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We analyze a KeckI/LRIS nebular spectrum taken 268 days after $B$-bandmaximum 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 riseto peak brightness, possibly the signature of an interaction between the SNejecta and a large ($\gtrsim 20~R_\odot$) nearby, non-degenerate companion. Wesearch for emission signatures of stripped material from a non-degeneratecompanion in the nebular spectrum and find no evidence for any unboundmaterial. We place an upper limit of $< 0.006~M_\odot$ on the amount ofstripped/ablated H-rich material that could go undetected in our spectrum,effectively ruling out all hydrogen-rich donor stars. Additionally, we place amore tentative upper limit on HeI emission in the observed spectrum of$\lesssim 0.02~M_\odot$ which also rules out helium star companions. Our deeplimits rule out a non-degenerate companion as the explanation for theearly-time feature in ASASSN-18bt.

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