GRB 190304A

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,

A. Goldstein, M. S. Briggs, and C. Wilson-Hodge
on behalf of the Fermi GBM team,

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

and

W. Boynton, C. Fellows, K. Harshman, H. Enos, and R. Starr,
on behalf of the GRS-Odyssey GRB team, report:

A long-duration GRB 190304A was detected by Fermi (GBM;
trigger 573421048), Konus-Wind, Mars-Odyssey (HEND),
and Swift (BAT), at about 70642 s UT (19:37:22).
The burst was 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:
    16.909 (01h 07m 38s) -80.695 (-80d 41' 41")
  Corners:
    14.558 (00h 58m 14s) -80.443 (-80d 26' 35")
    20.223 (01h 20m 54s) -80.804 (-80d 48' 14")
    19.382 (01h 17m 32s) -80.930 (-80d 55' 49")
    13.675 (00h 54m 42s) -80.556 (-80d 33' 21")
  ---------------------------------------------
The error box area is about 581 sq. arcmin, and its maximum
dimension is 1.09 deg (the minimum one is 9.7 arcmin).
The Sun distance was about 76 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB190304_T70641/IPN/

The time history and spectrum will be given in forthcoming
GCN Circulars.

A. Kozlova, S. Golenetskii, R. Aptekar, D. Frederiks,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration GRB 190304A
(IPN Triangulation: Hurley et al., GCN Circ. 23942
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triggered Konus-Wind at T0=70641.622 s UT (19:37:21.622).

The burst light curve shows a double-peaked structure
started at ~T0-1.6 s with a total duration of ~3.3 s.
The emission is seen up to ~1 MeV.

As observed by Konus-Wind, the burst
had a fluence of 2.48(-0.35,+0.38)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0-0.028 s,
of 4.70(-1.01,+1.03)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 1 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.61(-0.56,+0.69)
and Ep = 97(-15,+22) keV (chi2 = 84/60 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.4
(chi2 = 84/59 dof).

The spectrum near the maximum count rate
(measured from T0 to T0+0.256 s)
is best fit in the 20 keV - 1 MeV range
by a power law with exponential cutoff model
with  alpha = -0.15(-0.43,+0.49)
and Ep = 153(-19,+25) keV (chi2 = 22/22 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.6
(chi2 = 21/21 dof).

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB190304_T70641/

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.