GCN Circular 6674
Subject
GRB 070721A: optical observations
Event
Date
2007-07-27T17:14:46Z (18 years ago)
From
Daniele Malesani at Niels Bohr Inst,Dark Cosmology Center <malesani@astro.ku.dk>
D. Malesani, J.P.U. Fynbo, P.M. Vreeswijk (DARK), I. Ilyn (AIP), report
on behalf of a larger collaboration:
We observed the field of GRB 070721A (Ziaeepour et al., GCN 6639) in two
different epochs, using the NOT and VLT telescopes. Observations were
carried out 0.78 and 1.98 days after the GRB. A bright star (R~17.3) is
close to the XRT position (Evans & Ziaeepour, GCN 6640). Inside the XRT
error circle, we detect a single source at the coordinates (J2000,
against USNO-B1):
RA = 00:12:39.13
Dec = -28:33:00.9
This source does not vary between the two epochs to within 0.2 mag, and
is pointlike under seeing conditions of 0.7". We measure R~22.9 using
VLT instrumental zeropoints (~0.1 mag error). No other sources are seen
inside the XRT error circle down to the limits reported below.
Mean UT T-T0 (d) t_exp (s) Instrument Rlim
--------------------------------------------------
Jul 22.20065 0.78320 4x600 NOT+StanCam 24.0
Jul 23.39637 1.97892 2x180 VLT+FORS2 25.5
T0 = trigger time = Jul 21.41745 UT.
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