GRB 071112B

M. Perri (ASDC), S. D. Barthelmy (GSFC), J. R. Cummings (NASA/UMBC),
N. Gehrels (NASA/GSFC), C. Gronwall (PSU),
S. T. Holland (CRESST/USRA/GSFC), J. A. Kennea (PSU),
C. B. Markwardt (CRESST/GSFC/UMD), S. Mateos (U Leicester),
D. M. Palmer (LANL), A. M. Parsons (GSFC),
P. Romano (Univ. Bicocca & INAF-OAB),
R. L. C. Starling (U Leicester), G. Stratta (ASDC),
T. N. Ukwatta (GSFC/GWU), D. E. Vanden Berk (PSU) and
S. D. Vergani (DIAS-DCU) report on behalf of the Swift Team:

At 18:23:31 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 071112B (trigger=296503).  Swift did not slew because
of the Earth observing constraint.  Swift will slew at T+33 min. 
The BAT on-board calculated location is 
RA, Dec 260.305, -80.884 which is 
   RA(J2000)  =  17h 21m 13s
   Dec(J2000) = -80d 53' 02"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows a double spike
structure with a duration of about 1 sec.  The peak count rate
was ~4500 counts/sec (15-350 keV), at ~0 sec after the trigger. 

Because of an Earth limb constraint, the spacecraft did not slew promptly
to the BAT position, and so there are no immediate XRT or UVOT data 
products to analyze. 

Burst Advocate for this burst is M. Perri (perri AT asdc.asi.it). 
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.S. Rykoff (UCSB), F. Yuan (U Mich), W. Rujopakarn (Steward), report on 
behalf of the ROTSE collaboration:

ROTSE-IIIc, located at the H.E.S.S. site at Mt. Gamsberg, Namibia, 
responded to the short/hard GRB 071112B (Swift trigger 296503; Perri et 
al., GCN 7058
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 ), producing images beginning 6.8 s after the GCN notice 
time. An automated response took the first image at 18:23:55.8 UT, 24.3 
s after the burst, under fair conditions. We took 10 5-sec, and 10 
20-sec exposures before ROTSE-IIIc repointed at Swift trigger 296504 
(GRB071111C). These unfiltered images are calibrated relative to USNO 
A2.0 (R).

Comparison to the DSS (second epoch) reveals no new sources within the 
3-sigma Swift/BAT error circle, for both single images and coadding into 
sets of 10. Individual images have limiting magnitudes ranging from 
15.3-16.3; we set the following specific limits.

start UT       end UT      t_exp(s)   mlim   t_start-tGRB(s)  Coadd?
--------------------------------------------------------------------
18:23:55.8   18:24:00.8         5     15.5           24.3       N
18:23:55.8   18:25:45.1       109     16.6           24.3       Y
18:25:53.0   18:31:02.2       309     17.3          141.5       Y

E. Fenimore (LANL), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
D. Palmer (LANL), A. Parsons (GSFC), M. Perri (ASDC),
T. Sakamoto (GSFC/UMBC), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-120 to T+182 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 071112 (trigger #296503)
(Perri, et al., GCN Circ. 7058
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 ).  The BAT ground-calculated position is
RA, Dec = 260.213, -80.884 deg, which is 
   RA(J2000)  =  17h 20m 51.0s 
   Dec(J2000) = -80d 53' 02" 
with an uncertainty of 2.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 78%.
 
The mask-weighted light curve shows two separated narrow peaks.  The first
starts at T-0.7 sec and has a total width of ~64 msec.  The second
starts at T+0.0 sec, peaks at T+0.1 sec, and ends at 0.3 sec.
T90 (15-350 keV) is 0.30 +- 0.05 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.0 to T+0.3 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
0.69 +- 0.34.  The fluence in the 15-150 keV band is 4.8 +- 0.9 x 10^-8 erg/cm2.
The 1-sec peak photon flux measured from T-0.38 sec in the 15-150 keV band
is 1.3 +- 0.3 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 

The automated script processing has generated fluence and spectral numbers
for the second peak only.  Since there seems to be urgent need in the 
community, we are pushing this circular out the door quickly so that at
least these partial (second peak only) values are available to the 
follow-up community.  By eye, the first peak appears to have a fluence
one third that of the second peak.  Also by eye, there appears to be no
extended emission for this SHB out to at least T+180 sec and to a flux
level ~0.007 counts/cm2/sec.

M. Perri, G. Stratta (ASDC), D.N. Burrows (PSU) report on behalf of the
Swift-XRT team:

The Swift-XRT began observing the field of the short hard GRB 071112B
(trigger=296503, Perri et al., GCN Circ. 7058
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 ) at 19:25:35 UT, about
62 minutes after the BAT trigger. In the first 2.1 ks of Photon Counting
mode data, no X-ray source is detected within the refined BAT error
circle (Fenimore et al., GCN Circ. 7071
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 )

We estimate a 3-sigma upper limit on the count rate of ~5e-3 cts/s.
Assuming a power-law spectrum with photon index Gamma=2 and a Galactic
column density of 7.9e20 cm-2, this corresponds to an upper limit on the
observed flux of ~2e-13 ergs/cm2/s (0.3-10 keV)

This is an official product of the Swift XRT Team.

J. S. Bloom, D. Kocevski (UC Berkeley), and H.-W. Chen report:

"We obtained target of opportunity imaging of the field of SHB  
071112B (Perri et al. GCN 7058
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 ; Fenimore et al. 7071) on Gemini South  
after twilight.  Several images of 15 sec and 180 sec were obtained  
as the sky darkened. Inspection of a single 180 sec image in r band  
(start =  2007-11-13 00:51:17.5 UTC) did not reveal a bright new  
source when compared to DSS2 (Red) inside the reported XRT error  
circle, although we do note a very weak candidate near the DSS limit  
at (J2000):

RA: 17:21:15.62
DEC: -80:53:50

We make no claims to variability nor newness at this time, but  
further Gemini observations are planned."

