GRB 171112A

GRB 171112A: MAXI/GSC detection

S. Sugita (Tokyo Tech), H. Negoro (Nihon U.), S. Nakahira (RIKEN), 
S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai (JAXA),
T. Mihara, M. Sugizaki, W. Iwakiri, M. Shidatsu, F. Yatabe, Y. Takao, M. Matsuoka (RIKEN), 
N. Kawai, T. Yoshii, Y. Tachibana, S. Harita, Y. Muraki, K. Morita (Tokyo Tech), 
A. Yoshida, T. Sakamoto, M. Serino, Y. Kawakubo, Y. Kitaoka, T. Hashimoto (AGU), 
H. Tsunemi, T. Yoneyama (Osaka U.), 
M. Nakajima, T. Kawase, A. Sakamaki (Nihon U.),
Y. Ueda, T. Hori, A. Tanimoto, S. Oda, T. Morita, S. Yamada (Kyoto U.), 
Y. Tsuboi, R. Sasaki, Y. Nakamura, H. Kawai (Chuo U.), 
M. Yamauchi, C. Hanyu, K, Hidaka (Miyazaki U.), 
T. Kawamuro (NAOJ), 
K. Yamaoka (Nagoya U.) 

The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source 
at 20:50:01 UT on 2017 November 12. 
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (20.467 deg, -59.678 deg) = (01 21 52, -59 40 40) (J2000) 
with a statistical 90% C.L. elliptical error region 
with long and short radii of 0.17 deg and 0.12 deg, respectively. 
The roll angle of long axis from the north direction is 107.0 deg counterclockwise. 
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).

We estimated a rectangular error box for the transient source with the following corners
which were independently calculated with respect to each camera.
camera 2:
(20.320, -61.117) deg = (01 21 16, -61 07 01) (J2000)
(19.513, -61.013) deg = (01 18 03, -61 00 47) (J2000)
(21.134, -58.662) deg = (01 24 32, -58 39 42) (J2000)
(21.890, -58.756) deg = (01 27 33, -58 45 23) (J2000)
camera 7:
(19.831, -60.456) deg = (01 19 19, -60 27 20) (J2000)
(19.396, -60.398) deg = (01 17 35, -60 23 51) (J2000)
(20.488, -58.842) deg = (01 21 57, -58 50 31) (J2000)
(20.905, -58.897) deg = (01 23 37, -58 53 48) (J2000)
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).

The X-ray flux averaged over the scan was 437 +- 44 mCrab
(4.0-10.0keV, 1 sigma error).
There was no significant excess flux in the previous transit at UT 19:14
and in the next transit at UT 22:19:10 with an upper limit of 20 mCrab for each.

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

The long-duration GRB 171112A
(MAXI/GSC detection: Sugita et al., GCN Circ. 22118
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triggered Konus-Wind at T0=75019.162 s UT (20:50:19.162).

The burst light curve shows multipeaked structure
which starts at ~T0-204 s and has a total duration of ~310 s.
The emission is seen up to ~2 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB171112_T75019/

As observed by Konus-Wind, the burst
had a fluence of 1.80(-0.33,+0.47)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+0.720 s,
of 2.43(-0.97,+1.17)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+16.640 s)
is best fit in the 30 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.51(-0.30,+0.38),
the high energy photon index beta = -2.67(-1.20,+0.44),
the peak energy Ep = 200(-30,+34) keV
(chi2 = 91/82 dof).

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

M. Stanbro, R. Hamburg, and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:

"At 20:50:17.15 UT on 12 November 2017, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 171112A (trigger 532212622 / 171112868)
which was also detected by the MAXI/GSC (Sugita et al. 2017, GCN 22118
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The GBM on-ground location is consistent with the MAXI position.

The angle from the Fermi LAT boresight at the GBM trigger time is 99
degrees.

The GBM light curve consists of multiple episodes
with a duration (T90) of about 145 s (50-300 keV).
The time-averaged spectrum from T0-45.44 s to T0+104.07 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.49 +/- 0.06 and
the cutoff energy, parameterized as Epeak, is 198 +/- 38 keV.

The event fluence (10-1000 keV) in this time interval is
(1.75 +/- 0.06)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.73 s in the 10-1000 keV band
is 6.50 +/- 0.31 ph/s/cm^2.

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