has been dimming
Presente perfecto progresivo para el sujeto he/she del verbo dim.

dim

Popularity
500+ learners.
For no obvious reason, Tabby's Star has been dimming and brightening in strange and unpredictable ways.
Sin ninguna razón obvia, la Estrella de Tabby se ha estado atenuando y brillando de formas extrañas e impredecibles.
Palabra del día
tejer