TITLE:   GCN CIRCULAR
NUMBER:  11375
SUBJECT: GRB101024A: Swift/UVOT
DATE:    10/10/24 19:21:47 GMT
FROM:    Massimiliano de Pasquale at MSSL-UCL  <mdp@mssl.ucl.ac.uk>

M. De Pasquale (UCL-MSSL) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 101024A
82 s after the BAT trigger (De Pasquale et al., GCN Circ. 11370).
An optical afterglow is detected within the refined XRT error circle
(Beardmore et al., GCN Circ. 11372) in the white filter finding chart.
The same source is detected very marginally in the sum of the following 
white filter exposures. It is not found in any other filter, either
in single and in summed exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Poole et al. 2008, MNRAS, 383, 627) for the first finding chart (FC)
exposure and subsequent exposures are:

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

white_FC         82          232          147      19.4 +/- 0.2
u_FC            294          543          246         >20.3
white           573         6068          413   22.3 +/- 0.6 (2.1 sigma)
v               624         6479          413         >20.0
b               549         5864          413         >20.6
u               294         5659          459         >20.6
w1              673         5454          216         >20.1
m2              648         5249          221         >19.7
w2              599         6274          413         >20.5

The values quoted above are not corrected for the non-negligible Galactic 
extinction due to the reddening of E(B-V) = 0.09 in the direction of the 
burst (Schlegel et al. 1998).