//////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3496 SUBJECT: Swift-BAT detection of possible GRB 050528 DATE: 05/05/28 05:50:12 GMT FROM: Hans Krimm at NASA-GSFC S.T. Holland (GSFC/USRA), D. Band (GSFC/UMBC), S. Barthelmy (GSFC), N. Gehrels (GSFC), M. Goad (Leicester U.), C. Gronwall (PSU), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), P. Roming (PSU) on behalf of the Swift team At 04:06:45 UT on May 28, 2005 the BAT instrument on the Swift spacecraft triggered on (trigger = 130679) and located possible GRB 050528. The BAT on-board calculated location is RA 353.529d {+23h 34m 07s} (J2000), +45.944d {+45d 56' 37"} (J2000) with an uncertainty of 4 arc minutes (radius, 3-sigma, including systematic uncertainty). Due to the temporary lack of BAT lightcurves and engineering work on the XRT, there is no additional information on this burst at this time. We can not say if this is a real GRB or not. The full data set from the next available Malindi downlink will be available at approximately 10:00 UT. A burst validity statement will be made at that time. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3497 SUBJECT: Possible GRB050528: no candidate from Liverpool Telescope DATE: 05/05/28 06:18:47 GMT FROM: Alessandro Monfardini at JMU/Liverpool Robotic Tele A. Monfardini, A. Gomboc, C. Guidorzi, C.G. Mundell, I. A. Steele, C.J. Mottram, D. Carter, R.J. Smith, M.F. Bode (Liverpool JMU) report: "The Liverpool Telescope reacted to the SWIFT trigger 130679. The automatic detection mode resulted in a non-detection. We remind that our field-of-view is 4.6 arcmin wide. The earlier, robotic upper limit is R>17.2 at 2.5 minutes after the possible GRB reported time (limited by observing conditions). Further observations have been performed, and quick inspection reveals no obvious candidates. Analysis is in progress. This message can be cited." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3498 SUBJECT: GRB050528: BOOTES optical candidate DATE: 05/05/28 13:53:50 GMT FROM: Martin Jelinek at Inst.Astrophys.Andalucia,Granada Martin Jelinek, Alberto J. Castro-Tirado, Antonio de Ugarte Postigo, Stanislav Vitek, Sergey Guziy (IAA CSIC Granada, Spain), Petr Kubanek, Rene Hudec, Martin Nekola, (ASU AV CR Ondrejov, Czech Republic) Petr Pata, Martin Bernas (CVUT Praha, Czech Republic), and Tomas de J. Mateo Sanguino (Univ. Huelva, Spain) report Robotic telescope BOOTES-1B located at CEDEA in El Arenosillo, Suthern Spain, has observed the error box of GRB050528 starting 71s after the GRB trigger. We see a bright variable object at 23:34:42.93 +45:56:14.4 Further analysis is in progress. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3500 SUBJECT: GRB050528: BOOTES optical candidate (retraction) DATE: 05/05/28 14:52:48 GMT FROM: Martin Jelinek at Inst.Astrophys.Andalucia,Granada Martin Jelinek, Alberto J. Castro-Tirado, Antonio de Ugarte Postigo, Stanislav Vitek, Sergey Guziy (IAA CSIC Granada, Spain), Petr Kubanek, Rene Hudec, Martin Nekola, (ASU AV CR Ondrejov, Czech Republic) Petr Pata, Martin Bernas (CVUT Praha, Czech Republic), and Tomas de J. Mateo Sanguino (Univ. Huelva, Spain) enunciate sadly that the optical candidate reported by ourselves in previous GCN (Jelinek et al., GCN3498) is in fact a star, which is not present in GSC2 catalogue. This mislead me (MJ) and although doing a double-check using DSS, I have missed the star, thus convincing myself about reality of the object. We apologize to the comunity for a false alert. Anyhow: The BOOTES-1B has observed the errorbox starting 71s after the trigger in a light twilight, setting the limit to the possible GRB counterpart to V>13.8 and I>13.0 during the first 60s after the beginning of our observation. