[论文解读] From Discovery to the First Month of the Type II Supernova 2023ixf: High and Variable Mass Loss in the Final Year before Explosion

D. Hiramatsu, D. Tsuna+23 more|arXiv (Cornell University)|Jul 6, 2023

Gamma-ray bursts and supernovae参考文献 118被引用 5

一句话总结

本研究对在爆发后一天内被发现的II型超新星SN 2023ixf进行了多波段观测，揭示了其在爆发前一年内存在高且可变的质量损失。通过光曲线建模，该研究对连续与爆发式质量损失情景进行了约束，发现爆发前约一年内存在0.1–1.0 M☉ yr⁻¹的连续损失，或0.3–1.0 M☉的爆发式损失，周围介质延伸至∼(3–7)×10¹⁴ cm，表明存在致密且紧凑的CSP相互作用。

ABSTRACT

We present the discovery of the Type II supernova SN 2023ixf in M101 and follow-up photometric and spectroscopic observations, respectively, in the first month and week of its evolution. Our discovery was made within a day of estimated first light, and the following light curve is characterized by a rapid rise ($\approx5$ days) to a luminous peak ($M_V\approx-18.2$ mag) and plateau ($M_V\approx-17.6$ mag) extending to $30$ days with a fast decline rate of $\approx0.03$ mag day$^{-1}$. During the rising phase, $U-V$ color shows blueward evolution, followed by redward evolution in the plateau phase. Prominent flash features of hydrogen, helium, carbon, and nitrogen dominate the spectra up to $\approx5$ days after first light, with a transition to a higher ionization state in the first $\approx2$ days. Both the $U-V$ color and flash ionization states suggest a rise in the temperature, indicative of a delayed shock breakout inside dense circumstellar material (CSM). From the timescales of CSM interaction, we estimate its compact radial extent of $\sim(3-7) imes10^{14}$ cm. We then construct numerical light-curve models based on both continuous and eruptive mass-loss scenarios shortly before explosion. For the continuous mass-loss scenario, we infer a range of mass-loss history with $0.1-1.0\,M_\odot\,{ m yr}^{-1}$ in the final $2-1$ yr before explosion, with a potentially decreasing mass loss of $0.01-0.1\,M_\odot\,{ m yr}^{-1}$ in $\sim0.7-0.4$ yr toward the explosion. For the eruptive mass-loss scenario, we favor eruptions releasing $0.3-1\,M_\odot$ of the envelope at about a year before explosion, which result in CSM with mass and extent similar to the continuous scenario. We discuss the implications of the available multiwavelength constraints obtained thus far on the progenitor candidate and SN 2023ixf to our variable CSM models.

研究动机与目标

• 理解II型超新星SN 2023ixf前身星在爆发前一年的质量损失历史。
• 确定观测到的光曲线与光谱演化是否与连续或爆发式质量损失一致。
• 从激波爆发与相互作用 timescales 出发，约束周围介质（CSM）的性质，包括质量与径向范围。
• 通过连续与爆发式质量损失情景对超新星光曲线进行建模，以识别最可能的前身星演化路径。
• 评估多波段约束对前身星候选体及SN 2023ixf周围CSP环境的影响。

提出的方法

• 利用多台望远镜与仪器，对SN 2023ixf自发现起至爆发后30天进行测光与光谱监测。
• 通过分析U-V色指数演化与闪光电离态，推断温度变化与激波爆发时间。
• 基于连续质量损失与爆发式质量损失情景的数值模拟，对光曲线进行建模。
• 假设激波为恒定速度模型，从CSP相互作用 timescale 估算CSP的径向范围。
• 使用MESA与emcee对光曲线模型进行拟合，以约束质量损失速率与爆发能量。
• 利用档案数据与巡天数据（如ATLAS、PS1、ZTF、NEOWISE）识别前身星的变异性与爆发前质量损失。

Figure 1: Left : last nondetection ( top ) and discovery ( bottom ) images taken by the Itagaki Astronomical Observatory. The red circle marks the position of SN 2023ixf. Right : color-composite ( $griz$ -band) image of SN 2023ixf and its host galaxy M101 taken by the Fred Lawrence Whipple Observato

实验结果

研究问题

• RQ1 SN 2023ixf在爆发前一年内的质量损失性质与 timescale 是什么？
• RQ2 观测到的光曲线快速上升与平台特征，最合理的解释是连续质量损失还是爆发事件？
• RQ3 与超新星激波相互作用的周围介质（CSM）的径向范围与质量是多少？
• RQ4 观测到的闪光电离态与色指数演化如何约束激波爆发与温度演化？
• RQ5 CSP性质对前身星演化状态与最终质量损失历史有何影响？

主要发现

• 光曲线在约5天内快速上升至峰值绝对星等MV ≈ -18.2 mag，随后在30天内保持在MV ≈ -17.6 mag的平台期，衰减速率约为0.03 mag day⁻¹。
• U-V色指数演化显示上升阶段向蓝端移动，平台期则向红端移动，表明温度先升高后冷却。
• H、He、C与N的闪光特征在约5天内主导光谱，且在前2天内迅速过渡至更高电离态，表明在致密CSP中激波爆发存在延迟。
• CSP相互作用 timescale 暗示CSP具有约(3–7)×10¹⁴ cm的紧凑径向范围，与爆发前致密质量损失一致。
• 对于连续质量损失，推断的损失速率在最后2–1年内为0.1至1.0 M☉ yr⁻¹，最后0.7–0.4年内可能下降至0.01–0.1 M☉ yr⁻¹。
• 对于爆发式质量损失，模型更支持约一年前爆发释放0.3–1.0 M☉的包层物质，形成质量与范围与连续情景相似的CSP。

Figure 2: Left : pre-explosion differential flux measurements at the SN 2023ixf position in the ZTF g,r,i bands; ATLAS c,o bands; and WISE W1,W2 bands. Error bars denote $1\sigma$ uncertainties, and filled and open symbols are used for detections and $5\sigma$ limits, respectively. No significant va