Single-lens mass measurement in the high-magnification microlensing event Gaia19bld located in the Galactic disc

Abstract

We present the photometric analysis of Gaia19bld, a high-magnification ($A\approx 60$) microlensing event located in the southern Galactic plane, which exhibited finite source and microlensing parallax effects. Due to a prompt detection by the Gaia satellite and the very high brightness of $I=9.05$mag at the peak, it was possible to collect a complete and unique set of multi-channel follow-up observations, which allowed us to determine all parameters vital for the characterisation of the lens and the source in the microlensing event. Gaia19bld was discovered by the Gaia satellite and was subsequently intensively followed up with a network of ground-based observatories and the Spitzer Space Telescope. We collected multiple high-resolution spectra with Very Large Telescope (VLT)/X-Shooter to characterise the source star. The event was also observed with VLT Interferometer (VLTI)/PIONIER during the peak. Here we focus on the photometric observations and model the light curve composed of data from Gaia, Spitzer, and multiple optical, ground-based observatories. We find the best-fitting solution with parallax and finite source effects. We derived the limit on the luminosity of the lens based on the blended light model and spectroscopic distance. We compute the mass of the lens to be $1.13\pm 0.03M_{\odot }$ and derive its distance to be $5.52_{-0.64}^{+0.35}\mathrm{kpc}$. The lens is likely a main sequence star, however its true nature has yet to be verified by future high-resolution observations. Our results are consistent with interferometric measurements of the angular Einstein radius, emphasising that interferometry can be a new channel for determining the masses of objects that would otherwise remain undetectable, including stellar-mass black holes.

accepted to Astronomy&Astrophysics

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Cited by in corpus (10)

• Gaia Data Release 3: Microlensing Events from All Over the Sky
• The Large Array Survey Telescope -- Science Goals
• A spectroscopic follow-up for Gaia19bld
• Relative astrometry in an annular field
• First Resolution of Microlensed Images of a Binary-Lens Event
• Observations of Microlensed Images with Dual-field Interferometry: On-sky Demonstration and Prospects
• Gaia21blx: Complete resolution of a binary microlensing event in the Galactic disk
• Gaia20fnr: A binary-lens microlensing event with full orbital motion revealed by four space telescopes
• Constraining Lens Masses in Moderately to Highly Magnified Microlensing Events from Gaia
• LensNet: Enhancing Real-time Microlensing Event Discovery with Recurrent Neural Networks in the Korea Microlensing Telescope Network