We present extensive optical observations of a Type?IIn supernova (SN?IIn) 2010jl for the first 1.5?years after its discovery. The UBVRI light curves demonstrated an interesting two-stage evolution during the nebular phase, which almost flatten out after about 90?days from the optical maximum. SN 2010jl has one of the highest intrinsic Hα luminosities ever recorded for an SN?IIn, especially at late phase, suggesting a strong interaction of SN ejecta with the dense circumstellar material (CSM) ejected by the progenitor. This is also indicated by the remarkably strong Balmer lines persisting in the optical spectra. One interesting spectral evolution about SN 2010jl is the appearance of asymmetry of the Balmer lines. These lines can be well decomposed into a narrow component and an intermediate-width component. The intermediate-width component showed a steady increase in both strength and blueshift with time until t ~ 400 days after maximum, but it became less blueshifted at t ~ 500 days, when the line profile appeared relatively symmetric again. Owing to the fact that a pure reddening effect will lead to a sudden decline of the light curves and a progressive blueshift of the spectral lines, we therefore propose that the asymmetric profiles of H lines seen in SN 2010jl are unlikely due to the extinction by newly formed dust inside the ejecta, contrary to the explanation by some early studies. Based on a simple CSM-interaction model, we speculate that the progenitor of SN 2010jl may suffer a gigantic mass loss (~30-50 M ☉) a few decades before explosion. Considering a slow-moving stellar wind (e.g., ~28?km?s–1) inferred for the preexisting, dense CSM shell and the extremely high mass-loss rate (1-2 M ☉ yr–1), we suggest that the progenitor of SN 2010jl might have experienced a red supergiant stage and may explode finally as a post-red supergiant star with an initial mass above 30-40 M ☉.
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机译：我们发现Ij型超新星（SNIIIn）2010jl在发现后的前1.5？年内进行了广泛的光学观测。 UBVRI的光曲线显示出在星云阶段有一个有趣的两阶段演化，在距光学最大值约90天后几乎变平了。 SN 2010jl是有史以来对SN？IIn记录的最高固有Hα发光度之一，尤其是在后期，这表明SN射流与祖先射出的致密周星物质（CSM）有很强的相互作用。这也通过在光谱中持续存在的非常强的巴尔默线来表明。关于SN 2010jl的一个有趣的频谱演变是Balmer线的不对称现象。这些线可以很好地分解为较窄的分量和中等宽度的分量。直到最大后t〜400天时，中等宽度分量的强度和蓝移都随时间稳定增加，但在t〜500天时，线形再次出现相对对称时，其蓝移变小。由于纯粹的变红作用会导致光曲线突然下降并导致光谱线逐渐蓝移，因此我们建议，由于新的消光，SN 2010jl中出现的H线不对称分布不太可能与一些早期研究的解释相反，在喷射器内部形成了灰尘。基于简单的CSM相互作用模型，我们推测SN 2010jl的祖先可能在爆炸前的几十年内遭受巨大的质量损失（〜30-50 M☉）。考虑到先前存在的致密CSM壳和极高的质量损失率（1-2 M☉yr-1）推断出的恒星风缓慢移动（例如〜28？km？s–1），我们建议SN 2010jl的祖先可能经历了红色超巨星阶段，并可能最终以初始质量超过30-40 M as的后红色超巨星爆炸。
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