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GRB 181020A

GCN Circular 23349

Subject
GRB 181020A: Swift detection of a burst with an optical counterpart
Date
2018-10-20T19:19:43Z (7 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
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 Circular 23350

Subject
GRB 181020A: Fermi-LAT detection
Date
2018-10-21T01:47:35Z (7 years ago)
From
Magnus Axelsson at Stockholm U. <magaxe@kth.se>
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<mailto: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 Circular 23351

Subject
GRB 181020A: Enhanced Swift-XRT position
Date
2018-10-21T03:35:37Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
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 Circular 23352

Subject
GRB 181020A: Fermi GBM detection
Date
2018-10-21T04:22:04Z (7 years ago)
From
Peter Veres at UAH <veresp@gmail.com>
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 Circular 23353

Subject
GRB 181020A: Swift-XRT refined Analysis
Date
2018-10-21T04:36:46Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
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 Circular 23356

Subject
GRB 181020A: VLT/X-shooter spectroscopy and redshift
Date
2018-10-21T10:09:02Z (7 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
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 Circular 23357

Subject
GRB 181020A: Swift-BAT refined analysis
Date
2018-10-21T14:50:33Z (7 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
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 Circular 23358

Subject
GRB 181020A: LCO Cerro Tololo observations
Date
2018-10-21T15:54:44Z (7 years ago)
From
Cristiano Guidorzi at Ferrara U,Italy <guidorzi@fe.infn.it>
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 Circular 23359

Subject
GRB 181020A: Global MASTER Net OT observations
Date
2018-10-21T18:05:37Z (7 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
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 Circular 23360

Subject
GRB 181020A: Swift/UVOT Detection
Date
2018-10-21T18:39:11Z (7 years ago)
From
Jeffrey Gropp at PSU <jdg44@psu.edu>
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 Circular 23362

Subject
GRB 181020A: REM detection
Date
2018-10-22T12:16:45Z (7 years ago)
From
Andrea Melandri at INAF-OAB <andrea.melandri@brera.inaf.it>
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 Circular 23363

Subject
Konus-Wind observation of GRB 181020A
Date
2018-10-22T14:49:57Z (7 years ago)
From
Anastasia Tsvetkova at Ioffe Institute <tsvetkova@mail.ioffe.ru>
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 Circular 23436

Subject
GRB 181020A: AstroSat CZTI detection
Date
2018-11-23T14:34:19Z (7 years ago)
From
Vidushi Sharma at IUCAA <vidushi@iucaa.in>
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.

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