They are not immigrants, they are expatriates.
"An expatriate (often shortened to expat) is a person temporarily or permanently residing, as an immigrant, in a country other than that of their citizenship."
expats = migrants from the 'elite' class. educated, wealthy, well-connected etc. most often referred to persons from so called '1st/2nd world' countries.
immigrants = migrants from the 'cattle' class. not-so-rich, varied education, mostly non-caucasians. most often referred to persons from so called '3rd world' countries.
According to the article, at least one of the laureates is now a US citizen.