Paper

Free-Floating planet Mass Function from MOA-II 9-year survey towards the Galactic Bulge

Miyazaki, Shota, Hibiki Yama, Fujii, Hirosane, Satoh, Yuki, Tristram, Paul J, koshimoto, Naoki, Suzuki, Daisuke, Sumi, Takahiro, Mio Tomoyoshi, Stela Ishitani Silva, Rattenbury, Nicholas J, Matsubara, Yutaka, Barry, Richard, Yamashita, Kansuke, Abe, Fumio, Olmschenk, Greg, Vandorou, Aikaterini, Bennett, David P, Kondo, Iona, Bond, Ian A, Kirikawa, Rintaro, collaboration, MOA, Fukui, Akihiko, Itow, Yoshitaka, Clement Ranc, Bhattacharya, Aparna, Hirao, Yuki, Muraki, Yasushi, Hamada, Ryusei

2023

Overview

We present the first measurement of the mass function of free-floating planets (FFP) or very wide orbit planets down to an Earth mass, from the MOA-II microlensing survey in 2006-2014. Six events are likely to be due to planets with Einstein radius crossing times, \\(t_{\\rm E}<0.5\\)days, and the shortest has \\(t_{\\rm E} = 0.057\\pm 0.016\\)days and an angular Einstein radius of \\(\\theta_{\\rm E} = 0.90\\pm 0.14\\mu\\)as. We measure the detection efficiency depending on both \\(t_{\\rm E}\\) and \\(\\theta_{\\rm E}\\) with image level simulations for the first time. These short events are well modeled by a power-law mass function, \\(dN_4/d\\log M = (2.18^{+0.52}_{-1.40})\\times (M/8\\,M_\\oplus)^{-\\alpha_4}\\) dex\\(^{-1}\\)star\\(^{-1}\\) with \\(\\alpha_4 = 0.96^{+0.47}_{-0.27}\\) for \\(M/M_\\odot < 0.02\\). This implies a total of \\(f= 21^{+23}_{-13}\\) FFP or very wide orbit planets of mass \\(0.33

• Publisher: Cornell University Library, arXiv.org
• Subject: Galactic bulge / Initial mass function / Microlenses / Planetary mass / Planetary orbits / Planetary systems / Power law / Rogue planets / Space telescopes