GRB 170127C

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/hard GRB 170127C (Fermi-GBM detection: Bissaldi et al.,
GCN 20543
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 ; Fermi-LAT detection: Moretti et al., GCN 20544
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 ;
AGILE analysis: Ursi et al., GCN 20545
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 ;
AstroSat CZTI Sharma:  Verrecchia et al., GCN 20561
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 ;
POLAR observation: Marcinkowski et al., GCN 20563
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 )
triggered Konus-Wind at T0=5744.660 s UT (01:35:44.660).

The light curve shows a bright, hard initial pulse with a
duration of ~0.170 ms, followed, after a short period of quiescence,
by a weaker and softer emission episode lasing for ~16 s.
Even more weaker and softer emission is traced in the KW light curve
up to ~T0+90 s.
The emission in the initial pulse is seen up to ~5 MeV.

As observed by Konus-Wind, the burst had a total fluence of
1.62(-0.25, +0.49)x10^-5 erg/cm2 and a 16-ms peak energy flux,
measured from T0, of (1.1 �� 0.1)x10^-4 erg/cm2
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the initial pulse
(measured from T0 to T0+0.192 s)
is best fit in the 20 keV - 15 MeV range
by a power law with exponential cutoff (CPL) model
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -0.01 (-0.14,+0.16), Ep = 887 (-88,+90) keV,
chi2 = 46/55 dof.

The time-averaged spectrum of the extended emission
(measured from T0+0.256 to T0+16.640 s)
is best fit in the 20 keV - 15 MeV range
by the CPL model with alpha = -1.19 (-0.29,+0.35),
Ep = 307 (-98,+342) keV, chi2 = 91/98 dof.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB170127_T05744/

All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.

V. D�Elia (ASDC) reports on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the Fermi/LAT-detected burst GRB 170127C (Bissaldi et al., GCN Circ 20543
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 , Moretti et al., GCN Circ 20544
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 )  in a series of observations tiled on the sky. The total exposure time is 5 ks, distributed over 7 tiles; the maximum exposure at a single sky location was 1.4 ks. The data were collected between T0+61.2 and T0+77.4 ks and are entirely in Photon Counting (PC) mode. 

No new source is detected in the XRT field of view, at a count rate limit in the range 0.005-0.01 cts/s.

The results of the XRT-team automatic analysis of the tiled XRT observations, including a position-specific upper limit calculator, areavailable at http://www.swift.ac.uk/xrt_products/TILED_GRB00063.

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

R. Marcinkowski (PSI), H.L. Xiao (PSI), W. Hajdas (PSI), Yi Zhao (IHEP), 
M. Kole (DPNC) and S.L. Xiong (IHEP) report on behalf of the POLAR 
collaboration:

At 2017-01-27 01:35:48.7 UT(T0), during a routine on-ground search of data,
POLAR detected GRB 170127C, which was also observed by Fermi GBM
(trigger # 507173752) and reported by Fermi GBM (Bissaldi et al. GCN 20543
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 ),
Fermi-LAT (E. Moretti et al. GCN 20544
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 ), Agile (A. Ursi et al. GCN 20545
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 )
and AstroSat (V. Sharma et al. GCN 20561
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 ).

The POLAR light curve consists of 1 short (~0.15 s), strong peak followed by
longer and weaker multi peak structure with duration (T90) of 22.0 +/- 0.2 s
measured from T0. The light curve is compatible with the one from
Fermi-GBM. The 0.2 s peak flux at T0 + 0.2 s  is equal to
13000 +/- 140 counts/sec. POLAR recorded 3600 +/- 140 events from the burst.
Above measurements are in the energy range of about 20 - 500 keV.

LC_URL: http://polar.psi.ch/triggers/GRB_170127C_raw.png
     or http://polar.psi.ch/pub/lc.php?event=GRB+170127C

Using the best location from Fermi LAT (E. Moretti et al. GCN 20544
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 ),
which is:
RA : 339.3 [deg]
Dec: -63.9 [deg]
Err:   0.4 [deg]

the incident angle in the POLAR coordinate at T0 is:
Theta: 41.8 [deg]
Phi: 157.6 [deg]

The analysis results presented above are preliminary. Calibration of the
instrument is ongoing. POLAR is a dedicated Gamma-Ray Burst polarimeter which
was launched on-board the Chinese space laboratory Tiangong-2 (TG-2) on
Sep 15, 2016. The energy detection range of POLAR is ~ 50-500 keV.
More information about POLAR can be found at http://polar.psi.ch/pub ,
 http://polar.ihep.ac.cn/en/ and http://isdc.unige.ch/polar/ .

This message is quotable in publications.

V. Sharma, D. Bhattacharya and V. Bhalerao (IUCAA), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:

Analysis of AstroSat CZTI data showed clear detection of GRB170127C (Fermi detection: E. Bissaldi et al., GCN Circ. 20543
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 ) in the 40-200 keV energy range. The light curve shows single peak structure with main peak at 01:35:47.79 UT, coincident with Fermi trigger. The measured peak count rate is 895.2 counts/sec above the background in combined data of four quadrants, with a total 904.3 counts. The local mean background count rate was 416.8 counts/sec. Using cumulative rates, we measure a T90 of 0.91 secs.

It was clearly detected in the CsI anticoincidence detector (Veto) also as bright detection in the 100-500 keV energy range.

CZTI GRB detections are reported regularly on the payload site at http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.