We thank Ruben Diaz and the entire Gemini staff for assistance in  
taking this data.

J. S. Bloom notes:

"The position of the source noted in GCN #7073
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  should read:
  17:21:27.1, -80:53:48

We thank E. Berger for correspondence on this source (who also  
pointed out that that source appears in the DSS II N-plate)."

E. Berger (Princeton/OCIW) and P. Challis (CfA) report:

"We observed the BAT error circle of the short GRB 071112B (GCN 7071
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 ) with 
LDSS3 on the Magellan/Clay telescope.  A total of 1200 sec were obtained 
in the i-band in 0.9" seeing starting 6.25 hours after the burst.  A 
comparison to DSS reveals no new bright sources within the BAT error 
circle.  A comparison of the first and final images (with a separation of 
20 min) reveals no clear fading sources, although we note that the time 
baseline is very short.  Further observations are in progress."

P. Schady (MSSL-UCL) and M. Perri (ASDC) report on behalf of the Swift 
UVOT team:

The Swift UVOT observed the field of GRB 071112B (Perri et al., GCN 7058
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 ) 
62 minutes after the BAT trigger, once the Earth had come out of observing 
constraint. No new source is found in any of the UVOT observations in 
either single or co-added exposures within the refined BAT error circle 
(Fenimore et al., GCN 7071
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 ) or anywhere within the UVOT field of view down 
to the following 5-sigma upper limits:

Filter  Tmid    Exp     Magnitude
         (s)     (s)    (5-sigma UL)
White   8864    885      > 20.7
v       3826    197      > 18.2
b       8306    197      > 19.5
u       6905    290      > 19.1
uvw1    4236    197      > 18.8
uvm2    4031    197      > 18.7
uvw2    9419    187      > 18.9

where Tmid is the weighted mean of the co-added exposures. The values 
quoted above are not corrected for the expected Galactic extinction 
corresponding to a reddening of E(B-V) = 0.12 mag in the direction of the 
GRB (Schlegel et al. 1998).

E. Berger (Princeton/OCIW) and P. Challis (CfA) report:

"We re-observed the BAT error circle of the short GRB 071112B (GCN 7071
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 ) 
with LDSS3 on the Magellan/Clay telescope.  A total of 1200 sec were 
obtained in the i-band in 0.8" seeing starting about 30 hours after the 
burst.  A comparison to our first epoch of imaging taken about 6 hours 
after the burst (GCN 7075
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 ) reveals no variable sources to a conservative 
limit of about 23.5 mag.  Further analysis is in progress."

Mark H. Wieringa (Australia Telescope National Facility), Poonam
Chandra (UVA/NRAO), and Dale A. Frail (NRAO) report on behalf
of a larger collaboration:

"We observed the region centered on the Swift burst GRB 071112B (GCN 7058
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 )
using the Australia Telescope Compact Array starting at UT 7.0 Nov 14, 07
and ending at UT 15.0 Nov 14, 07. No emission was seen at a frequency of
8.7 GHz within the BAT error circle. The 5-sigma detection limits in BAT
error circle are 235 uJy. The map noise is 47 uJy."

The Australia Telescope Compact Array is part of the Australia
Telescope which is funded by the Commonwealth of Australia for
operation as a National Facility managed by CSIRO.

K. Wiersema, N. Tanvir (Leicester), A. Levan (Warwick), D. Malesani (DARK, 
NBI), P. Jakobsson (Hertfordshire), E. Rol and R. Starling (Leicester) 
report on behalf of a larger collaboration:

We observed the BAT position of the short GRB 071112B (GCN 7071
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 ) using 
FORS2 on the VLT. We acquired two epochs of data, the first in VRI, the 
second in R band only. The first R band epoch, consisting of 5 x 4 minutes 
exposures, started at 00:25:02 UT on 13 november. The second epoch, again 
5 x 4 minutes exposures, started at 00:47:00 UT on 14 november. Both 
epochs were taken in good seeing conditions (0.7 and 0.9 arcsec 
respectively) but at high airmass. Limiting magnitudes (3 sigma) are 
estimated at R = 25.2 and R = 25.5 for the first and second epochs, 
respectively. 

Both visual inspection and PSF-matched image subtraction using the ISIS2 
code (Alard 2000) did not reveal a significantly fading source in or near 
the BAT error circle.

We note that the limiting magnitudes above may not be fully representative 
for the upper limit on the afterglow brightness, as the BAT error circle 
contains some nebulosity, and the dithering pattern employed to avoid the 
chip-gap between the two FORS2 chips means that a narrow strip through the 
error circle has received comparatively less illumination.

We thank the Paranal staff for their excellent support, particularly 
Stephane Brillant and Linda Schmidtobreick.

D. Kocevski and J. S. Bloom (U.C.  Berkeley), on behalf of a larger  
collaboration, report:

"We performed image subtraction between multiple r-band observations  
of the error box of SHB 071112B (Perri et al. GCN 7058
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 ; Fenimore et  
al. 7071) on Gemini South.  The first epoch of observations began at  
2007-11-13 00h14m UTC (airmass ~2.0) followed by a second epoch ~4  
hours later at 2007-11-13 04h08m UTC (airmass ~2.6), with total  
exposures of 1800 sec and 1043 sec, seconds respectively.  Image  
subtraction using the public IPP package (*) software shows no  
variable sources to r=23.7 mag (3 sigma) within the >95% of the BAT  
error circle.  No further observations are planned."

This message may be cited.

* See http://pan-starrs.ifa.hawaii.edu/project/IPP/software/