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

TL;DR

This study uses post-common-envelope white dwarf–brown dwarf binaries and binary evolution modeling to investigate the distribution and characteristics of brown dwarf companions around main-sequence A-F-G stars, addressing the brown dwarf desert.

Contribution

It introduces a novel method combining observations and binary evolution simulations to analyze brown dwarf companions around A-F-G stars, expanding the sample size and understanding of the brown dwarf desert.

Findings

Tentative evidence of the brown dwarf desert extending to several hundred days orbital periods.

Enrichment of the brown dwarf companion sample around A-F-G stars using post-common-envelope binaries.

Identification of potential orbital period range where brown dwarf companions are scarce.

Abstract

Brown dwarfs (BDs) possessing masses within the range $40-60 M_{\rm Jup}$ 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 brown dwarf companions with precisely determined mass around main-sequence A-F-G type stars using observations of post common-envelope white dwarf (WD)$-$BD binaries. We employ the rapid binary evolution code COMPAS to deduce the properties of MS$-$BD binary progenitors from post common-envelope WD$-$BD binaries. This method supplements the directly observed MS$-$BD binary sample, enriching the data available for analyzing BDD around main-sequence A-F-G type stars. Our study opens a new window for studying the shape of BDD around A-F-G type main-sequence stars in the short period regime. We find tentative evidence that the `driest' part of BDD around A-F-G type stars may extend into an orbital period of several hundred days, albeit with a small sample size. More post common-envelope WD$-$BD binaries detected in the future will advance our understanding of the BDD around A-F-G type stars.