The evolution of luminous red nova AT 2017jfs in NGC 4470

We thank Rubina Kotak for useful suggestions. YZC is supported by the China Scholarship Council (No. 201606040170). MF is supported by a Royal Society - Science Foundation Ireland University Research Fellowship. NER acknowledges support from the Spanish MICINN grant ESP2017-82674-R and FEDER funds. S.Bose, PC and SD acknowledge Project 11573003 supported by NSFC. This research uses data obtained through the Telescope Access Program (TAP), which has been funded by the National Astronomical Observatories of China, the Chinese Academy of Sciences, and the Special Fund for Astronomy from the Ministry of Finance. S. Benetti is partially supported by PRIN-INAF 2017 >Toward the SKA and CTA era: discovery, localization, and physics of transient sources.> (PI: M. Giroletti). KM acknowledges support from STFC (ST/M005348/1) and from H2020 through an ERC Starting Grant (758638). AF acknowledges the support of an ESO Studentship. AMT acknowledges the support from the Program of development of M.V. Lomonosov Moscow State University (Leading Scientific School >Physics of stars, relativistic objects and galaxies>. CT, AdUP, DAK and LI acknowledge support from the Spanish research project AYA2017-89384-P, and from the >Center of Excellence Severo Ochoa> award for the IAA (SEV-2017-0709). CT and AdUP acknowledge support from funding associated to Ramon y Cajal fellowships (RyC-2012-09984 and RyC-2012-09975). DAK and LI acknowledge support from funding associated to Juan de la Cierva Incorporacion fellowships (IJCI-2015-26153 and IJCI-2016-30940). The Pan-STARRS1 Surveys (PS1) have been made possible through contributions of the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, Queen's University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, STScI, NASA under Grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the US NSF under Grant No. AST-1238877, the University of Maryland, and Eotvos Lorand University (ELTE). Operation of the Pan-STARRS1 telescope is supported by NASA under Grant No. NNX12AR65G and Grant No. NNX14AM74G issued through the NEO Observation Program. This paper is also based upon work supported by AURA through the National Science Foundation under AURA Cooperative Agreement AST 0132798 as amended. ATLAS observations were supported by NASA grant NN12AR55G. NUTS is supported in part by the Instrument Center for Danish Astrophysics (IDA). This work is based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 199. D-0143(G,I,K,L). This work makes use of observations from the LCOGT network. It is also based on observations made with the 2.2m MPG telescope at the La Silla Observatory, the Nordic Optical Telescope (NOT), operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias; the 1.82m Copernico Telescope of INAF-Asiago Observatory; the Gran Telescopio Canarias (GTC), installed in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias, in the Island of La Palma; the Liverpool Telescope operated on the island of La Palma by Liverpool John Moores University at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias with financial support from the UK Science and Technology Facilities Council; the 6m Big Telescope Alt-azimuth and the Zeiss-1000 Telescope of the Special Astrophysical Observatory, Russian Academy of Sciences. We thank Las Cumbres Observatory and its staff for their continued support of ASAS-SN. ASAS-SN is supported by the Gordon and Betty Moore Foundation through grant GBMF5490 to the Ohio State University and NSF grant AST-1515927. Development of ASAS-SN has been supported by NSF grant AST-0908816, the Mt. Cuba Astronomical Foundation, the Center for Cosmology and AstroParticle Physics at the Ohio State University, the Chinese Academy of Sciences South America Center for Astronomy (CAS-SACA), the Villum Foundation, and George Skestos.