We find that the Kerr-(Newman)-${\mathrm{AdS}}_4$ black hole will be shadowless if its rotation parameter is larger than a critical value and shadowless-ness may be related to the appearance of the null hypersurface caustics (NHC) both inside the Cauchy horizon and outside the event horizon for the black hole with the rotation parameter beyond the critical value. Our studies also further confirm that whether an ultraspinning black hole is superentropic or not is unrelated to the existence of the NHC outside the event horizon.

• Received 30 July 2021
• Accepted 28 September 2021

DOI:https://doi.org/10.1103/PhysRevD.104.L121501