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Proton Cyclotron Lines in Thermal Magnetar Spectra S. Zane, R. Turolla, L. Stella and A. Treves Mullard Space Science Laboratory UCL, University of Padova,

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Presentation on theme: "Proton Cyclotron Lines in Thermal Magnetar Spectra S. Zane, R. Turolla, L. Stella and A. Treves Mullard Space Science Laboratory UCL, University of Padova,"— Presentation transcript:

1 Proton Cyclotron Lines in Thermal Magnetar Spectra S. Zane, R. Turolla, L. Stella and A. Treves Mullard Space Science Laboratory UCL, University of Padova, Roma Observatory, University of Milano In the last few years increasing observational evidence gathered in favour of the existence of ultra-magnetized neutron stars (NSs), with surface field >10 14 G. Magnetars were first hypothesized by Thompson and Duncan (1993), who realized that strong convective motions during the core collapse can strongly amplify the seed magnetic field. In magnetars magneto-dipolar radiation will cause rapid spin-down at a rate ~ (B/10 14 G) 2 /P ss -1, and it has been the detection of a secular spin down of the same order in two Soft  -repeaters (SGRs) that for the first time suggested the association of these sources with ultra- magnetized NSs. Besides their bursting activity, SGRs show also persistent X-ray emission with L~ erg/s and the possible presence of a thermal component at KT~0.5 keV. In the magnetar model, this is believed to originate from the star surface which is kept hot by the dissipation of the B-field. Magnetars have been also invoked to explain another enigmatic class of galactic high energy sources, the Anomalous X-ray pulsars (AXPs). AXPs have periods in a very narrow range (P~6-12 s) luminosities similar to SGRs and show no evidence of a massive binary companion. They show a stable spin period evolution with a long term spin down trend. The emission of AXPs has a thermal component at ~0.5 keV and, like SGRs, some of them are associated with a supernova remnant. The many similarities between AXPs and SGRs strengthen the idea that the two classes of sources are powered by the same mechanism, dissipation of a super-strong B-field in a magnetar. Artist impression of a magnetar Chandra and XMM-Newton can already provide the required energy resolution to allow for a detailed comparison with theoretical models and to probe the existence of such huge fields. Detailed radiative transfer calculations are therefore needed. Following Zane, Turolla and Treves (2000), we modelled thermal emission from the NS surface, exploring the ranges G


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