//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8355 SUBJECT: GRB 081011: Swift detection of a burst DATE: 08/10/11 00:57:02 GMT FROM: David Palmer at LANL D. Grupe (PSU), A. P. Beardmore (U Leicester), P. A. Evans (U Leicester), S. T. Holland (CRESST/USRA/GSFC), E. A. Hoversten (PSU), J. A. Kennea (PSU), C. B. Markwardt (CRESST/GSFC/UMD), F. E. Marshall (NASA/GSFC), D. M. Palmer (LANL), J. L. Racusin (PSU), 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 00:28:50 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 081011 (trigger=331332). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 220.361, +33.607 which is RA(J2000) = 14h 41m 27s Dec(J2000) = +33d 36' 27" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single complex peak structure with a duration of about 15 sec. The peak count rate was ~1100 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 00:30:24.4 UT, 93.9 seconds after the BAT trigger. No source was detected in the promptly available XRT data. This is highly unusual for a long GRB with a prompt Swift slew. We are waiting for the full dataset to detect and localise the XRT counterpart. UVOT took a finding chart exposure of 150 seconds with the White (160-650 nm) filter starting 98 seconds after the BAT trigger. No afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 25% of the BAT error circle. The typical 3-sigma upper limit has been about 18.5 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the BAT 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. Burst Advocate for this burst is D. Grupe (grupe 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: 8357 SUBJECT: GRB 081011, Swift-BAT refined analysis DATE: 08/10/11 13:38:06 GMT FROM: Takanori Sakamoto at NASA/GSFC T. Sakamoto (GSFC/UMBC), 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), K. McLean (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC), G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 081011 (trigger #331332) (Grupe, et al., GCN Circ. 8355). The BAT ground-calculated position is RA, Dec = 220.363, 33.548 deg which is RA(J2000) = 14h 41m 27.2s Dec(J2000) = +33d 32' 54.4" with an uncertainty of 2.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows two peaks around T+2 and T+9 sec. There is a hint of a weak extended emission until T+60 sec. T90 (15-350 keV) is 9 +- 2 sec (estimated error including systematics). The time-averaged spectrum from T-0.9 to T+9.0 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 1.6 +- 0.3 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+1.06 sec in the 15-150 keV band is 0.4 +- 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/331332/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8358 SUBJECT: GRB 081011: Swift/XRT detection DATE: 08/10/11 14:38:39 GMT FROM: Jamie A. Kennea at PSU/Swift-XRT J. A. Kennea and D. Grupe (PSU) report on behalf of the Swift/XRT Team We have analyzed downlinked data from the XRT observations of GRB 081011 (Grupe et al, GCN #8355). The XRT began observing the field at 00:30:24.4 UT, 94 seconds after the BAT trigger. Data from the first orbit of observations reveal an uncatalogued fading point source at RA, Dec = 220.34435, +33.544771 which is the equivalent to: RA(J2000) = 14h 41m 22.6s Dec(J2000) = +33d 32m 41.1s with an estimated uncertainty of 8 arcseconds radius (90% confidence). This position is 57 arcseconds from the BAT refined position (Sakamoto et al, GCN #8357). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8359 SUBJECT: GRB081011: UVOT detection of an optical afterglow DATE: 08/10/11 17:57:02 GMT FROM: Patricia Schady at MSSL/Swift P. Schady (MSSL-UCL) and D.Grupe (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT observed the field of GRB 081011 (Grupe et al., GCN Circ. 8355) with settled exposures starting 99s after the trigger. A new fading source is detected in the white and u-band finding chart (fc) exposures and marginally in a co-added b-band exposure at RA(J2000) = 14:41:22.627 (220.34428) Dec(J2000) = +33:32:37.12 (+33.54364) consistent with the XRT position (Kennea et al., GCN Circ. 8358). These detections imply an upper