A terrestrial-mass rogue planet candidate detected in the shortest-timescale microlensing event

Autor: Mroz, P., Poleski, R., Gould, A., Udalski, A., Sumi, T., Szymanski, M. K., Soszynski, I., Pietrukowicz, P., Kozlowski, S., Skowron, J., Ulaczyk, K., Albrow, M. D., Chung, S. -J., Han, C., Hwang, K. -H., Jung, Y. K., Kim, H. -W., Ryu, Y. -H., Shin, I. -G., Shvartzvald, Y., Yee, J. C., Zang, W., Cha, S. -M., Kim, D. -J., Kim, S. -L., Lee, C. -U., Lee, D. -J., Lee, Y., Park, B. -G., Pogge, R. W.
Rok vydání: 2020
Předmět:
Druh dokumentu: Working Paper
DOI: 10.3847/2041-8213/abbfad
Popis: Some low-mass planets are expected to be ejected from their parent planetary systems during early stages of planetary system formation. According to planet-formation theories, such as the core accretion theory, typical masses of ejected planets should be between 0.3 and 1.0 $M_{\oplus}$. Although in practice such objects do not emit any light, they may be detected using gravitational microlensing via their light-bending gravity. Microlensing events due to terrestrial-mass rogue planets are expected to have extremely small angular Einstein radii (< 1 uas) and extremely short timescales (< 0.1 day). Here, we present the discovery of the shortest-timescale microlensing event, OGLE-2016-BLG-1928, identified to date ($t_{\rm E} \approx 0.0288\ \mathrm{day} = 41.5 \mathrm{min}$). Thanks to the detection of finite-source effects in the light curve of the event, we were able to measure the angular Einstein radius of the lens $\theta_{\rm E} = 0.842 \pm 0.064$ uas, making the event the most extreme short-timescale microlens discovered to date. Depending on its unknown distance, the lens may be a Mars- to Earth-mass object, with the former possibility favored by the Gaia proper motion measurement of the source. The planet may be orbiting a star but we rule out the presence of stellar companions up to the projected distance of 8.0 au from the planet. Our discovery demonstrates that terrestrial-mass free-floating planets can be detected and characterized using microlensing.
Comment: accepted for publication in ApJ Letters, minor changes
Databáze: arXiv
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