2024A&A...691A..90Z

In this paper, we present an extensive analysis of SN 2021 wuf, a transition between Ia-norm and SN 1991T-like supernovae, which exploded at the periphery of the tidal bridge between the pair galaxy NGC 6500 and NGC 6501, at a redshift of z = 0.01. Our observations, ranging from -21 to +276 days relative to the B-band maximum light, reveal that SN 2021wuf exhibits properties akin to normal SNe Ia, with a peak absolute magnitude of M_max(B) ∼ - 19.49 ± 0.10 mag and a post-peak decline rate of Δm₁₅(B) ∼ 1.11 ± 0.06 mag. The peak bolometric luminosity of this SN is estimated as 1.58 × 10⁴³ erg s^–1, corresponding to a ⁵⁶Ni mass of M_Ni ∼ 0.64 ± 0.05 M_⊙. The spectral features, including high-velocity Si IIλ6355 lines, a plateau in the Si IIλ6355 velocity evolution and the nickel-to-iron ratio in the nebular phase, suggest a potential pulsating delayed detonation mechanism. The absence of intermediate-mass elements in the early phase and the high photospheric temperature, as inferred from the line-strength ratio of Si IIλ5972 to Si IIλ6355 (named as R(Si II)), further support this classification.