Two-Dimensional Radiation-Hydrodynamic Simulations of Luminous Red Novae

Abstract

Luminous Red Novae (LRNe) are transients associated with mass ejection during stellar mergers and common envelope evolution (CEE). LRNe have the potential to illuminate the poorly understood phases of binary evolution leading up to the CEE, during the mass ejection phase, and in the immediate aftermath. However, the mechanism responsible for powering LRN light curves and the origin of their observed diversity remain open questions. Here, we perform two-dimensional moving-mesh radiation-hydrodynamic simulations of LRNe that take into account hydrogen and helium recombination and relevant opacities. We study a typical high-mass stellar merger, which dynamically ejects 2 $M_{\odot }$ with a characteristic velocity of 410 km/s. This ejecta collides with 2.7 $M_{\odot }$ of equatorially concentrated circumbinary material (CBM) left behind from a prior phase of non-conservative runaway mass transfer. We find that the resulting light curve is composed of a short, blue peak followed by a redder, predominantly shock-powered plateau with luminosities reaching up to $10^{41}$ erg/s and durations up to 200 days. These luminosities are significantly higher, and the durations much longer, than those produced by a simple spherical ejection of the same mass. They also depend in a complex way on the radial distribution of the CBM and the viewing angle. The shock is embedded in the ejecta and its observational signatures during the optically-thick phase are largely hidden. Our results are broadly compatible with observations of the brightest extragalactic LRNe and pave the way for the transformation of LRNe into powerful probes of binary evolution.

Accepted to ApJL. 6 figures and 1 table in the main text, 28 pages. Added tabulated EOS and opacities, viewing-angle dependent light curves from raytracing, illumination by central merger remnant, and comparison to observed events. Movies will become available in the journal once published

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Cited by in corpus (2)

• From Common Envelope Evolution to Luminous Red Novae I: A One-dimensional Radiation Hydrodynamic Model
• The fate of the progenitors of luminous red novae: Infrared detection of LRNe years after the outburst