GRB 161218B
GCN Circular 20324
Subject
GRB 161218B: Astrosat CZTI detection
Date
2016-12-21T18:20:09Z (10 years ago)
From
Vedant Kumar at Astrosat/CZTI/IUCAA <vedant@iucaa.in>
V. Kumar, D. Bhattacharya and V. Bhalerao (IUCAA), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data showed clear detection of a long duration and bright GRB161218B (Fermi-GBM detection: Hamburg et al., GCN 20286)
in the 40-200 keV energy range. The light curve shows multiple peak structure with at least 4 clear peaks and main peak at 08:32:42.0 UT followed
by a weaker emission, 1.35 secs after the Fermi- GBM trigger(consistent with GCN 20286). The measured peak count rate is 738.478 counts/sec above
the background in combined data of four quadrants, with a total of 6025.78 counts. The local mean background count rate was 328.52 counts/sec.
Using cumulative rates, we measure a T90 of 29.0 sec.
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 20304
Subject
Konus-Wind observation of GRB 161218B
Date
2016-12-20T10:06:29Z (10 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
D. Frederiks, S. Golenetskii, R.Aptekar, P. Oleynik, M. Ulanov,
D. Svinkin, A. Tsvetkova, A.Lysenko, A. Kozlova, and T. Cline,
on behalf of the Konus-Wind team, report:
The long GRB 161218B (Fermi-GBM detection: Hamburg et al., GCN 20286;
POLAR observation: Wang et al., GCN 20288;
IPN triangulation: Svinkin et al., GCN 20303)
triggered Konus-Wind at T0=30761.134 s UT (08:32:41.134).
The light curve starts with a bright, short pulse followed by
a weaker emission; the total duration of the burst is ~30 s.
The emission is seen up to ~10 MeV.
As observed by Konus-Wind, the burst had a fluence of
(8.6 �� 0.4)x10^-5 erg/cm2 and a 64-ms peak energy flux,
measured from T0+1.344, of (2.7 �� 0.2)x10^-5 erg/cm2
(both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+34.560 s)
is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.42 (-0.08,+0.08),
the high energy photon index beta = -3.37 (-0.80,+0.31),
the peak energy Ep = 203 (-8,+8) keV,
chi2 = 106/97 dof.
The spectrum near the peak count rate (measured from T0+0.256
to T0+1.536 s) is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.08 (-0.18,+0.21),
the high energy photon index beta = -2.71 (-0.24,+0.18),
the peak energy Ep = 203 (-15,+16) keV,
chi2 = 69/68 dof.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB161218_T30761/
All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.
GCN Circular 20303
Subject
IPN Triangulation of GRB 161218B (long/very bright)
Date
2016-12-20T09:25:37Z (10 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, A. Kozlova,
and T. Cline on behalf of the Konus-Wind team,
K. Hurley, on behalf of the IPN,
S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer,
on behalf of the Swift-BAT team,
A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
and
V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa,
and A. Goldstein, on behalf of the Fermi GBM team, report:
The long-duration, very bright GRB 161218B has been detected by Fermi
(GBM; Hamburg et al., GCN Circ. 20286), Konus-Wind, INTEGRAL (SPI-ACS),
Swift (BAT), and POLAR (Wang et al., GCN Circ. 20288), so far, at about
30760 s UT (08:32:40). The burst was outside the coded field of view of
the BAT.
We have triangulated it to a preliminary, 3 sigma error box whose
coordinates are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
0.888 (00h 03m 33s) -14.700 (-14d 42' 00")
Corners:
2.344 (00h 09m 23s) -18.473 (-18d 28' 23")
3.138 (00h 12m 33s) -17.987 (-17d 59' 13")
359.466 (23h 57m 52s) -10.927 (-10d 55' 37")
358.690 (23h 54m 46s) -11.401 (-11d 24' 03")
---------------------------------------------
The error box area is 7.05 sq. deg, and its maximum
dimension is 8.0 deg (the minimum one is 53.5 arcmin).
The Sun distance was 87 deg.
This box may be improved.
A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB161218_T30761/IPN
The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.
GCN Circular 20288
Subject
GRB 161218B: POLAR observation
Date
2016-12-18T19:04:42Z (10 years ago)
From
Yuanhao Wang at IHEP/CAS <wangyuanhao@ihep.ac.cn>
Y. H. Wang (IHEP), Z. H. Li (IHEP), S. L. Xiong (IHEP)
report for the POLAR collaboration:
At��2016-12-18T08:32:41.341��UT��(T0),��during��a��routine��on-ground��
search��of��data,��POLAR��detected the GRB 161218B,��which��was��also
detected��by��the Fermi/GBM (trigger 503742764/161218356).
The��POLAR��light��curve��consists��of��multiple��peaks,
with��a��duration��(T90) of��26.28��s��measured��from��T0+1.0��s .
The��1s��peak��rate��measured��from��T0+1.25��s��is��9849��cnts/s,
The��total��counts��is��about��29340 cnts.The��above��measurements��are
in��the��energy��range��of��about��80-500� �keV.
The preliminary estimation of minimum detectable polarization(MDP)
is 36.8%[3-sigma, statistical only]. Follow-up observations are
strongly encouraged.
LC_URL:
http://polar.ihep.ac.cn/grb/2016/GRB161218B/lc/POLAR_lc_grb161218356.png
Using��the��best��location��from��the��Fermi/GBM,��which��is��(J2000):
RA: 358.640 [deg]
Dec: -16.950 [deg]
Err: 1.00 [deg]
the��incident��angle��in��POLAR��coordinate��at��T0��is:
theta:�� 77.7612 ��[deg]
phi: ����252.239�� [deg]
The��analysis��results��presented��above��are��preliminary.
POLAR is a dedicated Gamma-Ray Burst polarimeter (50-500 keV) on-board
the Chinese space laboratory Tiangong-2 launched on Sep 15, 2016. More
information about POLAR can be found at http://polar.ihep.ac.cn/en/,
http://isdc.unige.ch/polar/ and http://polar.psi.ch/html/
GCN Circular 20286
Subject
GRB 161218B: Fermi GBM detection
Date
2016-12-18T18:19:00Z (10 years ago)
From
Rachel Hamburg at UAH <rkh0007@uah.edu>
R. Hamburg (UAH), C. Meegan (UAH), and H. Yu (MPE)
report on behalf of the Fermi GBM Team:
"At 08:32:40.65 UT on 18 December 2016, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 161218B (trigger 503742764 / 161218356).
The on-ground calculated location, using the GBM trigger
data, is RA = 358.64, DEC = -16.95, with an uncertainty
of 1.00 degrees (radius, 1-sigma containment,
statistical only; there is additionally a systematic
error which we have characterized as a core-plus-tail model, with 90% of
GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg
systematic error. [Connaughton et al. 2015, ApJS, 216, 32] ).
The trigger resulted in an Autonomous Repoint Request (ARR)
by the GBM Flight Software owing to the high peak flux of the GRB.
This ARR was accepted and the spacecraft slewed to the GBM in-flight
location. The initial angle from the Fermi LAT boresight to
the GBM ground location is 80 degrees.
The GBM light curve consists of multiple peaks
with a duration (T90) of about 26 s (50-300 keV).
The time-averaged spectrum from T0-2.0 s to T0+32.8 s is
best fit by a Band function with Epeak = 214.80 +/- 2.51 keV,
alpha = -0.51 +/- 0.01, and beta = -3.06 +/- 0.10.
The event fluence (10-1000 keV) in this time interval is
(8.91 +/- 0.06)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.7 s in the 10-1000 keV band
is 74.1 +/- 0.6 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."