Dynamical determination of the quadrupole mass moment of a white dwarf
arXiv:gr-qc/0611126 · doi:10.1007/s10509-007-9415-x
Abstract
In this letter we dynamically determine the quadrupole mass moment Q of the magnetic white dwarf WD 0137-349 by analyzing the period of the recently discovered brown dwarf moving around it in a close 2-hr orbit. It turns out that a purely Newtonian model for the orbit of WD 0137-349B, assumed circular and equatorial, is adequate, given the present-day accuracy in knowing the orbital parameters of such a binary system. Our result is Q=(-1.4615 +/- 0.9004) 10^47 kg m^2 for i=35 deg. It is able to accommodate the 3-sigma significant discrepancy of (1.0 +/- 0.3) 10^-8 s^-2 between the inverse square of the phenomenologically determined orbital period and the inverse square of the calculated Keplerian one. The impact of i, for which a range Delta i of possible values close to 35 deg is considered, is investigated as well.
arXiv commentLaTex2e, 8 pages, no figures, 1 table, 23 references. Discussion on the impact of the inclination added. Thanks to J. Katz. More details on the significant 3-sigma discrepancy between the Keplerian and the phenomenologically measured period added. Two references added. Final version to appear in Astrophysics and Space Science, including the proofs corrections
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