Colafrancesco, SergioSergioColafrancescoNoutsos, A.A.NoutsosAbdo, A. A.A. A.AbdoAckermann, M.M.Ackermann2020-09-172020-09-172011-02-01https://hdl.handle.net/20.500.13025/3662We report on the first year of Fermi ³-ray observations of pulsed high-energy emission from the old PSR J2043 + 2740. The study of the ³-ray efficiency of such old pulsars gives us an insight into the evolution of pulsars ability to emit in ³ rays as they age. The ³-ray light curve of this pulsar above 0.1 GeV is clearly defined by two sharp peaks, 0.353 ± 0.035 periods apart. We have combined the ³-ray profile characteristics of PSR J2043 + 2740 with the geometrical properties of the pulsars radio emission, derived from radio-polarization data, and constrained the pulsar-beam geometry in the framework of a two-pole caustic (TPC) and an outer gap (OG) model. The ranges of magnetic inclination and viewing angle were determined to be ±, ¶ < 52°-57°, 61°-68° for the TPC model, and ±, ¶ < 62°-73°, 74°-81° and ±, ¶ < 72°-83°, 60°-75° for the OG 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, ³-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 five and ten times less energetic, respectively.Article Journalhttp://dx.doi.org/10.1088/0004-637X/728/2/7754dcce0f8580fe1368eeb51e