Suzaku Observation of the Supergiant Fast X-Ray Transient AX J1841.0-0536

Abstract

We observed the supergiant fast X-ray transient AX J1841.0-0536 with Suzaku in 2011 March. Many short flares with time-scales of a few hundred seconds and a large flare with a peak flux (1.0-10 keV) of ≳; 2 × 10^-10 erg s^-1 cm^-2 were detected. The broad-band (1.0-40 keV) spectrum was fitted with a cut-off power-law continuum plus a Kα line from a neutral iron absorbed by partial covering gas. In addition, a broad absorption feature was found in a high-energy band. The photon index of the power-law is 1.01 ± 0.12 in a low-luminosity state, and decreases (becomes hard) with increasing luminosity. On the other hand, the absorption column density and the iron line equivalent width are nearly constant. The covering fraction does not vary significantly, except for the full coverage epoch at the end of the large flare. We thus propose that the X-ray emission is due to subsequent in-falls of many small blobs.