TITLE: GCN CIRCULAR NUMBER: 17221 SUBJECT: GRB 141221A: Continued Skynet PROMPT-CTIO observations DATE: 14/12/22 20:18:17 GMT FROM: Adam S. Trotter at UNC-Chapel Hill/PROMPT/Skynet A. Trotter, J. Haislip, D. Reichart, A. Aji, R. Beauchemin, T. Berger, A. Dow, A. Foster, N. Frank, M. Hinckle, K. Ivarsen, A. LaCluyze, M. Maples, J. Moore, M. Nysewander, C. Salemi, L. Zbinden, and J. A. Crain report: Skynet continued to observe the Swift UVOT localization of GRB 141221A (Sonbas et al., GCN 17206, Swift trigger=622006) with two 16" telescopes of the PROMPT array at Cerro Tololo, Chile. Starting at 2014-12-22 07:08 UT and continuing until 08:34 UT (t=23.0h-24.5h post-trigger), Skynet took a total of 64 exposures of 160s each in the V and I bands. We stacked subsets of these images to maximize the signal-to-noise ratio. We no longer detect the optical afterglow that we described in Trotter et al. (GCN 17210). Our limiting magnitudes are: ================================== tmid expos fil limit ================================== 23.8h 32x160s V >21.2 23.8h 31x160s I >20.7 A preliminary light curve is at: http://www.skynet.unc.edu/grb/grb141221a_2.png Magnitudes are in the Vega System, calibrated to 3 APASS stars in the field. Magnitudes have not been corrected for line-of-sight Milky Way dust extinction, with expected E(B-V)=0.024 (Schlafly & Finkbeiner 2011). No further Skynet observations are scheduled.