3rd Suzaku Conference 2009

Otaru, Japan
2009 June 29 – July 2

A Thorough Look at the Photoionized Wind and Absorption Dips in the Cyg X-1 System

Manfred Hanke, Jörn Wilms, Michael A. Nowak, Laura Barragán, Katja Pottschmidt, Norbert S. Schulz, Julia C. Lee

We present results from our simultaneous observations of the high-mass X-ray binary system Cygnus X-1 / HDE 226868 with Suzaku, Chandra-HETGS, XMM-Newton, RXTE , INTEGRAL, and Swift in 2008 April. The observations have been performed shortly after phase 0 of the 5.6 d orbit when our line of sight to the accreting black hole passes through the densest part of the wind of the donor star.
This contribution focuses on the analysis of the high resolution gratings spectra, which, in the context of a consistent description for the 0.5–600 keV spectrum, allow us to study the composition and dynamics of the highly photoionized wind. The soft X-ray band is strongly affected by transient absorption dips, caused by dense structures in the clumpy O-star wind. A color-color diagram shows evidence that the additional absorber causing the dips only covers part of the X-ray emitting region. The spectroscopic analysis reveals changes in the ionization state of the wind material between dip and non-dip phases.

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ADS Proceedings

Centaurus X-3 with Suzaku

Katja Pottschmidt et al.

Suzaku observed the high mass X-ray binary and accreting X-ray pulsar Centaurus X-3 over one 2.1 day binary orbit in December 2008. Here we present preleminary results from analyzing this observation showing the overall XIS and PIN lightcurves as well as modeling the observation-averaged joint XIS and PIN broad band spectrum. The latter is modified by a three-component iron line complex in the 6.4–6.9 keV region, as previously observed by ASCA and Chandra, as well as the known cyclotron resonance scattering feature at 31 keV.
An interesting property of this observation is its clear division into a bright first half of the binary orbit and an almost completely obscured second half, disrupted by bright flaring. This behavior is different from the usual orbital profile, where, while the second half of the orbit is less bright and has a tendency to show pre-eclipse dips, persistent X-ray emission is still seen (Suchy et al., 2008). In a future deeper analysis we expect to derive new constraints on the wind structure of the system and to study it in respect to Supergiant Fast X-ray Transients, sources with similar components, which have short, minutes to hours long outburst.
In addition we present an initial study of the pileup effect present in the XIS data of this bright source, after taking an improved attitude correction into account. We find that the brightest part of the orbit shows a maximum pile-up fraction of 20–30%, depending on the XIS chip and the editing mode. These results clearly indicate that in the next iteration of this analysis these regions of the point spread function have to be excluded. In addition, a time resolved spectral analysis of the different emission states is required and planned.


Suzaku Observations of Cygnus X-1

Jörn Wilms, Michael A. Nowak, Manfred Hanke, Sarah N. Trowbridge, Sera B. Markoff, Katja Pottschmidt, P. Coppi

We present highlights from a series of four simultaneous Suzaku/RXTE observations of the black hole candidate Cyg X-1 concentrating on the broad band 0.8–300keV spectrum and the broad Fe Kα line. All of these observations occurred at or very near the superior conjunction of the black hole and are therefore dominated by absorption due to the stellar wind of the companion, which is the subject of the accompanying contribution by Hanke et al. We find that it is necessary to carefully model this ionized absorption, which is not resolved with the XIS, in order to properly model the soft end of the Suzaku-XIS spectra.
The observations are among the hardest observations of the source since 1996. The spectrum of the source can be similarly well described by a physically motivated Comptonization model, where the Comptonizing plasma partly covers the accretion disk, and by a model where the hard emission comes from a jet. There is little evidence for a soft disk component, which formally corresponds to a small, inner disk radius. The Fe Kα line consists of a narrow core in emission, as well as by narrow Fe XXV absorption, both of which are also seen in simultaneous Chandra observations, and a broad component. The latter can be modeled with a relativistic line.
We discuss the influence of pile up onto this interpretation and comment on the cross-calibration of Suzaku with other instruments.