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Correcting Gaia distances for microlensing events with spectroscopy

March 13, 2024

When: March 13, 2024 3:30PM
Where: LCO Downstairs Conference Room

Paweł Zieliński

Institute of Astronomy Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Toruń, Poland

The Gaia mission delivers an enormous amount of astrometric and photometric data. Based on Gaia light curves we can select a growing number of microlensing event candidates located mostly in the Galactic Plane. The majority of them must still be classified spectroscopically to distinguish genuine microlensing events from other types of outbursts and variables. Therefore, we use a wide range of world-class telescopes equipped with low- and high-resolution spectrographs to detect distinctive absorption and/or emission features and determine physical parameters as well as line-of-sight extinction for the sources in the microlensing events. Moreover, the spectroscopic analysis is important not only in constraining the microlensing model and the lens parameters but also in distance estimation. From the comparison of spectroscopic distances with Gaia parallax/distance measurements, we found that at least in some cases Gaia distances can not be trusted (probably due to blending or astrometric microlensing) and have to be used with caution. In addition, this seems to be reflected in the quality flags and parameters of astrometric signals given in the GaiaDR3 catalogue. I will present the status of the spectroscopic study of candidates for microlensing events alerted by Gaia with recent examples of interesting results.

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Paweł Zieliński

Paweł Zieliński is a postdoc at the Institute of Astronomy, Nicolaus Copernicus University in Torun (Poland) since 2022. He participates in the search for compact stellar remnants in gravitational microlensing events based on the data from the Gaia space mission and ground-based telescope network coordinated within the OPTICON-RadioNet Pilot program. He obtained his PhD degree in 2015 at the Nicolaus Copernicus University in Toruń, taking part in the Pennsylvania-Toruń Planet Search project. Then, he spent several years as a postdoctoral researcher at Masaryk University in Brno (Czech Republic) and Warsaw University Astronomical Observatory (Poland). He was involved in searching for young exoplanets in open clusters as well as photometric and spectroscopic follow-up observations of microlensing events candidates. Currently, he continues the photometric and spectroscopic study of Gaia-alerted microlensing events and the development of an automatic tool for time-domain data processing - Black Hole TOM. He also worked in the science centre - Innovation Center Mill of Knowledge in Toruń - as a co-author and animator of interactive workshops, lectures and exhibitions. Since 2021, he is a treasurer of the Polish Astronomical Society.

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