# 28th Texas Symposium on Relativistic Astrophysics

13-18 December 2015
International Conference Centre Geneva
Europe/Zurich timezone

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

17 Dec 2015, 16:15
21m
Level 2, Room 13 (International Conference Centre Geneva)

### Level 2, Room 13

#### International Conference Centre Geneva

17 Rue de Varembé, 1211 Geneva

### Speaker

Dr Stefan Oslowski (Bielefeld University / MPIfR Bonn)

### Description

Gravitational waves are expected to be radiated by supermassive black hole binaries formed during galaxy mergers. A stochastic superposition of gravitational waves from all such binary systems will modulate the arrival times of pulses from radio pulsars. Using observations of millisecond pulsars obtained with the Parkes radio telescope, we constrain the characteristic amplitude of this background, $A_{\rm c,yr}$, to be < $1.0\times10^{-15}$ with 95% confidence. This limit excludes predicted ranges for $A_{\rm c,yr}$ from current models with 91-99.7% probability. We conclude that binary evolution is either stalled or dramatically accelerated by galactic-center environments, and that higher-cadence and shorter-wavelength observations would result in an increased sensitivity to gravitational waves.
Collaboration Parkes Pulsar Timing Array

### Primary author

Dr Ryan Shannon (CASS)

### Co-author

Dr Stefan Oslowski (Bielefeld University / MPIfR Bonn)