Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Energetic eruptions leading to a peculiar hydrogen-rich explosion of a massive star

Abstract

Every supernova so far observed has been considered to be the terminal explosion of a star. Moreover, all supernovae with absorption lines in their spectra show those lines decreasing in velocity over time, as the ejecta expand and thin, revealing slower-moving material that was previously hidden. In addition, every supernova that exhibits the absorption lines of hydrogen has one main light-curve peak, or a plateau in luminosity, lasting approximately 100 days before declining1. Here we report observations of iPTF14hls, an event that has spectra identical to a hydrogen-rich core-collapse supernova, but characteristics that differ extensively from those of known supernovae. The light curve has at least five peaks and remains bright for more than 600 days; the absorption lines show little to no decrease in velocity; and the radius of the line-forming region is more than an order of magnitude bigger than the radius of the photosphere derived from the continuum emission. These characteristics are consistent with a shell of several tens of solar masses ejected by the progenitor star at supernova-level energies a few hundred days before a terminal explosion. Another possible eruption was recorded at the same position in 1954. Multiple energetic pre-supernova eruptions are expected to occur in stars of 95 to 130 solar masses, which experience the pulsational pair instability2,3,4,5. That model, however, does not account for the continued presence of hydrogen, or the energetics observed here. Another mechanism for the violent ejection of mass in massive stars may be required.

This is a preview of subscription content

Access options

Buy article

Get time limited or full article access on ReadCube.

$32.00

All prices are NET prices.

Figure 1: Light curves of iPTF14hls.
Figure 2: Spectroscopic sequence of iPTF14hls.
Figure 3: Expansion velocities as a function of time.
Figure 4: The photospheric radius of iPTF14hls.

References

  1. Arcavi, I. Hydrogen-rich core-collapse supernova. In Handbook of Supernovae (eds Alsabti, A. W. & Murdin, P. ) (in the press, Springer, 2016)

  2. Barkat, Z., Rakavy, G. & Sack, N. Dynamics of supernova explosion resulting from pair formation. Phys. Rev. Lett. 18, 379–381 (1967)

    ADS  CAS  Google Scholar 

  3. Heger, A. & Woosley, S. E. The nucleosynthetic signature of population III. Astrophys. J. 567, 532–543 (2002)

    ADS  CAS  Google Scholar 

  4. Woosley, S. E., Blinnikov, S. & Heger, A. Pulsational pair instability as an explanation for the most luminous supernovae. Nature 450, 390–392 (2007)

    ADS  CAS  PubMed  Google Scholar 

  5. Woosley, S. E. Pulsational pair-instability supernovae. Astrophys. J. 836, 244 (2017)

    ADS  Google Scholar 

  6. Law, N. M. et al. The Palomar Transient Factory: system overview, performance and first results. Publ. Astron. Soc. Pacif. 121, 1395–1408 (2009)

    ADS  Google Scholar 

  7. Rau, A. et al. Exploring the optical transient sky with the Palomar Transient Factory. Publ. Astron. Soc. Pacif. 121, 1334–1351 (2009)

    ADS  Google Scholar 

  8. Li, W., Wang, X. & Zhang, T. Spectroscopic classification of CSS141118:092034+504148 as a type II-P supernova. Astron. Telegr. 6898 (2015)

  9. The Planck Collaboration et al. Planck 2015 results. XIII. Cosmological parameters. Astron. Astrophys. 594, A13 (2016)

  10. Popov, D. V. An analytical model for the plateau stage of Type II supernovae. Astrophys. J. 414, 712 (1993)

    ADS  Google Scholar 

  11. Bersten, M. C. & Hamuy, M. Bolometric light curves for 33 type II plateau supernovae. Astrophys. J. 701, 200–208 (2009)

    ADS  CAS  Google Scholar 

  12. Kasen, D. & Bildsten, L. Supernova light curves powered by young magnetars. Astrophys. J. 717, 245–249 (2010)

    ADS  Google Scholar 

  13. Dexter, J. & Kasen, D. Supernova light curves powered by fallback accretion. Astrophys. J. 772, 30 (2013)

    ADS  Google Scholar 

  14. Kirshner, R. P. & Kwan, J. The envelopes of type II supernovae. Astrophys. J. 197, 415 (1975)

    ADS  CAS  Google Scholar 

  15. Eastman, R. G., Schmidt, B. P. & Kirshner, R. The atmospheres of type II supernovae and the expanding photosphere method. Astrophys. J. 466, 911 (1996)

