Gravitational waves from binary supermassive black holes missing in pulsar observations.

Area of Science:

• Astrophysics
• Cosmology
• Gravitational Wave Astronomy

Background:

• Supermassive black hole binaries are formed during galaxy mergers.
• These binaries are predicted to emit gravitational waves, creating a stochastic background.
• This background can modulate the arrival times of radio pulsar signals.

Purpose of the Study:

• To constrain the characteristic amplitude of the stochastic gravitational wave background.
• To test current models of supermassive black hole binary evolution.

Main Methods:

• Utilized observations of millisecond pulsars from the Parkes radio telescope.
• Applied pulsar timing analysis to detect modulations caused by gravitational waves.

Main Results:

• Established an upper limit for the characteristic amplitude of the gravitational wave background, A(c,yr), at <1.0 × 10(-15) with 95% confidence.
• This limit excludes predicted ranges from current models with 91% to 99.7% probability.

Conclusions:

• Current models of supermassive black hole binary evolution may require revision.
• Binary evolution in galactic centers might be significantly stalled or accelerated.
• Future observations with higher cadence and shorter wavelengths could improve sensitivity to gravitational waves.