We have searched for prompt radio emission from nine Gamma Ray Bursts ( GRBs ) with a 12 m telescope at 1.4 GHz , with a time resolution of 64 ~ { } \mathrm { \mu s } to 1 s. We detected single dispersed radio pulses with significances > 6 \sigma in the few minutes following two GRBs .
The dispersion measures of both pulses are well in excess of the expected Galactic values , and the implied rate is incompatible with known sources of single dispersed pulses .
The arrival times of both pulses also coincide with breaks in the GRB X-ray light curves .
A null trial and statistical arguments rule out random fluctuations as the origin of these pulses with > 95 \% and \sim 97 \% confidence , respectively , although a simple population argument supports a GRB origin with confidence of only 2 % .
We caution that we can not rule out RFI as the origin of these pulses .
If the single pulses are not related to the GRBs we set an upper limit on the flux density of radio pulses emitted between 200 to 1800 s after a GRB of 1.27 w ^ { -1 / 2 } \mathrm { Jy } , where 6.4 \times 10 ^ { -5 } \mathrm { s } < w < 32 \times 10 ^ { -3 } \mathrm { s } is the pulse width .
We set a limit of less than 760 Jy for long timescale ( > 1 s ) variations .
These limits are some of the most constraining at high time resolution and GHz frequencies in the early stages of the GRB phenomenon .