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arXiv 0711.4010astro-ph
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两个小麦哲伦云X射线双星-- SXP46 .6和SXP6 .85的光学和X射线变率

Optical and X-ray variability of two Small Magellanic Cloud X-ray binary pulsars - SXP46.6 and SXP6.85

K. E. McGowan, M. J. Coe, M. P. E. Schurch, R. H. D. Corbet, J. L. Galache, A. Udalski

摘要:

我们提供了小麦哲伦星云中两颗X射线双星SXP 46.6和SXP 6.85的长期光学和RXTE数据。这两个光源的光学光变曲线在观测的时间跨度上显示出实质性的变化(约0.5-0.8等)。虽然SXP 6.85的光学数据没有显示任何周期性行为,但通过对SXP 46.6的光学测量进行去趋势化,我们发现轨道周期约为137天,与X射线数据的结果一致。从SXP 46.6探测到I型X射线爆发,结合我们在这些时候也看到光学爆发的事实,意味着SXP 46.6是一个高轨道偏心率系统。利用SXP 46.6的同期光谱,我们发现H_α发射线的等效宽度随时间变化,表明星周盘的大小是变化的。通过研究SXP6.85的颜色变化历史,我们发现源变得更红,因为它变亮,这也可以归因于拱星盘的变化。我们没有发现SXP 6.85的X射线和光学数据之间存在任何相关性。对SXP 6.85的观测结果表明,它是一颗低偏心双星,光调制是由于Be现象引起的。

英文摘要:

We present long-term optical and RXTE data of two X-ray binary pulsars in the Small Magellanic Cloud, SXP46.6 and SXP6.85. The optical light curves of both sources show substantial (~0.5-0.8 mag) changes over the time span of the observations. While the optical data for SXP6.85 do not reveal any periodic behaviour, by detrending the optical measurements for SXP46.6 we find an orbital period of ~137 days, consistent with results from the X-ray data. The detection of Type I X-ray outbursts from SXP46.6, combined with the fact that we also see optical outbursts at these times, implies that SXP46.6 is a high orbital eccentricity system. Using contemporaneous optical spectra of SXP46.6 we find that the equivalent width of the H_alpha emission line changes over time indicating that the size of the circumstellar disc varies. By studying the history of the colour variations for SXP6.85 we find that the source gets redder as it brightens which can also be attributed to changes in the circumstellar disc. We do not find any correlation between the X-ray and optical data for SXP6.85. The results for SXP6.85 suggest that it is a low eccentricity binary and that the optical modulations are due to the Be phenomenon.

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