Discovery of a Slow X-Ray Pulsator, AX J1740.1-2847, in the Galactic Center Region

Masaaki Sakano(1), Ken'ichi Torii(1), Katsuji Koyama(2), Yoshitomo Maeda(3), Shigeo Yamauchi

(1)Space Utilization Research Program (SURP), National Space Development Agency of Japan (NASDA), 2-1-1 Sengen, Tsukuba, Ibaraki 305-8505,
(2)Department of Physics, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo, Kyoto 606-8502,
(3) Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802-6305, U.S.A.,
(4) Faculty of Humanities and Social Sciences, Iwate University, 3-18-34 Ueda, Morioka, Iwate 020-8550

Paper: PASJ (2000), Vol.52 No.6 (Dec. 25), in press


EPrint Server: astro-ph/0008331


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 7-8 September 1998 with the ASCA Galactic center survey observation. Then, coherent pulsations of P=729+/- 14 sec 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 N_H 22.4 (cm-2) indicates that AX J1740.1-2847 is a distant source, larger than 2.4 kpc, and possibly near at 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.

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