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Post Info TOPIC: 4U 1909+07
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RE: 4U 1909+07
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Title: Staring at 4U 1909+07 with Suzaku
Authors: F. Fuerst (1,2), K. Pottschmidt (3,4), I. Kreykenbohm (1), S. Mueller (1), M. Kuehnel (1), J. Wilms (1), R. E. Rothshild (5) ((1) Remeis-Observatory Bamberg and ECAP, (2) SRL, California Institute of Technology, (3) CRESST and GSFC, (4) CSST, UMBC, (5) CASS, USCD)

We present an analysis of the neutron star High Mass X-ray Binary (HMXB) 4U 1909+07 mainly based on Suzaku data. We extend the pulse period evolution, which behaves in a random-walk like manner, indicative of direct wind accretion. Studying the spectral properties of 4U 1909+07 between 0.5 to 90 keV we find that a power-law with an exponential cutoff can describe the data well, when additionally allowing for a blackbody or a partially covering absorber at low energies. We find no evidence for a cyclotron resonant scattering feature (CRSF), a feature seen in many other neutron star HMXBs sources. By performing pulse phase resolved spectroscopy we investigate the origin of the strong energy dependence of the pulse profile, which evolves from a broad two-peak profile at low energies to a profile with a single, narrow peak at energies above 20 keV. Our data show that it is very likely that a higher folding energy in the high energy peak is responsible for this behaviour. This in turn leads to the assumption that we observe the two magnetic poles and their respective accretion columns at different phases, and that these accretions column have slightly different physical conditions.

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Blobrana


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Title: 4U 1909+07: a well-hidden pearl (Conf. Proc.)
Authors: F. Fuerst, I. Kreykenbohm, L. Barragán, J. Wilms, R. E. Rothschild, S. Suchy, K. Pottschmidt
(Version v2)

We present the first detailed spectral and timing analysis of the High Mass X-ray Binary (HMXB) 4U 1909+07 with INTEGRAL and RXTE. 4U 1909+07 is detected with an average of 2.4cps in ISGRI, but shows flares up to ~50cps. The system shows a pulse period of 605s, but we found that the period changes erratically around this value. The pulse profile is extremely energy dependent: while it shows a double peaked structure at low energies, the secondary pulse decreases rapidly with increasing energy and above 20keV only the primary pulse is visible. This evolution is consistent between PCA, HEXTE and ISGRI. We find that the phase averaged spectrum can be well fitted with a photoabsorbed power law with a cutoff at high energies and a blackbody component. To investigate the peculiar pulse profile, we performed phase resolved spectral analysis. We find that a change in the cutoff energy is required to fit the changing spectrum of the different pulse phases.

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