GRB 131002B

M. C. Stroh (PSU), D. N. Burrows (PSU), V. D'Elia (ASDC),
P. A. Evans (U Leicester), C. Gronwall (PSU), J. A. Kennea (PSU),
P. T. O'Brien (U Leicester), T. Sakamoto (AGU) and M. H. Siegel (PSU)
report on behalf of the Swift Team:

At 10:54:28 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 131002B (trigger=572742).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 75.061, -75.727 which is 
   RA(J2000) = 05h 00m 15s
   Dec(J2000) = -75d 43' 35"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve showed a single peak 
with a duration of about 40 sec.  The peak count rate
was ~1800 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 10:55:21.3 UT, 52.8 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 75.1213, -75.7017 which is equivalent to:
   RA(J2000)  = +05h 00m 29.11s
   Dec(J2000) = -75d 42' 06.1"
with an uncertainty of 5.9 arcseconds (radius, 90% containment). This
location is 105 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. 

The initial flux in the 2.5 s image was 7.25e-10 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White
filter  starting 62 seconds after the BAT trigger. No credible
afterglow candidate has  been found in the initial data products. The
2.7'x2.7' sub-image covers 100% of  the XRT error circle. The typical
3-sigma upper limit has been about 19.6 mag.  The 8'x8' region for the
list of sources generated on-board covers 100% of the  XRT error
circle. The list of sources is typically complete to about 18 mag. No 
correction has been made for the expected extinction corresponding to
E(B-V) of  0.12. 

Burst Advocate for this burst is M. C. Stroh (stroh AT astroh.org). 
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.)

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

Using 923 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 131002B, 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 = 75.12235, -75.70299 which is equivalent
to:

RA (J2000): 05h 00m 29.37s
Dec (J2000): -75d 42' 10.8"

with an uncertainty of 2.2 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.

A. A. Breeveld (UCL-MSSL) and M. C. Stroh (PSU) report on behalf of the 
Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 131002B
62 s after the BAT trigger (Stroh et al., GCN Circ. 15284
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 ).
No optical afterglow consistent with the XRT position (Beardmore et al. 
GCN Circ. 15291
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 ) is detected in the initial UVOT exposures. There is a 
DSS source lying just on the edge of the XRT region at 05:00:29.386 
-75:42:07.58.
Preliminary 3-sigma upper limits using the UVOT photometric system 
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding 
chart (FC) exposure and subsequent exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC            62          212          147         >21.8
white             5216         5416          197         >22.1
v                 5627         5826          197         >20.3
b                 5011         6512          260         >21.4
u                  275         6442          274         >21.0
w1                6037         6237          197         >20.4
m2                5832         6031          197         >20.1
w2                5422         5622          197         >20.5

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.12 in the direction of the 
burst (Schlegel et al. 1998).

M.C. Stroh and B. Sbarufatti report on behalf of the Swift-XRT team:

We have analysed 1.8 ks of XRT data for GRB 131002B,  from 58 s to 6.5
ks after the  BAT trigger. The data comprise 282 s in Windowed Timing
(WT) mode with the remainder in Photon Counting (PC) mode. 

The light curve consists of a relatively flat region of WT data from
T+58 to T+333 s with a count rate ranging between 10 and 50 cts/s. The
WT observation ended when Swift entered the SAA. PC data exists from
T+5.0 to T+6.5 ks with a count rates between 0.1 and 0.04 cts/s. Since
there is only 1.8ks of data on this source, it is difficult to be
confident that a fit to these data points truly models the overall
behavior in this GRB.

A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index	of 1.46 (+0.04, -0.03). The
best-fitting absorption column is  consistent with the Galactic value
of 9.1 x 10^20 cm^-2 (Kalberla et al. 2005). The counts to observed
(unabsorbed) 0.3-10 keV flux conversion factor deduced from this
spectrum  is 4.7 x 10^-11 (5.2 x 10^-11) erg cm^-2 count^-1. 

A summary of the WT-mode spectrum is thus:
Galactic foreground: 9.1 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.46 (+0.04, -0.03)

If the light curve continues to decay with a power-law decay index of
2.05, the count rate at T+24 hours will be 2.0 x 10^-4 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.2 x
10^-15 (1.0 x 10^-14) erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00572742.

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

V. Sudilovsky (MPE Garching), S. Schmidl (TLS Tautenburg) and J.Greiner
(MPE Garching) report on behalf of the GROND team:

We observed the field of GRB 131002B (Swift trigger 572742, Stroh et al.,
GCN 15284
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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/ESO telescope at La Silla
Observatory (Chile).

Observations started on October 03, 2013, at 03:15:17 UT, 16.35 hrs after
the GRB trigger. They were performed at an average seeing of 1".8 and at
an average airmass of 2.0 .

We do not detect any fading source inside the 2".2 XRT error circle
(Beardmore et al., GCN 15291
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 ).
Based on a total exposure time of 1500 s in g'r'i'z' and 1200 s in JHK, at
a midtime of 16.59 hrs after the burst, we estimate the following
preliminary 3-sigma upper limits (all in AB system) of

g' > 24.7 mag,

r' > 24.4 mag,

i' > 23.7 mag,

z' > 23.5 mag,

J > 21.6 mag,

H > 21.0 mag and

K > 20.4 mag.

Given magnitudes are calibrated against GROND zeropoints as well as
2MASS field stars and are not corrected for the expected Galactic
foreground extinction corresponding to a reddening of E_(B-V)=0.12 mag
in the direction of the burst (Schlegel et al. 1998).

G. Sato (ISAS), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (NASA/GSFC/ORAU),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), M. C. Stroh (PSU), J. Tueller (GSFC),
T. N. Ukwatta (MSU), (i.e. the Swift-BAT team):

Using the data set from T-240 to T+418 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 131002B (trigger #572742)
(Stroh, et al., GCN Circ. 15284
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 ).  The BAT ground-calculated position is
RA, Dec = 75.135, -75.701 deg which is
  RA(J2000)  =  05h 00m 32.4s
  Dec(J2000) = -75d 42' 05.2"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a single wide peak that has a main pulse
starts at ~T-6 and ends at ~T+20, and the remaining emission lasts until ~T+42.
T90 (15-350 keV) is 39.10 +- 8.08 sec (estimated error including systematics).

The time-averaged spectrum from T-5.95 to T+41.60 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.36 +- 0.84,
and Epeak of 34.0 +- 4.3 keV (chi squared 62.16 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 6.2 +- 0.6 x 10^-07 erg/cm2
and the 1-sec peak flux measured from T+5.48 sec in the 15-150 keV band is
0.6 +- 0.1 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 2.15 +- 0.14 (chi squared 81.27 for 57 d.o.f.).  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/572742/BA/