Discovery of 51 pulsars in a reanalysis of the Green Bank North Celestial Cap Survey and a revised pulsar census

Abstract

We present results from a reanalysis of the Green Bank North Celestial Cap (GBNCC) survey, conducted at 350 MHz with the Green Bank Telescope between 2009 and 2020, covering the sky with declinations $δ>-40^\circ$. We searched the survey data using an FFT-based periodicity search, with candidate selection extending to very low spectral signal-to-noise ratios and summing up to 32 harmonics. From the 60 promising candidates identified in this search, we confirmed 51 new pulsars using the Green bank and CHIME. We also used a direct folding search method (DFSM) to search for slow pulsars between 500 ms and 10 s. Of the 51 pulsars identified in the FFT search, 43 fall within this period range, all of which were found by the DFSM. The DFSM also found an additional pulsar that had been missed during the inspection of the FFT candidates. Most of the new discoveries are canonical pulsars, with spin periods ranging from 299 ms to 4.4 s and dispersion measures from 10 to 192 $\rm pc \, cm^{-3}$. We also found a binary millisecond pulsar with a spin period of 3.2 ms in a 4.5-d orbit. We redetected 855 pulsars in the data, 825 of which were found in the FFT search. Within the effective parameter space of our periodicity search, the FFT search recovered $\sim$98 % of the known pulsars within the survey sensitivity limits. After accounting for previously reported pulsars whose observations were not processed or whose parameters lay outside our search range, the updated GBNCC census now includes 964 pulsars.