[vsnet-grb-info 8698] GRB 091127: Swift/UVOT observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10199
SUBJECT: GRB 091127: Swift/UVOT observations
DATE:    09/11/28 05:17:52 GMT
FROM:    Stefan Immler at NASA/GSFC  <stefan.m.immler at nasa.gov>

S. Immler (CRESST/UMCP/GSFC) and Troja (NASA/GSFC/ORAU)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 091127
3219 s after the BAT trigger (Troja et al., GCN Circ. 10191).

We detect the optical afterglow at the refined UVOT position
RA, Dec 36.58288, -18.95239, which is

     RA  (J2000)  02:26:19.89
     Dec (J2000) -18:57:08.63

with an estimated uncertainty of 0.55 arcsec (radius, 90% confidence).
This position is consistent with ground-based optical/IR detections of
the afterglows (Smith et al., GCN 10192; Fugazza et al., GCN 10194;
Updike et al., GCN 10195; Xu et al., GCN 10196; Gorosabel et al.,
GCN 10198). Preliminary magnitudes are reported below.

Filter    T_start(s) T_stop(s)  Exposure(s)   Mag  Err
------------------------------------------------------------------------
white      3219       3369      147.4          16.2 +/- 0.1
v          3375       3575      196.6          17.0 +/- 0.1
uvw1       3785       5600     156.1          15.9 +/- 0.1
uvm2       3580       3780      196.6         15.6 +/- 0.1
-------------------------------------------------------------------------

The values quoted above are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.04 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).