Multi-epoch Analysis of Pulse Shapes from the Neutron Star SAX J1808.4-3658 - Astrophysics > High Energy Astrophysical PhenomenaReportar como inadecuado




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Abstract: The pulse shapes detected during multiple outbursts of SAX J1808 are analyzedin order to constrain the neutron star-s mass and radius. We use a hot-spotmodel with a small scattered-light component to jointly fit data from twodifferent epochs, under the restriction that the star-s mass and radius and thebinary-s inclination do not change from epoch to epoch. All other parametersdescribing the spot location, emissivity, and relative fractions of blackbodyto Comptonized radiation are allowed to vary with time. The joint fit of datafrom the 1998 -slow decay- and the 2002 -end of outburst maximum- epochs usingthe constraint i<90 degrees leads to the 3 sigma confidence constraint on theneutron star mass 0.8 M sun < M < 1.7 M sun and equatorial radius 5 km < R < 13km. Inclinations as low as 41 degrees are allowed. The best-fit models with M >1.0 M sun from joint fits of the 1998 data with data from other epochs of the2002 and 2005 outbursts also fall within the same 3 sigma confidence region.This 3 sigma confidence region allows a wide variety of hadronic equations ofstate, in contrast with an earlier analysis Leahy et al 2008 of only the 1998outburst data that only allowed for extremely small stars.



Autor: Sharon M. Morsink, Denis A. Leahy

Fuente: https://arxiv.org/







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