GRB 081102

T. N. Ukwatta (GSFC/GWU), S. D. Barthelmy (GSFC),
J. R. Cummings (NASA/UMBC), N. Gehrels (NASA/GSFC),
C. Gronwall (PSU), C. Guidorzi (INAF-OAB),
S. T. Holland (CRESST/USRA/GSFC), W.B Landsman (GSFC),
V. Mangano (INAF-IASFPA), J. Mao (INAF-OAB),
P. T. O'Brien (U Leicester), D. M. Palmer (LANL),
P. Romano (INAF-IASFPA), B. Sbarufatti (INAF-IASFPA),
M. Stamatikos (NASA/ORAU) and H. Ziaeepour (UCL-MSSL) report on
behalf of the Swift Team:

At 17:44:39 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 081102 (trigger=333427).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 331.182, +52.993 which is 
   RA(J2000)  = 22h 04m 44s
   Dec(J2000) = +52d 59' 36"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows multiple peaks
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 17:46:11.5 UT, 92.0 seconds after
the BAT trigger. Using promptly downlinked data we find a bright, fading
uncatalogued X-ray source located at RA, Dec 331.17357, 52.99345 which
is equivalent to:
   RA(J2000)  = 22h 04m 41.66s
   Dec(J2000) = +52d 59' 36.4"
with an uncertainty of 3.3 arcseconds (radius, 90% containment). This
location is 18 arcseconds from the BAT onboard position, within the BAT
error circle. This position may be improved as more data are received;
the latest position is available at http://www.swift.ac.uk/sper. 

A power-law fit to a spectrum formed from promptly downlinked event
data gives a column density consistent with the Galactic value of
4.95e+21 cm^-2 (Kalberla et al. 2005). 

The initial flux in the 2.5 s image was 2.85e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 150 seconds with the White
(160-650 nm) filter starting 99 seconds after the BAT trigger. No
afterglow candidate has  been found in the initial data products. The
2.7'x2.7' sub-image covers all of the XRT error circle.  The image
is typically complete to about 18 mag. No  correction has been made
for the expected extinction corresponding to E(B-V) of  0.81. 

Burst Advocate for this burst is T. N. Ukwatta (tilan.ukwatta AT gmail.com). 
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. Stefanescu, N. Primak, F. Schrey, G. Kanbach, A. Slowikowska, H.
Steinle, A. Updike and N. Lewandowski of the OPTIMA-Burst Team report
the following:

OPTIMA-Burst at the 1.3m Skinakas Observatory, of the University of
Crete and the Foundation for Research and Technolgy -- Hellas observed
the location of the XRT error-circle of GRB 081102 (GCN Circ 8462
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 , T. N.
Ukwatta et al.), starting at 2008-11-02 18:02:23 UT (~18 min after the
burst).

We did not detect any source inside the XRT error-circle in several
co-added short (10-50s) white-light target acquisition frames taken
under adverse conditions.

Our limit is as follows:

t-t_0 (mid-exp)       t_exp     limit (white light)
1276s                 210s      18.5

Observations are ongoing.

MASTER-Net Team (http://observ.pereplet.ru):

V. Lipunov, V.Kornilov,  E.Gorbovskoy,
A.Belinski, N.Shatskiy, N.Tyurina, D.Kuvshinov, P.Balanutsa
Sternberg Astronomical Institute, Moscow State University

A. Tlatov, I.Golubov
Kislovodsk Solar Station of the Pulkovo observatory

V.Krushinski, I.Zalognikh
Ural State University, Kourovka


S.Yazev, K.Ivanov
Irkutsk State University


MASTER Very Wide Field Camera located at Kislovodsk (2000 m)
(http://apollo.sai.msu.ru/, D=50 mm, 4000 square degrees, 35'' per pix) 
has observed the Swift-BAT GRB081102 error box  (Ukwatta et al., GCN Circ 
8642
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 ) with 5s exposures  starting before, during and after the GRB time.

