Professional and amateur astronomers are continuing to sift through and analyze data they collected during the March 18th occultation involving Pluto and a 15th-magnitude star in Sagittarius. It was the best-ever Pluto occultation predicted for North America, and according to occultation expert David Dunham, the event was successfully recorded at more than 20 locations in the central and western United States.
Preliminary analysis of the data by Bruno Sicardy of Paris Observatory, who observed with the 2.3-meter Bok Telescope in Arizona, indicate that the occultation occurred about 4.8 minutes later than predicted, and that the occultation track was somewhat north of predictions.
As such, observers in the southern portion of the track that crossed Arizona and Texas witnessed a gradual drop in the combined light of Pluto and the star followed immediately by a gradual increase in brightness. This is indicative of an occultation by Pluto's atmosphere, but not by the planet's solid surface, which would have caused a flat-bottomed light curve during the time the star was completely hidden behind the planet.
Dunham's website has a summary of the occultation observations, including links to results obtained at a number observatories, both amateur and professional.