GRB 160206A

K. Furuya (Miyazaki U.) , Nakahira, M.(JAXA), M. Nakajima (Nihon U.), M. Serino (RIKEN),
S. Ueno, H. Tomida, S. Nakahira, M. Ishikawa, Y. E. Nakagawa (JAXA),
T. Mihara, M. Sugizaki, M. Shidatsu, J. Sugimoto, T. Takagi, M. Matsuoka (RIKEN), 
N. Kawai, M. Arimoto, T. Yoshii, Y. Tachibana, Y. Ono, T. Fujiwara (Tokyo Tech),
A. Yoshida, T. Sakamoto, H. Ohtsuki Y. Kawakubo (AGU),
H. Tsunemi, R. Imatani (Osaka U.),
H. Negoro (Nihon U.), K. Tanaka, T. Masumitsu (Nihon U.),
Y. Ueda, T. Kawamuro, T. Hori, A. Tanimoto (Kyoto U.),
Y. Tsuboi, S. Kanetou, Y. Nakamura, R. Sasaki (Chuo U.),
M. Yamauchi, D. Itoh, (Miyazaki U.)
K. Yamaoka (Nagoya U.),
M. Morii (ISM)
report on behalf of the MAXI team:

The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient 
source at 02:52:43 UT on on 2016 Feburary 6.
Assuming that the source flux was constant over the transit,
we obtain the source position at
(R.A., Dec) = (132.696 deg, -36.099 deg) = (08 50 47, -36 05 56) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.33 deg and 0.3 deg, respectively.
The roll angle of long axis from the north direction is 23.0 deg counterclockwise.
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 125 +- 26 mCrab
(4-10keV, 1 sigma error).
Without assumptions on the source constancy,we obtain a rectangular error
box for the transient source with the following corners:
(R.A., Dec) = (132.055 deg, -35.576 deg) = (08 48 13, -35 34 32) (J2000)
(R.A., Dec) = (132.787 deg, -35.291 deg) = (08 51 08, -35 17 28) (J2000)
(R.A., Dec) = (133.399 deg, -36.778 deg) = (08 53 35, -36 46 40) (J2000)
(R.A., Dec) = (132.642 deg, -37.044 deg) = (08 50 34, -37 02 39) (J2000)
There was no significant excess flux in the previous transit at UT 01:20
and in the next transit at 04:25 UT with an upper limit of 20 mCrab for each.

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
MAXI GRB 160206A. Automated analysis of the XRT data will
be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00053

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 MAXI 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.

K.L. Page (U. Leicester), V. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A.
Maselli  (INAF-IASFPA), L.M. McCauley (PSU), J.A. Kennea (PSU), B.
Sbarufatti (INAF-OAB/PSU), C. Pagani (U. Leicester), A.P. Beardmore (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 MAXI-detected
burst GRB 160206A (Furuya et al. GCN Circ. 18993
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 ) in a series of
observations tiled on the sky. The total exposure time is 3.7 ks,
distributed over 4 tiles; the maximum exposure at a single sky location
was 1.6 ks. The data were collected between T0+46.2 ks and T0+53.5 ks,
and are entirely in Photon Counting (PC) mode. 

Two uncatalogued X-ray sources have been detected, however none of them
is above the RASS limit or shows definitive signs of fading. Therefore,
at the present time we cannot identify which, if any, is the afterglow.
Details of these sources are given below:

Source 1:
  RA (J2000.0):  132.7319  =  08:50:55.65
  Dec (J2000.0): -36.3302  =  -36:19:48.5
  Error: 4.1 arcsec (radius, 90% conf.)
  Count-rate: 0.0262 +/- 0.0060 ct s^-1
  Flux: (5.8 +/- 1.3)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

Source 2:
  RA (J2000.0):  132.5583  =  08:50:13.98
  Dec (J2000.0): -36.0137  =  -36:00:49.5
  Error: 5.8 arcsec (radius, 90% conf.)
  Count-rate: (5.2 +/- 2.4)e-3 ct s^-1
  Flux: (1.04 +/- 0.49)e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)

The results of the XRT-team automatic analysis of the tiled XRT
observations, including a position-specific upper limit calculator, are
available at http://www.swift.ac.uk/xrt_products/TILED_GRB00053.

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

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

We observed the field of GRB 160206A (Furuya et al., GCN #18993
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 )
simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120,
405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory
(Chile).

Observations centered on XRT source #2 (Page et al. 2016, GCN #18996
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 )
started at 00:40 UT on 2016-02-07, 22.3 hrs after the GRB trigger. They
were performed at an average seeing of 1.5" and at an average airmass of
1.4.

We detect no source brighter than the Digitized Sky Survey limiting
magnitudes in the 5.8" Swift-XRT error circle. There is one fainter source
(r'~22.6 AB mag) at RA(2000.0) = 08:50:14.1, Decl.(2000.0) = -36:00:52,
but no statement about variability  can be made at this stage.

M. De Pasquale (PSU) and A. Melandri (INAF-OAB)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began observing the field of MAXI-detected GRB
160206A (Furuya et al., GCN Circ. 18993
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 ) 46.2 ks after the trigger.

No optical afterglow consistent with the XRT source 2 given by Page
et al. (GCN Circ. 18996
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 ) is detected in the UVOT exposures.

Preliminary 3-sigma upper limit using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the summed UVOT
exposures is:

Filter         T_start(s)   T_stop(s)      Exp(s)    3sigma UL Mag

u                48081        52769         909           21


Source 1 is found to be consistent with the magnitude 12.3 object
TyC 7149 2271-1.

These magnitudes are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.47 in the direction of the burst
(Schlegel et al. 1998).

[GCN OPS NOTE(08feb16): Per author's request, "XRT source 1"
was changed to "XRT source 2", and "Source 2 is" was changed
to "Source 1 is".]

Tomoki Morokuma (The University of Tokyo), Nozomu Tominaga (Konan
University), Masaomi Tanaka (National Astronomical Observatory of
Japan), Akihiro Suzuki (Kyoto University), Motoko Serino (RIKEN),
Takanori Sakamoto (Aoyama Gakuin University), and Keiichi Maeda (Kyoto
University) report:

We took r-band images for the field of GRB 160206A (Furuya et al. 2016,
GCN Circ. 18993
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 ) 10.5 hours after the trigger with the Kiso Wide Field
Camera (KWFC; Sako et al. 2012, SPIE, 8446, 84466L) on the 1.05-m Kiso
Schmidt telescope in Japan. Our data were taken in a very low elevation
(10-15 degrees) and the detection limits were 17.0 mag (S/N=5, without
the Galactic extinction correction). No optical afterglow is detected at
the position of Swift XRT source 2 (Page et al. 2016, GCN Circ. 18996
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 )
in any of our ten 180-sec exposures. The Swift XRT source 1 (TYC
7149-2271-1) is saturated in all the images and it is difficult to
evaluate its time variability.

Starting times (UT) of the exposures are summarized as below.

 date(UT)    time  t_exp[s]
2016-02-06 13:27:19 180
2016-02-06 13:32:51 180
2016-02-06 13:38:17 180
2016-02-06 13:43:43 180
2016-02-06 13:49:06 180
2016-02-06 13:54:36 180
2016-02-06 14:00:01 180
2016-02-06 14:05:26 180
2016-02-06 14:10:50 180
2016-02-06 14:16:17 180