Correlations between Ca II H and K Emission and the Gaia M Dwarf Gap
Abstract
The Gaia M dwarf gap, also known as the Jao Gap, is a novel feature discovered in the Gaia Data Release 2 G versus BP-RP color–magnitude diagram. This gap represents a 17% decrease in stellar density in a thin magnitude band around the convective transition mass (∼0.35 M ⊙) on the main sequence. Previous work has demonstrated a paucity of Hα emission coincident with the G magnitude of the Jao Gap in the solar neighborhood. The exact mechanism that results in this paucity is as of yet unknown; however, the authors of the originating paper suggest that it may be the result of complex variations to a star's magnetic topology driven by the Jao Gap's characteristic formation and breakdown of stars' radiative transition zones. We present a follow-up investigating another widely used magnetic activity metric, Calcium II H and K emission. Ca II H and K activity appears to share a similar anomalous behavior as Hα does near the Jao Gap magnitude. We observe an increase in star-to-star variation of magnetic activity near the Jao Gap. We present a toy model of a star's magnetic field evolution, which demonstrates that this increase may be due to stochastic disruptions to the magnetic field originating from the periodic-mixing events characteristic of the convective kissing instabilities that drive the formation of the Jao Gap.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 2024
- DOI:
- 10.3847/1538-4357/ad2e8c
- arXiv:
- arXiv:2402.14984
- Bibcode:
- 2024ApJ...965...56B
- Keywords:
-
- Stellar evolution;
- Stellar evolutionary models;
- 1599;
- 2046;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 11 pages, 9 Figures, 1 Table, Accepted to ApJ for Publication on Feb 22, 2024