P. A. Evans (U. Leicester) reports on behalf of the Swift team:

Swift has initiated a series of observations, tiled on the sky, of the
Fermi/LAT GRB 170127C. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00063

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. The probability of finding
serendipitous sources, unrelated to the Fermi/LAT event is high: any X-ray source
considered to be a probable afterglow candidate will be reported via a GCN Circular
after manual consideration.

Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).

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

AGILE analysis of GRB 170127C (Fermi/GBM trigger 507173752)

A. Ursi (INAF/IAPS), P. Munar-Adrover (INAF/IAPS), F. Verrecchia (ASDC
and INAF/OAR), M. Tavani (INAF/IAPS, and Univ. Roma Tor Vergata), Y.
Evangelista (INAF/IAPS), F. Lucarelli (ASDC and INAF/OAR), F. Fuschino
(INAF/IASF-Bo), I. Donnarumma (INAF/IAPS), G. Minervini (INAF/IAPS), M.
Marisaldi (INAF/IASF-Bo and Bergen University), A. Bulgarelli, V. Fioretti
(INAF/IASF-Bo), C. Pittori (ASDC and INAF/OAR), G. Piano, A. Argan, E.
Del Monte, L. Pacciani (INAF/IAPS), M. Cardillo (INAF/OA-Arcetri and
INAF/IAPS), A. Giuliani (INAF/IASF-Mi), M. Pilia, A. Trois
(INAF/OA-Cagliari), F. Longo (Univ. Trieste and INFN Trieste), report on
behalf of the AGILE Team:

We performed an analysis of AGILE data of the GRB 170127C (Fermi/GBM
trigger num 507173752; GCN #20543
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 ), which occurred at 2017-01-27
01:35:47.79 UTC.

The Mini-CALorimeter (MCAL), sensitive in the energy range from 400 keV
to 100 MeV, detected a short burst at T0 = 2017-01-27 01:35:47.9294 UTC,
that triggered both the on-board 16 ms and 64 ms timescale hardware logic
system. The MCAL light curve shows a sharp single peak, that lasted about
0.13 s and released a total number of ~980 counts above 400 keV in the
detector, above an average background rate of 590 counts/s.

The time-integrated spectrum measured between T0 and T0+0.13 s can be fit
in the energy range 0.5 - 20 MeV with a power law with high-energy
cut-off at 1.63 MeV, with photon index -1.64��0.19 and reduced chi-squared
1.08 (18 d.o.f.). As observed by MCAL, the burst fluence in the same
energy range and time interval is 1.20��0.01e-6 erg cm-2. All quoted
errors are at 90% confidence levels.

SuperAGILE, sensitive in the energy range 18 to 60 keV, also clearly
detected the burst with its ratemeters.

E. Moretti (MPP), G. Vianello (Stanford Univ.), E. Bissaldi (INFN and Politecnico Bari), J. Racusin (NASA/GSFC) and M. Axelsson (Stockholm Univ. and KTH Stockholm) report on behalf of the Fermi-LAT team:

On January, 27, 2017 Fermi-LAT detected high-energy emission from GRB 170127C, which was also detected by Fermi-GBM starting at T0 = 01:35:47.79 (trigger 507173752 / 170127067; Bissaldi et al. GCN 20543
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 ).


The best LAT on-ground location is found to be

RA, Dec =  339.3, -63.9 (J2000)

with an error radius of 0.4 deg (90 % containment, statistical error only).

The location was outside the LAT field-of-view at the time of the trigger. The event triggered an autonomous repoint of the spacecraft, causing the location to enter the field-of-view around 300s later.

The data from the Fermi-LAT show a significant increase in the event rate that is spatially correlated with the trigger with high significance.

The highest-energy photon is a 500 MeV event which is observed 2890 seconds after the GBM trigger. A total of 5 photons above 100 MeV were detected up to 4000s after the trigger.

A Swift ToO has been requested for this burst.


The Fermi-LAT point of contact for this burst is Elena Moretti (moretti@mpp.mpg.de<mailto:moretti@mpp.mpg.de>).


The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater
than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and
many scientific institutions across France, Italy, Japan and Sweden.

E. Bissaldi (Politecnico & INFN Bari), B. Mailyan and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:


"At 01:35:47.79 UT on 27 January 2017, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 170127C (trigger 507173752 / 170127067).
The on-ground calculated location, using the GBM trigger data, is

RA, Dec = 336.380, -63.400

(J2000 degrees, equivalent to 22 h 25 m, -63 d 24 '), with an uncertainty
of 1.95 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 trigger resulted in an Autonomous Repoint Request (ARR)
by the GBM Flight Software owing to the high peak flux
of the GRB. This ARR was accepted and the spacecraft slewed to the GBM
in-flight location. The initial angle from the Fermi-LAT boresight
to the GBM ground location is 140 degrees.

The GBM light curve consists of single peak
with a duration (T90) of about 0.210 s (50-300 keV).
The time-averaged spectrum from T0-0.064 s to T0+0.192 s is
well fit by a power law function with an exponential
high-energy cutoff.  The power law index is 0.27 +/- 0.09 and
the cutoff energy, parameterized as Epeak, is 859 +/- 34 keV.

The event fluence (10-1000 keV) in this time interval is
(7.4 +/- 0.2)E-06 erg/cm^2. The 64-ms peak photon flux measured
starting from T0 in the 10-1000 keV band
is 84 +/- 5 ph/s/cm^2.


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