Searches for Exoplanetary Radio Emission

Analogous to the Earth and Jupiter in our solar system, magnetized exoplanets are expected to emit intense bursts of coherent radio waves via the electron cyclotron maser (ECM) instability. This mechanism produces narrow-band, up to 100% circularly polarized radiation close to the local electron cyclotron frequency and its harmonics. Detections of exoplanetary ECM emission, therefore, enable one to estimate planetary magnetic field strengths and assess their role in influencing planetary habitability. However, a conclusive detection of exoplanetary ECM emission still eludes us, despite over two decades of extensive searches.

As part of a comprehensive survey of stellar systems for exoplanet-associated ECM emission, Bastian et al. (2018) serendiptously detected a 5-minute-long, 1 mJy flare at 2—4 GHz from the nearby K2V star ε Eridani. Though the spectral properties of this flare favor a stellar origin, its ~ 3 AU separation from ε Eridani raises the possibility of a non-stellar provenance.

To localize any flare recurrences and conclusively identify their physical origin, we conducted deep 2—4 GHz observations of ε Eridani with the Very Large Array in its most extended configuration. Our observations represent the first detection of 2—4 GHz quiescent continuum emission from ε Eridani. We also report a non-detection of flares in our data above a 5σ threshold of 95 μJy.

PSR J1745—2900
An artistic depiction of super-Alfvénic star-planet interactions.
Image credit: NASA

Related Publications:

  1. Suresh, A., Chatterjee, S., Cordes, J. M., Bastian, T. S. & Hallinan, G., "Detection of 2—4 GHz Continuum Emission from ε Eridani", ApJ 904, 138, 2020. [ADS]