GRB181020A

This page lists all entries on GRB181020A in GRBweb

Summary Fermi GBM IPN Swift GCN 23349 GCN 23350 GCN 23351 GCN 23352 GCN 23353 GCN 23356 GCN 23357 GCN 23358 GCN 23359 GCN 23360 GCN 23362 GCN 23363 GCN 23436

Summary table
Variable Value Source
GRB_name_Fermi GRB181020792
T0 19:00:33 UTC GCN_circulars,Swift Det
ra 13.9824° Swift
decl -47.3811° Swift
pos_error 5.82e-05° Swift
T90 15.104 s Fermi_GBM
T90_error 0.572 s Fermi_GBM
T90_start 19:00:33.809 UTC Fermi_GBM
fluence 2.81e-05 erg/cm² Fermi_GBM
fluence_error 3.44e-08 erg/cm² Fermi_GBM
redshift 2.9380
T100 238.0 s
GBM_located False
mjd 58411.79204861111 GCN_circulars,Swift Det
Fermi GBM table
GRB_name_Fermi GRB181020792
trigger_name bn181020792
ra 13.9837°
decl -47.3797°
pos_error 2.98e+00°
datum 2018-10-20
t_trigger 19:00:33.297 UTC
T90 15.104 s
T90_error 0.572 s
T90_start 19:00:33.809 UTC
fluence 2.81e-05 erg/cm²
fluence_error 3.44e-08 erg/cm²
flux_1024 1.66e+01 erg/cm²/s
flux_1024_error 2.88e-01 erg/cm²/s
flux_1024_time 7.36e+00 erg/cm²/s
flux_64 1.88e+01 erg/cm²/s
flux_64_error 1.20e+00 erg/cm²/s
IPN table
GRB_name GRB181020A
ra 13.9667°
decl -47.3833°
pos_error 5.00e-02°
redshift 2.9380
Swift table
GRB_name GRB181020A
t_trigger 19:00:33 UTC
ra 13.9824°
decl -47.3811°
pos_error 5.82e-05°
T90 238.0 s
fluence 8.10e-06 erg/cm²
redshift 2.9380
GCN 23349 table
GRB_name GRB181020A
GCN_number 23349
Detection_method Swift Det
t_trigger 19:00:33 UTC
ra 13.9670°
decl -47.3800°
Circular_text TITLE: GCN CIRCULAR NUMBER: 23349 SUBJECT: GRB 181020A: Swift detection of a burst with an optical counterpart DATE: 18/10/20 19:19:43 GMT FROM: David Palmer at LANL M. J. Moss (George Washington University), A. D'Ai (INAF-IASFPA), V. D'Elia (SSDC), J.D. Gropp (PSU), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL), A. Y. Lien (GSFC/UMBC), K. L. Page (U Leicester), D. M. Palmer (LANL) and A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 19:00:33 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 181020A (trigger=867987). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 13.967, -47.380 which is RA(J2000) = 00h 55m 52s Dec(J2000) = -47d 22' 47" 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 30 sec. The peak count rate was ~12000 counts/sec (15-350 keV), at ~7 sec after the trigger. The XRT began observing the field at 19:01:29.0 UT, 55.6 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 13.9837, -47.3796 which is equivalent to: RA(J2000) = 00h 55m 56.09s Dec(J2000) = -47d 22' 46.6" with an uncertainty of 4.8 arcseconds (radius, 90% containment). This location is 40 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. The initial flux in the 2.5 s image was 6.04e-09 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 250 seconds with the U filter starting 121 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 00:55:55.78 = 13.98240 DEC(J2000) = -47:22:51.8 = -47.38105 with a 90%-confidence error radius of about 0.76 arc sec. This position is 6.1 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.51 with a 1-sigma error of about 0.15. No correction has been made for the expected extinction corresponding to E(B-V) of 0.01. Burst Advocate for this burst is M. J. Moss (mikejmoss3 AT gmail.com). 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.)
