With the advent of new wide-field, high-cadence optical transient surveys, our understanding of the diversity of core-collapse supernovae has grown tremendously in the last decade. However, the pre-supernova evolution of massive stars, which sets the physical backdrop to these violent events, is theoretically not well understood and difficult to probe observationally. Here we report the discovery of the supernova iPTF 13dqy  = SN 2013fs  a mere 3 h after explosion. Our rapid follow-up observations, which include multiwavelength photometry and extremely early (beginning at 6 h post-explosion) spectra, map the distribution of material in the immediate environment (1015 cm) of the exploding star and establish that it was surrounded by circumstellar material (CSM) that was ejected during the final 1 yr prior to explosion at a high rate, around 10−3 solar masses per year. The complete disappearance of flash-ionized emission lines within the first several days requires that the dense CSM be confined to within 1015 cm, consistent with radio non-detections at 70–100 days. The observations indicate that iPTF 13dqy was a regular type II supernova; thus, the finding that the probable red supergiant progenitor of this common explosion ejected material at a highly elevated rate just prior to its demise suggests that pre-supernova instabilities may be common among exploding massive stars.

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We are grateful to the staff at the various observatories where data were obtained, as well as to N. E. Groeneboom, K. I. Clubb, M. L. Graham, D. Sand, A. A. Djupvik, I. Shivvers, J. C. Mauerhan and A. Waszczak for assistance with observations. We thank E. Waxman for valuable discussions. A.G.-Y.’s group is supported by the EU/FP7 via an ERC grant, the Quantum Universe I-Core programme by the Israeli Committee for planning and budgeting and the ISF; by Minerva and ISF grants; by the Weizmann-UK ‘making connections’ programme; and by Kimmel, ARCHES and Yes awards. D.A.P. acknowledges support from Hubble Fellowship grant HST-HF-51296.01-A awarded by the Space Telescope Science Institute, and from a Marie Curie Individual Fellowship as part of the Horizon 2020 European Union (EU) Framework Programme for Research and Innovation (H2020-MSCA-IF-2014-660113). J.H.G. acknowledges support from an AMBIZIONE grant of the Swiss NSF. E.O.O. is supported by the Arye Dissentshik career development chair, Israel Science Foundation, Minerva, Weizmann-UK, and the I-Core programme. M.M.K. acknowledges support from the National Science Foundation for the GROWTH project funded under Grant No. 1545949. A.V.F.’s research is supported by the Christopher R. Redlich Fund, the TABASGO Foundation, and US NSF grant AST-1211916. Support for I.A. was provided by NASA through the Einstein Fellowship Program, grant PF6-170148. LANL participation in iPTF is supported by the US Department of Energy as part of the Laboratory Directed Research and Development programme. Supernova research at the Oskar Klein Centre is supported by the Swedish Research Council and by the Knut and Alice Wallenberg Foundation. K.M. acknowledges support from a Marie Curie Intra-European Fellowship, within the 7th European Community Framework Programme (FP7). Some data were obtained with the Nordic Optical Telescope, which is operated by the Nordic Optical Telescope Scientific Association at the Observatorio del Roque de los Muchachos, La Palma, Spain. We thank the RATIR project team, the staff of the Observatorio Astronomico Nacional on Sierra San Pedro Martir, and the software support team from Teledyne Scientific and Imaging. RATIR, the automation of the Harold L. Johnson Telescope of the Observatorio Astronomico Nacional and the operation of both are funded through National Aeronautics and Space Administration (NASA) grants NNX09AH71G, NNX09AT02G, NNX10AI27G and NNX12AE66G, CONACyT (INFR-2009-01-122785, CB-2008-101958), UNAM PAPIIT (IN113810 and IG100414) and UCMEXUS-CONACyT. 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 NASA. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Research at Lick Observatory is partially supported by a generous gift from Google. A portion of this work was carried out at the Jet Propulsion Laboratory under a Research and Technology Development Grant, under contract with NASA.

