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arXiv 1909.03595astro-ph.HE
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来自毫秒X射线脉冲星SAX J1808的NICER热核爆发。4 -3658

A NICER thermonuclear burst from the millisecond X-ray pulsar SAX J1808.4-3658

Peter Bult, Gaurava K. Jaisawal, Tolga Güver, Tod E. Strohmayer, Diego Altamirano, Zaven Arzoumanian, David R. Ballantyne, Deepto Chakrabarty, Jérôme Chenevez, … 展开作者

Peter Bult, Gaurava K. Jaisawal, Tolga Güver, Tod E. Strohmayer, Diego Altamirano, Zaven Arzoumanian, David R. Ballantyne, Deepto Chakrabarty, Jérôme Chenevez, Keith C. Gendreau, Sebastien Guillot, Renee M. Ludlam

摘要:

中子星内部成分探测器(NICER)广泛监测了2019年8月401 Hz毫秒X射线脉冲星SAX J1808.4-3658的爆发。在这封信中,我们报告了一个明亮的氦燃料I型X射线爆发的检测。这是迄今为止用NICER观测到的所有爆发源中最明亮的X射线爆发,其辐射热峰值通量为$(2.3\pm0.1)\times 10^{-7}$ erg/cm^2/s。爆发显示出显着的两个阶段的流量,在$1.0$ keV和$6.7$ keV的发射线,和爆发振荡在已知的脉冲星自旋频率,与$\approx4$ \%分数正弦振幅的演变。我们解释的爆发通量的演变为检测当地爱丁顿限制与氢和氦层的中子星信封。这些发射线可能与Fe有关,这是由于吸积盘对爆发发射的再加工。

英文摘要:

The Neutron Star Interior Composition Explorer (NICER) has extensively monitored the August 2019 outburst of the 401 Hz millisecond X-ray pulsar SAX J1808.4-3658. In this Letter, we report on the detection of a bright helium-fueled Type I X-ray burst. With a bolometric peak flux of $(2.3\pm0.1)\times 10^{-7}$ erg/cm^2/s, this was the brightest X-ray burst among all bursting sources observed with NICER to date. The burst shows a remarkable two-stage evolution in flux, emission lines at $1.0$ keV and $6.7$ keV, and burst oscillations at the known pulsar spin frequency, with $\approx4$\% fractional sinusoidal amplitude. We interpret the burst flux evolution as the detection of the local Eddington limits associated with the hydrogen and helium layers of the neutron star envelope. The emission lines are likely associated with Fe, due to reprocessing of the burst emission in the accretion disk.

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