SN 2016ije: An SN 2002es-like Type Ia Supernova Exploded in a Metal-poor and Low-surface Brightness Galaxy

We have conducted photometric and spectroscopic observations of the peculiar Type Ia supernova (SN Ia) 2016ije that was discovered through the Tsinghua-NAOC Transient Survey. This peculiar object exploded in the outskirts of a metal-poor, low-surface brightness galaxy (i.e., M-g= 14.5 mag). Our photometric analysis reveals that SN 2016ije is subluminous (M-B,M-max = -17.65 +/- 0.06 mag) but exhibits relatively broad light curves (Delta m(15)(B)-1.35 +/- 0.14 mag), similar to the behavior of SN 2002es. Our analysis of the bolometric light curve indicates that only 0.14 +/- 0.04 M-circle dot of Ni-56 was synthesized in the explosion of SN 2016ije, which suggests a less energetic thermonuclear explosion when compared to normal SNe Ia, and this left a considerable amount of unburned materials in the ejecta. Spectroscopically, SN 2016ije resembles other SN 2002es-like SNeIa, except that the ejecta velocity inferred from its carbon absorption line (similar to 4500 km s(-1)) is much lower than that from silicon lines (similar to 8300 km s(-1)) at around the maximum light. Additionally, most of the absorption lines are broader than other 02es-like SNe Ia. These peculiarities suggest the presence of significant unburned carbon in the inner region and a wide line-forming region along the line of sight. These characteristics suggest that SN 2016ije might originate from the violent merger of a white dwarf binary system, when viewed near an orientation along the iron-group-element cavity caused by the companion star.

Automated summary

We conducted observations of the peculiar Type Ia supernova 2016ije and found that it is subluminous and exhibits broad light curves, similar to SN 2002es. Our analysis suggests that the explosion of SN 2016ije was less energetic and left a considerable amount of unburned materials in the ejecta. The spectroscopic analysis reveals the presence of significant unburned carbon and a wide line-forming region, indicating a violent merger of a white dwarf binary system.