Ca hnk: The Calcium-rich Transient Supernova 2016hnk from a Helium Shell Detonation of a Sub-Chandrasekhar White Dwarf

Wynn V. Jacobson-Galán, Wynn V. Jacobson-Galán, Wynn V. Jacobson-Galán, Abigail Polin, Abigail Polin, Abigail Polin, Ryan J. Foley, Georgios Dimitriadis, Charles D. Kilpatrick, Raffaella Margutti, Raffaella Margutti, David A. Coulter, Saurabh W. Jha, David O. Jones, Robert P. Kirshner, Yen Chen Pan, Anthony L. Piro, Armin Rest, Armin Rest, César Rojas-Bravo

Research output: Contribution to journalArticle

Abstract

We present observations and modeling of SN 2016hnk, a Ca-rich supernova (SN) that is consistent with being the result of a He-shell double-detonation explosion of a C/O white dwarf. We find that SN 2016hnk is intrinsically red relative to typical thermonuclear SNe and has a relatively low peak luminosity ( M B = -15.4 mag), setting it apart from low-luminosity SNe Ia. SN 2016hnk has a fast-rising light curve that is consistent with other Ca-rich transients (t r = 15 days). We determine that SN 2016hnk produced 0.03 ± 0.01 M o˙ of 56Ni and 0.9 ± 0.3 M o˙ of ejecta. The photospheric spectra show strong, high-velocity Ca ii absorption and significant line blanketing at λ < 5000 Å, making it distinct from typical (SN 2005E-like) Ca-rich SNe. SN 2016hnk is remarkably similar to SN 2018byg, which was modeled as a He-shell double-detonation explosion. We demonstrate that the spectra and light curves of SN 2016hnk are well modeled by the detonation of a 0.02 M⊙ helium shell on the surface of a 0.85 M⊙ C/O white dwarf. This analysis highlights the second observed case of a He-shell double-detonation and suggests a specific thermonuclear explosion that is physically distinct from SNe that are defined simply by their low luminosities and strong [Ca ii] emission.

Original languageEnglish (US)
Article number165
JournalAstrophysical Journal
Volume896
Issue number2
DOIs
StatePublished - Jun 20 2020

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Jacobson-Galán, W. V., Jacobson-Galán, W. V., Jacobson-Galán, W. V., Polin, A., Polin, A., Polin, A., Foley, R. J., Dimitriadis, G., Kilpatrick, C. D., Margutti, R., Margutti, R., Coulter, D. A., Jha, S. W., Jones, D. O., Kirshner, R. P., Pan, Y. C., Piro, A. L., Rest, A., Rest, A., & Rojas-Bravo, C. (2020). Ca hnk: The Calcium-rich Transient Supernova 2016hnk from a Helium Shell Detonation of a Sub-Chandrasekhar White Dwarf. Astrophysical Journal, 896(2), [165]. https://doi.org/10.3847/1538-4357/ab94b8