Ionization of Gravitational Atoms
Journal
Physical Review D
Journal Volume
105
Journal Issue
11
Date Issued
2021-12-30
Author(s)
Abstract
Superradiant instabilities may create clouds of ultralight bosons around
rotating black holes, forming so-called "gravitational atoms." It was recently
shown that the presence of a binary companion can induce resonant transitions
between bound states of these clouds, whose backreaction on the binary's orbit
leads to characteristic signatures in the emitted gravitational waves. In this
work, we show that the interaction with the companion can also trigger
transitions from bound to unbound states of the cloud -- a process that we
refer to as "ionization" in analogy with the photoelectric effect in atomic
physics. The orbital energy lost in the process overwhelms the losses due to
gravitational wave emission and contains sharp features carrying information
about the energy spectrum of the cloud. Moreover, we also show that if the
companion is a black hole, then the part of the cloud impinging on the event
horizon will be absorbed. This "accretion" leads to a significant increase of
the companion's mass, which alters the dynamical evolution and ensuing waveform
of the binary. We argue that a combined treatment of resonances, ionization,
and accretion is crucial to discover and characterize gravitational atoms with
upcoming gravitational wave detectors.
Subjects
General Relativity and Quantum Cosmology; General Relativity and Quantum Cosmology; High Energy Physics - Phenomenology; High Energy Physics - Theory
SDGs
Description
34+21 pages, 16 figures
Type
journal article