Updated High-temperature Opacities for the Dartmouth Stellar Evolution Program and Their Effect on the Jao Gap Location

Abstract

The Jao Gap, a 17% decrease in stellar density at M _G ~ 10 identified in both Gaia Data Release 2 and Early Data Release 3, presents a new method to probe the interior structure of stars near the fully convective transition mass. The Gap is believed to originate from convective-kissing instability wherein asymmetric production of ³He causes the core convective zone of a star to periodically expand and contract and consequently causes the star luminosities to vary. Modeling of the Gap has revealed a sensitivity in its magnitude to a population metallicity primarily through opacity. Thus far, models of the Jao Gap have relied on OPAL high-temperature radiative opacities. Here we present updated synthetic population models tracing the Gap location modeled with the Dartmouth stellar evolution code using the OPLIB high-temperature radiative opacities. Use of these updated opacities changes the predicted location of the Jao Gap by ~0.05 mag as compared to models that use the OPAL opacities. This difference is likely too small to be detectable in empirical data.