SN 2019ein: a Type Ia supernova likely originated from a sub-Chandrasekhar-mass explosion. Issue 3 (6th October 2022)

• Record Type: Journal Article
• Authors: Xi, Gaobo; Wang, Xiaofeng; Li, Wenxiong; Mo, Jun; Zhang, Jujia; Liu, Jialian; Chen, Zhihao; Filippenko, Alexei V; Zheng, Weikang; Brink, Thomas G; Zhang, Xinghan; Sai, Hanna; Ehgamberdiev, Shuhrat A; Mirzaqulov, Davron; Zhang, Jicheng
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 517:Issue 3(2022)
• Page Start: 4098
• Page End: 4118
• Publication Date: 2022-10-06
• Subjects: supernovae: general -- supernovae: individual (SN 2019ein); Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac2848
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We present extensive optical photometric and spectroscopic observations for the nearby Type Ia supernova (SN Ia) 2019ein, spanning the phases from ∼3 to ∼330 d after the explosion. This SN Ia is characterized by extremely fast expansion at early times, with initial velocities of Si ii and Ca ii being above ∼25 000–30 000 km s −1 . After experiencing an unusually rapid velocity decay, the ejecta velocity dropped to ∼13 000 km s −1 around maximum light. Photometrically, SN 2019ein has a moderate post-peak decline rate (Δ m 15 ( B ) = 1.35 ± 0.01 mag), while being fainter than normal SNe Ia by about 40 per cent (with $M^{\rm max}_{B} \approx -18.71 \pm 0.15$ mag). The nickel mass synthesized in the explosion is estimated to be 0.27–0.31 M⊙ from the bolometric light curve. Given such a low nickel mass and a relatively high photospheric velocity, we propose that SN 2019ein likely had a sub-Chandrasekhar-mass white dwarf (WD) progenitor, M WD ≲ 1.22 M⊙ . In this case, the explosion could have been triggered by a double-detonation mechanism, for which 1D and 2D models with WD mass M WD ≈ 1 M⊙ and a helium shell of 0.01 M⊙ can reasonably produce the observed bolometric light curve and spectra. The predicted asymmetry as a result of double detonation is also favoured by the redshifted Fe ii and Ni ii lines observed in the nebular-phase spectrum. Possible diversity in origin of high velocity SNe Ia is also discussed.