When the anomalistic, draconitic and sidereal orbital periods do not coincide: the impact of post-Keplerian perturbing accelerations

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Auteur principal: Iorio, Lorenzo
Format: Preprint
Publié: 2023
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author Iorio, Lorenzo
author_facet Iorio, Lorenzo
contents In a purely Keplerian picture, the anomalistic, draconitic and sidereal orbital periods of a test particle orbiting a massive body coincide with each other. Such a degeneracy is removed when a post-Keplerian perturbing acceleration enters the equations of motion yielding generally different corrections to the Keplerian period for the three aforementioned characteristic orbital timescales. They are analytically worked out in the case of the accelerations induced by the general relativistic post-Newtonian gravitoelectromagnetic fields and, to the Newtonian level, by the oblateness of the central body as well. The resulting expressions hold for completely general orbital configurations and spatial orientations of the spin axis of the primary. Astronomical systems characterized by extremely accurate measurements of the orbital periods like, e.g., transiting exoplanets and binary pulsars, may offer potentially viable scenarios for measuring such post--Keplerian features of motion, at least in principle. As an example, the sidereal period of the brown dwarf WD1032 + 011 b is currently known with an uncertainty as small as $\simeq 10^{-5}\,\mathrm{s}$, while its predicted post-Newtonian gravitoelectric correction amounts to $0.07\,\mathrm{s}$; however, the accuracy with which the Keplerian period can be calculated is just 572 s. For the double pulsar PSR J0737-3039, the largest relativistic correction to the anomalistic period amounts to a few tenths of a second, given a measurement error of such a characteristic orbital timescale as small as $\simeq 10^{-6}\,\mathrm{s}$. On the other hand, the Keplerian term can be currently calculated just to a $\simeq 9$ s accuracy. In principle, measuring at least two of the three characteristic orbital periods for the same system independently would allow to cancel out their common Keplerian component provided that their difference is taken.
format Preprint
id arxiv_https___arxiv_org_abs_2310_14311
institution arXiv
publishDate 2023
record_format arxiv
spellingShingle When the anomalistic, draconitic and sidereal orbital periods do not coincide: the impact of post-Keplerian perturbing accelerations
Iorio, Lorenzo
General Relativity and Quantum Cosmology
Earth and Planetary Astrophysics
Space Physics
In a purely Keplerian picture, the anomalistic, draconitic and sidereal orbital periods of a test particle orbiting a massive body coincide with each other. Such a degeneracy is removed when a post-Keplerian perturbing acceleration enters the equations of motion yielding generally different corrections to the Keplerian period for the three aforementioned characteristic orbital timescales. They are analytically worked out in the case of the accelerations induced by the general relativistic post-Newtonian gravitoelectromagnetic fields and, to the Newtonian level, by the oblateness of the central body as well. The resulting expressions hold for completely general orbital configurations and spatial orientations of the spin axis of the primary. Astronomical systems characterized by extremely accurate measurements of the orbital periods like, e.g., transiting exoplanets and binary pulsars, may offer potentially viable scenarios for measuring such post--Keplerian features of motion, at least in principle. As an example, the sidereal period of the brown dwarf WD1032 + 011 b is currently known with an uncertainty as small as $\simeq 10^{-5}\,\mathrm{s}$, while its predicted post-Newtonian gravitoelectric correction amounts to $0.07\,\mathrm{s}$; however, the accuracy with which the Keplerian period can be calculated is just 572 s. For the double pulsar PSR J0737-3039, the largest relativistic correction to the anomalistic period amounts to a few tenths of a second, given a measurement error of such a characteristic orbital timescale as small as $\simeq 10^{-6}\,\mathrm{s}$. On the other hand, the Keplerian term can be currently calculated just to a $\simeq 9$ s accuracy. In principle, measuring at least two of the three characteristic orbital periods for the same system independently would allow to cancel out their common Keplerian component provided that their difference is taken.
title When the anomalistic, draconitic and sidereal orbital periods do not coincide: the impact of post-Keplerian perturbing accelerations
topic General Relativity and Quantum Cosmology
Earth and Planetary Astrophysics
Space Physics
url https://arxiv.org/abs/2310.14311