Abstract
We present a detailed spectral and timing analysis of the High Mass X-ray Binary (HMXB) 4U 1909+07 with INTEGRAL and RXTE. 4U1909+07 is a persistent accreting X-ray pulsar with a period of approximately 605 s. The period changes erratically consistent with a random walk expected for a wind accreting system. INTEGRAL detects the source with an average of 2.4 cps (corresponding to 15mCrab), but sometimes exhibits flaring activity up to 50 cps (i.e. 300mCrab). The strongly energy dependent pulse profile shows a double peaked structure at low energies and only a single narrow peak at energies above 20 keV. The phase averaged spectrum is well described by a powerlaw modified at higher energies by an exponential cutoff and photoelectric absorption at low energies. In addition at 6.4 keV a strong iron fluorescence line and at lower energies a blackbody component are present. We performed phase resolved spectroscopy to study the pulse phase dependence of the spectral parameters: while most spectral parameters are constant within uncertainties, the blackbody normalization and the cutoff folding energy vary strongly with phase.
Highlights
In 2005, [16] detected an OB star in the near infrared at the location of the X-ray source, confirming that the system is a High Mass X-ray Binary (HMXB)
We have presented a detailed study with INTEGRAL and RXTE of 4U 1909+07
We have shown that the pulse period changes strongly with time
Summary
In 2005, [16] detected an OB star in the near infrared at the location of the X-ray source, confirming that the system is a High Mass X-ray Binary (HMXB). They estimated the distance to the source to 7 kpc [16]. [11] were able to refine the binary orbit parameters They obtained M = 9–31 M and R ≤ 22 R for the mass and radius of the companion star assuming the canonical mass of 1.4 M for the neutron star.
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