Detecting Gravitational Wave Memory without Parent Signals.

Area of Science:

• Astrophysics
• Gravitational-wave Astronomy
• Cosmology

Background:

• Gravitational-wave memory is a permanent detector distortion from energetic astrophysical events like black hole mergers.
• Memory bursts are typically much smaller than their parent gravitational waves.
• Existing detectors have limited sensitivity to high-frequency gravitational waves.

Purpose of the Study:

• Introduce and define "orphan memory": gravitational-wave memory without a detectable parent signal.
• Investigate the generation of orphan memory from high-frequency gravitational-wave bursts (≳kHz).
• Explore the implications of orphan memory for gravitational-wave detector bandwidth and future searches.

Main Methods:

• Analyzed Advanced LIGO data to constrain the existence of high-frequency gravitational waves.
• Modeled the production of orphan memory from hypothetical high-frequency astrophysical sources.
• Assessed the potential for future gravitational-wave observatories to detect orphan memory.

Main Results:

• Advanced LIGO measurements place stringent limits on high-frequency gravitational waves, effectively extending the observable bandwidth.
• High-frequency gravitational-wave bursts are shown to produce orphan memory detectable in the LIGO/Virgo band.
• Searches for orphan memory could significantly enhance our understanding of energetic astrophysical phenomena.

Conclusions:

• Orphan memory represents a novel channel for gravitational-wave astronomy, particularly for high-frequency events.
• Current and future gravitational-wave detectors can be optimized for orphan memory detection.
• The search for orphan memory promises to expand the frontiers of gravitational-wave astrophysics.