| Description: | We recently reported on a search for pulsars and fast transients in Andromeda, using LOFAR. We compared our single-pulse results on the Andromeda Galaxy with those for a Galactic giant-pulse emitter, the Crab pulsar. The comparison is additionally fitting given the mythological struggle involving Andromeda and the sea monster as told by Ovidius.
The Crab Pulsar rotates 33 times per second and both poles are visible (as the "main pulse" and "inter-pulse"). So, up to 66 regular pulses can in principle be seen every second. But its regular emission is very weak -- only the occasional, very bright "giant pulses" can be detected. In a 1-hr observation, using 21 HBA core stations in “complex voltage” mode and using coherent dedispersion with Cees Bassa's CDMT, we identified 4000 pulses. The daily image shows an example of the occurrence of multiple pulses within a 1s window. Dashed lines indicate the same phase as the onset of the highest pulse. Giant pulses occur at the main and inter-pulse phase. The interstellar scattering at LOFAR frequencies is so large that the pulses have a very sharp rise but a slow, scattering decay. Subsequent pulses sometimes even blend into each other. |
