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Analysis of APOGEE DR12 stellar radial-velocities by Troup et al. (2016)affirmed the existence of the well-known Brown-Dwarf Desert (BDD). Theydetected a dearth of spectroscopic binaries (SB) with periods shorter than$\sim 10$ - $30$ days and secondaries with masses in the range of $\sim0.01$ -$0.1\, M_{\odot}$. We reconsider here their sample of binaries, focusing on 116systems on the main sequence of the Gaia color-magnitude diagram, with mostlyK-dwarf primaries. Using our recently devised algorithm to analyze themass-ratio distribution of a sample of SBs we confirm the BDD existence anddelineate its boundaries. For the K-dwarf APOGEE $1$ - $25$ days binaries, thecompanion-mass range of the BDD is $\sim0.02$ - $0.2\, M_{\odot}$. The massratio distribution of the long-period ($25$ - $500$ days) binaries does notshow any dearth at the $q$-range studied. Instead, their distribution displaysa linear increase in $\log q$, implying a tendency towards low-$q$ values. Thelimits of the BDD do not coincide with the frequently used mass limits of thebrown-dwarf population, sometimes defined as $0.013$ and $0.08\, M_{\odot}$,based on theoretically derived stellar minimum masses for burning deuterium andhydrogen in their cores. Trying to draw the boundaries of the desert, wesuggest either a wedged or trapezoidal shape. We discuss briefly differentscenarios that can account for the formation of the BDD, in terms ofdifferentiating between stellar secondaries and planets in particular, andcompare this desert to the Neptunian desert that can distinguish between Jovianplanets and super Earths of short periods.

monthly notices of the royal astronomical society

Study of the Mass-Ratio Distribution of Spectroscopic Binaries. II. The  Boundaries of the Brown-Dwarf Desert as Seen with the APOGEE Spectroscopic  Binaries