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arXiv 1407.1897astro-ph.HE
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4U 1630 - 47在2010年爆发结束时向硬态的延迟转变

A Delayed Transition to the Hard State for 4U 1630-47 at the End of Its 2010 Outburst

John A. Tomsick, Kazutaka Yamaoka, Stephane Corbel, Emrah Kalemci, Simone Migliari, Philip Kaaret

摘要:

在这里,我们报告斯威夫特和朱雀观测接近尾声的爆发从黑洞瞬态4U 1630 - 47和钱德拉观测时,源处于静止状态。4U 1630 - 47在主突结束后约50 d由软态向硬态转变。在这段不寻常的延迟期间,通量持续下降,雨燕的一次测量发现,在2 - 10 keV的光度L = 1.07e35 erg/s,估计距离为10 kpc的软光谱源。虽然这种瞬变通常在L/Ledd = 0.3 - 3%时转变为硬态,其中Ledd是爱丁顿光度,但4U 1630 - 47光谱在L/Ledd = 0.008/M10%(在2 - 10 keV波段测量)时保持柔软,其中M10是黑洞的质量,单位为10个太阳质量。在更宽的0.5 - 200 keV带通范围内的光度估计给出L/Ledd = 0.03/M10%,这仍然比典型的低一个数量级。我们还测量了硬态X射线通量的指数衰减,e-折叠时间为3.39 +/-0.06 d,这比以前测量的软态4U 1630 - 47衰变期间的12 - 15 d要小得多。通过~100 ks的朱雀观测,我们没有看到反射分量的证据,窄铁K α发射线的等效宽度的90%置信限对于窄线<40 eV,对于任何宽度的线<100 eV,这与硬态中几何形状的变化(截短的吸积盘或硬X射线源位置的变化)一致。最后,我们报告了0.5 - 8 keV的光度上限<2e32 erg/s的平静,这是迄今为止测量到的最低值4U 1630 - 47。

英文摘要:

Here we report on Swift and Suzaku observations near the end of an outburst from the black hole transient 4U 1630-47 and Chandra observations when the source was in quiescence. 4U 1630-47 made a transition from a soft state to the hard state ~50 d after the main outburst ended. During this unusual delay, the flux continued to drop, and one Swift measurement found the source with a soft spectrum at a 2-10 keV luminosity of L = 1.07e35 erg/s for an estimated distance of 10 kpc. While such transients usually make a transition to the hard state at L/Ledd = 0.3-3%, where Ledd is the Eddington luminosity, the 4U 1630-47 spectrum remained soft at L/Ledd = 0.008/M10% (as measured in the 2-10 keV band), where M10 is the mass of the black hole in units of 10 solar masses. An estimate of the luminosity in the broader 0.5-200 keV bandpass gives L/Ledd = 0.03/M10%, which is still an order of magnitude lower than typical. We also measured an exponential decay of the X-ray flux in the hard state with an e-folding time of 3.39+/-0.06 d, which is much less than previous measurements of 12-15 d during decays by 4U 1630-47 in the soft state. With the ~100 ks Suzaku observation, we do not see evidence for a reflection component, and the 90% confidence limits on the equivalent width of a narrow iron Kalpha emission line are <40 eV for a narrow line and <100 eV for a line of any width, which is consistent with a change of geometry (either a truncated accretion disk or a change in the location of the hard X-ray source) in the hard state. Finally, we report a 0.5-8 keV luminosity upper limit of <2e32 erg/s in quiescence, which is the lowest value measured for 4U 1630-47 to date.

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