If a creature is exiled and returned to the battlefield, do Auras fall off?

When a creature is exiled and then returned to the battlefield, it enters as a completely new object. The game has no memory of what was previously attached to, or true of, the old creature. This is known as the 'new object' rule, covered in CR 400.7.

Auras that were enchanting the creature when it left the battlefield remain in whatever zone they moved to (usually the graveyard, since they become unattached and then illegal — CR 704.5n handles this state-based action: if an Aura is on the battlefield not attached to anything legal, it's put into its owner's graveyard). They do NOT automatically follow the creature back.

When the creature re-enters the battlefield, if an effect returning it says 'return it to the battlefield,' no Auras are placed on it unless the returning effect specifically says so (some cards like Oblivion Ring do create a loop, but even then the Aura re-attaches only by instruction of the effect).

Concrete example: Your Gigantosaurus is enchanted with Octopus Umbra. Your opponent casts Flickerwisp, exiling Gigantosaurus. At the end of the turn it returns — but Octopus Umbra is already in the graveyard (state-based actions put it there when it became unattached). Gigantosaurus comes back as a fresh object with no Aura.

Relevant rules: CR 400.7 (objects leaving zones lose history), CR 303.4c (Aura becoming unattached), and CR 704.5n (state-based action putting an unattached Aura into the graveyard).