Optical Photometric Study of the Type Ia Supernova SN 2019ein

Abstract We present an optical photometric study of the Type Ia supernova SN 2019ein based on B, V, R, and I-band observations obtained with the 1.5-m AZT-22 telescope at the Maidanak Astronomical Observatory, covering -11.6 to +81.4 days relative to B-band maximum. SALT2 fitting gives t_max(B) = 58619.311 MJD (formal error 0.032 d; total uncertainty 0.19 d), x1 = -1.781 ± 0.033, Δm15(B) = 1.43 ± 0.05 mag, and M_max(B) = -18.75 ± 0.22 mag; the epoch of maximum is the zero point of all phases in this work. A joint eight-band early-rise fit gives n = 1.74 ± 0.07 and t_fl = 58603.39 ± 0.24 MJD when the power-law index is free, with t_fl ranging over 58603.39-58604.48 MJD for other early-time cutoffs. Fixing n = 2 for direct comparison with previous fireball-based results gives t_fl = 58602.56 ± 0.07(stat) MJD and a rise time of 16.75 ± 0.07(stat) days, with a 0.17-day sensitivity to the adopted early-time cutoff. The spectra-assisted optical pseudo-bolometric light curve yields L_max = (6.2 ± 1.7) x 10^42 erg/s and a model-dependent 56Ni mass of M_Ni = 0.28 ± 0.08 Msun. From archival spectra we measure a Si II λ6355 velocity of 12,900 ± 400 km/s near maximum, independently confirming the high-velocity classification, and pEW(Si II λ6355) = 122 Å, consistent with the previously reported broad-line character. The intrinsic colours near maximum remain within the normal/transitional range, but their evolution is faster than in the comparison sample. The transitional interpretation rests on the light-curve shape (the decline rate, light-curve morphology, and colour-evolution timing), not on the peak luminosity, whose placement remains limited by host-extinction and pseudo-bolometric systematics.

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