[vsnet-grb-info 9129] GRB 100418A: GROND observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10616
SUBJECT: GRB 100418A: GROND observations
DATE:    10/04/19 06:01:52 GMT
FROM:    Sylvio Klose at TLS Tautenburg  <klose at tls-tautenburg.de>

GROND (Greiner et al. 2008, PASP 120, 405), the 7-channel imager mounted 
at the 2.2m ESO/MPI telescope at La Silla Observatory (Chile), started 
follow-up observations of GRB 100418A (Marshall et al. 2010, GCN 10612) on 
Apr 19, at 4:50 UT (about 7.5 hrs after the burst).

Within the enhanced XRT 1.9 arcsec error circle reported by Osborne et al. 
(GCN 10614) we find a fading point source at coordinates RA, DEC (J2000) =

17:05:27.09,
11:27:42.3

with an uncertainty of 0.5" in each coordinate and estimate the following 
preliminary magnitudes (in the AB system):

g' = 19.2 +- 0.1 
r' = 18.8 +- 0.1
i' = 18.4 +- 0.1
z' = 18.1 +- 0.1
J  = 17.7 +- 0.1

Given magnitudes are calibrated against SDSS field stars and are not 
corrected for the expected Galactic foreground extinction corresponding to 
a reddening of E_(B-V)=0.07 mag in the direction of the burst (Schlegel et 
al. 1998).