GRB 170403A

O.J. Roberts (USRA/NASA) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 13:59:17.80 UT on the 3rd of April 2017, the
Fermi Gamma-Ray Burst Monitor triggered and
located GRB 170403A (trigger 512920762 / 170403583).
The on-ground calculated location using the GBM
trigger data is,

RA = 267.08, DEC = +14.53 (J2000 degrees)

with an uncertainty of 7.16 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 88 degrees.

The GBM light curve consists of a short, bright GRB with
emission over a duration (T90) of about 1s
(50-300 keV). The time-averaged spectrum from T0-0.096 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
-1.01 +/- 0.14 and the cutoff energy, parameterized as
Epeak is 470 +/- 163 keV.

The event fluence (10-1000 keV) in this time interval is
(3.9 +/- 0.2)E-07 erg/cm^2. The 64 ms peak photon flux
measured starting from T0+0 s in the 10-1000 keV band
is 16.6 +/- 1.5 ph/s/cm^2.

The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."

D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, A. Kozlova,
and T. Cline on behalf of the Konus-Wind team,

K. Hurley, on behalf of the IPN,

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

S. Barthelmy, J. Cummings, H. Krimm, and D. Palmer,
on behalf of the Swift-BAT team, report:

The short-duration GRB 170403A has been detected by
Fermi (GBM; Roberts and Meegan, GCN Circ. 20975
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 ), Konus-Wind, INTEGRAL 
(SPI-ACS), and Swift (BAT), so far, at about 50358 s UT (13:59:18).
The burst was probably outside the coded field of view of the BAT.

We have triangulated it to a preliminary, 3 sigma error box whose
coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
   259.339 (17h 17m 21s) +18.373 (+18d 22' 24")
  Corners:
   259.284 (17h 17m 08s) +20.795 (+20d 47' 43")
   259.729 (17h 18m 55s) +15.801 (+15d 48' 04")
   259.375 (17h 17m 30s) +16.007 (+16d 00' 24")
   258.911 (17h 15m 39s) +21.035 (+21d 02' 06")
  ---------------------------------------------
The error box area is 1.63 sq. deg, and its maximum
dimension is 5.29 deg (the minimum one is 19.4 arcmin).
The Sun distance was 110 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB170403_T50358/IPN

The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.

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 170403A (Fermi-GBM observation: Roberts & Meegan,
GCN 20975
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 ; IPN triangulation: Svinkin et al., GCN 20976
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 ) triggered
Konus-Wind at T0=50358.544 s UT (13:59:18.544).

The light curve shows a single pulse with a duration of ~0.12s.

As observed by Konus-Wind, the burst had a fluence of
(5.4 �� 0.8)x10^-7 erg/cm2 and a 16-ms peak energy flux,
measured from T0-0.016, of (7.6 �� 1.8)x10^-6 erg/cm2
(both in the 20 keV - 10 MeV energy range).

The time-integrated 3-channel spectrum of the burst, measured from
T0-0.064 s to T0+0.064 s, can be modeled by an exponentially cutoff 
power law with alpha = -0.16 (-0.36, +0.46) and Ep = 357(-58,+90) keV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB170403_T50358/

All the quoted errors are estimated at the 1 sigma confidence level.
All the presented results are preliminary.