GRB 091130B

J. L. Racusin (NASA/GSFC), S. D. Barthelmy (GSFC),
A. P. Beardmore (U Leicester), J. R. Cummings (NASA/UMBC),
P. A. Evans (U Leicester), S. T. Holland (CRESST/USRA/GSFC),
E. A. Hoversten (PSU), J. A. Kennea (PSU),
H. A. Krimm (CRESST/GSFC/USRA), J. Mao (INAF-OAB),
R. Margutti (Univ Bicocca&OAB), F. E. Marshall (NASA/GSFC),
C. Pagani (PSU), K. L. Page (U Leicester), T. Sakamoto (NASA/UMBC),
M. H. Siegel (PSU), E. Troja (NASA/GSFC/ORAU) and
T. N. Ukwatta (GSFC/GWU) report on behalf of the Swift Team:

At 17:59:04 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 091130B (trigger=377487).  Swift slewed immediately to the burst. 
The BAT on-board calculated location is 
RA, Dec 203.098, +34.075 which is 
   RA(J2000)  =  13h 32m 24s
   Dec(J2000) = +34d 04' 31"
with an uncertainty of 3 arcmin (radius, 90% containment, including 
systematic uncertainty).  The BAT light curve shows two, possibly three, peaks
with a total duration of about 100 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 18:00:30.2 UT, 85.4 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 203.1487, +34.0883 which is equivalent to:
   RA(J2000)  = 13h 32m 35.68s
   Dec(J2000) = +34d 05' 17.8"
with an uncertainty of 4.8 arcseconds (radius, 90% containment). 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 5.45e-09 erg cm^-2 s^-1 (0.2-10
keV). 

UVOT took a finding chart exposure of 136 seconds with the White filter
starting 94 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
0.01. 

Burst Advocate for this burst is J. L. Racusin (judith.racusin AT nasa.gov). 
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.J. Levan (U. Warwick), N.R. Tanvir (U. Leicester) report:

"Inspection of SDSS images of GRB 091130B (Racusin et al. GCN 10214
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 )
shows a faint galaxy (r=22.5),  inside the XRT localization.
There is also a brighter galaxy (r=18.9) offset roughly 7" from the
XRT position (which has a 4.8" error radius). The detection of these
objects suggests that GRB 091130B could be a relatively low redshift
event."

S.Sergienko, V.Yurkov
Blagoveschensk Educational State University, Blagoveschensk


E. Gorbovskoy, D. Zimnukhov, V. Lipunov, V.Kornilov, A.Belinski, D.Kuvshinov, 
N.Shatskiy,  N.Tyurina, P.Balanutsa, V.V.Chazov,
A.Kuznetsov

Sternberg Astronomical Institute, Moscow State University

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

V.Krushinski, I.Zalognikh, T.Kopytova, A. Popov
Ural State University, Kourovka

S.Yazev, K.Ivanov, N.M.Budnev, E.Konstantinov, V.Lenok Irkutsk State University


MASTER  robotic telescope (MASTER-Net: http://observ.pereplet.ru, D= 200 mm, 
FOV= 7  square degrees, 16 Mpx Apogee CCD, testing mode) located
at Blagoveschensk   was responted to the  GRB 091130B
(Racusin et al., GCN 10214
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 )   40 sec after Notice time and
65 s after the GRB time.
The exposition of the first image is 10s.

We do not see OT brighter 15 mag  at the Swift XRT position.

The reduction is continued.

The message may be cited.

We note that MASTER-Amur-Blagoveschensk are in testing mode now.

mailto: lipunov@sai.msu.ru

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

Using 3970 s of XRT Photon Counting mode data and 7 UVOT
images for GRB 091130B, 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 = 203.14844, +34.08839 which is equivalent
to:

RA (J2000): 13h 32m 35.63s
Dec (J2000): +34d 05' 18.2"

with an uncertainty of 1.6 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.

