TheChandraX‐Ray Spectrum of the 10.6 s Pulsar in Westerlund 1: Testing the Magnetar Hypothesis
Author(s) -
Stephen L. Skinner,
Rosalba Perna,
Svetozar A. Zhekov
Publication year - 2006
Publication title -
the astrophysical journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.376
H-Index - 489
eISSN - 1538-4357
pISSN - 0004-637X
DOI - 10.1086/508059
Subject(s) - magnetar , physics , astrophysics , pulsar , neutron star , x ray pulsar , black body radiation , radius , astronomy , context (archaeology) , binary pulsar , accretion (finance) , pulsar planet , x ray , millisecond pulsar , radiation , nuclear physics , paleontology , computer security , computer science , biology
Two sensitive Chandra X-ray observations of the heavily-reddened galacticstarburst cluster Westerlund 1 in May and June 2005 detected a previouslyunknown X-ray pulsar (CXO J164710.20-455217). Its slow 10.6 s pulsations,moderate X-ray temperature kT $\approx$ 0.5 keV, and apparent lack of a massivecompanion tentatively suggest that it is an Anomalous X-ray Pulsar (AXP). Anisothermal blackbody model yields an acceptable spectral fit but the inferredsource radius is much less than that of a neutron star, a result that has alsobeen found for other AXPs. We analyze the X-ray spectra with more complexmodels including a model that assumes the pulsar is a strongly magnetizedneutron star (``magnetar'') with a light element atmosphere. We conclude thatthe observed X-ray emission cannot be explained as global surface emissionarising from the surface of a cooling neutron star or magnetar. The emissionlikely arises in one or more localized regions (``hot spots'') covering a smallfraction of the surface. We discuss these new results in the context of bothaccretion and magnetar interpretations for the X-ray emission.Comment: 14 pages, 5 figures; to appear in Ap
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