[vsnet-grb-info 13319] GRB 130515A: GROND Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  14655
SUBJECT: GRB 130515A: GROND Observations
DATE:    13/05/15 06:01:37 GMT
FROM:    Sebastian Schmidl at TLS Tautenburg  <schmidl 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 of the short GRB 130515A (Swift trigger 555880;
Malesani et al., GCN 14650) 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 as soon as the position became visible above the
pointing limit, at 02:12:08 UT on May 15th, 51 minutes after the BAT
trigger. They were performed at an average seeing of 1".6 and at an
average airmass of 2.4.

Inside the 2".9 SPER XRT error circle (RA = 18:53:45.79, Dec.
-54:16:45.2), we detect a faint source, and additionally a significantly
brighter, possibly extended source on the western edge of the XRT error
circle.

We find the following positions (J2000) for these sources:
In the error circle: RA = 18:53:45.79, Dec. = -54:16:47.3
On the western edge: RA = 18:53:45.24, Dec. = -54:16:44.5
with an error of 0".5 in each case.

Based on an observation with 780 s integration time in g'r'i'z' and 720 s
integration time in JHK, centered at 0.043586 days after the trigger, we
estimate preliminary magnitudes 3-sigma upper limits (all in AB system) of

g' > 23.86,
r' = 22.55 +/- 0.15,
z' = 21.17 +/- 0.11,
J  = 19.74 +/- 0.27,
H  > 19.4 and
K  > 19.1

for the object inside the error circle, and

g' = 22.12 +/- 0.08.,
r' = 20.68 +/- 0.03.,
z' = 19.51 +/- 0.03.,
J  = 18.50 +/- 0.09,
H  = 18.45 +/- 0.14 and
K  = 18.47 +/- 0.17

for the possible galaxy on the western edge.

Given magnitudes are calibrated against GROND zero points (g'r'i'z') as
well as 2MASS field stars (JHK) 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).