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Abstract
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 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+128.31-84.94 days for the best solution and tE=453.74+178.69-105.74 days for the second-best. Assuming Galaxy priors, this translates to the most probable lens mass of ML = 2.65+5.09-1.48 M⊙ and ML = 1.71+3.78-1.06 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.
Original language | English |
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Article number | A59 |
Number of pages | 12 |
Journal | Astronomy & Astrophysics |
Volume | 662 |
Early online date | 14 Jun 2022 |
DOIs | |
Publication status | Published - 30 Jun 2022 |
Keywords
- Gravitational lensing: micro
- Techniques: photometric
- White dwarfs
- Stars: neutron
- Stars: black holes
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