//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5776 SUBJECT: GRB 061102: Swift detection of a burst DATE: 06/11/02 01:20:42 GMT FROM: Scott Barthelmy at NASA/GSFC S. T. Holland (GSFC/USRA), S. D. Barthelmy (GSFC), M. M. Chester (PSU), N. Gehrels (NASA/GSFC), C. Gronwall (PSU), J. A. Kennea (PSU), F. E. Marshall (NASA/GSFC), K. M. McLean (LANL/UTD), K. L. Page (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC), M. Stamatikos (NASA/ORAU) and R. L. C. Starling (U Leicester) report on behalf of the Swift Team: At 01:00:31 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 061102 (trigger=236430). Swift slewed immediately to the burst. The BAT on-board calculated location is RA,Dec 148.405, -17.066 {09h 53m 37s, -17d 03' 58"} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a weak pulse ~15 sec long. The peak count rate was ~500 counts/sec (15-350 keV) at ~5 sec after the trigger. The XRT began observing the field at 01:02:11 UT, 100 seconds after the BAT trigger. XRT found an uncatalogued fading X-ray source located at RA(J2000) = 09h 53m 37.7s, Dec(J2000) = -17d 01' 28.1", with an estimated uncertainty of 6.1 arcseconds (90% confidence radius). This location is 150 arcseconds from the BAT on-board position, within the BAT error circle. The initial flux in the 2.5s image was 6.0e-10 erg/cm2/s (0.2-10 keV). UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 110 seconds after the BAT trigger. No 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 3-sigma upper limit is approximately 18.5 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.04. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5777 SUBJECT: GRB 061102, Swift-BAT refined analysis DATE: 06/11/02 04:39:10 GMT FROM: Scott Barthelmy at NASA/GSFC GRB 061102, Swift-BAT refined analysis J. Tueller (GSFC), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), S.T. Holland (GSFC/USRA), D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU) on behalf of the Swift-BAT team: Using the data set from T-120 to T+182 sec from the recent telemetry downlink, we report further analysis of BAT GRB 061102 (trigger #236430) (Holland, et al., GCN Circ. 5776). The BAT ground-calculated position is RA,Dec = 148.393, -17.000 deg {9h 53m 34.2s, -17d 0' 0.8"} (J2000) +- 2.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted lightcurve shows a FRED starting at T+0 and ending about T+50 sec. T90 (15-350 keV) is 17.6 +- 1 sec (estimated error including systematics). The time-averaged spectrum from T-1.0 to T+18.9 is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.45 +- 0.33. The fluence in the 15-150 keV band is 1.9 +- 0.4 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+3.37 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: 5778 SUBJECT: GRB 061102B: Swift detection of a possible burst DATE: 06/11/02 06:41:41 GMT FROM: Scott Barthelmy at NASA/GSFC S. T. Holland (GSFC/USRA), A. M. Parsons (GSFC), L. M. Barbier (NASA/GSFC), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), D. N. Burrows (PSU), P. A. Evans (U Leicester), C. Gronwall (PSU), C. B. Markwardt (GSFC/UMD), K. L. Page (U Leicester), D. M. Palmer (LANL) and M. Stamatikos (NASA/ORAU) report on behalf of the Swift Team: At 06:13:16 UT, the Swift Burst Alert Telescope (BAT) triggered and located possible GRB 061102B (trigger=236481). Swift slewed immediately to the burst. The BAT on-board calculated location is RA,Dec 309.881, +15.179 {20h 39m 31s, +15d 10' 44"} (J2000) with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). This is a 32 msec trigger and the TDRSS lightcurve shows nothing significant. Therefore, it is possible that this trigger is due to a cosmic ray shower event in the spacecraft. We will not be able to separate the burst and shower possibilities until we receive the full data set in 2 hours. The XRT began taking data at 06:14:38 UT, 83 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. There is no source in the quicklook downlinked data products, which have an exposure time of about 250 s, giving us a rough upper limit of 2E-12 ergs/cm2/s for any point source in the field of view. We are waiting for full down-linked data to make a more sensitive search for a possible point source. The UVOT began observing at 06:14:44, 89 s after the BAT trigger with the White (160-650 nm) filter. No source is detected inside the BAT error circle. The 3-sigma upper limit is approximately V = 18 mag. No correction has been made for the expected Galactic extinction of E_{B-V} = 0.09 mag. