GCN Circular 18227

Subject

GRB 150831B: Swift/UVOT Upper Limits

Event

Date

2015-09-01T20:59:18Z (10 years ago)

From

Frank Marshall at GSFC <femarsha@khamseen.gsfc.nasa.gov>

F. E. Marshall (NASA/GSFC) reports on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150831B
3089 s after the BAT trigger (Marshall et al., GCN Circ. 18215Loading...
 
 ).
No optical afterglow consistent with the refined XRT position
(D'Avanzo et al., GCN Circ. 18222Loading...
 
 ) is detected in the initial UVOT 
exposures. We note that this is a very crowded field.
Preliminary 3-sigma upper limits using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first
finding chart (FC) exposure and subsequent exposures are:

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

white_FC          3089         3239          147         >20.6
v                 3246         3445          197         >18.2
b                 8838         9745          885         >20.3
u                 3861         5659          158         >19.4
w1                3656         3856          197         >19.2
m2                3451         3651          197         >20.2

The magnitudes in the table are not corrected for the large
Galactic extinction in the direction of the burst
(Schlegel et al. 1998).