Hanjie Tan (Institute of Astronomy, National Central University), Mi Zhang, Guoyou Sun, Jingyuan Zhao (Xingming Observatory), Quanzhi Ye , Xing Gao (Xingming Observatory), report ~4 mag outburst in a known variable star ( 16.81 r ) which is 21.06 rmag in Pan-STARRS DR1 catalogue. The transient was discovered on several 120-s survey images ( limiting mag about 19.0 ) taken by Xing Gao at Xingming Observatory #3 ( N88 ) around Mar. 02.75369, 2021 UT using a unfiltered CCD ( 0.3-m f/3.6 reflector ). Images can be found at: http://xjltp.china-vo.org/xm57ht.html
XM57HT C2021 03 02.75369 06 34 39.48 +32 25 18.7 16.81 r N88
XM57HT C2021 03 02.77072 06 34 39.48 +32 25 18.9 17.06 r N88
*Known VS MGAB-V319
