//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19855 SUBJECT: GRB 160824A: Swift detection of a burst DATE: 16/08/24 23:40:59 GMT FROM: Kim Page at U.of Leicester P.A. Evans (U Leicester), S. B. Cenko (GSFC), H. A. Krimm (CRESST/GSFC/USRA), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester) and M. H. Siegel (PSU) report on behalf of the Swift Team: At 23:22:25 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 160824A (trigger=709765). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 80.078, +40.040 which is RA(J2000) = 05h 20m 19s Dec(J2000) = +40d 02' 25" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 40 sec. The peak count rate was ~2100 counts/sec (15-350 keV), at ~5 sec after the trigger. The XRT began observing the field at 23:23:56.5 UT, 91.1 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 80.0877, 40.0286 which is equivalent to: RA(J2000) = 05h 20m 21.05s Dec(J2000) = +40d 01' 43.1" with an uncertainty of 2.1 arcseconds (radius, 90% containment). This location is 48 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. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (6.32 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 4.7 (+6.16/-4.59) x 10^21 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 1.04e-08 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 101 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. 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 large, but uncertain extinction expected. Burst Advocate for this burst is P.A. Evans (pae9 AT star.le.ac.uk). 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: 19857 SUBJECT: GRB 160824A: Enhanced Swift-XRT position DATE: 16/08/25 07:28:12 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 2198 s of XRT Photon Counting mode data and 5 UVOT images for GRB 160824A, 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 = 80.08758, +40.02826 which is equivalent to: RA (J2000): 05h 20m 21.02s Dec (J2000): +40d 01' 41.7" with an uncertainty of 1.4 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: 19858 SUBJECT: GRB 160824A: Swift-XRT refined Analysis DATE: 16/08/25 12:29:35 GMT FROM: Phil Evans at U of Leicester B. Mingo (U. Leicester), A.P. Beardmore (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), T.G.R. Roegiers (PSU), L.M. McCauley (PSU), J.A. Kennea (PSU) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 10 ks of XRT data for GRB 160824A (Evans et al. GCN Circ. 19855), from 81 s to 29.6 ks after the BAT trigger. The data comprise 105 s in Windowed Timing (WT) mode (the first 8 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 Goad et al. (GCN Circ. 19857). The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=3.33 (+0.17, -0.18). At T+258 s the decay flattens to an alpha of 0.44 (+0.05, -0.06) before breaking again at T+7762 s to a final decay with index alpha=1.31 (+/-0.14). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.07 (+/-0.10). The best-fitting absorption column is 1.18 (+0.11, -0.10) x 10^22 cm^-2, in excess of the Galactic value of 6.3 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.96 (+/-0.13) and a best-fitting absorption column of 1.05 (+0.14, -0.13) x 10^22 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 5.0 x 10^-11 (9.1 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.05 (+0.14, -0.13) x 10^22 cm^-2 Galactic foreground: 6.3 x 10^21 cm^-2 Excess significance: 5.3 sigma Photon index: 1.96 (+/-0.13) If the light curve continues to decay with a power-law decay index of 1.31, the count rate at T+24 hours will be 0.018 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.8 x 10^-13 (1.6 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/00709765. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19859 SUBJECT: GRB 160824A: Bassano Bresciano Observatory upper limits DATE: 16/08/25 12:42:52 GMT FROM: Ulisse Quadri at Bassano Bresciano Obs U.Quadri, L.Strabla and R.Girelli report: We imaged the field of GRB 160824A detected by SWIFT(trigger 709765) with the robotic telescope of (IAU station 565) Bassano Bresciano Observatory, Italy. Member of: AAVSO - American Association of Variable Star Observers. ISSP - Italian Supernovae Search Project. UAI/SSV - Unione Astrofili Italiani/sezione stelle variabili. The observations started 20.77 min after the GRB trigger, with our Schmidt telescope D=320/400 mm F/D=3.1. Weather conditions not good for Moon proximity. We co-added 4 series of 20 exposures of 120 sec each. Start T0+ End T0+ CVlim 20.77 min 196.52 min 17.5 We did not found any optical counterpart in the error box of the XRTcandidate. P.A. Evans (U Leicester), S. B. Cenko (GSFC), et al. Magnitudes were estimated with the UCAC4 cat. and are not corrected for galactic dust extinction. Reference: http://www.osservatoriobassano.org/GRB.asp The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19860 SUBJECT: GRB 160824A: Swift/UVOT Possible Afterglow Detection DATE: 16/08/25 14:25:28 GMT FROM: Frank Marshall at