[vsnet-grb-info 9963] GRB 101117B: Swift/UVOT Observations of the Optical Afterglow
GCN Circulars
gcncirc at capella2.gsfc.nasa.gov
Tue Nov 23 00:25:39 JST 2010
TITLE: GCN CIRCULAR
NUMBER: 11420
SUBJECT: GRB 101117B: Swift/UVOT Observations of the Optical Afterglow
DATE: 10/11/22 15:25:34 GMT
FROM: Stephen Holland at USRA/NASA/GSFC/SSC <Stephen.T.Holland at nasa.gov>
S. T. Holland (CRESST/GSFC/USRA) and
C. W. Wolf (PSU)
report on the behalf of the Swift UVOT team:
The Swift/UVOT observed the field of GRB 101117B starting 63 s
after the BAT trigger (Wolf, et al., 2010, GCN Circ. 11411). Settled
observations started at 82 s. We detect the optical afterglow
(Holland, 2010, GCN Circ. 11412) in the U, B, and white filters. The
refined UVOT position is
RA (J2000) 11:32:00.54 = 173.00225 (deg)
Dec (J2000) -72:39:45.9 = -72.66275 (deg)
with an estimated uncertainty of 0.43 arcsec (radius, 90% confidence,
statistical + systematic). This is 1.16 arcsec northwest of the
UVOT-enhanced XRT position (Goad, et al., 2010, GCN Circ. 11413).
Preliminary magnitudes, and 3-sigma upper limits for detecting a
source in the finding charts and in the co-added images, are
Filter T_start T_stop Exp(s) Mag Err
-----------------------------------------------------------
white (fc) 82 232 147 17.81 0.08
u (fc) 295 545 246 18.68 0.15
v 626 646 20 >17.9
b 551 571 20 18.22 0.27
u 700 1325 59 >19.1
uvw1 675 1300 78 >19.3
uvm2 825 1275 58 >18.7
uvw2 601 1051 58 >19.0
white 575 595 20 19.20 0.34
-----------------------------------------------------------
The quoted magnitudes and upper limits have not been corrected
for the expected Galactic extinction along the line of sight
corresponding to a reddening of E_{B-V} = 0.38 mag (Schlegel, et al.,
1998, ApJS, 500, 525). All photometry is on the UVOT photometry
system described in Poole et al. (2008, MNRAS, 383, 627).
The non-detection in the UVOT uvw1 filter, and the observed UVOT
spectral energy distribution at 600 s, is consistent with GRB 101117B
having a redshift of approximately z <= 3, although we can not rule
out the non-detection in the ultraviolet being due to extinction in
the host galaxy. The white light curve exhibits a power-law decay
with an index of alpha = -0.8 +/- 0.1 between 82 and 6005 s after the
BAT trigger.
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