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Abstract We measure the Einstein radius of the single-lens microlensing event KMT-2022-BLG-2397 to beθE= 24.8 ± 3.6μas, placing it at the upper shore of the Einstein Desert, 9 ≲θE/μas ≲ 25, between free-floating planets (FFPs) and bulge brown dwarfs (BDs). In contrast to the six BD (25 ≲θE≲ 50) events presented by Gould et al. (2022), which all had giant-star source stars, KMT-2022-BLG-2397 has a dwarf-star source, with angular radiusθast∼ 0.9μas. This prompts us to study the relative utility of dwarf and giant sources for characterizing FFPs and BDs from finite-source point-lens (FSPL) microlensing events. We find “dwarfs” (including main-sequence stars and subgiants) are likely to yield twice as manyθEmeasurements for BDs and a comparable (but more difficult to quantify) improvement for FFPs. We show that neither current nor planned experiments will yield complete mass measurements of isolated bulge BDs, nor will any other planned experiment yield as manyθEmeasurements for these objects as the Korea Microlensing Telescope (KMT). Thus, the currently anticipated 10 yr KMT survey will remain the best way to study bulge BDs for several decades to come.
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This content will become publicly available on July 31, 2026
Microlensing Constraints on the Stellar and Planetary Mass Functions
Abstract The mass function (MF) of isolated objects measured by microlensing consists of both a stellar and a planetary component. We compare the microlensing MFs of A. Gould et al. and T. Sumi et al. to other measurements of the MF. The abundance of brown dwarfs from the tail of the T. Sumi et al. stellar MF is consistent with measurements from the local solar neighborhood. Microlensing free-floating planets (μFFPs) may be free-floating or orbit host stars with semimajor axesa ≳ 10 au and therefore can constrain the populations of both free-floating and wide-orbit planets. Comparisons to radial velocity and direct imaging low-mass companion populations suggest that either most of theμFFP population with masses > 1MJupis bound to hosts more massive than M dwarfs, or some fraction of the observed companion population 1MJup < mp < 0.08M⊙actually comes from the low-mass tail of the stellar MF. TheμFFP population also places strong constraints on planets inferred from debris disks and gaps in protoplanetary disks observed by the Atacama Large Millimeter/submillimeter Array.
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- Award ID(s):
- 2108414
- PAR ID:
- 10654664
- Publisher / Repository:
- AAS Journals
- Date Published:
- Journal Name:
- The Astronomical Journal
- Volume:
- 170
- Issue:
- 2
- ISSN:
- 0004-6256
- Page Range / eLocation ID:
- 132
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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