VI-Band Follow-Up Observations of Ultra-Long-Period Cepheid Candidates in M31

Chow-Choong Ngeow, Chien-Hsiu Lee, Michael Ting-Chang Yang +7

The ultra-long period Cepheids (ULPCs) are classical Cepheids with pulsation periods exceeding $\approx 80$ days. The intrinsic brightness of ULPCs are ~1 to ~3 mag brighter than t…