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arXiv 1009.4392astro-ph.HE
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用XMM-牛顿数据研究中等极性EX Hya的轨道和自旋相位分辨光谱

Orbital and Spin Phase-Resolved Spectroscopy of the Intermediate Polar EX Hya Using XMM-Newton Data

Y. Pekon, S. Balman

摘要:

我们提出了第一次轨道相位分辨光谱的中间极性(IP),EX Hya,连同自旋相位分辨光谱在两个不同的时代使用X射线多镜任务,欧洲光子成像相机(pn仪器)。我们发现两个时期的源具有相同的X射线光度,为$\sim$ 6.5 $\times$ 10 $^{31}$ erg s $^{-1}$。我们检测光谱之间的变化,2000年和2003年的观测源。我们拟合光谱使用中性氢吸收模型与或不覆盖分数与高斯发射线,两个碰撞平衡等离子体发射模型(MEKAL)和冷却流等离子体发射模型(VMCFLOW)。我们发现三种发射成分中的两种($kT$ =0.6-0.8 keV和$kT$ =1.3-1.7 keV)由MEKAL模型拟合的数据在自旋和轨道相位上以及在两个不同的时期上几乎是恒定的,当根据轨道和自旋相位折叠数据时,归一化与通量成正比,这表明轻微的变化可能是由于掩星由VMCFLOW模拟的发射在自旋和轨道阶段发生变化,2000年和2003年的观测揭示了两个不同的温度范围(分别为3-33和8-61 keV),模拟了吸积柱中的激波区。随着等离子体温度的升高,自旋谱的最大值与最小值之比和轨道谱的最大值与最小值之比都增大,表明在轨道周期和自旋周期的最小相位谱都变硬。在2003年的观测中,一个6.4 keV的荧光铁发射线存在于轨道最小值的相位范围从0.9到1.3,否则它是不存在的。这表明,有来自光盘的反射,最有可能是来自吸积撞击区的一个大凸起。

英文摘要:

We present for the first time orbital phase-resolved spectra of an intermediate polar (IP), EX Hya, together with the spin phase-resolved spectra during two different epochs using the X-ray Multi-Mirror Mission, European Photon Imaging Camera (pn instrument). We find that the source at the two epochs has the same X-ray luminosity of $\sim$ 6.5 $\times$ 10$^{31}$ erg s$^{-1}$. We detect spectral variations between the 2000 and 2003 observations of the source. We fitted the spectrum using a neutral hydrogen absorption model with or without covering fraction together with Gaussians for emission lines, two collisional equilibrium plasma emission models (MEKAL) and a cooling-flow plasma emission model (VMCFLOW). We find that two of the three emission components ($kT$=0.6-0.8 keV and $kT$=1.3-1.7 keV) fitted by the MEKAL models are almost constant over the spin and orbital phases and also over the two different epochs with the normalisation varying directly proportional to the flux when the data are folded according to the orbital and spin phase indicating that the slight variation may be due to occultation. The emission modeled by the VMCFLOW changes over the spin and orbital phases and the 2000 and 2003 observations reveal two different ranges of temperatures (3-33 and 8-61 keV respectively) that model the shock zone in the accretion column/s. The ratios of the spin maximum to minimum and the orbital maximum to minimum spectra along with the increase in the plasma temperatures indicate that the spectrum gets harder in the minimum phases of both orbital and spin periods. In the 2003 observation, a 6.4 keV fluorescent Fe emission line is present at the orbital minima in a range of phases from 0.9 to 1.3 and it is absent otherwise. This indicates that there is reflection from the disc most likely from a large bulge at the accretion impact zone.

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