[AAVSO-HEN] GRB 090926A: Skynet/PROMPT Observations of Day 4 - 6 Fading Rate

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
For an archive and more information on circulars visit:
http://lheawww.gsfc.nasa.gov/docs/gamcosray/legr/bacodine/gcn3_archive.html

TITLE:   GCN CIRCULAR
NUMBER:  9984
SUBJECT: GRB 090926A: Skynet/PROMPT Observations of Day 4 - 6 Fading Rate
DATE:    09/10/03 20:49:13 GMT
FROM:    Josh Haislip at U.North Carolina  <haislip at 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 has continued to observe the afterglow (Haislip et al., GCN 9937) of 
GRB 090926A (Bissaldi, GCN 9933) with four of the 16" PROMPT telescopes at 
CTIO in BVRI.

After peaking in brightness approximately 1 day after the trigger (Haislip 
et al., GCN 9953), the afterglow had been fading with a power-law index of 
approximately -1.4 until approximately 4 days after the trigger (Haislip, 
et al., GCN 9982).

Between 4 and 6 days after the trigger, the afterglow has been fading with 
a shallower power-law index of approximately -0.8.

At 6.1 days after the trigger, its magnitude is R = 20.40 +0.11 -0.10 
(statistical) +/-  0.57 (systematic; calibrated to 172 USNO B1 stars).

Skynet's most recent BVRI light curve, calibrated to USNO B1 and NOMAD 
stars, can be found here:

http://skynet.unc.edu/grb/grb090926a.jpg