Discovery of a highly eccentric, chromospherically active binary: ASASSN-V J192114.84+624950.8

As part of an All-Sky Automated Survey for SuperNovae (ASAS-SN) search sources with large flux decrements, we discovered a transient where the quiescent, stellar source, ASASSN-V J192114.84+624950.8, rapidly decreased in by $\sim55\%$ ($\sim0.9$ mag) g-band. The \textit{TESS} light curve revealed that source is highly eccentric, eclipsing binary. Fits to using \textsc{phoebe} find binary orbit have $e=0.79$, $P_{\rm orb}=18.462~\text{days}$, and $i=88.6^{\circ}$ ratios radii temperatures be $R_2/R_1 = 0.71$ $T_{e,2}/T_{e,1} 0.82$. Both stars are chromospherically active, allowing us determine their rotational periods $P_1=1.52$ days $P_2=1.79$ days, respectively. A LBT/MODS spectrum shows primary late-G or early-K type dwarf. SED show luminosities two $L_1 0.48~L_{\sun}$, $T_1= 5050~K$, $L_2 0.12~L_{\sun}$, $T_{2} 4190~K$. We conclude J192114.84+624950.8 consists variable elliptical orbit.