GSFC F. E. Marshall (NASA/GSFC) and P. A. Evans (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 160824A 101 s after the BAT trigger (Evans et al., GCN Circ. 19855). UVOT marginally detects a source consistent with the enhanced XRT position (Goad et al. GCN Circ. 19857) in the initial UVOT exposure with the white filter. The preliminary analysis produces the following marginal detection and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373): Filter T_start(s) T_stop(s) Exp(s) Mag white 101 787 186 20.16 +/- 0.27 v 645 837 39 >17.9 b 571 763 39 >18.7 u 313 738 265 >19.7 w1 694 714 19 >18.5 m2 669 861 39 >19.2 w2 620 813 39 >18.5 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.69 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19861 SUBJECT: GRB 160824A: Swift-BAT refined analysis DATE: 16/08/25 16:50:54 GMT FROM: Hans Krimm at NASA-GSFC T. Sakamoto (AGU), S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC), P.A. Evans (U Leicester), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 160824A (trigger #709765) (Evans, et al., GCN Circ. 19855). The BAT ground-calculated position is RA, Dec = 80.087, 40.039 deg which is RA(J2000) = 05h 20m 20.8s Dec(J2000) = +40d 02' 21.6" with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 55%. The mask-weighted light curve shows two episodes of emission. The first runs from T-5 sec to roughly T+45 sec and contains multiple peaks. The second runs from T+85 sec to T+110 sec. T90 (15-350 keV) is 99.3 +- 7.8 sec (estimated error including systematics). The time-averaged spectrum from T-0.66 to T+111.58 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.64 +- 0.11. The fluence in the 15-150 keV band is 2.6 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+4.88 sec in the 15-150 keV band is 1.3 +- 0.2 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/709765/BA/ [GCN OPS NOTE(25aug16): Per author's request, the TBDs for the time range of the spectral average was filled in with the actual values.] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19862 SUBJECT: GRB 160824A: ISON/Terskol optical observations DATE: 16/08/25 18:20:16 GMT FROM: Alexei Pozanenko at IKI, Moscow E. Mazaeva (IKI), A. Mokhnatkin (KIAM), A. Volnova (IKI), Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration We observed the field of GRB 160824A (Evans et al., GCN 19855) with K-800 (0.8m f/2.9) telescope of ISON/Terskol observatory. We obtained several unfiltered images starting on August 24 (UT) 23:58:36. We detected optical source in coordinates (J2000) 05:20:21.18 +40:01:43.5 with uncertainty of 1 arcsec in both coordinates. This is 2.6 arcsec apart of the center of the enhanced XRT error circle (Goad et al., GCN 19857). At this time we cannot say nothing about variability of the object. It is not clear whether our source is the same as the source reported by Marshall et al. (GCN 19860). Preliminary photometry of a combined image is following Date UT start t-T0 Filter Exp. OT Err. UL (mid, days) (s) 2016-08-24 23:58:36 0.02758 CR 400 20.6 0.3 20.9 Photometry is based on nearby USNO-B1.0 stars USNO-B1.0_id R2 1300-0122742 18.17 1300-0122665 18.04 1300-0122653 18.66 1300-0122680 17.00 1300-0122864 17.60 1299-0128308 18.00 1300-0122784 17.56 //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19863 SUBJECT: GRB 160824A: 1.5m OSN I-band observation DATE: 16/08/25 19:08:04 GMT FROM: Youdong HU at IAA-CSIC, UGR Y. Hu, A. Sota and A.J. Castro-Tirado (IAA-CSIC Granada), on behalf of a larger collaboration, report: Following the detection of GRB 160824A by Swift (Evans et al. GCNC 19855), optical images in the I-band were obtained at the 1.5m OSN telescope in Granada (Spain) starting at 01:25 (Aug 25), i.e. 2.05 h postburst. No optical afterglow is detected in the co-added image (13 x 300s, mid time 02:00 UT, 2.6 h after the trigger) within the enhanced Swift/XRT error box (Goad et al. GCNC 19857) down to I = 20.0. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 19899 SUBJECT: GRB 160824A: 15 GHz upper limits from AMI DATE: 16/09/06 15:26:44 GMT FROM: Kunal Mooley at Oxford U K. P. Mooley, T. D. Staley, R. P. Fender (Oxford), G. E. Anderson (Curtin), T. Cantwell (Manchester), D. Titterington, S. H. Carey, J. Hickish, Y. C. Perrott, N. Razavi-Ghods, C. Rumsey, P. Scott (Cambridge), K. Grainge, A. Scaife (Manchester) The AMI Large Array robotically triggered on the Swift alert for GRB 160824A (Evans et al., GCN 19855) as part of the 4pisky program, and subsequent follow up observations were obtained up to 10 days post-burst. Our observations at 15 GHz on 2016 Aug 25.11, Aug 26.27, Aug 28.29, and Sep 01.29 (UT) do not reveal any radio source at the XRT location (Goad et al., GCN 19857), with 3sigma upper limits of 444 uJy, 126 uJy, 117 uJy, and 117 uJy respectively. We thank the AMI staff for scheduling these observations. The AMI-GRB database is a log of all GRB follow up observations with the AMI, and is available at http://4pisky.org/ami-grb/.