[vsnet-grb-info 8795] GRB 091221: Skynet/PROMPT Detections

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10294
SUBJECT: GRB 091221: Skynet/PROMPT Detections
DATE:    09/12/23 22:11:00 GMT
FROM:    Josh Haislip at U.North Carolina  <haislip at physics.unc.edu>

J. Haislip, D. Reichart, K. Ivarsen, A. LaCluyze, R. Egger, 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 091221 (Palmer et al., 
GCN 10283) with four of the 16" PROMPT telescopes at CTIO beginning 4.3 
hours after the trigger in BVRI.

We detect the afterglow (Palmer et al., GCN 10283; Zheng et al., GCN 
10284).  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)

4.9   PROMPT-5 44 x 80  I    > 21.1 (3 sigma)  143 USNO B1 0.338  0.000
            + 1 x 40
4.9   PROMPT-4 42 x 80  R    21.49 +0.27 -0.22 139 USNO B1 0.362  0.000
4.9   PROMPT-3 41 x 80  B    > 21.5 (3 sigma)  82 USNO B1  0.154  0.000
4.9   PROMPT-1 41 x 80  V    21.41 +0.42 -0.31 27 NOMAD    0.193  0.000
7.3   PROMPT-3 136 x 80 B    > 22.1 (3 sigma)  79 USNO B1  0.153  0.000
7.3   PROMPT-5 134 x 80 I    > 21.8 (3 sigma)  120 USNO B1 0.337  0.000
7.3   PROMPT-4 139 x 80 R    22.44 +0.38 -0.28 112 USNO B1 0.392  0.000
7.4   PROMPT-1 145 x 80 V    > 22.0 (3 sigma)  28 NOMAD    0.112  0.000