//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6584 SUBJECT: GRB 070628: Swift detection of a possible burst DATE: 07/06/28 15:01:09 GMT FROM: Scott Barthelmy at NASA/GSFC S. T. Holland (CRESST/GSFC/USRA), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), P. J. Brown (PSU), D. N. Burrows (PSU), S. Campana (INAF-OAB), M. L. Conciatore (ASDC), N. Gehrels (NASA/GSFC), C. Gronwall (PSU), C. Guidorzi (Univ Bicocca&INAF-OAB), J. A. Kennea (PSU), H. A. Krimm (GSFC/USRA), V. La Parola (INAF-IASFPA), V. Mangano (INAF-IASFPA), F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), M. Perri (ASDC), P. Romano (Univ. Bicocca & INAF-OAB), T. Sakamoto (NASA/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (NASA/ORAU) and T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team: At 14:41:02 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 070628 (trigger=283320). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 115.284, -20.285 which is RA(J2000) = 07h 41m 08s Dec(J2000) = -20d 17' 04" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a single peak on a rising background while entering the SAA with a duration of about 20 sec. The peak count rate was ~3000 counts/sec (15-350 keV), at ~5 sec after the trigger. Given the galactic latitude of +1.25deg, we can not rule out a Galactic transient origin of this trigger. The XRT began taking data at 14:42:53 UT, 111 seconds after the BAT trigger. The initial image mode frames show many cosmic ray tracks due to entrance into the SAA; the XRT on-board centroid algorithm did not find a source in the image and no prompt position is available. Further XRT data are delayed by the SAA passage. We are waiting for down-linked data to detect and determine a position for the source. Because Swift was entering the SAA, there were no prompt UVOT observations of this source. Burst Advocate for this burst is S. T. Holland (sholland AT milkyway.gsfc.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.) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6585 SUBJECT: Swift UVOT Observations of GRB 070628 DATE: 07/06/28 15:21:36 GMT FROM: Caryl Gronwall at PSU/Swift-UVOT Swift UVOT Observations of GRB 070628 C. Gronwall (PSU) and S. T. Holland (CRESST/GSFC/USRA) report on the behalf of the Swift UVOT team: In response to GRB 070628 (Swift/BAT trigger 283320) at 14:41:02.84 UT, UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm) filter starting 1099 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 07:41:06.12 = 115.2755 DEC(J2000) = -20:16:46.2 = -20.2795 with a 1-sigma error radius of about 0.6 arc sec. This position is 34.9 arcsec. from the center of the BAT error circle. The estimated magnitude is 19.1 with a 1-sigma error of about 0.5 mag. No correction has been made for extinction. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6586 SUBJECT: GRB 070628: Watcher Observations DATE: 07/06/28 21:56:11 GMT FROM: Gary Melady at UCD Gary Melady (University College Dublin), John French (UCD), Petr Kubanek (GACE Valencia), Martin Jelinek (IAA CSIC Granada) report on behalf of the Watcher collaboration: The Watcher 40cm robotic telescope, located at Boyden Observatory, South Africa, responded to Swift Trigger 283320 (GRB 070628, Holland et al. GCN 6584). when the dome opened at 15:17:29 UT, 36.43 minutes after the trigger. However the bright evening sky rendered the earliest images unusable. An unfiltered 60s exposure taken under twilight conditions at 16:12:48 UT, 91.76 minutes after the Swift trigger, showed no new source in the UVOT error box (as reported by Gronwall et al., GCN 6585) down to an R-band limiting magnitude of approx 16.2 (in comparison to USNO-B1). We combined 27 subsequent 60s exposures to create a 1620s unfiltered image with an exposure mid-time of 16:28:05 (108.05 minutes after the trigger). The later images were taken at high air mass as the target was setting. This shows no new source in the error box down to an R-band limiting magnitude of approx 17.2. The target set at our location at 18:20 UT so no further observations will be made. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6587 SUBJECT: GRB 070628: Swift XRT refined analysis DATE: 07/06/29 00:01:58 GMT FROM: Matteo Perri at ISAC/ASDC M. Perri, G. Stratta (ASDC) and S.T. Holland (CRESST/GSFC/USRA) report on behalf of the Swift XRT team: We have analysed the first 3 orbits of Swift XRT data from the possible burst GRB 070628 (Holland et al., GCN Circ. 6584). Using an exposure time of 6.3 ks the refined XRT position is RA (J2000) = 115.275833, Dec (J2000) = -20.279750, corresponding to: RA(J2000) = 07h 41m 06.2s Dec(J2000) = -20d 16' 47.1" with an uncertainty of 3.5" (90% containment). This is 0.5 arcmin from the BAT position (GCN Circ. 6584) and 1.4 arcsec from the UVOT position (Gronwall et al. GCN Circ. 6585). The XRT light-curve in the time interval from T+116s to T+14ks shows a fading behavior with superimposed flaring activity. More data are being collected to monitor the light-curve evolution. The X-ray spectrum covering the time period from T+1.1ks to T+14ks is well fit by an absorbed power law with a photon index of 2.2 +/- 0.1 and a total column density of