标题： H$α$ATLAS18qtd 亮度在新生代阶段并未达到平台期 显示英文标题

标题： H$α$ Luminosity of ATLAS18qtd Does Not Plateau in the Nebular Phase

摘要： 我们提供了ATLAS18qtd/SN 2018cqj的新光谱和测光观测数据，这是一颗快速衰减的Ia型超新星，在之前发表的爆发后期光谱中显示出可变的H$\alpha$发射。ATLAS18qtd在最大亮度后$\sim 540~\rm d$的光谱和测光观测中均未被检测到，以及在最后一次H$\alpha$检测后$\sim 230~\rm d$的观测中也未被检测到。 随着这些新的未检测到的结果，我们对H$\alpha$光度设定了一个上限，即$\lesssim 1.1\times 10^{36}~\rm{erg}~\rm s^{-1}$，表明自上次检测以来H$\alpha$流量减少了$\gtrsim 4$倍。这个上限排除了自上次检测以来趋于平稳或增加的H$\alpha$辐射，但无法确认H$\alpha$辐射衰减率与超新星衰减率相同。 显示英文摘要

摘要： We present new spectroscopic and photometric observations of ATLAS18qtd/SN 2018cqj, a fast-declining Type Ia supernova with variable H$\alpha$ emission in previously-published nebular phase spectra. ATLAS18qtd is undetected in both spectroscopic and photometric observations which occurred at $\sim 540~\rm d$ after maximum light and $\sim 230~\rm d$ after the last H$\alpha$ detection. With these new non-detections, we place an upper limit on the H$\alpha$ luminosity of $\lesssim 1.1\times 10^{36}~\rm{erg}~\rm s^{-1}$ indicating the H$\alpha$ flux decreased by a factor of $\gtrsim 4$ since the previous detection. This upper limit excludes H$\alpha$ emission that plateaus or increases since the previous detection but cannot confirm that the H$\alpha$ emission decay rate is equivalent to the supernova decay rate.