    ADS  CAS  Google Scholar 

  16. Dessart, L. & Hillier, D. J. Distance determinations using type II supernovae and the expanding photosphere method. Astron. Astrophys. 439, 671–685 (2005)

    ADS  CAS  Google Scholar 

  17. Schlegel, E. A new subclass of Type II supernovae? Mon. Not. R. Astron. Soc. 244, 269–271 (1990)

    ADS  CAS  Google Scholar 

  18. Kiewe, M. et al. Caltech Core-Collapse Project (CCCP) observations of type IIn supernovae: typical properties and implications for their progenitor stars. Astrophys. J. 744, 10 (2012)

    ADS  Google Scholar 

  19. Chevalier, R. A., Fransson, C. & Nymark, T. K. Radio and X-ray emission as probes of type IIP supernovae and red supergiant mass loss. Astrophys. J. 641, 1029–1038 (2006)

    ADS  CAS  Google Scholar 

  20. Geha, M. et al. Variability-selected quasars in MACHO Project Magellanic cloud fields. Astrophys. J. 125, 1–12 (2003)

    Google Scholar 

  21. Michel, F. C. Neutron star disk formation from supernova fall-back and possible observational consequences. Nature 333, 644–645 (1988)

    ADS  Google Scholar 

  22. Leonard, D. C. et al. The distance to SN 1999em in NGC 1637 from the expanding photosphere method. Publ. Astron. Soc. Pacif. 114, 35–64 (2002)

    ADS  Google Scholar 

  23. Cao, Y., Nugent, P. E. & Ka sliwal, M. M. Intermediate Palomar Transient Factory: realtime image subtraction pipeline. Publ. Astron. Soc. Pacif. 128, 114502 (2016)

    ADS  Google Scholar 

  24. Shappee, B. J. et al. The man behind the curtain: X-rays drive the UV through NIR variability in the 2013 active galactic nucleus outburst in NGC 2617. Astrophys. J. 788, 48 (2014)

    ADS  Google Scholar 

  25. Drake, A. J. et al. First results from the Catalina Real-time Transient Survey. Astrophys. J. 696, 870–884 (2009)

    ADS  Google Scholar 

  26. Cenko, S. B. et al. The Automated Palomar 60 Inch Telescope. Publ. Astron. Soc. Pacif. 118, 1396–1406 (2006)

    ADS  Google Scholar 

  27. Brown, T. M. et al. Las Cumbres Observatory Global Telescope Network. Publ. Astron. Soc. Pacif. 125, 1031–1055 (2013)

    ADS  Google Scholar 

  28. Huang, F. et al. The photometric system of the Tsinghua-NAOC 80-cm telescope at NAOC Xinglong Observatory. Res. Astron. Astrophys. 12, 1585–1596 (2012)

    ADS  Google Scholar 

  29. Laher, R. R. et al. IPAC image processing and data archiving for the Palomar Transient Factory. Publ. Astron. Soc. Pacif. 126, 674–710 (2014)

    ADS  Google Scholar 

  30. Sullivan, M. et al. Photometric selection of high-redshift type Ia supernova candidates. Astron. J. 131, 960–972 (2006)

    ADS  Google Scholar 

  31. Ahn, C. P. et al. The tenth data release of the Sloan Digital Sky Survey: first spectroscopic data from the SDSS-III Apache Point Observatory Galactic Evolution Experiment. Astrophys. J. Suppl. Ser. 211, 17 (2014)

    ADS  Google Scholar 

  32. Fremling, C. et al. PTF12os and iPTF13bvn. Two stripped-envelope supernovae from low-mass progenitors in NGC 5806. Astron. Astrophys. 593, A68 (2016)

    Google Scholar 

  33. Jenness, T. & Economou, F. ORAC-DR: a generic data reduction pipeline infrastructure. Astron. Comput. 9, 40–48 (2015)

