IIn型超新星2011 ht的异常时间和光谱演化
The Unusual Temporal and Spectral Evolution of the Type IIn Supernova 2011ht
摘要：
本文报道了UGC 5460中奇特的I In型超新星（SN）2011 ht的极早期紫外-光学光度和光谱观测结果。紫外线观测上升到峰值是有史以来第二次记录到的IIn型SN，也是迄今为止最完整的。SN最初被归类为SN冒名顶替者，在\sim 55天内缓慢上升至M_V \sim -17。与从第一次观测到峰值的v波段光变曲线中的\sim 2量级增加相反，UV通量增加了>7个量级。光谱主要是强的，巴耳末发射与窄峰（FWHM \sim 600 km/s），非常广泛的不对称翼（FWHM \sim 4200 km/s），蓝移吸收（\sim 300 km/s）叠加在一个强的蓝色连续。UV光谱主要由Fe II、Mg II、Si II和Si III吸收线组成，吸收线被\sim 1500 km/s加宽。合并X射线观测表明L_（0.2-10）=（1.0+/-0.2 x10 ^（39）erg/s）。SN 2011 ht的一些特性类似于SN冒名顶替者，而其他特性则与IIn型SNe相当。早期的光谱显示出明亮的蓝色变星在最大值和巨大爆发期间的典型特征。然而，在以前的SN冒名顶替者中没有观察到与强UV通量相结合的宽发射轮廓。绝对星等和能量（前112天约为2.5x10^（49）尔格）让人联想到正常的II型超新星，但光谱是密集风。我们认为，形成这种不寻常的轮廓的机制可能是一个冲击波与一个物质壳相互作用，这个物质壳是在SN发现前一年喷射出来的。
英文摘要：
We present very early UV to optical photometric and spectroscopic observations of the peculiar Type IIn supernova (SN) 2011ht in UGC 5460. The UV observations of the rise to peak are only the second ever recorded for a Type IIn SN and are by far the most complete. The SN, first classified as a SN impostor, slowly rose to a peak of M_V \sim -17 in \sim55 days. In contrast to the \sim2 magnitude increase in the v-band light curve from the first observation until peak, the UV flux increased by >7 magnitudes. The optical spectra are dominated by strong, Balmer emission with narrow peaks (FWHM\sim600 km/s), very broad asymmetric wings (FWHM\sim4200 km/s), and blue shifted absorption (\sim300 km/s) superposed on a strong blue continuum. The UV spectra are dominated by FeII, MgII, SiII, and SiIII absorption lines broadened by \sim1500 km/s. Merged X-ray observations reveal a L_(0.2-10)=(1.0+/-0.2)x10^(39) erg/s. Some properties of SN 2011ht are similar to SN impostors, while others are comparable to Type IIn SNe. Early spectra showed features typical of luminous blue variables at maximum and during giant eruptions. However, the broad emission profiles coupled with the strong UV flux have not been observed in previous SN impostors. The absolute magnitude and energetics (~2.5x10^(49) ergs in the first 112 days) are reminiscent of normal Type IIn SN, but the spectra are of a dense wind. We suggest that the mechanism for creating this unusual profile could be a shock interacting with a shell of material that was ejected a year before the discovery of the SN.
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