Ground-based and JWST Observations of SN 2022pul: II. Evidence from Nebular Spectroscopy for a Violent Merger in a Peculiar Type-Ia Supernova
Creators: name: Kwok, Lindsey A.
name: Siebert, Matthew R.
name: Johansson, Joel
name: Jha, Saurabh W.
name: Blondin, Stephane
name: Dessart, Luc
name: Foley, Ryan J.
name: Hillier, D. John
name: Larison, Conor
name: Pakmor, Ruediger
name: Temim, Tea
name: Andrews, Jennifer E.
name: Auchettl, Katie
name: Badenes, Carles
name: Barna, Barnabas
name: Bostroem, K. Azalee
name: Newman, Max J. Brenner
name: Brink, Thomas G.
name: Bustamante-Rosell, Maria Jose
name: Camacho-Neves, Yssavo
name: Clocchiatti, Alejandro
name: Coulter, David A.
name: Davis, Kyle W.
name: Deckers, Maxime
name: Dimitriadis, Georgios
name: Dong, Yize
name: Farah, Joseph
name: Filippenko, Alexei V.
name: Flors, Andreas
name: Fox, Ori D.
name: Garnavich, Peter
name: Gonzalez, Estefania Padilla
name: Graur, Or
name: Hambsch, Franz-Josef
name: Hosseinzadeh, Griffin
name: Howell, D. Andrew
name: Hughes, John P.
name: Kerzendorf, Wolfgang E.
name: Saux, Xavier K. Le
name: Maeda, Keiichi
name: Maguire, Kate
name: McCully, Curtis
name: Mihalenko, Cassidy
name: Newsome, Megan
name: O'Brien, John T.
name: Pearson, Jeniveve
name: Pellegrino, Craig
name: Pierel, Justin D. R.
name: Polin, Abigail
name: Rest, Armin
name: Rojas-Bravo, Cesar
name: Sand, David J.
name: Schwab, Michaela
name: Shahbandeh, Melissa
name: Shrestha, Manisha
name: Smith, Nathan
name: Strolger, Louis-Gregory
name: Szalai, Tamas
name: Taggart, Kirsty
name: Terreran, Giacomo
name: Terwel, Jacco H.
name: Tinyanont, Samaporn
name: Valenti, Stefano
name: Vinko, Jozsef
name: Wheeler, J. Craig
name: Yang, Yi
name: Zheng, WeiKang
name: Ashall, Chris
name: DerKacy, James M.
name: Galbany, Lluis
name: Hoeflich, Peter
name: de Jaeger, Thomas
name: Lu, Jing
name: Maund, Justyn
name: Medler, Kyle
name: Morrell, Nidia
name: Shappee, Benjamin J.
name: Stritzinger, Maximilian
name: Suntzeff, Nicholas
name: Tucker, Michael
name: Wang, Lifan
Publisher: name: arXiv
Year: 2023
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We present an analysis of ground-based and JWST observations of SN~2022pul, a peculiar "03fg-like" (or "super-Chandrasekhar") Type Ia supernova (SN Ia), in the nebular phase at 338d post explosion. Our combined spectrum continuously covers 0.4--14 $μ$m and includes the first mid-infrared spectrum of an 03fg-like SN Ia. Compared to normal SN Ia 2021aefx, SN 2022pul exhibits a lower mean ionization state, asymmetric emission-line profiles, stronger emission from the intermediate-mass elements (IMEs) argon and calcium, weaker emission from iron-group elements (IGEs), and the first unambiguous detection of neon in a SN Ia. Strong, broad, centrally peaked [Ne II] line at 12.81 $μ$m was previously predicted as a hallmark of "violent merger'' SN Ia models, where dynamical interaction between two sub-$M_{ch}$ white dwarfs (WDs) causes disruption of the lower mass WD and detonation of the other. The violent merger scenario was already a leading hypothesis for 03fg-like SNe Ia; in SN 2022pul it can explain the large-scale ejecta asymmetries seen between the IMEs and IGEs and the central location of narrow oxygen and broad neon. We modify extant models to add clumping of the ejecta to better reproduce the optical iron emission, and add mass in the innermost region ($&lt; 2000$ km s$^{-1}$) to account for the observed narrow [O I]~$λ\lambda6300$, 6364 emission. A violent WD-WD merger explains many of the observations of SN 2022pul, and our results favor this model interpretation for the subclass of 03fg-like SN Ia.
description: 20 pages, 10 figures, published in ApJ