Signatures of circumstellar interaction in the Type IIL supernova ASASSN-15oz

K. Azalee Bostroem*, Stefano Valenti, Assaf Horesh, Viktoriya Morozova, N. Paul M. Kuin, Samuel Wyatt, Anders Jerkstrand, David J. Sand, Michael Lundquist, Mathew Smith, Mark Sullivan, Griffin Hosseinzadeh, Iair Arcavi, Emma Callis, Régis Cartier, Avishay Gal-Yam, Lluís Galbany, Claudia Gutiérrez, D. Andrew Howell, Cosimo InserraErkki Kankare, Kristhell Marisol López, Curtis McCully, Giuliano Pignata, Anthony L. Piro, Ósmar Rodríguez, Stephen J. Smartt, Kenneth W. Smith, Ofer Yaron, David R. Young

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


Hydrogen-rich, core-collapse supernovae are typically divided into four classes: IIP, IIL, IIn, and IIb. Recent hydrodynamic modelling shows that circumstellar material is required to produce the early light curves of most IIP/IIL supernovae. In this scenario, IIL supernovae experience large amounts of mass-loss before exploding. We test this hypothesis on ASASSN-15oz, a Type IIL supernova. With extensive follow-up in the X-ray, UV, optical, IR, and radio, we present our search for signs of interaction and the mass-loss history indicated by their detection. We find evidence of short-lived intense mass-loss just prior to explosion from light-curve modelling, amounting in 1.5 M of material within 1800 R of the progenitor. We also detect the supernova in the radio, indicating mass-loss rates of 10−6 to 10−7 M yr−1 prior to the extreme mass-loss period. Our failure to detect the supernova in the X-ray and the lack of narrow emission lines in the UV, optical, and NIR do not contradict this picture and place an upper limit on the mass-loss rate outside the extreme period of <10−4 M yr−1. This paper highlights the importance gathering comprehensive data on more Type II supernovae to enable detailed modelling of the progenitor and supernova which can elucidate their mass-loss histories and envelope structures and thus inform stellar evolution models.

Original languageAmerican English
Pages (from-to)5120-5141
Number of pages22
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - 13 Mar 2019

Bibliographical note

Funding Information:
This work was supported by the Swift Guest Observers Program through grant NNX16AE90G. This work is based (in part) on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere, Chile as part of PESSTO [the Public European Southern Observatory (ESO) Spectroscopic Survey for Transient Objects Survey], ESO program 188.D-3003, 191.D-0935, 197.D-1075. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere under ESO program 095.A-0316(A). We acknowledge support from EU/FP7-ERC (European Research Council) grant [615929]. DAH, GH, and CM are supported by National Science Foundation (NSF) grant AST-1313484. KML acknowledges funding from the European Research Council under ERC Consolidator Grant agreement no. 647208. ALP acknowledges financial support for this research from a Scialog award made by the Research Corporation for Science Advancement. OR acknowledges support by projects IC120009 ‘Millennium Institute of Astrophysics (MAS)’ of the Iniciativa Científica Milenio del Ministerio Economía, Fomento y Turismo de Chile, and CONICYT PAI/INDUSTRIA 79090016. DJS is a visiting astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under contract NNH14CK55B with the National Aeronautics and Space Administration. Research by DJS is supported by NSF grants AST-1821967, 1821987, 1813708, and 1813466.

Funding Information:
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 work uses the National Radio Astronomy Observatory which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. This work makes use of observations from the Las Cumbres Observatory network. This work was partly supported by the United Kingdom Space Agency. Based on observations obtained at the Gemini Observatory through proposal GS-2016A-Q-75-25, acquired through the Gemini Observatory Archive, and processed using the GEMINI IRAF package, 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 Inovac¸ão (Brazil).

Publisher Copyright:
© 2019 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society


  • Outflows
  • Stars: late-type
  • Stars: winds
  • Supernovae: general
  • Supernovae: individual: ASASSN-15oz
  • Techniques: imaging spectroscopy


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