SN 2016dsg: A Thermonuclear Explosion Involving a Thick Helium Shell

A thermonuclear explosion triggered by a helium-shell detonation on carbon-oxygen white dwarf core has been predicted to have strong UV line blanketing at early times due the iron-group elements produced during burning. We present photometric and spectroscopic observations of SN 2016dsg, sub-luminous peculiar Type I consistent with involving thick He shell. With redshift 0.04, $i$-band peak absolute magnitude is derived be around -17.5. The object located far away from its host, an early-type galaxy, suggesting it originated old stellar population. spectra collected after are unusually red, show weak O $\lambda$7773 absorption lines, do not evolve significantly over 30 days. An 9700-10500 \AA detected in near-infrared spectrum likely unburnt helium ejecta. evolution models for sub-Chandrasekhar mass shell, while well described existing models.