TITLE: GCN CIRCULAR NUMBER: 18567 SUBJECT: GRB 151027A: Hankasalmi optical observations DATE: 15/11/08 09:04:54 GMT FROM: Arto Oksanen at Nyrola Obs., Finland Arto Oksanen (Hankasalmi Obs., Hankasalmi, Finland) reports the following observations of GRB 151027A (Maselli et al. 2015, GCN Circular #18478; Zheng et al. 2015, GCN Circular #18479, and many subsequent Circulars) to the AAVSO High Energy Network: A. Oksanen observed the location of GRB 151027A using the Hankasalmi Observatory 0.4-m Richey-Chretien telescope using an SBIG STL-1001E camera. Time-series images were obtained with both Rc and clear filters, with fifty 60-second frames obtained in each filter. Clear filtered images were obtained between 16:27:07 UT and 22:01:23 UT on 2015 October 27, and Rc-filtered images were obtained between 18:59:58 and 21:45.04 UT. Photometry was performed using an ensemble of comparison stars with APASS photometry available from AAVSO VSP (www.aavso.org/vsp). The afterglow is detected in both Rc- and clear-filtered observations, with evidence of fading between the start and end of the observing run. Photometry of co-added groups of images yields the following: Clear filter: t-t0(d) m(CR) err(CR) 0.5235 16.872 0.030 0.5334 16.816 0.030 0.6531 17.160 0.044 0.6644 17.322 0.047 0.7468 17.575 0.065 Rc filter: t-t0(d) m(R) err(R) 0.6365 17.257 0.058 0.6848 17.544 0.074 0.7353 17.580 0.118 These magnitudes of GRB 151027A are consistent with other magnitudes obtained at similar epochs of this burst (e.g. Hentunen et al. GCN Circular #18503; Sonbas et al. #18518).