limit on the redshift of z < ~3.8. The source is decaying with an approximate optical decay rate of alpha~1.1 (where the afterglow flux is proportional to t^-alpha). The detections and 3 sigma upper limits in the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627) are: Filter      T_start T_stop  Exp  Mag or 3-sigma UL             (s)     (s)     (s) ======================================================== white (FC)  99      249     145.8  19.25 +/- 0.08 white       537     1878    283.5   20.33 +/- 0.13 u (FC)      257     507     245.8   18.62 +/- 0.10 u           660     2003    155.6   19.91 +/- 0.30 v           586     7371    548.8   > 20.29 b           512     6756   351.4   21.13 +/- 0.39 uvw1        636     7781   548.8   > 20.96 uvm2        611     7576    548.9  > 20.74 uvw2        562     7167   548.8   > 21.06 The values quoted above are not corrected for the expected Galactic extinction corresponding to a reddening of E(B-V) = 0.01 mag in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8360 SUBJECT: Revised table for GRB 081011 UVOT detections DATE: 08/10/11 18:08:10 GMT FROM: Patricia Schady at MSSL/Swift P. Schady (MSSL-UCL) report on behalf of the Swift/UVOT team: Due to formatting problems, the data table in GCN Circ 8359 (Schady et al.) is unreadable. Below is the properly formatted version of the UVOT data table for GRB 0810111 Filter T_start T_stop Exp Mag or 3-sigma UL (s) (s) (s) ===================================================- white (FC) 99 249 145.8 19.25 +/- 0.08 white 537 1878 283.5 20.33 +/- 0.13 u (FC) 257 507 245.8 18.62 +/- 0.10 u 660 2003 155.6 19.91 +/- 0.30 v 586 7371 548.8 > 20.29 b 512 6756 351.4 21.13 +/- 0.39 uvw1 636 7781 548.8 > 20.96 uvm2 611 7576 548.9 > 20.74 uvw2 562 7167 548.8 > 21.06 The values quoted above are not corrected for the expected Galactic extinction corresponding to a reddening of E(B-V) = 0.01 mag in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8380 SUBJECT: GRB 081011: Enhanced Swift-XRT position DATE: 08/10/16 17:19:43 GMT FROM: Phil Evans at U of Leicester M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team. Using 12236 s of XRT Photon Counting mode data and 7 UVOT images for GRB 081011, 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 = 220.34404, +33.54332 which is equivalent to: RA (J2000): 14h 41m 22.57s Dec (J2000): +33d 32' 35.9" with an uncertainty of 1.5 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 http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an extension of this method. This circular was automatically generated, and is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 8385 SUBJECT: GRB 081011: Swift XRT refined analysis DATE: 08/10/17 14:10:54 GMT FROM: Dirk Grupe at PSU/Swift-XRT Dirk Grupe (PSU) reports on behalf of the Swift-XRT team: The XRT began observing the field of GRB 081011 (trigger=331332; Grupe et al., GCN Circ 8355) on 2008 October 11 00:30:24.4 UT, 93.9 s after the BAT trigger. The enhanced XRT position given in GCN Circ 8380 (Goad et al.) is 59.3" away from the ground-processed BAT position given in GCN Circ. 8357 (Sakamoto et al.), consistent with that position. This position was outside the central 200x200 pixel XRT window which is telemetered as SPER data, hence the non-detection reported in GCN 8357. The 0.3-10 keV X-ray light curve starts at a level of 7e-11 ergs/s/cm2 (1.8 counts/s) in the XRT with a steep decay slope at these early times of alpha1 = 1.10+/-0.23 The light curve breaks at about 4+/-2 ks after the burst and flattens to alpha2 = 0.24+/-0.17. Due to the proximity to the sun constraint, it was decided to cancel the observations after the first day. No further observations are planned and possible due the sun constraint. The spectrum of the Photon Counting mode data can be fitted by an absorbed single powerlaw with a photon index Gamma = 2.04 +/- 0.13 and column density fixed to the Galactic value of 1.04e20 cm-2 in the direction of the burst. The count rate to observed flux conversion factor is 2.2e-11 (ergs/s/cm2)/(counts/s) in the 0.3-10 keV band. This Circular is an official product of the Swift-XRT team.