GRB 081109A
GCN Circular 8503
Subject
GRB 081109A optical upper limit
Date
2008-11-09T14:15:04Z (17 years ago)
From
AAVSO GRB Network at AAVSO <matthewt@aavso.org>
Peter Nelson (Ellinbank, Victoria, Australia) reports to the AAVSO
International High Energy Network the following optical observation of
GRB081109A (GCN #8500 Immler et al.; GCN #8501 D'Avanzo et al.):
Peter Nelson has obtained a limiting magnitude on the optical afterglow of
GRB081109A (Immler et al., GCN #8500). The near IR afterglow position RA:
22:03:09.72 Dec: -54:42:39.5 found by D'Avanzo et al. (GCN #8501) was observed
for 120 seconds using a 0.32-meter Newtonian with an SBIG ST8XE
CCD and an R filter under poor photometric conditions. The mid-point of
the observations was 2008 Nov 09.5188 UT, approximately 5.4 hours after the
burst. The afterglow was not detected to an upper limit of R=18.1, using
the USNO-A2.0 star 0300-37476396 (R=13.2) as the comparison.
A detailed report of these observations is available on the AAVSO website
at ftp://ftp.aavso.org/grb/PeterNelson_081109_2454780.06997_.txt
A fits image is available at
ftp://ftp.aavso.org/grb/PeterNelson_081109_2454780.06997_.fits
The AAVSO thanks the Curry Foundation for their continued support of the
AAVSO International High Energy Network.
GCN Circular 8506
Subject
GRB 081109A: Swift-XRT refined analysis
Date
2008-11-09T16:19:07Z (17 years ago)
From
Andy Beardmore at U Leicester <apb@star.le.ac.uk>
A.P. Beardmore, K.L. Page (U. Leicester) and S. Immler (CRESST/GSFC/UMD)
report on behalf of the Swift-XRT team.
The Swift-XRT started observing the field of GRB 081109A (trigger
#334112, Immler et al., GCN 8500) at 07:03:12.2 UT, 65.6 s after
the BAT trigger. The XRT observed the GRB in Windowed Timing (WT) mode
until 318 s after the trigger and Photon Counting (PC) mode thereafter.
Using 4661 s of XRT Photon Counting mode data and 7 UVOT images, we
find an astrometrically corrected X-ray position (using the XRT-UVOT
alignment and matching to the USNO-B1 catalogue) of
RA, Dec = 330.7905, -54.7118 which is equivalent to :
RA (J2000): 22h 03m 9.72s
Dec (J2000): -54d 42m 42.5s
with an uncertainty of 1.4 arcsec (90% confidence). This is 2.98
arcsec from the reported possible NIR counterpart of D'Avanzo (GCN
8501).
The X-ray light curve from the first three orbits can be modelled with
a broken powerlaw with an initial decay slope of 1.78 +/- 0.06, a break
time of 353 +/- 40 s, followed by a shallower decay slope of 0.99 +/- 0.04.
The spectrum of the WT data from orbit 1 (from T+71.9 s to T+318.4 s,
where T is the trigger time) can be well fit by an absorbed powerlaw
with a photon index of 1.72 +/- 0.08 and column density of
(1.84 +/- 0.22) x 10^21 cm^-2, compared with the Galactic column
density of 1.6 x 10^20 cm^-2 in the direction of the burst. The observed
0.3-10 keV flux is (7.4 +/- 0.4) x 10^-10 erg cm^-2 s^-1. The
corresponding unabsorbed 0.3-10 keV flux is (9.5 +/- 0.5) x 10^-10
erg cm^-2 s^-1.
A powerlaw fit to a spectrum obtained from PC mode data spanning
orbits 2 to 3 (T+4.76 ks to T+12.88 ks) is best fit with a photon
index of 2.20 +/- 0.20 and column density (3.1 +/- 0.7) x 10^21 cm^-2.
The observed 0.3-10 keV flux over this interval is (7.3 +/- 0.7) x 10^-12
erg cm^-2 s^-1. The count-to-observed-flux conversion factor is
6.0e-11 erg cm^-2 count^-1.
Assuming the X-ray emission from the burst continues to decline at the
same rate we predict an XRT count rate of 0.018 count s^-1 at T+24 hour,
or an observed 0.3-10 keV X-ray flux of 1.1 x 10^-12 erg cm^-2 s^-1.
This circular is an official product of the Swift-XRT team.
GCN Circular 8507
Subject
GRB 081109A, Swift-BAT refined analysis
Date
2008-11-09T16:42:12Z (17 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
C. B. Markwardt (GSFC/UMD), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
S. Immler (CRESST/GSFC/UMD), H. A. Krimm (GSFC/USRA), 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 081109A (trigger #334112)
(Immler, et al., GCN Circ. 8500). The BAT ground-calculated position is
RA, Dec = 330.798, -54.711 deg, which is
RA(J2000) = 22h 03m 11.5s
Dec(J2000) = -54d 42' 40.5"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 73%.
