UV properties of the first known surviving companions of Type Ia supernovae
Abstract
The study of Type Ia supernovae (SNe Ia) has undergone a revolution within the last year following the discovery of three extremely unique stars in Gaia's Data Release 2. Their hypervelocities (1000-2500 km/s), atmospheric compositions (predominantly C/O with contributions from Mg, Si, S, and Fe-group elements), inflated radii, and the kinematic association of one of the stars with a known SN remnant are all strong evidence that they are the former white dwarf (WD) secondaries in merging double WD systems in which the primary WD exploded as a SN Ia. While analysis of these paradigm-shifting stars in the optical is ongoing, a complete understanding is currently limited by degeneracies in the effective temperatures, surface gravities, and metal abundances. Near-ultraviolet spectroscopy is crucial to break these degeneracies. Our proposed ultraviolet observations of the brightest of these stars will allow for the derivation of its radius, mass, and bulk atmospheric composition, enabling constraints on the precise nucleosynthetic yields of the nearby explosion that polluted the surviving companion's surface as well as characterization of its current stellar structure. This will enable modeling of the future evolution of these stars, which will facilitate searches for more SN Ia survivors that will answer the decades-old mystery of the nature of SN Ia progenitors.
- Publication:
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HST Proposal
- Pub Date:
- June 2019
- Bibcode:
- 2019hst..prop15871S