TITLE: GCN CIRCULAR NUMBER: 23082 SUBJECT: GRB 180805B: Swift-BAT refined analysis (short GRB with extended emission) DATE: 18/08/06 02:00:36 GMT FROM: Amy Lien at GSFC T. Sakamoto (AGU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), P. D'Avanzo (INAF-OAB), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), J. P. Norris (BSU), D. M. Palmer (LANL), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 180805B (trigger #851855) (D'Avanzo et al., GCN Circ. 23076). The BAT ground-calculated position is RA, Dec = 25.877, -17.475 deg which is RA(J2000) = 01h 43m 30.6s Dec(J2000) = -17d 28' 29.3" with an uncertainty of 3.1 arcmin, (radius, sys+stat, 90% containment). The partial coding was 67%. The mask-weighted light curve show a short pulse that starts from ~T-0.1 s, peaks at ~T+0.1 s, and ends at ~T+0.7 s. The short pulse is followed by some weak emission that lasts until ~ T+130 s. T90 (15-350 keV) is 122.5 +- 18.3 sec (estimated error including systematics). The time-averaged spectrum from T-0.10 to T+127.46 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.13 +- 0.29. The fluence in the 15-150 keV band is 9.6 +- 1.7 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T-0.11 sec in the 15-150 keV band is 1.7 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The structure of the burst shows similarity to those of short GRBs with extended emission. We thus perform further analysis on the short spike and the tail emission. The spectrum of the short pulse from T-0.001 to T+0.712 sec can be fitted by a simple power-law model with power-law index of 0.66 +- 0.20 and fluence (15-150 keV) of 1.7 +- 0.2 x 10^-7 erg/cm2. The spectrum of the extended emission from T+0.712 to T+126.532 sec is best fit by a simple power-law model, with power-law index of 1.16 +- 0.39 and fluence (15-150 keV) of 6.8 +- 1.6 x 10^-7 erg/cm2. These values are consistent with those of short GRBs with extended emission (Lien & Sakamoto et al. 2016). The lag analysis does not produce a well-constrained value due to the weakness of the short pulse. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/851855/BA/