GRB 071101

S. McBreen (MPE), S. D. Barthelmy (GSFC), J. R. Cummings (NASA/UMBC),
N. Gehrels (NASA/GSFC), O. Godet (U Leicester),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
H. A. Krimm (GSFC/USRA), F. E. Marshall (NASA/GSFC),
P. T. O'Brien (U Leicester), C. Pagani (PSU),
K. L. Page (U Leicester), D. M. Palmer (LANL), A. M. Parsons (GSFC),
P. Romano (Univ. Bicocca & INAF-OAB), T. Sakamoto (NASA/UMBC),
M. Stamatikos (NASA/ORAU), R. L. C. Starling (U Leicester),
E. Troja (INAF-IASFPA), T. N. Ukwatta (GSFC/GWU),
D. E. Vanden Berk (PSU) and S. D. Vergani (DIAS-DCU) report on behalf
of the Swift Team:

At 17:53:46 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 071101 (trigger=295779).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 48.194, +62.473 which is 
   RA(J2000)  =  03h 12m 46s
   Dec(J2000) = +62d 28' 24"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a single peak
with a duration of about 3 sec.  The peak count rate
was ~1000 counts/sec (15-350 keV), at ~1 sec after the trigger. 

The XRT began taking data at 17:58:29 UT, 283 seconds after the BAT
trigger.  The XRT on-board centroid algorithm did not find a source in the
image and no prompt position is available.  We are waiting for down-linked
data to detect and determine a position for the source. 


UVOT took a finding chart exposure of 100 seconds with the White (160-650 nm)
filter starting 82 seconds after the BAT trigger. No afterglow candidate has
been found in the initial data products. The 2.7'x2.7' sub-image covers 25% of
the BAT error circle. The typical 3-sigma upper limit has been about 18.5 mag. 
The 8'x8' region for the list of sources generated on-board covers 100% of the
BAT error circle. The list of sources is typically complete to about 18 mag. No
correction has been made for the large, but uncertain extinction expected. 

Burst Advocate for this burst is S. McBreen (smcbreen AT mpe.mpg.de). 
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.)

E. Ofek (Caltech) reports:

I note the presence of a 2MASS-cataloged galaxy, 2MASX J03124721+6231391,
just outside the BAT localization region for the short-duration burst
GRB 071101 (McBreen et al. 2007; GCN 7030
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 ).
The galaxy is located 3.3 arcmin. from the nominal BAT localization.
By analyzing all the Swift BAT and XRT observed GRB positions,
I find that the probability that the BAT localization is off by
more than 3.3 arcmin is about 3%.
The galaxy J2000.0 position is: 03:12:47.2 +62:31:39, and it
has a total K-band magnitude of 11.4.

This research has made use of the NASA/IPAC Extragalactic Database
(NED) which is operated by the Jet Propulsion Laboratory, California
Institute of Technology, under contract with the National Aeronautics
and Space Administration.

Martin Jelínek, Petr Kubánek, Stanislav Vítek, 
Alberto J. Castro-Tirado (IAA-CSIC Granada) and 
Lola Sabau-Graziati (INTA Madrid), 
on behalf of the BOOTES collaboration,

report:

"The robotic telescope BOOTES-2 located at Experimental
Station La Mayora (EELM-CSIC) in southern Spain
followed automatically the Swift GRB 071101 (McBreen et
al, GCN 7030
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 ). Images were taken starting 56s after the
GRB (23.5s after the GCN notice).

We do not detect any new source within the BAT errorbox
down to our unfiltered, USNO-A2 calibrated magnitude of
17.0 in out 180s exposure.

Note the high extinction in the line of sight
E(B-V)=1.43697 => (Ar=3.43).

In particular, we do not see any object at the position
of the galaxy mentioned by Ofek (GCN 7031
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 )."

I. Lee, M. Im (Seoul National University), and 
Y. Urata (Saitama U/ASIAA) on behalf of the EAFON team:

"Using the Mt. Lemmon (Arizona, US) 1.0m telescope operated by the
Korea Astronomy and Space Science Institute, we have imaged the
GRB071101 field (McBreen et al. GCN7030
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 ). The observation started at
UT 01:59 on Nov 02 (8 hours after the GRB).  These images obtained in
B,V,R,I with 300 sec exposure show no new source.  The upper limit
derived from USNO-B1.0 stars is 21th mag in R-band."

This message may be cited.

We acknowledge the help of the LOAO operators, J.H. Yoon, for this
observation.

C. Pagani (PSU) reports on behalf of the Swift-XRT team:

Swift XRT observed the GRB 071101 (trigger=295779, McBreen et al., GCN Circ.
7030
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 ) beginning 85 s after the BAT trigger.
In the first 13 ks of Photon Counting mode data a faint X-ray source is detected
at the position RA,Dec = 48.1772, +62.5002 deg, equivalent to:

RA(J2000) =  03h 12m 42.53s
Dec(J2000)= +62d 30' 00.7"

with an error of radius 7 arcseconds (90%, including boresight uncertainties).
This is 102 arcseconds from the BAT position (GCN Circ. 7030
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 ) and 103
arcseconds from the 2MASS-cataloged galaxy, 2MASX J03124721+6231391 reported by
Ofek (GCN Circ. 7031
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 ).

