GRB 130420A: Swift detection of a burst with an optical counterpart. Page, M. J. ; Baumgartner, W. H. ; Beardmore, A. P. ; Chester, M. M. ; Cummings, J. R. ; Oates, S. R. ; Palmer, D. M. Abstract Publication: GRB Coordinates Network Pub Date: 2013 Bibcode: 2013GCN.14406....1P