发现一颗高偏心色球活动双星：ASASSN-V J192114 .84+624950.8
Discovery of a Highly Eccentric, Chromospherically Active Binary: ASASSN-V J192114.84+624950.8
摘要：
作为全天超新星自动巡天（ASAS-SN）搜索具有大通量递减的源的一部分，我们发现了一个瞬态，其中静止的恒星源ASASSN-V J192114.84+624950.8在g波段的$\sim55\%$（$\sim0.9$等）的通量迅速下降。\textit{TESS}光变曲线显示，这个来源是一个高度偏心的食双星。使用\textsc{phoebe}拟合光变曲线，发现双星轨道具有$e=0.79$、$P_{\rm orb}=18.462~\text{days}$和$i=88.6^{\circ}$，恒星半径和温度的比值为$R_2/R_1 = 0.71$和$T_{e,2}/T_{e,1} = 0.82$。这两颗恒星都是色球活跃的，使我们能够确定它们的旋转周期分别为$P_1=1.52$天和$P_2=1.79$天。LBT/MODS光谱表明，主星是晚G型或早K型矮星。与SED的拟合显示，这两颗恒星的光度和温度分别为$L_1 = 0.48~L_{\sun}$、$T_1= 5050~K$、$L_2 = 0.12~L_{\sun}$和$T_{2} = 4190~K$。我们的结论是，ASASSN-V J192114.84+624950.8由两颗色球活跃的旋转变星组成，它们位于一个高度椭圆的食轨道上。
英文摘要：
As part of an All-Sky Automated Survey for SuperNovae (ASAS-SN) search for sources with large flux decrements, we discovered a transient where the quiescent, stellar source, ASASSN-V J192114.84+624950.8, rapidly decreased in flux by $\sim55\%$ ($\sim0.9$ mag) in the g-band. The \textit{TESS} light curve revealed that the source is a highly eccentric, eclipsing binary. Fits to the light curve using \textsc{phoebe} find the binary orbit to have $e=0.79$, $P_{\rm orb}=18.462~\text{days}$, and $i=88.6^{\circ}$ and the ratios of the stellar radii and temperatures to be $R_2/R_1 = 0.71$ and $T_{e,2}/T_{e,1} = 0.82$. Both stars are chromospherically active, allowing us to determine their rotational periods of $P_1=1.52$ days and $P_2=1.79$ days, respectively. A LBT/MODS spectrum shows that the primary is a late-G or early-K type dwarf. Fits to the SED show that the luminosities and temperatures of the two stars are $L_1 = 0.48~L_{\sun}$, $T_1= 5050~K$, $L_2 = 0.12~L_{\sun}$, and $T_{2} = 4190~K$. We conclude that ASASSN-V J192114.84+624950.8 consists of two chromospherically active, rotational variable stars in a highly elliptical eclipsing orbit.
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