Search for: All records

Abstract In an effort to identify nearby and unusual cold objects in the solar neighborhood, we searched for previously unidentified moving objects using CatWISE2020 proper motion data combined with machine learning methods. We paired the motion candidates with their counterparts in 2MASS, UHS, and VHS. Then we searched for white dwarf, brown dwarf, and subdwarf outliers on the resulting color–color diagrams. This resulted in the discovery of 16 new dwarfs, including 2 nearby M dwarfs (<30 pc), a possible young L dwarf, a high-motion early-T dwarf, and 3 later-T dwarfs. This research represents a step forward in completing the census of the Sun’s neighbors. 

Abstract A complete accounting of nearby objects—from the highest-mass white dwarf progenitors down to low-mass brown dwarfs—is now possible, thanks to an almost complete set of trigonometric parallax determinations from Gaia, ground-based surveys, and Spitzer follow-up. We create a census of objects within a Sun-centered sphere of 20 pc radius and check published literature to decompose each binary or higher-order system into its separate components. The result is a volume-limited census of ∼3600individualstar formation products useful in measuring the initial mass function across the stellar (<8M_⊙) and substellar (≳5M_Jup) regimes. Comparing our resulting initial mass function to previous measurements shows good agreement above 0.8M_⊙and a divergence at lower masses. Our 20 pc space densities are best fit with a quadripartite power law, $\xi \left(M\right)=\mathit{dN}/\mathit{dM}\propto M^{-\alpha }$, with long-established values ofα= 2.3 at high masses (0.55 <M< 8.00M_⊙), andα= 1.3 at intermediate masses (0.22 <M< 0.55M_⊙), but at lower masses, we findα= 0.25 for 0.05 <M< 0.22M_⊙, andα= 0.6 for 0.01 <M< 0.05M_⊙. This implies that the rate of production as a function of decreasing mass diminishes in the low-mass star/high-mass brown dwarf regime before increasing again in the low-mass brown dwarf regime. Correcting for completeness, we find a star to brown dwarf number ratio of, currently, 4:1, and an average mass per object of 0.41M_⊙.