  Since the radio-frequency emission from planets is expected to be strongly
influenced by their interaction with the magnetic field and corona of the host
star, the physics of this process can be effectively constrained by making
sensitive measurements of the planetary radio emission. Up to now, however,
numerous searches for radio emission from extrasolar planets at radio
wavelengths have only yielded negative results. Here we report deep radio
observations of the nearby Neptune-mass extrasolar transiting planet HAT-P-11b
at 150 MHz, using the Giant Meterwave Radio Telescope (GMRT). On July 16, 2009,
we detected a 3-sigma emission whose light curve is consistent with an eclipse
when the planet passed behind the star. This emission is at a position 14
arcsec from the transiting exoplanet's coordinates; thus, with a synthetized
beam of FWHM~16 arcsec, the position uncertainty of this weak radio signal
encompasses the location of HAT-P-11. We estimate a 5% false positive
probability that the observed radio light curve mimics the planet's eclipse
light curve. If the faint signature is indeed a radio eclipse event associated
with the planet, then its flux would be 3.87 mJy +/- 1.29 mJy at 150 MHz.
However, our equally sensitive repeat observations of the system on November
17, 2010 did not detect a significant signal in the radio light curve near the
same position. This lack of confirmation leaves us with the possibility of
either a variable planetary emission, or a chance occurrence of a false
positive signal in our first observation. Deeper observations are required to
confirm this hint of 150 MHz radio emission from HAT-P-11b.
