Hot subdwarf B stars ( sdBs ) are evolved , core helium-burning objects located on the extreme horizontal branch .
Their formation history is still puzzling as the sdB progenitors must lose nearly all of their hydrogen envelope during the red-giant phase .
About half of the known sdBs are in close binaries with periods from 1.2 h to a few days , a fact that implies they experienced a common-envelope phase .
Eclipsing hot subdwarf binaries ( also called HW Virginis systems ) are rare but important objects for determining fundamental stellar parameters .
Even more significant and uncommon are those binaries containing a pulsating sdB , as the mass can be determined independently by asteroseismology .
Here we present a first analysis of the eclipsing hot subdwarf binary V2008-1753 .
The light curve shows a total eclipse , a prominent reflection effect , and low–amplitude pulsations with periods from 150 to 180 s. An analysis of the light– and radial velocity ( RV ) curves indicates a mass ratio close to q = 0.146 , an RV semi-amplitude of K = 54.6 kms ^ { -1 } , and an inclination of i = 86.8 ^ { \circ } .
Combining these results with our spectroscopic determination of the surface gravity , \log g = 5.83 , the best–fitting model yields an sdB mass of 0.47 M _ { \odot } and a companion mass of 69 M _ { Jup } .
As the latter mass is below the hydrogen-burning limit , V2008-1753 represents the first HW Vir system known consisting of a pulsating sdB and a brown dwarf companion .
Consequently , it holds great potential for better constraining models of sdB binary evolution and asteroseismology .