Author information


  1. Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 76100, Israel

    • O. Yaron
    • , A. Gal-Yam
    • , E. O. Ofek
    • , A. Rubin
    • , P. Szabo
    • , N. Sapir
    • , P. M. Vreeswijk
    • , D. Khazov
    •  & M. T. Soumagnac
  2. Division of Physics, Math and Astronomy, California Institute of Technology, 1200 E. California Boulevard, Pasadena, California 91125, USA

    • D. A. Perley
    • , S. R. Kulkarni
    • , M. M. Kasliwal
    •  & Y. Cao
  3. Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark

    • D. A. Perley
  4. School of Physics, Trinity College Dublin, Dublin 2, Ireland

    • J. H. Groh
  5. Racah Institute of Physics, Hebrew University, Jerusalem 91904, Israel

    • A. Horesh
    •  & O. Gnat
  6. The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, 10691 Stockholm, Sweden

    • J. Sollerman
    • , C. Fransson
    •  & F. Taddia
  7. Plasma Physics Department, Soreq Nuclear Research Center, Yavne 81800, Israel

    • N. Sapir
  8. Astrophysics Science Division, NASA Goddard Space Flight Center, Mail Code 661, Greenbelt, Maryland 20771, USA

    • S. B. Cenko
  9. Joint Space-Science Institute, University of Maryland, College Park, Maryland 20742, USA

    • S. B. Cenko
  10. Department of Physics, University of California, 1 Shields Avenue, Davis, California 95616-5270, USA

    • S. Valenti
  11. Las Cumbres Observatory, 6740 Cortona Drive, Suite 102, Goleta, California 93117, USA

    • I. Arcavi
    •  & D. A. Howell
  12. Department of Physics, University of California, Santa Barbara, California 93106-9530, USA

    • I. Arcavi
    •  & D. A. Howell
  13. Department of Astronomy, University of California, Berkeley, California 94720-3411, USA

    • O. D. Fox
    • , P. L. Kelly
    • , P. E. Nugent
    •  & A. V. Filippenko
  14. Computational Research Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Road MS 50B-4206, Berkeley, California 94720, USA

    • P. E. Nugent
  15. Spitzer Science Center, California Institute of Technology, Pasadena, California 91125, USA

    • R. R. Laher
  16. Los Alamos National Laboratory, Mail Stop B244, Los Alamos, New Mexico 87545, USA

    • P. R. Wozniak
  17. Instituto de Astronomía, Universidad Nacional Autonóma de México, Apdo. Postal 70-264, 04510 México DF, México

    • W. H. Lee
  18. Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA

    • U. D. Rebbapragada
  19. Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN, UK

    • K. Maguire
  20. School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, UK

    • M. Sullivan


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O.Y. initiated the study, conducted analysis and wrote the manuscript. D.A.P. is PI of the first-night Keck programme, obtained and reduced the Keck/LRIS spectra, and contributed to the analysis of the early-time data. A.G.-Y. is PI of iPTF early-time SN II studies, managed the project, and contributed to analysis and manuscript preparation. J.H.G. performed modelling and analysis of the early spectra. A.H. is PI of the VLA radio programme, provided radio observations, reduction, and analysis, and contributed to figures and manuscript preparation. E.O.O. contributed to analysis of early-time data, mass-loss estimates, Swift-XRT reductions and manuscript preparation. S.R.K. is PI of PTF and of Palomar and Keck follow-up programmes. J.S. provided NOT spectroscopy and contributed to analysis and manuscript preparation. C.F. contributed to analysis of line profiles, estimates of physical properties, and X-ray and radio data interpretation. A.R. performed analysis of the multiband photometry fits to RW11 shock-cooling models. P.S. performed SBO models and contributed to analysis of X-ray emission. N.S. contributed to analysis of SBO properties, early-time spectral modelling, and X-ray emission. F.T. provided and reduced NOT data. S.B.C. reduced Swift and Palomar 60-inch data, and contributed to spectroscopic reduction and analysis. S.V. provided LCOGT multiband photometry and reduced FTS-FLOYDS spectroscopy. I.A. provided LCOGT multiband photometry and reduced FTS-FLOYDS spectroscopy. D.A.H. is PI of the LCOGT follow-up programme. M.M.K. is a PTF builder and provided APO data. P.M.V. contributed to spectroscopic reductions, analysis and figure preparation. D.K. contributed to analysis of the early flash-ionized spectra and to figure preparation. O.D.F. provided RATIR multiband photometry. Y.C. is a PTF builder and performed spectroscopic observations and reductions. O.G. contributed to radiative-transfer analysis of the early-time emission-line spectra. P.L.K. contributed to Keck-II/DEIMOS spectroscopic reductions. P.E.N. is a PTF builder and contributed to manuscript preparation. A.V.F. provided Keck and Lick data, and edited the manuscript. R.R.L. is a developer of the image reduction pipeline. P.R.W. is a PTF builder, involved with machine-learning development. W.H.L. is PI of the RATIR proposals. U.D.R. is a PTF builder, involved with machine-learning development. K.M. is PI of the WHT ToO spectroscopic time, and performed WHT-ISIS spectroscopic reductions. M.S. is PI of the WHT follow-up effort. M.T.S. is a member of the iPTF human monitoring (scanners) team.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to O. Yaron.

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