Light Curve Models of Convective Common Envelopes

TL;DR

This paper models the light curves of convective common envelopes to predict their observational signatures, aiding in understanding the physics of common envelope phases in binary star evolution.

Contribution

It introduces the first light curve models for convective common envelopes, linking convection physics to observable signatures for upcoming Rubin Observatory data.

Findings

Convective CEs produce distinct light curve signatures.

Observable out to ~8 Mpc with Rubin, at ~0.3 detections per day.

Light curves are lengthened by convection effects.

Abstract

Common envelopes are thought to be the main method for producing tight binaries in the universe as the orbital period shrinks by several orders of magnitude during this phase. Despite their importance for various evolutionary channels, direct detections are rare, and thus observational constraints on common envelope physics are often inferred from post-CE populations. Population constraints suggest that the CE phase must be highly inefficient at using orbital energy to drive envelope ejection for low-mass systems and highly efficient for high-mass systems. Such a dichotomy has been explained by an interplay between convection, radiation and orbital decay. If convective transport to the surface occurs faster than the orbit decays, the CE self-regulates and radiatively cools. Once the orbit shrinks such that convective transport is slow compared to orbital decay, a burst occurs as the release of orbital energy can be far in excess of that required to unbind the envelope. With the anticipation of first light for the Rubin Observatory, we calculate light curve models for convective common envelopes and provide the time evolution of apparent magnitudes for the Rubin filters. Convection imparts a distinct signature in the light curves and lengthens the timescales during which they are observable. Given Rubin limiting magnitudes, convective CEs should be detectable out to distances of ~8 Mpc at a rate of ~0.3 per day and provide an intriguing observational test of common envelope physics.