Is there an English word for "a name you legally gave yourself"?

Let's say that a woman known since birth as Alice Smith changes her name to Mary Jones. Alice Smith would be her "birthname"; is there a word for Mary Jones meaning "a name she gave herself"?

I see that there is a word "autonym," but it does not appear to have that meaning:
https://en.wiktionary.org/wiki/autonym

Note that I'm not looking for "married name," which would apply to a name acquired through marriage.

It could of course be the case that a person legally changes just their first name (not a nickname but a completely different name), but keeps the last name. What would that first name be called?

UPDATE: Lots of good answers here, getting at various nuances. In the particular case I am asking about, the name was legally changed, so many of the answers (like "pseudonym") probably wouldn't work. Sorry I wasn't clearer when I said that she "changes her name."

Answer

I'm going with "legally assumed name," because

• It does imply that the name has been changed.


• It does not imply that the name is not a true, legal name.


• It does not have an implied context, e.g. war, theater, authorship, or crime.

Thanks to Mazura for the hint, which led me to this in Wikipedia:

Most state courts have held that a legally assumed name (i.e., for a
non-fraudulent purpose) is a legal name and usable as their true name,
...

although it does go on to add this:

... though assumed names are often not considered the person's
technically true name.