Follow-up LOFAR observations of the $\tau$ Bo\"{o}tis exoplanetary system

TL;DR

Follow-up LOFAR observations of the $ au$ Bo"{o}tis exoplanetary system aimed to confirm previous tentative radio emission detections, but no signals were observed, highlighting the need for further multi-site and ancillary data.

Contribution

This study provides the first follow-up observations of $ au$ Boo with LOFAR covering 70% of the orbital period to verify prior tentative radio detections.

Findings

No bursty or slow radio emission detected in follow-up observations.

Results suggest previous signals may have been instrumental artifacts or due to stellar variability.

Highlights the necessity for multi-site and ancillary observations for confirmation.

Abstract

Context. Observing the radio emission from exoplanets is among the most promising methods to detect their magnetic fields and a measurement of an exoplanetary magnetic field will help constrain the planet's interior structure, star-planet interactions, atmospheric escape and dynamics, and habitability. Recently, circularly polarized bursty and slow emission from the $\tau$ Bo\"{o}tis ($\tau$ Boo) exoplanetary system was tentatively detected using LOFAR (LOW-Frequency ARray) beamformed observations. If confirmed, this detection will be a major contribution to exoplanet science. However, follow-up observations are required to confirm this detection. Aims. Here, we present such follow-up observations of the $\tau$ Boo system using LOFAR. These observations cover 70$\%$ of the orbital period of $\tau$ Boo b including the orbital phases of the previous tentative detections. Methods. We used the BOREALIS pipeline to mitigate radio frequency interference and to search for bursty and slowing varying radio signals. BOREALIS was previously used to find the tentative radio signals from $\tau$ Boo. Results. Our new observations do not show any signs of bursty or slow emission from the $\tau$ Bo\"{o}tis exoplanetary system. Conclusions. The cause for our non-detection is currently degenerate. It is possible that the tentative radio signals were an unknown instrumental systematic or that we are observing variability in the planetary radio emission due to changes in its host star. More radio data (preferably multi-site) and ancillary observations (e.g. magnetic maps) are required to further investigate the potential radio emission from the $\tau$ Bo\"{o}tis exoplanetary system.