标题： 双“acct”：与脉动对不稳定模型相匹配的双峰超新星 显示英文标题

标题： Double "acct": a distinct double-peaked supernova matching pulsational pair-instability models

摘要： 我们展示了SN2020acct的多波段数据，SN2020acct是位于约150兆秒差距外NGC2981中的一个双峰包络剥离超新星（SN）。 这两个峰值在时间上是分开的，峰值间隔58个静止框架天数，并且在亮度上有20倍的下降。 第一个峰值明亮（M$_{r}$ = -18.00 $\pm$ 0.02 mag），呈蓝色（g - r = 0.27 $\pm$ 0.03 mag），并显示出与无氢星际物质相互作用的光谱特征。 第二个峰值较暗淡（M$_{r}$ = -17.29 $\pm$ 0.03 mag），光谱上类似于演化的包络剥离SN，具有强烈的混合禁线[Ca II]和[O II]特征。 没有其他已知的双峰SN表现出与SN 2020acct类似的光变曲线。 我们发现，在同一恒星形成区域内于该时间段内发生两次独立超新星的可能性极低，而需要一种难以置信的精确配置才能从单个双星系统产生两次超新星。 我们发现SN2020acct的独特性质与脉动对不稳定（PPI）模型相符，其中初始峰值由喷发物质壳层的碰撞产生，随后不久发生最终爆炸。 一颗拥有72 M$_{\odot}$ 氦核的恒星脉动与双峰光变曲线非常匹配。 该星系的局部环境金属丰度为0.4 Z$_{\odot}$，在此水平下，大质量单一恒星预计不会保留足够的质量来遭遇PPI。 然而，晚期双星合并或低金属丰度区域可能允许所需的核质量。 我们测量了 SN 2020acct 类似事件的发生率为$<3.3\times10^{-8}$Mpc$^{-3}$年$^{-1}$（z = 0.07），即总塌缩核超新星率的不到 0.1%。 显示英文摘要

摘要： We present multi-wavelength data of SN2020acct, a double-peaked stripped-envelope supernova (SN) in NGC2981 at ~150 Mpc. The two peaks are temporally distinct, with maxima separated by 58 rest-frame days, and a factor of 20 reduction in flux between. The first is luminous (M$_{r}$ = -18.00 $\pm$ 0.02 mag), blue (g - r = 0.27 $\pm$ 0.03 mag), and displays spectroscopic signatures of interaction with hydrogen-free circumstellar material. The second peak is fainter (M$_{r}$ = -17.29 $\pm$ 0.03 mag), and spectroscopically similar to an evolved stripped-envelope SNe, with strong blended forbidden [Ca II] and [O II] features. No other known double-peak SN exhibits a light curve similar to that of SN 2020acct. We find the likelihood of two individual SNe occurring in the same star-forming region within that time to be highly improbable, while an implausibly fine-tuned configuration would be required to produce two SNe from a single binary system. We find that the peculiar properties of SN2020acct match models of pulsational pair instability (PPI), in which the initial peak is produced by collisions of shells of ejected material, shortly followed by a terminal explosion. Pulsations from a star with a 72 M$_{\odot}$ helium core provide an excellent match to the double-peaked light curve. The local galactic environment has a metallicity of 0.4 Z$_{\odot}$, a level where massive single stars are not expected retain enough mass to encounter the PPI. However, late binary mergers or a low-metallicity pocket may allow the required core mass. We measure the rate of SN 2020acct-like events to be $<3.3\times10^{-8}$ Mpc$^{-3}$ yr$^{-1}$ at z = 0.07, or <0.1% of the total core-collapse SN rate.