[vsnet-grb-info 21446] GRB 181213A: Swift/UVOT Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  23545
SUBJECT: GRB 181213A: Swift/UVOT Observations 
DATE:    18/12/18 20:20:49 GMT
FROM:    Mike Siegel at PSU/Swift MOC  <mhs18 at psu.edu>

M. H. Siegel (PSU) and P. A. Evans (U. Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 181213A
2352 s after the BAT trigger (Evans et al., GCN Circ. 23525).  A fading
optical afterglow consistent with initial reports (Lipunov et al., GCN
Circ. 23526, Hu et al., GCN Circ. 23529) was detected in four of UVOT’s
filters. The lack of detection of this bright burst in the bluer filters
would imply a redshift of z > 1.4, which is not inconsistent with the
spectroscopic redshift of z < 2.4 from Heintz et al. (GCN Circ. 23537).

The preliminary UVOT position is:
  RA  (J2000) =  16:33:04.86 = 248.27025 (deg.)
  Dec (J2000) = +78:29:48.7  =  78.49685 (deg.)
with an estimated uncertainty of 0.43 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)        2353         2503          294      17.33+/-0.04
white             2633         2653           19      17.15+/-0.10
white             8535         9061          513      19.03+/-0.07
white            66263        67021          738            >21.71
v                 2683         2703           19            >17.35
v                26217        37929         1168            >20.45
b                 2608         3393           87      17.82+/-0.10
b                 8330        15947          230      19.18+/-0.23
b                65351        82801         1115            >20.39
u                 2584         3318          216      17.25+/-0.06
u                14999        33141         1327      19.69+/-0.10
u                71983        72421          426            >20.32
uvw1              2559         3113          216      17.50+/-0.11
uvw1             14093        32991         2656      20.07+/-0.16
uvw1             71077        71977          885            >19.97
uvm2              2708         2908          196            >19.26
uvm2             19555        32084         2047            >20.84
uvw2              2659         2679           19            >17.50
uvw2             25310        37634         1771            >20.67

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).