GRB 180210A

E. Bissaldi (Politecnico & INFN Bari)
reports on behalf of the Fermi GBM Team:


"At 12:24:38.55 UT on 10 February 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180210A (trigger 539958283 / 180210517).
The on-ground calculated location, using the GBM trigger data, is

RA = 3.33, DEC = 21.01 (J2000 degrees),

with an uncertainty of 1.5 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 31 degrees.

The GBM light curve consists of a multi-peaked
emission episode with a duration (T90) of about 40 s (50-300 keV).
The time-averaged spectrum from T0 to T0+31 s is best fit by
a Band function with Epeak = 145 +/- 3 keV,
alpha = -0.45 +/- 0.02, and beta = -2.60 +/- 0.06.

The event fluence (10-1000 keV) in this time interval is
(4.21 +/- 0.04)E-05 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+24 s in the 10-1000 keV band
is 16.7 +/- 0.3 ph/s/cm^2.


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

F. Dirirsa (U. Johannesburg) and E. Bissaldi (Politecnico & INFN Bari)
report on behalf of the Fermi-LAT team:


"At 12:24:38.55 UT on February 10, 2018 Fermi-LAT detected
high-energy emission from GRB 180210A, which was also
detected by Fermi-GBM (trigger 539958283/180210517)
(E. Bissaldi, GCN 22407
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 ).

The best LAT on-ground location is found to be

RA, Dec = 1.80, 18.35 (J2000 deg)

with an error radius of 0.18 deg (90 % containment, statistical error only).
This was 30 deg from the LAT boresight at the time of the trigger
and triggered an autonomous repoint of the spacecraft.

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 4 GeV event
which is observed 363 seconds after the GBM trigger.

A Swift ToO has been approved for this burst.

The Fermi-LAT point of contact for this burst is
Feraol F. Dirirsa (fdirirsa@uj.ac.za).


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."

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

Swift has initiated a ToO observation of the Fermi/LAT GRB 180210A. 
Automated analysis of the XRT data will be presented online at
http://www.swift.ac.uk/ToO_GRBs/00020787

Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Fermi/LAT event. 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.

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 180210A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00069

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.

A.P. Beardmore (U. Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA),
A. Melandri (INAF-OAB), S. J. LaPorte (PSU), J.A. Kennea (PSU), B.
Sbarufatti (INAF-OAB/PSU), S.L. Gibson (U. Leicester) and P.A. Evans
(U. Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the
Fermi/LAT-detected burst GRB 180210A (Dirirsa et al. GCN Circ. 22408
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 ),
collecting 7.5 ks of Photon Counting (PC) mode data between T0+31.0 ks
and T0+117.4 ks. 

Four uncatalogued X-ray sources are detected, of which one ("Source 1",
the brightest) is fading with 3-sigma significance, and is therefore
likely the GRB afterglow. Using 4922 s of PC mode data and 4 UVOT
images, we find an enhanced XRT position (using the XRT-UVOT alignment
and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec =
1.84177, +18.55274 which is equivalent to:

RA (J2000): 00h 07m 22.02s
Dec(J2000): +18d 33' 09.9"

with an uncertainty of 1.7 arcsec (radius, 90% confidence). This
position is 12.4 arcmin from the Fermi/LAT position. 

The light curve can be modelled with a power-law decay with a decay
index of alpha=1.57 (+0.36, -0.28).

A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.3 (+/-0.4). The
best-fitting absorption column is  3.6 (+1.7, -1.4) x 10^21 cm^-2, in
excess of the Galactic value of 3.7 x 10^20 cm^-2 (Willingale et al.
2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum  is 2.7 x 10^-11 (5.0 x 10^-11) erg
cm^-2 count^-1. 

A summary of the PC-mode spectrum is thus:
Total column:	     3.6 (+1.7, -1.4) x 10^21 cm^-2
Galactic foreground: 3.7 x 10^20 cm^-2
Excess significance: 3.7 sigma
Photon index:	     2.3 (+/-0.4)

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00020787.
The results of the full analysis of the XRT observations are available
at http://www.swift.ac.uk/ToO_GRBs/00020787.