GCN 23350 table
GRB_name GRB181020A
GCN_number 23350
Detection_method Fermi LAT Det
ra 14.1000°
decl -47.3000°
Circular_text TITLE: GCN CIRCULAR NUMBER: 23350 SUBJECT: GRB 181020A: Fermi-LAT detection DATE: 18/10/21 01:47:35 GMT FROM: Magnus Axelsson at Stockholm U. M. Axelsson (KTH and Stockholm University) reports on behalf of the Fermi-LAT team: On October 20, 2018, Fermi-LAT detected high-energy emission from GRB 181020A, which was also detected by Swift (Moss et al. 2018, GCN 23349) and by Fermi-GBM (trigger 561754838). The best LAT on-ground location is found to be RA, Dec = 14.1, -47.3 (J2000) with an error radius of 1.1 deg (90 % containment, statistical error only). This is 0.19 deg from the Swift location. This was 50 deg from the LAT boresight at the time of the GBM trigger: 19:00:33.30 UT. The data from the Fermi-LAT in the time interval 0-50s after the GBM trigger show a significant increase in the event rate that is spatially and temporally correlated with the trigger with very high significance. The highest-energy photon is a 930 MeV event which is observed 18 seconds after the GBM trigger. The Fermi-LAT point of contact for this burst is Masanori Ohno (ohno@astro.hiroshima-u.ac.jp). The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
GCN 23351 table
GRB_name GRB181020A
GCN_number 23351
Detection_method Swift-XRT Det
ra 13.9825°
decl -47.3803°
Circular_text TITLE: GCN CIRCULAR NUMBER: 23351 SUBJECT: GRB 181020A: Enhanced Swift-XRT position DATE: 18/10/21 03:35:37 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 1995 s of XRT Photon Counting mode data and 3 UVOT images for GRB 181020A, 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 = 13.98251, -47.38033 which is equivalent to: RA (J2000): 00h 55m 55.80s Dec (J2000): -47d 22' 49.2" 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.
GCN 23352 table
GRB_name GRB181020A
GCN_number 23352
Detection_method Fermi GBM Det
t_trigger 19:00:33.300 UTC
Circular_text TITLE: GCN CIRCULAR NUMBER: 23352 SUBJECT: GRB 181020A: Fermi GBM detection DATE: 18/10/21 04:22:04 GMT FROM: Peter Veres at UAH P. Veres (UAH) reports on behalf of the Fermi GBM Team: "At 19:00:33.30 UT on 20 October 2018, the Fermi Gamma-Ray Burst Monitor triggered and located GRB 181020A (trigger 561754838 / 181020792). which was also detected by Fermi/LAT (Axelsson GCN 23350) and Swift/BAT (Moss et al., GCN 23349). The GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight at the GBM trigger time is 50 degrees. The GBM light curve shows a single bright pulse with a duration (T90) of about 15 s (50-300 keV). The time-averaged spectrum from T0-2 s to T0+20.5 s is best fit by a Band function with Epeak = 367 +/- 17 keV, alpha = -0.70 +/- 0.02, and beta = -2.06 +/- 0.07. The event fluence (10-1000 keV) in this time interval is (3.07 +/- 0.04)E-5 erg/cm^2. The 1-sec peak photon flux measured starting from T0+7.4 s in the 10-1000 keV band is 16.6 +/- 0.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog."
GCN 23353 table
GRB_name GRB181020A
GCN_number 23353
Detection_method Swift-XRT Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 23353 SUBJECT: GRB 181020A: Swift-XRT refined Analysis DATE: 18/10/21 04:36:46 GMT FROM: Phil Evans at U of Leicester K.L. Page (U. Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), A. Tohuvavohu (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester) and M.J. Moss report on behalf of the Swift-XRT team: We have analysed 7.3 ks of XRT data for GRB 181020A (Moss et al. GCN Circ. 23349), from 61 s to 18.3 ks after the BAT trigger. The data comprise 1.1 ks 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. 23351). The late-time light curve (from T0+4.8 ks) can be modelled with a power-law decay with a decay index of alpha=1.2 (+/-1.0). A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.865 (+0.020, -0.019). The best-fitting absorption column is 4.3 (+0.5, -0.4) x 10^20 cm^-2, in excess of the Galactic value of 1.6 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.97 (+0.09, -0.08) and a best-fitting absorption column of 5.2 (+1.9, -1.8) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.3 x 10^-11 (3.8 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 5.2 (+1.9, -1.8) x 10^20 cm^-2 Galactic foreground: 1.6 x 10^20 cm^-2 Excess significance: 3.2 sigma Photon index: 1.97 (+0.09, -0.08) If the light curve continues to decay with a power-law decay index of 1.2, the count rate at T+24 hours will be 0.042 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.4 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/00867987. This circular is an official product of the Swift-XRT team.
