[vsnet-grb-info 2202] GRB050922C - Swift UVOT preliminary analysis

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  4041
SUBJECT: GRB050922C - Swift UVOT preliminary analysis
DATE:    05/09/26 21:13:03 GMT
FROM:    Caryl Gronwall at PSU/Swift-UVOT  <caryl at astro.psu.edu>

S. D. Hunsberger (PSU), F. Marshall (GSFC), S. T. Holland (GSFC),
P. Brown (PSU), A. Morgan (PSU), P. Roming (PSU), and
A. Cucchiara (PSU) on behalf of the Swift/UVOT teams

The UVOT began observing GRB050922C at 19:57:41UT, 111 seconds
after the BAT trigger (Norris et al., GCN 4013). A fading
optical counterpart is detected at 21:09:33.0 -08:45:30.1. The
afterglow is apparent in the UBV filters and there is a marginal
detection in UVW1 which is likely due to the redward edge of the
filter response overlapping the U bandpass. The UVOT magnitudes
listed below are not corrected for extinction. Tmid is the time
since trigger of the midpoint of the exposure(s).


Filter    Tmid(s)     Exp(s)    Mag
V         115.5       99.8      14.60 +- 0.10
V         374.5        9.8      15.49 +- 0.17
V         543.5        9.8      15.99 +- 0.21
V         712.5        9.8      16.01 +- 0.21
V        4543.5      899.8      17.62 +- 0.11
V       15962.5      899.8      18.89 +- 0.21
V       28443.5      899.8      19.95 is 3sigma upper limit

B         261.5        9.8      15.88 +- 0.13
B         430.5        9.8      16.36 +- 0.15
B         598.5        9.8      16.45 +- 0.16
B         767.0        8.4      16.91 +- 0.20
B       11133.5      899.8      19.12 +- 0.11
B       22648.5      899.8      20.13 +- 0.21
B       39108.5      897.3      20.70 +- 0.38
B       50681.5      899.8      20.74 +- 0.39

U         246.5        9.8      15.09 +- 0.19
U         416.5        9.7      15.69 +- 0.20
U         584.5        9.8      15.84 +- 0.21
U         753.5        9.7      16.00 +- 0.21
U       10226.5      899.8      18.58 +- 0.18
U       21749.0      900.0      19.13 +- 0.20
U       34939.5      507.6      19.88 +- 0.31
U       46660.0      814.1      19.89 +- 0.26

UVW1      487.0       68.6      17.70 +- 0.29   (co-added 10s exposures)
UVW1     6233.5      651.1      19.96 +- 0.41
UVW1    17730.0      806.0      20.18 is 3sigma upper limit

UVM2      473.0       68.5      18.86 is 3sigma upper limit (co-added)
UVM2     5450.5      899.8      20.48 is 3sigma upper limit

UVW2      487.5       58.8      19.30 is 3sigma upper limit (co-added)
UVW2    11969.5      753.2      20.62 is 3sigma upper limit

Magnitudes are based on preliminary zeropoints, measured in orbit, and
may require further refinement.