with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). The BAT light curve shows a single
with a duration of about 10 sec. The peak count rate
was ~3000 counts/sec (15-350 keV), at ~3 sec after the trigger.
Due to a Sun observing constraint, Swift cannot slew to the BAT
position until 05:29 UT on 2017 June 19. There will thus be no XRT or
UVOT data for this trigger before this time.
Burst Advocate for this burst is A. Cholden-Brown (aaronb AT swift.psu.edu).
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 #21019
P. Veres and C. Meegan (both UAH)
report on behalf of the Fermi GBM Team:
"At 21:33:46.807 UT on 19 April 2016, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 170419B (trigger 514330431 / 170419898).
which was also detected by the Swift/BAT
(Cholden-Brown et al., GCN 21016). The GBM on-ground
location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 41 degrees.
The GBM light curve shows a single pulse
with a duration (T90) of about 24 s (50-300 keV).
The time-averaged spectrum from T0-0.5 s to T0+5.1 s is
best fit by a Band function with Epeak = 116 +/- 19 keV,
alpha = -0.03 +/- 0.29, and beta = -2.07 +/- 0.15.
The event fluence (10-1000 keV) in this time interval is
(2.4 +/- 0.2)E-6 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.2 s in the 10-1000 keV band
is 3.8 +/- 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 #21024
A. Klotz, D. Turpin (IRAP-CNRS-OMP), D. Macpherson (UWA/ICRAR), D.
Coward (UWA),
M. Boer, (UNS-CNRS-OCA), Gendre B. (UVI - Etelman Obs.),
A. Williams (PO-UWA), R. Martin (PO-UWA)
report:
We imaged the field of GRB 170419B detected by SWIFT
(trigger 748947) with the Zadko robotic telescope (D=100cm)
located at the observatory - Gingin, Australia.
The observations started 13.3h after the GRB trigger.
The elevation of the field decreased from
31 degrees above horizon and weather conditions
were good.
We co-added a series of exposures but we did not find any
optical transcient in the BAT error box provided by
Cholden-Brown et al. (GCNC 21016):
t0+13.3h to t0+13.5h : Rlim = 19.2
Magnitudes were estimated with the nearby NOMAD1 stars
and are not corrected for galactic dust extinction.

with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 52%.
The mask-weighted light curve shows a single-pulse structure that starts at
~ T0 and peaks at ~T+2. The major part of the pulse ends at ~T+10 s, and
the weaker tail emission lasts till ~T+90 s. T90 (15-350 keV) is
77.2 +- 9.8 sec (estimated error including systematics).
The time-averaged spectrum from T+0.3 to T+88.0 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.47 +- 0.13. The fluence in the 15-150 keV band is 1.9 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+1.98 sec in the 15-150 keV band
is 2.4 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence
level.
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/748947/BA/