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arXiv · 2108.02499

Using Source Proper Motion to Validate Terrestrial Parallax: OGLE-2019-BLG-1058

In-Gu Shin·Jennifer C. Yee·Kyu-Ha Hwang·Andrzej Udalski·Andrew Gould·Michael D. Albrow·Sun-Ju Chung·Cheongho Han·Youn Kil Jung·Hyoun-Woo Kim·Yoon-Hyun Ryu·Yossi Shvartzvald·Weicheng Zang·Sang-Mok Cha·Dong-Jin Kim·Seung-Lee Kim·Chung-Uk Lee·Dong-Joo Lee·Yongseok Lee·Byeong-Gon Park·Richard W. Pogge·Przemek Mróz·Michał K. Szymański·Jan Skowron·Radek Poleski·Igor Soszyński·Paweł Pietrukowicz·Szymon Kozłowski·Krzysztof Ulaczyk·Krzysztof A. Rybicki·Patryk Iwanek·Marcin Wrona·Mariusz Gromadzki
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Abstract

We show that because the conditions for producing terrestrial microlens parallax (TPRX; i.e., a nearby disk lens) will also tend to produce a large lens-source relative proper motion ($\mu_{\rm rel}$), source proper motion (${\boldsymbol\mu}_{\rm S}$) measurements in general provide a strong test of TPRX signals, which \citet{gould13} showed were an important probe of free-floating planet (FFP) candidates. As a case study, we report a single-lens/single-source microlensing event designated as OGLE-2019-BLG-1058. For this event, the short timescale ($\sim 2.5$ days) and very fast $\mu_{\rm rel}$ ($\sim 17.6\, {\rm mas\, yr^{-1}}$) suggest that this isolated lens is an FFP candidate located in the disk of our Galaxy. For this event, we find a TPRX signal consistent with a disk FFP, but at low significance. A direct measurement of the ${\boldsymbol\mu}_{\rm S}$ shows that the large $\mu_{\rm rel}$ is due to an extreme ${\boldsymbol\mu}_{\rm S}$, and thus, the lens is consistent with being a very low-mass star in the bulge and the TPRX measurement is likely spurious. By contrast, we show how a precise measurement of ${\boldsymbol\mu}_{\rm S}$ with the mean properties of the bulge proper motion distribution would have given the opposite result; i.e., provided supporting evidence for an FFP in the disk and the TPRX measurement.

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In-Gu Shin, Jennifer C. Yee, Kyu-Ha Hwang, Andrzej Udalski, Andrew Gould, Michael D. Albrow, Sun-Ju Chung, Cheongho Han, Youn Kil Jung, Hyoun-Woo Kim, Yoon-Hyun Ryu, Yossi Shvartzvald, Weicheng Zang, Sang-Mok Cha, Dong-Jin Kim, Seung-Lee Kim, Chung-Uk Lee, Dong-Joo Lee, Yongseok Lee, Byeong-Gon Park, Richard W. Pogge, Przemek Mróz, Michał K. Szymański, Jan Skowron, Radek Poleski, Igor Soszyński, Paweł Pietrukowicz, Szymon Kozłowski, Krzysztof Ulaczyk, Krzysztof A. Rybicki, Patryk Iwanek, Marcin Wrona, Mariusz Gromadzki. 2021-08-05. Using Source Proper Motion to Validate Terrestrial Parallax: OGLE-2019-BLG-1058. https://doi.org/10.3847/1538-3881%2Fac2ba5

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