TITLE: GCN CIRCULAR NUMBER: 11300 SUBJECT: MAXI J1659-152: Swift-BAT refined analysis (triggers 434928 and 434931) DATE: 10/09/25 18:55:41 GMT FROM: Scott Barthelmy at NASA/GSFC S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), V. Mangano (INAF-IASFPA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using only a partial data set from T+247 to T+303, T+706 to T+723 and T+728 to T+963 sec (T=08:05:06 UT) from recent downlinks, we report further analysis of MAXI J1659-152 (Swift-BAT trigger #434928) (Negoro, ATEL 2873 and initially reported as GRB 100925A in Mangano, et al., GCN Circ. 11296). The BAT ground-calculated position is RA, Dec = 254.750, -15.206 deg, which is RA(J2000) = 16h 59m 00.0s Dec(J2000) = -15d 12' 20.1" with an uncertainty of 2.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 38%. No statement can be given about the BAT lightcurve because of the fragmented coverage of the transient. This fragmentation is caused by (a) a second Swift-BAT trigger on the same source (a 64-sec image trigger, #434931, at 09:47:13 UT) and (b) the very long integration time of the first trigger (26.5 min). The normal set of event-by-event data used to do this "refined" analysis is not fully available (the on-board event ring buffer has been nearly completely wrapped). The time-averaged spectrum in the 3 time intervals listed above is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.79 +- 0.43. We caution even this limited analysis because of the partial coverage of the time interval of the event. Further, the time-averaged spectrum from T+0.0 to T+64.0 sec (T=09:47:13 UT, the second trigger) is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.36 +- 0.61. All the quoted errors are at the 90% confidence level. The GCN Notices for the first trigger were distributed with a GRB label, because the location did not match any known source in the on-board and ground catalogs. However, the GCN Notices for the second trigger were labeled as a transient because the location matched the location of the first trigger (AT trigger locations are maintained in the on-board catalog up to the 4th trigger in a 3-deep ring buffer).