Sure, a photo taken in non-visible spectrum is still a photo. And stacking photos taken with different wavelength filters or sensor can also be considered a photo. For example the headline image of the spruce tips taken in a lab is photo. And based on the description of the UV camera in the paper, they did generate UV video of the tree tops.
However, the linked article and associated paper don't have any such photos (or video) of the corona in the treetops. Instead the UV video was processed with a detection algorithm, and then the visible-light photos and video were annotated with graphed dots of where detections were seen. Those dots aren't a photo of the corona by any reasonable definition.
However, the linked article and associated paper don't have any such photos (or video) of the corona in the treetops. Instead the UV video was processed with a detection algorithm, and then the visible-light photos and video were annotated with graphed dots of where detections were seen. Those dots aren't a photo of the corona by any reasonable definition.