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arXiv 0911.0887astro-ph.HEastro-ph.SRgr-qc
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中子星SAX J1808 .4-3658脉冲振荡的多历元分析

Multi-epoch Analysis of Pulse Shapes from the Neutron Star SAX J1808.4-3658

Sharon M. Morsink, Denis A. Leahy

摘要:

分析了在SAXJ 1808多次爆发过程中探测到的脉冲波形,以约束中子星的质量和半径。我们使用一个热点模型与一个小的散射光组件,以联合拟合数据从两个不同的时代,限制下,恒星的质量和半径和二进制的倾角不改变从时代到时代。描述光斑位置、发射率和黑体与康普顿辐射的相对分数的所有其他参数都允许随时间变化。利用i&lt;90度的约束条件对1998年“慢衰变”和2002年“爆发末期极大”时期的数据进行联合拟合,得到中子星质量为0.8 M_sun &lt; M &lt; 1.7 M_sun,赤道半径为5 km &lt; R 1.0 M_sun的3 σ置信约束< 13 km. Inclinations as low as 41 degrees are allowed. The best-fit models with M >来自1998年数据与来自2002年和2005年爆发的其他时期的数据的联合拟合的Sun也落在相同的3 σ置信区域内。这个3 sigma置信区间允许各种各样的强子状态方程,与早期的分析(Leahy et al 2008)相比,只有1998年的爆发数据,只允许非常小的恒星。

英文摘要:

The pulse shapes detected during multiple outbursts of SAX J1808 are analyzed in order to constrain the neutron star's mass and radius. We use a hot-spot model with a small scattered-light component to jointly fit data from two different epochs, under the restriction that the star's mass and radius and the binary's inclination do not change from epoch to epoch. All other parameters describing the spot location, emissivity, and relative fractions of blackbody to Comptonized radiation are allowed to vary with time. The joint fit of data from the 1998 "slow decay" and the 2002 "end of outburst maximum" epochs using the constraint i<90 degrees leads to the 3 sigma confidence constraint on the neutron star mass 0.8 M_sun < M < 1.7 M_sun and equatorial radius 5 km < R < 13 km. 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 the 2002 and 2005 outbursts also fall within the same 3 sigma confidence region. This 3 sigma confidence region allows a wide variety of hadronic equations of state, in contrast with an earlier analysis (Leahy et al 2008) of only the 1998 outburst data that only allowed for extremely small stars.

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