GCN Circular 13688
Subject
GRB 120819A: GROND afterglow confirmation
Event
Date
2012-08-20T07:29:10Z (14 years ago)
From
Vladimir Sudilovsky at MPE <vsudilov@mpe.mpg.de>
V. Sudilovsky (MPE Garching), S. Klose (TLS Tautenburg), and J. Greiner
(MPE Garching) report on behalf of the GROND team:
We observed the field of GRB 120819A (Swift trigger 531428; Beardmore et
al., GCN 13681) 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 23:46 UT on 2012-08-19, 10.5 hrs after the GRB
trigger. Based on co-added images spanning 2 hours taken at a mean
airmass of 1.3 and seeing of 1.6", we confirm the presence of the NOT
afterglow candidate (Malesani et al., GCN 13683). We derive preliminary
magnitudes (all AB system) of this source:
g' = 23.7 +- 0.1
r' = 23.1 +- 0.1
i' = 22.5 +- 0.1
z' = 22.2 +- 0.1
J = 21.5 +- 0.3
H > 20.2
Ks > 20.1
We note that although these magnitudes do not suggest fading, the large
uncertainties from the USNO calibration used by Malesani et al. do not
preclude this possibility.
The consistency with the enhanced XRT position (Evans et al., GCN
13684), combined with the power-law like SED, confirm that this source
is the afterglow of GRB 120819A.
The g' band detection does not suggest substantial Ly-alpha or dust
effects, implying that the redshift of this burst is likely smaller than
3.0.
The magnitudes are derived based on GROND zeropoints (g'r'i'z') and
2MASS stars (JHK). The magnitudes are not corrected for the expected
Galactic reddening along the line of sight of E_(B-V)= 0.16 mag
(Schlegel et al. 1998).