A class of optical transients known as Luminous Red Novae ( LRNe ) have recently been associated with mass ejections from binary stars undergoing common-envelope evolution .
We use the population synthesis code COMPAS to explore the impact of a range of assumptions about the physics of common-envelope evolution on the properties of LRNe .
In particular , we investigate the influence of various models for the energetics of LRNe on the expected event rate and light curve characteristics , and compare with the existing sample .
We find that the Galactic rate of LRNe is \sim 0.2 yr ^ { -1 } , in agreement with the observed rate .
In our models , the luminosity function of Galactic LRNe covers multiple decades in luminosity and is dominated by signals from stellar mergers , consistent with observational constraints from iPTF and the Galactic sample of LRNe .
We discuss how observations of the brightest LRNe may provide indirect evidence for the existence of massive ( > 40 M _ { \odot } ) red supergiants .
Such LRNe could be markers along the evolutionary pathway leading to the formation of double compact objects .
We make predictions for the population of LRNe observable in future transient surveys with the Large Synoptic Survey Telescope and the Zwicky Transient Facility .
In all plausible circumstances , we predict a selection-limited observable population dominated by bright , long-duration events caused by common envelope ejections .
We show that the Large Synoptic Survey Telescope will observe 20 – 750 LRNe per year , quickly constraining the luminosity function of LRNe and probing the physics of common-envelope events .