TITLE: GCN CIRCULAR NUMBER: 5882 SUBJECT: GRB 061201, Swift-BAT refined analysis of the SHB DATE: 06/12/01 21:30:20 GMT FROM: Scott Barthelmy at NASA/GSFC C. Markwardt (GSFC/UMD), L. Barbier (GSFC), S.D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), F.E. Marshall (NASA/GSFC), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) on behalf of the Swift-BAT team: Using the data set from T-239 to T+366 sec from the recent telemetry downlink, we report further analysis of BAT GRB 061201 (trigger #241840) (Marshall, et al., GCN Circ. 5881). The BAT ground-calculated position is RA, Dec = 332.079, -74.569 deg which is RA(J2000) = 22h 08m 19.0s Dec(J2000) = -74d 34' 6.6" with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 48%. The mask-weighted lightcurve shows two main peaks separated by ~0.7 sec, the first starting at T+0 sec, and the second ending at T+1.1 sec. A visual scan of the lightcurve (from T+2 to T+300 sec) places an upper limit of 0.01 ph/cm2/sec for any extended emission. T90 (15-350 keV) is 0.8 +- 0.1 sec (estimated error including systematics). The time-averaged spectrum from T+0.0 to T+0.9 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 0.81 +- 0.15. The fluence in the 15-150 keV band is 3.3 +- 0.3 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.05 sec in the 15-150 keV band is 3.9 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The burst shows significant hard to soft spectral evolution. A fit to the first peak (T+0.0 to T+0.7) gives a simple power law index of 0.57 +/- 0.15, while a fit to the second peak (T+0.7 to T+0.9) has a power law index of 2.10 +/- 0.35. Similarly, the light curve shows that the emission in the 15-25 keV channel extends to T+1.5 sec, while emission in the 100-350 keV channel lasts only until ~T+0.6 sec.