//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5936 SUBJECT: Swift triggers (#251863) on a possible burst DATE: 06/12/18 04:33:40 GMT FROM: Scott Barthelmy at NASA/GSFC S. Zane (UCL-MSSL), S. D. Barthelmy (GSFC), D. N. Burrows (PSU), M. M. Chester (PSU), N. Gehrels (NASA/GSFC), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), K. M. McLean (LANL/UTD), S. R. Oates (UCL-MSSL), C. Pagani (PSU), D. M. Palmer (LANL) and M. Stamatikos (NASA/ORAU) report on behalf of the Swift Team: At 04:05:05 UT, the Swift Burst Alert Telescope (BAT) triggered and located trigger=251863. Swift slewed immediately to the location. The BAT on-board calculated location is RA, Dec 149.223, -35.146 which is RA(J2000) = 09h 56m 53s Dec(J2000) = -35d 08' 45" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a possible very weak pulse lasting about 10 sec, overlying the much stronger periodic variation of Vela X-1 in the same field. The peak count rate was ~500 counts/sec (15-350 keV), at ~1 sec before the trigger. The XRT began taking data at 04:06:51 UT, 106 seconds after the BAT trigger. The XRT on-board centroid algorithm did not find a source in the image and no prompt position is available. No source is detected in 275s of quicklook photon counting mode data. UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 110 seconds after the BAT trigger, and a finding chart exposure of nominal 400 seconds with the V filter starting 216 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 25% of the BAT error circle. The typical 3-sigma upper limit has been about 18.5 mag (in White). The 8'x8' region for the list of sources generated on-board covers 100% of the BAT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.125 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5937 SUBJECT: GRB 061218: REM prompt observations DATE: 06/12/18 05:17:33 GMT FROM: Paolo D'Avanzo at INAF-OAB P. D'Avanzo, S. Covino, E. Molinari, G. Chincarini, F.M. Zerbi, V. Testa, G. Tosti, F. Vitali, P. Conconi, L.A. Antonelli, G. Cutispoto, G. Malaspina, L. Nicastro, E. Palazzi, E. Meurs, and P. Goldoni report on behalf of the REM/ROSS team We observed the field of the possible GRB 061218 (Zane et al. GCN 5936) with the robotic 60-cm REM telescope located at La Silla (Chile). A set of observations was performed automatically in the optical and near infrared filters (V, R, I and J, H, K, z) starting on 2006 December 18 at 04:07:14 UT, 71 s after the BAT trigger and 129 s after the GRB time. Preliminary analysis of the whole dataset does not show any new variable source inside the BAT error box. The 3-sigma limiting magnitudes are: R~18.6 J~16.7 H~16.0 K~15.3 This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5938 SUBJECT: GRB 061218, SMARTS optical/IR observations DATE: 06/12/18 05:35:07 GMT FROM: Bethany Cobb at Yale U B. E. Cobb (Yale), part of the larger SMARTS consortium, reports: Using the ANDICAM instrument on the 1.3m telescope at CTIO, we obtained optical/IR imaging of the error region of GRB 061218 (GCN 5936, Zane et al.), with a mid-exposure time of 2006-12-18 04:44:48 UT, which is ~0.7 hours post-burst. Our optical images have a field of view of 6'x6' and, therefore, cover the entire GRB error circle. Our IR images have a smaller field of view, covering a region totaling ~6 square arcminutes in the middle of the quoted error region. Several dithered images were obtained in each filter, with total summed exposure times of 180s in each of BRIYJK and 120s in each of H and V. Preliminary visual comparison of the optical images to the DSS and the IR images to 2MASS frames does not reveal any new sources to the limit of the comparison frames. