//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25516 SUBJECT: GRB 190828B: Fermi GBM Final Real-time Localization DATE: 19/08/28 13:10:04 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM The Fermi GBM team reports the detection of a likely LONG GRB At 12:59:59 UT on 28 Aug 2019, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 190828B (trigger 588690004.456526 / 190828542). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 246.6, Dec = 24.6 (J2000 degrees, equivalent to J2000 16h 26m, 24d 36'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 17.0 degrees. The skymap can be found here: http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2019/bn190828542/quicklook/glg_skymap_all_bn190828542.png The HEALPix FITS file, including the estimated localization systematic, can be found here: http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2019/bn190828542/quicklook/glg_healpix_all_bn190828542.fit The GBM light curve can be found here: http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2019/bn190828542/quicklook/glg_lc_medres34_bn190828542.gif //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25517 SUBJECT: GRB 190828B: Swift detection of a burst DATE: 19/08/28 13:15:52 GMT FROM: Scott Barthelmy at NASA/GSFC S. Dichiara (NASA/GSFC/UMCP), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), M. G. Bernardini (INAF-OAB), A. A. Breeveld (UCL-MSSL), D. N. Burrows (PSU), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), P. A. Evans (U Leicester), J.D. Gropp (PSU), J. A. Kennea (PSU), N. J. Klingler (PSU), F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), K. L. Page (U Leicester), B. Sbarufatti (PSU), M. H. Siegel (PSU) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 12:59:59.42 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 190828B (trigger=922808). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 251.818, 27.237 which is RA(J2000) = 16h 47m 16s Dec(J2000) = +27d 14' 12" 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 ~3000 counts/sec (15-350 keV), at ~10 sec after the trigger. The XRT began observing the field at 13:00:54.1 UT, 54.7 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source with an enhanced position: RA, Dec 251.8317, 27.2808 which is equivalent to: RA(J2000) = 16h 47m 19.60s Dec(J2000) = +27d 16' 50.9" with an uncertainty of 2.2 arcseconds (radius, 90% containment). This location is 163 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 consistent with the Galactic value of 6.84 x 10^20 cm^-2 (Willingale et al. 2013). The initial flux in the 2.5 s image was 2.12e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 63 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 expected extinction corresponding to E(B-V) of 0.10. Burst Advocate for this burst is S. Dichiara (dichiara AT umd.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/) //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25521 SUBJECT: GRB 190828B: Enhanced Swift-XRT position DATE: 19/08/28 16:08:02 GMT FROM: Phil Evans at U of Leicester A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 1594 s of XRT Photon Counting mode data and 2 UVOT images for GRB 190828B, 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 = 251.83127, +27.28091 which is equivalent to: RA (J2000): 16h 47m 19.51s Dec (J2000): +27d 16' 51.3" with an uncertainty of 1.7 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: 25524 SUBJECT: GRB 190828B: Dabancheng-0.5m optical upper limit DATE: 19/08/28 16:31:06 GMT FROM: Dong Xu at NAOC/CAS B.Y. Yu, X. Liu, D. Xu, Z.P. Zhu (NAOC), J.H. Liu (XAO), X. Gao (Urumqi No.1 Senior High School), Z.B. Zhang (XJTS) report: We observed the field of GRB 190828B (Dichiara et al., GCN 25517) using the Half-Meter Telescope (HMT-0.5m) located at Dabancheng, Xinjiang, China. We obtained 5x60 s unfiltered frames, started at 13:56:32 UT on 2019-08-28, i.e., 56.5 min after the burst. No optical source is detected at the XRT position (Dichiara et al., GCN25517) in our stacked image, down to a limiting magnitude of R~17.8, calibrated with the nearby SDSS field. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25534 SUBJECT: GRB 190828B: Swift-BAT refined analysis DATE: 19/08/28 23:33:26 GMT FROM: Amy Lien at GSFC H. A. Krimm (NSF), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), S. Dichiara (NASA/GSFC/UMCP), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): (i.e. the Swift-BAT team): Using the data set from T-239 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 190828B (trigger #922808) (Dichiara et al., GCN Circ. 25517). The BAT ground-calculated position is RA, Dec = 251.838, 27.287 deg which is RA(J2000) = 16h 47m 21.2s Dec(J2000) = +27d 17' 12.9" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%. The mask-weighted light curve shows a multi-peak structure that starts at ~T-40 s and ends at ~T+50 s. There are roughly three main peaks that occurs at ~T0, ~T+11 s, and ~T+31 s, respectively. T90 (15-350 keV) is 66.6 +- 6.2 sec (estimated error including systematics). The time-averaged spectrum from T-42.4 to T+53.3 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.29 +- 0.07. The fluence in the 15-150 keV band is 4.2 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+10.74 sec in the 15-150 keV band is 2.3 +- 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/922808/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25535 SUBJECT: GRB 190828B: Fermi GBM observation DATE: 19/08/29 03:23:48 GMT FROM: Oliver J Roberts at USRA/NASA O.J. Roberts (USRA/MSFC), E. Bissaldi (INFN Bari) and C. Meegan (UAH) report on behalf of the Fermi GBM Team: "At 12:59:59.46 UT on 28 August 2019, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 190828B (trigger 588690004 / 190828542), which was also detected by Swift (Dichiara et al. 2019, GCN 25517 ) The Fermi GBM Final Real-time Localization (GCN 25516) is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 18 degrees. The GBM light curve consists of multiple, bright peaks with a duration (T90) of about 55 s (50-300 keV). The time-averaged spectrum from T0-34 s to T0+46 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.99 +/- 0.06 and the cutoff energy, parameterized as Epeak, is 237 +/- 22 keV The event fluence (10-1000 keV) in this time interval is (1.24 +/- 0.06)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+10.6 s in the 10-1000 keV band is 3.9 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25544 SUBJECT: GRB 190828B: Swift/UVOT Upper Limits DATE: 19/08/29 13:01:37 GMT FROM: Samantha Oates at MSSL S. R. Oates (U.Warwick) and S. Dichiara (NASA/GSFC/UMCP) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 190828B 63 s after the BAT trigger (Dichiara et al., GCN Circ. 25517). No optical afterglow consistent with the XRT position (Beardmore et al. GCN Circ. 25521) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 63 213 147 >20.8 u_FC 275 525 246 >20.1 white 63 1717 411 >21.4 v 605 1767 136 >19.1 b 530 1693 117 >20.0 u 275 1668 363 >20.4 w1 654 1644 117 >19.2 m2 630 5626 259 >19.4 w2 580 1743 136 >19.3 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.10 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25546 SUBJECT: GRB 190828B: Swift-XRT refined Analysis DATE: 19/08/29 13:16:02 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M. Perri (ASDC), B. Sbarufatti (PSU), D.N. Burrows (PSU), J. D. Gropp (PSU) and S. Dichiara report on behalf of the Swift-XRT team: We have analysed 5.8 ks of XRT data for GRB 190828B (Dichiara et al. GCN Circ. 25517), from 60 s to 74.7 ks after the BAT trigger. The data comprise 90 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN Circ. 25521). The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=2.4 (+/-0.4). At T+98.4 s the decay flattens to an alpha of -1.5 (+0.0, -1.4). The light curve breaks again at T+110 s to a decay with alpha=3.5 (+0.7, -0.4), and again at T+217 s s to alpha=-0.24 (+0.16, -0.20), before a final break at T+1028 s s after which the decay index is 0.96 (+/-0.04). