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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  > 1M_Jupis bound to hosts more massive than M dwarfs, or some fraction of the observed companion population 1M_Jup < m_p <  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. 

ABSTRACT WD 0145+234 is a white dwarf that is accreting metals from a circumstellar disc of planetary material. It has exhibited a substantial and sustained increase in 3–5 $$\mu$$m flux since 2018. Follow-up Spitzer photometry reveals that emission from the disc had begun to decrease by late 2019. Stochastic brightening events superimposed on the decline in brightness suggest the liberation of dust during collisional evolution of the circumstellar solids. A simple model is used to show that the observations are indeed consistent with ongoing collisions. Rare emission lines from circumstellar gas have been detected at this system, supporting the emerging picture of white dwarf debris discs as sites of collisional gas and dust production.