GCN Circular 14815
Subject
GRB 130606A: Skynet/PROMPT detection of the optical afterglow
Date
2013-06-07T20:46:16Z (11 years ago)
From
Adam S. Trotter at UNC-Chapel Hill/PROMPT/Skynet <atrotter@physics.unc.edu>
A. Trotter, A. LaCluyze, D. Reichart, J. Haislip, T. Berger, M. Carroll,
H. T. Cromartie, R. Egger, A. Foster, C. Foster, N. Frank, K. Ivarsen,
D. James, M. Maples, J. Moore, M. Nysewander, E. Speckhard, P. Taylor
and J. A. Crain report:
Skynet observed field of GRB 130606A (Ukwatta et al., GCN 14781, Swift
trigger #557589), using the optical localization of Xu et al. (GCN
14783). It took ~150 160-second exposures in each of the g', R and z'
bands with three 16" telescopes of the PROMPT array at CTIO, Chile,
starting at 2013-06-07, 00:47 UT (t=3.75h post-trigger), and continuing
until t=9.7h.
We detect a fading afterglow in the z' band in most individual
exposures, with z~18.5 at t~6.3h, and an approximate temporal index
alpha~-1.4. We do not detect the afterglow in the R or g' bands in
individual exposures, consistent with the spectroscopic redshift z=5.91
reported by Castro-Tirado et al. (GCN 14796). Stacks of ~70 160-second
exposures at a mean time t~5.7h yield a questionable R~21.9 detection
and a 3-sigma upper limit g'>23.7. Similar stacks at t~8.5h yield
3-sigma upper limits R>22.7 and g'>23.6. A preliminary light curve is at:
http://www.skynet.unc.edu/grb/grb130606a.png
Photometry is calibrated to 10 SDSS stars in the field; g' and z'
magnitudes are in the AB system; R-band magnitudes are in the Vega
system, with the SDSS calibration stars transformed according to Jester
(2005). No correction has been applied for the expected line-of-sight
Milky Way extinction of E(B-V)=0.02 (Schlegel et al. 1998).
Further Skynet observations are scheduled.
