GRB 150127B

K. Hurley and J. Goldsten, on behalf of the MESSENGER NS GRB team,

I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin,
on behalf of the HEND-Odyssey GRB team,

S. Golenetskii, R. Aptekar, V. Pal'shin, D. Frederiks,
D. Svinkin, and T. Cline on behalf of the Konus-Wind team,

V. Connaughton, M. S. Briggs, C. Meegan, V. Pelassa,
and A. Goldstein, on behalf of the Fermi GBM team,

S. Barthelmy, J. Cummings, N. Gehrels, 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 150127B has been observed by Fermi (GBM trigger 
444060509), Konus-Wind, Mars-Odyssey (HEND), MESSENGER (GRNS), and Swift 
(BAT), so far, at about 50906 s UT (14:08:26). 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:
    140.184 (09h 20m 44s)  -3.205 ( -3d 12' 18")
   Corners:
    140.849 (09h 23m 24s)  -3.717 ( -3d 43' 00")
    140.139 (09h 20m 33s)  -3.925 ( -3d 55' 29")
    139.534 (09h 18m 08s)  -2.676 ( -2d 40' 32")
    140.241 (09h 20m 58s)  -2.479 ( -2d 28' 43")
   ---------------------------------------------
The error box area is 1.0 sq. deg, and its maximum
dimension is 1.7 deg (the minimum one is 43 arcmin).
The Sun distance was 155 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB150127_T50911/IPN/

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

S. Golenetskii, R. Aptekar, D. Frederiks, V. Pal'shin, P. Oleynik,
M. Ulanov, D. Svinkin, A. Tsvetkova, A. Lysenko, and T. Cline
on behalf of the Konus-Wind team, report:

The long-duration GRB 150127B (IPN triangulation: Hurley et al., GCN 
17360
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 ) triggered Konus-Wind at T0=50911.89 s UT (14:08:31.890).

The burst light curve shows two multi-peak emission episodes with a 
total duration of ~90 s.
The emission is seen up to ~1 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB150127_T50911/

As observed by Konus-Wind, the burst
had a fluence of 5.43(-0.21,+0.23)x10^-5 erg/cm2,
and a 256-ms peak flux, measured from T0+10.288 s,
of 2.97(-0.43,+0.43)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+82.176 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.98(-0.10,+0.10)
and Ep = 197(-12,+14) keV (chi2 = 40/58 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.8
(chi2 = 40/57 dof)

The spectrum near the maximum count rate
(measured from T0+0.000 to T0+16.640 s)
is best fit in the 20 keV - 2 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.23(-0.13,+0.14)
and Ep = 252(-13,+14) keV (chi2 = 49/58 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.9
(chi2 = 47/57 dof)

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

P. Jenke (UAH) and A. von Kienlin (MPE) report
 on behalf of the Fermi GBM Team:

"At 14:08:26.68 UT on January 27 2015, the Fermi Gamma-Ray Burst 
Monitor triggered and located 
GRB 150127B (trigger 444060509/150127589). The GBM on-ground 
location, using the Fermi GBM trigger data, is consistent with
the IPN Triangulation (K. Hurley et al., GCN 17360
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 ).  This burst
was also observed by Konus-Wind (S. Golenetskii et al., GCN 17363
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 ).

The angle of the burst direction to the Fermi LAT boresight is 
80 degrees.

The GBM light curve consists of two peaks with a duration
(T90) of about 61 s (50-300 keV).
The time-averaged spectrum from T0+0.0 s to T0+79 s is
adequately fit by a Band function with Epeak = 240 +/- 7 keV,
Alpha =-1.08 +/- 0.01 and Beta = -2.8 +/- 0.2.  The spectrum is also
well fit by a power law function with an exponential 
high-energy cutoff.  The power law index is -1.09 +/- 0.01
and the cutoff energy, parameterized as Epeak, is 250 +/- 5 keV.

The event fluence (10-1000 keV) in this time interval is
(1.99 +/- 0.01)E-05 erg/cm^2. The 1 s peak photon flux measured
starting from T0+55 s in the 10-1000 keV band
is 19.8 +/- 0.4 ph/s/cm^2.

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