TITLE: GCN CIRCULAR NUMBER: 15394 SUBJECT: Swift 575905/GRB 131026A: optical observations DATE: 13/10/28 17:52:28 GMT FROM: Alexei Pozanenko at IKI, Moscow A. Volnova (IKI), R. Inasaridze (AAO), G. Inasaridze (AAO), V. Zhuzhunadze (AAO), Yu. Krugly (IA KhNU), I. Molotov (KIAM), A. Pozanenko (IKI) report on behalf of larger GRB follow-up collaboration: We observed the field of Swift Trigger 575905/GRB 131026A (Cenko et al., GCN 15384) with AS-32 telescope of Abastumani Observatory starting Oct., 26 (UT) 21:06:35. We obtained several unfiltered images with exposures of 180 s. We investigated stacked image and found that both XRT sources (Izzo et al., GCN 15388) coincide with known optical sources, i.e. source 1 (XRT) = SDSS J010222.74+323005.0 (01:02:22.75 +32:30:05.0) source 2 (XRT) = TYC 2281-1221-1 (01 02 02.468 +32 30 01.53) Within BAT error circle (Cenko et al., GCN 15384) we found a point-like source which is not presented in SDSS catalog. Coordinates of the source are (J2000) RA= 01 02 14.64, Dec = +32 30 35.7 with uncertainties of 0.2 arcsec in both coordinates. The details of the photometry of the source are the following: UT start t-T0 Filter Exp. OT UL (3 sigma) (mid, days) (s) 21:06:35 0.64270 None 32x180 21.67 +/- 0.08 22.6 The photometry is based SDSS stars, R (gri -> R transformations by Lupton 2005): SDSS id R(Lupton) J010212.32+323137.9 18.988 J010208.62+323107.7 17.448 J010155.76+322851.8 17.317 We subdivide total number of images in two combined images and compare astrometry and photometry of the two combined images. One can conclude that the upper limit of a proper motion of the source is 3 arcsec per 50 minutes, and one can marginally suggest that brightness of the source is increased at ~0.3m between the two combined images. Finding chart can be found in http://grb.rssi.ru/GRB131026A_Swift_575905/GRB131026A_chart2.png Additional observations in optic and X-ray are encouraged.