Title: Photometric variable stars in the young open cluster NGC 6823 Show Chinese title

Title: 光度变星在年轻的疏散星团NGC 6823中

Abstract: We present stellar variability towards the young open cluster NGC\,6823. Time series $V$- and $I$-band CCD photometry led to identification and characterization of 88 variable stars, of which only 14 have been previously recognized. We ascertain the membership of each variable with optical $UBVI$ and infrared photometry, and with Gaia EDR3 parallax and proper motion data. Seventy two variable stars are found to be cluster members, of which 25 are main sequence stars and 48 are pre-main-sequence stars. The probable cluster members collectively suggest an isochrone age of the cluster to be about 2~Myrs based on the GAIA photometry. With the color and magnitude, as well as the shape of the light curve, we have classified the main sequence variables into $\beta$~Cep, $\delta$~Scuti, slowly pulsating B type, and new class variables. Among the pre-main-sequence variables, eight are classical T Tauri variables, and four are Herbig Ae/Be objects, whereas the remaining belong to the weak-lined T Tauri population. The variable nature of 32 stars is validated with TESS light curves. Our work provides refined classification of variability of pre-main-sequence and main-sequence cluster members of the active star-forming complex, Sharpless\,86. Despite no strong evidence of the disk-locking mechanism in the present sample of TTSs, one TTS with larger $\Delta(I-K)$ is found to be slow rotator. Show Chinese abstract

Abstract: 我们展示了年轻开放星团NGC 6823的恒星变异性。时间序列$V$和$I$波段CCD测光导致识别和表征了88颗变星，其中只有14颗已被先前确认。我们通过光学$UBVI$和红外测光，以及Gaia EDR3视差和自行数据来确定每颗变星的成员资格。发现72颗变星是星团成员，其中25颗是主序星，48颗是前主序星。根据GAIA测光，这些可能的星团成员共同表明星团的等时线年龄约为2~Myrs。根据颜色和亮度以及光变曲线的形状，我们将主序变星分类为$\beta$Cep、$\delta$Scuti、缓慢脉动B型星和新类别变星。在前主序变星中，有8颗是经典T Tauri变星，4颗是Herbig Ae/Be天体，其余属于弱线T Tauri星群体。32颗恒星的变异性通过TESS光变曲线得到了验证。我们的工作提供了对活跃恒星形成复合体Sharpless 86中前主序星和主序星成员变异性更精确的分类。尽管目前的TTS样本中没有强有力的盘锁机制证据，但发现一颗具有较大$\Delta(I-K)$的TTS是慢速旋转体。