These unfiltered images are calibrated relative to USNO A2.0 (R).
The limit of the each image is aboute 11.1 (S/N=3).

The reduction is continuing.

mailto: lipunov@sai.msu.ru

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

Using 4108 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 081102, 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 = 331.1724, +52.9942 which is equivalent
to:

RA (J2000): 22h 04m 41.38s
Dec (J2000): +52d 59' 39.3"

with an uncertainty of 1.5 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
http://www.swift.ac.uk/xrt_positions/Goad.pdf), the current algorithm is an
extension of this method.

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

E. E. Fenimore (LANL), 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/UMD), D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. N. Ukwatta (GWU)
(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 081102 (trigger #333427)
(Ukwatta, et al., GCN Circ. 8462
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 ).  The BAT ground-calculated position is
RA, Dec = 331.178, 52.991 deg, which is 
   RA(J2000)  =  22h 04m 42.6s 
   Dec(J2000) = +52d 59' 27.7" 
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 36%.
 
The mask-weighted light curve shows two overlapping peaks, the first starting
at ~T-20 sec, peaking at ~T-15 sec, and hitting a minimum between the two
peaks at ~T-7 sec.  The second peak peaks at ~T+1 sec, and returns to background
at ~T+90 sec.  T90 (15-350 keV) is 63 +- 16 sec (estimated error
including systematics).
 
The time-averaged spectrum from T-20.2 to T+62.8 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.73 +- 0.13.  The fluence in the 15-150 keV band is 2.3 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.08 sec in the 15-150 keV band
is 1.4 +- 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/333427/BA/

S. Immler (GSFC/CRESST/UMCP) and T. N. Ukwatta (GSFC/GWU) report on the 
behalf of the Swift UVOT team:

The Swift Ultra-Violet/Optical Telescope (UVOT) began observing GRB 
081102 (trigger 333427) 83 seconds after the BAT trigger (Ukwatta et 
al., GCN Circ. 8462
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 ). No afterglow is detected at the enhanced XRT 
position (Osborne et al., GCN Circ. 8467
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 ) in the initial v-filter 
finding chart or subsequent images. The limiting magnitudes (3-sigma in 
3" radius apertures) in each of the UVOT filters are as follows:

Filter  T_start(s)  T_stop(s)  Exp(s)  Mag UL (3sig)

white      100       19051       1246     >21.9
v           83      35803       1423     >20.3
b          433      24833       1808     >21.3
u          408     30614       2717     >21.3
uvw1       383      29977       2922     >21.1
uvm2      359      36395       2701     >20.9
uvw2      309      34890       1434     >20.7

The values quoted above are in the UVOT photometric system (Poole et al. 
2008, MNRAS, 383, 627). They are not corrected for the high (and 
unreliable) Galactic extinction at the low Galactic latitude of the 
burst of <5 degrees.

V. Mangano, B. Sbarufatti, V. La Parola (INAF-IASF Pa), T. Ukwatta  
(GSFC/GWU)
report on behalf of the Swift-XRT team:

Swift-XRT began observing the field of GRB 081102 (trigger 333427,  
Ukwatta et
al., GCN circ.8462
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 ) at 17:46:11.5 UT, 92.0 seconds after the BAT  
trigger.
We analysed data from the first 10 orbits, consisting of 151 s in  
Windowed
Timing mode, from T+98 s to T+251s and 14 ks in Photon Counting mode,  
from
T+251s to T+42.1 ks. The lightcurve is best fit by a broken powerlaw  
model
with slopes alpha_1 = -2.35 +/- 0.15 and alpha_2= -1.22 (-0.11 +0.22)  
and
break time T_break = T+560 (-160 +500)s. After the break, we observe  
a strong
flare at T+960 (-11+21) s with decay time 157 +/-15 s.

