Optical Spectroscopy and Temporal Evolution of the Nova V1405 Cas

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Abstract
This paper presents the findings from our study of nova V1405 Cas over the first 1051 days after the outburst. The study includes an analysis of the photometric light-curve evolution, along with a detailed spectroscopic analysis. Photometric analysis shows that the nova is a very slow nova, with a decline timescale of t 2 ≈ 165 days. The mass of the white dwarf (WD) is calculated as M WD ∼ 0.7 M ⊙ . The secondary star is a low-mass main-sequence star, with a mass of M sec ≈ 0.43 M ⊙ . Spectral observations show initial dominance of Balmer emission lines accompanied by prominent P Cygni profiles during the first +339 days. These features disappeared in later epochs, being replaced by high-ionization coronal lines, indicating that the nova had transitioned to the coronal phase by day +371. To investigate the physical conditions of the ejecta and the central source, we conducted photoionization modeling using cloudy . Our model reveals a gradual increase in the temperature and luminosity of the system, and suggests that the ejecta were primarily composed of He, N, Fe, Ne, and Ca, with noticeable temporal variations in their relative abundances. The estimated mean ejected mass is approximately 1.10 × 10 −4 M ⊙ , which is relatively high and suggests a low-mass WD. Our optical spectroscopic and photometric analyses, combined with detailed photoionization modeling, indicate that the WD in Nova V1405 Cas is unlikely to be of the ONeMg type.
Funding Information
  • Agentúra na Podporu Výskumu a Vývoja (APVV-20-0148)

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