SN 2023zaw: An Ultrastripped, Nickel-poor Supernova from a Low-mass Progenitor
Abstract
We present SN 2023zaw—a subluminous (M r = ‑16.7 mag) and rapidly evolving supernova (t 1/2,r = 4.9 days), with the lowest nickel mass (≈0.002 M ⊙) measured among all stripped-envelope supernovae discovered to date. The photospheric spectra are dominated by broad He I and Ca near-infrared emission lines with velocities of ∼10,000‑12,000 km s‑1. The late-time spectra show prominent narrow He I emission lines at ∼1000 km s‑1, indicative of interaction with He-rich circumstellar material. SN 2023zaw is located in the spiral arm of a star-forming galaxy. We perform radiation-hydrodynamical and analytical modeling of the lightcurve by fitting with a combination of shock-cooling emission and nickel decay. The progenitor has a best-fit envelope mass of ≈0.2 M ☉ and an envelope radius of ≈50 R ⊙. The extremely low nickel mass and low ejecta mass (≈0.5 M ⊙) suggest an ultrastripped SN, which originates from a mass-losing low-mass He-star (zero-age main-sequence mass < 10 M ⊙) in a close binary system. This is a channel to form double neutron star systems, whose merger is detectable with LIGO. SN 2023zaw underscores the existence of a previously undiscovered population of extremely low nickel mass (<0.005 M ☉) stripped-envelope supernovae, which can be explored with deep and high-cadence transient surveys.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2024
- DOI:
- 10.3847/2041-8213/ad527a
- arXiv:
- arXiv:2403.08165
- Bibcode:
- 2024ApJ...969L..11D
- Keywords:
-
- Core-collapse supernovae;
- Type Ib supernovae;
- Compact binary stars;
- Stellar mass loss;
- Roche lobe overflow;
- 304;
- 1729;
- 283;
- 1613;
- 2155;
- Astrophysics - High Energy Astrophysical Phenomena;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted for publication in ApJL