//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7012 SUBJECT: GRB 071028: Swift detection of a burst DATE: 07/10/28 18:00:32 GMT FROM: Scott Barthelmy at NASA/GSFC J. L. Racusin (PSU), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), G. Cusumano (INAF-IASFPA), N. Gehrels (NASA/GSFC), C. Gronwall (PSU), J. A. Kennea (PSU), H. A. Krimm (GSFC/USRA), F. E. Marshall (NASA/GSFC), P. T. O'Brien (U Leicester), C. Pagani (PSU), D. M. Palmer (LANL), P. Romano (Univ. Bicocca & INAF-OAB), M. Stamatikos (NASA/ORAU), M. C. Stroh (PSU), T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the Swift Team: At 17:41:01 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 071028 (trigger=295527). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 119.847, +21.498 which is RA(J2000) = 07h 59m 23s Dec(J2000) = +21d 29' 52" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). Even though this is an image trigger, there is an indication of activity from about T+20 sec to T+50 sec. The peak count rate was ~400 counts/sec (15-350 keV), at ~25 sec after the trigger. The XRT began observing the field at 17:42:59 UT, 118 seconds after the BAT trigger. Using prompt downlinked data, we find a bright, variable, uncatalogued X-ray source located at RA, Dec 119.8176, 21.4841 which is RA(J2000) = 07 59 16.22 Dec(J2000) = +21 29 02.8 with an uncertainty of 4.1 arcsec (radius, 90% containment). This location is 106 arcseconds from the BAT on-board position, within the BAT error circle. The initial flux in the 2.5s image was 7.2e-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 128 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. There is a bright (12th mag) star in the XRT error circle which severely limits our ability to detect a possible afterglow. No correction has been made for extinction. Burst Advocate for this burst is J. L. Racusin (racusin AT astro.psu.edu). 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: 7013 SUBJECT: GRB 071028, Swift-BAT refined analysis DATE: 07/10/28 21:31:20 GMT FROM: Scott Barthelmy at NASA/GSFC J. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL), J. L. Racusin (PSU), T. Sakamoto (GSFC/UMBC), 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-239 to T+541 sec from the recent telemetry downlink, we report further analysis of BAT GRB 071028 (trigger #295527) (Racusin, et al., GCN Circ. 7012). The BAT ground-calculated position is RA, Dec = 119.828, 21.473 deg, which is RA(J2000) = 07h 59m 18.6s Dec(J2000) = 21d 28' 22" with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows a single FRED-like peak starting at ~T_zero, peaking at ~T+35 sec, and ending at ~T+110 sec. T90 (15-350 keV) is 27.0 +- 1.0 sec (estimated error including systematics). The time-averaged spectrum from T+19.2 to T+48.9 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.87 +- 0.26. The fluence in the 15-150 keV band is 3.0 +- 0.5 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+41.75 sec in the 15-150 keV band is 0.3 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7014 SUBJECT: GRB 071028: Swift-XRT Team refined analysis DATE: 07/10/28 23:13:12 GMT FROM: Judith Racusin at PSU J. Racusin (PSU) reports on behalf of the Swift-XRT Team: We have analysed the first 2 orbits of Swift-XRT data obtained for GRB 071028 (Racusin et al. GCN Circ. 7012), totaling 61 s of Windowed Timing (WT) data and 2.9 ks of Photon Counting (PC) data. Using 399 s of overlapping XRT Photon Counting mode and UVOT V-band data, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 119.81936, 21.48482 which is equivalent to: RA (J2000): 07 59 16.65 Dec (J2000): +21 29 05.4 with an uncertainty of 1.9 arcsec (radius, 90% confidence). This is 6.5 arcsec from the previous XRT position (GCN Circ. 7012), and 51 arcsec from the refined BAT position (Cummings et al., GCN Circ. 7013). The bright X-ray light-curve can be fit by a broken power-law, with an initial steep decay index of 3.3 +/- 0.4 followed by a flatter decay index of 1.1 +/- 0.3 after a break at 475 +/- 150 seconds. The WT data (124-182 seconds) can be modeled as an absorbed power-law, with photon index of 1.9 +/- 0.2 and a total absorbing column of NH = (5.9 +/- 5.6)e20 cm^-2, consistent with the Galactic value of 5.1e20 cm^-2. The 0.3-10 keV observed (unabsorbed) flux during this time is 3.1e-10 (3.6e-10) erg cm^-2 s^-1. Assuming the source continues to decay with the same decay index of 1.1, we predict an XRT count rate of 5.5e-4 counts/s at T+24 hours, which corresponds to an 0.3-10.0 keV observed flux of 2.3e-14 ergs cm^-2 s^-1. