We present radio and X-ray observations of the nearby SN IIb 2013df in NGC 4414 from 10 to 250 days after the explosion. The radio emission showed a peculiar steep-to-shallow spectral evolution. We present a model in which inverse Compton cooling of synchrotron emitting electrons can account for the observed spectral and light curve evolution. A significant mass-loss rate, yr?1 for a wind velocity of 10 km s?1, is estimated from the detailed modeling of radio and X-ray emission, which are primarily due to synchrotron and bremsstrahlung, respectively. We show that SN 2013df is similar to SN 1993J in various ways. The shock wave speed of SN 2013df was found to be average among the radio supernovae; . We did not find any significant deviation from smooth decline in the light curve of SN 2013df. One of the main results of our self-consistent multiband modeling is the significant deviation from energy equipartition between magnetic fields and relativistic electrons behind the shock. We estimate . In general for SNe IIb, we find that the presence of bright optical cooling envelope emission is linked with free–free radio absorption and bright thermal X-ray emission. This finding suggests that more extended progenitors, similar to that of SN 2013df, suffer from substantial mass loss in the years before the supernova.
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机译：我们展示了爆炸后10到250天在NGC 4414中附近的SN IIb 2013df的无线电和X射线观测结果。无线电发射显示出奇特的从陡峭到浅的光谱演变。我们提出了一个模型，其中同步加速器发射电子的逆康普顿冷却可以解释观察到的光谱和光曲线的演变。根据无线电和X射线发射的详细模型，估计出风速为10 km s？1时，明显的质量损失率yr？1，这主要是由于同步加速器和致辐射。我们显示SN 2013df在各种方面类似于SN 1993J。 SN 2013df的冲击波速度在射电超新星中是平均的; 。我们没有发现SN 2013df的光曲线平滑下降有任何明显的偏差。我们自洽的多频带建模的主要结果之一是，磁场与电击后的相对论电子之间的能量分配显着偏离。我们估计。通常，对于SNe IIb，我们发现明亮的光学冷却包络线发射与自由自由无线电吸收和明亮的X射线热发射有关。这一发现表明，与SN 2013df相似的更广泛的祖细胞在超新星出现之前的几年中遭受了巨大的质量损失。
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