//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 10998 SUBJECT: GRB 100727A: Swift detection of a burst DATE: 10/07/27 05:56:00 GMT FROM: David Palmer at LANL D. C. Morris (GWU/GSFC), M. M. Chester (PSU), J. M. Gelbord (PSU), C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC), H. A. Krimm (CRESST/GSFC/USRA), V. Mangano (INAF-IASFPA), P. T. O'Brien (U Leicester), K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB/IASFPA), M. H. Siegel (PSU), M. Stamatikos (OSU/NASA/GSFC) and R. L. C. Starling (U Leicester) report on behalf of the Swift Team: At 05:42:17 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 100727A (trigger=430094). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 154.166, -21.364 which is RA(J2000) = 10h 16m 40s Dec(J2000) = -21d 21' 51" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 50 sec, with possible additional activity around T+175. The peak count rate was ~3300 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 05:43:14.4 UT, 56.6 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 154.17823, -21.39002 which is equivalent to: RA(J2000) = 10h 16m 42.78s Dec(J2000) = -21d 23' 24.1" with an uncertainty of 3.9 arcseconds (radius, 90% containment). This location is 100 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 5.09e+20 cm^-2 (Kalberla et al. 2005). The initial flux in the 2.5 s image was 1.29e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 65 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 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. Data from the list of sources generated on-board are not available at this time. No correction has been made for the expected extinction corresponding to E(B-V) of 0.05. Burst Advocate for this burst is D. C. Morris (david.c.morris AT 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: 10999 SUBJECT: GRB100727A: MOA optical upper limit DATE: 10/07/27 09:53:01 GMT FROM: Shuhei Kobara at U.Nagoya/MOA-II S. Kobara, K. Omori, T. Sumi, D. Suzuki, H.Naito and T. Sako (STE Lab. , Nagoya Univ.) on behalf of the MOA Collaboration report : We searched for an optical afterglow of GRB100727A (GCN 10998, D. C. Morris et al.) starting from 07:12:3 UT on 2010 July 27 ( 90 minutes after the burst) with the MOA-II 1.8m telescope at Mt.John observatory in New Zealand. In a single image of a 300 sec exposure with a wideband Red filter (center wavelength ~ 750nm and FWHM ~ 250nm), we did not find any object within the error circle of the Swift XRT source position (GCN 10998, D. C. Morris et al. ). A 3 sigma upper limit is set in the I magnitude at 21.6 mag. This photometry was done by using the DoPhot and calibrated against the USNO-B1.0 catalog stars, and not corrected for the Galactic extinction. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11000 SUBJECT: GRB 100727A: Enhanced Swift-XRT position DATE: 10/07/27 12:49:07 GMT FROM: Phil Evans at U of Leicester J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 4198 s of XRT Photon Counting mode data and 8 UVOT images for GRB 100727A, 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 = 154.17739, -21.39042 which is equivalent to: RA (J2000): 10h 16m 42.57s Dec (J2000): -21d 23' 25.5" with an uncertainty of 1.6 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11001 SUBJECT: GRB 100727A, Swift-BAT refined analysis DATE: 10/07/27 14:00:16 GMT FROM: Hans Krimm at NASA-GSFC M. Stamatikos (GSFC/ORAU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), D. C. Morris (GWU/GSFC), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+617 sec from the recent telemetry downlink, we report further analysis of BAT GRB 100727A (trigger #430094) (Morris, et al., GCN Circ. 10998). The BAT ground-calculated position is RA, Dec = 154.187, -21.417 deg which is RA(J2000) = 10h 16m 44.8s Dec(J2000) = -21d 25' 02.7" with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment). The partial coding was 98%. The burst began with weak precursor activity starting at T-80 sec and peaking at T-40 sec. The main pulse, a mostly featureless FRED profile, began at T-2 sec and continued to approximately T+50 sec. T90 (15-350 keV) is 84 +- 14 sec (estimated error including systematics). The time-averaged spectrum from T-82.0 to