| Title: |
SN 2021foa: The “Flip-flop” Type IIn/Ibn Supernova |
| Authors: |
Farias, D; Gall, C; Narayan, G; Rest, S; Villar, VA; Angus, CR; Auchettl, K; Davis, KW; Foley, RJ; Gagliano, A; Hjorth, J; Izzo, L; Kilpatrick, CD; Perkins, HML; Ramirez-Ruiz, E; Ransome, CL; Sarangi, A; Yarza, R; Coulter, DA; Jones, DO; Khetan, N; Rest, A; Siebert, MR; Swift, JJ; Taggart, K; Tinyanont, S; Wrubel, P; de Boer, TJL; Clever, KE; Dhara, A; Gao, H; Lin, C-C |
| Source: |
The Astrophysical Journal, vol 977, iss 2 |
| Publisher Information: |
eScholarship, University of California |
| Publication Year: |
2024 |
| Collection: |
University of California: eScholarship |
| Subject Terms: |
5109 Space Sciences (for-2020); 51 Physical Sciences (for-2020); 5101 Astronomical Sciences (for-2020); 13 Climate Action (sdg); 0201 Astronomical and Space Sciences (for); 0202 Atomic; Molecular; Nuclear; Particle and Plasma Physics (for); 0306 Physical Chemistry (incl. Structural) (for); Astronomy & Astrophysics (science-metrix); 5107 Particle and high energy physics (for-2020) |
| Description: |
We present a comprehensive analysis of the photometric and spectroscopic evolution of SN 2021foa, unique among the class of transitional supernovae for repeatedly changing its spectroscopic appearance from hydrogen-to-helium-to-hydrogen dominated (IIn-to-Ibn-to-IIn) within 50 days past peak brightness. The spectra exhibit multiple narrow (≈300–600 km s−1) absorption lines of hydrogen, helium, calcium, and iron together with broad helium emission lines with a full width at half-maximum (FWHM) of ∼6000 km s−1. For a steady, wind mass-loss regime, light-curve modeling results in an ejecta mass of ∼8 M ⊙ and circumstellar material (CSM) mass below 1 M ⊙, and an ejecta velocity consistent with the FWHM of the broad helium lines. We obtain a mass-loss rate of ≈2 M ⊙ yr−1. This mass-loss rate is 3 orders of magnitude larger than derived for normal Type II supernovae. We estimate that the bulk of the CSM of SN 2021foa must have been expelled within half a year, about 12 yr ago. Our analysis suggests that SN 2021foa had a helium-rich ejecta that swept up a dense shell of hydrogen-rich CSM shortly after explosion. At about 60 days past peak brightness, the photosphere recedes through the dense ejecta-CSM region, occulting much of the redshifted emission of the hydrogen and helium lines, which results in an observed blueshift (∼−3000 km s−1). Strong mass-loss activity prior to explosion, such as those seen in SN 2009ip-like objects and SN 2021foa as precursor emission, are the likely origin of a complex, multiple-shell CSM close to the progenitor star. |
| Document Type: |
article in journal/newspaper |
| Language: |
unknown |
| Relation: |
qt4g67k1dr; https://escholarship.org/uc/item/4g67k1dr |
| DOI: |
10.3847/1538-4357/ad8cd3 |
| Availability: |
https://escholarship.org/uc/item/4g67k1dr; https://doi.org/10.3847/1538-4357/ad8cd3 |
| Rights: |
CC-BY |
| Accession Number: |
edsbas.DA56883F |
| Database: |
BASE |