GRB 071001

M. De Pasquale (UCL-MSSL), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), S. Campana (INAF-OAB),
J. R. Cummings (NASA/UMBC), P. A. Evans (U Leicester),
N. Gehrels (NASA/GSFC), C. Gronwall (PSU),
C. Guidorzi (Univ Bicocca&INAF-OAB),
S. T. Holland (CRESST/USRA/GSFC), H. A. Krimm (GSFC/USRA),
V. Mangano (INAF-IASFPA), C. B. Markwardt (CRESST/GSFC/UMD),
F. E. Marshall (NASA/GSFC), A. Moretti (INAF-OAB), C. Pagani (PSU),
K. L. Page (U Leicester), D. M. Palmer (LANL), J. L. Racusin (PSU),
G. Sato (GSFC/ISAS), M. Stamatikos (NASA/ORAU),
R. L. C. Starling (U Leicester), E. Troja (INAF-IASFPA),
T. N. Ukwatta (GSFC/GWU) and L. Vetere (PSU) report on behalf of the
Swift Team:

At 16:31:48 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 071001 (trigger=292826).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 149.766, -59.751 which is 
   RA(J2000) = 09h 59m 04s
   Dec(J2000) = -59d 45' 02"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows two isolated peaks
spanning a duration of about 50 sec.  The peak count rate
was ~1500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

The XRT began observing the field at 16:33:10 UT, 83 seconds after the
BAT trigger. Using prompt downlinked data, we find a bright, variable, 
uncatalogued X-ray source located at RA, Dec 149.7302, -59.7819 which is
   RA(J2000)  = 09h 58m 55.25s
   Dec(J2000) = -59d 46' 54.8"
with an uncertainty of 6.0 arcsec (radius, 90% containment). 
This location is 129 arcseconds from the BAT on-board position,
within the BAT error circle. The initial flux in the 2.5s image
was 1.5e-09 erg/cm2/s (0.2-10 keV). 

The star tracker during the XRT observation has detected and
identified three valid stars, however the attitude solution quality
is worse than normal.  Therefore, there may be some additional 
systematic error in the quoted positions. 

Burst Advocate for this burst is M. De Pasquale (mdp 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.)

D. Bersier (Liverpool JMU), C. Guidorzi (U. Bicocca & INAF-OAB),
R. Smith (Liverpool JMU) report on behalf of a larger collaboration:

We observed the field of GRB 071001 (Swift trigger 292826, GCN 6832
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 )
with the Faulkes Telescope South in BVRi filters.  We do not detect
any variable object within the XRT error circle down to mR=19.5
(calibrated with respect to USNO-B).

We note that a fairly bright object within the XRT error circle may
complicate the analysis.

M. Stamatikos (GSFC/ORAU), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD), D. Palmer (LANL),
A. Parsons (GSFC), M. De Pasquale (UCL-MSSL), T. Sakamoto (GSFC/UMBC),
G. Sato (GSFC/ISAS), J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-119 to T+183 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 071001 (trigger #292826)
(De Pasquale, et al., GCN Circ. 6832
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 ).  The BAT ground-calculated position is
RA, Dec = 149.707, -59.763 deg which is 
   RA(J2000)  =  09h 58m 49.7s 
   Dec(J2000) = -59d 45' 48" 
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 85%.
 
The mask-weighted light curve shows two main peaks: 1) starting/peaking/ending
at ~T-20/0/+30 sec, resp; 2) T+40/+48/+70; and a much weaker (~3 sigma) peak:
~T+70/+90/+100 sec.  T90 (15-350 keV) is 58.5 +- 1.0 sec (estimated error
including systematics).
 
The time-averaged spectrum from T-1.6 to T+64.7 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.62 +- 0.17.  The fluence in the 15-150 keV band is 7.7 +- 0.8 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+48.14 sec in the 15-150 keV band
is 0.9 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

K.L. Page, A.P. Beardmore (U. Leicester) and M. De Pasquale (UCL-MSSL) 
report on behalf of the Swift-XRT team:

We have analysed the two orbits of Swift-XRT data obtained for GRB 071001 
(De Pasquale et al., GCN Circ. 6832
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 ), totalling 37 seconds of Windowed 
Timing (WT) data and 1.3 ks of Photon Counting mode data. Because of a 
temporary problem with the star trackers, we use only the data when the 
attitude can be said to be stable to find a refined position of RA, Dec = 
149.7336, -59.7818, which is equivalent to:

RA(J2000):   09 58 56.07
Dec(J2000): -59 46 54.5

with an estimated uncertainty of 6 arcsec (radius, 90% containment 
including boresight uncertainty). This is 83 arcsec from the 
ground-calculated BAT position (Stamatikos et al., GCN Circ. 6834
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 ) and 6.2 
arcsec from the initial XRT position quoted in GCN Circ. 6832
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 .

The X-ray light-curve shows an initial steep decay, with alpha = 
3.0 +/- 0.2, breaking at about 310 seconds after the trigger to a flatter 
slope of 0.2 +/- 0.1.

The WT spectrum (89-120 seconds after the trigger) can be modelled by a 
power-law of Gamma = 2.2 +0.5/-0.4, absorbed by the Galactic column in 
this direction of 7.6e21 cm^-2. The 0.3-10 keV observed (unabsorbed) flux 
during this time is 4.2e-10 (2.0e-9) erg cm^-2 s^-1.

With only 2 orbits of data, predicting the count rate at 24 hours would 
not lead to an accurate result. No further Swift observations of this 
burst are planned.

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