[vsnet-grb-info 17332] GRB151215A: Swift/UVOT detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18698
SUBJECT: GRB151215A: Swift/UVOT detection
DATE:    15/12/15 16:28:33 GMT
FROM:    Massimiliano de Pasquale at IASF-Palermo  <m.depasquale at ucl.ac.uk>

M. De Pasquale (UCL-MSSL) and S. L. Gibson (U Leicester)
report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 151215A
174 s after the BAT trigger (Gibson et al., GCN Circ. 18691).
We detect the optical afterglow of GRB151215A within the XRT error
circle (Evans et al. GCN Circ. 18695), in the initial UVOT exposures.

The preliminary UVOT position is:
     RA  (J2000) =  06:14:20.25 =  93.58438 (deg.)
     Dec (J2000) = +35:30:57.4  =  35.51595 (deg.)
with an estimated uncertainty of 0.46 arc sec. (radius, 90% confidence).

The position of this source is consistent with those given by Cenko et al.
(GCN Circ. 18692) and GROND (Wiseman et al. GCN Circ. 18694).

There is no detection in UVOT uv filters, which is congruous with
the redshift z=2.6 of the event (Xu et al., GCN circ. 18696).

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 (Finding Chart)         174          323          147 19.05 ± 0.14
white                         531         2586          362 20.59 ± 0.19
v                             408         2636          253 19.67 ± 0.35
b                             507         2561          233 20.85 ± 0.42
u                             482         2536          233 >20.3
w1                            458         2512          233 >19.9
m2                            433         2651          225 >19.6
w2                            384         2612          253 >19.9

The magnitudes in the table are not corrected for the substantial Galactic
extinction due to the reddening of E(B-V) = 0.39 in the direction of the 
burst
(Schlegel et al. 1998).

-- 

Dr. Massimiliano De Pasquale
Research associate - Swift UVOT scientist
Mullard Space Science Laboratory, University College London