GRB 160726A
GCN Circular 19731
Subject
GRB 160726A: Swift detection of a short burst
Date
2016-07-26T01:50:31Z (9 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
R. L. C. Starling (U Leicester), A. Y. Lien (GSFC/UMBC),
K. L. Page (U Leicester) and T. Sakamoto (AGU) report on behalf of the
Swift Team:
At 01:34:07 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 160726A (trigger=706052). Swift did not slew immediately
due to an observational constraint.
The BAT on-board calculated location is
RA, Dec 98.821, -6.644 which is
RA(J2000) = 06h 35m 17s
Dec(J2000) = -06d 38' 39"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve showed a double-peaked
structure with a duration of about 1 sec. The peak count rate
was ~14000 counts/sec (15-350 keV), at ~0.7 sec after the trigger.
Due to a Sun observing constraint, Swift cannot slew to the BAT
position until 12:53 UT on 2016 August 10. There will thus be no XRT or
UVOT data for this trigger before this time.
Burst Advocate for this burst is R. L. C. Starling (rlcs1 AT star.le.ac.uk).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)
GCN Circular 19732
Subject
GRB 160726A: Fermi GBM observation
Date
2016-07-26T08:28:00Z (9 years ago)
From
Elisabetta Bissaldi at U.Innsbruk/IAPP <Elisabetta.Bissaldi@uibk.ac.at>
R. Hamburg (UAH), E. Burns (UAH),
and E. Bissaldi (Politecnico & INFN Bari)
report on behalf of the Fermi GBM Team:
"At 01:34:07.72 UT on 26 July 2016, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 160726A (trigger 491189651 / 160726065),
which was also detected by the Swift/BAT
(Starling et al. 2016, GCN 19731).
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi-LAT boresight at the GBM trigger time is 50 degrees.
The GBM light curve consists of two short peaks
with a duration (T90) of about 0.7 s (50-300 keV).
The time-averaged spectrum from T0-0.06 s to T0+0.77 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.0 +/- 0.1 and
the cutoff energy, parameterized as Epeak, is 540 +/- 100 keV.
The event fluence (10-1000 keV) in this time interval is
(1.01 +/- 0.05)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0-0.06 s in the 10-1000 keV band
is 5.5 +/- 0.2 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 19733
Subject
Konus-Wind observation of short GRB 160726A
Date
2016-07-26T14:14:21Z (9 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 short GRB 160726A (Swift/BAT detection: Starling et al., GCN 19731;
Fermi GBM observation: Hamburg et al., GCN 19732)
triggered Konus-Wind at T0=5645.315 s UT (01:34:05.315).
The light curve shows a short pulse with a total duration is ~0.2 s.
The emission is seen up to ~2 MeV.
As observed by Konus-Wind, the burst had a fluence of
(1.5 �� 0.5)x10^-6 erg/cm2 and a 16-ms peak energy flux,
measured from T0+0.016, of (1.1 �� 0.3)x10^-5 erg/cm2
(both in the 20 keV - 10 MeV energy range).
The spectrum of the burst (measured from T0 to T0+0.128 s)
is best fit in the 20 keV - 2 MeV range by a cutoff power-law
(CPL) function with the following model parameters:
the photon index alpha = -0.65(-0.47,+0.71),
and the peak energy Ep = 424(-163,+389) keV,
chi2 = 19.5/20 dof.
Fitting this spectrum with the GRB (Band) function yields
the same alpha and Ep with only an upper limit on beta of -1.8,
chi2 = 19.5/19 dof.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB160726_T05645/
All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.
GCN Circular 19734
Subject
GRB 160726A, Swift-BAT refined analysis
Date
2016-07-27T01:18:02Z (9 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
S. D. Barthelmy (GSFC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
J. P. Norris (BSU), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU),
R. L. C. Starling (U Leicester), 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 160726A (trigger #706052)
(Starling et al., GCN Circ. 19731). The BAT ground-calculated position is
RA, Dec = 98.809, -6.617 deg which is
RA(J2000) = 06h 35m 14.2s
Dec(J2000) = -06d 37' 03.0"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 58%.
The mask-weighted light curve shows a double-peaked structure that
starts at ~T0 and ends at ~T+0.8 s, with the two peaks at ~ T0 and ~T+0.6 s,
respectively. T90 (15-350 keV) is 0.7 +- 0.04 sec (estimated error including
systematics).
The time-averaged spectrum from T+0.0 to T+0.8 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.26 +- 0.13. The fluence in the 15-150 keV band is 2.6 +- 0.2 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.11 sec in the 15-150 keV band
is 3.2 +- 0.3 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
Using a 4-ms binned light curve, the lag analysis finds a lag of
is -3.5 +/- 3 ms for the 100-350 keV to 25-50 keV, and -5 +/- 6 ms for
the 50-100 keV to 15-25 keV band. These numbers are consistent with
those of a short GRB.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/706052/BA/
GCN Circular 19751
Subject
GRB 160726A: CALET Gamma-Ray Burst Monitor detection
Date
2016-08-01T21:03:22Z (9 years ago)
From
Takanori Sakamoto at AGU <tsakamoto@phys.aoyama.ac.jp>
Y. Shimizu (Kanagawa U), A. Yoshida, T. Sakamoto, Y. Kawakubo, M. Moriyama,
Y. Yamada (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), I. Takahashi (IPMU),
Y. Asaoka, S. Ozawa, S. Torii (Waseda U), T. Tamura (Kanagawa U), W. Ishizaki (ICRR),
M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena)
and the CALET collaboration:
The short-duration GRB 160726A (Starling, et al., GCN circ. 19731;
Hamburg, et al., GCN circ. 19732; Frederiks, et al. GCN circ. 19733)
triggered the CALET Gamma-ray Burst Monitor (CGBM) at 01:34:08.25
on 26 July 2016. The burst signal was seen by all CGBM instruments.
The light curve of the SGM shows two peaks. The first weak episode
peaks at T-0.55 s. The second peak starts at T-0.1 s, peaks at T+0.1 s
and ends at T+0.3 s. The T90 duration measured by the SGM data is
0.83 +- 0.09 sec (40-1000 keV).
The light curve is available at
http://cgbm.calet.jp/cgbm_trigger/flight/1153531947/
The CALET data used in this analysis are provided by the Waseda
CALET Operation Center located at the Waseda University.