TITLE:   GCN CIRCULAR
NUMBER:  25569
SUBJECT: GRB 190829A: GROND detection of the Optical/NIR Afterglow
DATE:    19/08/30 09:16:48 GMT
FROM:    Ting-Wan Chen at MPE  <jchen@mpe.mpg.de>

T.-W. Chen, J. Bolmer (both MPE Garching), A. Nicuesa Guelbenzu and S.Klose (both TLS Tautenburg) report: 

We observed the field of GRB 190829A (SWIFT trigger 922968; Dichiara et al. GCN 25552) simultaneously in g’r’i’z’JHKs with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at ESO La Silla Observatory (Chile). 

Observations started at 05:41 UT on 30 August 2019, 9.73 hr after the GRB trigger. They were performed at an average seeing of 1.75" and at an average airmass of 1.6. We detect the optical/NIR afterglow  (Xu et al., GCN 25555; Lipunov et al., GCN 25558; Kumar et al., GCN 25560; Heintz et al., GCN 25563; Valeev et al., GCN 25565) at coordinates RA, DEC (J2000) = 2:58:10.51, -8:57:28.1 (+/- 0.3 arcsec) with the following preliminary AB magnitudes:

g’ = 20.30 +/- 0.03,
r’ = 19.34 +/- 0.03,
i’ = 18.77 +/- 0.03,
z’ = 18.21 +/- 0.03,
J = 17.34 +/- 0.06,
H = 16.68 +/- 0.06,
Ks = 16.40 +/- 0.08.

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)=0.04 mag in the direction of the burst (Schlafly & Finkbeiner 2011).

We acknowledge excellent help in obtaining these data from Sam Kim on La Silla.