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

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 180210A
(Fermi-GBM detection: Bissaldi, GCN Circ. 22407
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 ;
Fermi-LAT detection: Dirirsa and Bissaldi, GCN Circ. 22407
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 )
triggered Konus-Wind at T0=44678.454 s UT (12:24:38.454).

The burst light curve shows a multipeaked structure
which starts at ~T0-6 s and has a total duration of ~65 s.
The emission is seen up to ~5 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180210_T44678/

As observed by Konus-Wind, the burst
had a fluence of 4.81(-0.30,+0.36)x10^-5 erg/cm2,
and a 64-ms peak flux, measured from T0+20.224 s,
of 5.35(-1.07,+1.10)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+47.360 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.49(-0.13,+0.15),
the high energy photon index beta = -3.12(-0.54,+0.30),
the peak energy Ep = 153(-8,+8) keV
(chi2 = 84/97 dof).

The spectrum near the maximum count rate
(measured from T0+16.128 to T0+22.784 s)
is best fit in the 20 keV - 10 MeV range
by the GRB (Band) model with the following parameters:
the low-energy photon index alpha = -0.08(-0.24,+0.27),
the high energy photon index beta = -3.25(-1.02,+0.37),
the peak energy Ep = 152(-11,+12) keV
(chi2 = 106/91 dof).

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

X. F. Lu, J. Y. Liao, C. K. Li, Y. Huang, Y. Zhu, S. L. Xiong, X. B. Li,
C. Z. Liu, Z. W. Li, J. L. Zhao, Y. F. Zhang, X.F. Li, Z. Chang, Y. J. Jin, 
C. L. Zou (IHEP), A. M. Zhang, Z. Zhang (THU), T. P. Li (IHEP/THU),
F. J. Lu, L. M. Song, H. Y. Wang, M. Wu, Y. P. Xu, S. N. Zhang (IHEP),
report on behalf of the Insight-HXMT team:
 
At 2018-02-10T12:24:38.55 UT, the Insight-HXMT/HE detected
GRB 180210A(trigger ID: HEB180210517) in a routine search of the data,
which was also triggered by Fermi/GBM(GCN Circ. 22407
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 ),Fermi/LAT(GCN Circ. 22408
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 ), 
Swift/XRT(GCN Circ. 22413
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 ) and KONUS-Wind(GCN Circ. 22415
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 ).
 
The Insight-HXMT/HE light curve consists of a multi-peaked pulse
with a duration (T90) of 26.7 s measured from T0+3.9 s.
The 1-s peak rate, measured from T0+23.9 s, is 3173.8 cnts/sec.
The total counts from this burst is 40447.9 counts.

URL_LC: http://www.hxmt.org/images/GRB/HEB180210517_lc.jpg
 
All measurements above are made with the CsI detectors operating in the
regular mode with the energy range of about 80-800 keV (record energy).
Only gamma-rays with energy greater than about 200 keV can penetrate
the spacecraft and leave signals in the CsI detectors installed inside
of the telescope.

The time-averaged spectrum from T0-8 to T0+30 s is adequately fit by a Power
Law model with spectral index = -1.86 +/- 0.03. The energy fluence is 
(4.5 +/- 0.2) E-05 erg/cm^2 in 200 - 5000 keV in this time interval.
 
The analysis results presented above are preliminary, 
final results will be published elsewhere.
 
Insight-HXMT is the first Chinese space X-ray telescope, which was funded
jointly by the China National Space Administration (CNSA) and the Chinese
Academy of Sciences (CAS). More information about it could be found at:
http://www.hxmt.org/index.php/enhome.

[GCN OPS NOTE(26feb18): "2018-02-10T17:29:06.000" was changed to "2018-02-10T12:24:38.55"
and "HEB180210728" was changed to "HEB180210517".]