INTEGRAL and Swift/XRT observations of IGR J18179−1621

Authors

  • J. Li,

    Corresponding author
    1. Key Laboratory for Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing 100049, China
    2. Institut de Ciències de l’Espai (IEEC-CSIC), Campus UAB, Torre C5, 2a planta, 08193 Barcelona, Spain
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  • S. Zhang,

    Corresponding author
    1. Key Laboratory for Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing 100049, China
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  • D. F. Torres,

    1. Institut de Ciències de l’Espai (IEEC-CSIC), Campus UAB, Torre C5, 2a planta, 08193 Barcelona, Spain
    2. Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Spain
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  • A. Papitto,

    1. Institut de Ciències de l’Espai (IEEC-CSIC), Campus UAB, Torre C5, 2a planta, 08193 Barcelona, Spain
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  • Y. P. Chen,

    1. Key Laboratory for Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing 100049, China
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  • J. M. Wang

    1. Key Laboratory for Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, 19B Yuquan Road, Beijing 100049, China
    2. National Astronomical Observatories of China, Chinese Academy of Sciences, 20A Datun Road, Beijing 100020, China
    3. Theoretical Physics Center for Science Facilities (TPCSF), Chinese Academy of Sciences, Beijing 100049, China
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E-mail: jianli@ihep.ac.cn (JL); szhang@ihep.ac.cn (SZ)

ABSTRACT

IGR J18179−1621 is a hard X-ray binary transient discovered recently by INTEGRAL. Here we report on detailed timing and spectral analysis of IGR J18179−1621 in X-rays based on available INTEGRAL and Swift data. From the INTEGRAL analysis, IGR J18179−1621 is detected with a significance of 21.6σ in the 18–40 keV band by ISGRI and 15.3σ in the 3–25 keV band by JEM-X, between 2012 February 29 and 2012 March 1. We analyse two quasi-simultaneous Swift ToO observations. A clear 11.82-s pulsation is detected above the white noise at a confidence level larger than 99.99 per cent. The pulse fraction is estimated as 22 ± 8 per cent at 0.2–10 keV. No sign of pulsation is detected by INTEGRAL/ISGRI in the 18–40 keV band. With Swift and INTEGRAL spectra combined in soft and hard X-rays, IGR J18179−1621 could be fitted by an absorbed power law with a high-energy cut-off plus a Gaussian absorption line centred at 21.5 keV. An additional absorption intrinsic to the source is found, while the absorption line is evidence for a most probable origin from cyclotron resonant scattering and suggests a magnetic field in the emitting region of ∼2.4 × 1012 G.

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