TITLE: GCN CIRCULAR NUMBER: 16089 SUBJECT: GRB 140408A: GROND Detection of an Afterglow Candidate DATE: 14/04/09 12:58:38 GMT FROM: Jochen Greiner at MPI GRB 140408A: GROND Detection of an Afterglow Candidate K. Varela, C. Delvaux (both MPE Garching), D.A. Kann (TLS Tautenburg), and J. Greiner (MPE Garching) report on behalf of the GROND team: We observed the field of GRB 140408A (Swift trigger 595141; d'Elia et al., GCN #16082) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 405) mounted at the 2.2 m MPG telescope at La Silla Observatory (Chile). Observations started at 06:16:31 UT on 8th April 2014, 0.709 days after the GRB trigger. They were performed at an average seeing of 0".9 and at an average airmass of 1.6. We find a single point source within the 2".2 Swift-XRT error circle reported by Evans et al. (GCN #16085) at RA (J2000.0) = 19h 22m 51.78s Dec. (J2000.0) = -12d 35' 40.9" with an uncertainty of 0".4 in each coordinate. Based on a 7380 s exposure on g'r'i'z' , and a 6000 s exposure in JHK, we estimate preliminary magnitudes (all in AB system) of g' = 25.6 +- 0.3 mag, r' = 23.7 +- 0.2 mag, i' = 22.7 +- 0.2 mag, z' = 22.8 +- 0.3 mag, J > 22.0 mag, H > 21.5 mag, and K > 20.0 mag. We propose this source to be a candidate afterglow for GRB 140408A. At the moment, fading can not be established. If it is the afterglow, the SED suggests a redshift of z ~ 4. Given magnitudes are calibrated against GROND zeropoints as well as 2MASS field stars and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E_(B-V)=0.16 mag in the direction of the burst (Schlafly & Finkbeiner 2011). [GCN OPS NOTE(10apr14): The missing minus sign on the Declination value in the 3rd paragraph was added. Acknowledgement to F.Marshall.]