GRB 170419A

B. Sbarufatti (INAF-OAB/PSU), S. D. Barthelmy (GSFC),
A. A. Breeveld (UCL-MSSL), D. N. Burrows (PSU),
A. Cholden-Brown (PSU), C. Gronwall (PSU), J. A. Kennea (PSU),
N. P. M. Kuin (UCL-MSSL), A. Y. Lien (GSFC/UMBC),
F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester),
M. H. Siegel (PSU) and T. N. Ukwatta (LANL) report on behalf of the
Swift Team:

At 13:26:40 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 170419A (trigger=748898).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 79.866, -21.420 which is 
   RA(J2000)  =  05h 19m 28s
   Dec(J2000) = -21d 25' 12"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single peak
with a duration of about 5 sec.  The peak count rate
was ~1700 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT settled on the field at 13:28:21.4 UT, 101.2 seconds after
the BAT trigger. XRT data were delayed for about 8 minutes until Swift 
exited the SAA. Using promptly downlinked data we find an uncatalogued
X-ray source with an enhanced position: RA, Dec 79.8549, -21.4240 which
is equivalent to:
   RA(J2000)  = 05h 19m 25.18s
   Dec(J2000) = -21d 25' 26.4"
with an uncertainty of 2.5 arcseconds (radius, 90% containment). This
location is 39 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper.  We
cannot determine whether the source is fading at the present time. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of 3.50
x 10^20 cm^-2 (Willingale et al. 2013). 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 591 seconds after the BAT trigger. No credible afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of
the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
XRT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the expected extinction corresponding to E(B-V) of
0.05. 

Burst Advocate for this burst is B. Sbarufatti (boris.sbarufatti AT brera.inaf.it). 
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.)

M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 2234 s of XRT Photon Counting mode data and 3 UVOT
images for GRB 170419A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 79.85468, -21.42386 which is equivalent
to:

RA (J2000): 05h 19m 25.12s
Dec (J2000): -21d 25' 25.9"

with an uncertainty of 1.6 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.

M. Stamatikos (OSU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), N. Gehrels (GSFC),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), B. Sbarufatti (INAF-OAB/PSU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-190 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 170419A (trigger #748898)
(Sbarufatti et al., GCN Circ. 21013
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 ).  The BAT ground-calculated position is
RA, Dec = 79.854, -21.433 deg which is
  RA(J2000)  =  05h 19m 25.1s
  Dec(J2000) = -21d 25' 58.0"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 53%.

The mask-weighted light curve shows a single-pulse structure that starts
and peaks at ~T0. The main emission ends at ~T+3 s, with a tail that
lasts till ~T+9 s. T90 (15-350 keV) is 8.18 +- 2.00 sec (estimated error
including systematics).

The time-averaged spectrum from T-0.39 to T+8.92 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.06 +- 0.26.  The fluence in the 15-150 keV band is 3.1 +- 0.5 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+0.47 sec in the 15-150 keV band
is 1.5 +- 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/748898/BA/

V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), S. J.
LaPorte (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), B.
Mingo (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U.
Leicester) and	report on behalf of the Swift-XRT team: report on
behalf of the Swift-XRT team:

We have analysed 6.2 ks of XRT data for GRB 170419A, from 550 s to 59.3
ks after the  BAT trigger. The data are entirely in Photon Counting
(PC) mode. 

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.02 (+0.14, -0.12).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.7 (+/-0.3). The
best-fitting absorption column is  1.6 (+1.2, -1.0) x 10^21 cm^-2, in
excess of the Galactic value of 3.5 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 4.1 x 10^-11 (5.0 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     1.6 (+1.2, -1.0) x 10^21 cm^-2
Galactic foreground: 3.5 x 10^20 cm^-2
Excess significance: 2.1 sigma
Photon index:	     1.7 (+/-0.3)

If the light curve continues to decay with a power-law decay index of
1.02, the count rate at T+24 hours will be 1.5 x 10^-3 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.3 x
10^-14 (7.7 x 10^-14) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00748898.

This circular is an official product of the Swift-XRT team.

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 170419A detected by SWIFT
(trigger 748898) with the Zadko robotic telescope (D=100cm)
located at the observatory - Gingin, Australia.

The observations started 22.3h after the GRB trigger.
The elevation of the field decreased from
49 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 XRT error box provided by Goad et al.
(GCNC 21015):

t0+22.3h to t0+22.9h : Rlim = 21.0

Magnitudes were estimated with the nearby NOMAD1 stars
and are not corrected for galactic dust extinction.

A. Cucchiara, D. Morris (U. of Virgin Islands),
C. Guidorzi (U. Ferrara), and B. Gendre  (U. of Virgin
Islands) report on behalf of a larger collaboration:

"On April 19.71 UT  (T_0 +3.6h) we began observing the
field of GRB 170419A (Sbarufatti et al. GCN #21013
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 ) using
the Las Cumbres Observatory Global Network 1m Sutherland facility.

We obtained a series of observations in R and I bands for a total
of 5 minutes on target in each filter.
We identified no optical counterpart within the Enhanced Swift-XRT
position (Goad et al. GCN #21015
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 ) at the following 3-sigma limits:

R > 20.9 mag
I > 20.8 mag

These values are calibrated against nearby USNO-B1 sources and
are not corrected for Galactic Extinction."

M. H. Siegel (PSU) and B. Sbarufatti (INAF-OAB/PSU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 170419A
592 s after the BAT trigger (Sbarufatti et al., GCN Circ. 21013
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 ).
No optical afterglow consistent with the XRT position
(Goad et al. GCN Circ. 21015
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 )
is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           592          742          147         >21.1
white              592        13376         1194         >22.0
v                  748        19148          594         >19.6
b                  846         7551          313         >20.4
u                  822        23245         1108         >21.0
w1                 797         7141          313         >20.0
m2                 773         6935          274         >19.9
w2                1027        17141          672         >20.7

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.05 in the direction of the burst
(Schlegel et al. 1998).