The search for radio emission from exoplanets using LOFAR low-frequency beamformed observations

The detection of radio emissions from exoplanets will open up a vibrant new research field. Observing planetary auroral radio emissions is the most promising method to detect exoplanetary magnetic fields, the knowledge of which will provide valuable insights into the planet's interior structure, atmospheric escape, and habitability.  To date, many ground-based observations conducted to find exoplanet radio emissions have resulted in non-detections. 

Here, we present our recent study using Low Frequency Array (LOFAR) circularly polarized beamformed observations of the three exoplanetary systems 55 Cnc, Upsilon Andromedae, and Tau Bootis.  All three systems are predicted to be ideal candidates to search for radio emission. 

For the Tau Bootis system, we tentatively detected circularly polarized bursty emissions from 14 - 21 Mhz at 3 sigma and slowly variable circularly polarized emissions from 21 - 30 Mhz at 8 sigma.  We will discuss in detail all the arguments for and against an actual detection. 

Furthmore, no signals are detected from the 55 Cancri and Upsilon Andromedae systems.  Assuming the detected signals are real, we discuss their potential origin.  Their source probably is the Tau Bootis planetary system, and a possitlbe explanation is radio emission from the exoplanet Tau Bootis b via the cyclotron maser mechanism. 

Assuming a planetary origin, we derived limits for the planetary polar surface magnetic field strength, finding values compatible with theoretical predictions.  Follow-up observations are ongoing with LOFAR and other low-frequency telescopes to confirm this possible first detection of an exoplanetary radio signal.  We will also briefly discuss the first results from these follow-up observations.

Speaker: Jake Turner, Cornell