Further analysis will be reported in a subsequent circular.

Klotz, A. (CESR-OMP), Boer M. (OHP), Atteia J.L. (LATT-OMP) report:

We imaged the field of GRB 071101 detected by SWIFT
(trigger 295779) with the TAROT robotic telescope (D=25cm)
located at the Calern observatory, France.

The observations started 39.4s after the GRB trigger
(7.1s after the notice). The elevation of the field increased from
from 36 degrees above horizon and weather conditions
were good. Images were acquired with no filter.

The date of trigger : t0 = 2007-11-01T17:53:46.752

The first image is trailed with a duration of 60.0s
(see the description in Klotz et al., 2006, A&A 451, L39).
We do not detect any OT at the XRT location defined
by Pagani et al. GCN Circ. 7034
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 ) with a limiting magnitude of:
t0+39.4s to t0+99.4s : R > 16.3

The second image is 30.0s exposure in tracking mode:
t0+106.4s to t0+136.4s : R > 17.5

We co-added a series of exposures:
t0+106.4s to t0+393.6s : R > 18.4

Magnitudes were estimated with the nearby USNO-B1 stars
and are not corrected for galactic dust extinction.

N.B. Galactic coordinates are lon=138.4726 lat= +3.9459
and the galactic extinction in R band is about 4.0 magnitudes
estimated from D. Schlegel et al. 1998ApJ...500..525S.

This message may be cited.

M. Uemura, A. Arai, and T. Uehara (Hiroshima Univ.), report 
on behalf of the KANATA GRB team:

  We performed optical-NIR observations of the field of 
GRB 071101 (GCN Circ. 7030
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 ) with TRISPEC attached to 
the "KANATA" 1.5-m telescope.  
Our images cover about 70% of the south region of the BAT errorbox, 
in which the nearby galaxy reported in GCN Circ. 7031
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  is not 
included and the region of the XRT error circle (GCN Circ. 7034
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 ) 
is included.

  No fading source or afterglow candidate can significantly 
be detected in the XRT error circle. 
Upper limits of magnitude were estimated from neighbor 
USNO B1.0 stars and 2MASS sources, shown below:

time(UT)     time after the burst  lim. mag. exposure_time
1 Nov. 2007      (sec)                          (sec)
 
17:57:36          229              19.7(V)        30
17:57:33          226              17.0(J)        24
17:57:27          220              14.8(Ks)       12
18:16:25         1358              20.8(V)       123
18:16:24         1357              18.0(J)       120
18:16:16         1349              15.5(Ks)      108

O. Godet, K.L. Page, A.P.  Beardmore,  J.P. Osborne (U. Leicester),
S. McBreen (MPE) on behalf of the Swift-XRT team:

We analysed 15.5ks of Photon Counting data for GRB 071101 (McBreen et
al. GCN Circ. 7030
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 ).  Using Swift-XRT PC data, Pagani (GCN Circ. 7034
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 )
reported a faint X-ray source in the BAT error circle.

The X-ray light-curve for this source can be fitted by a power-law from
T+85s to T+4.1e4s, with an initial decay index of 0.9 � 0.3. So, this
source is the X-ray afterglow of GRB 071101.

The Photon Counting spectrum can modelled as an absorbed power-law, with
Gamma = 2.9 +2.5/-1.7 and a total absorbing column of NH = (2.0
+2.8/-1.6)e22 cm-2. The Galactic value is 5.7e21 cm-2 in the direction
of the burst. The 1-10 keV observed (unabsorbed) flux during this time
is 1.4e-13(3.2e-13) erg cm-2 s-1.

Assuming the source continues to decay with the same decay index of 0.9,
we predict an XRT count rate of 6.4e-4 counts/s at T+24 hours, which
corresponds to an observed 1-10keV flux of 6.8E-14 ergs cm-2 s-1.

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

T. Ukwatta (GWU) S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC),
E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), S. McBreen (MPE), D. Palmer (LANL),
T. Sakamoto (GSFC/UMBC), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC),
(i.e. the Swift-BAT team):
 
Using the data set from T-240 to T+962 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 071101 (trigger #295779)
(McBreen, et al., GCN Circ. 7030
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 ).  The BAT ground-calculated position is
RA, Dec = 48.179, 62.524 deg, which is 
   RA(J2000)  = 03h 12m 42.9s 
   Dec(J2000) = 62d 31' 27" 
with an uncertainty of 2.7 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 99%.
 
The mask-weighted light curve shows a single peak starting at a low level
at ~T-20, then spiking at T+1 sec, and ending at ~T+10 sec.
T90 (15-350 keV) is 9.0 +- 1.0 sec (estimated error including systematics).
 
The time-averaged spectrum from T-1.9 to T+6.1 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
2.25 +- 0.58.  The fluence in the 15-150 keV band is 7.6 +- 2.6 x 10^-8 erg/cm2.
The 1-sec peak photon flux measured from T+0.07 sec in the 15-150 keV band
is 0.4 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.