//////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30485 SUBJECT: GRB 210723A: Swift detection of a burst DATE: 21/07/23 15:04:47 GMT FROM: David Palmer at LANL T. Sbarrato (INAF-OAB), M. G. Bernardini (INAF-OAB), P. D'Avanzo (INAF-OAB), J. A. Kennea (PSU), N. J. Klingler (GSFC/UMBC/CRESSTII), N. P. M. Kuin (UCL-MSSL), S. Laha (GSFC/UMBC/CRESST), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), D. M. Palmer (LANL), M. H. Siegel (PSU) and A. Tohuvavohu (U Toronto) report on behalf of the Neil Gehrels Swift Observatory Team: At 14:46:10 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 210723A (trigger=1061284). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 121.726, -32.889 which is RA(J2000) = 08h 06m 54s Dec(J2000) = -32d 53' 20" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 50 sec. The peak count rate was ~2200 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 14:47:40.4 UT, 89.6 seconds after the BAT trigger. Using promptly downlinked data we find a bright, fading, uncatalogued X-ray source located at RA, Dec 121.72157, -32.88624 which is equivalent to: RA(J2000) = 08h 06m 53.18s Dec(J2000) = -32d 53' 10.5" with an uncertainty of 7.0 arcseconds (radius, 90% containment). This position may be improved as more data are received; the latest position is available at https://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 7.70 x 10^21 cm^-2 (Willingale et al. 2013). The initial flux in the 2.5 s image was 3.04e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 99 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 large, but uncertain, extinction expected. Although the data from this burst are consistent with a classical long GRB, we note that this source is close to the Galactic plane (lat = -0.34 degrees) which raises the possibility that this is a Galactic transient. If further analysis determines that to be the case, we would name the object Swift J0806.9-3253 . Burst Advocate for this burst is T. Sbarrato (tullia.sbarrato 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: 30486 SUBJECT: GRB 210723A: Prompt enhanced Swift-XRT position DATE: 21/07/23 15:23:33 GMT FROM: Phil Evans at U of Leicester P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Using promptly downlinked XRT event data for GRB 210723A, we find an enhanced XRT position of the afterglow: RA, Dec: 121.7213, -32.8851 which is equivalent to: RA (J2000) = 08 06 53.12 Dec (J2000) = -32 53 06.4 with an uncertainty of 1.9 arcseconds (radius, 90% confidence). Analysis of the promptly available data is online at http://www.swift.ac.uk/sper/1061284. Position enhancement is is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30491 SUBJECT: Swift GRB 210723A: Global MASTER-Net observations report DATE: 21/07/23 23:16:55 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, D. Cheryasov (Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), 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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB 210723A ( T. Sbarrato et al., GCN 30485) errorbox 29771 sec after notice time and 29801 sec after trigger time at 2021-07-23 23:02:52 UT, with upper limit up to 15.3 mag. Observations started at twilight. The observations began at zenith distance = 80 deg. The sun altitude is -14.6 deg. The galactic latitude b = -0 deg., longitude l = 251 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1668344 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 29891 | MASTER-OAFA | C | 180 | 15.3 | 30091 | MASTER-OAFA | C | 180 | 14.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30493 SUBJECT: GRB 210723A: Swift-XRT refined Analysis DATE: 21/07/24 11:06:33 GMT FROM: Phil Evans at U of Leicester A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), J.P. Osborne (U. Leicester) and T. Sbarrato report on behalf of the Swift-XRT team: We have analysed 6.3 ks of XRT data for GRB 210723A (Sbarrato et al. GCN Circ. 30485), from 79 s to 57.3 ks after the BAT trigger. The data comprise 267 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. Using 3236 s of PC mode data and 6 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 121.72115, -32.88570 which is equivalent to: RA (J2000): 08h 06m 53.08s Dec(J2000): -32d 53' 08.5" with an uncertainty of 2.0 arcsec (radius, 90% confidence). The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=2.45 (+/-0.15). At T+154 s the decay flattens to an alpha of 1.67 (+/-0.09) before breaking again at T+959 s to a final decay with index alpha=1.04 (+0.09, -0.23). