I found this paper which details how a charged particle falling into a black hole radiates. How is this possible when there is no acceleration on the particle?

https://adsabs.harvard.edu/full/1971PASP...83..633R

Title: Radiation from Particles Falling into Black-Holes

Authors: Ross, D. K.

Journal: Publications of the Astronomical Society of the Pacific, Vol. 83, No. 495, p.633

Bibliographic Code: 1971PASP...83..633R