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arXiv 0704.2255astro-ph
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X射线脉冲星1 E 1207.4-5209的精确定年:一颗诞生时弱磁化的稳定中子星

Precise Timing of the X-ray Pulsar 1E 1207.4-5209: A Steady Neutron Star Weakly Magnetized at Birth

E. V. Gotthelf, J. P. Halpern

摘要:

我们分析了2000-2005年收集的超新星遗迹PKS 1209-51/52中1 E 1207.4-5209的所有X射线计时数据,发现了一个高稳定的自转,其P=424.130451(4)ms,周期导数为(9.6 +/- 9.4)E-17 s/s。这驳斥了先前关于这些数据中存在大量时间不规则性的说法。在偶极自旋下降形式中,周期导数的2 σ上限意味着能量损失率< 1.5E32 ergs/s,表面磁场强度B_p < 3.5E11 G,特征年龄τ> 2400万年。这个τ比剩余年龄大了3个数量级,这就要求脉冲星出生时就在它的当前周期旋转。1 E 1207.4-5209的X射线光度L(bol)~= 2 E33 ergs/s(2kpc),超过了它的自旋下降能量损失,这意味着L(bol)来自剩余冷却,可能部分来自超新星碎片的吸积。对于软X射线谱中的至少一条显著吸收线,B_p的上限足够小,以支持电子回旋模型。这是继Kesteven 79中的PSR J1852+0040之后,第二个可以证明的脉冲星旋转缓慢且具有弱B场的情况。

英文摘要:

We analyze all X-ray timing data on 1E 1207.4-5209 in supernova remnant PKS 1209-51/52 gathered in 2000-2005, and find a highly stable rotation with P=424.130451(4) ms and period derivative of (9.6 +/- 9.4)E-17 s/s. This refutes previous claims of large timing irregularities in these data. In the dipole spin-down formalism, the 2-sigma upper limit on period derivative implies an energy loss rate < 1.5E32 ergs/s, surface magnetic field strength B_p < 3.5E11 G, and characteristic age tau > 24 Myr. This tau exceeds the remnant age by 3 orders of magnitude, requiring that the pulsar was born spinning at its present period. The X-ray luminosity of 1E 1207.4-5209, L(bol) ~= 2E33 ergs/s at 2 kpc, exceeds its spin-down energy loss, implying that L(bol) derives from residual cooling, and perhaps partly from accretion of supernova debris. The upper limit on B_p is small enough to favor the electron cyclotron model for at least one of the prominent absorption lines in its soft X-ray spectrum. This is the second demonstrable case of a pulsar born spinning slowly and with a weak B-field, after PSR J1852+0040 in Kesteven 79.

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