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7015 SUBJECT: GRB071028: Xinglong EST V-band upper limit DATE: 07/10/29 03:32:13 GMT FROM: L.P. Xin at NAOC L.P. Xin, M. Zhai, Y.L. Qiu, J.Y. Wei, J.Y. Hu, J.S. Deng, J. Wang and W.K. Zheng on behalf of EAFON report: We have imaged the field of GRB071028 (J. L. Racusin, GCN7012 ; J. Cummings, GCN7013; J. Racusin, GCN7014) with EST 1m telescope at Xinglong Observatory. The observations were started from 17:57:16 UT, 16.25min after the burst. A series of V-band images were obtained . No new source was found in our combined images within the error region of the XRT (J. L. Racusin, GCN7012) but We found the location reported by J. Racusin(GCN7014) was consisting with a very bright star in USNO-B1.0. The 3 sigma limit of our V-band combined images derived from USNO-B1.0 R2mag were : ------------------------------------ Band Mid time Exp time Limit Mag V 30min 19*60 19.8 V 1.19hours 9*300s 19.98 V 2.98hours 14*600s 20.09 This message may be cited //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7016 SUBJECT: Swift UVOT upper limits to GRB071028 DATE: 07/10/29 17:12:39 GMT FROM: Patricia Schady at MSSL/Swift P. Schady (MSSL/UCL) and J.L. Racusin (PSU) report on behalf of the Swift UVOT team: The Swift/UVOT observed the field of GRB 071028 (GCN 7012; Racusin et al.) beginning 128 seconds after the BAT trigger. No afterglow is detected in any of the UVOT filters within the XRT error circle (Racusin et al., GCN 7014). As already noted by Xin et al. (GCN 7015), the refined XRT position (Racusin et al., GCN 7014) lies next to a very bright star (V<10 mag), severely limiting the detection of an optical afterglow. In the case of the white band and optical filters (v,b,u), contamination from the nearby, bright star is causing the exposures to be affected by coincidence loss to a degree that is outside the photometrically calibrated range of UVOT. This limits the depth of our observations at the XRT position in these filters to white > 13.86, v > 11.46, b > 12.68 and u > 11.91. The 3-sigma upper limits at the XRT position in co-added UV exposures are as follows: Filter Tmid Exp Magnitude (s) (s) (3-sigma UL) uvw1 5044 412 > 19.89 uvm2 4847 413 > 20.32 uvw2 5014 213 > 19.67 where Tmid is the mid time of the observations. The values quoted above are not corrected for the expected Galactic extinction corresponding to a reddening of E_{B-V} = 0.06 mag in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7017 SUBJECT: GRB 071028: SARA observations of variable source DATE: 07/10/29 21:58:11 GMT FROM: Adria C. Updike at Clemson U Adria C. Updike, Dieter H. Hartmann (Clemson University) and Gary D. Henson (ETSU) report on behalf of the Clemson GRB Follow-Up Team: We observed the field of GRB 071028 (GCN 7012, Racusin et al.) with the 0.9m SARA telescope on Kitt Peak beginning 15 hours and 25 minutes after the trigger. Under variable cloud cover, we detect an apparently fading source within the BAT circle, but outside the revised XRT position (GCN 7014, Racusin et al.), at RA=07:59:15.22, Dec=+21:28:32.052 (+/- 2 arcsec, J2000). This candidate source is approximately 0.5 arcmin to the SW of the revised XRT position. In an hour of exposures, the source faded from R ~ 17 to beyond our detection limit (R limit ~ 18.5 in a single 120s exposure). The source was calibrated relative to 10 field stars in the USNO B1.0 catalog. The separation between the candidate OT and the revised XRT position makes this very unlikely to be the afterglow of GRB 071028. Second epoch observations may be required to establish the nature of this source. The SARA website can be found at http://astro.fit.edu/sara/sara.html . This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7019 SUBJECT: GRB 071028B Swift-BAT detection of a burst DATE: 07/10/30 13:19:51 GMT FROM: Jay R. Cummings at NASA/GSFC/Swift J. R. Cummings (CRESST/NASA/GSFC) and J. Greiner (MPE) for the Swift team At 02:43:46 UT on October 28, the Swift Burst Alert Telescope (BAT) triggered on GRB 071028B (trigger #295492). The burst was on the edge of the field of view (4.1% coded) and no source was found automatically onboard. A source was found during later ground analysis at a location RA, Dec 354.163, -31.630 which is RA(J2000) = 23h 36m 39s Dec(J2000) = -31d 37' 47" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows two FRED peaks, the first at T+1 sec about 4 seconds long, the second at T+48 sec about 9 seconds long. The peak count rate was about 1500 counts/sec (15-350 keV), at ~1 sec after the trigger. Because the burst was detected on the ground, there are no prompt XRT or UVOT data. A Swift TOO has been scheduled for October 30, at approximately 1400 UT. There have been several ground-detected Swift-BAT bursts lately: GRB 071006 (GCN circ #6858), GRB 071010C (GCN circ #6906) and this one. We have not changed our procedures substantially, and we do not believe that we have missed many such bursts in the past. It apparently is merely an odd statistical fluctuation of rare events: Two weak bursts on the edge of the BAT field of view and another immediately before a preplanned slew maneuver. Five such bursts have been noted before, one occurring just before a preplanned slew, GRB 051012 (GCN circ #4093), one combining both factors, GRB 070227 (GCN circ #6156), and the other three being very weak/short, GRB 051114 (GCN circ #4272), GRB 060505 (GCN circ #5076), and GRB 070406 (GCN circ #6247). A fifth nearly similar case was a very long and weak burst, GRB 060123 (GCN circ #4608), producing a significant detection onboard though automatic long-image triggers were not enabled at that time. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7040 SUBJECT: Swift XRT and UVOT observations of GRB071028B DATE: 07/11/03 03:33:32 GMT FROM: Dirk Grupe at PSU/Swift-XRT Dirk Grupe (PSU) and Patricia Schady (MSSL/UCL) report on behalf of the Swift team: The Swift XRT began observing the field of GRB 071028B (GCN 7019; Cummings 2007) on 2007 October 30 13:36 UT approximately 212 ks after the burst. Note that this burst was discovered in ground processing of the BAT data. Therefore no immediate observations after the burst were performed. There are clearly three sources within the 3' BAT error circle. The brightest of these (0.01 counts/s) coincides with a known source listed in the USNO catalogue. There is one source nearly at the center of the BAT error circle at RA-2000, Dec-2000 354.16300, -31.62050 which corresponds to RA-2000 = 23 36 39.1 Dec-2000 = -31 37 13.8 with a 4.8" XRT error circle. The second source is located at 354.11579, -31.63948 corresponding to RA-2000: 23 36 27.8 Dec-2000: -31 38 22.1 with a 4.8" XRT error circle. UVOT observed the field of GRB 071028B for a total of 6443s in the V-filter. There is no optical counterpart within the XRT error circles of the first and second source. The 3-sigma upper limits are V > 21.3mag and V >21.6 mag, respectively. These values are not corrected for the expected Galactic extinction corresponding to a reddening of E(B-V) = 0.02 mag in the direction of the burst (Schlegel et al. 1998). There are no counterparts at either of the source positions in the USNO catalogue within the XRT error radius (90% containment). This circular is an official product of the Swift team //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 7064 SUBJECT: Swift XRT follow-up observations of GRB071028B DATE: 07/11/12 20:25:48 GMT FROM: Dirk Grupe at PSU/Swift-XRT Dirk Grupe (PSU) reports on behalf of the Swift XRT team: The Swift XRT re-observed the field of GRB 071028B (GCN 7019; Cummings 2007) on 2007 November 07 for 9 ks and 2007 November 10 for 11ks. Clearly the first source listed in GCN Circ 7040 (Grupe & Schady, 2007) had faded while the second source is still visible at a similar level as reported in GCN 7040. It is therefore clear that this first source was the X-ray afterglow of GRB 070128, since its flux decreased. The position of the X-ray afterglow of GRB 071028B is RA-2000, Dec-2000 354.16300, -31.62050 which corresponds to RA-2000 = 23 36 39.1 Dec-2000 = -31 37 13.8 with a 4.8" XRT error circle. The 3-sigma upper limit at the position of the burst combining both data sets (20ks) is 6.7e-4 counts/s which converts roughly to 3e-14 ergs/s/cm2. This circular is an official product of the Swift team