GCN Circular 18567

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).