[vsnet-grb-info 9157] GRB 100418A: further GROND observations and light curve fit

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10644
SUBJECT: GRB 100418A: further GROND observations and light curve fit
DATE:    10/04/21 19:20:41 GMT
FROM:    Sylvio Klose at TLS Tautenburg  <klose at tls-tautenburg.de>

R. Filgas (MPE Garching), D. A. Kann, S. Klose (all Tautenburg),
M. Nardini, and J. Greiner (all MPE Garching), report on behalf of the GROND 
team:

GROND on La Silla (Greiner et al. 2008, PASP 120, 405)  continues 
observing the afterglow of GRB 100418A.  GROND data, with the first epoch 
at 28 ks after the burst and the last data point at 133 ks after the 
burst, in combination with data from Updike et al. (GCN 10619), Antonelli 
et al. (GCN 10620), Malesani (GCN 10621), Pearson et al. (GCN 10626), 
Malesani et al. (GCN 10631), Rumyantsev et al. (GCN 10634), Bikmaev et al. 
(GCN 10635), Updike et al. (GCN 10637), and Bikmaev et al. (GCN 10643), 
show that the R-band afterglow light curve had a break at t = 1.11 +/- 
0.01 days and is now decaying with a slope of 2.41 +/- 0.08.

While the steep decay of the afterglow is in favor of a SN search, the 
bright host (Malesani, GCN 10621) might make a detection difficult. 
Assuming a SN 1998bw template, a Galactic visual extinction along the line 
of sight of 0.2 mag, no GRB host extinction but 0.2 mag host extinction 
for SN 1998bw, we predict the following SN peak times and magnitudes:

      band         dt/days         mag
      V            21.5           24.5
      R            22.5           23.7
      I            24.0           22.9
      J            29.5           22.8

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