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

August 2022 • 2022ApJ...934..102D

Authors • Dong, Yize • Valenti, Stefano • Polin, Abigail • Boyle, Aoife • Flörs, Andreas • Vogl, Christian • Kerzendorf, Wolfgang E. • Sand, David J. • Jha, Saurabh W. • Wyrzykowski, Łukasz • Bostroem, K. Azalee • Pearson, Jeniveve • McCully, Curtis • Andrews, Jennifer E. • Benetti, Stefano • Blondin, Stéphane • Galbany, L. • Gromadzki, Mariusz • Hosseinzadeh, Griffin • Howell, D. Andrew • Inserra, Cosimo • Jencson, Jacob E. • Lundquist, Michael • Lyman, J. D. • Magee, Mark • Maguire, Kate • Meza, Nicolas • Srivastav, Shubham • Taubenberger, Stefan • Terwel, J. H. • Wyatt, Samuel • Young, D. R.

Abstract • A thermonuclear explosion triggered by a He-shell detonation on a carbon-oxygen white-dwarf core has been predicted to have strong UV line blanketing at early times due to the iron-group elements produced during He-shell burning. We present the photometric and spectroscopic observations of SN 2016dsg, a subluminous peculiar Type I supernova consistent with a thermonuclear explosion involving a thick He shell. With a redshift of 0.04, the i-band peak absolute magnitude is derived to be around -17.5. The object is located far away from its host, an early-type galaxy, suggesting it originated from an old stellar population. The spectra collected after the peak are unusually red, show strong UV line blanketing and weak O I λ7773 absorption lines, and do not evolve significantly over 30 days. An absorption line around 9700-10500 Å is detected in the near-infrared spectrum and is likely from the unburnt He in the ejecta. The spectroscopic evolution is consistent with the thermonuclear explosion models for a sub-Chandrasekhar-mass white dwarf with a thick He shell, while the photometric evolution is not well described by existing models.

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Jacob Jencson

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