The propagation delay in the timing of a pulsar orbiting a supermassive black hole

verfasst von: Eva Hackmann, Arnab Dhani
Abstract: The observation of a pulsar closely orbiting the galactic center supermassive black hole would open the window for an accurate determination of the black hole parameters and for new tests of General Relativity. An important relativistic effect which has to be taken into account in the timing model is the propagation delay of the pulses in the gravitational field of the black hole. Due to the extreme mass ratio of the pulsar and the supermassive back hole we use the test particle limit to derive an exact analytical formula for the propagation delay in a Schwarzschild spacetime. We then compare this result to the propagation delays derived in the usually employed post-Newtonian approximation, in particular to the Shapiro delay up to the second post-Newtonian order. For edge-on orbits we also consider modifications of the Shapiro delay which take the lensing effects into account. Our results are then used to assess the accuracy of the different orders of the post-Newtonian approximation of the propagation delay. This comparison indicates that for (nearly) edge-on orbits the new exact delay formula should be used.
Externe Organisation(en): Zentrum für angewandte Raumfahrttechnologie und Mikrogravitation (ZARM)
Universität Bielefeld
Pennsylvania State University
Indiana Institute of Technology (Indiana Tech)
Typ: Artikel
Journal: General relativity and gravitation
Band: 51
ISSN: 0001-7701
Publikationsdatum: 04.03.2019
Publikationsstatus: Veröffentlicht
Peer-reviewed: Ja
ASJC Scopus Sachgebiete: Physik und Astronomie (sonstige)
Elektronische Version(en): https://doi.org/10.1007/s10714-019-2517-2 (Zugang: Geschlossen)

BibTeX

@article{cd00e06834974438a8c8e17d95264fc3,
title = "The propagation delay in the timing of a pulsar orbiting a supermassive black hole",
abstract = "The observation of a pulsar closely orbiting the galactic center supermassive black hole would open the window for an accurate determination of the black hole parameters and for new tests of General Relativity. An important relativistic effect which has to be taken into account in the timing model is the propagation delay of the pulses in the gravitational field of the black hole. Due to the extreme mass ratio of the pulsar and the supermassive back hole we use the test particle limit to derive an exact analytical formula for the propagation delay in a Schwarzschild spacetime. We then compare this result to the propagation delays derived in the usually employed post-Newtonian approximation, in particular to the Shapiro delay up to the second post-Newtonian order. For edge-on orbits we also consider modifications of the Shapiro delay which take the lensing effects into account. Our results are then used to assess the accuracy of the different orders of the post-Newtonian approximation of the propagation delay. This comparison indicates that for (nearly) edge-on orbits the new exact delay formula should be used.",
keywords = "Black holes, Light propagation, Pulsar timing",
author = "Eva Hackmann and Arnab Dhani",
note = "Publisher Copyright: {\textcopyright} 2019, Springer Science+Business Media, LLC, part of Springer Nature.",
year = "2019",
month = mar,
day = "4",
doi = "10.1007/s10714-019-2517-2",
language = "English",
volume = "51",
journal = "General relativity and gravitation",
issn = "0001-7701",
publisher = "Springer New York",
number = "3",
}