TITLE: GCN CIRCULAR NUMBER: 20522 SUBJECT: LIGO/Virgo G270580: GMG photometric follow-up of PS17yt DATE: 17/01/25 09:24:59 GMT FROM: Jinzhong Liu at Xinjiang Astronomical Observatory J. Mao (YNAO/CAS), D. Xu (NAO/CAS), J.M. Bai (YNAO/CAS), H.B. Zhao, B. Li (PMO/CAS), J.Z. Liu, H.B. Niu, Y. Zhang, X. Zhang, G.X. Pu, S.G. Ma, T.Z. Yang, F.F. Song (XAO/CAS), T.M. Zhang, X. Zhou, H.X. Feng, Z.P. Zhu (NAO/CAS) report on behalf of the Gravitational Wave Follow-Up Network by NAO-PMO-XAO-YNAO in China (GWFUNC): We observed the transient, PS17yt, in Chambers et al. (GCN 20512) using the Gao-Mei-Gu (GMG) 2.4-m telescope at Lijiang, Yunan, China. The photometric observation began at 18:35:37 UT on 2017-01-24, and 1x600 s imaging was obtained in the Sloan r-filter . The object was well detected with the magnitude of m(r) = 18.76 ¡À 0.04 mag, calibrated with nearby SDSS stars. Together with the previous measurements in GCN 20512, it indicates that the object has been rising relatively slowly, being more consistent with the behavior of early SN Ia than those of other types of early SNe, in agreement with its spectroscopic classification of SN Ia in Castro-Tirado et al. (GCN 20521).