  After finding a solution for the Hayward regular black hole (HRBH) in massive
gravity, we embed the (3+1)-dimensional HRBHs both in massless and in massive
gravities into (5+2)- and (6+3)-dimensional Minkowski spacetimes, respectively.
Here, massive gravity denotes that a graviton acquires a mass holographically
by broken momentum conservation in the HRBH. The original HRBH has no
holographically added gravitons, which we call massless. Making use of newly
found embedding coordinates, we obtain desired Unruh temperatures and compare
them with the Hawking and local fiducial temperatures, showing that the Unruh
effect for a uniformly accelerated observer in a higher dimensional flat
spacetime is equal to the Hawking effect for a fiducial observer in a black
hole spacetime. We also obtain freely falling temperatures of the HRBHs in
massless and massive gravities seen by freely falling observers, which remain
finite even at the event horizons while becoming the Hawking temperatures in
asymptotic infinity.