NH=(7.5+/-0.7)e21 cm**-2. We note that the Galactic column density in the direction of the source is 7.35e21 cm**-2 (Dickey & Lockman 1990). This circular is an official product of the Swift XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6588 SUBJECT: GRB 070628: TAROT La Silla observatory optical observations DATE: 07/06/29 10:05:31 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 070628 detected by SWIFT (trigger 283320) with the TAROT robotic telescope (D=25cm) located at the European Southern Observatory, La Silla observatory, Chile. The observations started 8.3h after the GRB trigger (started at the begining of the night). The elevation of the field decreased from from 22 degrees above horizon and weather conditions were good. We co-added a series of exposures filtered in R, V and I. We do not detect any OT at the UVOT location (Gronwall & Holland GCN Circ. 6585): t0+8.3h to t0+9.1h : R > 17.9 Magnitudes were estimated with the nearby USNO-B1 stars and are not corrected for galactic dust extinction. N.B. Galactic coordinates are lon=236.5513 lat= +1.2335 and the galactic extinction in R band is 2.4 magnitudes estimated from D. Schlegel et al. 1998ApJ...500..525S. This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6589 SUBJECT: GRB 070628, Swift-BAT refined analysis DATE: 07/06/29 13:12:01 GMT FROM: Scott Barthelmy at NASA/GSFC H. Krimm (GSFC/USRA), L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC), S. T. Holland (CRESST/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), T. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+67 sec from recent telemetry downlinks, we report further analysis of BAT GRB 070628 (trigger #283320) (Holland, et al., GCN Circ. 6584). The BAT ground-calculated position is RA, Dec = 115.271, -20.281 deg which is RA(J2000) = 7h 41m 5.1s Dec(J2000) = -20d 16' 50" with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 58%. The mask-weighted light curve shows pretrigger emission starting at T-30 sec. Then comes the main emission peak (roughly symmetrical) starting at ~T-5 sec and ending at ~T+20 sec. T90 (15-350 keV) is 39.1 +- 2 sec (estimated error including systematics). The BAT data end at T+67 sec because Swift entered the SAA. The time-averaged spectrum from T-31.7 to T+16.2 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.91 +- 0.09. The fluence in the 15-150 keV band is 3.5 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+4.90 sec in the 15-150 keV band is 5.1 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6590 SUBJECT: GRB 070628: NIR detection of afterglow DATE: 07/06/29 19:54:12 GMT FROM: Jochen Greiner at MPI N. Primak, G. Szokoly, J. Greiner, C. Clemens, T. Kruehler, A. Kuepcue-Yoldas, A. Yoldas (all MPE Garching), S. Klose, A. Rossi (Tautenburg Observatory), and F. Carrier (Instituut voor Sterrenkunde Leuven, Belgium) report: We observed the field of GRB 070628 (Swift trigger 283320; Holland et al., GCN 6584) with GROND at the 2.2m Max-Planck Institute telescope at the ESO La Silla observatory in Chile. The observations started at 22:21:57, about 7.7 hrs after the GRB and just after sunset, and lasted 10 min. We observed simultaneously in the g,r,i,z,J,H,K bands. The UVOT afterglow (Cronwall & Holland, GCN 6585) is clearly detected at H=16.2+-0.3 and K=16.3+-0.2 mag. The NIR magnitudes are calibrated against 2MASS. Nothing is visible in the J band (limiting magnitude 16.0), and all optical frames are saturated due to twilight. We note that the afterglow was atypically bright for the given time after the burst, suggesting a slow fading. We encourage near-IR spectroscopy to determine the redshift. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 6591 SUBJECT: GRB 070628 Swift-UVOT Refined Analysis DATE: 07/06/30 00:43:01 GMT FROM: Wayne Landsman at GSFC/SSAI W. Landsman (GSFC/SSAI), F.E. Marshall (NASA/GSFC) and S.T. Holland (CRESST/GSFC/USRA) report on behalf of the Swift/UVOT team. The Swift/UVOT observed the field of GRB 070628 starting 1099 sec after the trigger (Holland et al., GCN Circ. 6584). We strongly detect the afterglow in the white and V filters, and have a weak detection in the B filter. The refined afterglow position is RA(J2000) = 07h 41m 06.09s Dec(J2000) = -20d 16' 45.4" with an uncertainty of 0.7" (radius, 90% containment, including systematic uncertainty). This is within the refined XRT error circle (Perri et al. GCN Circ. 6587). Magnitudes and upper limits are reported below. Filter Tstart Tstop Exp Mag (s) (s) (s) WHITE 1099 1199 98 19.65 ± 0.11 1202 1302 98 19.62 ± 0.11 6628 6827 197 20.59 ± 0.15 11691 11990 295 >21.2 (3 sigma) V 1309 1708 393 18.88 ± 0.11 1850 5804 256 19.55 ± 0.25 13207 13506 295 >19.6 (3 sigma) B 1786 6622 78 20.7 ± 0.3 7856 8055 197 >20.4 (3 sigma) U 6217 6417 197 >20.0 (3 sigma) UVW1 6014 6213 197 >19.8 (3 sigma) UVM2 5809 6008 197 >19.6 (3 sigma) UVW2 6833 7032 197 >19.9 (3 sigma) The above magnitudes are not corrected for the large and uncertain extinction expected at the low Galactic latitude of GRB 070628. A power-law fit to the white filter observations gives a decay index of ~0.55 +/- 0.3. [GCN OPS NOTE(30jun07): Per author's request, the authors line was added.]