Data sources:


6m: BVRc photometry by E.A. Barsukova, V.P. Goranskij and A. Valeev with the Russian 6-m BTA telescope and SCORPIO camera.
Ca: Y. Cao, M.M. Kasliwal, G. Chen, I. Arcavi, Palomar Transient Factory collaboration, ATel No. 7070, 2015.
B7: N. Blagorodnova, R. Kotak, J. Polshaw, M.M. Kasliwal, Y. Cao, A.M. Cody, G.B. Doran, N. Elias-Rosa, M. Fraser, C. Fremling, C. Gonzalez-Fernandez, J. Harmanen, J. Jencson, E. Kankare, R.-P. Kudritzki, S.R. Kulkarni, E. Magnier, I. Manulis, F.J. Masci, S. Mattila, P. Nugent, P. Ochner, A. Pastorello, T. Reynolds, K. Smith, J. Sollerman, F. Taddia, G. Terreran, L. Tomasella, M. Turatto, P.M. Vreeswijk, P. Wozniak, and S. Zaggia, Astrophysical Journal V.834, 107, 2017.
CB: S. Parker, R.A. Koff, J. Brimacombe, V. Martignoni, http://www.cbat.eps.harvard.edu/unconf/followups/J14021678+5426205.html.
CD: Ciprian Dumitru Vintdevara discovery observation with the 8" Orion telescope and CCD of Barlad Observatory, Romania.
CF: Prediscovery C. Frenzi, Flickr, color image.
DH: Prediscovery D. Hartmann, Flickr, color image.
DS: Prediscovery POSS II Kodak IIIaJ image.
It: Prediscovery K. Itagaki, images at http://www.cbat.eps.harvard.edu/unconf/followups/J14021678+5426205.html.
JB: J. Brimacombe, Flickr.
KG: CCD BVRc photometry by B.S. Safonov, D.V. Cherjasov, and O.V. Vozyakova with the SAI Caucasus Mountain Observatory 2.5-m telescope.
LB: J. Gerke, S.M. Adams, C.S. Kochanek, K.Z. Stanek, ATel No.7069, 2015. LBT pre-discovery obseravtions.
TH: Prediscovery T. Hancock, RGB images.
OB: Prediscovery O. Bryzgalov, Flickr, color images.
PF: Prediscovery R. Pfile, Flickr, color image.
RP: Prediscovery P. Pecce, Flickr, color image.
SD: P. Kelly, S. van Dyk, O. Fox, A.V. Filippenko, R. Foley, ATel No.7082, 2015. SDSS pre-discovery observations.
SF: Prediscovery S. Furlong, Flickr, color image.
SO: CCD BVRc photometry by O.I. Spiridonova with the SAO 1-m Zeiss telescope.
SV: T. Szalai, J. Vinko, K. Sarneczky, ATel No. 8891, 2016.
Sw: Swift B,V observations by R. Margutti, ATel No. 7072, 2015.
Vi: J. Vinko, K. Sarneczky, A. Szing, ATel No.7079, 2015.
ZP: Prediscovery Z. Orbanic, Flickr, color image.
47: CCD Rc photometry by A.V. Zharova with the SAI Crimean Station 60-cm Zeiss telescope and CCD Apogee-47p (V = V(47)-0.10).