Identifying as many gamma-ray pulsars as possible in the Fermi Large Area Telescope ( LAT ) data helps test pulsar emission models by comparing predicted and observed properties for a large , varied sample with as little selection bias as possible .
It also improves extrapolations from the observed population to estimate the contribution of unresolved pulsars to the diffuse gamma-ray emission .
We use a recently developed method to determine the probability that a given gamma-ray photon comes from a known position in the sky , convolving the photon ’ s energy with the LAT ’ s energy-dependent point-spread-function ( PSF ) , without the need for an accurate spatial and spectral model of the gamma-ray sky around the pulsar .
The method is simple and fast and , importantly , provides probabilities , or weights , for gamma rays from pulsars too faint for phase-integrated detection .
We applied the method to over a thousand pulsars for which we obtained rotation ephemerides from radio observations , and discovered gamma-ray pulsations from 16 pulsars , 12 young and 4 recycled .
PSR J2208+4056 has spindown power \dot { E } = 8 \times 10 ^ { 32 } erg s ^ { -1 } , about three times lower than the previous observed gamma-ray emission “ deathline ” .
PSRs J2208+4056 and J1816 - 0755 have radio interpulses , constraining their geometry and perhaps enhancing their gamma-ray luminosity .
We discuss whether the deathline is an artifact of selection bias due to the pulsar distance .