1 Swift Observation of GRB 100614A G. Stratta (ASDC), V. D’Elia (ASDC), S. T. Holland (CRESST/USRA/GSFC), T. N. Ukwatta (GSFC/GWU), S.D. Barthelmy (GSFC), D.N. Burrows (PSU), P. Roming (PSU), N. Gehrels (GSFC) for the Swift Team 1 Introduction At 21:38:26 UT, the Swift Burst Alert Telescope (BAT) triggered and located the long GRB 100614A (trigger=424716, Stratta et al., GCN Circ. 10837). The BAT light curve shows a smooth peak with a duration of about 300 sec. Swift slewed immediately, and the narrow field instruments were on target 133 seconds later. The X-ray telescope XRT detected a bright X-ray afterglow. UVOT took a finding chart exposure of nominal 250 seconds with the U filter starting 873 seconds after the BAT trigger. No white observations were taken because there is a V = 7.4 star in the UVOT field of view. No credible afterglow candidate has been found in the initial data products to an estimated magnitude limit of u> 19.2. No detection from ground-based facilities has been reported. 2 BAT Observation and Analysis Using the data set from T - 239 to T + 963 sec from prompt telemetry downlinks, the BAT ground- calculated position is RA, Dec = 263.534, 49.232 deg which is RA(J2000) = 17 h 34 m 08.2 s and Dec(J2000) = +49 d 13 ′ 56.4” with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 56%. The mask-weighted light curve shows a relatively smooth peak starting at ∼ T - 10 sec, peaking around T + 50 sec, and ending at ∼ T + 275 sec. T 90 (15 - 350 keV) is 225 ± 55 sec (estimated error including systematics). The time-averaged spectrum from T - 9.0 to T + 282.0 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.88 ± 0.15. The fluence in the 15 - 150 keV band is 2.7 ± 0.2 × 10 −6 erg cm −2 . The 1-sec peak photon flux measured from T + 31.00 sec in the 15 - 150 keV band is 0.7 ± 0.2 ph cm −2 sec −1 . 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/424716/BA/ 3 XRT Observations and Analysis The enhanced Swift/XRT position RA (J2000)= 17 h 33 m 59.82 s and Dec (J2000)= +49 d 14 ′ 03.6” with an uncertainty of 1.7 arcsec (radius, 90% confidence) was given by Osborne et al. (GCN Circ. 10849). The XRT data comprise 451 sec in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a double broken power-law model with an initial decay index of α 1 = (2.2 ± 0.1), a temporal break around T + (3975 ± 10) sec, a second decay index of α 2 =0.434 ± 0.001, a second temporal break at T + (150 +10 −30 ) ks and a final decay index α 3 =2.0 ± 0.4. Modest X-ray flaring activity is detected in the first 1000 sec of observation. A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.85 ± 0.05. The best-fitting absorption column is 1.60 ± 0.15 × 10 21 cm −2 , in excess GCN Report 287.1 04-Jul-10