GRB 170305A
GCN Circular 20818
Subject
GRB170305A: Fermi GBM detection
Date
2017-03-05T20:28:27Z (8 years ago)
From
Matthew Stanbro at UAH/Fermi <mcs0001@uah.edu>
M. Stanbro (UAH), A. von Kienlin (MPE), and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 06:09:06.78 UT on 05 March 2017, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 170305A (trigger 510386951 / 17035256).
The on-ground calculated location, using the GBM trigger
data, is RA = 38.66, DEC = 12.09, with an uncertainty
of 3.7 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] ).
This burst was also independently detected by INTEGRAL SPI-ACS.
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 59 degrees.
The GBM light curve consists of 1 episode
with a duration (T90) of about 0.44 s (50-300 keV).
The time-averaged spectrum from T0-0.064 s to T0+0.384 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.53 +/- 0.08 and
the cutoff energy, parameterized as Epeak, is 293 +/- 24 keV
The event fluence (10-1000 keV) in this time interval is
(1.29 +/- 0.07)E-06 erg/cm^2. The 64-msec peak photon flux measured
starting from T0+0.0 s in the 10-1000 keV band
is 31.0 +/- 1.6 ph/s/cm^2.
A Band function fits the spectrum equally well
with Epeak= 233 +/- 35 keV, alpha = -0.42 +/- 0.13 and beta = -2.06 +/-
0.13.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 20824
Subject
IPN Triangulation of GRB 170305A (short)
Date
2017-03-06T18:57:17Z (8 years ago)
From
Dmitry Svinkin at Ioffe Institute <svinkin@mail.ioffe.ru>
K. Hurley, on behalf of the IPN,
I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin,
on behalf of the HEND-Odyssey GRB team,
D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, A. Kozlova,
and T. Cline on behalf of the Konus-Wind team,
A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,
V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa,
and A. Goldstein, on behalf of the Fermi GBM team,
S. Barthelmy, J. Cummings, N. Gehrels, H. Krimm, and D. Palmer,
on behalf of the Swift-BAT team,
and
W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:
The short-duration GRB 170305A (Stanbro at al., GCN Circ. 20818)
has been detected by Fermi (GBM), Konus-Wind, INTEGRAL (SPI-ACS),
Mars-Odyssey (HEND), and Swift (BAT), so far,
at about 22147 s UT (06:09:07).
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:
39.658 (02h 38m 38s) +9.901 ( +9d 54' 05")
Corners:
39.371 (02h 37m 29s) +11.649 (+11d 38' 56")
39.926 (02h 39m 42s) +9.863 ( +9d 51' 47")
39.796 (02h 39m 11s) +8.512 ( +8d 30' 43")
39.391 (02h 37m 34s) +9.939 ( +9d 56' 21")
---------------------------------------------
The error box area is 2881 sq. arcmin, and its maximum
dimension is 3.16 deg (the minimum one is 29.0 arcmin).
The Sun distance was 55 deg.
This box may be improved.
A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB170305_T22143/IPN
The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.
GCN Circular 20837
Subject
GRB 170305A: POLAR observation
Date
2017-03-08T09:24:45Z (8 years ago)
From
Radek Marcinkowski at PSI/POLAR <radoslaw.marcinkowski@psi.ch>
R. Marcinkowski (PSI), H.L. Xiao (PSI) and W. Hajdas (PSI) report on behalf
of the POLAR collaboration:
At 2017-03-05 06:09:06.8 UT(T0), during a routine on-ground search of data,
POLAR detected GRB 170305A, which was also observed by Fermi GBM (trigger
# 510386951; GCN 20818, M. Stanbro) and Konus-Wind, INTEGRAL (SPI-ACS),
Mars-Odyssey (HEND), and Swift (BAT) (GCN 20824, K. Hurley et al.).
The POLAR light curve consists of 1 peak with duration (T90) of
0.3 +/- 0.05 s measured from T0. The 64ms peak flux at T0 + 0.1 s
is equal to 9630 +/- 120 counts/sec. POLAR recorded 2400 events from
the burst. Above measurements are in the energy range of about 20 - 500 keV.
LC_URL: http://polar.psi.ch/triggers/GRB_170305A_raw.png
or http://polar.psi.ch/pub/lc.php?event=GRB+170305A
Using the best location from IPN Triangulation (GCN 20824, K. Hurley et al.),
which is (J2000):
RA : 39.66 deg
Dec: 9.90 deg
the incident angle in the POLAR coordinate at T0 is:
Theta: 31.4 deg
Phi: 239.1 deg
The analysis results presented above are preliminary. POLAR is a dedicated
Gamma-Ray Burst polarimeter which was launched on-board the Chinese space
laboratory Tiangong-2 (TG-2) on Sep 15, 2016. The energy detection range
of POLAR is ~ 50-500 keV. More information about POLAR can be found at
http://polar.psi.ch/pub , http://polar.ihep.ac.cn/en/
and http://isdc.unige.ch/polar/ .
This message is quotable in publications.