HST pre-imaging of a free-floating planet candidate microlensing event
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arXiv
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| Natura: | Preprint |
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2025
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| author | Kapusta, Mateusz Mroz, Przemek Ryu, Yoon-Hyun Udalski, Andrzej Kozlowski, Szymon Terry, Sean Szymanski, Michal K. Soszynski, Igor Pietrukowicz, Pawel Poleski, Radoslaw Skowron, Jan Ulaczyk, Krzysztof Gromadzki, Mariusz Rybicki, Krzysztof Iwanek, Patryk Wrona, Marcin Mróz, Mateusz J. Albrow, Michael D. Chung, Sun-Ju Gould, Andrew Han, Cheongho Hwang, Kyu-Ha Jung, Youn Kil Shin, In-Gu Shvartzvald, Yossi Yee, Jennifer C. Yang, Hongjing Zang, Weicheng Cha, Sang-Mok Kim, Dong-Jin Kim, Seung-Lee Lee, Chung-Uk Lee, Dong-Joo Lee, Yongseok Park, Byeong-Gon Pogge, Richard W. |
| author_facet | Kapusta, Mateusz Mroz, Przemek Ryu, Yoon-Hyun Udalski, Andrzej Kozlowski, Szymon Terry, Sean Szymanski, Michal K. Soszynski, Igor Pietrukowicz, Pawel Poleski, Radoslaw Skowron, Jan Ulaczyk, Krzysztof Gromadzki, Mariusz Rybicki, Krzysztof Iwanek, Patryk Wrona, Marcin Mróz, Mateusz J. Albrow, Michael D. Chung, Sun-Ju Gould, Andrew Han, Cheongho Hwang, Kyu-Ha Jung, Youn Kil Shin, In-Gu Shvartzvald, Yossi Yee, Jennifer C. Yang, Hongjing Zang, Weicheng Cha, Sang-Mok Kim, Dong-Jin Kim, Seung-Lee Lee, Chung-Uk Lee, Dong-Joo Lee, Yongseok Park, Byeong-Gon Pogge, Richard W. |
| contents | High-cadence microlensing observations uncovered a population of very short-timescale microlensing events, which are believed to be caused by the population of free-floating planets (FFP) roaming the Milky Way. Unfortunately, the light curves of such events are indistinguishable from those caused by wide-orbit planets. To properly differentiate both cases, one needs high-resolution observations that would allow resolving a putative luminous companion to the lens long before or after the event. Usually, the baseline between the event and high-resolution observations needs to be quite long ($\sim 10$ yr), hindering potential follow-up efforts. However, there is a chance to use archival data if they exist. Here, we present an analysis of the microlensing event OGLE-2023-BLG-0524, the site of which was captured in 1997 with the Hubble Space Telescope (HST). Hence, we achieve a record-breaking baseline length of 25 years. A very short duration of the event ($t_E = 0.346 \pm 0.008$ d) indicates an FFP as the explanation. We have not detected any potential companion to the lens with the HST data, which is consistent with the FFP origin of the event. Thanks to the available HST data, we are able to reject from 25% to 48% of potential stellar companions depending on the assumed population model. Based on the finite-source effects in the light curve we measure the angular Einstein radius value $θ_E = 4.78 \pm 0.23 μas$, suggesting a super-Earth in the Galactic disk or a sub-Saturn-mass planet in the Galactic bulge. We show that the archival high-resolution images should be available for several microlensing events, providing us with the unprecedented possibility of seeing the lensing system as it was many years before the event. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_01109 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | HST pre-imaging of a free-floating planet candidate microlensing event Kapusta, Mateusz Mroz, Przemek Ryu, Yoon-Hyun Udalski, Andrzej Kozlowski, Szymon Terry, Sean Szymanski, Michal K. Soszynski, Igor Pietrukowicz, Pawel Poleski, Radoslaw Skowron, Jan Ulaczyk, Krzysztof Gromadzki, Mariusz Rybicki, Krzysztof Iwanek, Patryk Wrona, Marcin Mróz, Mateusz J. Albrow, Michael D. Chung, Sun-Ju Gould, Andrew Han, Cheongho Hwang, Kyu-Ha Jung, Youn Kil Shin, In-Gu Shvartzvald, Yossi Yee, Jennifer C. Yang, Hongjing Zang, Weicheng Cha, Sang-Mok Kim, Dong-Jin Kim, Seung-Lee Lee, Chung-Uk Lee, Dong-Joo Lee, Yongseok Park, Byeong-Gon Pogge, Richard W. Earth and Planetary Astrophysics Astrophysics of Galaxies High-cadence microlensing observations uncovered a population of very short-timescale microlensing events, which are believed to be caused by the population of free-floating planets (FFP) roaming the Milky Way. Unfortunately, the light curves of such events are indistinguishable from those caused by wide-orbit planets. To properly differentiate both cases, one needs high-resolution observations that would allow resolving a putative luminous companion to the lens long before or after the event. Usually, the baseline between the event and high-resolution observations needs to be quite long ($\sim 10$ yr), hindering potential follow-up efforts. However, there is a chance to use archival data if they exist. Here, we present an analysis of the microlensing event OGLE-2023-BLG-0524, the site of which was captured in 1997 with the Hubble Space Telescope (HST). Hence, we achieve a record-breaking baseline length of 25 years. A very short duration of the event ($t_E = 0.346 \pm 0.008$ d) indicates an FFP as the explanation. We have not detected any potential companion to the lens with the HST data, which is consistent with the FFP origin of the event. Thanks to the available HST data, we are able to reject from 25% to 48% of potential stellar companions depending on the assumed population model. Based on the finite-source effects in the light curve we measure the angular Einstein radius value $θ_E = 4.78 \pm 0.23 μas$, suggesting a super-Earth in the Galactic disk or a sub-Saturn-mass planet in the Galactic bulge. We show that the archival high-resolution images should be available for several microlensing events, providing us with the unprecedented possibility of seeing the lensing system as it was many years before the event. |
| title | HST pre-imaging of a free-floating planet candidate microlensing event |
| topic | Earth and Planetary Astrophysics Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2507.01109 |