Confirming Pulsar Candidates from CHAMPSS using a Multiday Coherent Search

Magnus L'Argent ( Université McGill )

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a drift scan radio telescope that offers a unique opportunity to make daily observations of the entire northern sky. The CHIME All-Sky Multiday Pulsar Stack Search (CHAMPSS) utilizes this daily cadence to search for periodic signals in the CHIME Fast Radio Burst datastream. The periodic pulsar signals appear as sharp peaks in power spectra created from a fast fourier transform of the dedispersed datastream. The power spectra from the same pointing are then summed each day to create an ongoing, multi-day stack that gives sensitivity to faint, persistent sources.

Phase coherent searches offer higher sensitivity compared to phase incoherent searches like power spectra stacking. However, it is too computationally costly to blindly search the datastream and pulsars will not align in phase over multiple days due to spindown, so the power spectra stack search provides an initial period estimate to search around. Promising candidates found in the stack are confirmed by folding the time-dependent data on their initial period estimate. Strong pulsars will appear in a single day fold. Weaker pulsars will only appear after aligning the pulsed signal in phase over multiple observations. In this talk, I will give an overview of the CHAMPSS candidate confirmation process I have developed. I will describe how observations from multiple days are aligned in phase to create an initial timing solution and how aliased signals are removed.

In the first commissioning survey, covering 4% of the CHIME sky in over 2 months, three new pulsars have been discovered and confirmed using this phase coherent process. We also re-detect several pulsars discovered through single pulses at CHIME as well as sources in the FAST Galactic Plane Pulsar Survey (GPPS).