Swift follow-up of the blazar 4C+21.35 (PKS 1222+21) after a bright gamma-ray flare

Following the AGILE/GRID (ATel #2686) and Fermi/LAT (ATel #2687) detection of a gamma-ray flare on June 19, 2010, from a source positionally consistent with the Flat Spectrum Radio Quasar 4C +21.35 (also known as PKS 1222+21 and 1FGL J1224.7+2121; R.A.=12h24m54.5s, Dec=+21d22m46.4s, J2000) at z=0.43, six Swift Target of Opportunity observations were performed between 20 and 23 June. The Swift/XRT data were taken in Photon Counting mode for a total exposure time of 13.5 ks, while the Swift/UVOT was operated with all filters.