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3501 SUBJECT: Update on Swift-BAT GRB 050528 (Trigger 130679) DATE: 05/05/28 15:57:03 GMT FROM: Scott Barthelmy at NASA/GSFC S. Barthelmy (GSFC), S.T. Holland (GSFC/USRA), N. Gehrels (GSFC), M. Goad (Leicester U.), C. Gronwall (PSU), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), P. Roming (PSU) on behalf of the Swift team The putative Swift-BAT burst GRB050528 (Trigger 130679 at 04:06:45 UT) (GCN 3496) is still uncertain. Intermittant problems with the transfer of data from Malindi to the US have prevented a final determination of the validity of this BAT trigger. The file transfer problem is being worked, and when we get the data from the trigger time interval, we will issue an update. We apologize for the delay and any inconvenience in follow-up observing programs. //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3502 SUBJECT: Swift-BAT GRB 050528: a soft burst DATE: 05/05/28 19:48:57 GMT FROM: Scott Barthelmy at NASA/GSFC J. Cummings (GSFC/NRC), L. Barbier, S. Barthelmy (GSFC), E. Fenimore (LANL), N. Gehrels (GSFC), D. Hullinger (GSFC/UMD), H. Krimm (GSFC/USRA), C. Markwardt, (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC), G. Sato (ISAS), M. Suzuki (Saitama), T. Takahashi (ISAS), J. Tueller (GSFC) on behalf of the Swift-BAT team: The full data set has been delivered (GCN 3501). Analysis of the data has allowed us to determine that Trigger 130649 at 04:06:45 UT (GCN 3496) is a real GRB. The ground-analysis position is RA,Dec 353.515,+45.938 (J2000) with an uncertainty of 3 arcmin (radius, 90%, statistical plus systematic). The lightcuve shows a single smooth peak lasting ~12 sec with an ~1-sec spike riding on top towards the end of the event. It starts ~T-8 and ends at T+4 sec. T90 is 10.8 sec. The burst spectrum is consistant with a simple power-law with a photon index of 2.44 +-0.25 and a flux of 11.8 +-0.1 ph/cm2/sec (15-350 keV, 90% c.l.). This is a very soft event with essentially no emission above 100 keV. The fluence is (5.1+-0.1)x10^-7 ergs/cm2 (15-350 keV, 90% c.l.). //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3503 SUBJECT: GRB050528: updated Liverpool Telescope limits DATE: 05/05/28 20:39:03 GMT FROM: Alessandro Monfardini at JMU/Liverpool Robotic Tele A. Monfardini, A. Gomboc, C. Guidorzi, C.G. Mundell, I. A. Steele, C.J. Mottram, D. Carter, R.J. Smith, M.F. Bode (Liverpool JMU) report: "As a result of 1 hour monitoring of the center of the possible GRB050528 field (4.6x4.6 arcmin FoV) we provide the following rough limits to update our previous GCN3497: R > 20 at 30 minutes mean epoch I > 19 at 35 minutes mean epoch Observations started 2.5 minutes after the GRB under non-ideal conditions. This message can be cited." //////////////////////////////////////////////////////////////////////// TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3505 SUBJECT: GRB050528, XRT observations DATE: 05/05/31 15:10:43 GMT FROM: Michael Goad at Leicester U M. Goad (U. Leicester), J. Kennea (PSU), and D. N. Burrows (PSU) report on behalf of the Swift XRT team: We have analysed Swift XRT data from the soft burst GRB050528 (GCN3496, GCN3502). The XRT was in an engineering mode at the time of the burst and did not begin observations until it was switched back into its normal observing mode. Analysis of 15965 seconds (9 orbits) of Photon Counting mode data starting 14.15 hours after the BAT trigger reveals 3 faint sources within the BAT 3 arcmin error circle. The source coordinates are : RA(J2000) 23 34 03.7 Dec(J2000) +45 58 18.9 RA(J2000) 23 33 52.1 Dec(J2000) +45 57 40.2 RA(J2000) 23 34 03.2 Dec(J2000) +45 56 03.3 with an estimated uncertainty of 7 arcsecs radius. Sources 1, 2 and 3 are located 122.1, 146.1 and 14.1 arcsecs from the BAT position respectively. Assuming a Crab like spectrum, photon index 2.1, and column density 1.2e21 cm-2 the observed count rates correspond to unabsorbed fluxes of 4.9e-14, 4.2e-14 and 3.2e-14 erg/cm2/s (0.5-10.0 keV), with an uncertainty of 1.2e-14 erg/cm2/s. Due to the faintness of the sources, we cannot determine at this time whether any of the sources are fading.