarf
• Time-variable electromagnetic star-planet interaction: The TRAPPIST-1 system as an exemplary case
• Radio Stars: from kHz to THz
• The Habitable-zone Planet Finder Detects a Terrestrial-mass Planet Candidate Closely Orbiting Gliese 1151: The Likely Source of Coherent Low-frequency Radio Emission from an Inactive Star
• No Massive Companion to the Coherent Radio-Emitting M Dwarf GJ 1151
• On the Correlation between L Dwarf Optical and Infrared Variability and Radio Aurorae
• The Occurrence Rate of Quiescent Radio Emission for Ultracool Dwarfs using a Generalized Semi-Analytical Bayesian Framework
• Transitions in magnetic behavior at the substellar boundary
• Constraining the Radio Emission of TRAPPIST-1
• Upper Limits on Planet-Induced GHz Radio Emission from Inactive M Dwarfs