//////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3826 SUBJECT: GRB050819: Swift-BAT detection of a weak burst DATE: 05/08/19 17:23:53 GMT FROM: Scott Barthelmy at NASA/GSFC M. De Pasquale (MSSL), S. Barthelmy (GSFC), A.P. Beardmore (U Leicester), D. Burrows (PSU), M. Chester (PSU), A. Cucchiara (PSU), J. Cummings (GSFC/NRC), N. Gehrels (GSFC), M.R. Goad (U Leicester), J. Kennea (PSU), H. Krimm (GSFC/USRA), S.T. Holland (GSFC/USRA), S. Hunsberger (PSU), F. Marshall (GSFC), C. Markwardt (GSFC/UMD), J.P. Osborne (U Leicester), K.L. Page (U Leicester), D. Palmer (LANL), A. Parsons (GSFC), P. Roming (PSU), T. Sakamoto (GSFC), M. Still (GSFC) on behalf of the Swift team: At 16:23:55 UT, Swift-BAT triggered and located GRB050819 (trigger 151131). The BAT on-board calculated location is RA,Dec 358.735d,+24.854d {23h 54m 56s,+24d 51' 13"} (J2000), with an uncertainty of 2 arcmin (radius, 90% containment, stat+sys). The BAT light curve shows a very broad shallow peak of about 40 seconds duration. The peak count rate was ~400 counts/sec (15-350 keV) at ~10 seconds after the trigger. The spacecraft slewed immediately and the XRT began taking data at 16:26:15.8, 141 seconds after the BAT trigger. There were not enough counts in the first 2.5 s image for a successful on-board centroid. However, the light-curve shows evidence for a decaying X-ray source in the field of view and the spectrum appears consistent with that of a GRB. The UVOT began observing the position of the trigger at 16:26:13.5 UT, 138 s after the BAT trigger. In a 100 s V-band image, no new source is detected with respect to the DSS down to a 5 sigma upper limit of 18.1 mag. The estimated extinction in this direction is A_V ~ 0.4 magnitudes. The UVOT image gives 50% coverage assuming a BAT error circle of 2 arcmin radius. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3827 SUBJECT: GRB050819: Swift XRT position DATE: 05/08/19 18:32:59 GMT FROM: Jamie A. Kennea at PSU/Swift-XRT J.A. Kennea, D.N. Burrows (PSU), K. Page (U. Leceister) report on behalf of the Swift/XRT team: We have analysed the ground data from GRB 050819 (BAT Trigger #151131). We find a previously uncatalogued, fading X-ray source at the following coordinates: RA(J2000): 23:55:01.2 Dec(J2000): 24:51:36.5 with a uncertainty of 8 arcseconds radius (90% containment). This position is 69 arcseconds from the BAT position reported in GCN 3826. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3828 SUBJECT: GRB 050819 Swift-BAT refined analysis DATE: 05/08/19 20:09:55 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift S. Barthelmy (GSFC), L. Barbier (GSFC), J. Cummings (GSFC/NRC), D. Hullinger (GSFC/UMD), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), F. Marshall (GSFC), A. Smale (NASA HQ), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC), G. Sato (ISAS), J. Tueller (GSFC) on behalf of the Swift-BAT team: Using the full data set from the recent telemetry downlink, we report further analysis of Swift-BAT GRB 050819 (trigger #151131) (De Pasquale, et al., GCN 3826). The ground-analysis position is RA,Dec 358.757, +24.874 (J2000) with an uncertainty of 2 arcmin (radius, 90%, stat+sys). This is 50 arcseconds from the XRT ground- calculated position reported by Kennea et al. in GCN Circ. 3827. The light curve shows a long weak peak with indistinct structure from T-12 to T+37 seconds. T90 is 36 +/- 4 sec. Fitting a simple power law over the interval from T-2 to T+34 sec, the photon index is 2.6 +/- 0.3 with a fluence of 4.2 +/- 0.8 x 10^-7 erg/cm^2 in the 15-350 keV band (90% c.l.). The peak flux in a 1-sec wide window starting at T+9.5 seconds is 0.46 +/- 0.14 ph/cm^2/sec (15-350 keV). //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3831 SUBJECT: GRB050819: RTT150 optical observations DATE: 05/08/20 08:21:32 GMT FROM: Irek Khamitov at TUG I. Bikmaev, A. Galeev, N. Sakhibullin (KSU/AST), R. Burenin, M. Pavlinsky, R. Sunyaev (IKI), I. Khamitov, Z. Aslan (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.), report: We have observed the error box of GRB 050819 (S. Barthelmy, et al., GCN 3790) with the Russian-Turkish 1.5-m telescope (Bakirlitepe, TUBITAK National Observatory,Turkey). We made a series of 30s and 100s exposures in R between UT 18:35 - 22:15, August 19, 2005, under full Moon conditions. We have found no variable source brighter than magnitude R ~= 21.6 This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3832 SUBJECT: GRB050819: refined XRT analysis DATE: 05/08/20 08:53:47 GMT FROM: Kim Page at U.of Leicester,Swift SDC K.L. Page (U. Leicester), J.A. Kennea, D.N. Burrows (PSU), M. Ajello (MPE), M. Trippico (GSFC-SSAI) report on behalf of the Swift/XRT team: We have analysed the XRT data for GRB050819 (BAT Trigger 151131), between 146 and 3.7e4 seconds after the trigger. As previously reported by Kennea et al in GCN 3827, there is an uncatalogued, fading X-ray source in the field of view. The refined coordinates for this burst are RA(J2000): 23:55:01.37 Dec(J2000): 24:51:31.28 with an uncertainty of 8 arcseconds radius (90% containment). This is 5.7 arcseconds from the XRT position given in GCN 3827 and 75 arcseconds from the initial BAT position reported in GCN 3826. XRT observations began in Windowed Timing mode 146 seconds after the trigger, switching down to Photon Counting mode 58 seconds later. The light-curve shows a steep initial decline with a decay index of alpha = 3.7 +/- 0.3, breaking to a very flat slope of < 0.28 at around 850 seconds. The spectrum of the early afterglow shows no evidence for excess NH above the Galactic value (4.6e20 cm^-2), and can be well fitted by a power-law with Gamma = 2.2 +/- 0.2. Between 146 and 203 seconds, the unabsorbed 0.3-10 keV flux was 1.62e-10 erg cm^-2 s^-1. If the light-curve continues without a further break, the predicted count-rate at 24 hours will be 0.009 counts s^-1, corresponding to 0.3-10 keV flux of 3.2e-13 erg cm^-2 s^-1 (unabsorbed).