GRB 170607B
GCN Circular 21232
Subject
GRB 170607B: AstroSat CZTI detection
Date
2017-06-09T12:09:39Z (8 years ago)
From
Vidushi Sharma at IUCAA <vidushi@iucaa.in>
V. Sharma and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the Astrosat CZTI collaboration:
Routine on-ground analysis of AstroSat CZT Imager data showed the detection of a bright GRB 170607B, which was also detected by Fermi GBM (designation: bn170607946) at 2017-06-07 22:41:58.947 UT.
The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with the strongest peak at 22:42:04.947 UT, ~6 s after the Fermi Trigger. The measured peak count rate is 496.1 cts/s above the background in combined data of four quadrants, with a total of 7677 cts. The local mean background count rate was 354.9 cts/s. Using cumulative rates, we measure a T90 of 21.8 s.
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 21238
Subject
GRB 170607B: Fermi GBM detection
Date
2017-06-09T19:27:07Z (8 years ago)
From
Rachel Hamburg at UAH <rkh0007@uah.edu>
R. Hamburg (UAH), C. Meegan (UAH), and E. Bissaldi (Politecnico & INFN Bari)
report on behalf of the Fermi GBM Team:
"At 22:41:58.95 UT on 07 June 2017, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 170607B (trigger 518568123 / 170607946)
which was also detected by the AstroSat CZTI
(Sharma et al. 2017, GCN 21232).
The on-ground calculated location, using the GBM trigger
data, is RA = 257.1, DEC = -35.7, with an uncertainty
of 1.5 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 angle from the Fermi LAT boresight at the GBM trigger time is 99
degrees.
The GBM light curve consists of a spiked structure
with a duration (T90) of about 18 s (50-300 keV).
The time-averaged spectrum from T0-5.1 s to T0+22.5 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -0.77 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 627 +/- 21 keV.
The event fluence (10-1000 keV) in this time interval is
(5.9 +/- 0.1)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+20.4 s in the 10-1000 keV band
is 12.0 +/- 0.4 ph/s/cm^2.
A Band function fits the spectrum equally well
with Epeak= 619 +/- 22 keV, alpha = -0.76 +/- 0.02 and beta =
-3.5 +/- 0.7.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 21242
Subject
IPN Triangulation of GRB 170607B
Date
2017-06-10T14:15:43Z (8 years ago)
From
Anna Kozlova at Ioffe Institute <ann_kozlova@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,
A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks, D.Svinkin,
and T. Cline on behalf of the Konus-Wind team,
V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa,
and A. Goldstein, on behalf of the Fermi GBM 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
W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:
The long-duration GRB 170607B (Sharma et al., GCN Circ. 21232;
Hamburg et al., GCN 21238) has been detected by Konus-Wind,
Fermi (GBM), INTEGRAL (SPI-ACS), Mars-Odyssey (HEND), and
AstroSat (CZTI), so far, at about 81720 s UT (22:42:00).
We have triangulated it to a preliminary, 3 sigma error box whose
coordinates are:
---------------------------------------------
RA(2000), deg Dec(2000), deg
---------------------------------------------
Center:
246.661 (16h 26m 39s) -39.159 (-39d 09' 32")
Corners:
245.286 (16h 21m 09s) -37.113 (-37d 06' 45")
247.857 (16h 31m 26s) -41.075 (-41d 04' 30")
248.366 (16h 33m 28s) -41.126 (-41d 07' 34")
245.736 (16h 22m 57s) -37.211 (-37d 12' 39")
---------------------------------------------
The error box area is 1.3 sq. deg, and its maximum
dimension is 4.67 deg (the minimum one is 17.8 arcmin).
The Sun distance was 160 deg.
This box may be improved.
A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB170607_T81725/IPN/
The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.
GCN Circular 21246
Subject
Konus-Wind observation of GRB 170607B
Date
2017-06-11T13:36:09Z (8 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 170607B (AstroSat CZTI detection: Sharma et al., GCN 21232;
Fermi GBM detection: Hamburg et al., GCN 21238;
IPN triangulation: Hurley et al., GCN 21242)
triggered Konus-Wind at T0=81725.036 s UT (22:42:05.036).
The burst light curve shows a bright, multi-peaked pulse
which started at ~T0-9 s an had a total duration of ~35 s.
A weak count rate increase is also visible around ~T0+100 s
The emission is seen up to ~10 MeV.
As observed by Konus-Wind, the burst had a fluence of
(7.2 �� 0.8)x10^-5 erg/cm2 and a 64-ms peak energy flux,
measured from T0+18.752 s of (8.1 �� 1.2)x10^-6 erg/cm2
(both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+22.528 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 = -0.77 (-0.07,+0.08),
the high energy photon index beta = -2.87 (-1.27,+0.40),
the peak energy Ep = 512 (-50,+49) keV,
chi2 = 105/97 dof.
The spectrum near the peak count rate (measured from T0+14.336
to T0+22.528 s) is best fit in the 20 keV - 5 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.58 (-0.32,+0.38),
the high energy photon index beta = -2.22 (-1.17,+0.22),
the peak energy Ep = 244 (-51,+103) keV,
chi2 = 70/72 dof.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB170607_T81725/
All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.