Measuring a truncated disk in Aquila X-1

Ashley L. King, John A. Tomsick, Jon M. Miller, Jérôme Chenevez, Didier Barret, Steven E. Boggs, Deepto Chakrabarty, Finn Erland Christensen, William W. Craig, Felix Fürst, Charles J. Hailey, Fiona A. Harrison, Michael L. Parker, Daniel Stern, Patrizia Romano, Dominic J. Walton, William W. Zhang

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    Abstract

    We present NuSTAR and Swift observations of the neutron star Aquila X-1 during the peak of its 2014 July outburst. The spectrum is soft with strong evidence for a broad Fe Kα line. Modeled with a relativistically broadened reflection model, we find that the inner disk is truncated with an inner radius of 15 ± 3RG. The disk is likely truncated by either the boundary layer and/or a magnetic field. Associating the truncated inner disk with pressure from a magnetic field gives an upper limit of B<5 ± 2x108. Although the radius is truncated far from the stellar surface, material is still reaching the neutron star surface as evidenced by the X-ray burst present in the NuSTAR observation.
    Original languageEnglish
    JournalThe Astrophysical Journal Letters
    Volume819
    Issue number2
    Pages (from-to)L29
    Number of pages6
    ISSN2041-8205
    DOIs
    Publication statusPublished - 2016

    Keywords

    • Accretion
    • Accretion disks
    • Magnetic fields
    • Stars: neutron
    • X-rays: binaries
    • X-rays: bursts

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