[vsnet-grb-info 15913] GRB 141220A: Swift/UVOT Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17201
SUBJECT: GRB 141220A: Swift/UVOT Detection
DATE:    14/12/20 16:08:45 GMT
FROM:    Frank Marshall at GSFC  <femarsha at khamseen.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) and J. R. Cummings (NASA/UMBC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 141220A
597 s after the BAT trigger (Cummings et al., GCN Circ. 17196).
There were also other exposures when the spacecraft attitude
was not stable.
A source consistent with the optical position
Gorosabel et al. (GCN Circ. 17197)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  13:00:15.76 = 195.06565 (deg.)
    Dec (J2000) = +32:08:47.0  =  32.14639 (deg.)
with an estimated uncertainty of 0.45 arc sec. (radius, 90% confidence).

Preliminary detections using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: 

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white              597          617           19         17.30 ± 0.07
v                  647          839           39         17.65 ± 0.16
b                  573          593           20         17.58 ± 0.13

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.01 in the direction of the burst
(Schlegel et al. 1998).