论文标题
NGC 925 ULX-3的可变性行为
The variability behavior of NGC 925 ULX-3
论文作者
论文摘要
我们报告了与XMM-Newton和Nustar的迅速目标观察结果的2019 - 2021年监测活动的结果，研究了高度可变的超小X射线源（ULX）NGC 925 ULX ULX-3的光谱和时机行为。我们发现该来源表现出127-128天的周期性，通量通常从1E-13到8E-13 ERGS/s/cm2。我们找不到在2005年首次在Chandra首次观察到NGC 925 ULX-3的时间内发生变化的有力证据，尽管该源可能处于较低的通量状态。我们没有检测到搏动，并且在XMM-Newton Band band band band band band band puls的脉冲中，我们对脉冲分数的最高限制了，而脉冲的脉冲量不一致，而其他脉冲则是其他脉动效果。该源表现出典型的ULX光谱，该光谱在Nustar带中翻转，可以使用两个热组件拟合。这些组件的高温比可能表明缺乏通过磁场级磁场缺乏极端的内盘截断。我们研究了ULX中许多不同模型对许多不同模型的含义，发现该来源的中子恒星的磁场为〜10^12 g可能是合理的。从该来源对脉动的未来检测将允许对此类模型进行进一步的测试和约束。
We report the results of a 2019-2021 monitoring campaign with Swift and associated target-of-opportunity observations with XMM-Newton and NuSTAR, examining the spectral and timing behavior of the highly variable ultraluminous X-ray source (ULX) NGC 925 ULX-3. We find that the source exhibits a 127-128 day periodicity, with fluxes typically ranging from 1e-13 to 8e-13 ergs/s/cm2. We do not find strong evidence for a change in period over the time that NGC 925 ULX-3 has been observed, although the source may have been in a much lower flux state when first observed with Chandra in 2005. We do not detect pulsations, and we place an upper limit on the pulsed fraction of ~40% in the XMM-Newton band, consistent with some previous pulsation detections at low energies in other ULXs. The source exhibits a typical ULX spectrum that turns over in the NuSTAR band and can be fitted using two thermal components. These components have a high temperature ratio that may indicate the lack of extreme inner disk truncation by a magnetar-level magnetic field. We examine the implications for a number of different models for superorbital periods in ULXs, finding that a neutron star with a magnetic field of ~10^12 G may be plausible for this source. The future detection of pulsations from this source would allow for the further testing and constraining of such models.
