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

January 2022 • 2022A&A...657A..18R

Authors • Rybicki, K. A. • Wyrzykowski, Ł. • Bachelet, E. • Cassan, A. • Zieliński, P. • Gould, A. • Calchi Novati, S. • Yee, J. C. • Ryu, Y. -H. • Gromadzki, M. • Mikołajczyk, P. • Ihanec, N. • Kruszyńska, K. • Hambsch, F. -J. • Zoła, S. • Fossey, S. J. • Awiphan, S. • Nakharutai, N. • Lewis, F. • Olivares E., F. • Hodgkin, S. • Delgado, A. • Breedt, E. • Harrison, D. L. • van Leeuwen, M. • Rixon, G. • Wevers, T. • Yoldas, A. • Udalski, A. • Szymański, M. K. • Soszyński, I. • Pietrukowicz, P. • Kozłowski, S. • Skowron, J. • Poleski, R. • Ulaczyk, K. • Mróz, P. • Iwanek, P. • Wrona, M. • Street, R. A. • Tsapras, Y. • Hundertmark, M. • Dominik, M. • Beichman, C. • Bryden, G. • Carey, S. • Gaudi, B. S. • Henderson, C. • Shvartzvald, Y. • Zang, W. • Zhu, W. • Christie, G. W. • Green, J. • Hennerley, S. • McCormick, J. • Monard, L. A. G. • Natusch, T. • Pogge, R. W. • Gezer, I. • Gurgul, A. • Kaczmarek, Z. • Konacki, M. • Lam, M. C. • Maskoliunas, M. • Pakstiene, E. • Ratajczak, M. • Stankeviciute, A. • Zdanavicius, J. • Ziółkowska, O.

Abstract • Context. Microlensing provides a unique opportunity to detect non-luminous objects. In the rare cases that the Einstein radius θ_E and microlensing parallax π_E can be measured, it is possible to determine the mass of the lens. With technological advances in both ground- and space-based observatories, astrometric and interferometric measurements are becoming viable, which can lead to the more routine determination of θ_E and, if the microlensing parallax is also measured, the mass of the lens.
Aims: We present the photometric analysis of Gaia19bld, a high-magnification (A ≈ 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.
Methods: 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.
Results: We compute the mass of the lens to be 1.13 ± 0.03 M_⊙ and derive its distance to be 5.52_−0.64^+0.35 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.

Links

• PREPRINT http://arxiv.org/abs/2112.01613
• POSTSCRIPT https://www.aanda.org/10.1051/0004-6361/202039542/postscript
• ELECTR https://doi.org/10.1051%2F0004-6361%2F202039542
• SIMBAD http://simbad.u-strasbg.fr/simbo.pl?bibcode=2022A%26A...657A..18R
• PDF https://www.aanda.org/10.1051/0004-6361/202039542/pdf
• DATA http://archive.eso.org/bin/ads2eso?2022A%26A...657A..18R
• DATA https://irsa.ipac.caltech.edu/bibdata/2022/R/2022A&A...657A..18R.html