Discovery of a 1247 s pulsar in the Be X-ray binary SAX J2239.3+6116

A search for pulsations from the Be X-ray binary SAX J2239.3+6116, through observations with the Narrow Field Instruments on BeppoSAX and the Proporti onal Counter Array on RXTE, yielded the clear presence of a 1247 s coherent oscillation. Given the fairly high X-ray luminosity on previous occasions (up to a few times 10(36) erg s(-1) in 2 to 28 keV), the oscillation must b e due to the spin of a neutron star. Assuming that the 262 day recurrence t ime is the orbital period, SAX J2239.3+6116 has both the longest orbital pe riod and the longest pulse period of 24 Be X-ray binaries with measured orb ital periods.