Abstract The Laser Interferometer Space Antenna (LISA) has the potential to reveal wonders
about the fundamental theory of nature at play in the extreme gravity regime, where the …

Very compact objects probe extreme gravitational fields and may be the key to understand
outstanding puzzles in fundamental physics. These include the nature of dark matter, the …

Thanks to unparalleled near-horizon images of the shadows of Messier 87*(M87*) and
Sagittarius A*(Sgr A*) delivered by the Event Horizon Telescope (EHT), two amazing …

Black hole spectroscopy with gravitational waves is an important tool to measure the mass
and spin of astrophysical black holes and to test their Kerr nature. Next-generation ground …

Extreme mass-ratio inspirals (EMRIs) detectable by the Laser Interferometer Space Antenna
are unique probes of the nature of supermassive compact objects. We compute the …

Searches for gravitational waves from compact binaries focus mostly on quasicircular motion
with the rationale that wave emission circularizes the orbit. Here, we study the generality of …

The defining feature of a classical black hole is being a perfect absorber. Any evidence
showing otherwise would indicate a departure from the standard black-hole picture. Energy …

LISA, the Laser Interferometer Space Antenna, will usher in a new era in gravitational-wave
astronomy. As the first anticipated space-based gravitational-wave detector, it will expand …

Ultracompact objects with photonspheres are known to mimic many observational features
of black holes. It has been suggested that anomalous tidal heating or the presence of …

We study gravitational wave (GW) emission in the strong-field regime by a hierarchical triple
system composed of a binary system placed in the vicinity of a supermassive black hole …