Interestingly, the noun «personne» is always feminine (even if used to refer to a male). Just one of those quirks of French.
Sorry, this does not work in modern English, though it would have been appropriate in past eras. "Persons" is correct in legalistic terms (legal documents) or to specifically differentiate between the people in a group or refer to them individually. https://www.grammarly.com/blog/persons-people-peoples/ Otherwise the use of persons has fallen out of favor and Oxford does not recommend its use.
In this case, «absentées» is the past participle of the verb «s'absenter» (not the adjective). «se» is the pronoun associated with the pronominal verb.