TITLE:   GCN CIRCULAR
NUMBER:  25789
SUBJECT: GRB 190919B: GROND detection of the NIR afterglow
DATE:    19/09/20 02:30:15 GMT
FROM:    Jan Bolmer at MPE/Garching  <jan@bolmer.de>

J. Bolmer (MPE Garching) report: 

We observed the field of GRB 190919B (INTEGRAL trigger 8377; Mereghetti et al. GCN 25788) 
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 23:50 UT on 19 September 2019, 3.6 min after the GRB trigger.
They were performed at an average seeing of 1.31" and at an average airmass of 1.2. We
detect the fading NIR afterglow at the following coordinates and with the following
preliminary AB magnitudes at 407 +/- 194 s after the trigger:

Ra, Dec = 311.87765 -44.69533

J = 16.33 +/- 0.05,
H = 16.06 +/- 0.05,
Ks = 15.92 +/- 0.07.

Given magnitudes are calibrated against 2MASS field stars and are not corrected
for the expected Galactic foreground extinction corresponding to a reddening of
E_(B-V)=0.10 mag in the direction of the burst (Schlafly & Finkbeiner 2011).