GCN 23356 table
GRB_name GRB181020A
GCN_number 23356
Detection_method Optical
ra 13.9647°
decl -47.3874°
Circular_text TITLE: GCN CIRCULAR NUMBER: 23356 SUBJECT: GRB 181020A: VLT/X-shooter spectroscopy and redshift DATE: 18/10/21 10:09:02 GMT FROM: Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst Johan P. U. Fynbo (DAWN/NBI and DAWN/DTU), Antonio de Ugarte Postigo (HETH/IAA-CSIC and DARK/NBI), Valerio D'Elia (ASI-SSDC), Nial R. Tanvir (Univ. Leicester), Giovanna Pugliese (API/Univ. Amsterdam), D. Alexander Kann (HETH/IAA-CSIC), D. Malesani (DAWN/NBI, DAWN/DTU, and DARK/NBI), and Kasper E. Heintz (Univ. Iceland), report on behalf of the Stargate collaboration: We observed the optical afterglow of the bright Swift and Fermi GRB 181020A (Moss et al., GCN 23349; Axelsson, GCN 23350; Veres, GCN 23352) with the ESO VLT UT2 equipped with the X-shooter instrument. Spectroscopy covering the wavelength range 3000-21000 AA was carried out starting on 2018 Oct 21.030 UT (5.7 hr after the GRB), for a total of 4x600 s exposure time. In a 5-s image taken with the acquisition camera on 2018 Oct 10.023 UT, we measure for the afterglow R ~ 17.3 (Vega), assuming R = 18.34 for the USNO star at RA = 00:55:51.53, Dec = -47:23:14.5. The spectrum has a very high S/N. A wide trough is easily visible around 4780 AA, which we interpret as a DLA in the GRB host system. From detection of a plethora of absorption lines, including Al II, Al III, S II, O I, Si II, Si IV, C IV, Zn II, Cr II, Ni II, Fe II, Mn II, O I*, Si II*, Ni II*, Fe II*, we measure the redshift to be z = 2.938. The velocity structure of the lines spans the redshift range 2.9360-2.9407 (2.938 corresponding to the strongest component). The detection of fine-structure lines makes the redshift association with the GRB host system secure. Intervening absorbers are also detected at z = 1.788 (Mg II), 2.172 (Mg II), and 2.822 (C IV). We acknowledge the ESO observing staff in Paranal for conducting these observations, in particular Elizabeth Bartlett, Stephane Brillant, Marcelo Lopez, and Thomas Rivinius.
GCN 23357 table
GRB_name GRB181020A
GCN_number 23357
Detection_method Swift-BAT Det
ra 13.9870°
decl -47.3720°
Circular_text TITLE: GCN CIRCULAR NUMBER: 23357 SUBJECT: GRB 181020A: Swift-BAT refined analysis DATE: 18/10/21 14:50:33 GMT FROM: Amy Lien at GSFC T. Sakamoto (AGU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC), M. J. Moss (GWU), 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 181020A (trigger #867987) (Moss et al., GCN Circ. 23349). The BAT ground-calculated position is RA, Dec = 13.987, -47.372 deg which is RA(J2000) = 00h 55m 56.9s Dec(J2000) = -47d 22' 18.1" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 94%. The mask-weighted light curve shows a large pulse that starts at ~T-1 s, peaks at ~T+8 s and ends at ~T+30 s. There is a second, much weaker, pulse that occurs at ~T+200 s and lasts until ~T+270 s. T90 (15-350 keV) is 238.0 +- 11.6 sec (estimated error including systematics). The time-averaged spectrum from T-1.45 to T+271.20 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.25 +- 0.06. The fluence in the 15-150 keV band is 8.1 +- 0.3 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+7.26 sec in the 15-150 keV band is 7.7 +- 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/867987/BA/
GCN 23358 table
GRB_name GRB181020A
GCN_number 23358
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 23358 SUBJECT: GRB 181020A: LCO Cerro Tololo observations DATE: 18/10/21 15:54:44 GMT FROM: Cristiano Guidorzi at Ferrara U,Italy A. Cucchiara (U. Virgin Islands), C. Guidorzi, R. Martone (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (U. Bath), A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU), D. Morris (U. of Virgin Islands) on behalf of a large collaboration report: We observed Swift GRB 181020A (Moss et al. GCN 23349) with one of the LCO 1-m unit at Cerro Tololo Observatory on October 20, from 23:55 to Oct 21, 00:49 UT (corresponding to 4.9 to 5.8 hours from the GRB trigger time) with the SDSS r' and i' filters. We clearly detect the optical afterglow (Moss et al. GCN 23349) in both filters with the following magnitudes for the first half of the observation run: Mid time from GRB Exposure Filter Magnitude trigger time (hrs) (s) --------------------------------------------------------------------- 5.0 5x120 SDSS r' 17.55 +- 0.03 5.2 5x120 SDSS i' 17.2 +- 0.1 --------------------------------------------------------------------- as calibrated against nearby USNO UCAC4 objects.
