The Astronomical Journal (Jan 2023)
Terrestrial- and Neptune-mass Free-Floating Planet Candidates from the MOA-II 9 yr Galactic Bulge Survey
- Naoki Koshimoto,
- Takahiro Sumi,
- David P. Bennett,
- Valerio Bozza,
- Przemek Mróz,
- Andrzej Udalski,
- Nicholas J. Rattenbury,
- Fumio Abe,
- Richard Barry,
- Aparna Bhattacharya,
- Ian A. Bond,
- Hirosane Fujii,
- Akihiko Fukui,
- Ryusei Hamada,
- Yuki Hirao,
- Stela Ishitani Silva,
- Yoshitaka Itow,
- Rintaro Kirikawa,
- Iona Kondo,
- Yutaka Matsubara,
- Shota Miyazaki,
- Yasushi Muraki,
- Greg Olmschenk,
- Clément Ranc,
- Yuki Satoh,
- Daisuke Suzuki,
- Mio Tomoyoshi,
- Paul J. Tristram,
- Aikaterini Vandorou,
- Hibiki Yama,
- Kansuke Yamashita,
- MOA Collaboration
Affiliations
- Naoki Koshimoto
- ORCiD
- Code 667, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA ; [email protected]; Department of Astronomy, University of Maryland , College Park, MD 20742, USA; Center for Research and Exploration in Space Science and Technology , NASA/GSFC, Greenbelt, MD 20771, USA; Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Takahiro Sumi
- ORCiD
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- David P. Bennett
- ORCiD
- Code 667, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA ; [email protected]; Department of Astronomy, University of Maryland , College Park, MD 20742, USA; Center for Research and Exploration in Space Science and Technology , NASA/GSFC, Greenbelt, MD 20771, USA
- Valerio Bozza
- ORCiD
- Dipartimento di Fisica “E.R. Caianiello,” Universitá di Salerno , Via Giovanni Paolo 132, Fisciano I-84084, Italy; Istituto Nazionale di Fisica Nucleare , Sezione di Napoli, Via Cintia, Napoli I-80126, Italy
- Przemek Mróz
- ORCiD
- Astronomical Observatory, University of Warsaw Al. Ujazdowskie 4 , 00-478 Warszawa, Poland
- Andrzej Udalski
- ORCiD
- Astronomical Observatory, University of Warsaw Al. Ujazdowskie 4 , 00-478 Warszawa, Poland
- Nicholas J. Rattenbury
- ORCiD
- Department of Physics, University of Auckland , Private Bag 92019, Auckland, New Zealand
- Fumio Abe
- Institute for Space-Earth Environmental Research, Nagoya University , Nagoya 464-8601, Japan
- Richard Barry
- ORCiD
- Code 667, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA ; [email protected]
- Aparna Bhattacharya
- Code 667, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA ; [email protected]; Department of Astronomy, University of Maryland , College Park, MD 20742, USA; Center for Research and Exploration in Space Science and Technology , NASA/GSFC, Greenbelt, MD 20771, USA
- Ian A. Bond
- Institute of Natural and Mathematical Sciences, Massey University , Auckland 0745, New Zealand
- Hirosane Fujii
- Institute for Space-Earth Environmental Research, Nagoya University , Nagoya 464-8601, Japan
- Akihiko Fukui
- ORCiD
- Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan; Instituto de Astrofísica de Canarias , Vía Láctea s/n, E-38205 La Laguna, Tenerife, Spain
- Ryusei Hamada
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Yuki Hirao
- ORCiD
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Stela Ishitani Silva
- Code 667, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA ; [email protected]; Center for Research and Exploration in Space Science and Technology , NASA/GSFC, Greenbelt, MD 20771, USA; Department of Physics, The Catholic University of America , Washington, DC 20064, USA
- Yoshitaka Itow
- ORCiD
- Institute for Space-Earth Environmental Research, Nagoya University , Nagoya 464-8601, Japan
- Rintaro Kirikawa
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Iona Kondo
- ORCiD
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Yutaka Matsubara
- ORCiD
- Institute for Space-Earth Environmental Research, Nagoya University , Nagoya 464-8601, Japan
- Shota Miyazaki
- ORCiD
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Yasushi Muraki
- ORCiD
- Institute for Space-Earth Environmental Research, Nagoya University , Nagoya 464-8601, Japan
- Greg Olmschenk
- ORCiD
- Code 667, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA ; [email protected]
- Clément Ranc
- ORCiD
- Sorbonne Université, CNRS, UMR 7095, Institut d’Astrophysique de Paris , 98 bis bd Arago, F-75014 Paris, France
- Yuki Satoh
- ORCiD
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Daisuke Suzuki
- ORCiD
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Mio Tomoyoshi
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Paul J. Tristram
- University of Canterbury Mt. John Observatory , P.O. Box 56, Lake Tekapo 8770, New Zealand
- Aikaterini Vandorou
- Code 667, NASA Goddard Space Flight Center , Greenbelt, MD 20771, USA ; [email protected]; Department of Astronomy, University of Maryland , College Park, MD 20742, USA; Center for Research and Exploration in Space Science and Technology , NASA/GSFC, Greenbelt, MD 20771, USA
- Hibiki Yama
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- Kansuke Yamashita
- Department of Earth and Space Science, Graduate School of Science, Osaka University , Toyonaka, Osaka 560-0043, Japan
- MOA Collaboration
- DOI
- https://doi.org/10.3847/1538-3881/ace689
- Journal volume & issue
-
Vol. 166,
no. 3
p. 107
Abstract
We report the discoveries of low-mass free-floating planet (FFP) candidates from the analysis of 2006–2014 MOA-II Galactic bulge survey data. In this data set, we found 6111 microlensing candidates and identified a statistical sample consisting of 3535 high-quality single-lens events with Einstein radius crossing times in the range 0.057 < t _E /days < 757, including 13 events that show clear finite-source effects with angular Einstein radii of 0.90 < θ _E / μ as < 332.54. Two of the 12 events with t _E < 1 day have significant finite-source effects, and one event, MOA-9y-5919, with t _E = 0.057 ± 0.016 days and θ _E = 0.90 ± 0.14 μ as, is the second terrestrial-mass FFP candidate to date. A Bayesian analysis indicates a lens mass of ${0.75}_{-0.46}^{+1.23}$ M _⊕ for this event. The low detection efficiency for short-duration events implies a large population of low-mass FFPs. The microlensing detection efficiency for low-mass planet events depends on both the Einstein radius crossing times and the angular Einstein radii, so we have used image-level simulations to determine the detection efficiency dependence on both t _E and θ _E . This allows us to use a Galactic model to simulate the t _E and θ _E distribution of events produced by the known stellar populations and models of the FFP distribution that are fit to the data. Methods like this will be needed for the more precise FFP demographics determinations from Nancy Grace Roman Space Telescope data.
Keywords
