[vsnet-grb-info 26642] GRB 201020A: Swift/UVOT Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  28742
SUBJECT: GRB 201020A: Swift/UVOT Observations
DATE:    20/10/22 12:16:21 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18 at psu.edu>

M. H. Siegel (PSU) and E. Ambrosi (INAF-IASFPA)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 201020A
144 s after the BAT trigger (Ambrosi et al., GCN Circ. 28696).
We confirm the fading source initially reported by Ambrosi et al. and
since confirmed by numerous observations (Adachi et al., GCN 
Circ. 28697; Fu  et al., GCN Circ. 28701;  Belkin et al., GCN Circ. 28703,
Pankow et al. GCN Circ. 28708, Kumar et al. GCN Circ. 28711, Paek et al.
GCN Circ. 28713).  The afterglow is not detected in UVOT's NUV filters,
which would be consistent with the redshift of 2.9 reported by Kann et al.
(GCN Circ. 28717).

The preliminary UVOT position is:
   RA  (J2000) =  17:24:54.66 = 261.22773 (deg.)
   Dec (J2000) = +31:25:42.1  =  31.42837 (deg.)
with an estimated uncertainty of 0.44 arc sec. (radius, 90% confidence).

Preliminary detections and 3-sigma upper limits 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 (fc)         145          294          147      18.19+/-0.05
white              583          775           38      19.39+/-0.23
white             9805        10713          885      19.71+/-0.09
white           131168       131712          531            >21.48
v                  632          826           38      17.91+/-0.28
v                21653        22150          485      19.26+/-0.28
v                34473        35292          798      19.86+/-0.29
v               125782       126429          629            >19.99
b                  558          750           38            >19.30
b                22822        23469          630      20.35+/-0.21
b                39219        39998          759      21.05+/-0.36
b               130256       131163          885            >20.60
u (fc)             303          552          245      19.76+/-0.27
u                  706          726           19            >18.42
u                29427        29557          128            >19.69
uvw1               681          876           38            >18.16
uvw1             28521        29420          885            >20.42
uvm2               656          676           19            >17.06
uvm2             27614        28514          885            >20.29
uvw2               608          800           38            >18.04
uvw2             10719        34466         1329            >20.71

The magnitudes in the table 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).