GRB 160221A

S.Mereghetti (IASF-Milano), D.Gotz (CEA, Saclay), C.Ferrigno, E.Bozzo, 
T.Favre (ISDC, Versoix), and J.Borkowski (CAMK, Torun) on behalf of the 
IBAS Localization Team report:

a gamma ray burst lasting about 10 s has been detected by IBAS in the 
IBIS/ISGRI data at 23:49:42 UT of February 21, 2016.

The refined coordinates (J2000) are:

R.A.=   232.0818 deg
DEC.=   -28.4337 deg

with an uncertainty of 2.5 arcmin (90% c.l.).

The burst had a peak flux of 1 counts/cm2/s (20-200 keV, 1-s integration 
time) and a fluence in the same energy range of about 5e-7 erg/cmq.

A plot of the light curve will be posted at 
http://ibas.iasf-milano.inaf.it/IBAS_Results.html

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

Swift has initiated a ToO observation of the INTEGRAL GRB 160221A. 
Automated analysis of the XRT data will be presented online at
http://www.swift.ac.uk/ToO_GRBs/00020600

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 INTEGRAL 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.

D.Buckley, S. Potter, M.Kotze, A.Kniazev
South African Astronomical Observatory

E. Gorbovskoy, V. Lipunov, V.Kornilov, D.Kuvshinov, N.Tyurina, 
P.Balanutsa,  A.Kuznetsov
Lomonosov Moscow State University,
Sternberg Astronomical Institute, Moscow State University

A.Gabovich, V.Yurkov, Yu.Sergienko, D.Varda
Blagoveschensk Educational State University, Blagoveschensk

K.Ivanov, N.M.Budnev, O.Gres, V.A.Poleshchuk, S. Yazev
Irkutsk State University

A. Tlatov, V.Senik, A.V. Parhomenko, D. Dormidontov
Kislovodsk Solar Station of the Pulkovo Observatory

R. Rebolo, M. Serra-Ricart, N. Lodieu, G. Israelian
The Instituto de Astrofisica de Canarias


MASTER II  robotic telescope (MASTER-Net: http://observ.pereplet.ru) 
located in SAAO was pointed to the  GRB160221A (Mereghetti et. al GCN 
19046
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 ) 61 sec after notice time and 74 sec after trigger time at 
2016-02-21 23:51:04 UT. On our second (10s exposure)  set we haven`t found 
optical transient  within INTEGRAL error-box (ra=15 28 19 dec=-28 26 40 
r=0.053100).
The 5-sigma upper limit has been about 16.5 mag on single (10 s images) 
and 19.0 on coadd image with total exposure 150 s.

The message may be cited.

A. Melandri (INAF-OAB), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), L.M.
McCauley (PSU), S.L. Gibson (U. Leicester), J.P. Osborne (U.
Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC) and P.A. Evans (U.
Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has performed follow-up observations of the INTEGRAL-detected
burst GRB 160221A (Mereghetti et al. GCN Circ. 19046
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 ), collecting 1.3
ks of Photon Counting (PC) mode data between T0+21.3 ks and T0+25.8 ks.


One uncatalogued X-ray source has been detected inside or close to the
INTEGRAL error region, it is below the RASS limit and shows no
definitive signs of fading. Therefore, at the present time we cannot
confirm this as the afterglow. Details of this source are given below:

Source 1:
  RA (J2000.0):  232.0897  =  15:28:21.54
  Dec (J2000.0): -28.4552  =  -28:27:18.7
  Error: 4.5 arcsec (radius, 90% conf.)
  Count-rate: 0.0151 +/- 0.0040 ct s^-1
  Flux: (5.6 +/- 1.5)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Another uncatalogued was also detected, however this was too far from
the GRB position to be the afterglow.

The results of the XRT-team automatic analysis of the XRT observations,
including a position-specific upper limit calculator, are available at
http://www.swift.ac.uk/ToO_GRBs/00020600.

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

J. Bolmer, T. Kruehler, J. Greiner (all MPE Garching) report on behalf
of the GROND team:

We observed the field of the INTEGRAL GRB 160221A (Mereghetti et al.,
GCN #19046
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 ) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008, PASP 120, 405) mounted at the 2.2m MPG telescope at ESO La Silla
Observatory (Chile).

Observations started at 05:12 UT on 2016-02-22, 5.4 hrs after the GRB
trigger. They were performed at an average seeing of 1.0" and at an
average airmass of 1.4.

No source within the Swift-XRT error circle (Melandri et al.,
GCN #19050
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 ) is detected. Based on 48.0 min of exposure in g'r'i'z'
and 43.3 min in JHK, at a mid-time of 06:43 UT, we derive the
following preliminary upper limits:

g' > 23.6 mag
r' > 24.3 mag
i' > 23.4 mag
z' > 23.4 mag
J  > 21.8 mag
H  > 21.1 mag
K  > 20.0 mag

Given limits are in the AB system and calibrated against GROND
zeropoints as well as 2MASS field stars. No correction for the expected
Galactic foreground extinction corresponding to a reddening of
E_(B-V)=0.26 mag in the direction of the burst (Schlafly &
Finkbeiner 2011) has been applied.

C. M. Hui (NASA/MSFC) and E. Bissaldi (Politecnico & INFN Bari)
report on behalf of the Fermi GBM Team:

"At 23:49:45.22 UT on 21 February 2016, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 160221A (trigger 477791389 / 160221993),
which was also detected by INTEGRAL (Mereghetti et al., GCN 19046
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 ).
The GBM on-ground location is consistent with the INTEGRAL position.

The angle from the Fermi LAT boresight at the GBM trigger time is 58 degrees.

The GBM light curve consists of a single pulse
with a duration (T90) of about 15 s (50-300 keV).
The time-averaged spectrum from T0-1.5 s to T0+5.6 s is
best fit by a power law function with an exponential
high-energy cutoff.  The power law index is -1.15 +/- 0.16 and
the cutoff energy, parameterized as Epeak, is 67 +/- 7 keV.

The event fluence (10-1000 keV) in this time interval is
(1.55 +/- 0.14)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+2.2 s in the 10-1000 keV band
is 4.0 +/- 0.3 ph/s/cm^2.


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

A. Melandri (INAF-OAB), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), L.M.
McCauley (PSU), S.L. Gibson (U. Leicester), J.P. Osborne (U.
Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC) and P.A. Evans (U.
Leicester) report on behalf of the Swift-XRT team:

Swift-XRT has conducted further observations of the field of the
INTEGRAL-detected burst GRB 160221A (Mereghetti et al. GCN Circ.
19046
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 ). The observations now extend from T0+21.3 ks to T0+274.5 ks. The
source previously reported by Melandri et al. (GCN Circ. 19050
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 ),
"Source 1", is fading with 3-sigma significance, and is therefore
likely the GRB afterglow.  The position of this source is RA,
Dec=232.0895, -28.4551 which is equivalent to:

RA (J2000): 15:28:21.48
Dec(J2000): -28:27:18.4

with an uncertainty of 4.1 arcsec (radius, 90% confidence).  This
position is 80 arcsec from the INTEGRAL position.  The source is fading
with alpha >0.5.

The results of the XRT-team automatic analysis of the likely afterglow
are at http://www.swift.ac.uk/ToO_GRBs/00020600/index_1.php.
The results of the full analysis of the XRT observations are available
at http://www.swift.ac.uk/ToO_GRBs/00020600.

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