DISCOVERY OF A 7 SECOND ANOMALOUS X-RAY PULSAR IN THE DISTANT MILKY-WAY

We report the serendipitous discovery of a 7-s X-ray pulsar using data acquired with the Advanced Satellite for Cosmology and Astrophysics ( ASCA). The pulsar is detected as an unresolved source located towards a region of the Galactic plane (l,b similar or equal to 29.5,0.08) tha t coincides with an overdensity of star-formation tracers. The signal suffers tremendous foreground absorption, equivalent to N-H similar or equal to 10(23) cm(-2); the absorption correlates well with a line-of -sight that is tangential to the inner spiral arms and the 4-kpc molec ular ring. The pulsar is not associated with any known supernova remna nts or other cataloged objects in that direction. The near sinusoidal pulse (period P similar or equal to 6.9712) is modulated at 35% pulsed amplitude, and the steep spectrum is characteristic of hot black-body emission with temperature kT similar to 0.65 keV. We characterize the source as an anomalous X-ray pulsar (AXP). (C) 1998 Elsevier Science B.V.