Indefinite/definite article before an adjective + a person's name ("an exasperated Einstein")

Question

I saw the following sentence in a book that I'm reading:

"Why do I get my best ideas in the shower?" an exasperated Einstein is said to have remarked.

I was wondering why an indefinite article is used before Einstein. My best guess is that it's because they are referring to one of many states of Einstein (for example, a tired Einstein, a confused Einstein, etc.), but I'm not sure what the grammatical reason behind this is.

I came up with other adjectives that required a definite article "the" before adjective + Einstein, for example, "the newly-wedded Einstein" or "the recently-relocated Einstein". However, I don't understand the rules for why a definite article must be used in these cases and an indefinite article in the earlier cases.

Answer 1

I don't know if there are formal grammatical rules for this usage, but the indefinite article denotes a temporary state, where Einstein may have seemed exasperated when he made the remark. Using a definite article tends to identify a subject that has transitioned to a new state, so there is clearly a before-and-after condition that applies.