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GCN Circular 11420

Subject
GRB 101117B: Swift/UVOT Observations of the Optical Afterglow
Date
2010-11-22T15:25:34Z (14 years ago)
From
Stephen Holland at USRA/NASA/GSFC/SSC <Stephen.T.Holland@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. 11411Not found
 
 
).  Settled
observations started at 82 s.  We detect the optical afterglow
(Holland, 2010, GCN Circ. 11412Not found
 
 
) 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. 11413Not found
 
 
).

     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.