Gravitational Wave Constraints on Planetary-Mass Primordial Black Holes Using LIGO O3a Data

Area of Science:

• Astrophysics and Cosmology
• Gravitational Wave Astronomy
• Compact Object Physics

Background:

• Primordial black holes (PBHs) are hypothetical black holes formed in the early universe.
• Gravitational waves (GWs) from inspiraling compact objects offer a unique probe for their existence.
• Subsolar mass compact objects, including potential PBHs, are challenging to detect.

Purpose of the Study:

• To conduct the first search for inspiraling planetary-mass compact objects using LIGO-Virgo-KAGRA data.
• To set upper limits on merger rate densities for such systems.
• To constrain the abundance of PBHs as a component of dark matter.

Main Methods:

• Analysis of data from the first half of the LIGO-Virgo-KAGRA third observing run.
• Search for GW signals from equal-mass and highly asymmetric mass-ratio binaries.
• Interpretation of rate density limits to constrain PBH dark matter fraction.

Main Results:

• No significant candidates for inspiraling planetary-mass compact objects were detected.
• Established maximum luminosity distances of O(0.1-100) kpc for the search.
• Derived model-independent upper limits on merger rate densities from O(10^3) to O(10^-7) kpc^-3 yr^-1.

Conclusions:

• The study provides constraints on the fraction of dark matter that could be composed of PBHs.
• For equal-mass PBH binaries, constraints are set for PBH masses between 2x10^-3 M_⊙ and 10^-2 M_⊙.
• Constraints are also derived for asymmetric binaries, complementing microlensing observations.