T+29.8 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.81 +- 0.13. The fluence in the 15-150 keV band is 1.2 +- 0.1 x 10-6 erg/cm2. The 1-sec peak photon flux measured from T+1.33 sec in the 15-150 keV band is 1.2 +- 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/430094/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11002 SUBJECT: GRB 100727A: Fermi GBM observation DATE: 10/07/27 14:57:12 GMT FROM: Andreas von Kienlin at MPE A. von Kienlin (MPE) reports on behalf of the Fermi GBM Team: "At 05:42:22.00 UT on 27 July 2010, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 100727A (trigger 301902143 / 100727238), which was also detected by the SWIFT-BAT (Morris et al. 2010, GCN 10998) The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 95.1 degrees. The GBM light curve consists of single peak with a duration (T90) of about 24 +/- 3 s (50-300 keV). The time-averaged spectrum from T0-6.144 s to T0+12.288 s is best fit by a simple power law function with index -1.71 +/- 0.04 (Castor C-STAT 785 for 473 d.o.f.). The event fluence (8-1000 keV) in this time interval is (2.03 +/- 0.14)E-06 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0-4.096 s in the 8-1000 keV band is 1.6 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11003 SUBJECT: GRB 100727A: Swift XRT refined analysis DATE: 10/07/27 21:07:26 GMT FROM: Boris Sbarufatti at INAF-OAB/IASFPA B. Sbarufatti (INAF OAB/IASF PA), V. Mangano (INAF/IASF PA) and D. C. Morris (GWU/GSFC) report on behalf of the Swift-XRT team: We have analysed 9.8 ks of XRT data for GRB 100727A (Morris et al. GCN Circ. 10998), from 48 s to 39.8 ks after the BAT trigger. The data comprise 185 s in Windowed Timing (WT) mode (the first 7 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Osborne et al. (GCN. Circ 11000). The light curve can be modeled with a doubly broken power-law decay. The initial decay index is alpha=2.6 (+/-0.1). A bright flare starts at T+190 s and peaks at T+247 s. The light curve breaks at T+450 s entering a plateau phase with alpha=0.0 (+0.06 -0.08). The second break is observed at T+6.5 ks, followed by a decay index alpha=0.64 (+0.12-0.09) A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.8 (+/-0.14). The best-fitting absorption column is 4.2 (+/-0.3) x 10^21 cm^-2, in excess of the Galactic value of 5.1 x 10^20 cm^-2 (Kalberla et al. 2005). The PC mode spectrum has a photon index of 2.6 (+/-0.2) and a best-fitting absorption column of 3.1 (+/-0.5) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 9.7 x 10^-11 (2.3 x 10^-10) erg cm^-2 count^-1. If the light curve continues to decay with a power-law decay index of 0.64, the count rate at T+24 hours will be 2.8 x 10^-2 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.7 x 10-12 (6.4 x 10-12) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00430094. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 11019 SUBJECT: GRB 100727A: Swift/UVOT Upper Limits DATE: 10/07/28 16:14:12 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC S. T. Holland (CRESST/GSFC/USRA) and D. C. Morris (GWU/GSFC) report on the behalf of the Swift UVOT team: The Swift/UVOT observed the field of GRB 100727A starting 47 s after the BAT trigger (Morris, et al., 2010, GCN Circ. 10998). Settled observations started at 65 s. We do not find any new source, relative to the DSS, USNO-B1.0, or 2MASS at the position of the XRT afterglow (Osborne, et al. 2010, GCN Circ. 11000). Preliminary 3-sigma upper limits for detecting a source in the finding charts, and in the co-added images, using a 2.5 arcsecond radius circular aperture, are Filter T_start T_stop Exp(s) Mag ------------------------------------------------ white (fc) 65 215 147 >20.8 856 1006 147 >21.2 u (fc) 278 527 246 >20.5 v 609 18,409 1414 >20.9 b 533 24,918 1215 >21.7 u 278 24,189 2335 >21.7 uvw1 658 29,885 2289 >21.9 uvm2 633 28,542 2390 >21.8 uvw2 584 17,496 1415 >21.8 white 65 7075 805 >22.1 ------------------------------------------------ The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight corresponding to a reddening of E_{B-V} = 0.05 mag (Schlegel, et al., 1998, ApJS, 500, 525). All photometry is on the UVOT photometry system described in Poole et al. (2008, MNRAS, 383, 627).