Is there a nearby microlensing stellar remnant hiding in Gaia DR3 astrometry?

Abstract

Massive galactic lenses with large Einstein Radii should cause a measurable astrometric microlensing effect, i.e. the light centroid shift due to the motion of the two images. Such a shift in the position of a background star due to microlensing was not included in the $Gaia$ astrometric model, therefore significant deviation should cause $Gaia$'s astrometric parameters to be determined incorrectly. Here we studied one of the photometric microlensing events reported in the $Gaia$ DR3, GaiaDR3-ULENS-001, for which poor goodness of $Gaia$ fit and erroneous parallax could indicate the presence of the astrometric microlensing signal. Based on the photometric microlensing model, we simulated $Gaia$ astrometric time-series with the astrometric microlensing effect added. We found that including microlensing with the angular Einstein Radius of ${\theta }_{\mathrm{E}}$ = $2.60_{-0.24}^{+0.21}$ mas ($2.47_{-0.24}^{+0.28}$ mas) assuming positive (negative) impact parameter $u_0$ reproduces well the astrometric quantitie reported by $Gaia$. We estimate the mass of the lens to $1.00_{-0.18}^{+0.23}$ $M_{\odot }$ ($0.70_{-0.13}^{+0.17}$ $M_{\odot }$) and its distance to $0.90_{-0.11}^{+0.14}$ kpc ($0.69_{-0.09}^{+0.13}$ kpc), proposing the lens could be a nearby isolated white dwarf.

References in corpus (4)

• A catalogue of white dwarfs in Gaia EDR3
• Three-dimensional mapping of the local interstellar medium with composite data
• Astrometric excess noise in Gaia EDR3 and the search for X-ray binaries
• Completeness of the Gaia-verse III: using hidden states to infer gaps, detection efficiencies and the scanning law from the DR2 light curves

Cited by in corpus (1)

• Predicting Astrometric Microlensing Events from Gaia DR3