Q2 (panels a and b) and beam differences for Q4a (panel c), Q4b (panel d), Q4e (panel e), and Q4f (panel f) for τ Boo in observation L570725 from the range 21–30 MHz in Stokes-V (). Panel a: Q2 for the ON-beam vs the OFF-beam 2. Panel b: Q2 for the OFF-beam 1 vs. the OFF-beam 2. Panel c: Q4a (number of peaks). Panel d: Q4b (power of peaks). Panel e: Q4e (peak offset). Panel f: Q4f (peak offset). For panels c–f the black lines are the ON-beam difference with the OFF beam 2 and the red lines are the OFF beam difference. The dashed lines are statistical limits (1, 2, 3σ) of the difference between all the Q4 values derived using two different Gaussian distributions (each performed 10 000 times). We do not see any excess signal in the ON-beam compared to the OFF-beams. Therefore, this observation is a non-detection for burst emission. We find by performing Gaussian simulations that the probability to obtain the OFF beam curve in Q4f (panel f) is ~73%, whereas the probability to randomly reproduce the ON-beam curve is ~82%.