Terrestrial- and Neptune-mass Free-Floating Planet Candidates from the MOA-II 9 yr Galactic Bulge Survey

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dc.citation.issue3
dc.citation.volume166
dc.contributor.authorKoshimoto N
dc.contributor.authorSumi T
dc.contributor.authorBennett DP
dc.contributor.authorBozza V
dc.contributor.authorMróz P
dc.contributor.authorUdalski A
dc.contributor.authorRattenbury NJ
dc.contributor.authorAbe F
dc.contributor.authorBarry R
dc.contributor.authorBhattacharya A
dc.contributor.authorBond IA
dc.contributor.authorFujii H
dc.contributor.authorFukui A
dc.contributor.authorHamada R
dc.contributor.authorHirao Y
dc.contributor.authorIshitani Silva S
dc.contributor.authorItow Y
dc.contributor.authorKirikawa R
dc.contributor.authorKondo I
dc.contributor.authorMatsubara Y
dc.contributor.authorMiyazaki S
dc.contributor.authorMuraki Y
dc.contributor.authorOlmschenk G
dc.contributor.authorRanc C
dc.contributor.authorSatoh Y
dc.contributor.authorSuzuki D
dc.contributor.authorTomoyoshi M
dc.contributor.authorTristram PJ
dc.contributor.authorVandorou A
dc.contributor.authorYama H
dc.contributor.authorYamashita K
dc.date.accessioned2024-05-07T23:25:30Z
dc.date.available2024-05-07T23:25:30Z
dc.date.issued2023-08-16
dc.description.abstractWe 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/μas < 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 μas, 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.
dc.description.confidentialfalse
dc.edition.editionSeptember 2023
dc.identifier.citationKoshimoto N, Sumi T, Bennett DP, Bozza V, Mróz P, Udalski A, Rattenbury NJ, Abe F, Barry R, Bhattacharya A, Bond IA, Fujii H, Fukui A, Hamada R, Hirao Y, Silva SI, Itow Y, Kirikawa R, Kondo I, Matsubara Y, Miyazaki S, Muraki Y, Olmschenk G, Ranc C, Satoh Y, Suzuki D, Tomoyoshi M, Tristram PJ, Vandorou A, Yama H, Yamashita K. (2023). Terrestrial- and Neptune-mass Free-Floating Planet Candidates from the MOA-II 9 yr Galactic Bulge Survey. Astronomical Journal. 166. 3.
dc.identifier.doi10.3847/1538-3881/ace689
dc.identifier.eissn1538-3881
dc.identifier.elements-typejournal-article
dc.identifier.issn0004-6256
dc.identifier.number107
dc.identifier.urihttps://mro.massey.ac.nz/handle/10179/69507
dc.languageEnglish
dc.publisherAmerican Astronomical Society
dc.publisher.urihttps://iopscience.iop.org/article/10.3847/1538-3881/ace689
dc.relation.isPartOfAstronomical Journal
dc.rights(c) 2023 The Author/s
dc.rightsCC BY 4.0
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/
dc.subjectGravitational microlensing exoplanet detection
dc.subjectFree floating planets
dc.subjectExoplanets
dc.titleTerrestrial- and Neptune-mass Free-Floating Planet Candidates from the MOA-II 9 yr Galactic Bulge Survey
dc.typeJournal article
pubs.elements-id480239
pubs.organisational-groupOther
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