# Dynamical Orbital classification of selected N-rich stars with \textit{Gaia} DR2 astrometry

## TL;DR

This study uses Gaia DR2 data and galaxy modeling to classify the orbits of N-rich stars in the Milky Way, revealing their distribution among bulge, disk, and halo components and highlighting potential halo contamination.

## Contribution

It provides a dynamical orbital classification of N-rich stars using Gaia data and galaxy simulations, identifying their likely Galactic components and orbital characteristics.

## Key findings

- Majority of N-rich stars have eccentric orbits with height below 3 kpc.
- Approximately 66% of N-rich stars are in the inner Galaxy inside the corotation radius.
- Some N-rich stars are likely halo interlopers, indicating halo contamination in the bulge area.

## Abstract

We have used the galaxy modeling algorithm \texttt{GravPot16}, to explore the more probable orbital elements of a sample of 64 selected N-rich stars across the Milky Way. Using the newly measured proper motions from \texttt{Gaia} DR2 with existing line-of-sight velocities from APOGEE-2 survey and spectrophotometric distance estimations from the \texttt{StarHorse}. We adopted a set of high-resolution particle simulations evolved in the same steady-state Galactic potential model with a bar, in order to identify the groups of N-rich stars that have a high probability of belonging to the bulge/bar, disk, and stellar halo component. We find that the vast majority of the N-rich stars show typically maximum height from the Galactic plane below 3 kpc, and develop rather eccentric orbits (\textit{e}$>$0.5), which means these stars appear to have bulge/bar-like and/or halo-like orbits. We also show that $\sim66$\% of the selected N-rich stars currently lives in the inner Galaxy inside the corotation radius (C.R.), whilst $\sim14$\% of the N-rich star resides in halo-like orbits. Among the N-rich in the inner Galaxy, $\sim27\%$ of them share orbital properties in the boundary between bulge/bar and disk, depending on the bar pattern speeds. Our dynamical analysis also indicates that some of the N-rich are likely halo interlopers and therefore suggest that halo contamination is not insignificant within the bulge area.