TITLE: GCN CIRCULAR NUMBER: 15649 SUBJECT: GRB 131227A: KAIT light curve analysis DATE: 14/01/01 20:55:53 GMT FROM: Weikang Zheng at UC Berkeley WeiKang Zheng, Alexei V. Filippenko, Adam Morgan (UC Berkeley), and S. B. Cenko (NASA/Goddard Space Flight Center) report on behalf of the KAIT GRB team: We analyzed the early time KAIT data of GRB 131227A (Oates et al., GCN 15616). The afterglow is easily detected in our clear and I band images, but not in V band images (single or co-added). After correcting for the large Galactic extinction (A_V = 2.8 mag, A_I = 1.5 mag; Schlegel et al., 2011, ApJ, 737, 103), we found the afterglow had a color of (V - I) > 1.2 mag at early times (~200 s - 900 s). This is consistent with the spectral break around 7600 A reported by Cucchiara & Cenko (GCN 15624), but still not so constraining to say the break is caused by Lyman-alpha. Due to lack of emission below 7600 A (either because of extinction or Lyman-alpha break), we calibrated the KAIT clear image to the i' band. Our preliminary result shows the afterglow decays as a power law with alpha = -0.99. The late time upper limit reported by Kann et al. (GCN 15632) is below the extrapolation of the line. The preliminary light curve can be found at the following link: http://128.32.15.133/kait/grb/131227A/GRB131227A.png