HW Vir systems are rare evolved eclipsing binaries composed by a hot compact star and a low-mass main-sequence star in a close orbit . These systems provide a direct way to measure the fundamental properties , e.g . masses and radii , of their components , hence they are crucial to study the formation of sdB stars and low-mass white dwarfs , the common-envelope phase , and the pre-phase of cataclysmic variables . Here we present a detailed study of HS 2231+2441 , an HW Vir type system , by analysing BVR _ { C } I _ { C } photometry and phase-resolved optical spectroscopy . The spectra of this system , which are dominated by the primary component features , were fitted using NLTE models providing effective temperature T _ { eff } = 28500 \pm 500 K , surface gravity \log g = 5.40 \pm 0.05 ~ { } cm s ^ { -2 } , and helium abundance \log ( n ( He ) / n ( H ) ) = -2.52 \pm 0.07 . Geometrical orbit and physical parameters were derived by modelling simultaneously the photometric and spectroscopic data using the Wilson-Devinney code . We derive two possible solutions for HS 2231+2441 that provide component ’ s masses : M _ { 1 } = 0.19 M _ { \odot } and M _ { 2 } = 0.036 M _ { \odot } or M _ { 1 } = 0.288 M _ { \odot } and M _ { 2 } = 0.046 M _ { \odot } . Considering the possible evolutionary channels to form a compact hot star , the primary of HS 2231+2441 probably evolved through the red-giant branch scenario and does not have a helium-burning core , which is consistent with a low-mass white dwarf . Both solutions are consistent with a brown dwarf as the secondary .