GRB 110102A

S. R. Oates (UCL-MSSL), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), D. N. Burrows (PSU), V. D'Elia (ASDC),
N. Gehrels (NASA/GSFC), J. M. Gelbord (PSU), C. Gronwall (PSU),
C. Guidorzi (U Ferrara), S. T. Holland (CRESST/USRA/GSFC),
V. Mangano (INAF-IASFPA), C. B. Markwardt (NASA/GSFC),
K. L. Page (U Leicester), D. M. Palmer (LANL),
C. J. Saxton (UCL-MSSL), B. Sbarufatti (INAF-OAB/IASFPA),
M. H. Siegel (PSU) and G. Stratta (ASDC) report on behalf of the Swift
Team:

At 18:52:25 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 110102A (trigger=441454).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 245.879, +7.619 which is 
   RA(J2000)  =  16h 23m 31s
   Dec(J2000) = +07d 37' 09"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a weak precursor at T_zero
and then a bright FRED-like pulse at T+130 sec with a total duration
of about 170 sec.  The peak count rate was ~6000 counts/sec (15-350 keV),
at ~130 sec after the trigger. 

The XRT began observing the field at 18:54:54.0 UT, 148.6 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 245.8821, +7.6160 which is equivalent to:
   RA(J2000)  = 16h 23m 31.70s
   Dec(J2000) = +07d 36' 57.5"
with an uncertainty of 6.3 arcseconds (radius, 90% containment). This
location is 15 arcseconds from the BAT onboard position, within the BAT
error circle. No event data are yet available to determine the column
density using X-ray spectroscopy. 

UVOT took a finding chart exposure of 150 seconds with the White filter
starting 149 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
  RA(J2000)  =	16:23:31.43 = 245.88096
  DEC(J2000) = +07:36:50.0  =	7.61390
with a 90%-confidence error radius of about 0.62 arc sec. This position is 8.6
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.93 with a 1-sigma error of about  0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.08. 

Burst Advocate for this burst is S. R. Oates (sro AT mssl.ucl.ac.uk). 
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/too.html.)

M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) 
report on behalf of the Swift-XRT team.

Using 3361 s of XRT Photon Counting mode data and 7 UVOT
images for GRB 110102A, we find an astrometrically corrected X-ray
position (using the XRT-UVOT alignment and matching UVOT field sources
to the USNO-B1 catalogue): RA, Dec = 245.88117, +7.61377 which is equivalent
to:

RA (J2000): 16h 23m 31.48s
Dec (J2000): +07d 36' 49.6"

with an uncertainty of 1.7 arcsec (radius, 90% confidence).

This position may be improved as more data are received. The latest
position can be viewed at http://www.swift.ac.uk/xrt_positions. Position
enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans
et al. (2009, MNRAS, 397, 1177).

This circular was automatically generated, and is an official product of the
Swift-XRT team.

T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
C. B. Markwardt (GSFC), S. R. Oates (UCL-MSSL), D. M. Palmer (LANL),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 110102A (trigger #441454)
(Oates, et al., GCN Circ. 11509
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 ).  The BAT ground-calculated position is
RA, Dec = 245.877, 7.617 deg, which is
   RA(J2000)  =  16h 23m 30.5s 
   Dec(J2000) = +07d 37' 00.1" 
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 66%.
 
The mask-weighted light curve shows a pair of small precursor peaks starting
at ~T-50 sec and ending at ~T+50 sec.  The main emission occurs with four peaks
that start at ~T+100 sec and ending at ~T+340 with the maximum at ~T+210 sec.
T90 (15-350 keV) is 264 +- 8 sec (estimated error including systematics).
 
The time-averaged spectrum from T-49.2 to T+294.9 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.60 +- 0.04.  The fluence in the 15-150 keV band is 1.65 +- 0.03 x 10^-5 erg/cm2.
The 1-sec peak photon flux measured from T+208.76 sec in the 15-150 keV band
is 8.4 +- 0.3 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/441454/BA/

Lin Lin (UAH) 
report on behalf of the Fermi GBM Team: 

"At 18:54:36.00 UT on 2 Jan. 2011, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 110102A (trigger 315687278 / 110102788).
which was also detected by the Swift/BAT
(S. R. Oates et al. 2011, GCN 11509
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 )
The GBM on-ground location is consistent with the Swift position.


The GBM light curve shows of several peaks 
with a duration (T90) of about 254 s (50-300 keV). 
The T90 starts at T0-119 s.
The time-averaged spectrum from T0-123 s to T0+149 s is 
well fit by

a power law function with an exponential
high-energy cutoff.  The power law index is -1.49 +/- 0.02 and
the cutoff energy, parameterized as Epeak, is 476.6 +/- 68.7 keV

The event fluence (10-1000 keV) in this time interval is 
(4.39 +/- 0.09)E-5 erg/cm^2. The 1 sec peak photon flux measured 
starting from T0+78 s in the 10-1000 keV band 
is 14.07 +/- 0.35 ph/s/cm^2.

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

D. Kuroda, K. Yanagisawa, Y. Shimizu, H. Toda (OAO, NAOJ),
S. Nagayama (NAOJ), M. Yoshida (Hiroshima), K. Ohta (Kyoto)
and N. Kawai(Tokyo Tech)
report on behalf of the MITSuME collaboration:

We observed the field of GRB 110102A (Oates et al., GCN 11509
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 )
with the optical three color (g', Rc and Ic) CCD camera attached
to the MITSuME 50cm telescope of Okayama Astrophysical Observatory.
The observation started on 2011-01-02 20:08:45 UT (~1.3 hours after
the burst).  We detected the afterglow candidate within the
enhanced XRT error circle (Goad et al., GCNC 11510) in all the three
bands.

