TITLE: GCN CIRCULAR NUMBER: 11516 SUBJECT: GRB 101219B: After 2 weeks still detected by Swift/UVOT DATE: 11/01/03 23:31:29 GMT FROM: Jonathan Gelbord at PSU/Swift N.P.M. Kuin (MSSL/UCL) and J.M. Gelbord (PSU) report on behalf of the Swift/UVOT team: As reported earlier (Gelbord et al., GCN Circ. 11473; Kuin et al., GCN Circ. 11482), Swift/UVOT observations of GRB 101219B detected an optical afterglow in all its bands with initial magnitudes of about 18 mag. The optical afterglow has been unusually slow to decay, and is around 23 mag at present in the u and uv bands. The UVOT has obtained a good light curve in all bands up to about 300ks, with continuing detections through 1000ks in u, uvw1, uvm2, and uvw2 (v and b measurements after 300ks are significantly affected by the PSF wings of a B = 15.5 mag star located 7 arcsec to the SW). The light curve still appears to be decaying and there is some indication that this decay may not be smooth. GRB 101219B is further interesting because the UVOT light curve exhibits an early decay to about 600 seconds after the trigger time T, after which a second brightness rise to a maximum around T+850s occurs. A corresponding break is found in the X-ray light curve, in that the decay observed by XRT flattens approximately at T+700s. The only constraint on the redshift of this burst is an upper limit around 1.5 implied by the detection in uvw2, as there have not been any spectroscopic observations announced to date. However, if this burst is bright because it is close, then we might detect a supernova bump in the coming days. We consider this an interesting burst and would like to bring this to the attention of the community as an opportunity for further observations.