come up vs come about

come up and come about both are verbs.

Word	Noun	Adjective	Verb	Adverb
come up	No	No	Yes	No
come about	No	No	Yes	No

As verbs, come about is a hypernym of come up; that is, come about is a word with a broader meaning than come up:

Other hypernyms of come up include fall out, go on, hap, happen, occur, pass, pass off, take place.

come up (verb)	come about (verb)
result or issue	come to pass
start running, functioning, or operating
gather or bring together
gather (money or other resources) together over time
bring forth, usually something desirable
come up, of celestial bodies
come to the surface
move toward, travel toward something or somebody or approach something or somebody
move upward
get something or somebody for a specific purpose
originate or come into being
be mentioned