Gamma-ray Burst 170305A
(All information courtesy of the instrument teams.)
Previous IAU Circulars
Results of Observations
- GCN Circular #20818
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
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 +/-
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
- GCN Circular #20824
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,
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
RA(2000), deg Dec(2000), deg
39.658 (02h 38m 38s) +9.901 ( +9d 54' 05")
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
The Konus-Wind time history and spectrum will be given in a forthcoming
- GCN Circular #20837
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.
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.
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Jochen Greiner, last update: 13-Mar-2017