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arXiv · 2506.04615

A comprehensive light curve model of the very fast nova V1674 Herculis

Mariko Kato·Izumi Hachisu·Hideyuki Saio
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Abstract

V1674 Her is one of the fastest novae, of which the very early phase is well observed including optical rise to the peak over 10 magnitudes. We present a full theoretical light curve model of V1674 Her. Our $1.35~M_\odot$ white dwarf (WD) model with the mass accretion rate of $1\times 10^{-11}~M_\odot$ yr$^{-1}$ explains overall properties including a very fast rise and decay of the optical $V$ light curve. The WD photosphere expands up to $21 ~R_\odot$, thus, a $0.26 ~M_\odot$ companion star orbiting the WD every 3.67 hours, is engulfed 2.7 hours after the onset of thermonuclear runaway, and appears 5.3 days after that. The duration of X-ray flash is only 0.96 hours. The evolution of the expanding envelope and temporal change of the photospheric radius are very consistent with observed optical and X-ray modulations with the orbital and spin (501 s) periods. We confirmed that the decay phase of nova light curve is well approximated by a sequence of steady-state envelope solutions. Using time-stretching method of nova light curves, we obtain the $V$ band distance modulus of $(m-M)_V= 16.3\pm 0.2$, and determine the distance to be $d=8.9\pm 1$ kpc for the interstellar extinction of $E(B-V)= 0.5 \pm 0.05$.

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Mariko Kato, Izumi Hachisu, Hideyuki Saio. 2025-06-05. A comprehensive light curve model of the very fast nova V1674 Herculis. https://arxiv.org/abs/2506.04615

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