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Radio pulses from Andromeda?

Submitter: Eduardo Rubio-Herrera, B.W. Stappers, J.W.T. Hessels & R. Braun
Description: We have used the Westerbork Synthesis Radio Telescope (WSRT) to perform the most sensitive and comprehensive survey yet undertaken for pulsars and fast radio transients in the Andromeda Galaxy (Rubio-Herrera et al.). The survey was made at a central frequency of 328 MHz using the WSRT in a special observing mode which allowed us to cover a large area of the sky (an area equivalent to 6 full moons) at millisecond time resolution.

We have detected several single pulse events which potentially originate from neutron stars in M31, though remain unconfirmed. One in particular, shown in these images, was seen at multiple times including a burst of six pulses in about 2000 seconds.

  • The top-left plot is a sum of six 5-6 sigma bursts; the top-right shows how the signal-to-noise of this cumulative sum behaves as a function of dispersion measure (the number of free electrons between us and M31).

  • The bottom plot shows the dispersion measure versus time parameter space that we searched as well as the individual pulses (circled in red).

    The dispersion measure of this source (~54 pc cm-3), is consistent with it being beyond the edge of our Galaxy and potentially on the near-side of Andromeda. This survey has also allowed us to place constraints on the luminosity function of pulsars in M31.
  • Copyright: Rubio-Herrera/Hessels
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