A Stacking Survey of Gamma-ray Pulsars

Abstract

We report on a likelihood stacking search for gamma-ray pulsars at 362 high-latitude locations that coincide with known radio pulsar positions. We observe a stacked signal conservatively 2.5$\sigma$ over the background. Stacking their likelihood profiles in spectral parameter space implies a pulsar-like spectral index and a characteristic flux a factor of 2 below the Fermi-LAT point source sensitivity, assuming isotropic/unbeamed emission from all sample pulsars. The same procedures performed on empty control fields indicate that the pulsars as a population can be distinguished from the background with a $\Delta$(TS) = 28 at the peak location (or 4.8$\sigma$), and the stacked spectra of the control fields are distinctly softer than those of the pulsars. This study also probes a unique region of parameter space populated by low \Edot\ pulsars, most of which have no \gray\ ephemeris available, and is sensitive to high duty cycles. We also discusses the possible \gray\ emission mechanism from such pulsars.