TITLE: GCN CIRCULAR NUMBER: 16143 SUBJECT: GRB 140423A: optical afterglow candidate DATE: 14/04/23 09:32:14 GMT FROM: Alexei Pozanenko at IKI, Moscow L. Elenin (KIAM), A. Volnova (IKI), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed of the field of the Swift GRB 140423A (Sonbas et al., GCN 16142) with 0.4-m telescope of ISON-NM observatory starting on Mar., 20 (UT) 09:01:03. The start of observation was delayed due to bad weather. We took unfiltered images of 30 s exposures. We detect a fading optical source in coordinates (J2000) 13 09 08.50 +49 50 29.4 (with initial accuracy of about 1 arcsec). Preliminary photometry of the source in the first images is ~ 17.2m. the photometry is based on nearby USNO-B1.0 stars (R2 mag). Since the source is absent in USNO-B1.0 catalog and clearly fading we suggest it as GRB 140423A afterglow candidate. [GCN OPS NOTE(23apr14): Please see 16148 for the correction on the start date. Also added the "A" on the GRB name in the first and last sentences.]