The WT spectrum is best fit by a simple absorbed powerlaw with photon  
index
2.7 +/- 0.1 and an absorbing column consistent with the Galactic  
value of
4.9E21 cm^-2 (Kalberla et al. 2005). The observed (unabsorbed) flux  
in the
0.3 - 10 keV band is 4.0E-10 (1.3E-9) erg cm^-2 s^-1. The PC spectrum  
is best
fit by a simple absorbed powerlaw with photon index 1.97 +/- 0.1 and an
absorbing column consistent with the Galactic value. The observed  
(unabsorbed)
flux in the 0.3 - 10 keV band is 1.1 (1.8)E-11 erg cm^-2 s^-1. The  
countrate to flux
conversion factor is 7.1E-11.

The predicted countrate for November 3, 17:45 UT (T+ 24h) is 1.3E-3  
counts/s
equivalent to a flux of 9.2E-14 erg cm^-2 s^-1.

All quoted errors are at 90% confidence level.

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

MASTER-Net Team (http://observ.pereplet.ru):

V. Lipunov, V.Kornilov,  E.Gorbovskoy,
A.Belinski, N.Shatskiy, N.Tyurina, D.Kuvshinov, P.Balanutsa
Sternberg Astronomical Institute, Moscow State University

A. Tlatov, A.Parkhomenko
Kislovodsk Solar Station of the Pulkovo observatory

V.Krushinski, I.Zalognikh
Ural State University, Kourovka


S.Yazev, K.Ivanov
Irkutsk State University


MASTER Very Wide Field Camera located at Kislovodsk (2000 m)
(http://apollo.sai.msu.ru/, D=50 mm, 4x1000 square degrees, 35'' per pix) 
has observed the Swift-BAT GRB081102 error box  (Ukwatta et al., GCN Circ 8642
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 ) 
with 5s exposures during all night without windows between images. 
There are two  separeted (~702m) mount with double cameras.

Now we present results from North camera.

These unfiltered images are calibrated relative to Tycho stars (V).
We do not detect any new source at the XRT position
reported in GCN Circ. 8467
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  ( Osborne et al.) brighter than 12.4 mag 
before and after trigger time.
The photometry results +-4 min around trigger time:


  T-T_trigger            m_lim (S/N=3)         Exposure         Coadd

-255s... 0... 255 s       11.6                  5s              no 
-2min...0...+2 min        12.2                 30s               6
-2min...0...+2 min        12.4                 60s              12

The optical fluence during the 60s-GRburst is limited by <= 6x10_-9 
erg/cm_2    including 2.5 magnitude  absorbtion (Ukwatta et al., Circ 
8462). The BAT-fluence is aboute 3 10_-6 erg/cm_2 (15-150 Kev) 
(http://gcn.gsfc.nasa.gov/notices_s/333427/BA/).
So

Optical Fluence/Gamma-Fluence ~ < 1/500

Same ratio for GRB080319B is ~ 1/200 (Naked Eye GRB).

The  light curve  is available at
http://observ.pereplet.ru/images/GRB081102/lc1.png


The  video  are available at
http://observ.pereplet.ru/images/GRB081102/grb.gif
You can see 200 sets.
Note: the GRB was at the edge of the FOW.

The reduction is continuing.

mailto: lipunov@sai.msu.ru

C. Kouveliotou (NASA/MSFC) and M.S. Briggs (UAHuntsville) report on
behalf of the Fermi GBM Team:

At 17:44:21.6 UT on 02 November 2008, the Fermi GBM triggered and
located an event (trigger 247340662 / 081102739) which was also seen by
SWIFT (Ukwata et al. 2008, GCN 8462
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 ). The GBM on-ground location is
consistent with the Swift position; the GBM trigger time is 17.4 s
earlier than the Swift trigger. 

