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arXiv · 1811.09635

No Stripped Companion Material in the Nebular Spectrum of the "Two-Component" Type Ia Supernova ASASSN-18bt

M. A. Tucker·B. J. Shappee·J. P. Wisniewski
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Abstract

We analyze a KeckI/LRIS nebular spectrum taken 268 days after $B$-band maximum of ASASSN-18bt (SN~2018oh), a Type Ia supernova (SN Ia) observed by {\it K2} at the time of explosion. ASASSN-18bt exhibited a two-component rise to peak brightness, possibly the signature of an interaction between the SN ejecta and a large ($\gtrsim 20~R_\odot$) nearby, non-degenerate companion. We search for emission signatures of stripped material from a non-degenerate companion in the nebular spectrum and find no evidence for any unbound material. We place an upper limit of $< 0.006~M_\odot$ on the amount of stripped/ablated H-rich material that could go undetected in our spectrum, effectively ruling out all hydrogen-rich donor stars. Additionally, we place a more tentative upper limit on HeI emission in the observed spectrum of $\lesssim 0.02~M_\odot$ which also rules out helium star companions. Our deep limits rule out a non-degenerate companion as the explanation for the early-time feature in ASASSN-18bt.

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M. A. Tucker, B. J. Shappee, J. P. Wisniewski. 2018-11-23. No Stripped Companion Material in the Nebular Spectrum of the "Two-Component" Type Ia Supernova ASASSN-18bt. https://doi.org/10.3847/2041-8213/ab0286

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