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

Understand

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.