TITLE:   GCN CIRCULAR
NUMBER:  9927
SUBJECT: GRB 090715B: Skynet/PROMPT Detections
DATE:    09/09/21 04:34:58 GMT
FROM:    Josh Haislip at U.North Carolina  <haislip@physics.unc.edu>

J. Haislip, D. Reichart, K. Ivarsen, A. LaCluyze, A. Foster, J. Moore, A. 
Oza, M. Schubel, J. Styblova, A. Trotter, J. A. Crain, and M. Nysewander 
report:

Skynet observed the Swift/BAT localization of GRB 090715B (Vetere et al., 
GCN 9668) with three of the 16" PROMPT telescopes at CTIO beginning 3.1 
hours after the trigger in UBRI.

We detect the afterglow (Vetere et al., GCN 9668).  Stacking only images 
that increase the limiting magnitude yields:

mean                                                          1-sig. 
1-sig.
time                                                          sys.    stat.
since                                              cal.       cal.    cal.
trig.  tel.      exp.     fil.  magnitude          stars*     unc.    unc.
(h)              (# x s)                                      (mag)   (mag)

3.4    PROMPT-3  12 x 80  U     > 17.5 (3 sig.)    10 SDSS 7  0.094   0.001
3.8    PROMPT-5  40 x 80  I     19.80 +0.40 -0.29  93 SDSS 7  0.268   0.000
3.8    PROMPT-4  41 x 80  R     20.31 +0.20 -0.17  78 SDSS 7  0.151   0.000
4.0    PROMPT-3  29 x 80  B     > 20.8 (3 sig.)    37 SDSS 7  0.134   0.000

* Transformed using Jester et al., 2005, ApJ, 130, 873.