Wilms J (2007)
Publication Status: Published
Publication Type: Journal article
Publication year: 2007
Publisher: EDP SCIENCES S A
Book Volume: 462
Pages Range: 995-U71
Journal Issue: 3
DOI: 10.1051/0004-6361:20053878
Aims: We present the results of the INTEGRAL monitoring campaign on the accreting low mass X-ray binary pulsar GX1+4 performed during the Galactic plane scan of the INTEGRAL Core Programme.Methods. The source was observed in different luminosity states ranging from L20-40 keV = 1.7 x 10(-10) erg cm(-2) s(-1), to L20-40 keV = 10.5 x 10(-10) erg cm(-2) s(-1) for about 779 ks from March 2003 until October 2004.Results. Our observations confirm the secular spin down of GX 1+4 with the spin period (P-s) varying from 139.63 s to 141.56 s. In the highest luminosity state, a spin-up phase is observed. The phase-averaged spectrum of the source was modelled either with an absorbed cut-off power law or with a Comptonization model with significantly different parameters in the two brightest luminosity states. No evidence of any absorption-like feature is observed in the phase averaged spectrum up to 110 keV. At highest luminosity, the source is found to pulsate up to 130 keV. Phase resolved spectroscopy reveals a phase-dependent continuum and marginal evidence for an absorption feature at 34 +/- 2 keV in the descending part of the pulse. If interpreted as due to electron resonant cyclotron scattering, the magnetic field in the emitting region would be (2.9 +/- 0.2) x 10(12) (1+z) G where z is the gravitational red shift of the emitting region. We also observed a very low luminosity state, typical of this source, which lasted for about two days during which the source spectrum was modelled by a simple power law, and a pulsed signal was still detectable in the 15-100 keV energy range.
APA:
Wilms, J. (2007). INTEGRAL observation of the accreting pulsar GX 1+4. Astronomy & Astrophysics, 462(3), 995-U71. https://dx.doi.org/10.1051/0004-6361:20053878
MLA:
Wilms, Jörn. "INTEGRAL observation of the accreting pulsar GX 1+4." Astronomy & Astrophysics 462.3 (2007): 995-U71.
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