Broadband study with Suzaku of the magnetar class

T. Enoto, K. Nakazawa, K. Makishima, N. Rea, K. Hurley, S. Shibata

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    Abstract

    Broadband (0.8-70 keV) spectra of the persistent X-ray emission from nine magnetars were obtained with Suzaku, including three objects in apparent outburst. The soft X-ray component was detected from all of them, with a typical blackbody temperature of kT ∼ 0.5 keV, while the hard-tail component, dominating above ∼10 keV, was detected at ∼1 mCrab intensity from seven of them. Therefore, the spectrum composed of a soft emission and a hard-tail component may be considered to be a common property of magnetars, both in their active and quiescent states.Wideband spectral analyses revealed that the hard-tail component has a 1-60 keV flux, Fh, comparable to or even higher than that carried by the 1-60 keV soft component, Fs. The hardness ratio (HR) of these objects, defined as ζ = Fh/Fs, was found to be tightly anti-correlated with their characteristic age τc as ζ = (3.3 ± 0.3) × (τc /1 kyr) -0.67±0.04 with a correlation coefficient of -0.989, over the range from ζ ∼10 to ζ ∼0.1. Magnetars in outburst states were found to lie on the same correlation as relatively quiescent ones. This HR is also positively correlated with their surface magnetic fields with a correlation coefficient of 0.873. In addition, the hard-tail component becomes harder toward sources with older characteristic ages, with the photon index changing from ∼1.7 to ∼0.4. © 2010 The American Astronomical Society. All rights reserved.
    Original languageEnglish
    JournalAstrophysical Journal Letters
    Volume722
    Issue number2 PART 2
    DOIs
    Publication statusPublished - 20 Oct 2010

    Keywords

    • Stars: evolution
    • Stars: magnetars
    • Stars: magnetic field
    • Stars: neutron

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    Enoto, T., Nakazawa, K., Makishima, K., Rea, N., Hurley, K., & Shibata, S. (2010). Broadband study with Suzaku of the magnetar class. Astrophysical Journal Letters, 722(2 PART 2). https://doi.org/10.1088/2041-8205/722/2/L162