Mass- and Metallicity-dependent Changes in Stellar Hydrogen Luminosity after Low-mass Brown Dwarf Engulfment

Abstract Brown dwarf engulfment is a common occurrence in stellar systems. However, its dynamics have not been fully studied. By using Modules for Experiments in Stellar Astrophysics to simulate the engulfment of low-mass brown dwarfs of Jupiter-composition and 1 R J by 100 R ⊙ red giant branch (RGB) stars, we aim to shed some light on the immediate effects of brown dwarf engulfment on RGB stars. We varied engulfed brown dwarf mass (13, 16.5, and 20 M J ) and initial stellar metallicity ( z = 0.001, 0.01, and 0.04) to study their impacts on the hydrogen luminosity of the engulfing RGB star. We found prominent dips of up to ≈17.8%, and post-dip spikes of up to ≈2.6%, in the hydrogen luminosity of the star immediately after engulfment in all cases, with more pronounced dips and post-dip spikes for higher-mass brown dwarfs and lower-metallicity stars.