6533b85bfe1ef96bd12bbf13
RESEARCH PRODUCT
XMM-Newton detects a relativistically broadened iron line in the spectrum of the ms X-ray pulsar SAX J1808.4-3658
M. T. MennaR. IariaAlessandro PapittoLuciano BurderiAlessandro RiggioN. R. RobbaAntonino D'aiT. Di Salvosubject
PhysicsAstrophysics::High Energy Astrophysical PhenomenaAstrophysics (astro-ph)accretion accretion disks line: profiles stars: pulsars: individual: SAX J1808.4-3658 relativity X-rays: binariesFOS: Physical sciencesAstronomy and AstrophysicsAstrophysicsRadiusAstrophysics::Cosmology and Extragalactic AstrophysicsAstrophysicssymbols.namesakeNeutron starSettore FIS/05 - Astronomia E AstrofisicaSpace and Planetary ScienceMillisecond pulsarIonizationsymbolsAstrophysics::Solar and Stellar AstrophysicsEmission spectrumAstrophysics::Earth and Planetary AstrophysicsDoppler effectAstrophysics::Galaxy AstrophysicsX-ray pulsarLine (formation)description
We report on a 63-ks long XMM-Newton observation of the accreting millisecond pulsar SAX J1808.4-3658 during the latest X-ray outburst which started on September 21st 2008. The pn spectrum shows a highly significant emission line in the energy band where the iron K-alpha line is expected, and which we identify as emission from neutral (or mildly ionized) iron. The line profile appears to be quite broad (more than 1 keV FWHM) and asymmetric; the most probable explanation for this profile is Doppler and relativistic broadening from the inner accretion disc. From a fit with a diskline profile we find an inner radius of the disc of 8.7^(+3.7)_(-2.7) R_g, corresponding to 18.0^(+7.6)_(-5.6) km for a 1.4 Msun neutron star. The disc therefore appears truncated inside the corotation radius (31 km for SAX J1808.4-3658) in agreement with the fact that the source was still showing pulsations during the XMM-Newton observation.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2008-12-05 |