    ADS  Google Scholar 

  34. Valenti, S. et al. The diversity of Type II supernova versus the similarity in their progenitors. Mon. Not. R. Astron. Soc. 459, 3939–3962 (2016)

    ADS  CAS  Google Scholar 

  35. Henden, A. A., Welch, D. L., Terrell, D. & Levine, S. E. The AAVSO Photometric All-Sky Survey (APASS). Am. Astron. Soc. Meet. Abstr. 214, 407.02 (2009)

    ADS  Google Scholar 

  36. Aihara, H. et al. The eighth data release of the Sloan Digital Sky Survey: first data from SDSS-III. Astrophys. J. Suppl. Ser. 193, 29 (2011)

    ADS  Google Scholar 

  37. Ahn, C. P. et al. The ninth data release of the Sloan Digital Sky Survey: first spectroscopic data from the SDSS-III Baryon Oscillation Spectroscopic Survey. Astrophys. J. Suppl. Ser. 203, 21 (2012)

    ADS  Google Scholar 

  38. Chonis, T. S. & Gaskell, C. M. Setting UBVRI photometric zero-points using Sloan Digital Sky Survey ugriz magnitudes. Astrophys. J. 135, 264–267 (2008)

    ADS  CAS  Google Scholar 

  39. Schlafly, E. F. & Finkbeiner, D. P. Measuring reddening with SDSS stellar spectra and recalibrating SFD. Astrophys. J. 737, 103 (2011)

    ADS  Google Scholar 

  40. Foreman-Mackey, D., Hogg, D. W., Lang, D. & Goodman, J. emcee: the MCMC hammer. Publ. Astron. Soc. Pacif. 125, 306–312 (2013)

    ADS  Google Scholar 

  41. Oke, J. B. et al. The Keck Low-Resolution Imaging Spectrometer. Publ. Astron. Soc. Pacif. 107, 375 (1995)

    ADS  Google Scholar 

  42. Faber, S. M. et al. in Instrument Design and Performance for Optical/Infrared Ground-based Telescopes (eds Iye, M. & Moorwood, A. F. M. ) Proc. SPIE 4841, 1657–1669 (2003)

    Google Scholar 

  43. Oke, J. B. & Gunn, J. E. An efficient low resolution and moderate resolution spectrograph for the Hale telescope. Publ. Astron. Soc. Pacif. 94, 586 (1982)

    ADS  CAS  Google Scholar 

  44. Cooper, M. C., Newman, J. A., Davis, M., Finkbeiner, D. P., & Gerke, B. F. spec2d: DEEP2 DEIMOS Spectral Pipeline. Astrophysics Source Code Library ascl:1203.003 (2012)

  45. Newman, J. A. et al. The DEEP2 galaxy redshift survey: design, observations, data reduction, and redshifts. Astrophys. J. 208, 5 (2013)

    Google Scholar 

  46. Yaron, O. & Gal-Yam, A. WISeREP—an interactive supernova data repository. Publ. Astron. Soc. Pacif. 124, 668–681 (2012)

    ADS  Google Scholar 

  47. Howell, D. A. et al. Gemini spectroscopy of supernovae from SNLS: improving high redshift SN selection and classification. Astrophys. J. 634, 1190–1201 (2005)

    ADS  CAS  Google Scholar 

  48. Burrows, D. N. et al. The Swift X-ray telescope. Space Sci. Rev. 120, 165–195 (2005)

    ADS  Google Scholar 

  49. Gehrels, N. et al. The Swift gamma-ray burst mission. Astrophys. J. 611, 1005–1020 (2004)

    ADS  CAS  Google Scholar 

  50. Evans, P. A. et al. An online repository of Swift/XRT light curves of GRBs. Astron. Astrophys. 469, 379–385 (2007)

    ADS  Google Scholar 

  51. Evans, P. A. et al. Methods and results of an automatic analysis of a complete sample of Swift-XRT observations of GRBs. Mon. Not. R. Astron. Soc. 397, 1177–1201 (2009)

