Lens mass estimate in the Galactic disk extreme parallax microlensing event Gaia19dke

TL;DR

This paper analyzes a microlensing event Gaia19dke with strong parallax effects, estimating the lens as likely an isolated white dwarf at a few kiloparsecs from Earth, using extensive follow-up observations.

Contribution

It provides a detailed mass and distance estimate of an invisible lens in a microlensing event, demonstrating the use of Gaia data and follow-up observations to identify a white dwarf.

Findings

Lens likely at 3.05 kpc distance

Lens mass estimated at 0.51 solar masses

Lens identified as an isolated white dwarf

Abstract

We present the results of our analysis of Gaia19dke, an extraordinary microlensing event in the Cygnus constellation that was first spotted by the {\gaia} satellite. This event featured a strong microlensing parallax effect, which resulted in multiple peaks in the light curve. We conducted extensive photometric, spectroscopic, and high-resolution imaging follow-up observations to determine the mass and the nature of the invisible lensing object. Using the Milky Way priors on density and velocity of lenses, we found that the dark lens is likely to be located at a distance of $D_L =(3.05^{+4.10}_{-2.42})$kpc, and has a mass of $M_L =(0.51^{+3.07}_{-0.40}) M_\odot$. Based on its low luminosity and mass, we propose that the lens in Gaia19dke event is an isolated white dwarf.