GW190425, GW190521 and GW190814: Three candidate mergers of primordial black holes from the QCD epoch

Abstract

The two recent gravitational-wave events GW190425 and GW190814 from the third observing run of LIGO/Virgo have both a companion which is unexpected if originated from a neutron star or a stellar black hole, with masses $[1.6-2.5]M_{\odot }$ and $[2.5-2.7]M_{\odot }$ and merging rates $460_{-360}^{+1050}$ and $7_{-6}^{+16}$ events/yr/Gpc${}^3$ respectively, at 90\% c.l.. Moreover, the recent event GW190521 has black hole components with masses 67 and $91M_{\odot }$, and therefore lies in the so-called pair-instability mass gap, where there should not be direct formation of stellar black holes. The possibility that all of these compact objects are Primordial Black Holes (PBHs) is investigated. The known thermal history of the Universe predicts that PBH formation is boosted at the time of the QCD transition, inducing a peak in their distribution at this particular mass scale, and a bump around $30-50M_{\odot }$. We find that the merging rates inferred from GW190425, GW190521 and GW190814 are consistent with PBH binaries formed by capture in dense halos in the matter era or in the early universe. At the same time, the rate of black hole mergers around $30M_{\odot }$ and of sub-solar PBH mergers do not exceed the LIGO/Virgo limits. Such PBHs could explain a significant fraction, or even the totality of the Dark Matter, but they must be sufficiently strongly clustered in order to be consistent with current astrophysical limits.

9 pages, 6 figures. New version includes two appendices and a whole new discussion on rates of events

Cited by in corpus (26)

• New Horizons for Fundamental Physics with LISA
• Detection of Early-Universe Gravitational Wave Signatures and Fundamental Physics
• Can we distinguish astrophysical from primordial black holes via the stochastic gravitational wave background?
• Intermediate mass black holes from stellar mergers in young star clusters
• Broad search for gravitational waves from subsolar-mass binaries through LIGO and Virgo's third observing run
• Exploring the high-redshift PBH-$\Lambda$CDM Universe: early black hole seeding, the first stars and cosmic radiation backgrounds
• Detecting Planetary-mass Primordial Black Holes with Resonant Electromagnetic Gravitational Wave Detectors
• GW190814: On the properties of the secondary component of the binary
• Primordial black hole dark matter in dilaton-extended two-field Starobinsky inflation
• QCD color superconductivity in compact stars: color-flavor locked quark star candidate for the gravitational-wave signal GW190814
• Tidal Love Numbers of Novel and Admixed Celestial Objects
• Compact Binary Coalescences: Astrophysical Processes and Lessons Learned
• The stochastic gravitational wave background from close hyperbolic encounters of primordial black holes in dense clusters
• Search for black hole hyperbolic encounters with gravitational wave detectors
• Heavy double neutron stars: birth, mid-life and death
• Primordial black hole mergers from three-body interactions
• The Astro-Primordial Black Hole Merger Rates: a Reappraisal
• A gravitational-wave limit on the Chandrasekhar mass of dark matter
• Testing Primordial Black Holes with multi-band observations of the stochastic gravitational wave background
• Primordial black hole formation for an anisotropic perfect fluid: Initial conditions and estimation of the threshold
• Mass-gap extreme mass ratio inspirals
• Interplay of spin-precession and higher harmonics in the parameter estimation of binary black holes
• Lepton Flavour Asymmetries and the Mass Spectrum of Primordial Black Holes
• Constraints on accreting primordial black holes with the global 21-cm signal
• A Robust Test of the Existence of Primordial Black Holes in Galactic Dark Matter Halos
• Limits on Primordial Black Holes from M87