GCN 23359 table
GRB_name GRB181020A
GCN_number 23359
Detection_method Fermi LAT Other
Circular_text TITLE: GCN CIRCULAR NUMBER: 23359 SUBJECT: GRB 181020A: Global MASTER Net OT observations DATE: 18/10/21 18:05:37 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, E. Gorbovskoy, V.Kornilov, D.Kuvshinov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.V.Chazov, D. Vlasenko Lomonosov Moscow State University, Sternberg Astronomical Institute, Moscow State University D. Buckley, S. Potter, A. Kniazev, M. Kotze South African Astronomical Observatory A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov Kislovodsk Solar Station of the Pulkovo Observatory K. Ivanov, O. Gres, N.M. Budnev, S. Yazev, O. Chuvalaev, V. Poleshchuk Irkutsk State University V. Yurkov, A. Gabovich, Yu. Sergienko Blagoveschensk Educational State University, Blagoveschensk R. Podesta, Carlos Lopez and F. Podesta Observatorio Astronomico Felix Aguilar (OAFA) Hugo Levato and Carlos Saffe Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE) R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres The Instituto de Astrofisica de Canarias MASTER-SAAO robotic telescope (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 starting survey on the SWIFT GRB181020.79 error-box (ra=00 55 55.78 dec=-47 22 52 r=0.05; Moss et all., GCN #23349; Axelsson et al., Fermi LAT, GCN #23350) 7550 sec after notice time and 7572 sec after trigger time at 2018-10-20 21:06:45 UT. The delay connected with weather condition around trigeer time. The 5-sigma upper limit on our first (540s exposure) coadd set is about 19.5 mag We see possible nonmonotonic behaviour OT detected UVOT ( Moss et all., GCN #23349;). More accurate (handmade) reduction will be coming. The automatic OT LC is available at http://observ.pereplet.ru/images/GRB181020A_LC.jpg The galactic latitude b = -70 deg., longitude l = 300 deg. The observations made on zenit distance = 16 deg.The moon (85 % bright part) is 60 deg. above the horizon. The distance between moon and object is 45 degrees. The sun altitude is -43.7 deg. The object can be observed till sunrise at 2018-10-21 03:49:44 This message may be cited.
GCN 23360 table
GRB_name GRB181020A
GCN_number 23360
Detection_method Swift-UVOT Det
ra 13.9824°
decl -47.3811°
redshift 2.9400
Circular_text TITLE: GCN CIRCULAR NUMBER: 23360 SUBJECT: GRB 181020A: Swift/UVOT Detection DATE: 18/10/21 18:39:11 GMT FROM: Jeffrey Gropp at PSU J. D. Gropp (PSU), M. De Pasquale (U. Instanbul) and Moss (George Washington University) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 181020A 122 s after the BAT trigger (Moss et al., GCN Circ. 23349). A fading source consistent with the XRT enhanced position (Goad et al. GCN Circ. 23351) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 00:55:55.77 = 13.98239 (deg.) Dec (J2000) = -47:22:51.9 = -47.38108 (deg.) with an estimated uncertainty of 0.45 arc sec. (radius, 90% confidence). This optical afterglow is also reported by VLT/X-shooter, Fynbo et al., GCN Circ. 23356; LCO Cerro Tololo, Cucchiara et al., GCN Circ. 23358; and its position is consistent with the Fermi LAT Measurement reported in, Axelsson et al., GCN Circ. 23350; Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag b 352 1027 97 17.18+-0.07 m2 427 745 58 >18.06 u_fc 96 6797 768 18.52+-0.09 u 96 346 245 17.60+-0.08 v 21 720 67 14.89+-0.04 w1 452 769 58 >18.20 w2 379 1053 97 >18.56 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.01 in the direction of the burst (Schlegel et al. 1998). We note that the non-detection in the UV filters is expected for a source at the reported redshift z=2.94 (VLT/X-shooter, Fynbo et al., GCN Circ. 23356;), given the Lyman forest absorption by intergalactic hydrogen.
