SN 2022ngb: A faint, slowly evolving Type IIb supernova with a low-mass envelope

Zhao, JW ORCID: 0009-0009-8633-8582, Benetti, S ORCID: 0000-0002-3256-0016, Cai, YZ ORCID: 0000-0002-7714-493X, Pastorello, A ORCID: 0000-0002-7259-4624, Elias-Rosa, N ORCID: 0000-0002-1381-9125, Reguitti, A ORCID: 0000-0003-4254-2724, Valerin, G ORCID: 0000-0002-3334-4585, Wang, ZY ORCID: 0000-0002-0025-0179, Cappellaro, E ORCID: 0000-0001-5008-8619, Feng, GF ORCID: 0009-0000-4301-0573, Fiore, A ORCID: 0000-0002-0403-3331, Fitzpatrick, B ORCID: 0000-0002-5311-9254, Fraser, M ORCID: 0000-0003-2191-1674, Isern, J ORCID: 0000-0002-0819-9574, Kankare, E ORCID: 0000-0001-8257-3512, Kravtsov, T ORCID: 0000-0003-0955-9102, Kumar, B ORCID: 0000-0001-7225-2475, Lundqvist, P ORCID: 0000-0002-3664-8082, Matilainen, K ORCID: 0000-0002-8111-4581, Mattila, S ORCID: 0000-0001-7497-2994 et al (2026) SN 2022ngb: A faint, slowly evolving Type IIb supernova with a low-mass envelope. Astronomy & Astrophysics, 706. ISSN 0004-6361

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Abstract

Context.
Type IIb supernovae (SNe IIb) are stellar explosions whose spectra reveal transitional features between hydrogen-rich (Type II) and helium-rich (Type Ib) SNe. Their progenitors are massive stars that were mostly stripped of their hydrogen envelope, likely through binary interaction and/or strong stellar winds. This makes such stars key tools in studies of the late stages of the evolution of massive stars.

Aims.
We present an extensive photometric and spectroscopic follow-up campaign of the Type IIb SN 2022ngb. Through the detailed modeling of this dataset, we aim to constrain the key physical parameters of the explosion, infer the nature of the progenitor star and its environment, and probe the dynamical properties of the ejecta.

Methods.
We analyzed photometric and spectroscopic data of SN 2022ngb. By constructing and modeling the bolometric light curve with semianalytic models, we were able to estimate the primary explosion parameters. The spectroscopic data were compared with those of well-studied SNe IIb and NLTE models to constrain the properties of the progenitor and the structure of the resulting ejecta.

Results. SN 2022ngb is a low-luminosity SN IIb with a peak bolometric luminosity of LBol = 7.76+1.15−1.00 × 1041 erg s−1 and a V-band rising time of 24.32 ± 0.50 days. The light curve modeling indicates an ejecta mass of ∼2.9−3.2 M⊙, an explosion energy of ∼1.4 × 1051 erg, and a low synthesized 56Ni mass of ∼0.045 M⊙. The nebular phase spectra exhibit asymmetric line profiles, pointing to a nonspherical explosion and an anisotropic distribution of radioactive material. Our analysis reveals a relatively compact stripped-envelope progenitor with a pre-SN mass of approximately 4.7 M⊙ (corresponding to a 15–16 M⊙ZAMS star).

Conclusions.
Our analysis suggests that SN 2022ngb originated from the explosion of a moderate-mass relatively compact, stripped-envelope star in a binary system. The asymmetries inferred from the nebular phase spectral line features indicate the occurrence of a nonspherical explosion.

Item Type:	Article
Uncontrolled Keywords:	5109 Space Sciences; 51 Physical Sciences; 0201 Astronomical and Space Sciences; Astronomy & Astrophysics; 5101 Astronomical sciences; 5107 Particle and high energy physics; 5109 Space sciences
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	EDP Sciences
Date of acceptance:	9 December 2025
Date of first compliant Open Access:	4 March 2026
Date Deposited:	04 Mar 2026 11:12
Last Modified:	04 Mar 2026 11:12
DOI or ID number:	10.1051/0004-6361/202557619
URI:	https://researchonline.ljmu.ac.uk/id/eprint/28182

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