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arXiv 1409.0939astro-ph.SRastro-ph.HE
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VY Scl型类新星双星高、低态X射线观测

X-ray observations of VY Scl type nova-like binaries in the high and low state

P. Zemko, M. Orio, K. Mukai, S. Shugarov

摘要:

在低光态和高光态的X射线中观测到四个VY Scl型类新星系统。我们研究了钱德拉,ROSAT,斯威夫特和朱雀档案观测BZ凸轮,MV Lyr,TT阿里,和V794 Aql。BZ Cam的X射线通量在低状态下较高,但不存在之前文章中假设的超软X射线源(SSS)。在任何其他系统的低电平状态下均未检测到SSS,X射线通量降低2 - 50倍。用碰撞电离平衡的多组分等离子体模型得到了与Swift X射线谱的最佳拟合。用Chandra ACIS-S和HETG光栅获得的TT Ari的高态高分辨光谱显示出丰富的发射线光谱,其中Mg,Si,Ne和S的发射线非常突出。这个光谱的复杂性似乎起源于不止一个区域,或者不止一个单一的物理机制。虽然有几条发射线与吸积流中的冷却流一致,但至少还有一个额外的组成部分。我们讨论了这一组成部分,这可能是在风中产生的系统的起源。我们还研究的可能性,VY Scl系统可能是中间极性,而吸积盘的边界层只在极紫外线发射,部分的X射线通量可能是由于磁驱动的吸积。

英文摘要:

Four VY Scl-type nova-like systems were observed in X-rays during both the low and the high optical states. We examined Chandra, ROSAT, Swift and Suzaku archival observations of BZ Cam, MV Lyr, TT Ari, and V794 Aql. The X-ray flux of BZ Cam is higher during the low state, but there is no supersoft X-ray source (SSS) as hypothesized in previous articles. No SSS was detected in the low state of the any of the other systems, with the X-ray flux decreasing by a factor between 2 and 50. The best fit to the Swift X-ray spectra is obtained with a multi-component model of plasma in collisional ionization equilibrium. The high state high resolution spectra of TT Ari taken with Chandra ACIS-S and the HETG gratings show a rich emission line spectrum, with prominent lines of in Mg, Si, Ne, and S. The complexity of this spectrum seems to have origin in more than one region, or more than one single physical mechanism. While several emission lines are consistent with a cooling flow in an accretion stream, there is at least an additional component. We discuss the origin of this component, which is probably arising in a wind from the system. We also examine the possibility that the VY Scl systems may be intermediate polars, and that while the boundary layer of the accretion disk emits only in the extreme ultraviolet, part of the X-ray flux may be due to magnetically driven accretion.

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