Persistent nuclear burning in Nova Sgr 2016 N.4 (=V5856 Sgr = ASASSN-16ma) six years past its outburst

We report on the fast Nova Sgr 2016 N.4 being surprisingly trapped in a long-lasting and bright plateau (ΔI≥10 mag above quiescence) six years past the nova eruption. Very few other novae experience a similar occurrence. We carried out an intensive observing campaign collecting daily BVRI photometry and monthly high-resolution optical spectroscopy, and observed the nova in ultraviolet and X-rays with Swift at five distinct epochs. The bolometric luminosity radiated during the plateau is ∼4200 L⊗ (scaled to the distance of the Galactic Bulge), corresponding to stable nuclear burning on a 0.6 M⊗ white dwarf. A stable wind is blown off at full width at zero intensity (FWZI) ∼ 1600 km s-1, with episodic reinforcement of a faster FWZI ∼ 3400 km s-1 mass loss, probably oriented along the polar directions. The collision of these winds could power the emission detected in X-rays. The burning shell has an outer radius of ∼25 R⊗ at which the effective temperature is ∼7600 K, values similar to those of a F0 II/Ib bright giant. The Δm < 1 mag variability displayed during the plateau is best described as chaotic, with the irregular appearance of quasi-periodic oscillations with a periodicity of 15-17 days. A limited amount of dust (≈3 × 10-11 M⊗) continuously condenses at Tdust ∼ 1200 K in the outflowing wind, radiating Ldust ∼ 52 L⊗. © U. Munari et al. 2022.

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Keywords

Cataclysmic variables, Novae, Outflows, Stars: winds, Bolometric luminosities, Galactic bulge, High resolution, Long lasting, Nova, Nuclear burning, Optical spectroscopy, Stars: winds, White dwarfs

Citation

Astronomy and Astrophysics, Volume 667, 1 November 2022, Article number A7

DOI

10.1051/0004-6361/202244498

URI

https://repositorio.unab.cl/handle/ria/55779

Collections

FCE - Artículos de Revista

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