A precursor plateau and pre-maximum [O ii ] emission in the superluminous SN2019szu: a pulsational pair-instability candidate
A precursor plateau and pre-maximum [O ii ] emission in the superluminous SN2019szu: a pulsational pair-instability candidate
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超光速 SN2019szu 中的前驱平台和最大前 [O ii ] 发射：脉动对不稳定性候选者
DOI：
10.1093/mnras/stad3776
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发表时间：
2024
影响因子：
4.8
通讯作者：
Aamer A
中科院分区：
文献类型：
--
作者：
Aamer A
我们对SN 2019 szu进行了详细的研究，SN 2019 szu是一颗I型超亮超新星，atz= 0.213，具有独特的光度和光谱特性。Pan-STARRS和ZTF强制测光显示了一个持续约40天的爆炸前平台。与其他SLSNe显示光球温度随时间下降不同，光学颜色显示在前70天内从15000 K到20000 K的明显温度增加，可能是由光谱中的额外伪连续谱引起的。值得注意的是，光谱显示了一条在最大光之前16天可见的禁止发射线（可能归因于λλ 7320，7330），与明显紧凑的光球不一致。光谱中出现的[Oiii] λ4959、5007和[Oiii] λ4363进一步加强了这一识别。通过与星云光谱模型的比较，我们发现，用密度为的1.25 × 10 - 6的富氧物质可以再现氧线通量和氧线比率。低密度表明是星周起源，但发射线的早期开始要求这种物质在终端爆炸前的最后几个月内被喷射出来，与前体平台的时间一致。与更接近爆炸的密度更大的物质的相互作用可能产生了大约5500焦耳的伪连续谱。我们认为，这一事件是迄今为止最好的候选人之一的脉动对不稳定喷射，早期脉冲提供的低密度材料所需的形成的禁止发射线，和碰撞之间的最后壳的喷射材料产生的爆炸前高原。
We present a detailed study on SN2019szu, a Type I superluminous supernova atz= 0.213 that displayed unique photometric and spectroscopic properties. Pan-STARRS and ZTF forced photometry show a pre-explosion plateau lasting ∼40 d. Unlike other SLSNe that show decreasing photospheric temperatures with time, the optical colours show an apparent temperature increase from ∼15 000 to ∼20 000 K over the first 70 d, likely caused by an additional pseudo-continuum in the spectrum. Remarkably, the spectrum displays a forbidden emission line (likely attributed to λλ7320,7330) visible 16 d before maximum light, inconsistent with an apparently compact photosphere. This identification is further strengthened by the appearances of [Oiii] λλ4959, 5007, and [Oiii] λ4363 seen in the spectrum. Comparing with nebular spectral models, we find that the oxygen line fluxes and ratios can be reproduced with ∼0.25 M⊙of oxygen-rich material with a density of. The low density suggests a circumstellar origin, but the early onset of the emission lines requires that this material was ejected within the final months before the terminal explosion, consistent with the timing of the precursor plateau. Interaction with denser material closer to the explosion likely produced the pseudo-continuum bluewards of ∼5500 Å. We suggest that this event is one of the best candidates to date for a pulsational pair-instability ejection, with early pulses providing the low density material needed for the formation of the forbidden emission line, and collisions between the final shells of ejected material producing the pre-explosion plateau.