GCN Circular 3914
Subject
GRB 050904: Possible High-Redshift GRB
Event
Date
2005-09-04T12:04:56Z (21 years ago)
From
Daniel E. Reichart at U.North Carolina <reichart@physics.unc.edu>
J. Haislip, D. Reichart, E. Cypriano, S. Pizzaro, A. LaCluyze, J. Rhoads,
E. Figueredo report on behalf of the UNC team of the FUN GRB Collaboration.
With SOAR, we have continued to image the NIR afterglow (Haislip et al.,
GCN 3913) of GRB 050904 (Cummings et al., GCN 3910) in JHK. Between 3.0
and 7.4 hours after the burst, we measure the temporal index to be -1.20.
At 7.4 hours after the burst, we measure J - K = 1.2 mag, corresponding to
a spectral index of -0.35.
Scaling the i and R limits of Fox et al. (GCN 3912) to 3.0 hours after the
burst, we measure i - J > 1.85 mag and R - J > 3.05 mag, corresponding to
spectral indexes of <-1.90 and <-3.35, respectively.
This is too steep to be explained by even heavy extinction. If
interpretted as dropout, this corresponds to 5.3 < z < 9.0 (calculated
using filter centers).
Further NIR and especially z observations are strongly encouraged.