Using OSARG variables stars to trace the chemo-dynamical history of the Milky Way

OSARGs are a ubiquitous and unique type of long-period variables that has small-amplitude, multi-periodic signatures, and exhibit a period-luminosity relation. Just like RR-lyra and Cepheid variables, observing the photometric magnitude variation of OSARGs, we can derive the heliocentric distance of these objects, making them excellent tracer to different structures in the Milky Way. Better than RR-lyra and Cepheid variables, OSARGs has mass similar to the Sun, and sitting in the red-giant branch or asymptotic giant branch in the stellar evolution, so it does not bias towards the old or young star population.

We aim to construct an unbiased tracer sample to investigate different structures in the Milky Way using OSARGs. We use the OGLE survey which provide long-term photometric observations for LMC, SMC, the Galactic bulge to study the properties of the existent OSARGs and calibrate the period-luminosity relation. Then, establishing on the relation, we identify new OSARGs and calculate their heliocentric distances in the whole northern hemisphere using ZTF survey.

This sample will be capable to shed new light on the substructures and chemo-dynamical evolution of the Milky Way, especially on the more distant part of the Milky Way. For example, we plan to study the dynamics of the Galactic bulge/bar in full 6D phase space using Gaia astrometry + OSARGs luminosity distances + Gaia radial velocities.