扩展2002es型Ia超新星的参数空间：关于暗弱天体ASASSN-20jq / SN 2020qxp
Expanding the parameter space of 2002es-like type Ia supernovae: on the underluminous ASASSN-20jq / SN 2020qxp
AI总结：
本研究报道了暗弱Ia型超新星ASASSN-20jq/SN 2020qxp，其低光度但光变曲线下降速率正常，光谱特征表明高密度白矮星经历偏心延迟爆轰，被归类为2002es型异质参数空间的极端候选体。
摘要：
我们展示了特殊Ia型超新星ASASSN-20jq/SN 2020qxp的光学测光和光谱观测。它是一个低光度天体，峰值绝对星等为$M_B=-17.1\pm0.5$等。尽管其光度较低，其峰值后光变曲线下降速率（$\Delta m_{15}(B)=1.35\pm0.09$等）和颜色-拉伸参数（sBV>0.82）与正常SNe Ia相似，使其在光度-宽度和光度-颜色-拉伸关系中成为离群点。早期光变曲线表明在爆炸后的前1.4天内存在一个“凸起”。ASASSN-20jq合成了低放射性$^{56}$Ni质量，为$0.09\pm0.01M_\odot$。近最大光光谱显示出强烈的Si II吸收线，表明其光球层比正常SNe Ia更冷，但缺乏Ti II吸收线。存在异常强的O I $\lambda$7773和Ca II近红外三重态吸收特征。星云光谱显示出强烈的窄禁线[Ca II] $\lambda\lambda$7291,7324双线发射，这在SNe Ia中很少见，除非在某些Iax型事件中。观察到[O I] $\lambda\lambda$6300,6364双线发射的边缘探测，这极为罕见。[Ca II]和[O I]线均红移约$\sim2000$ km/s。还观察到一条强的[Fe II] $\lambda$7155发射线，具有倾斜顶部轮廓，与[Fe II] $\lambda$16433轮廓相同。这些不对称的[Fe II]轮廓和红移的[Ca II]和[O I]发射表明，一个高中心密度的白矮星前身星经历了偏心延迟爆轰爆炸机制，在爆燃和爆轰阶段产生了大致等量的$^{56}$Ni。这将ASASSN-20jq与正常和亚光度SNe Ia区分开来。ASASSN-20jq的光变曲线和光谱与任何单一的SNe Ia子类都不完全吻合，但与2002es型天体有相似之处。因此，我们将其作为2002es型SNe Ia异质参数空间中的一个极端候选体。
英文摘要：
We present optical photometric and spectroscopic observations of the peculiar Type Ia supernova ASASSN-20jq/SN 2020qxp. It is a low-luminosity object with a peak absolute magnitude of $M_B=-17.1\pm0.5$ mag. Despite its low luminosity, its post-peak light-curve decline rate ($Δm_{15}(B)=1.35\pm0.09$ mag) and color-stretch parameter (sBV>0.82) are similar to normal SNe Ia, making it an outlier in the luminosity-width and luminosity-color-stretch relations. Early light curves suggest a "bump" during the first 1.4 days of explosion. ASASSN-20jq synthesized a low radioactive $^{56}$Ni mass of $0.09\pm0.01M_\odot$. Near-maximum light spectra reveal strong Si II absorption lines, indicating a cooler photosphere than normal SNe Ia, but lack Ti II absorption lines. Unusually strong O I $λ$7773 and Ca II near-infrared triplet absorption features are present. Nebular spectra show a strong, narrow forbidden [Ca II] $λλ$7291,7324 doublet emission, rarely seen in SNe Ia except in some Type Iax events. Marginal detection of [O I] $λλ$6300,6364 doublet emission, which is extremely rare, is observed. Both [Ca II] and [O I] lines are redshifted by $\sim2000$ km/s. A strong [Fe II] $λ$7155 emission line with a tilted-top profile, identical to the [Fe II] $λ$16433 profile, is also observed. These asymmetric [Fe II] profiles and redshifted [Ca II] and [O I] emissions suggest a high central density white dwarf progenitor undergoing an off-center delayed-detonation explosion mechanism, producing roughly equal amounts of $^{56}$Ni in deflagration and detonation phases. This distinguishes ASASSN-20jq from normal and subluminous SNe Ia. ASASSN-20jq's light curve and spectra do not align with any single SNe Ia subclass but show similarities to 2002es-like objects. Thus, we add it as an extreme candidate within the heterogeneous parameter space of 2002es-like SNe Ia.
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