E. A. Hoversten (PSU) and J. L. Racusin (NASA/GSFC) report on behalf
of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 091130B
95s after the BAT trigger (Racusin et al., GCN 10214
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 ). We do not
detect any source at the enhanced Swift XRT position (Goad et al. GCN
10218
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 ). UVOT magnitude 3-sigma upper limits are reported in the
following table:

Filter   T_start   T_stop   Exp(s)  Mag (3-sigma upper limit)
-------------------------------------------------------------
white       95       230     132        > 20.20
white     4517      4717     196        > 20.97
v         3492      3692     196        > 19.38
b         4313      4512     196        > 20.31
u         4107      4307     196        > 19.91
uvw1      3903      4102     196        > 19.88
uvm2      3697      3897     196        > 19.76
uvw2      4723      4923     196        > 19.98

The quoted upper limits have not been corrected for the expected
Galactic extinction along the line of sight of E_(B-V) = 0.01 mag
(Schlegel et al. 1998). All photometry is on the UVOT photometric
system described in Poole et al. (2008, MNRAS, 383, 627).

T. N. Ukwatta (GWU), 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),
C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), A. M. Parsons (GSFC),
J. L. Racusin (NASA/GSFC), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC)
(i.e. the Swift-BAT team):

Using the data set from T-60 to T+243 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 091130B (trigger #377487)
(Racusin, et al., GCN Circ. 10214
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 ).  The BAT ground-calculated position
is RA, Dec = 203.149, 34.086 deg which is
    RA(J2000)  =  13h 32m 35.8s
    Dec(J2000) = +34d 05' 11.0"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 77%.

The mask-weighted light curve shows several broad, irregular, 
overlapping peaks starting at T-25 sec, peaking at T0 and ending
about T+120 sec.  T90 (15-350 keV) is 112.5 +- 17.1 sec (estimated
error including systematics).

The time-averaged spectrum from T-4.7 to T+127.4 sec is best fit by a
simple power-law model.  The power law index of the time-averaged 
spectrum is 2.15 +- 0.15.  The fluence in the 15-150 keV band is
1.3 +- 0.1 x 10^-06 erg/cm2.  The 1-sec peak photon flux measured from
T-0.06 sec in the 15-150 keV band is 1.1 +- 0.2 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/377487/BA/

[GCN OPS NOTE(01dec09): Changed "091130" to "091130B".]

K.L. Page (U. Leicester) and J. L. Racusin (NASA/GSFC) report on behalf of 
the Swift-XRT team: 

We have analysed 12 ks of XRT data for GRB 091130B (Racusin et al. GCN 
Circ. 10214
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 ), from 91 s to 29.1 ks after the BAT trigger. The data 
comprise 155 s in Windowed Timing (WT) mode with the remainder in Photon 
Counting (PC) mode. The enhanced XRT position for this burst was given by 
Goad et al. (GCN. Circ 10218).

The light curve can be modelled with a series of power-law decays. The 
initial index is alpha=-0.36 (+0.87, -1.14) - i.e., the light curve rises 
slightly. At T+107 s the light curve starts decaying with an alpha of 3.58 
(+0.24, -0.17). The light curve breaks again at T+172 s to a decay with 
alpha=2.11 (+0.24, -0.06), before a final break at T+4020 s, after which 
the decay index is 0.32 (+0.10, -0.11).

A spectrum formed from the WT mode data can be fitted with an absorbed 
power-law with a photon spectral index of 2.26 (+0.07, -0.06). The 
best-fitting absorption column is 2.32 (+/-0.17) x 10^21 cm^-2, in excess 
of the Galactic value of 8.0 x 10^19 cm^-2 (Kalberla et al. 2005). The PC 
mode spectrum has a photon index of 2.48 (+0.18, -0.19) and a best-fitting 
absorption column of 1.66 (+0.23, -0.43) x 10^21 cm^-2. The counts to 
observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this 
spectrum is 3.2 x 10^-11 (5.8 x 10^-11) erg cm^-2 count^-1.

If the light curve continues to decay with a power-law decay index of 
0.32, the count rate at T+24 hours will be 0.030 count s^-1, corresponding 
to an observed (unabsorbed) 0.3-10 keV flux of 9.6 x 10^-13 (1.7 x 10^-12) 
erg cm^-2 s^-1.

The results of the XRT-team automatic analysis are available at 
http://www.swift.ac.uk/xrt_products/00377487.

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