TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2950 SUBJECT: SGR 1806-20: RXTE/PCA pulse frequency during flare DATE: 05/01/14 18:00:12 GMT FROM: Peter Woods at UAH/MSFC Pulse Frequency of SGR 1806-20 during the Giant Flare P.M. Woods, M. Finger, S. Patel (USRA, NSSTC), C. Kouveliotou (NASA/MSFC, NSSTC), Y. Rephaeli (UCSD), D. Gruber (Eureka), M. Persic (Obs.Ast.Trieste), R. Rothschild (UCSD), D. Palmer, N. Gehrels, S. Barthelmy, E. Smith, J. Swank, and C. Markwardt (GSFC) report: We have re-analyzed the RXTE PCA data of the giant flare of 2004 December 27 from SGR 1806-20. We find that the pulse period reported in GCN #2927 of 7.579 +/- 0.002 s was strongly biased by pulse profile changes during the tail of this flare. Excluding the first ~60 s of the flare where pulse profile changes are strongest, we measure a barycenter-corrected pulse period of 7.5605 +/- 0.0006 s, significantly different than the previously reported measurement.