低金属丰度致密矮星系J1320 +2155中一个带冕线的IIn型超新星
A type IIn supernova with coronal lines in the low-metallicity compact dwarf galaxy J1320+2155
摘要：
我们报道了在低金属量矮星系J1320+2155中发现的一颗IIn型超新星，氧丰度为12+logO/H = 8.0+/-0.2。这一发现基于SDSS（2008年2月）和3.5米阿帕奇角天文台（2009年2月）相隔一年的光谱，并根据以下观测结果：H β和H α发射线显示出对应于~1600 km/s的气体膨胀速度的宽分量;巴耳末减量非常高：H α/H β通量比大于30，意味着一个非常稠密的环境（>10^7 cm^-3）;而H α的宽光度则缓慢下降，一年中只有1.8倍，典型的IIn型超新星的缓慢光度演化。在SDSS光谱中还可以看到[Fe VII]和[Fe X]的几条弱日冕线，这意味着激波诱导的X射线辐射使激波前的星周介质电离。星系J1320+2155是有史以来第一个被发现的矮星系，它的光谱中有一颗IIn型超新星显示出日冕线。
英文摘要：
We report the discovery of a type IIn supernova in the low-metallicity dwarf galaxy J1320+2155, with an oxygen abundance 12+logO/H = 8.0+/-0.2. This finding is based on SDSS (February 2008) and 3.5m Apache Point Observatory (February 2009) spectra taken one year apart, and on the observations that: the Hbeta and Halpha emission lines show broad components corresponding to gas expansion velocities of ~1600 km/s; the Balmer decrement is exceeedingly high: the Halpha/Hbeta flux ratio, being more than 30, implies a very dense environment (>10^7 cm^-3); and the Halpha broad luminosity decreases slowly, by only a factor of ~1.8 over the course of a year, typical of the slow luminosity evolution of a type IIn supernova. Several weak coronal lines of [Fe VII] and [Fe X] are also seen in the SDSS spectrum, implying ionization of the pre-shock circumstellar medium by shock-induced X-ray emission. The galaxy J1320+2155 is the first dwarf system ever to be discovered with a type IIn supernova exhibiting coronal lines in its spectrum.
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