    ADS  CAS  Google Scholar 

  52. Willingale, R., Starling, R. L. C., Beardmore, A. P., Tanvir, N. R. & O’Brien, P. T. Calibration of X-ray absorption in our Galaxy. Mon. Not. R. Astron. Soc. 431, 394–404 (2013)

    ADS  Google Scholar 

  53. Margutti, R. et al. Ejection of the massive hydrogen-rich envelope timed with the collapse of the stripped SN2014C. Astrophys. J. 835, 140 (2017)

    ADS  PubMed  PubMed Central  Google Scholar 

  54. Zwart, J. T. L. et al. The Arcminute Microkelvin Imager. Mon. Not. R. Astron. Soc. 391, 1545–1558 (2008)

    ADS  CAS  Google Scholar 

  55. Davies, M. L. et al. Follow-up observations at 16 and 33 GHz of extragalactic sources from WMAP 3-year data: I—spectral properties. Mon. Not. R. Astron. Soc. 400, 984–994 (2009)

    ADS  Google Scholar 

  56. Perrott, Y. C. et al. AMI galactic plane survey at 16 GHz: I—observing, mapping and source extraction. Mon. Not. R. Astron. Soc. 429, 3330–3340 (2013)

    ADS  Google Scholar 

  57. Ostriker, J. P. & Gunn, J. E. On the nature of pulsars. I. Theory. Astrophys. J. 157, 1395 (1969)

    ADS  Google Scholar 

  58. Woosley, S. E. Bright supernovae from magnetar birth. Astrophys. J. 719, L204–L207 (2010)

    ADS  Google Scholar 

  59. Colgate, S. A. Neutron-star formation, thermonuclear supernovae, and heavy-element reimplosion. Astrophys. J. 163, 221 (1971)

    ADS  CAS  Google Scholar 

  60. Serkowski, K., Mathewson, D. L. & Ford, V. L. Wavelength dependence of interstellar polarization and ratio of total to selective extinction. Astrophys. J. 196, 261 (1975)

    ADS  Google Scholar 

  61. Patat, F. & Romaniello, M. Error analysis for dual-beam optical linear polarimetry. Publ. Astron. Soc. Pacif. 118, 146–161 (2006)

    ADS  Google Scholar 

  62. Leonard, D. C. & Filippenko, A. V. Spectropolarimetry of the type II supernovae 1997ds, 1998A, and 1999gi. Publ. Astron. Soc. Pacif. 113, 920–936 (2001)

    ADS  Google Scholar 

  63. Abbott, D. C. & Lucy, L. B. Multiline transfer and the dynamics of stellar winds. Astrophys. J. 288, 679 (1985)

    ADS  CAS  Google Scholar 

  64. Minkowski, R. L. & Abell, G. O. The National Geographic Society—Palomar Observatory Sky Survey. In Basic Astronomical Data: Stars and Stellar Systems (ed. Strand, K. A. ) 481–487 (Univ. Chicago Press, 1963)

  65. Reid, I. N. et al. The second Palomar Sky Survey. Publ. Astron. Soc. Pacif. 103, 661 (1991)

    ADS  Google Scholar 

  66. Ofek, E. O. et al. Precursors prior to type IIn supernova explosions are common: precursor rates, properties, and correlations. Astrophys. J. 789, 104 (2014)

    ADS  Google Scholar 

  67. Ofek, E. O. et al. PTF13efv: an outburst 500 days prior to the SNHunt 275 explosion and its radiative efficiency. Astrophys. J. 824, 6 (2016)

    ADS  Google Scholar 

  68. Fraser, M. et al. SN 2009ip a la PESSTO: no evidence for core-collapse yet. Mon. Not. R. Astron. Soc. 433, 1312–1337 (2013)

    ADS  CAS  Google Scholar 

  69. Bianco, F. B. et al. Monte Carlo method for calculating oxygen abundances and their uncertainties from strong-line flux measurements. Astron. Comput. 16, 54–66 (2016)

    ADS  Google Scholar 

  70. Asplund, M., Grevesse, N., Sauval, A. J. & Scott, P. The chemical composition of the Sun. Annu. Rev. Astron. Astrophys. 47, 481–522 (2009)

