TITLE: GCN CIRCULAR NUMBER: 8870 SUBJECT: GRB 090201: Swift-BAT refined analysis DATE: 09/02/02 04:13:21 GMT FROM: Scott Barthelmy at NASA/GSFC W. H. Baumgartner (GSFC/UMBC), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), S. R. Oates (UCL-MSSL), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+363 sec from the recent telemetry downlink, we report further analysis of BAT GRB 090201 (trigger #341749) (Oates, et al., GCN Circ. 8865). The BAT ground-calculated position is RA, Dec = 92.051, -46.604 deg, which is RA(J2000) = 06h 08m 12.3s Dec(J2000) = -46d 36' 16.1" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 8%. The mask-weighted light curve shows two clusters of overlapping peaks. The first starting at ~T-20 sec and peaking at ~T+8 sec. The second peaks at ~T+39 sec and ends at ~T+120 sec. T90 (15-350 keV) is 83 +- 4 sec (estimated error including systematics). The time-averaged spectrum from T-10.2 to T+102.2 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.88 +- 0.18, and Epeak of 104 +- 16 keV (chi squared 39.5 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 3.0 +- 0.1 x 10^-5 erg/cm2 and the 1-sec peak flux measured from T+7.60 sec in the 15-150 keV band is 14.7 +- 1.0 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.50 +- 0.04 (chi squared 76.3 for 57 d.o.f.). All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/341749/BA/