Secondary radio eclipse of the transiting planet HD 189733 b: an upper limit at 307-347 MHz

TL;DR

This study attempts to detect radio emission from the secondary eclipse of exoplanet HD 189733 b at 307-347 MHz, setting an upper flux limit and finding no definitive eclipse signal.

Contribution

First radio observation of a transiting exoplanet's secondary eclipse, establishing an upper flux limit at 307-347 MHz.

Findings

Upper flux density limit of 81 mJy at 3-sigma confidence.

No definitive detection of eclipse signal, with a marginal 2-sigma hint in a specific band.

Results align with theoretical predictions of planetary radio emission.

Abstract

We report the first attempt to observe the secondary eclipse of a transiting extra-solar planet at radio wavelengths. We observed HD 189733 b with the Robert C. Byrd Green Bank Telescope of the NRAO over about 5.5 hours before, during and after secondary eclipse, at frequencies of 307 - 347 MHz. In this frequency range, we determine the 3-sigma upper limit to the flux density to be 81 mJy. The data are consistent with no eclipse or a marginal reduction in flux at the time of secondary eclipse in all subsets of our bandwidth; the strongest signal is an apparent eclipse at the 2-sigma level in the 335.2 - 339.3 MHz region. Our observed upper limit is close to theoretical predictions of the flux density of cyclotron-maser radiation from the planet.