//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25427 SUBJECT: GRB 190821A: Swift detection of a burst DATE: 19/08/21 17:31:00 GMT FROM: Amy Lien at GSFC A. D'Ai (INAF-IASFPA), E. Ambrosi (INAF-IASFPA), V. D'Elia (SSDC), J.D. Gropp (PSU), J. A. Kennea (PSU), N. J. Klingler (PSU), H. A. Krimm (NSF), S. J. LaPorte (PSU), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), M. J. Moss (GWU), K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (PSU), K. K. Simpson (PSU) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 17:10:03 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 190821A (trigger=921722). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 250.077, -34.022 which is RA(J2000) = 16h 40m 18s Dec(J2000) = -34d 01' 16" 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 100 sec. The peak count rate was ~2200 counts/sec (15-350 keV), at ~30 sec after the trigger. The XRT began observing the field at 17:11:21.8 UT, 78.0 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 250.05464, -34.00719 which is equivalent to: RA(J2000) = 16h 40m 13.11s Dec(J2000) = -34d 00' 25.9" with an uncertainty of 3.6 arcseconds (radius, 90% containment). This location is 85 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 (3.35 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 3.2 (+2.68/-2.37) x 10^21 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 2.95e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 88 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. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the sub-image. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. Because of the density of catalogued stars, further analysis is required to report an upper limit for any afterglow in the region. No correction has been made for the expected extinction corresponding to E(B-V) of 0.54. Burst Advocate for this burst is A. D'Ai (antonino.dai AT inaf.it). 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: 25429 SUBJECT: Swift GRB190821.72 Global MASTER-Net observations report DATE: 19/08/21 17:55:19 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), H.Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev, O.Ershova (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University) MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB190821.72 (trigger No 921722, 16h 40m 18.48s , -34d 1m 19.20s, R=0.05) errorbox 8 sec after notice time and 41 sec after trigger time at 2019-08-21 17:10:44 UT, with upper limit up to 18.4 mag. Observations started at twilight. The observations began at zenit distance = 3 deg. The sun altitude is -12.4 deg. The galactic latitude b = -60 deg., longitude l = 98 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1111516 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 46 | MASTER-SAAO | P\ | 10 | 16.3 | 73 | MASTER-SAAO | P\ | 10 | 16.4 | 98 | MASTER-SAAO | P\ | 60 | 17.3 | Coadd 104 | MASTER-SAAO | P\ | 20 | 16.9 | 145 | MASTER-SAAO | P\ | 30 | 17.0 | 195 | MASTER-SAAO | P\ | 40 | 17.3 | 250 | MASTER-SAAO | P\ | 150 | 17.9 | Coadd 256 | MASTER-SAAO | P\ | 50 | 17.4 | 328 | MASTER-SAAO | P\ | 60 | 17.6 | 508 | MASTER-SAAO | P\ | 270 | 18.1 | Coadd 941 | MASTER-SAAO | P\ | 490 | 18.4 | Coadd The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25431 SUBJECT: GRB 190821A: T60 Les Makes optical detection of the afterglow DATE: 19/08/21 18:13:19 GMT FROM: Alain Klotz at IRAP-CNRS-OMP Klotz A., Noysena.K., Atteia J.L. (CNRS-OMP-IRAP), Boer, M., Eymar, L. (CNRS-ARTEMIS), Gendre B. (UWA - Univ. Western Australia) Peyrot, A., Teng J.P., Thierry P. (Les Makes observatory) report: We imaged the field of GRB 190821A detected by SWIFT (trigger 921722) with the T60 tele-operated telescope (D=60cm) located at Les Makes Observatory, Reunion Island, France. The observations started 790s after the GRB trigger. On the first image of 120s (Clear filter) we detect the optical afterglow compatible with the position of XRT (Lien et al. GCNC 25427). start  end    R (sec) (sec) 790   910   18.4 +/- 0.2 Further images are comming. Magnitudes were estimated with the nearby NOMAD1 stars and are not corrected for galactic dust extinction. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25433 SUBJECT: GRB 190821A: MASTER do not see any afterglow candidate DATE: 19/08/21 19:01:27 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, F.Balakin, E. Gorbovskoy, V. Kornilov, N.Tyurina, P.Balanutsa,A.Kuznetsov, F.Balakin, V. Vladimirov, D. Vlasenko, I. Gorbunov,D.Zimnukhov, V.Senik, A.Chasovnikov, A.Pozdnyakov, A.Chasovnikov, V.Topolev, D.Kuvshinov(Lomonosov Moscow State University, SAI, Physics Department), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias IAC), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), H. Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE), D. Buckley (South African Astronomical Observatory SAAO), O. Gress, N.M. Budnev, O.Ershova (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University) There is known star at Swift XRT position (GCN 25427, GCN 25431). Its brightnes not changes during 1 hour, after 41 sec after trigger in MASTER images (GCN 25429). This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25435 SUBJECT: GRB 190821A: Fermi GBM observation DATE: 19/08/21 21:38:14 GMT FROM: Bagrat Mailyan at UAH B. Mailyan, S. Lesage and C. Meegan (all UAH) report on behalf of the Fermi GBM Team: "At 17:10:34.08 UT on 21 August 2019, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 190821A (trigger 588100239/ 190821716), which was also detected by the Swift/BAT (D'Ai et al. 2019, GCN 25427). