GCN Circular 32339
Subject
GRB 220706A, GROND observations
Event
Date
2022-07-07T13:17:52Z (3 years ago)
From
Ana Nicuesa at TLS Tautenburg <ana@tls-tautenburg.de>
A. Nicuesa Guelbenzu, S. Klose (both TLS Tautenburg), and A. Rau (MPE
Garching) report:
We observed the field of GRB 220706A (D�Ai et al., GCN 32329) with
GROND mounted at the 2.2m MPG telescope at La Silla Observatory
(Chile).
Observations started at a midtime of 09:40 UT on July 07, 2022, about
17.5 hours after the GRB trigger and were on target for 20 minutes.
They were performed at an average seeing of 1.2 arcsec and at an
airmass close to 1.0.
Inside the enhanced Swift/XRT error circle (Goad et al., GCN 32333),
we do not detect an optical/NIR transient in any band down to the
following upper limits (AB mags; 3 sigma):
g' > 25.2,
r' > 24.9,
i' > 24.2,
J > 21.7,
H > 21.0,
K > 19.9.
Combining the GROND optical (g'r'i') and NIR (JHK) bands, no object is
detected inside the enhanced XRT error circle either.
Our measurements add to previousely reported results (Gendre et al.,
GCN 32331; Lipunov et al., GCN 32332; Jiang et al., GCN 32335; de
Ugarte-Postigo et al., GCN 32338).
The source at the northern border of the enhanced XRT error circle
reported by de Ugarte Postigo et al. (GCN 32338) is clearly detected
in our combined gri images. At present we cannot decide whether this
is a galaxy or not.
The given limits are derived based on calibrating the optical images
against the Pan-STARRS catalog and the JHK data against 2MASS stars.
We thank Sam Kim for excellent support and for performing the
observations.