The supersoft X-ray transient ASASSN-16oh as a thermonuclear runaway without mass ejection

Abstract

The supersoft X-ray and optical transient ASASSN-16oh has been interpreted by Maccarone et al. (2019) as having being induced by an accretion event on a massive white dwarf, resembling a dwarf nova super-outburst. These authors argued that the supersoft X-ray spectrum had a different origin than in an atmosphere heated by shell nuclear burning, because no mass was ejected. We find instead that the event's timescale and other characteristics are typical of non-mass ejecting thermonuclear runaways, as already predicted by Shara et al. (1977) and the extensive grid of nova models by Yaron et al. (2005). We suggest that the low X-ray and bolometric luminosity in comparison to the predictions of the models of nuclear burning are due to an optically thick accretion disk, hiding most of the white dwarf surface. If this is the case, we calculated that the optical transient can be explained as a non-ejective thermonuclear event on a WD of $\simeq$1.1M${}_{\odot }$ accreting at the rate of $\simeq 3.5-5\times 10^{-7}$M${}_{\odot }$yr${}^{-1}$. We make predictions that should prove whether the nature of the transient event was due to thermonuclear burning or to accretion; observational proof should be obtained in the next few years, because a new outburst should occur within $\simeq$10-15 years of the event.

7 pages, 2 figures

References in corpus (7)

• NLTE model atmospheres for the hottest white dwarfs: Spectral analysis of the compact component in nova V4743 Sgr
• A Thousand and One Nova Outbursts
• Observational Signatures of SNIa Progenitors, as Predicted by Models
• Short-period X-ray oscillations in super-soft novae and persistent SSS
• Variability and multi-periodic oscillations in the X-ray light curve of the classical nova V4743 Sgr
• Chemical and physical parameters from X-ray high resolution spectra of the Galactic nova V959 Mon
• CXO J004318.8+412016, a steady supersoft X-ray source in M 31

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• Investigation of a likely orbital periodicity of Nova Hercules 2021 in X-rays and gamma-rays
• Millinovae: A New Class of Transient Supersoft X-ray Sources without a Classical Nova Eruption
• Revisiting multiwavelength data on the supersoft X-ray source CAL 83
• X-ray emission mechanisms in accreting white dwarfs
• Helium Accumulation and Thermonuclear Instabilities on Accreting White Dwarfs: From Recurring Helium Novae to Type Ia Supernovae