1. Lens mass estimate in the galactic disk extreme parallax microlensing event Gaia19dkeM. Maskoliunas, Łukasz Wyrzykowski, K. Howil, P. J. Mikołajczyk, P. Zieliński, Z. Kaczmarek, K. Kruszyńska, M. Jabłońska, J. Zdanavičius, Mateusz Bronikowski, 2024, izvirni znanstveni članek Opis: We present the results of our analysis of Gaia19dke, an extraordinary microlensing event in the Cygnus constellation that the Gaia satellite discovered. This event featured a strong microlensing parallax effect, resulting in multiple light curve peaks. We conducted extensive photometric, spectroscopic, and high-resolution imaging follow-up observations to determine the mass and nature of the invisible lensing object. Using the Milky Way priors on the density and proper motion of lenses, we found that the lens is likely to be located at a distance of DL=3.3(+2.1, -1.7) kpc, and has a mass of ML=0.50(+0.82, -0.27) M☉. Based on its low luminosity and mass, we propose that the lens in the Gaia19dke event is either a main sequence star or an isolated white dwarf. Due to its brightness, longevity, and lack of blending, Gaia19dke is a target for which the forthcoming Gaia Data Release 4 data will help to constrain the parameters of the lens.
Ključne besede: gravitational lensing, micro stars, fundamental parameters, white dwarfs, astrophysics, solar astrophysics, stellar astrophysics, astrophysics of galaxies, instrumentation for astrophysics, methods for astrophysics
Objavljeno v RUNG: 13.01.2025; Ogledov: 130; Prenosov: 0
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2. Lens parameters for Gaia18cbf – a long gravitational microlensing event in the Galactic planeK. Kruszyńska, Ł. Wyrzykowski, K. A. Rybicki, M. Maskoliūnas, E. Bachelet, N. Rattenbury, P. Mróz, P. Zieliński, K. Howil, Z. Kaczmarek, S. T. Hodgkin, N. Ihanec, I. Gezer, M. Gromadzki, P. Mikołajczyk, A. Stankevičiūtė, V. Čepas, E. Pakštienė, K. Šiškauskaitė, J. Zdanavičius, V. Bozza, M. Dominik, R. Figuera Jaimes, A. Fukui, M. Hundertmark, N. Narita, R. Street, Y. Tsapras, Mateusz Bronikowski, M. Jabłońska, A. Jabłonowska, O. Ziółkowska, 2022, izvirni znanstveni članek Opis: Context. The timescale of a microlensing event scales as a square root of a lens mass. Therefore, long-lasting events are important candidates for massive lenses, including black holes.
Aims. Here, we present the analysis of the Gaia18cbf microlensing event reported by the Gaia Science Alerts system. It exhibited a long timescale and features that are common for the annual microlensing parallax effect. We deduce the parameters of the lens based on the derived best fitting model.
Methods. We used photometric data collected by the Gaia satellite as well as the follow-up data gathered by the ground-based observatories. We investigated the range of microlensing models and used them to derive the most probable mass and distance to the lens using a Galactic model as a prior. Using a known mass-brightness relation, we determined how likely it is that the lens is a main-sequence (MS) star.
Results. This event is one of the longest ever detected, with the Einstein timescale of tE = 491.41−84.94+128.31 days for the best solution and tE = 453.74−105.74+178.69 days for the second best. Assuming Galaxy priors, this translates to the most probable lens masses of ML = 2.65−1.48+5.09 M⊙ and ML = 1.71−1.06+3.78 M⊙, respectively. The limits on the blended light suggest that this event was most likely not caused by a MS star, but rather by a dark remnant of stellar evolution.
Ključne besede: gravitational lensing: micro, Galaxy: stellar content, stars: black holes, stars: neutron, Astrophysics - Solar and Stellar Astrophysics
Objavljeno v RUNG: 13.11.2023; Ogledov: 1801; Prenosov: 7
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