TITLE: GCN CIRCULAR NUMBER: 16306 SUBJECT: GRB 140518A, Swift-BAT refined analysis DATE: 14/05/19 00:27:52 GMT FROM: Amy Lien at GSFC T. N. Ukwatta (MSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (NASA/UMBC), C. B. Markwardt (GSFC), A. Melandri (INAF-OAB), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), J. Tueller (GSFC) (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 140518A (trigger #599287) (Melandri, et al., GCN Circ. 16298). The BAT ground-calculated position is RA, Dec = 227.231, 42.396 deg which is RA(J2000) = 15h 08m 55.3s Dec(J2000) = +42d 23' 44.2" with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 89%. The mask-weighted light curve shows multiple peaks with roughly three main pulse structures. The first main pulse starts at ~T-4 s and ends at ~T+8 s. The second main pulse starts at ~T+38 s, followed immediately by the third main pulse structure that starts at ~T+48 s and ends at ~T+61 s. Additionally, each of these main pulse structure contains several sub-pulses. T90 (15-350 keV) is 60.5 +- 2.4 sec (estimated error including systematics). The time-averaged spectrum from T-4.1 to T+60.0 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.92 +- 0.61, and Epeak of 43.9 +- 7.6 keV (chi squared 54.15 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.0 +- 0.1 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+41.94 sec in the 15-150 keV band is 1.0 +- 0.1 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.97 +- 0.13 (chi squared 65.02 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/599287/BA/