GRB 181020A
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.
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 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 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 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 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 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