The mask-weighted light curve shows a smooth rise to a single peak
starting at ~T-90 sec, peaking at ~T+5 sec, and roughly exponentially decaying
back to baseline at ~T+400 sec.
T90 (15-350 keV) is 190 +- 60 sec (estimated error including systematics).
The time-averaged spectrum from T-15.9 to T+416.1 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.72 +- 0.09. The fluence in the 15-150 keV band is 3.6 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+7.64 sec in the 15-150 keV band
is 1.1 +- 0.0 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/334112/BA/
GCN Circular 8508
Subject
GRB 081109A: Faulkes Telescope South observations
Date
2008-11-09T19:27:53Z (17 years ago)
From
David Bersier at Liverpool John Moores U <dfb@astro.livjm.ac.uk>
C. Guidorzi (INAF-OAB), D. Bersier, M. Burgdorf, C.G. Mundell (LJMU)
and N. Tanvir (U. Leicester) report on behalf of a larger collaboration:
We observed GRB 081109A (Immler et al. GCN Circ. 8500) with the 2m
Faulkes Telescope South starting on November 11 at 11:50:36 UT
(corresponding to 4.81 hours post burst) in the R and i' filters.
We do not detect any object at the position of the REM afterglow
(D'Avanzo et al., GCN Circ 8501) down to magnitudes 21.0 and 21.2
in the R and i' filters respectively.
These upper limits are conservative however, as there is a possible
flux excess at the position of the REM afterglow but further analysis
is required to ascertain the reality of this source.
The calibration was performed using the R2 and I values of the
nearby USNOB1 star RA=22:03:01.679, Dec=-54:43:07.05 (R2=16.88, I=16.46).
GCN Circular 8509
Subject
GRB 081109A: Possible Swift-UVOT detection
Date
2008-11-10T01:35:23Z (17 years ago)
From
Stefan Immler at NASA/GSFC <stefan.m.immler@nasa.gov>
S. Immler (CRESST/UMD/GSFC), N. P. M. Kuin (MSSL/UCL), and S. T. Holland
(CRESST/USRA/GSFC) report on behalf of the Swift UVOT team:
Further analysis of Swift Ultraviolet/Optical Telescope (UVOT) data of
GRB 081109A (Immler et al., GCN Circ. 8500), starting 75 sec after the
BAT trigger, gives a tentative detection of an optical source at the
reported REM position (D'Avanzo et al., GCN Circ 8501) in the white
filter at a 3.3-sigma level of confidence. The source is not detected in
any of the other UVOT filters at the limiting magnitudes reported below.
Filter Tstart(s) Tstop(s) Exp(s) Magnitude
wh 75 6592 745 21.6+/-0.3
u 287 6181 501 >21.5 (3-sigma UL)
b 543 6387 452 >20.9 (3-sigma UL)
uvw2 593 5362 274 >21.6 (3-sigma UL)
v 617 5566 274 >20.9 (3-sigma UL)
uvm2 641 5771 274 >21.5 (3-sigma UL)
uvw1 666 5976 255 >21.5 (3-sigma UL)
The possible detection in the white filter, combined with the lack of a
detection in the v filter, is consistent with the source having a
redshift greater than 5.5.
Follow-up observations, especially in the infrared, are encouraged.
GCN Circular 8523
Subject
GRB 081109A: confirmation of possible detection host galaxy
Date
2008-11-17T00:02:24Z (17 years ago)
From
Paul Kuin at MSSL <npkuin@googlemail.com>
N. P. M. Kuin (MSSL/UCL) and S. Immler(CRESST/GSFC/UMD) report on
behalf of the Swift UVOT team.
Continued observations by the Swift UltraViolet/Optical Telescope
(UVOT) of the field of GRB 081109A (Immler et al., GCN Circ. 8500,
Kuin and Immler, GCN Circ. 8504, Immler et al., GCN Circ. 8509)
confirm that a weak source is present close to the REM position
(D'Avanzo et al, GCN Circ. 8501) and also close to the refined
XRT position (Beardmore et al., GCN Circ. 8506).
We detect a constant source in 166 images totaling 54.4 ks of exposure time
over a period of 544 ks (~1 week) in the UVOT white filter at position:
RA = 22:03:09.579, Dec = -54.42.40.49 (J2000)
with an uncertainty of 0.8 arcsec (90% confidence). The source
magnitude in the summed image is wh = 22.86 +/- 0.09 mag (11.5 sigma detection).
The values quoted above are on the UVOT Photometric System
(Poole et al, 2008, MNRAS 383,627). They are not corrected for the
expected galactic reddening of E(B-V) = 0.019 in the direction of
the burst (Schlegel et al. 1998).
We interpret this image as the possible host galaxy. In that case the
REM position offset suggests that the GRB took place on the edge of the
host galaxy. The source we detect is also just outside the XRT error
circle.