In which two constellations, were the two gravitational wave events of 2016? As best as is known, what is the latest thinking on in the issue of,

in which constellation was GW150914, and in which constellation was GW151226?

(That is to say, within the large uncertainty, as best as is known in what direction is the likely center of that uncertainty?)
The data is indeed very uncertain. As for GW150914, LIGO posted this image of the probable area of the sky:



The most probable banana-shaped region stretches from Crux to the Large Magellanic cloud. Comparing the image with a constellation map, there are several small constellations that may have hosted the event. Those are Mensa, Chamaeleon, Musca and Crux.