NUSTAR, XMM-NEWTON, AND SUZAKU OBSERVATIONS OF THE ULTRALUMINOUS X-RAY SOURCE HOLMBERG II X-1-猫眼课题宝

DOI：

10.1088/0004-637x/806/1/65

发表时间：

2015-03

期刊：

The Astrophysical Journal

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

D. Walton;M. Middleton;V. Rana;Jonathan M. Miller;F. Harrison;A. Fabian;M. Bachetti;M. Bachetti;D. Barret;D. Barret;S. Boggs;F. Christensen;W. Craig;F. Fuerst;B. Grefenstette;C. Hailey;K. Madsen;D. Stern;Will Zhang

我们介绍了由NuSTAR、XMM-牛顿和Suzaku于2013年9月对明亮的超发光X射线源(ULX)Holmberg II X-1进行的第一次0.3-25.0keV的宽带X射线观测。NuSTAR的数据提供了10keV以上Holmberg II X-1的第一次观测，并揭示了非常陡峭的高能谱，类似于NuSTAR迄今观测到的其他ULXs。这些观测进一步证明，ULX呈现出在银河系黑洞双星中不常见的光谱状态。与其他来源的比较表明，Holmberg II X-1以其爱丁顿吸积速率的很高比例进行吸积，并可能超过它。软X射线能谱(Ekev)似乎由两个类黑体发射成分主导，其中较热的成分可能与吸积盘有关。然而，所有简单的圆盘模型都低估了∼10keV以上的NuSTAR数据，并在所探测的最高能量处需要额外的发射成分，这意味着NuSTAR数据不会随着维恩谱的消失而消失。我们研究了这样一个额外的高能发射分量的物理起源，并倾向于一种假设，即多余的电子是由康普顿散射引起的，这些电子具有一些类似于银河系双星中看到的非常高的状态的性质。从这些历元推算出的宽带0.325.0keV光度为：L X=(8.1±0.1)×1039？gT；erg S−1，这是Holmberg II X-1的典型特征，这个通量的大部分(∼90%)在10keV以下发射。

We present the first broadband 0.3–25.0 keV X-ray observations of the bright ultraluminous X-ray source (ULX) Holmberg II X-1, performed by NuSTAR, XMM-Newton, and Suzaku in 2013 September. The NuSTAR data provide the first observations of Holmberg II X-1 above 10 keV and reveal a very steep high-energy spectrum, similar to other ULXs observed by NuSTAR to date. These observations further demonstrate that ULXs exhibit spectral states that are not typically seen in Galactic black hole binaries. Comparison with other sources implies that Holmberg II X-1 accretes at a high fraction of its Eddington accretion rate and possibly exceeds it. The soft X-ray spectrum ( E keV) appears to be dominated by two blackbody-like emission components, the hotter of which may be associated with an accretion disk. However, all simple disk models under-predict the NuSTAR data above ∼10 keV and require an additional emission component at the highest energies probed, implying the NuSTAR data does not fall away with a Wien spectrum. We investigate physical origins for such an additional high-energy emission component and favor a scenario in which the excess arises from Compton scattering in a hot corona of electrons with some properties similar to the very high state seen in Galactic binaries. The observed broadband 0.3–25.0 keV luminosity inferred from these epochs is L X = ( 8.1 ± 0.1 ) × 10 39 ?> erg s−1, typical for Holmberg II X-1, with the majority of this flux (∼90%) emitted below 10 keV.

NUSTAR, XMM-NEWTON, AND SUZAKU OBSERVATIONS OF THE ULTRALUMINOUS X-RAY SOURCE HOLMBERG II X-1

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