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arXiv · 1910.05436

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

Wynn V. Jacobson-Galán·Abigail Polin·Ryan J. Foley·Georgios Dimitriadis·Charles D. Kilpatrick·Raffaella Margutti·David A. Coulter·Saurabh W. Jha·David O. Jones·Robert P. Kirshner·Yen-Chen Pan·Anthony L. Piro·Armin Rest·César Rojas-Bravo
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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 Type Ia supernovae (SNe Ia). SN 2016hnk has a fast-rising light curve that is consistent with other Ca-rich transients ($t_r = 15$ d). We determine that SN 2016hnk produced $0.03 \pm 0.01 M_{\odot}$ of ${}^{56}\textrm{Ni}$ and $0.9 \pm 0.3 M_{\odot}$ of ejecta. The photospheric spectra show strong, high-velocity Ca II absorption and significant line blanketing at $λ< 5000$ Angstroms, 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 $0.02 \ M_{\odot}$ helium shell on the surface of a $0.85 \ M_{\odot}$ 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.

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Wynn V. Jacobson-Galán, Abigail Polin, Ryan J. Foley, Georgios Dimitriadis, Charles D. Kilpatrick, Raffaella Margutti, David A. Coulter, Saurabh W. Jha, David O. Jones, Robert P. Kirshner, Yen-Chen Pan, Anthony L. Piro, Armin Rest, César Rojas-Bravo. 2020-05-20. Ca hnk: Calcium-rich Transient SN 2016hnk from the Helium Shell Detonation of a Sub-Chandrasekhar White Dwarf. https://doi.org/10.3847/1538-4357%2Fab94b8

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