Probing the Low-mass End of Core-collapse Supernovae Using a Sample of Strongly-stripped Calcium-rich Type IIb Supernovae from the Zwicky Transient Facility

December 2023 • 2023ApJ...959...12D

Authors • Das, Kaustav K. • Kasliwal, Mansi M. • Fremling, Christoffer • Yang, Sheng • Schulze, Steve • Sollerman, Jesper • Sit, Tawny • De, Kishalay • Tzanidakis, Anastasios • Perley, Daniel A. • Anand, Shreya • Andreoni, Igor • Barbarino, C. • Brudge, K. • Drake, Andrew • Gal-Yam, Avishay • Laher, Russ R. • Karambelkar, Viraj • Kulkarni, S. R. • Masci, Frank J. • Medford, Michael S. • Polin, Abigail • Reedy, Harrison • Riddle, Reed • Sharma, Yashvi • Smith, Roger • Yan, Lin • Yang, Yi • Yao, Yuhan

Abstract • The fate of stars in the zero-age main-sequence (ZAMS) range ≈8-12 M _⊙ is unclear. They could evolve to form white dwarfs or explode as electron-capture supernovae (SNe) or iron core-collapse SNe (CCSNe). Even though the initial mass function indicates that this mass range should account for over 40% of all CCSN progenitors, few have been observationally confirmed, likely due to the faintness and rapid evolution of some of these transients. In this paper, we present a sample of nine Ca-rich/O-poor Type IIb SNe detected by the Zwicky Transient Facility with progenitors likely in this mass range. These sources have a [Ca II] λ λ7291, 7324/[O I] λ λ6300, 6364 flux ratio of ≳2 in their nebular spectra. Comparing the measured [O I] luminosity (≲10³⁹ erg s^-1) and derived oxygen mass (≈0.01 M _⊙) with theoretical models, we infer that the progenitor ZAMS mass for these explosions is less than 12 M _⊙. The ejecta properties (M _ej ≲ 1 M _⊙ and E _kin ~ 10⁵⁰ erg) are also consistent. The low ejecta mass of these sources indicates a class of strongly-stripped SNe that is a transition between the regular stripped-envelope SNe and ultra-stripped SNe. The progenitor could be stripped by a main-sequence companion and result in the formation of a neutron star-main sequence binary. Such binaries have been suggested to be progenitors of neutron star-white dwarf systems that could merge within a Hubble time and be detectable with LISA.

Links

• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2023ApJ...959...12D
• PDF https://iopscience.iop.org/article/10.3847/1538-4357/acfeeb/pdf
• PREPRINT http://arxiv.org/abs/2210.05729
• ELECTR https://doi.org/10.3847%2F1538-4357%2Facfeeb