Timing and Spectral Study of AX J1745.6-2901 with Suzaku

Yoshiaki Hyodo (1), Yoshihiro Ueda (1), Takayuki Yuasa (2), Yoshitomo Maeda (3), Kazuo Makishima (2), and Katsuji Koyama (1),

(1) Department of Astronomy, Graduate School of Science, Kyoto University, Kita-shirakawa Oiwake-cho, Sakyo, Kyoto 606-8502
(2) Department of Physics, School of Science, the University of Tokyo, 7-3-1, Hongo, Bunkyo, Tokyo 113-0033
(3) Institute of Space and Astronautical Science, 3-1-1, Yoshinodai, Sagamihara, Kanagawa, 229-8510

Paper: PASJ, 2009, accepted


The eclipsing low-mass X-ray binary \axj was observed with Suzaku in its outburst phase. Combining the Chandra observation made 1.5 month earlier than Suzaku, we determined the orbital period to be 30063.76+/-0.14 s. We found deep flux dips prior to the eclipse phase of orbit. The X-ray spectrum of the persistent phase is described with a combination of a direct and a scattered-in by dust emissions. During the eclipse, the X-ray spectrum becomes only the dust scattering (scattered-in) component. The optical depth of the dust-scattering is 10.5 at 1 keV. The direct component is composed of a blackbody likely from the neutron star surface and a disk-blackbody. No power-law component is found in the hard energy band up to 30 keV. A clear edge at 7.1 keV in the deep dip spectrum indicates that the major portion of Fe in the absorber is neutral or at low ionization state. We discovered four narrow absorption lines near the K-shell transition energies of Fe\emissiontypeXXV, Fe\emissiontypeXXVI, and Ni\emissiontypeXXVII. The absorption line features are well explained by the solar abundance gas in a bulk motion of 103 km s-1.

Preprints available from the authors at hyodo@cr.scphys.kyoto-u.ac.jp , or the raw TeX (no figures) if you click here.

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