Eccentricity evolution of compact binaries and applications to gravitational-wave physics

Abstract

Searches for gravitational waves from compact binaries focus mostly on quasi-circular motion, with the rationale that wave emission circularizes the orbit. Here, we study the generality of this result, when astrophysical environments (e.g., accretion disks) or other fundamental interactions are taken into account. We are motivated by possible electromagnetic counterparts to binary black hole coalescences and orbits, but also by the possible use of eccentricity as a smoking-gun for new physics. We find that: i) backreaction from radiative mechanisms, including scalars, vectors and gravitational waves circularize the orbital motion. ii) by contrast, environmental effects such as accretion and dynamical friction increase the eccentricity of binaries. Thus, it is the competition between radiative mechanisms and environmental effects that dictates the eccentricity evolution. We study this competition within an adiabatic approach, including gravitational radiation and dynamical friction forces. We show that that there is a critical semi-major axis below which gravitational radiation dominates the motion and the eccentricity of the system decreases. However, the eccentricity inherited from the environment-dominated stage can be substantial, and in particular can affect LISA sources. We provide examples for GW190521-like sources.

Gravitational and electromagnetic radiation from binary black holes with electric and magnetic charges: Circular orbits on a cone

“…The energy emission (17) due to electromagnetic radiation leads to the averaged energy loss rate PEM = lim…”

“…Compared to Schwarzschild black holes, charged black holes have rich phenomena. Recently, charged black holes have been discussed extensively [9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25]. Binary black holes with charges emit not only gravitational radiation but also electromagnetic radiation.…”

Radiation-reaction force and multipolar waveforms for eccentric, spin-aligned binaries in the effective-one-body formalism

“…While the expected fraction of eccentric GW observations with current detectors is small, neglecting eccentricity for the parameter inference can cause significant bias [22]. This becomes more relevant for LISA where a large fraction of stellar-mass binaries are expected to be eccentric [23][24][25][26][27]. Hence, it is important to develop accurate waveform models for eccentric binaries to detect them, infer their properties, and shed light on their astrophysical environment and formation channels.…”