Dynamical constraints on some orbital and physical properties of the WD0137-349A/B binary system

In this paper I deal with the WD0137-349 binary system consisting of a white dwarf (WD) and a brown dwarf (BD) in a close circular orbit of about 116 min. I, first, constrain the admissible range of values for the inclination i by noting that, from looking for deviations from the third Kepler law, the quadrupole mass moment Q would assume unlikely large values, incompatible with zero at more than 1-sigma level for i . 35 deg and i & 43 deg. Then, by conservatively assuming that the most likely values for i are those that prevent such an anomalous behavior of Q, i.e. those for which the third Kepler law is an adequate modeling of the orbital period, I obtain i = 39± 2 deg. Such a result is incompatible with the value i = 35 deg quoted in literature by more than 2 sigma. Conversely, it is shown that the white dwarf’s mass range obtained from spectroscopic measurements is compatible with my experimental range, but not for i = 35 deg. As a consequence, my estimate of i yields an orbital separation of a = (0.59 ± 0.05)R and an equilibrium temperature of BD of Teq = (2087± 154)K which differ by 10% and 4%, respectively, from the corresponding values for i = 35 deg.