Discovery of a slow X-ray pulsator, AX J1740.1-2847, in the galactic center region

We report the discovery of an X-ray pulsar, AX J1740.1-2847, from the Galactic center region. This source was found as a faint hard X-ray object on 1998 September 7-8 with the ASCA Galactic center survey observation. Then, coherent pulsations of P = 729 ± 14 s period were detected. The X-ray spectrum is described by a flat power-law of ∼ 0.7 photon index. The large absorption column of log NH ∼ 22.4 cm-2 indicates that AX J1740.1-2847 is a distant source, larger than 2.4 kpc, and possibly near to the Galactic center region. The luminosity in the 2-10 keV band is larger than 2.5×1033 erg s-1, or likely to be 3.2 × 1034 erg s-1 at the Galactic-center distance. Although the slow-pulse period does not discriminate whether AX J1740.1-2847 is a white dwarf or neutron-star binary, the flat power-law and moderate luminosity strongly favor a neutron-star binary.