The ultracool dwarf (UCD) TRAPPIST-1 is close to Earth (~12 pc) and possesses several Earth-sized terrestrial planets, making it a compelling target for exoplanet characterization. TRAPPIST-1 is an active M8V star with frequent flaring, as is typical of UCDs. UCDs have been observed to undergo particularly extreme outbursts known as superflares; a superflare from Proxima Cen b, for example, was recently observed by the Evryscope team. Superflares can render planets uninhabitable primarily by two processes. They may erode a planet's atmosphere over long timescales, or destroy atmospheric volatiles such as ozone over geologically short timescales. Both UV flux and particle bombardment play roles in these processes. If TRAPPIST-1 is subject to frequent superflares, the habitability of its planets may be severely impacted. As yet, only one 1033-erg event has been observed from TRAPPIST-1; the occurrence rate for higher-energy superflares remains unknown. The Evryscope at CTIO observes the entire southern sky at a two-minute cadence, and is thus especially well suited to characterize the superflare occurrence rate for ultracool dwarves such as TRAPPIST-1. Particle bombardment can be probed by radio observations: Strong gyrosynchrotron radiation is indicative of ~MeV particles being injected into the stellar environment, which can erode the atmosphere of close-orbiting planets. Hence, simultaneous radio observations from the Very Large Array (VLA) can further inform habitability considerations by showing whether optical flares are accompanied by radio-emitting processes, such as gyrosynchrotron emission or the electron cyclotron maser instability. Pairing Evryscope optical observations with VLA radio observations constrains the flare occurrence rate for TRAPPIST-1 and provides information on the habitability of its planets. We present here the preliminary results of this analysis.
American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019