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5780 SUBJECT: GRB061102B: Super-LOTIS observations DATE: 06/11/02 08:19:29 GMT FROM: Peter A. Milne at Super-LOTIS P.A.Milne, G.G.Williams (Steward Obs), H.-S.Park (LLNL), on behalf of the Super-LOTIS GRB team report: We observed the field of GRB 061102B (SWIFT trigger 236481) starting at UT=06:13:54 (38s after the BAT trigger), with the 0.6m SLOTIS telescope at Kitt Peak, AZ. We obtained 5 x 10-sec, 5 x 20-sec and 30 x 30-sec images during the observation at failry high airmass. Comparison of the resulting co-added images to the relevant DSS2 image reveals no new sources within the BAT error circle (Holland et al., GCN 5778). No fading source was detected when comparing early and late epoch summed images. We estimate a 3-sigma upper limit of R ~ 19.8 mag. for the 5 x 10-sec exposures. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5781 SUBJECT: Swift-BAT Trigger 236481 is a Cosmic Ray Shower event DATE: 06/11/02 09:51:01 GMT FROM: Scott Barthelmy at NASA/GSFC L. Barbier (GSFC), S.D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), S.T Holland (GSFC/USRA), D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) on behalf of the Swift-BAT team: The BAT trigger 236481 (Holland et al, GCN Circ 5778) is not a GRB. It is due to a cosmic ray shower in the spacecraft. All 60 events recorded in the BAT detector array occurred within a single 100 microsecond timestamp interval. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5783 SUBJECT: GRB 061102, XRT refined analysis DATE: 06/11/02 13:59:45 GMT FROM: Rhaana Starling at GRACE/U of Amsterdam R. L. C. Starling, K. L. Page (U Leicester) and S. T. Holland (GSFC/USRA) report on behalf of the Swift XRT team: We have analysed the first 3 orbits of Swift XRT data obtained for GRB 061102 (trigger 236430, GCN 5776 Holland et al.). The data consist of 208 s of WT mode data beginning at 112s since BAT trigger and 2560s of subsequent PC mode data. Using the PC mode data we obtain a refined position of: RA(J2000) = 09 53 37.64 Dec(J2000) = -17 01 26.5 with an estimated uncertainty of 4.9 arcsec (90% containment) taking into account the new TELDEF files. This location is 1.8 arcsec from the initial XRT position (GCN Circ. 5776) and 98.7 arcsec from the ground-calculated BAT position (GCN Circ. 5777; Tueller et al.) The lightcurve shows a steep decay over the first 400s with a slope of alpha = 4.0+/-0.1. At ~400s the lightcurve breaks to a slope of alpha~1. The first orbit WT-mode spectrum can be well fitted with an absorbed power law with index Gamma = 3.6+/-0.2. The total column density required is 1.6E21 cm^-2 which exceeds the Galactic value of 5.0E20 cm^-2 (Dickey & Lockman 1990). The total flux in the 0.3-10 keV band is 1.2E-10 erg cm^-2 s^-1. All errors are quoted at the 90% confidence limit. From these data we predict a count rate of 3.3E-4 counts s^-1, corresponding to a flux of approximately 8E-15 erg cm^-2 s^-1 at T+24h. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 5784 SUBJECT: GRB 061102: Swift/UVOT Magnitude Upper Limits DATE: 06/11/02 14:37:28 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC GRB 061102: Swift/UVOT Magnitude Upper Limits S. T. Holland (NASA/GSFC & USRA) reports on behalf of the Swift/UVOT team: The Swift/UVOT began observing the field of GRB 061102 at 01:02:02 on 2006-11-02, 92 s after the BAT trigger (Holland et al., GCN Circ. 5776). No optical afterglow was detected in any of the individual UVOT exposures, or in the coadded exposures, down to the following 3-sigma limiting magnitudes. The start and stop times are relative to the BAT trigger. Filter Start Stop Exposure 3-sigma (s) (s) (s) Upper Limit Finding Charts White 112 209 97 19.9 V 216 275 59 18.3 Coadded Exposures V 216 10154 1141 20.5 B 4078 16849 1278 21.6 U 3873 15938 1278 21.3 UVW1 3669 11845 1160 21.3 UVM2 3464 11059 1279 21.7 UVW2 4488 6061 336 20.9 White 112 17629 1247 21.5 The values quoted above are not corrected for the expected Galactic extinction of E_{B-V} = 0.04 mag (Schlegel et al. 1998).