Do some astronomers specialize in exosolar planets

Just wondering

Yes. Astronomers are very active currently with the data acquired from the Kepler Mission, which is monitoring and imaging about 150,000 stars in one small region of the sky.

Over 700 exoplanets have been observed by astronomers, a few by amateur astronomers. Another thousand or so are soon to follow once the candidates have been confirmed as true exoplanets.

Given the amount of research going into detecting exoplanets, yes.
http://exoplanets.org/
http://exoplanets.sfsu.edu/Research/Exop…
http://exep.jpl.nasa.gov/
http://exoplanets.astro.yale.edu/
https://astronomy.osu.edu/news/kepler-je…
And so on.

Geoffrey Marcy is probably the best known and most active, but there are others