Viscous matter can damp gravitational waves more than expected

Working in Schwarzschild and static spherically symmetric spacetimes — more realistic than flat space — the authors find that gravitational wave damping by viscous matter is strongly enhanced when the source-matter distance falls below one wavelength. The energy deposited in the fluid can be large enough to cause significant signal attenuation or drive gamma-ray burst emission. Core-collapse supernovae, binary neutron star mergers, and black hole mergers with surrounding accretion disks are identified as plausible astrophysical settings where the effect would matter.