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arXiv 1003.4257astro-ph.HE
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超铝紫外光源的直接探测

Direct Detection of an Ultraluminous Ultraviolet Source

Philip Kaaret, Hua Feng, Diane S. Wong, Lian Tao

摘要:

我们介绍了哈勃太空望远镜在远紫外波段对NGC 6946中与光学星云MF 16相关的超亮X射线源的观测。在FUV中探测到与X射线源重合的点状源和周围的星云。点源的通量为5E-16 erg s^-1 cm^-2 Ang^-1,星云的通量为1.6E-15 erg s^-1 cm^-2 Ang^-1,以1533 Ang表示,假设消光为A_V = 1.54。因此,MF 16似乎是第一个直接检测到的超铝紫外线源(ULUV)。点源的通量与T ~ 30,000 K的黑体一致,可能来自大质量伴星,但这个光谱并不足以产生足够的电离辐射来产生星云HeII通量,需要第二个更热的发射成分。用~ 16,000 K的外盘温度截断的圆盘黑体光谱提供了对FUV、B、V、I和HeII通量的充分拟合,并且可以产生所需的电离辐射。还需要进行更多的观测,以确定放射源的物理性质。

英文摘要:

We present Hubble Space Telescope observations in the far UV of the ultraluminous X-ray source in NGC 6946 associated with the optical nebula MF 16. Both a point-like source coincident with the X-ray source and the surrounding nebula are detected in the FUV. The point source has a flux of 5E-16 erg s^-1 cm^-2 Ang^-1 and the nebula has a flux of 1.6E-15 erg s^-1 cm^-2 Ang^-1, quoted at 1533 Ang and assuming an extinction of A_V = 1.54. Thus, MF 16 appears to host the first directly detected ultraluminous UV source (ULUV). The flux of the point-like source is consistent with a blackbody with T ~ 30,000 K, possibly from a massive companion star, but this spectrum does not create sufficient ionizing radiation to produce the nebular HeII flux and a second, hotter emission component would be required. A multicolor disk blackbody spectrum truncated with an outer disk temperature of ~16,000 K provides an adequate fit to the FUV, B, V, I, and HeII fluxes and can produce the needed ionizing radiation. Additional observations are required to determine the physical nature of the source.

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