[vsnet-grb-info 16989] GRB 150910A: Swift/UVOT Detection of a Brightening Afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18270
SUBJECT: GRB 150910A: Swift/UVOT Detection of a Brightening Afterglow
DATE:    15/09/10 16:11:49 GMT
FROM:    Marissa McCaule at PSU  <marissamc at swift.psu.edu>

L. M. McCauley (PSU) and C. Pagani (U Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 150910A
154 s after the BAT trigger (Pagani et al., GCN Circ. 18264).
A source consistent with the XRT position
(Pagani et al. GCN Circ. 18264)
is detected in the initial UVOT exposures.

The preliminary UVOT position is:
    RA  (J2000) =  00:22:40.11 =   5.66713 (deg.)
    Dec (J2000) = +33:28:21.9  =  33.47274 (deg.)
with an estimated uncertainty of 0.58 arc sec. (radius, 90% confidence).

Preliminary detections using the UVOT photometric system
(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) show a very rapid and steep
rise in the luminosity of the afterglow over the first 1 ks of observation.
Further investigation is strongly encouraged.
Preliminary detections for the early exposures are:


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

white                 153            303         147         19.90
white                 156            303         144         19.93
white                 592            612          19         17.09
white                 765            785          19         16.67
white                 866           1016         147         16.30
v                     135            145           9        >17.23
v                     642            662          19         16.64
v                     815            835          19         16.91
v                    1046           1066          19         16.11
b                     568            588          19         17.56
b                     741            761          19         16.87
u                     312            561         245         18.03
u                     312            561         245         18.02
u                     716            736          19         16.14
uvw1                  692            712          19         16.76
uvw2                 1022           1041          19        >17.97

The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.05 in the direction of the burst
(Schlegel et al. 1998).