The long-lived Type IIn SN 2015da: Infrared echoes and strong interaction within an extended massive shell
Full author list: L. Tartaglia, A. Pastorello, J. Sollerman, C. Fransson, S. Mattila, M. Fraser, F. Taddia, L. Tomasella, M. Turatto, A. Morales-Garoffolo, N. Elias-Rosa, P. Lundqvist, J. Harmanen, T. Reynolds, E. Cappellaro, C. Barbarino, A. Nyholm, E. Kool, E. Ofek, X. Gao, Z. Jin, H. Tan, D. J. Sand, F. Ciabattari, X. Wang, J. Zhang, F. Huang, W. Li, J. Mo, L. Rui, D. Xiang, T. Zhang, G. Hosseinzadeh, D. A. Howell, C. McCully, S. Valenti, S. Benetti, E. Callis, A. S. Carracedo, C. Fremling, T. Kangas, A. Rubin, A. Somero and G. Terreran ; In this paper we report the results of the first ~four years of spectroscopic and photometric monitoring of the Type IIn supernova SN 2015da (also known as PSN J13522411+3941286, or iPTF16tu). The supernova exploded in the nearby spiral galaxy NGC 5337 in a relatively highly extinguished environment. The transient showed prominent narrow Balmer lines in emission at all times and a slow rise to maximum in all bands. In addition, early observations performed by amateur astronomers give a very well-constrained explosion epoch. The observables are consistent with continuous interaction between the supernova ejecta and a dense and extended H-rich circumstellar medium. The presence of such an extended and dense medium is difficult to reconcile with standard stellar evolution models, since the metallicity at the position of SN 2015da seems to be slightly subsolar. Interaction is likely the mechanism powering the light curve, as confirmed by the analysis of the pseudo bolometric light curve, which gives a total radiated energy ≳ 1051 erg. Modeling the light curve in the context of a supernova shock breakout through a dense circumstellar medium allowed us to infer the mass of the prexisting gas to be ≂ 8 MO , with an extreme mass-loss rate for the progenitor star ≂ 0.6 MO yr-1, suggesting that most of the circumstellar gas was produced during multiple eruptive events. Near- and mid-infrared observations reveal a fluxexcess in these domains, similar to those observed in SN 2010jl and other interacting transients, likely due to preexisting radiatively heated dust surrounding the supernova. By modeling the infrared excess, we infer a mass ≳ 0.4 × 10-3 MO for the dust. ; The Oskar Klein Centre is funded by the Swedish Research Council. We acknowledge the support of the staff of the Xinglong 2.16 m telescope. This work was partially supported by the Open Project Program of the Key Laboratory of Optical Astronomy, National Astronomical Observatories, Chinese Academy of Sciences. M.F. is supported by a Royal Society – Science Foundation Ireland University Research Fellowship. J.H. acknowledges financial support from the Finnish Cultural Foundation and the Vilho, Yrjö and Kalle Väisälä Foundation of the Finnish Academy of Science and Letters. Research by D.J.S. is supported by NSF grants AST-1821987, AST-1821967, AST-1813708, AST-1813466 and AST-1908972. S.B., L.T.and M.T. are partially supported by the PRIN-INAF 2016 with the project "Towards the SKA and CTA era: discovery, localisation, and physics of transient sources" (PI: M. Giroletti). N E.-R. acknowledges support from the Spanish MICINN grant ESP2017–82674–R and FEDER funds. D.A.H., C.M., and G.H. were supported by NSF AST-1313484 The work of X.W. is supported by the National Natural Science Foundation of China (NSFC grants 11325313, 11633002, and 11761141001), and the National Program on Key Research and Development Project (grant no. 2016YFA0400803). Research by S.V. is supported by NSF grant AST-1813176. J.Z. is supported by the National Natural Science Foundation of China (NSFC, grants 11773067, 11403096), the Youth Innovation Promotion Association of the CAS (grants 2018081), and the Western Light Youth Project. Based on observations collected at: ESO La Silla Observatory under program "Optical & NIR monitoring of bright supernovae with REM" during AOT30. The Gemini Observatory, under program GN– 2016B-Q-57, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovação (Brazil). Tthe Nordic Optical Telescope, operated by the Nordic Optical Telescope Scientific Association and the Gran Telescopio Canarias (GTC), both installed at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofìsica de Canarias, on the island of La Palma (Spain). The Copernico Telescope (Asiago, Italy) operated by INAF – Osservatorio Astronomico di Padova. The 3 m Shane Reflector, located at the Lick Observatory (7281 Mt Hamilton Rd, Mt Hamilton, CA 95140, USA.) owned and operated by the University of California. This work makes use of observations from the Las Cumbres Observatory network of telescopes. We acknowledge the support of the staff of the Li–Jiang 2.4 m telescope (LJT). Funding for the LJT has been provided by the Chinese Academy of Sciences (CAS) and the People's Government of Yunnan Province. The LJT is jointly operated and administrated by Yunnan Observatories and Center for Astronomical Mega–Science, CAS. This research has made use of the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This publication makes use of data products from NEOWISE, which is a project of the Jet Propulsion Laboratory/California Institute of Technology, founded by the Planetary Science Division of the National Aeronautics and Space Administration. This research has made use of the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This research has made use of the NASA/IPAC Infrared Science Archive, which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. Funding for the Sloan Digital Sky Survey (SDSS) has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Aeronautics and Space Administration, the National Science Foundation, the U.S. Department of Energy, the Japanese Monbukagakusho, and the Max Planck Society. The SDSS Web site is http://www.sdss.org/. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. The SDSS is managed by the Astrophysical Research Consortium (ARC) for the Participating Institutions. The Participating Institutions are The University of Chicago, Fermilab, the Institute for Advanced Study, the Japan Participation Group, The Johns Hopkins University, Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, University of Pittsburgh, Princeton University, the United States Naval Observatory, and the University of Washington. The intermediate Palomar Transient Factory project is a scientific collaboration among the California Institute of Technology, Los Alamos National Laboratory, the University of Wisconsin, Milwaukee, the Oskar Klein Center, the Weizmann Institute of Science, the TANGO Program of the University System of Taiwan, and the Kavli Institute for the Physics and Mathematics of the Universe. IRAF is distributed by the National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation. SNOOPY is a package for SN photometry using PSF fitting and/or template subtraction developed by E. Cappellaro. A package description can be found at http:// sngroup.oapd.inaf.it/snoopy.html. FOSCGUI is a graphic user interface aimed at extracting SN spectroscopy and photometry obtained with FOSC-like instruments. It was developed by E. Cappellaro. A package description can be found at http://sngroup.oapd.inaf.it/foscgui.html