    ADS  CAS  Google Scholar 

  71. Alam, S. et al. The eleventh and twelfth data releases of the Sloan Digital Sky Survey: final data from SDSS-III. Astrophys. J. Suppl. Ser. 219, 12 (2015)

    ADS  Google Scholar 

  72. Perley, D. A. et al. A population of massive, luminous galaxies hosting heavily dust-obscured gamma-ray bursts: implications for the use of GRBs as tracers of cosmic star formation. Astrophys. J. 778, 128 (2013)

    ADS  Google Scholar 

  73. Bruzual, G. & Charlot, S. Stellar population synthesis at the resolution of 2003. Mon. Not. R. Astron. Soc. 344, 1000–1028 (2003)

    ADS  Google Scholar 

  74. Nagao, T., Maiolino, R. & Marconi, A. Gas metallicity diagnostics in star-forming galaxies. Astron. Astrophys. 459, 85–101 (2006)

    ADS  CAS  Google Scholar 

  75. Denicoló, G., Terlevich, R. & Terlevich, E. New light on the search for low metallicity galaxies I. The N2 calibrator. Mon. Not. R. Astron. Soc. 330, 69–74 (2002)

    ADS  Google Scholar 

  76. Pettini, M. & Pagel, B. E. J. [O iii]/[N ii] as an abundance indicator at high redshift. Mon. Not. R. Astron. Soc. 348, L59–L63 (2004)

    ADS  CAS  Google Scholar 

  77. Maiolino, R. et al. AMAZE. I. The evolution of the mass-metallicity relation at z>3. Astron. Astrophys. 488, 463–479 (2008)

    ADS  Google Scholar 

  78. Marino, R. A. et al. The O3N2 and N2 abundance indicators revisited: improved calibrations based on CALIFA and Te-based literature data. Astron. Astrophys. 559, A114 (2013)

    Google Scholar 

  79. Kobulnicky, H. A. & Kewley, L. J. Metallicities of 0.3. Astrophys. J. 617, 240–261 (2004)

    ADS  CAS  Google Scholar 

  80. Kewley, L. J. & Dopita, M. A. Using strong lines to estimate abundances in extragalactic H ii regions and starburst galaxies. Astrophys. J. Suppl. Ser. 142, 35–52 (2002)

    ADS  CAS  Google Scholar 

  81. Guillochon, J. et al. An open catalog for supernova data. Astrophys. J. 835, 64 (2017)

    ADS  Google Scholar 

Download references

Acknowledgements

I. Arcavi is an Einstein Fellow. B.S. is a Hubble Fellow and a Carnegie-Princeton Fellow. A.V.F. is a Miller Senior Fellow. See the Supplementary Information for a full list of Acknowledgements.

