Pulsar-black hole binaries: prospects for new gravity tests with future radio telescopes
Abstract
The anticipated discovery of a pulsar in orbit with a black hole is expected to provide a unique
laboratory for black hole physics and gravity. In this context, the next generation of radio
telescopes, like the Five-hundred-meter Aperture Spherical radio Telescope (FAST) and the
Square Kilometre Array (SKA), with their unprecedented sensitivity, will play a key role. In
this paper, we investigate the capability of future radio telescopes to probe the space–time
of a black hole and test gravity theories by timing a pulsar orbiting a stellar-mass black hole
(SBH). Based on mock data simulations, we show that a few years of timing observations of a
sufficiently compact pulsar–SBH (PSR–SBH) system with future radio telescopes would allow
precise measurements of the black hole mass and spin. A measurement precision of 1 per cent
can be expected for the spin. Measuring the quadrupole moment of the black hole, needed to
test general relativity’s (GR’s) no-hair theorem, requires extreme system configurations with
compact orbits and a large SBH mass. Additionally, we show that a PSR–SBH system can
lead to greatly improved constraints on alternative gravity theories even if they predict black
holes (practically) identical to GR’s. This is demonstrated for a specific class of scalar–tensor
theories. Finally, we investigate the requirements for searching for PSR–SBH systems. It is
shown that the high sensitivity of the next generation of radio telescopes is key for discovering
compact PSR–SBH systems, as it will allow for sufficiently short survey integration times.
Origin : Publisher files allowed on an open archive
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