TITLE: GCN CIRCULAR NUMBER: 16118 SUBJECT: GRB 140419A: Swift detection of a burst with optical afterglow DATE: 14/04/19 04:21:34 GMT FROM: Caryl Gronwall at PSU/Swift-UVOT F. E. Marshall (NASA/GSFC), J. R. Cummings (NASA/UMBC), C. Gronwall (PSU), J. A. Kennea (PSU), A. Maselli (INAF-IASFPA), T. Sakamoto (AGU), M. H. Siegel (PSU) and T. N. Ukwatta (MSU) report on behalf of the Swift Team: At 04:06:51 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 140419A (trigger=596426). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 126.999, +46.221 which is RA(J2000) = 08h 28m 00s Dec(J2000) = +46d 13' 15" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 80 sec. The peak count rate was ~5611 counts/sec (15-350 keV), at ~52 sec after the trigger. The XRT began observing the field at 04:08:17.5 UT, 86.5 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 126.9909, 46.2416 which is equivalent to: RA(J2000) = +08h 27m 57.82s Dec(J2000) = +46d 14' 29.8" with an uncertainty of 4.8 arcseconds (radius, 90% containment). This location is 76 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. The initial flux in the 2.5 s image was 5.09e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 96 seconds after the BAT trigger. A bright uncatalogued source is identified in the 2.7'x2.7' sub-image near the position of the XRT afterglow. However, a more precise position is unavailable at this time. The approximate magnitude in the White filter is 16.1. No correction has been made for the expected extinction corresponding to E(B-V) of 0.03. Burst Advocate for this burst is F. E. Marshall (marshall AT milkyway.gsfc.nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/too.html.)