AT 2020afjz (TSS2020a)：首个由凌星系外行星巡天卫星（TESS）发现的快速河外瞬变源

本文报告了首个在光学波段被完整观测到从爆发到衰减全过程的小时级河外瞬变源 AT 2020afjz。该天体由凌星系外行星巡天卫星（TESS）通过 TESSELLATE 巡天观测项目发现，其光变特征与“脏火球”或孤立余辉模型相符。

arXiv:2608.17242v1 Announce Type: new Abstract: We report the discovery of AT 2020afjz (TSS2020a): the first hour-scale extragalactic transient discovered in optical wavelengths whose complete evolution -- from explosion onset to decay -- is temporally resolved, and the first such transient discovered by TESS. AT 2020afjz was identified as a $>10\sigma$ detection in the pilot HiLaTS program run within the TESSELLATE Sky Survey, which blindly searches for transient phenomena in TESS data with the TESSELLATE pipeline. Through cross-matching with legacy imaging, we associate it with DES J042144.37$-$383311.3, a member of an interacting galaxy pair at $z_{\rm phot}=0.67^{+0.07}_{-0.10}$. While AT 2020afjz is similar in duration and brightness to GRB afterglows, it exhibits a slow rise time of $\sim1$ hr and lasts for only 2.4 hr above the half-max brightness; modeling the TESS light curve with VegasAfterglow finds that it is best described as either an on-axis "dirty-fireball" or off-axis orphan afterglow. Each of these rare classifications hinge upon a non-detection at gamma-ray energies, but as Fermi-GBM was Earth-occulted at the time of explosion, AT 2020afjz's gamma-quiet nature cannot be definitively confirmed. Regardless, AT 2020afjz demonstrates TESS's power to discover fast extragalactic transients, and heralds a new population awaiting discovery with TESSELLATE.