[vsnet-grb-info 13298] GRB 130514A: GROND optical-NIR afterglow discovery and photo-z

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14634
SUBJECT: GRB 130514A: GROND optical-NIR afterglow discovery and photo-z
DATE:    13/05/14 08:40:11 GMT
FROM:    Alexander Kann at TLS Tautenburg  <kann at tls-tautenburg.de>

S. Schmidl, D. A. Kann (both TLS Tautenburg) and J. Greiner (MPE Garching)
report on behalf of the GROND team:

We observed the field GRB 130514A (Swift trigger 555821; E. Sonbas et al.,
GCN 14632) simultaneously in g'r'i'z'JHKs with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla
Observatory (Chile).

Observations started at 07:15:31 UT on May 14th, 2 minutes after the SWIFT
BAT trigger. They were performed at an average seeing of 1" and at an
average airmass of 1.18.

Inside the 2".6 refined XRT error circle, we detect a source not visible
in the DSS or SDSS in all 7 bands. The GROND position for this source is:

RA (J2000)   =  19:45:07.90
Dec.(J2000)  = -07:58:34.4

with an uncertainty of 0".3.

Based on the first  4 min of total exposure we estimate preliminary
magnitudes (all in AB system) of

g' =  22.17 +- 0.09,
r' =  19.98 +- 0.01,
i' =  19.18 +- 0.02,
J  =  17.87 +- 0.03,
H  =  17.26 +- 0.03 and
K  =  16.81 +- 0.03

We propose this source to be the afterglow of GRB 130514A. Additional
evidence is the power-law shape of the SED.

The source shows a strong g'-band dropout, we derive a photometric
redshift of z = 3.6 +/- 0.2, with an additional small line-of-sight
extinction by SMC dust.

Given magnitudes are calibrated against SDSS as well as 2MASS field stars
and are not corrected for the expected Galactic foreground extinction
corresponding to a reddening of E_(B-V)=0.23 mag in the direction of the
burst (Schlegel et al. 1998).