Author information

Authors and Affiliations

Authors

Contributions

I. Arcavi initiated the study, triggered follow-up observations, reduced data, performed the analysis and wrote the manuscript. D.A.H. is the Principal Investigator of the Las Cumbres Observatory (LCO) Supernova Key Project through which all of the LCO data were obtained; he also assisted with interpretation and the manuscript. D. Kasen and L.B. assisted with theoretical models, data interpretation, and with the manuscript. G.H. and C.McC. assisted with obtaining and reducing LCO data. Z.C.W. first flagged the supernova as interesting. S.R.K. performed the spectral expansion velocity measurements. A.G.-Y. is the Principal Investigator for core-collapse supernovae in iPTF and assisted with interpretation. J.S. and F.T. obtained the Nordic Optical Telescope spectra and polarimetry data and assisted with the manuscript. G.L. reduced the polarimetry data. C.F. reduced the Palomar 60-inch telescope (P60) data. P.E.N. discovered the 1954 eruption image of iPTF14hls, helped obtain the host-galaxy spectrum, and is a Co-Principal Investigator of the Keck proposal under which it and one of the supernova spectra were obtained. A.H. obtained and reduced the Very Large Array (VLA) data and is Principal Investigator of the programme through which the data were obtained. K.M. and C.R. obtained and reduced the Arcminute Microkelvin Imager Large Array (AMI-LA) data. S.B.C. obtained and reduced the Swift X-Ray Telescope (XRT) data. M.L.G. obtained and reduced Keck spectra. D.A.P. performed the host-galaxy analysis and assisted with the manuscript. E.N., O.B., N.J.S. and K.J.S. assisted with theoretical interpretation and the manuscript. E.O.O. helped with interpretation and the manuscript. Y.C. built the real-time iPTF image-subtraction pipeline and obtained Palomar 200-inch telescope (P200) observations. X.W., F.H., L.R., T.Z., W.L., Z.L. and J.Z. obtained and reduced the Xinglong, Lijiang, and Tsinghua University-NAOC telescope (TNT) data. S.V. built the LCO photometric and spectroscopic reduction pipelines and assisted with LCO observations, interpretation, and the manuscript. D.G. assisted with the Palomar Observatory Sky Survey (POSS) image analysis. B.S., C.S.K. and T.W.-S.H. obtained and reduced the All Sky Automated Survey for Supernovae (ASAS-SN) pre-discovery limits. A.V.F. is a Co-Principal Investigator of the Keck proposal under which the host-galaxy spectrum and one of the supernova spectra were obtained; he also helped with the manuscript. R.F. is Principal Investigator of the programme through which the AMI-LA data were obtained. A.N. helped scan for iPTF candidates and assisted with the manuscript. O.Y. is in charge of the iPTF candidate scanning effort. M.M.K. led the work for building iPTF. M.S. wrote the pipeline used to reduce Palomar 48-inch Oschin Schmidt telescope (P48) data. N.B. and R.S.W. obtained P60 SEDM photometry. R.L., D. Khazov, and I. Andreoni obtained P200 observations. R.R.L. contributed to building the P48 image-processing pipeline. N.K. was a main builder of the P60 SEDM. P.W. and B.B. helped build the machine-learning algorithms that identify iPTF supernova candidates.

Corresponding author

Correspondence to Iair Arcavi.

Ethics declarations

Competing interests

The authors declare no competing financial interests.

Additional information

Reviewer Information Nature thanks P. Mazzali, S. Woosley and the other anonymous reviewer(s) for their contribution to the peer review of this work.

Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data figures and tables

Extended Data Figure 1 The discovery and environment of iPTF14hls.

a, SDSS image centered at the position of iPTF14hls. b, Palomar 48-inch deep coadded pre-discovery reference image. c, Palomar 48-inch discovery image of iPTF14hls. d, The result of subtracting the reference image from the discovery image. The position of iPTF14hls is indicated by tick marks in each image.

Extended Data Figure 2 Additional photometry of iPTF14hls.

The bolometric light curve of iPTF14hls (a) deduced from the blackbody fits shows a late-time decline rate that is slower than the radioactive decay of 56Co (black), but consistent with both delayed accretion power (blue; t0 is the onset of accretion at the last peak which could represent a final fallback event) and magnetar spindown power (red; t0 is the formation time of the magnetar, P0 is the initial spin period and B is the magnetic field in this simple analytic model). The magnetar model, however, is not consistent with the luminosity during the first 100 days, as implied by the P48, CSS and Gaia observations (b), unless the early-time magnetar emission is substantially adiabatically degraded. TNT photometry of iPTF14hls and publicly available CSS photometry (retrieved from the CSS website) and Gaia photometry (retrieved from the Gaia Alerts website) not presented in Fig. 1 are shown in b. Data from the P48 (dashed lines) and the LCO 1-m telescope (solid lines) presented in Fig. 1 are shown for comparison. Photometric points from the same day, instrument and filter are averaged for clarity. The B - V (c) and V - I/i (d) colour evolution of iPTF14hls from the LCO 1-m data (filled squares) differs from that of the normal type II-P SN 1999em (empty circles)22, even when contracting the iPTF14hls data by a factor of 10 in time (empty squares) to compensate for the slow evolution observed in its spectra compared to that of normal type II-P supernovae. All error bars, when available, denote 1σ uncertainties.

Source data

Extended Data Figure 3 Pre-explosion nondetection limits for iPTF14hls.

