Is Arthur Trent Vesper 1 in The 39 Clues?

No, apparently, he isn't.

I do know who vesper 1 is though.

He is Damien Vesper.

The book ' The Medusa plot's end chapter has a preview to who vesper 1 may be.

His description is an old man with a burn on his arm said to be from the cahill family house fire. Damien Vesper was the only vesper there who survived.

But however, the fire happened 500 years from present, we are told.

Probably a formula created by Damien himself. Gideon and Damien were alchemists.