//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10799 SUBJECT: GRB 100526B: Swift detection of a probable GRB DATE: 10/05/26 19:13:54 GMT FROM: Scott Barthelmy at NASA/GSFC M. H. Siegel (PSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU), J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC), J. M. Gelbord (PSU), D. Grupe (PSU), S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU), H. A. Krimm (CRESST/GSFC/USRA), D. M. Palmer (LANL), T. A. Pritchard (PSU), P. Romano (INAF-IASFPA), T. Sakamoto (NASA/UMBC), M. A. Stark (PSU), E. Troja (NASA/GSFC/ORAU) and L. Vetere (PSU) report on behalf of the Swift Team: At 19:00:38 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 100526B (trigger=423184). The slew was delayed due to an observing constraint. The BAT on-board calculated location is RA, Dec 0.700, -37.902 which is RA(J2000) = 00h 02m 48s Dec(J2000) = -37d 54' 07" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve shows a few weak peaks with a duration of about ~30 sec. The peak count rate was ~1000 counts/sec (15-350 keV), at ~3 sec after the trigger. Due to an observing constraint, Swift will not slew until T0+54 minutes. There will be no XRT or UVOT data until this time. Burst Advocate for this burst is M. H. Siegel (siegel 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: 10802 SUBJECT: GRB 100526B: Swift XRT/UVOT observations DATE: 10/05/26 20:30:55 GMT FROM: Jamie A. Kennea at PSU/Swift-XRT J. A. Kennea, L. Vetere and M. Siegel (PSU) report on behalf of the Swift team: The XRT began observing the field of GRB 100526B at 19:55:21.1 UT, 3282.6 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 0.73552, -37.91195 which is equivalent to: RA(J2000) = 00h 02m 56.52s Dec(J2000) = -37d 54' 43.0" with an uncertainty of 5.6 arcseconds (radius, 90% containment). This location is 107 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at http://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 1.12e+20 cm^-2 (Kalberla et al. 2005). UVOT took a finding chart exposure of 150 seconds with the White filter starting 3288 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT 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 0.01. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10803 SUBJECT: GRB 100526B: Swift-BAT refined analysis DATE: 10/05/26 21:58:32 GMT FROM: Scott Barthelmy at NASA/GSFC J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), M. H. Siegel (PSU), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-60 to T+243 sec from the recent telemetry downlink, we report further analysis of BAT GRB 100526B (trigger #423184) (Siegel, et al., GCN Circ. 10799). The BAT ground-calculated position is RA, Dec = 0.777, -37.913 deg, which is RA(J2000) = 00h 03m 06.5s Dec(J2000) = -37d 54' 48.4" with an uncertainty of 3.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 95%. The mask-weighted light curve shows a broad weak peak starting at ~T-25 sec, peaking around T+10 sec, and ending around t+50 sec. The burst location went out of the BAT FOV at T+240 sec when Swift was forced to slew due to an observing constraint. T90 (15-350 keV) is 64.0 +- 22.6 sec (estimated error including systematics). The time-averaged spectrum from T-28.4 to T+35.6 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.47 +- 0.28. The fluence in the 15-150 keV band is 4.7 +- 0.9 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+11.15 sec in the 15-150 keV band is 0.1 +- 0.1 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/423184/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10808 SUBJECT: GRB 100526B: Swift/UVOT Upper Limits DATE: 10/05/27 18:26:17 GMT FROM: Tyler Pritchard at PSU T. A. Pritchard (PSU) and Siegel (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 100526B 3288 s after the BAT trigger (Siegel et al., GCN Circ. 10799). No optical afterglow consistent with the XRT position (Kennea et al., GCN Circ. 10802) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag -------------------------------------------------------------- white (FC) 3288 3438 147 >21.3 white 3288 4669 344 >21.7 v 3445 5080 393 >20.2 b 4265 5880 372 >20.7 u 4060 5695 393 >20.5 w1 3855 5491 393 >20.7 m2 3650 3849 197 >19.9 w2 4675 4875 197 >20.3 The values quoted above are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10809 SUBJECT: GRB 100526B: Swift-XRT confirmation of fading afterglow DATE: 10/05/28 05:40:58 GMT FROM: Loredana Vetere at PSU L. Vetere and M. H. Siegel (PSU) report on behalf of the Swift-XRT team: We have now collected 5.7 ks of Swift-XRT Photon Counting mode data on the GRB 100526B (Siegel et al. GCN Circ. 10799), from 3289 s to 34.8 ks after the BAT trigger. The source reported by Kennea et al. (GCN Circ. 10802) is now only marginally detected, with a count rate of 1.5x10^-3 count s^-1 (corresponding to an observed flux of 7.1x10^-14 erg cm^-2 s^-1). With this fading, we can confirm that this source is the X-ray afterglow of GRB 100526B. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00423184. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10812 SUBJECT: GRB100526B: GROND Upper limits DATE: 10/05/28 10:03:44 GMT FROM: Paulo M. J. Afonso at MPE GRB 100526B: GROND Upper limits P. Afonso (MPE), A. Nicuesa (Tautenburg Obs.), R. Filgas and J. Greiner (all MPE Garching), report on behalf of the GROND team: We observed the field of GRB 100526B (Swift trigger #423184 ; Siegel et al., GCN #10799) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPI/ESO telescope at La Silla Observatory (Chile). Observations started at 09:37 UT on March 27, 14.6 hours after the GRB trigger, and were performed under strong wind. We do not detect a source within the Swift-XRT error circle reported by Kennea et al. (GCN #10802) in any of the GROND filters. Stacked images with a total integration time of 28 minutes in JHK and 32 minutes in g'r'i'z' yield the following preliminary 3-sigma upper limits: g' > 24.1 r' > 24.2 i' > 23.9 z' > 23.8 J > 22.7 H > 22.2 K > 21.3 All magnitudes given above are in the AB system and are based on the GROND zeropoints and 2MASS field stars. No correction has been applied for the Galactic foreground extinction corresponding to a reddening of E_(B-V)= 0.012 in the direction of the burst (Schlegel et al. 1998).