Data from P48 (R band, 3σ nondetections), CSS (unfiltered, obtained via the CSS website), and ASAS-SN (V band, 3σ nondetections—the dark-blue arrow is a deep coadd of the three images taken during the time range denoted by the horizontal line in the marker) are shown. The dashed line indicates the discovery magnitude and the shaded region shows the 1954 outburst magnitude and its uncertainty.

Source data

Extended Data Figure 4 The slow spectral evolution of iPTF14hls compared to normal supernovae.

Weighted average best-fit phase of iPTF14hls spectra from Superfit47, compared to the true spectral phase are shown, when fitting the entire spectrum (black) or only certain line regions as noted. The dashed lines denote constant ratios between the observed and best-fit phases (assuming the explosion happened at discovery). The spectra of iPTF14hls evolve a factor of approximately 6–10 times slower than those of other type II supernovae.

Source data

Extended Data Figure 5 A lack of spectral interaction signatures in iPTF14hls.

The Hα region in our highest-resolution spectrum of iPTF14hls taken on 2016 June 4 using DEIMOS on Keck II (blue), expressed in terms of normalized flux density as a function of rest-frame wavelength (bottom axis), compared to the interaction-powered type IIn SN2005cl18 (red). The top axis is the corresponding velocity of Hα. iPTF14hls shows no signs of the narrow emission or narrow P Cygni features seen in interacting supernovae.

Extended Data Figure 6 The nature of the increased flux during the brightest peak of iPTF14hls.

Spectra of iPTF14hls expressed in terms of normalized flux density as a function of rest-frame wavelength taken on rest-frame day 207 (right before the rise to the brightest peak in the light curve) and day 232 (at the brightest peak in the light curve) after discovery (solid lines) are shown. The similarity of the spectra indicates that the increase of about 50% in luminosity observed in the light curve between the two epochs is equal at all wavelengths. If the increase were due only to the continuum flux, then the line emission on day 232 would have been diluted by the continuum (as simulated by the dashed line).

Extended Data Figure 7 The perplexing velocity evolution of iPTF14hls.

Evolution of the measured velocity gradient in the normal type II-P SN 1999em22 (a) and in iPTF14hls (b) are shown. At a given time, the H-line-forming region is at material expanding with velocity v1, while the Fe-line-forming region is at material expanding with lower velocity v2 (top inset in a). For SN 1999em, the H-line-forming region soon reaches the material expanding at velocity v2 as it moves inward in mass (bottom inset in a) and v2 is measured in the H lines. For iPTF14hls, in contrast, the H-line-forming region does not reach the material expanding at v2 even after the time since discovery increases by a factor of 6. If the material were ejected at the time of discovery, this would indicate an increase in the radius of the line-forming regions by a factor of about 6, which is unlikely given the observed velocity gradient between the H and Fe lines. If the material were ejected before discovery, on the other hand, the relative expansion in radius would be much smaller, thus offering one possible explanation for the constant velocity gradient observed in iPTF14hls.

Extended Data Figure 8 A historic eruption at the position of iPTF14hls.

Blue-filter images of the position of iPTF14hls (marked by blue ticks) from 1954 February 23 (POSS; a) and 1993 January 2 (POSS-II; b) are shown. A source is visible at the position of iPTF14hls in the 1954 image, which is not there in the 1993 image. Using aperture photometry, we find that the 1954 source is 0.31 ± 0.14 mag brighter than the underlying host galaxy at that position, corresponding to a rough outburst magnitude of about −15.6 at the luminosity distance of iPTF14hls, after removing the host-galaxy contribution and calibrating the field to the SDSS u+g bands.

Extended Data Table 1 iPTF14hls host-galaxy line fluxes
Extended Data Table 2 iPTF14hls host-galaxy metallicity values

Supplementary information

Supplementary Information

This file contains the full list of acknowledgements. (PDF 40 kb)

PowerPoint slides

Source data

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Arcavi, I., Howell, D., Kasen, D. et al. Energetic eruptions leading to a peculiar hydrogen-rich explosion of a massive star. Nature 551, 210–213 (2017). https://doi.org/10.1038/nature24030

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1038/nature24030

Further reading

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Search

Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing