Helium-rich superluminous supernovae from the Zwicky transient facility

Lin Yan*, D. A. Perley, S. Schulze, R. Lunnan, J. Sollerman, K. De, Z. H. Chen, C. Fremling, A. Gal-Yam, K. Taggart, T. W. Chen, I. Andreoni, E. C. Bellm, V. Cunningham, R. Dekany, D. A. Duev, C. Fransson, R. R. Laher, M. Hankins, A. Y.Q. HoJ. E. Jencson, S. Kaye, S. R. Kulkarni, M. M. Kasliwal, V. Z. Golkhou, M. Graham, F. J. Masci, A. A. Miller, J. D. Neill, E. Ofek, M. Porter, P. Mróz, D. Reiley, R. Riddle, M. Rigault, B. Rusholme, D. L. Shupe, M. T. Soumagnac, R. Smith, L. Tartaglia, Y. Yao, O. Yaron

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


Helium is expected to be present in the massive ejecta of some hydrogen-poor superluminous supernovae (SLSN-I). However, until now only one event has been identified with He features in its photospheric spectra (PTF10hgi). We present the discovery of a new He-rich SLSN-I, ZTF19aawfbtg (SN2019hge), at z = 0.0866. This event has more than 10 optical spectra at phases from -41 to +103 days relative to the peak, most of which match well with that of PTF10hgi. Confirmation comes from a near-IR spectrum taken at +34 days, revealing He I features with P-Cygni profiles at 1.083 and 2.058 μm. Using the optical spectra of PTF10hgi and SN2019hge as templates, we examined 70 other SLSNe-I discovered by Zwicky Transient Facility in the first two years of operation and found five additional SLSNe-I with distinct He-features. The excitation of He I atoms in normal core-collapse supernovae requires nonthermal radiation, as proposed by previous studies. These He-rich events cannot be explained by the traditional 56Ni mixing model because of their blue spectra, high peak luminosities, and long rise timescales. Magnetar models offer a possible solution since pulsar winds naturally generate high-energy particles, potential sources of nonthermal excitation. An alternative model is the interaction between the ejecta and dense H-poor circumstellar material, which may be supported by observed undulations in the light curves. These six SLSNe-Ib have relatively low-peak luminosities (rest frame Mg = -20.06 ± 0.16).

Original languageEnglish (US)
Article numberL8
JournalAstrophysical Journal Letters
Issue number1
StatePublished - Oct 10 2020

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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  • Optical and NIR spectra of ZTF19aawfbtg (SN2019hge)

    Yan, L. (Creator), Perley, D. A. (Creator), Schulze, S. (Creator), Lunnan, R. (Creator), Sollerman, J. (Creator), De, K. (Creator), Chen, Z. H. (Creator), Fremling, C. (Creator), Gal-Yam, A. (Creator), Taggart, K. (Creator), Chen, T. (Creator), Andreoni, I. (Creator), Bellm, E. C. (Creator), Cunningham, V. (Creator), Dekany, R. (Creator), Duev, D. A. (Creator), Fransson, C. (Creator), Laher, R. R. (Creator), Hankins, M. (Creator), Ho, A. Y. Q. (Contributor), Jencson, J. E. (Creator), Kaye, S. (Creator), Kulkarni, S. R. (Creator), Kasliwal, M. M. (Creator), Golkhou, V. Z. (Creator), Graham, M. (Creator), Masci, F. J. (Creator), Miller, A. A. (Creator), Neill, J. D. (Creator), Ofek, E. (Creator), Porter, M. (Creator), Mróz, P. (Contributor), Reiley, D. (Creator), Riddle, R. (Creator), Rigault, M. (Creator), Rusholme, B. (Creator), Shupe, D. L. (Creator), Soumagnac, M. T. (Creator), Smith, R. (Creator), Tartaglia, L. (Creator), Yao, Y. (Creator) & Yaron, O. (Creator), Centre de Donnees Strasbourg (CDS), 2022


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