TITLE: GCN CIRCULAR NUMBER: 11820 SUBJECT: GRB 110319B Swift-XRT afterglow confirmation DATE: 11/03/24 16:31:02 GMT FROM: Boris Sbarufatti at INAF-OAB/IASFPA B. Sbarufatti (INAF-OAB/IASFPA) reports on behalf of the Swift-XRT team: Swift performed a second target of opportunity observation of GRB 110319B on March 23, 2011. The XRT began observing the field at 2011-03-23 17:57:33 UT, that is T+340 ks ( 3.9 days) (Cummings, GCN Circ. 11813). Using 4.9 ks of Photon Counting mode data we find that the source reported previously (Sbarufatti, GCN Circ. 11814) has faded down to a 3-sigma upper limit of 0.002 counts/s. Assuming a power law decay starting from the first source detection the upper limit is consistent with a decay index steeper than alpha = 0.6. The fading nature of the source confirms its afterglow origin. This circular is an official product of the Swift-XRT team.