Photometric results are listed below. We used SDSS catalog for flux
calibration.

#T0+[day]  MID-UT    T-EXP[sec]   g'  g'_err   Rc  Rc_err   Ic  Ic_err
----------------------------------------------------------------------
0.06851    20:31:04  2340.0      20.0  0.4    19.6  0.3    18.3  0.2
----------------------------------------------------------------------
T0+ : Elapsed time after the burst [day]
T-EXP: Total Exposure time [sec]

S. R. Oates (MSSL-UCL) and M. De Pasquale (MSSL-UCL) report on behalf  
of the Swift-UVOT team

The Swift/UVOT began settled observations of the field of GRB 110102A
156 s after the BAT trigger (Oates et al., GCN Circ. 11509
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 ). The optical
afterglow is detected in the white, v, b and u filters at a refined UVO
position RA(J2000)= 245.88087 deg, DEC(J2000) = 7.61383, which is:

  RA (J2000) =   16:23:31.41
  Dec (J2000) = +07:36:49.8

with an estimated uncertainty of 0.5 arcsec (radius, 90% confidence).
This position is consistent with the enhanced XRT position (Goad et  
al., GCN Circ. 11510
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 ).
The detection in u suggests a redshift of <2.5.

Preliminary magnitudes using the UVOT photometric system (Poole et al.  
2008,
MNRAS, 383, 627) for single and summed exposures are:

Filter  T_start(s)  T_stop(s)   Exp(s)       Mag/3sigUL
#####################################################
wh (FC) 156          306        147       17.97 +/- 0.06
wh          868          1018      147       18.39 +/- 0.08
u  (FC)   314          564        246       17.98 +/- 0.09
u             1122       1315      39          18.89 +/- 0.62
v             816          835        19          17.86 +/- 0.53
b             597          589        19          17.60 +/- 0.20
uvw1      693         6331      452        > 20.09
uvm2      668         6126      292        > 19.87
uvw2      619         7152      471        > 20.35
#####################################################

The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.08 in the direction of the burst
(Schlegel et al. 1998).

S. Golenetskii, R.Aptekar, D. Frederiks, E. Mazets, V. Pal'shin,
P. Oleynik, M. Ulanov, D. Svinkin, and T. Cline on behalf
of the Konus-Wind team, report:

The long GRB 110102A, (Swift/BAT trigger=441454:
Oates, et al., GCN 11509
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 ; Sakamoto et.al, GCN 11511
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 )
triggered Konus-Wind at T0=68074.462s UT (18:54:34.462)

The burst light curve consists of three major pulses,
first two of them are much harder than the third one.
The total duration of the burst is ~160 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/GRB110102_T68074/

As observed by Konus-Wind the burst
had a fluence of (5.4 � 0.9)x10-5 erg/cm2,
and a 256-ms peak flux, measured from T0+76.032s,
of (4.9 � 0.8)x10-6 erg/cm2/s
(both in the 20 keV - 5 MeV energy range).

The time-integrated spectrum of the burst
(from T0 to T0+164.096 s) is best fit
in the 20 keV - 5 MeV range by the GRB (Band)
model, for which:
the low-energy photon index alpha = -1.22 (-0.16, +0.26),
the high energy photon index beta = -2.3 (< -0.9),
the peak energy Ep = 267(-91, +111) keV,
chi2 = 65/76 dof.

The spectrum at the maximum count rate
(measured from T0+73.984 to T0+82.176 s) is best fit
in the 20 keV - 5 MeV range by the GRB (Band)
model, for which:
the low-energy photon index alpha = -1.14 (-0.12, +0.15),
the high energy photon index beta = -2.2 (-3.1, +0.3),
the peak energy Ep = 436(-122, +180) keV,
chi2 = 57/76 dof.

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

V. D'Elia, G. Stratta (ASDC) and S. R. Oates (MSSL-UCL) report on behalf
of the Swift-XRT team:

We have analysed 18.8 ks of XRT data for GRB 110102A (Oates et
al., GCN Circ. 11509
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 ), from 139 s to 47.5 ks after the  BAT trigger.
The data comprise 400 s in Windowed Timing (WT) mode with the
remainder in Photon Counting (PC) mode. The enhanced XRT position for
this burst was given by Goad et al. (GCN. Circ 11510).

The light curve shows an intital flaring activity, possibly associated
to the prompt event, followed by a canonical steep-flat-steep
behaviour, which can be modelled with double broken power-law
decay. The initial decay index is alpha= 8.6. At T+450 (+/- 0.05) s the
decay flattens to an alpha of 0.49 (+/-0.03). At T+11.38 (+/- 0.01) ks  
the decay steepens again to an alpha of 1.53 (+0.07 -0.09).

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.48 (+/-0.04). The
best-fitting absorption column is  7.8 (+/- 1) x 10^20 cm^-2, in
excess of the Galactic value of 4.8 x 10^20 cm^-2 (Kalberla et al.
2005). The PC mode spectrum has a photon index of 2.27 (+/-0.07) and a
best-fitting absorption column of 1.28 (+/- 0.17) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum  is 3.6 x 10^-11 (5.8 x 10^-11) erg cm^-2 count^-1.

If the light curve continues to decay with a power-law decay index of 1.6,
the count rate at T+48 hours will be 0.012 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of
4.3 x 10^-13 (7.0 x 10^-13) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00441454.

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

[GCN OPS NOTE(04jan11):  Per author's request, the "4.3 x 10^-12 (2.1 x 10^-13)"
in the 4th paragraph was changed to "4.3 x 10^-13 (7.0 x 10^-13)".]