The GBM light curve shows a multiple peak event (three and possibly four
peaks) with T90= 88 s (50-300 keV). The time-averaged spectrum from
T0-2.048 s to T0+46.01 s is best fit by a exponentially cutoff power law
model with Epeak = 88.7 +/- 8.3 keV, and index 0.0 +/- 0.3 (chi squared
278 for 238 d.o.f.). The event fluence (50-300 keV) in this time
interval is (2.1 +/- 0.05)E-06 erg/cm^2. A Band function fit the
spectrum equally well (chi squared 276 for 237 d.o.f.) with Epeak=72 +/-
13, alpha = 0.44 +/- 0.58 and beta = -2.36 +/- 0.32. 

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

E. Gorbovskoy, V. Lipunov, V.Kornilov, 
A.Belinski, N.Shatskiy, N.Tyurina, D.Kuvshinov, P.Balanutsa
Sternberg Astronomical Institute, Moscow State University

A. Tlatov, A.Parkhomenko
Kislovodsk Solar Station of the Pulkovo Observatory

V.Krushinski, I.Zalognikh
Ural State University, Kourovka


S.Yazev, K.Ivanov
Irkutsk State University


Two of the four  MASTER Very Wide Field Cameras located at Kislovodsk
(http://apollo.sai.msu.ru/, D=50 mm, 4x1000 square degrees, 35'' per pix) has 
observed the Swift-BAT GRB081102 error box  (Mangano et al., GCN Circ 
8470
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 , Lipunov et al., GCN 8464
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 , 8471
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 ) 
with 5s exposures during all night without time gap between images. There 
are  two  separeted (~702m) mount with double cameras.

Now we present results from the North and South mounts.

These unfiltered images are calibrated relative to Tycho stars (V).
We do not detect any new source at the XRT position
reported in GCN Circ. 8470
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  (Mangano et al.) brighter than 13.0 
mag before and after trigger time.
The photometry results +-4 min around trigger time:


  T-T_trigger            m_lim (S/N=3)         Exposure         Coadd

-255s... 0... 255 s       11.8                  5s              yes 
-2min...0...+2 min        12.7                 2x30s             12
-2min...0...+2 min        13.0                 2x60s             24

The optical fluence during the 40s-GRBurst is limited by

     <= 1.6x10_-8 erg/cm_2


including 2.8 magnitude  absorbtion (Ukwatta et al., Circ 8462).
The  BAT-fluence is aboute 2.3x10_-6 erg/cm_2 (15-150 keV) 
(Fenimore et al., GCN 8468
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 ).

So:

Optical Fluence/Gamma-Fluence(15-150keV) ~ < 1/140

Same ratio for GRB080319B is ~ 1/25 (Naked Eye GRB) in 15-150 keV 
(Racusin, Karpov et al., Nature, vol.455, 183, 2008).


Scientific Master Team Report   are available at
http://observ.pereplet.ru/images/GRB081102/grb_film.html

Note: the GRB was at the edge of the FOW in both cameras.
The message may be cited.

mailto: lipunov@sai.msu.ru

I. Khamitov, M.Parmaksizoglu (TUG), S.Alis, M.Hudaverdi (Istambul Uni.),
Z. Eker (TUG), U. Kiziloglu (METU),  E. Gogus (Sabanci Uni.),
R. Burenin, M. Pavlinsky, R. Sunyaev (IKI),
I. Bikmaev, N. Sakhibullin (KSU/AST)

report:

We observed the field of the Swift-BAT GRB 081102 (Ukwatta et al., 
GCN8462
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 ) with Russian-Turkish 1.5-m  telescope (RTT150, Bakirlitepe, 
TUBITAK National Observatory, Turkey), starting at 03 Nov, 17:44 UT, i.e. 
approximately 24.0 hours after the burst, using TFOSC CCD.

We made 3x300s exposures in R-band. We do not detect any new source inside
the XRT error circle (Osborne et al., GCN8467
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 ). Using USNO-B1 stars we 
estimated the limiting magnitude of combined image as m_R ~ 22.



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