MGAB-V300: rebrightening from a possible AM CVn star Type from ZTF data. Rapid fading (2 mag/d) and rebrightening in the past data. YYYYMMDD(UT) mag observer 20220612.2432 14.06C (Masao Funada) 20220612.3877 14.328zr (Zwicky Transient Facility Lasair (Masci+ 2019)) 20220614.3776 17.032zr (Zwicky Transient Facility Lasair (Masci+ 2019)) 20220614.4204 17.024zg (Zwicky Transient Facility Lasair (Masci+ 2019)) 20220615.163 <16.70C (Gary Poyner) 20220615.1640 <173C (Masao Funada) 20220617.715 16.45C (Hiroshi Itoh)