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 85 degrees. The GBM lightcurve shows an initial bright pulse followed by longer duration emission containing multiple peaks. with a duration (T90) of about 60 s (50-300 keV). The time-averaged spectrum from T0-4 s to T0+34 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.7 +/- 0.15 and the cutoff energy, parameterized as Epeak, is 29 +/- 6 keV. The event fluence (10-1000 keV) in this time interval is (2.54 +/- 0.17)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T-0.128 s in the 10-1000 keV band is 4.9 +/- 0.25 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: 25436 SUBJECT: GRB 190821A: Enhanced Swift-XRT position DATE: 19/08/21 22:38:34 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 1074 s of XRT Photon Counting mode data and 3 UVOT images for GRB 190821A, 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 = 250.05481, -34.00711 which is equivalent to: RA (J2000): 16h 40m 13.15s Dec (J2000): -34d 00' 25.6" 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: 25444 SUBJECT: GRB 190821A: Swift-XRT refined Analysis DATE: 19/08/22 07:29:53 GMT FROM: Phil Evans at U of Leicester J. D. Gropp (PSU), A. Tohuvavohu (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB) and A. D'Ai report on behalf of the Swift-XRT team: We have analysed 6.7 ks of XRT data for GRB 190821A (D'Ai et al. GCN Circ. 25427), from 84 s to 33.9 ks after the BAT trigger. The data comprise 290 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 25436). The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=7.82 (+0.18, -0.87). At T+140 s the decay flattens to an alpha of -0.4 (+/-0.5) before breaking again at T+1047 s to a final decay with index alpha=1.06 (+0.17, -0.16). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.75 (+0.18, -0.11). The best-fitting absorption column is consistent with the Galactic value of 3.3 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.4 x 10^-11 (5.9 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.3 (+/-1.0) x 10^21 cm^-2 Galactic foreground: 3.3 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 1.75 (+0.18, -0.11) If the light curve continues to decay with a power-law decay index of 1.06, the count rate at T+24 hours will be 0.015 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.8 x 10^-13 (9.0 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00921722. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25448 SUBJECT: GRB 190821A: MASTER VWFC syncronous optical observations DATE: 19/08/22 14:09:26 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs F.Balakin, V. Lipunov, E. Gorbovskoy, V. Kornilov, N.Tyurina, P.Balanutsa,A.Kuznetsov, F.Balakin, V. Vladimirov, D. Vlasenko, I. Gorbunov,D.Zimnukhov, V.Senik, A.Chasovnikov, A.Pozdnyakov, A.Chasovnikov, V.Topolev, D.Kuvshinov(Lomonosov Moscow State University, SAI, Physics Department), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias IAC), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), H. Levato (Instituto de Ciencias Astronomicas, de la Tierra y del Espacio ICATE), D. Buckley (South African Astronomical Observatory SAAO), O. Gress, N.M. Budnev, O.Ershova (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University) MASTER-SAAO very wide field cameras (d=82 mm, FOV = 2x384 sq. degree) syncronously observed GRB190821A (D'Ai et al. GCN 25427) position before, during and after trigger time. We do not see OT at Swift XRT (Gropp et al. GCN 25444) position up to 12 mag. The syncronous observation movie is avalable here: http://master.sai.msu.ru/static/MASTER_SAAO_GRB190822A.gif MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB190821A errorbox 8 sec after notice time and 41 sec after trigger time at 2019-08-21 17:10:44 UT, with upper limit up to 18.4 mag (Lipunov et al. GCN 25429; GCN 25433). Observations started at twilight. We alse do not see OT at Swift XRT. The observations began at zenit distance = 3 deg. The sun altitude is -12.4 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1111516 This message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25450 SUBJECT: GRB 190821A: Swift/UVOT Upper Limits DATE: 19/08/22 17:58:31 GMT FROM: Kira Simpson at PSU GRB 190821A: Swift/UVOT Upper Limits K. K. Simpson (PSU) and A. D'Ai (INAF-IASFPA) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 190821A 89 s after the BAT trigger (D'Ai et al., GCN Circ. 25427). No optical afterglow consistent with the XRT position (Goad et al. GCN Circ. 25436) 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 89 239 147 >19.1 white 89 5595 344 >19.5 v 5806 6006 197 >18.3 b 5191 5390 197 >19.9 u 303 11409 336 >19.6 w1 9373 9551 175 >18.9 m2 6011 6164 151 >19.7 w2 5602 5801 197 >20.2 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.53 in the direction of the burst (Schlegel et al. 1998). //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 25464 SUBJECT: GRB 190821A: Swift-BAT refined analysis DATE: 19/08/24 15:57:08 GMT FROM: Amy Lien at GSFC S. D. Barthelmy (GSFC), J. R. Cummings (CPI), A. D'Ai (INAF-IASFPA), H. A. Krimm (NSF), 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): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 190821A (trigger #921722) (D'Ai et al., GCN Circ. 25427). The BAT ground-calculated position is RA, Dec = 250.070, -34.027 deg which is RA(J2000) = 16h 40m 16.9s Dec(J2000) = -34d 01' 35.5" with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 83%. The mask-weighted light curve shows a multi-peaked structure that starts at ~T-3 s and ends at ~T+60 s. The highest peak occurs at ~T+30 s. T90 (15-350 keV) is 57.1 +- 2.6 sec (estimated error including systematics). The time-averaged spectrum from T-3.3 to T+59.5 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.03 +- 0.10. The fluence in the 15-150 keV band is 2.4 +- 0.1 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+29.98 sec in the 15-150 keV band is 2.8 +- 0.3 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/921722/BA/