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On the X-Ray Spectra of Anomalous X-Ray Pulsars and Soft Gamma Repeaters

Kaspi, V. M. and Boydstun, K. (2010) On the X-Ray Spectra of Anomalous X-Ray Pulsars and Soft Gamma Repeaters. Astrophysical Journal Letters, 710 (2). L115-L120. ISSN 2041-8205.

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We revisit the apparent correlation between soft X-ray band photon index and spin-down rate ύ previously reported for Anomalous X-ray Pulsars (AXPs) and Soft Gamma Repeaters (SGRs) by Marsden & White. Our analysis, improved thanks to new source discoveries, better spectral parameter measurements in previously known sources, and the requirement of source quiescence for parameter inclusion, shows evidence for the previously noted trend, although with greater scatter. This trend supports the twisted magnetosphere model of magnetars although the scatter suggests that factors other than ύ are also important.We also note possible correlations involving the spectra of AXPs and SGRs in the hard X-ray band. Specifically, the hard-band photon index shows a possible correlation with inferred ύ and B, as does the degree of spectral turnover. If the former trend is correct, then the hard-band photon index for AXP 1E 1048.1 − 5937 should be ∼0–1. This may be testable with long integrations by the International Gamma-Ray Astrophysics Laboratory, or by the upcoming focusing hard X-ray mission NuSTAR.

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Additional Information:© 2010 The American Astronomical Society. Issue 2 (2010 February 20). Received 2009 August 10, accepted for publication 2010 January 14. Published 2010 January 29. We thank A. Beloborodov, D. Eichler, M. Livingstone, and C. Thompson for useful conversations. We thank Caltech for its hospitality and support via a Summer Undergraduate Research Fellowship (K.B.) and a Moore Scholarship (V.M.K.). V.M.K. receives additional support from NSERC, FQRNT, CIFAR, and holds a Canada Research Chair and the Lorne Trottier Chair in Astrophysics and Cosmology.
Funding AgencyGrant Number
Caltech/Summer Undergraduate Research FellowshipUNSPECIFIED
Moore ScholarshipUNSPECIFIED
Natural Sciences and Engineering Research Council (Canada)UNSPECIFIED
Fonds Québécois de la Recherche sur la Nature et les Technologies (FQRNT)UNSPECIFIED
Cooperative Institute for Arctic Research (CIFAR )UNSPECIFIED
Subject Keywords:pulsars: general; stars: magnetic field; stars: neutron; X-rays: stars headings
Classification Code:PACS: 98.70.Qy; 98.70.Rz; 97.60.Jd; 95.30.Ky; 97.10.Ri
Record Number:CaltechAUTHORS:20100412-114303217
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Official Citation:V. M. Kaspi and K. Boydstun 2010 ApJ 710 L115 doi: 10.1088/2041-8205/710/2/L115
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17943
Deposited By: Ruth Sustaita
Deposited On:12 Apr 2010 22:42
Last Modified:29 Aug 2014 14:46

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