GCN 23362 table
GRB_name GRB181020A
GCN_number 23362
Detection_method Optical
Circular_text TITLE: GCN CIRCULAR NUMBER: 23362 SUBJECT: GRB 181020A: REM detection DATE: 18/10/22 12:16:45 GMT FROM: Andrea Melandri at INAF-OAB A. Melandri, S.Covino, P. D'Avanzo, D. Fugazza (INAF-OAB), on behalf of the REM team, report: We observed the optical counterpart of GRB 181020A (Moss et al. GCN 23349; Axelsson GCN 23350; Veres GCN 23352; Fynbo et al. GCN 23356; Cucchiara et al. GCN 23358; Gropp et al. GCN 23360) with the REM 60cm robotic telescope located at the ESO premise of La Silla (Chile). The observations were performed starting on 2018 October 20 at 23:51 UT (i.e. 4.86 hrs after the burst) and were carried in the g, r, i, z, J, H and K bands. The GRB afterglow is detected in the first set of optical and NIR images. From preliminary photometry we estimate the following magnitudes: r = 17.3 +/- 0.2 i = 16.8 +/- 0.1 at a mean time of 294 min from the GRB time (AB magnitudes, calibrated against the USNO UCAC4 catalogue).
GCN 23363 table
GRB_name GRB181020A
GCN_number 23363
Detection_method Konus-Wind Det
t_trigger 19:00:37.284 UTC
redshift 2.9380
Circular_text TITLE: GCN CIRCULAR NUMBER: 23363 SUBJECT: Konus-Wind observation of GRB 181020A DATE: 18/10/22 14:49:57 GMT FROM: Anastasia Tsvetkova at Ioffe Institute A. Tsvetkova, S. Golenetskii, R.Aptekar, D. Frederiks, M. Ulanov, D. Svinkin, A. Lysenko, A. Kozlova and T. Cline on behalf of the Konus-Wind team, report: The GRB 181020A (Swift-BAT detection: Moss et al., GCN 23349; Sakamoto et al., GCN 23357; Fermi-LAT detection: Axelsson, GCN 23350; Fermi GBM detection: Veres, GCN 23352) triggered Konus-Wind at T0=68437.284 s UT (19:00:37.284). The burst light curve shows a single pulse with a total duration of ~26 s. The emission is seen up to ~5 MeV. As observed by Konus-Wind, the burst had a fluence of 4.17(-0.54,+0.58)x10^-5 erg/cm2, and a 64-ms peak energy flux, measured from T0+7.552 s, of 8.27(-1.99,+2.05)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum of the burst (measured from T0 to T0+15.360 s) is best fit in the 20 keV - 20 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.73(-0.11,+0.13), the high energy photon index beta = -2.35(-0.41,+0.22), the peak energy Ep = 371(-52,+57) keV, chi2 = 80/97 dof. Assuming the redshift z=2.938 (Fynbo et al., GCN 23356) and a standard cosmology model with H_0 = 70 km/s/Mpc, Omega_M = 0.27, and Omega_Lambda = 0.73, we estimate the following rest-frame parameters: the isotropic energy release E_iso is 8.28(-1.07,+1.16)x10^53 erg, the peak luminosity L_iso is 6.47(-1.56,+1.60)x10^53 erg/s, and the rest-frame peak energy of the time-integrated spectrum, Ep,i, is 1461(-205,+225) keV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB181020_T68437/ All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.
GCN 23436 table
GRB_name GRB181020A
GCN_number 23436
Detection_method AstroSat CZTI
Circular_text TITLE: GCN CIRCULAR NUMBER: 23436 SUBJECT: GRB 181020A: AstroSat CZTI detection DATE: 18/11/23 14:34:19 GMT FROM: Vidushi Sharma at IUCAA V. Sharma, T. Khanam and D. Bhattacharya (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 long GRB 181020A, which was also detected by Swift (Moss M. J. et al., GCN 23349, XRT: Goad M. R. et al., GCN 23351, BAT: Sakamoto T. et al., GCN 23357), Fermi (LAT: Axelsson M. et al., GCN 23350 and GBM: Veres P. et al., GCN 23352), and Konus-Wind (Tsvetkova A. et al., GCN 23363). The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with strongest peak at 19:00:40.500 UT. The measured peak count rate is 1000 cts/s above the background in combined data of four quadrants, with a total of 8409 cts. The local mean background count rate was 513.8 cts/s. Using cumulative rates, we measure a T90 of 19.4 s. In preliminary analysis, we find that 749 compton events are associated with this event. 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.