Broad band X-ray spectroscopy of A0535+262 with SUZAKU

TL;DR

This study presents broad-band X-ray spectroscopy of A0535+262 with Suzaku, revealing energy-dependent pulse profiles, spectral components, and emission line characteristics, providing insights into the accretion processes and emission sites.

Contribution

First detailed broad-band spectral analysis of A0535+262 with Suzaku, identifying pulsating soft excess and emission line origins, enhancing understanding of accretion geometry.

Findings

Pulse profile varies with energy, double at soft X-rays, single at hard X-rays.

Soft excess is pulsating, likely from accretion column or inner disk.

Iron line flux varies sinusoidally with pulse phase, indicating inner disk origin.

Abstract

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 ~103 s X-ray pulse profile was strongly energy dependent, a double peaked profile at soft X-ray energy band (<3 keV) and a single peaked smooth profile at hard X-rays. The width of the primary dip is found to be increasing with energy. The broad-band 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 ~25 eV was detected in the source spectrum. The blackbody component is found to be pulsating over the pulse phase implying 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 at 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 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.