A Caltech Library Service

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.

PDF - Published Version
See Usage Policy.


Use this Persistent URL to link to this item:


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.

Item Type:Article
Related URLs:
URLURL TypeDescription
Kaspi, V. M.0000-0001-9345-0307
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 Fellowship (SURF)UNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Fonds de recherche du Québec – Nature et technologies (FRQNT)UNSPECIFIED
Canadian Institute for Advanced Research (CIFAR)UNSPECIFIED
Subject Keywords:pulsars: general; stars: magnetic field; stars: neutron; X-rays: stars headings
Issue or Number:2
Classification Code:PACS: 98.70.Qy; 98.70.Rz; 97.60.Jd; 95.30.Ky; 97.10.Ri
Record Number:CaltechAUTHORS:20100412-114303217
Persistent URL:
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:04 Dec 2019 20:20

Repository Staff Only: item control page