Article

Late-time observations of the extraordinary Type II supernova iPTF14hls

J. SollermanThe Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691 Stockholm, SwedenF. TaddiaThe Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691 Stockholm, SwedenI. ArcaviDepartment of Physics, University of California, Santa Barbara, CA, 93106-9530 USAC. FremlingCahill Center for Astrophysics, California Institute of Technology, Pasadena, CA, 91125 USAC. FranssonThe Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691 Stockholm, SwedenJ. BurkeDepartment of Physics, University of California, Santa Barbara, CA, 93106-9530 USAS. B. CenkoAstrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, MA, 20771 USAO. AndersenThe Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691 Stockholm, SwedenI. AndreoniCahill Center for Astrophysics, California Institute of Technology, Pasadena, CA, 91125 USAC. BarbarinoThe Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691 Stockholm, SwedenN. BlagorodovaCahill Center for Astrophysics, California Institute of Technology, Pasadena, CA, 91125 USAT. G. BrinkDepartment of Astronomy, University of California, Berkeley, CA, 94720-3411 USAA. V. FilippenkoDepartment of Astronomy, University of California, Berkeley, CA, 94720-3411 USAA. Gal-YamBenoziyo Center for Astrophysics, Weizmann Institute of Science, Rehovot, 76100 IsraelD. HiramatsuDepartment of Physics, University of California, Santa Barbara, CA, 93106-9530 USAG. HosseinzadehDepartment of Physics, University of California, Santa Barbara, CA, 93106-9530 USAD. A. HowellDepartment of Physics, University of California, Santa Barbara, CA, 93106-9530 USAT. de JaegerDepartment of Astronomy, University of California, Berkeley, CA, 94720-3411 USAR. LunnanThe Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691 Stockholm, SwedenC. McCullyDepartment of Physics, University of California, Santa Barbara, CA, 93106-9530 USAD. A. PerleyAstrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Browlow Hill, Liverpool, L3 5RF UKL. TartagliaThe Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691 Stockholm, SwedenG. TerreranCenter for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, Evanston, IL, 60208 USAS. ValentiDepartment of Physics, University of California, 1 Shields Avenue, Davis, CA, 95616-5270 USAX. WangPhysics Department and Tsinghua Center for Astrophysics (THCA), Tsinghua University, Beijing, 100084 PR China

2018en

ABI

Abstract

Aims. We study iPTF14hls, a luminous and extraordinary long-lived Type II supernova, which lately has attracted much attention and disparate interpretation. Methods . We have presented new optical photometry that extends the light curves up to more than three years past discovery. We also obtained optical spectroscopy over this period, and furthermore present additional space-based observations using Swift and HST. Results. After an almost constant luminosity for hundreds of days, the later light curve of iPTF14hls finally fades and then displays a dramatic drop after about 1000 d, but the supernova is still visible at the latest epochs presented. The spectra have finally turned nebular, and our very last optical spectrum likely displays signatures from the deep and dense interior of the explosion. A high-resolution HST image highlights the complex environment of the explosion in this low-luminosity galaxy. Conclusions. We provide a large number of additional late-time observations of iPTF14hls, which are (and will continue to be) used to assess the many different interpretations for this intriguing object. In particular, the very late (+1000 d) steep decline of the optical light curve is difficult to reconcile with the proposed central engine models. The lack of very strong X-ray emission, and the emergence of intermediate-width emission lines including [S II] that we propose originate from dense, processed material in the core of the supernova ejecta, are also key observational tests for both existing and future models.

Identifiers

DOI: 10.1051/0004-6361/201833689

Citations and references

Cited by 20 references

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