Mass-velocity dispersion relation by using the \textit{Gaia} data and its effect on interpreting short-duration and degenerate microlensing events

Abstract

Gravitational microlensing, the lensing of stars in the Milky Way galaxy with other stars, has been used for exploring compact dark matter objects, exoplanets, and black holes. The duration of microlensing events, the so-called Einstein crossing time, is a function of distance, mass, and velocities of lens objects. Lenses with different ages and masses might have various characteristic velocities inside the galaxy and this might lead to our misinterpretation of microlensing events. In this work, we use the \gaia~archived data to find a relation between the velocity dispersion and mass, and the age of stars. This mass-velocity dispersion relation confirms the known age-velocity relation for early-type and massive stars, and additionally reveals a dependence of stellar velocity dispersion on the mass for low-mass and late-type stars at $2$-$3$ sigma level. By considering this correlation, we simulate short-duration microlensing events due to brown dwarfs. From this simulation, we conclude that lens masses are underestimated by $\sim 2.5$-$5.5\%$ while modeling short-duration and degenerate microlensing events with the Bayesian analysis.

arXiv comment9 pages, 4 Figures; accepted by The Astronomical Journal

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• A Statistical Relation between Mass, Age and Velocity Dispersion in the Solar Neighborhood