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5940 SUBJECT: GRB 061218, Swift-BAT refined analysis DATE: 06/12/19 00:32:19 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift G. Sato (GSFC/ISAS), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), S. Zane (UCL-MSSL) on behalf of the Swift-BAT team: Using the data set from T-120 to T+183 sec from the recent telemetry downlink, we report further analysis of BAT GRB 061218 (trigger #251863) (Zane, et al., GCN Circ. 5936). The BAT ground-calculated position is RA, Dec = 149.238, -35.221 deg which is RA(J2000) = 09h 56m 57.0s Dec(J2000) = -35d 13' 15.9" with an uncertainty of 4 arcmin, (radius, sys+stat, 90% containment). The burst was in the fully-coded field of view. The mask-weighted lightcurve consists of a single very weak pulse lasting about 7 sec. T90 (15-350 keV) is 4.1 +- 0.5 sec (estimated error including systematics). The time-averaged spectrum from T+0.0 to T+4.1 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.76 +- 0.63. The fluence in the 15-150 keV band is 4.1 +- 1.5 x 10^-8 erg/cm2. The 1-sec peak photon flux measured from T+0.00 sec in the 15-150 keV band is 0.2 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5941 SUBJECT: GRB 061218: TORTOREM optical upper limits DATE: 06/12/19 16:05:22 GMT FROM: Giuseppe Greco at U Bologna S. Karpov, G. Beskin, S. Bondar, C. Bartolini, G. Greco, A. Guarnieri, D. Nanni, A. Piccioni, F. Terra, E. Molinari, G. Chincarini, F.M. Zerbi, S. Covino, V. Testa, G. Tosti, F. Vitali, L.A. Antonelli, P. Conconi, G. Cutispoto, G. Malaspina, L. Nicastro, E. Palazzi, E. Meurs, P. Goldoni report on behalf of the TORTOREM team: The field of GRB 061218 (Zane et al. GCN 5936) has been observed by the TORTORA (Telescopio Ottimizzato per la Ricerca di Transienti Ottici RApidi) wide-field fast camera (12 cm diameter, 20x25 deg FOV) mounted on REM robotic 60-cm telescope located at La Silla (Chile). The burst was initially outside the camera field of view. The system was repointed and the TORTORA began to acquire frames at 04:07:03 UT (118 sec after trigger) with 7.5 Hz frame frequency (0.128 s exposure). The summation of 100 frames with 12.8 s. effective exposure (middle time 04:07:16 UT) did not reveal any source down to the B = 11.3 mag (3-sigma). We performed the Fourier analysis of 23 min data set (10000 successive frames) to search for the periodic signal at the GRB position. The upper limit for the amplitude of sinusoidal variability is B=16.4 (3-sigma) over the 0.01 - 3.5 Hz range. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5943 SUBJECT: GRB 061218: TAROT La Silla observatory optical observations DATE: 06/12/19 22:54:35 GMT FROM: Alain Klotz at CESR-CNRS Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report: We imaged the field of GRB 061218 detected by SWIFT (trigger 251863) with the TAROT robotic telescope (D=25cm) located at the European Southern Observatory, La Silla observatory, Chile. The observations started 126.5s after the GRB trigger (69.6s after the notice). The elevation of the field increased from from 30 degrees above horizon and weather conditions were good. The date of trigger : t0 = 2006-12-18T04:05:06.144 A technichal problem prevent to obtain a 60s image at t0+58s. Moreover, images are slightly defocussed. We examined the BAT position provided by Sato et al. 2006 (GCN Circ. 5940). The first image is 30.0s exposure in tracking mode: We do not detect any OT with a limiting magnitude of: t0+126.5s to t0+156.5s : R > 17.4 The second image is 30.0s exposure: t0+162.3s to t0+192.3s : R > 17.4 We co-added a series of exposures: t0+126.5s to t0+510.6s : R > 18.0 Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction. N.B. Galactic coordinates are lon=267.1250 lat=+15.3187 and the galactic extinction in R band is 0.3 magnitudes estimated from D. Schlegel et al. 1998ApJ...500..525S. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5980 SUBJECT: GRB 061218: TAROT La Silla observatory early optical observations DATE: 06/12/25 01:46:47 GMT FROM: Alain Klotz at CESR-CNRS Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report: We solve technichal problems that prevent to acces to the first trailed image of GRB 061218 obtained with TAROT located at the European Southern Observatory, La Silla observatory, Chile. The observations started 61s after the GRB trigger (4s after the notice). The trailed image allows to follow continuously variable sources during the 60s integration time (see technichal description in Klotz et al., 2006, A&A 451, L39). We analyzed the GRB error box provided by Sato et al. GCN Circ. 5940. No variable object is detected. To summarize: t0+ 61.0s to t0+121.0s : R > 15.8 t0+126.5s to t0+156.5s : R > 17.4 (CGNC 5943) t0+162.3s to t0+192.3s : R > 17.4 (CGNC 5943) t0+126.5s to t0+510.6s : R > 18.0 (CGNC 5943) Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction. This message may be cited.