Probing the shape of the brown dwarf desert around main-sequence A-F-G-type stars using post-common-envelope WD-BD binaries

Abstract

Brown dwarfs (BDs) with masses in the range 40$-$60 $M_ Jup $ are rare around solar-type main-sequence (MS) stars, which gives rise to the brown dwarf desert (BDD). One caveat associated with previous studies of BDD is the relatively limited sample size of MS$-$BD binaries with accurately determined BD masses. We aim to produce a large sample of BD companions with precisely determined masses around MS A-F-G-type stars using observations of post-common-envelope white dwarf (WD)$-$BD binaries. We employed the rapid binary evolution code COMPAS to deduce the properties of MS$-$BD binary progenitors from post-common-envelope WD$-$BD binaries. With this method, we increase the sample of directly observed MS$-$BD binaries, enriching the data available for analyzing the BDD around MS A-F-G-type stars. Our study opens a new window for studying the shape of the BDD around A-F-G-type MS stars in the short-period regime. We find tentative evidence, albeit with a small sample size, that the ``driest'' part of the BDD around A-F-G-type stars may extend into an orbital period of several hundred days. More post-common-envelope WD$-$BD binaries detected in the future will advance our understanding of the BDD around A-F-G-type stars.