Pulsar timing sensitivities to gravitational waves from relativistic metric theories of gravity

Abstract

Pulsar timing experiments aimed at the detection of gravitational radiation have been performed for decades now. With the forthcoming construction of large arrays capable of tracking multiple millisecond pulsars, it is very likely we will be able to make the first detection of gravitational radiation in the nano-Hertz band, and test Einstein's theory of relativity by measuring the polarization components of the detected signals. Since a gravitational wave predicted by the most general relativistic metric theory of gravity accounts for six polarization modes (the usual two Einstein's tensor polarizations as well as two vector and two scalar wave components), we have estimated the single-antenna sensitivities to these six polarizations. We find pulsar timing experiments to be significantly more sensitive, over their entire observational frequency band (≈ 10 −9 − 10 −6 Hz), to scalar-longitudinal and vector waves than to scalar-transverse and tensor waves. At 10 −7 Hz and with pulsars at a distance of 1 kpc, for instance, we estimate an average sensitivity to scalar-longitudinal waves that is more than two orders of magnitude better than the sensitivity to tensor waves. Our results imply that a direct detection of gravitational radiation by pulsar timing will result into a test of the theory of general relativity that is more stringent than that based on monitoring the decay of the orbital period of a binary system. 95.36.+x, 95.30.Sf

Detection of non-Einsteinian Gravitational Waves using a Pulsar Timing Array

“…Furthermore, larger values of the non-transverse overlap reduction functions (Figs. 2) indicate increased sensitivity to these modes, in agreement with the results of (Lee et al 2008;Alves and Tinto 2011). This behavior is absent for transverse GW polarization modes.…”

The Confrontation between General Relativity and Experiment

“…The capability of space-based interferometers to measure the polarization modes was assessed in detail in [388, 302]. For pulsar timing arrays, see [245, 14, 74]. …”

Stochastic backgrounds in alternative theories of gravity: Overlap reduction functions for pulsar timing arrays

“…Alves and Tinto [22] have estimated antenna sensitivities to GWs of all six polarization modes by assuming a signal-to-noise ratio of 1 over 10 years and calculating the noise spectrum. Their results indicate an increase of two to three orders of magnitude in sensitivity to scalar-longitudinal mode GWs compared to that of plus and cross mode GWs.…”

“…For pulsar timing arrays the form of the correlation between pulsar pairs as a function of pulsar pair angular separation depends on the polarization content of the theory [21]. Additionally it has been shown that pulsar timing arrays have a greater sensitivity to longitudinal and vector polarization modes than to transverse modes [21,22].…”