[vsnet-grb-info 8789] GRB091208B: Swift/UVOT refined analysis
GCN Circulars
gcncirc at capella.gsfc.nasa.gov
Tue Dec 22 22:58:58 JST 2009
TITLE: GCN CIRCULAR
NUMBER: 10289
SUBJECT: GRB091208B: Swift/UVOT refined analysis
DATE: 09/12/22 13:58:52 GMT
FROM: Massimiliano de Pasquale at MSSL-UCL <mdp at mssl.ucl.ac.uk>
M. De Pasquale (MSSL/UCL) and H. Krimm (CRESST/GSFC/USRA)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB091221
80s after the BAT trigger with a 150s finding chart exposure in
the White filter.
We detect the optical afterglow in the finding chart exposure.
The refined UVOT position is RA = 55.79750, Dec = 23.24119 (J2000),
corresponding to
RA = 03h 43m 11.40s,
Dec = +23d 14m 28.3s (J2000)
with an estimated uncertainty of 0.6 arcsec (radius, 90% confidence).
This position is consistent with the XRT enhanced position (Evans
et al., GCN 10287) and ground-based detections (Zheng et al., GCN
10284; Klose et al., GCN 10286).
The afterglow is not detected anymore in single or summed exposures
in all filters. Preliminary magnitudes and 3 sigma upper limits
are reported below.
Filter T_start(s) T_stop(s) Exposure(s) Mag Err
-----------------------------------------------------------------------
white 80 230 149.8 20.19 +/- 0.27
white 3657 11605 927.1 >21.62
v 4068 5704 393.2 >19.56
b 3452 11054 1278.4 >21.11
u 4683 10142 1083.4 >20.68
uvw1 4478 6075 354.4 >19.96
uvm2 4273 5909 393.3 >19.79
uvw2 3863 5499 393.3 >20.07
------------------------------------------------------------------------
The values quoted above are not corrected for the heavy Galactic
extinction corresponding to the reddening of E(B-V) = 0.22 in the
direction of the burst (Schlegel et al. 1998, ApJS, 500, 525). The
photometry is on the UVOT photometric system described in Poole et al.
(2008, MNRAS, 383, 627).
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