Single lens mass measurement in the high magniﬁcation microlensing event Gaia19bld located in the Galactic Disk
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Context. Microlensing gives 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 θE 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 densely followed-up with a network of ground based observatories and the Spitzer Space Telescope. We collected multiple high resolution spectra with VLT/X-Shooter to characterise the source star. The event was also observed with 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 derive 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 the 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.
Rybicki , K A , Wyrzykowski , Ł , Bachelet , E , Cassan , A , Zieliński , P , Gould , A , Calchi Novati , S , Yee , J C , Ryu , Y-H , Gromadzki , M , Mikołayczyk , P , Ihanec , N , Kruszyńska , K , Hambsch , F-J , Zola , 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 , Pietrokowicz , 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 , Shvartzwald , 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 , Lam , M C , Maskoliunas , M , Pakstiene , E , Stankeviciute , A , Zdanavicius , J & Ziółkowska , O 2021 , ' Single lens mass measurement in the high magniﬁcation microlensing event Gaia19bld located in the Galactic Disk ' , Astronomy & Astrophysics .
Astronomy & Astrophysics
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DescriptionFunding: This work was supported from the Polish NCN grants: Preludium No. 2017/25/N/ST9/01253, Harmonia No. 2018/30/M/ST9/00311, MNiSW grant DIR/WK/2018/12, Daina No. 2017/27/L/ST9/03221, and by the Research Council of Lithuania, grant No. S-LL-19-2. . The OGLE project has received funding from the NCN grant MAESTRO 2014/14/A/ST9/00121 to AU. We acknowledge the European Commission’s H2020 OPTICON grant No. 730890. YT acknowledges the support of DFG priority program SPP 1992 "Exploring the Diversity of Extrasolar Planets" (WA 1047/11-1). EB and RS gratefully acknowledge support from NASA grant 80NSSC19K0291. Work by AG was supported by JPL grant 1500811. Work by JCY was supported by JPL grant 1571564. SJF thanks Telescope Live for access to their telescope network. NN acknowledges the support of Data Science Research Center, Chiang Mai University. F.O.E. acknowledges support from the FONDECYT grant nr. 1201223.
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