PSR J2229+6114: Discovery of an energetic young pulsar in the error box ofthe EGRET source 3EG J2227+6122

We report the detection of radio and X-ray pulsations at a period of 51.6 m s from the X-ray source RX/AX J2229.0+6114 in the error box of the EGRET so urce 3EG J2227+6122. An ephemeris derived from a single ASCA observation an d multiple epochs at 1412 MHz from Jodrell Bank indicates steady spin-down with (P) over dot = 7.83 x 10(-14) s s(-1). From the measured P and (P) ove r dot , we derive spin-down power (E) over dot = 2.2 x 10(37) ergs s(-1), m agnetic field B-P = 2.0 x 10(12) G, and characteristic age P/2(P) over dot = 10,460 yr. An image from the Chandra X-Ray Observatory reveals a point so urce surrounded by centrally peaked diffuse emission that is contained with in an incomplete radio shell. We assign the name G106.6+2.9 to this new sup ernova remnant, which is evidently a pulsar wind nebula. For a distance of 3 kpc estimated from X-ray absorption, the ratio of X-ray luminosity to spi n-down power is approximate to8 x 10(-5), smaller than that of most pulsars but similar to the Vela pulsar. If PSR J2229+6114 is the counterpart of 3E G J2227+6122, then its efficiency of gamma -ray production, if isotropic, i s 0.016 (d/3 kpc)(2). It obeys an established trend of gamma -ray efficienc y among known gamma -ray pulsars, which, in combination with the demonstrat ed absence of any other plausible counterpart for 3EG J2227+6122, makes the identification compelling. If confirmed, this identification bolsters the pulsar model for unidentified Galactic EGRET sources.