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.75 (+0.11, -0.10). The best-fitting absorption column is 1.26 (+0.14, -0.13) x 10^22 cm^-2, in excess of the Galactic value of 7.7 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.71 (+0.26, -0.25) and a best-fitting absorption column of 1.6 (+0.4, -0.3) x 10^22 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 6.5 x 10^-11 (1.1 x 10^-10) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.6 (+0.4, -0.3) x 10^22 cm^-2 Galactic foreground: 7.7 x 10^21 cm^-2 Excess significance: 4.1 sigma Photon index: 1.71 (+0.26, -0.25) If the light curve continues to decay with a power-law decay index of 1.04, the count rate at T+24 hours will be 7.0 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.6 x 10^-13 (7.7 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/01061284. This circular is an official product of the Swift-XRT team. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30495 SUBJECT: GRB 210723A: Swift-BAT refined analysis DATE: 21/07/24 20:28:49 GMT FROM: Amy Lien at GSFC H. A. Krimm (NSF), S. D. Barthelmy (GSFC), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), T. Sbarrato (INAF-OAB), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team): Using the data set from T-239 to T+861 sec from the recent telemetry downlink, we report further analysis of BAT GRB 210723A (trigger #1061284) (Sbarrato et al., GCN Circ. 30485). The BAT ground-calculated position is RA, Dec = 121.723, -32.893 deg which is RA(J2000) = 08h 06m 53.4s Dec(J2000) = -32d 53' 35.8" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 77%. The mask-weighted light curve shows a single-pulse structure that starts at ~T-5 s, peaks at ~T0, and ends at ~T+65 s. T90 (15-350 keV) is 48.54 +- 3.50 sec (estimated error including systematics). The time-averaged spectrum from T-4.59 to T+66.64 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 0.85 +- 0.29, and Epeak of 88.2 +- 15.3 keV (chi squared 54.48 for 52 d.o.f.). For this model the total fluence in the 15-150 keV band is 5.3 +- 0.2 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+2.68 sec in the 15-150 keV band is 3.1 +- 0.3 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.60 +- 0.06 (chi squared 75.55 for 53 d.o.f.). 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/1061284/BA/ //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30499 SUBJECT: GRB 210723A: Fermi GBM Observation DATE: 21/07/25 01:23:27 GMT FROM: Suraj Poolakkil at UAH S. Lesage (UAH), B. Hristov (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: At 14:46:07 UT on 23 July 2021, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 210723A (trigger 648744372/210723615). which was also detected by Swift BAT (T. Sbarrato et al. 2021, GCN 30485) The Fermi GBM on-ground location is consistent with the Swift BAT position. The angle from the Fermi LAT boresight is 94 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 43 s (10-1000 keV). The time-averaged spectrum from T0+1.5 to T0+36.4 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.67 +/- 0.07 and the cutoff energy, parameterized as Epeak, is 113 +/- 5 keV. The event fluence (10-1000 keV) in this time interval is (7.6 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+1 s in the 10-1000 keV band is 4.7 +/- 0.3 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: 30506 SUBJECT: GRB 210723A: CALET Gamma-Ray Burst Monitor detection DATE: 21/07/25 10:03:08 GMT FROM: Valentin Pal'shin at AGU Y. Asaoka (ICRR), A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU), Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The long GRB 210723A (Swift detection: Sbarrato et al., GCN Circ. 30485, Krimm and Barthelmy, GCN Circ. 30495; Fermi GBM Observation: Lesage et al., GCN Circ. 30499; https://gcn.gsfc.nasa.gov/other/210723A.gcn3) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 14:46:05.572 UTC on 23 July 2021 (http://cgbm.calet.jp/cgbm_trigger/flight/1311086521/index.html). The burst signal was seen only by the SGM detector. The burst light curve shows a single-pulse structure which starts at T+0.9 sec, peaks at T+12.6 sec,and ends at T+22.0 sec. The T90 and T50 durations measured by the SGM data are 17.2 +- 3.2 sec and 10.6 +- 3.2 sec (40-1000 keV), respectively. The ground processed light curve is available at http://cgbm.calet.jp/cgbm_trigger/ground/1311086521/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at the Waseda University. //////////////////////////////////////////////////////////////////////// TITLE: GCN CIRCULAR NUMBER: 30528 SUBJECT: GRB 210723A: Swift/UVOT Upper Limits DATE: 21/07/27 06:16:48 GMT FROM: Sam LaPorte at PSU GRB 210723A: Swift/UVOT Upper Limits S. J. LaPorte (PSU) and Sbarrato (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 210723A 99 s after the BAT trigger (Sbarrato et al., GCN Circ. 30485). No optical afterglow consistent with the XRT position (Evans GCN Circ. 30486) 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 99 249 147 >20.6 u_FC 312 562 246 >19.2 white 99 1364 369 >20.6 v 641 1241 78 >18.2 b 567 1339 78 >19.3 u 312 1315 304 >19.4 w1 691 1290 58 >19.0 m2 666 1266 78 >18.8 w2 617 1217 78 >19.5 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.962 in the direction of the burst (Schlegel et al. 1998).