Directional limits on persistent gravitational waves using data from Advanced LIGO's first two observing runs

Understand

We perform an unmodeled search for persistent, directional gravitational wave (GW) sources using data from the first and second observing runs of Advanced LIGO.

• We do not find evidence for any GW signals.
• We place limits on the broadband GW flux emitted at 25~Hz from point sources with a power law spectrum at $F_{\alpha,\Theta} <(0.05-25)\times 10^{-8} ~{\rm erg\,cm^{-2}\,s^{-1}\,Hz^{-1}}$ and the (normalized) energy density spectrum in GWs at 25 Hz from extended sources at $\Omega_{\alpha}(\Theta) <(0.19-2.89)\times 10^{-8} ~{\rm sr^{-1}}$ where $\alpha$ is the spectral index of the energy density spectrum.
• These represent improvements of $2.5-3\times$ over previous limits.