No Stripped Companion Material in the Nebular Spectrum of the “Two-Component” Type Ia Supernova ASASSN-18bt
Abstract
We analyze a Keck I/Low Resolution Imager and Spectrograph nebular spectrum taken 268 days after B-band maximum of ASASSN-18bt (SN 2018oh), a Type Ia supernova observed by K2 at the time of explosion. ASASSN-18bt exhibited a two-component rise to peak brightness, possibly the signature of an interaction between the supernova ejecta and a large (≳20 R ⊙) 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 ⊙ 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 He I emission in the observed spectrum of ≲0.02 M ⊙ 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- February 2019
- DOI:
- 10.3847/2041-8213/ab0286
- arXiv:
- arXiv:1811.09635
- Bibcode:
- 2019ApJ...872L..22T
- Keywords:
-
- supernovae: general;
- supernovae: individual: ASASSN-18bt&SN2018oh;
- techniques: spectroscopic;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 7 pages, 4 figures, 1 table, accepted by ApJL