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arXiv 1005.5299astro-ph.HE
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吸积毫秒X射线脉冲星IGR J17511-3057的I型X射线爆发和爆发振荡

Type I X-ray bursts and burst oscillations in the accreting millisecond X-ray pulsar IGR J17511-3057

D. Altamirano, A. Watts, M. Linares, C. B. Markwardt, T. Strohmayer, A. Patruno

摘要:

本文报道了在吸积毫秒X射线脉冲星(AMXP)IGR J17511-3057的10个热核爆发中发现了自旋频率的爆发振荡。爆发振荡特性与持续AMXPs SAX J1808.4-3658和XTE J1814-338的特性一样,与间歇性爆发或非脉冲LMXB的爆发振荡相比是异常的。与SAXJ1808.4 -3658一样,它们在上升阶段而不是尾部显示频率漂移。也有证据表明谐波含量。IGR J17511-3057与其他两个持续爆发相比的不寻常之处在于,在所有爆发中都没有检测到振荡。随着吸积率的下降,爆发变得更亮,它们的上升/衰减时间尺度变得更短,而振荡幅度下降到检测阈值以下:首先在爆发峰值,然后在上升。来自IGR J17511-3057的爆发都没有显示出光球半径膨胀的证据(这可能会抑制振荡幅度),这使我们能够将距离上限设定为6.9 kpc。我们讨论了我们的研究结果的突发振荡机制的模型的影响。

英文摘要:

We report the discovery of burst oscillations at the spin frequency in ten thermonuclear bursts from the accreting millisecond X-ray pulsar (AMXP) IGR J17511-3057. The burst oscillation properties are, like those from the persistent AMXPs SAX J1808.4-3658 and XTE J1814-338, anomalous compared to burst oscillations from intermittent pulsars or non-pulsing LMXBs. Like SAX J1808.4-3658 they show frequency drifts in the rising phase rather than the tail. There is also evidence for harmonic content. Where IGR J17511-3057 is unusual compared to the other two persistent pulsars is that oscillations are not detected throughout all bursts. As accretion rate drops the bursts get brighter and their rise/decay time scales become shorter, while the oscillation amplitude falls below the detection threshold: first in the burst peak and then also in the rise. None of the bursts from IGR J17511-3057 show evidence for photospheric radius expansion (which might be expected to suppress oscillation amplitude) which allow us to set an upper limit to the distance of 6.9 kpc. We discuss the implications of our results for models of the burst oscillation mechanism.

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