TITLE: GCN CIRCULAR NUMBER: 10014 SUBJECT: GRB 091010: RXTE detection DATE: 09/10/11 15:16:55 GMT FROM: Peter Curran at MSSL A.L. Watts, A. Patruno, M. van der Klis (U.v. Amsterdam), P. Casella (Southampton), P.A. Curran (MSSL-UCL), D. Altamirano, Y. Cavecchi, N. Degenaar, R. Kaur, M. Linares, P. Soleri, R. Wijnands, A. Kamble (U.v. Amsterdam) and N. Rea (ICE-CSIC/IEEC) report: RXTE observations taken at the time of the SuperAGILE detected burst GRB 091010 (Donnarumma et al., GCN Circ. 10004; Feroci, GCN Circ 10005) also recorded the event.  The RXTE PCA detected two strong flares in emission, the first coinciding with the SuperAGILE trigger time (02:43:09 UT) and the other 2s later.  Each flare lasted ~1s. There is also evidence for a third weaker flare 5s after the trigger. Peak count-rate (2-60 keV, 0.1s binning) for the first flare is 250 counts/s, and for the second flare is 500 counts/s. The RXTE lightcurve can be found at http://staff.science.uva.nl/~pgcasell/GRB091010 At the time RXTE was observing XTE J1751-305, with nominal pointing direction RA(J2000)  = 17h 51m 13.49s Dec(J2000) = -30d 39' 23.4" so was approximately 28 degrees off-axis from GRB 091010.  For this reason spectral and timing information will be degraded. Preliminary timing analysis reveals no significant periodic variability. The flares are not detected strongly below 30 keV.  Although bright, this GRB did not have an exceptionally high peak flux.  It is therefore perhaps a little surprising that RXTE was able to record this event so strongly given the offset angle. Reflections in the collimator may be responsible (see Laros et al. 1985). We would like to thank the SuperAGILE team for providing us with their lightcurve for GRB 091010, which enabled us to confirm the RXTE identification.