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.56 (+0.11, -0.09). The best-fitting absorption column is 7.8 (+3.8, -1.0) x 10^20 cm^-2, consistent with the Galactic value of 6.8 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.91 (+/-0.10) and a best-fitting absorption column of 1.25 (+0.29, -0.27) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.6 x 10^-11 (4.4 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.25 (+0.29, -0.27) x 10^21 cm^-2 Galactic foreground: 6.8 x 10^20 cm^-2 Excess significance: 3.4 sigma Photon index: 1.91 (+/-0.10) If the light curve continues to decay with a power-law decay index of 0.96, the count rate at T+24 hours will be 0.035 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.3 x 10^-12 (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/00922808. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25548 SUBJECT: GRB 190828B: optical upper limit from 0.5m Savelli Robotic Telescope DATE: 19/08/29 14:35:27 GMT FROM: Andrea Melandri at INAF-OAB A. Brosio (Oss. Astr. Savelli), A. Melandri (INAF-OAB), E. Palazzi (INAF-OAS), L. Nicastro (INAF-OAS), M.A. Tripodi (Oss. Astr. Savelli), S. Savaglio (UniCal) on behalf of a larger collaboration report: We observed the field of GRB 190828B (Dichiara et al., GCN 25517) with the 0.5m Savelli Robotic Telescope (SRT) located at the Osservatorio Astronomico Lilio (Savelli, Italy). The observations were performed starting on 2019 August 28 at 19:19:22 UT (i.e. about 6.3 hours after the burst) and consisted of 24x300s exposures in the r-sdss band. No optical counterpart is detected nearby the XRT enhanced position (Beardmore et al., GCN 25521) in our stacked image, down to a 5sigma limiting magnitude of r>20.5, at a mean time of about 7.48 hours after the GRB. Calibration was performed against the SDSS catalog. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25550 SUBJECT: GRB 190828B: VLT/X-shooter optical afterglow candidate DATE: 19/08/29 16:58:17 GMT FROM: Kasper Elm Heintz at Univ. of Iceland and DAWN/NBI J. P. U. Fynbo (DAWN/NBI), K. E. Heintz (Univ. of Iceland), D. B. Malesani (DTU space), and D. A. Perley (LJMU), report on behalf of the Stargate collaboration: We imaged the field of the Swift (Dichiara et al., GCN 25517) and Fermi-GBM (Roberts et al., GCN 25536) detected GRB 190828B with the ESO-VLT/X-shooter acquisition camera between 00:03:44 and 00:22:49 UT on August 29 (i.e. 11.15 hr after the trigger). From the combined images, obtained with a total integration time of 210 sec, we identify a faint source within the XRT error circle with magnitude r = 23.55 +/- 0.15 AB mag, calibrated from the photometry of nearby field stars as listed in the Pan-STARRS archival data. To verify whether this source is the afterglow or host galaxy of the GRB, a second epoch of images is required. We acknowledge the ESO observing staff at Paranal, especially Alain Smette, Camila Navarrete and Linda Schmidtobreick. [GCN OPS NOTE(31aug19): Per author's request, the "Title:" string was removed from the SUBJECT: line.] //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25771 SUBJECT: GRB 190828B: AstroSat CZTI detection DATE: 19/09/17 09:06:06 GMT FROM: Ramkrishna Gaikwad at IUCAA/AstroSat R. Gaikwad, V. Sharma, D. Bhattacharya and A. Vibhute (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data showed the detection of a GRB 190828B, which was also detected by Fermi GBM Final Real-time Localization (GCN #25516), Swift (S. Dichiara. et al., GCN # 25517), Swift-XRT (Beardmore A. et al., GCN # 25521), Swift-BAT (Krimm H. et al., GCN # 25534), Fermi GBM (Roberts J. et al., GCN # 25535),. The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple pulses of emission with the strongest peak at 2019-08-28 12:59:59.0 UT. The measured peak count rate associated with the burst is 297 cts/s above the background in the combined data of four quadrants, with a total of 3424 cts. The local mean background count rate was 611 cts/s. Using cumulative rates, we measure a T90 of 31.9 s. It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.