TITLE: GCN CIRCULAR NUMBER: 9161 SUBJECT: GRB 090419: Swift detection of a burst DATE: 09/04/19 13:59:53 GMT FROM: David Burrows at PSU/Swift G. Stratta (ASDC), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC), C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), N. P. M. Kuin (MSSL), V. Mangano (INAF-IASFPA), J. Mao (INAF-OAB), R. Margutti (Univ Bicocca&OAB), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), A. M. Parsons (GSFC), M. Perri (ASDC), P. Romano (INAF-IASFPA) and B. Sbarufatti (INAF-IASFPA) report on behalf of the Swift Team: At 13:43:31 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 090419 (trigger=349592). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 196.976, -75.609 which is RA(J2000) = 13h 07m 54s Dec(J2000) = -75d 36' 30" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a slow single peak taking 30 seconds to rise to a maximum with a duration of at least 90 seconds, and an additional peak at T+320. The peak count rate was ~800 counts/sec (15-350 keV), at ~30 sec after the trigger. The XRT began observing the field at 13:45:31.0 UT, 119.7 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 196.92907, -75.60534 which is equivalent to: RA(J2000) = 13h 07m 42.98s Dec(J2000) = -75d 36' 19.2" with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 44 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (1.2e+21 cm^-2, Kalberla et al. 2005), with an excess column of 1.1 (+0.85/-0.64) x 10^22 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 5.55e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 126 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The coverage of the XRT error circle by the 8'x8' region for the list of sources generated on-board is uncertain because the large number of sources filled the available telemetry. No correction has been made for the expected extinction corresponding to E(B-V) of 0.30. Burst Advocate for this burst is G. Stratta (giulia.stratta AT asdc.asi.it). 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.)