INTEGRAL observation of the accreting pulsar GX 1+4
Ferrigno, C., Segreto, A., Santangelo, A., Wilms, J. (Joern), Kreykenbohm, I., Denis, M. (Mirosław) and Staubert, R.. (2007) INTEGRAL observation of the accreting pulsar GX 1+4. Astronomy & Astrophysics, Vol.462 (No.3). pp. 995-1005. ISSN 0004-6361
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Official URL: http://dx.doi.org/10.1051/0004-6361:20053878
Aims. We present the results of the INTEGRAL monitoring campaign on the accreting low mass X-ray binary pulsar GX 1+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 × 10−10 erg cm−2 s−1, to L20−40 keV = 10.5 × 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 (Ps) 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) × 1012(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.
|Item Type:||Journal Article|
|Subjects:||Q Science > QB Astronomy|
|Divisions:||Faculty of Science > Physics|
|Library of Congress Subject Headings (LCSH):||Pulsars, X-ray sources, Galactic, Double stars|
|Journal or Publication Title:||Astronomy & Astrophysics|
|Official Date:||February 2007|
|Page Range:||pp. 995-1005|
|Access rights to Published version:||Open Access|
|Funder:||Agenzia spaziale italiana [Italian Space Agency] (ASI), Deutsche Forschungsanstalt für Luft- und Raumfahrt (DLR)|
|Grant number:||I/R/046/04 (ASI), ASI-INAF I/023/05/0 (ASI), 50 OG 9601 (DLR), 50 OG 0501 (DLR)|
Barthelmy, S. D., Barbier, L. M., Cummings, J. R., & SWIFT TEAM. 2005,
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