[vsnet-grb-info 16321] GRB 150318A : GROND upper limits

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  17602
SUBJECT: GRB 150318A : GROND upper limits
DATE:    15/03/18 13:14:38 GMT
FROM:    Karla Varela at MPE  <kvarela at mpe.mpg.de>

P. Wiseman, K. Varela, M.Salvato and J. Greiner (all MPE Garching) report
on behalf of the GROND team:

We observed the field of GRB 150318A (SWIFT-635289; Pagani et al.,
GCN#17599) simultaneously in g'r'i'z'JHK with GROND (Greiner et al.
2008,PASP 120, 405) mounted at the 2.2m MPG telescope at ESO La Silla
Observatory (Chile). Observations started on March 18rd, 2015, at 08:27UT,
83 minutes after the GRB trigger. They were performed at an average seeing
of 1.3" and at an average airmass of 2.0.

We do not detect a source inside the 1.9 arcsec error circle reported by
Evans et al. (GCN #17600). Based on a total exposure of 0.67 hours in
g’r'i'z'and 0.73 hours in JHK, we measure the following preliminary upper
limits (AB magnitudes system):

g' > 24.9 mag,
r' > 24.8 mag,
i' > 24.2 mag,
z' > 23.9 mag,
J > 21.4 mag,
H > 20.9 mag, and
K > 18.9 mag.

Given magnitudes are calibrated against GROND zeropoints as well as 2MASS
field stars and are not corrected for the expected Galactic foreground
extinction corresponding to a reddening of E_(B-V) = 0.03 mag in the
direction of the burst (Schlegel et al. 1998).