TITLE:   GCN CIRCULAR
NUMBER:  36136
SUBJECT: GRB 240415A: Swift/UVOT Detection
DATE:    24/04/16 13:38:30 GMT
FROM:    Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>

M. H. Siegel (PSU) and M. J. Moss (GSFC)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 240415A
3309 s after the BAT trigger (Moss et al., GCN Circ. 36108). A source consistent
with the XRT position (Beardmore et al., GCN Circ. 36128) and the reported
optical transient (Pankov et al., GCN Circ. 36118, Moskvitin et al., GCN Circ. 36122,
Reguitti et al., GCN Circ. 36123, Schneider et al., GCN Circ. 36124, Aryan et al.,
GCN Circ. 36132) is detected in the initial UVOT exposures.

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             3877         4077          197         19.92 +/- 0.19
v                 4287         4487          197         18.95 +/- 0.28
b                 3672         3872          197        >19.2
u                 3467         5040          332         18.96 +/- 0.18
w1                4698         4897          197        >19.3
m2                4492         4692          197        >19.1
w2                4083         4282          197        >19.5

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.022 in the direction of the burst
(Schlegel et al. 1998).