6533b82afe1ef96bd128b84b

RESEARCH PRODUCT

A relativistically broadened iron line from an Accreting Millisecond Pulsar

A. PapittoT. Di SalvoA. D’aìR. IariaL. BurderiA. RiggioM. T. MennaA. ComastriL. AngeliniM. Cappi

subject

PhysicsrelativityAstrophysics::High Energy Astrophysical PhenomenaX-ray binaryAstronomyAstrophysics::Cosmology and Extragalactic AstrophysicsRadiusAstrophysicsstars: pulsars: individual: SAX J1808.4-3658accretion accretion diskprofiles; relativity; stars: pulsars: individual: SAX J1808.4-3658; X-rays: binaries; Physics and Astronomy (all) [accretion accretion disks; line]X-rays: binarieNeutron starPhysics and Astronomy (all)Pulsarline: profileMillisecond pulsarAstrophysics::Solar and Stellar AstrophysicsAstrophysics::Earth and Planetary AstrophysicsEmission spectrumAstrophysics::Galaxy AstrophysicsLine (formation)Doppler broadening

description

The capabilities of XMM-Newton have been fully exploited to detect a broadened iron Kα emission line from the 2.5 ms Accreting Millisecond Pulsar, SAX J1808.4-3658. The energy of the transition is compatible with fluorescence from neutral/lowly ionized iron. The observed large width (FWHM more than 1 keV) can be explained through Doppler and relativistic broadening from the inner rings of an accretion disc close to the NS. From a fit of the line shape with a diskline model we obtain an estimate of the inner disc radius of 18.0-5.6+7.6km for a 1.4 M⊙ neutron star. The disc is therefore truncated inside the corotation radius (31 km for SAX J1808.4-3658), in agreement with the observation of coherent pulsations. From our estimate of the inner disc radius, we infer that the magnetic field of the neutron star is in the range 1-5×108G. © 2010 American Institute of Physics.

10.1063/1.3475360http://hdl.handle.net/10447/229368