ZTF light curve of AT 2021hdr between 2018-2024. (Top panel): ZTF light curve (in difference flux from PSF forced photometry) of AT 2021hdr in the g (green squares) and r (red triangles). The black dashed line represents the date of the first ZTF alert, and the gray dashed lines correspond to dates when optical spectra were obtained. (Bottom panel): ZTF g-r color evolution in total magnitude (see text for details).