Formation of mass gap objects in highly asymmetric mergers

Abstract

The LIGO/Virgo Collaboration (LVC) recently reported the detection of GW190814, a merger of a $23_{-0.9}^{+1.0}{M}_{\odot }$ primary black hole (BH), and a $2.6_{-0.08}^{+0.08}{M}_{\odot }$ secondary. The secondary's mass falls into the mass-gap regime, which refers to the scarcity of compact objects in the mass range of 2-5 $M_{\odot }$. The first clue to the formation of the GW190814 lies in the fact that the primary is a very massive BH. We suggest that the secondary was born as a neutron star (NS) where a significant amount of the supernova ejecta mass from its formation remained bound to the binary due to the presence of the massive BH companion. The bound mass forms a circumbinary accretion disk, and its accretion onto the NS created a mass-gap object. In this scenario, LIGO/Virgo will only detect mass-gap objects in binary mergers with an extreme mass ratio. We also predict a correlation between the mass of the secondary and the mass of the primary in such asymmetric mergers. Our model can be tested with future data from the LVC's third-observing run.

Accepted for publication in ApJ Letters

References in corpus (7)

• GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral
• GW190814: Gravitational Waves from the Coalescence of a 23 M${}_{\odot }$ Black Hole with a 2.6 M${}_{\odot }$ Compact Object
• The Explosion of Helium Stars Evolved With Mass Loss
• Dynamical Formation of Low-Mass Merging Black Hole Binaries like GW151226
• Supernova ejecta with a relativistic wind from a central compact object: a unified picture for extraordinary supernovae
• Formation and merging of Mass Gap Black Holes in Gravitational Wave Merger Events from Wide Hierarchical Quadruple Systems
• Global Stellar Budget for LIGO Black Holes

Cited by in corpus (8)

• Progress in Constraining Nuclear Symmetry Energy Using Neutron Star Observables Since GW170817
• Black Hole Formation in the Lower Mass Gap through Mergers and Accretion in AGN Disks
• Probing the nuclear equation of state from the existence of a $\sim 2.6M_{\odot }$ neutron star: the GW190814 puzzle
• $R$-mode Stability of GW190814's Secondary Component as a Supermassive and Superfast Pulsar
• Dynamical formation of the GW190814 merger
• Modelling a $2.5M_{\odot }$ Compact Star with Quark Matter
• Nuclear Matter and Neutron Stars from Relativistic Brueckner-Hartree-Fock Theory
• A Common Origin for Low Mass Ratio Events Observed by LIGO and Virgo in the First Half of the Third Observing Run