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

TL;DR

This study constrains the orbital inclination and related physical properties of the WD0137-349 binary system using deviations from Kepler's law, providing more accurate estimates that challenge previous literature values.

Contribution

The paper introduces a method to constrain the orbital inclination of WD0137-349 by analyzing deviations from Kepler's law, refining previous estimates and deriving related physical parameters.

Findings

Inclination i is approximately 39 degrees with a 2-degree uncertainty.

Derived orbital separation is about 0.59 solar radii.

Estimated brown dwarf temperature is roughly 2087 K.

Abstract

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_Sun and an equilibrium temperature of BD of T_eq=(2087 +/- 154)K which differ by 10% and 4%, respectively, from the corresponding values for i=35 deg.