{
  "bibcode": "2013GCN.15080....1V",
  "body": "K. Varela (MPE Garching), A.C. Updike (Roger Williams University),\nJ. Elliott (MPE Garching), J. Greiner (MPE Garching) and\nD.A. Kann (TLS Tautenburg) report on behalf of the GROND team:\n\nWe observed the field of GRB 130623A (Cummings et al., GCN #14921)\nsimultaneously in g'r'i'z'JHKs with GROND (Greiner et al. 2008,\nPASP 120, 405) mounted at the 2.2 m MPG/ESO telescope at La Silla\nObservatory (Chile).\n\nThe first epoch observation started at 09:15 UT on 25 June 2013,\n33.7 hrs after the GRB trigger. They were performed at an average\nseeing of 1.\"5 and at an average airmass of 1.6. We find a single\npoint source at the edge of the 4.\"5 Swift-XRT error circle reported\nby Grupe et al. (GCN #14926) at\n\nRA  (J2000.0) = 01:23:26.17 = 20.859063\nDEC (J2000.0) = -77:46:24.0 = -77.773361\n\nwith an uncertainty of 0.3\" in each coordinate.\n\nBased on a total exposure of 50 minutes in g'r'i'z' and 40 minutes in JHK,\nwe estimate preliminary magnitudes (all in AB) of\n\ng' = 22.5 +/- 0.1 mag,\nr' = 22.4 +/- 0.1 mag,\ni' = 22.2 +/- 0.1 mag,\nz' = 21.9 +/- 0.1 mag,\nJ = 21.3 +/- 0.3 mag,\nH = 20.5 +/- 0.3 mag, and\nK > 20.2 mag.\n\nThe second epoch observations started at 08:29 UT on 05 August 2013,\n42 days after the GRB trigger. They were performed at an average seeing of\n1.\"3 and at an average airmass of 1.5. The source found in the first epoch\nis not detected anymore: Based on a total exposure of 75 minutes in g'r'i'z'\nand 60 minutes in JHK, we estimate preliminary upper limits (all in AB) of\n\ng'  > 25.7\nr'  > 25.2\ni'  > 24.3\nz'  > 24.0\nJ  > 21.8\nH  > 20.9\nKs > 20.4\n\nThe fading by nearly 3 mag in the r'-band  proves it to have been the\nafterglow of GRB 130623A. The clear detection down to the g'-band\nimplies a redshift smaller than 3.\n\nGiven magnitudes are calibrated against GROND zeropoints as well as 2MASS\nfield stars and are not corrected for the expected Galactic foreground\nextinction corresponding to a reddening of E_(B-V)=0.05 mag in the\ndirection of the burst (Schlegel et al. 1998).",
  "circularId": 15080,
  "createdOn": 1375864534000,
  "email": "kvarela@mpe.mpg.de",
  "subject": "GRB 130623A: GROND detection of the optical/NIR afterglow",
  "submitter": "Karla Varela at MPE  <kvarela@mpe.mpg.de>",
  "eventId": "GRB 130623A"
}