论文标题
奇特的Ca-rich SN 2019EHK：来自低质量剥离的祖细胞的IIB型核心折叠超新星的证据
The peculiar Ca-rich SN 2019ehk: Evidence for a Type IIb core-collapse supernova from a low mass stripped progenitor
论文作者
论文摘要
附近Galaxy M100中奇特的“ Ca-rich” SN 2019EHK的性质尚不清楚。它的起源被认为是剥离的核心折叠超新星或热核氦爆炸事件。在这里，我们介绍了从峰光中以$ \ 280 $ $ \ 280 $的天数获得的瞬时光度法。使用光度法来执行同时的卵形相光谱的准确通量校准，我们测量$（0.19-1.08）\ times10^{38} $ erg s $^s $^{ - 1} $（-1} $} $（0.19-1.08）\ times10^{38} $（ca ii）的光度视线沿线的不确定灭绝。我们使用这些测量结果来得出合成氧质量为$ \ of0.004-0.069 $ m $ _ \ odot $的下限。氧气质量是核心折叠超新星的祖细胞质量的敏感示踪剂，我们的估计与非常低的质量核心核心的爆炸相一致，$ 1.45-1.5 $ m $ _ \ odot $，对应于$ \ $ \ \ \ \ \ \ \ odot $的核心质量。我们介绍了瞬时的高质量光光谱，并在早期（“闪光灯”）和光谱相光谱中介绍了氢的特征，这表明在爆炸时，在祖细胞中存在$ \ gtrsim0.02 $ m $ _ \ odot $。 The presence of H, together with the large [Ca II]/[O I] ratio ($\approx10-15$) in the nebular phase is consistent with SN 2019ehk being a Type IIb core-collapse supernova from a stripped low mass ($\approx9-9.5$ M$_\odot$) progenitor, similar to the Ca-rich SN IIb iPTF 15eqv.这些结果提供了证据表明，在恒星形成环境中，剥离的低质量祖细胞的一类可能的“ Ca-rich”核心 - 循环超新星与旧环境中的热核Ca-rich间隙瞬变不同。
The nature of the peculiar `Ca-rich' SN 2019ehk in the nearby galaxy M100 remains unclear. Its origin has been debated as either a stripped core-collapse supernova or a thermonuclear helium detonation event. Here, we present very late-time photometry of the transient obtained with the Keck I telescope at $\approx280$ days from peak light. Using the photometry to perform accurate flux calibration of a contemporaneous nebular phase spectrum, we measure an [O I] luminosity of $(0.19-1.08)\times10^{38}$ erg s$^{-1}$ and [Ca II] luminosity of $(2.7-15.6)\times10^{38}$ erg s$^{-1}$ over the range of the uncertain extinction along the line of sight. We use these measurements to derive lower limits on the synthesized oxygen mass of $\approx0.004-0.069$ M$_\odot$. The oxygen mass is a sensitive tracer of the progenitor mass for core-collapse supernovae, and our estimate is consistent with explosions of very low mass CO cores of $1.45-1.5$ M$_\odot$, corresponding to He core masses of $\approx1.8-2.0$ M$_\odot$. We present high quality peak light optical spectra of the transient and highlight features of hydrogen in both the early (`flash') and photospheric phase spectra, that suggest the presence of $\gtrsim0.02$ M$_\odot$ of hydrogen in the progenitor at the time of explosion. The presence of H, together with the large [Ca II]/[O I] ratio ($\approx10-15$) in the nebular phase is consistent with SN 2019ehk being a Type IIb core-collapse supernova from a stripped low mass ($\approx9-9.5$ M$_\odot$) progenitor, similar to the Ca-rich SN IIb iPTF 15eqv. These results provide evidence for a likely class of `Ca-rich' core-collapse supernovae from stripped low mass progenitors in star forming environments, distinct from the thermonuclear Ca-rich gap transients in old environments.
