TITLE: GCN CIRCULAR NUMBER: 10496 SUBJECT: GRB 100316D: Swift detection of a burst DATE: 10/03/16 12:56:50 GMT FROM: Scott Barthelmy at NASA/GSFC M. Stamatikos (OSU/NASA/GSFC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), A. P. Beardmore (U Leicester), S. Campana (INAF-OAB), A. de Ugarte Postigo (INAF-OAB), P. A. Evans (U Leicester), J. M. Gelbord (PSU), C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), R. Margutti (Univ Bicocca&OAB), F. E. Marshall (NASA/GSFC), S. R. Oates (UCL-MSSL), C. Pagani (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), P. Romano (INAF-IASFPA), B. Sbarufatti (INAF-OAB/IASFPA), R. L. C. Starling (U Leicester) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team: At 12:44:50 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 100316D trigger=416135). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 107.615, -56.278 which is RA(J2000) = 07h 10m 28s Dec(J2000) = -56d 16' 40" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). This is an image trigger, but there is a possibility that there is a low-level peak about 100 sec long. The XRT began observing the field at 12:47:08.1 UT, 137.7 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 107.6291, -56.2567 which is equivalent to: RA(J2000) = 07h 10m 30.98s Dec(J2000) = -56d 15' 24.1" with an uncertainty of 5.0 arcseconds (radius, 90% containment). This location is 81 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 2.38e-09 erg cm-2 s-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 148 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. Because part of the 2.7'x2.7' sub-image was not received, the overlap with the XRT error circle is uncertain. 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 0.12. Burst Advocate for this burst is M. Stamatikos (Michael.Stamatikos-1 AT 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.)