We report on the first year of Fermi \gamma -ray observations of pulsed high-energy emission from the old PSR J2043+2740 .
The study of the \gamma -ray efficiency of such old pulsars gives us an insight into the evolution of pulsars ’ ability to emit in \gamma rays as they age .
The \gamma -ray lightcurve of this pulsar above 0.1 GeV is clearly defined by two sharp peaks , 0.353 \pm 0.035 periods apart .
We have combined the \gamma -ray profile characteristics of PSR J2043+2740 with the geometrical properties of the pulsar ’ s radio emission , derived from radio polarization data , and constrained the pulsar-beam geometry in the framework of a Two Pole Caustic and an Outer Gap model .
The ranges of magnetic inclination and viewing angle were determined to be \ { \alpha, \zeta \ } \sim \ { 52 ^ { \circ } – 57 ^ { \circ } , 61 ^ { \circ } – 68 ^ { \circ } \ } for the Two Pole Caustic model , and \ { \alpha, \zeta \ } \sim \ { 62 ^ { \circ } – 73 ^ { \circ } , 74 ^ { \circ } – 81 ^ { \circ } \ } and \ { \alpha, \zeta \ } \sim \ { 72 ^ { \circ } – 83 ^ { \circ } , 60 ^ { \circ } – 75 ^ { \circ } \ } for the Outer Gap model .
Based on this geometry , we assess possible birth locations for this pulsar and derive a likely proper motion , sufficiently high to be measurable with VLBI .
At a characteristic age of 1.2 Myr , PSR J2043+2740 is the third oldest of all discovered , non-recycled , \gamma -ray pulsars : it is twice as old as the next oldest , PSR J0357+32 , and younger only than the recently discovered PSR J1836+5925 and PSR J2055+25 , both of which are at least 5 and 10 times less energetic , respectively .