Broadband X-ray spectroscopy of A0535+262 with Suzaku

The transient X-ray binary pulsar A0535+262 was observed with Suzaku on 2005 September 14 when the source was in the declining phase of the August-September minor outburst. The similar to 103 s X-ray pulse profile was strongly energy dependent, with a double-peaked profile in the soft X-ray energy band (< 3 keV) and a single-peaked smooth profile in hard X-rays. The width of the primary dip is found to increase with energy. The broadband energy spectrum of the pulsar is well described with a negative and positive power law with exponential (NPEX) continuum model, along with a blackbody component for soft excess. A weak iron K alpha emission line with an equivalent width similar to 25 eV was detected in the source spectrum. The blackbody component is found to be pulsating over the pulse phase, implying that the accretion column and/or the inner edge of the accretion disk may be the possible emission site of the soft excess in A0535+262. The higher value of the column density is believed to be the cause of the secondary dip in the soft X-ray energy band. The iron line equivalent width is found to be constant (within errors) over the pulse phase. However, a sinusoidal type of flux variation of the iron emission line, in phase with the hard X-ray flux, suggests that the inner accretion disk is the possible emission region of the iron fluorescence line.