TITLE: GCN CIRCULAR NUMBER: 16318 SUBJECT: GRB 140423A: TShAO optical observations DATE: 14/05/22 16:23:31 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Volnova (IKI), A.V. Kusakin (Fesenkov Astrophysical Institute) A.V. Khruslov (INASAN), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the optical afterglow (Elenin et al., GCN 16143; Kaur et al., GCN 16144; Ferrante et al., GCN 16145; Chester et al., GCN 16147; Maehara et al., GCN 16151) of the Swift GRB 140423A (Sonbas et al., GCN 16142) with Zeiss-1000 (East) 1m telescope of Tien Shan Astronomical Observatory on Apr., 23 and Apr., 24. We took several images in R-filter of 300 and 540 s exposures in three epochs. Details of the photometry are following: date UT start t-T0 Filter Exp. OT (mid, days) (s) 2014-04-23 R 15:04:19 0.291036 R 8*300 20.47 0.14 2014-04-23 R 19:04:44 0.450758 R 6*300 20.70 0.20 2014-04-24 R 15:20:01 1.322830 R 12*540 22.17 0.10 The photometry is based on SDSS stars, R (gri -> R transformations by Lupton 2005): SDSS id R J130914.51+494636.5 18.661+/-0.019 J130911.04+494854.6 20.209+/-0.053 J130924.79+494946.6 19.533+/-0.038 The light curve of the afterglow based on our previous an later observations (GCNs 16143, 16148, 16168, 16247, 16264) can be found in http://grb.rssi.ru/GRB140423A/grb140423a-lc.png