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IMBH Progenitors from Stellar Collisions in Dense Star Clusters
Elena González Prieto, Newlin C. Weatherford, Giacomo Fragione +2
Very massive stars (VMSs) formed via a sequence of stellar collisions in dense star clusters have been proposed as the progenitors of massive black hole seeds. VMSs could indeed co…
Binary black hole mergers and intermediate-mass black holes in dense star clusters with collisional runaways
Rujuta A. Purohit, Giacomo Fragione, Frederic A. Rasio +2
Intermediate-mass black holes (IMBHs) are believed to be the missing link between the supermassive black holes (BHs) found at the centers of massive galaxies and BHs formed through…
Stellar Escape from Globular Clusters. II. Clusters May Eat Their Own Tails
Newlin C. Weatherford, Frederic A. Rasio, Sourav Chatterjee +3
We apply for the first time the Monte Carlo star cluster modeling method to study tidal tail and stellar stream formation from globular clusters, assuming a circular orbit in a smo…
The dominant mechanism(s) for populating the outskirts of star clusters with neutron star binaries
Nathan W. C. Leigh, Claire S. Ye, Steffani M. Grondin +3
It has been argued that heavy binaries composed of neutron stars (NSs) and millisecond pulsars (MSPs) can end up in the outskirts of star clusters via an interaction with a massive…
Constraining the Properties of Black Hole Seeds from the Farthest Quasars
Giacomo Fragione, Fabio Pacucci
Over 60 years after the discovery of the first quasar, more than such sources are identified in the epoch of reionization at . JWST is now exploring higher redshifts ($z…
Globular cluster formation histories, masses and radii inferred from gravitational waves
Maya Fishbach, Giacomo Fragione
Globular clusters (GCs) are found in all types of galaxies and harbor some of the most extreme stellar systems, including black holes that may dynamically assemble into merging bin…
Demographics of Hierarchical Black Hole Mergers in Dense Star Clusters
Giacomo Fragione, Frederic A. Rasio
With about a hundred mergers of binary black holes (BBHs) detected via gravitational waves by the LIGO-Virgo-KAGRA (LVK) Collaboration, our understanding of the darkest objects in…
Stellar Escape from Globular Clusters. I. Escape Mechanisms and Properties at Ejection
Newlin C. Weatherford, Fulya Kıroğlu, Giacomo Fragione +3
The theory of stellar escape from globular clusters (GCs) dates back nearly a century, especially the gradual evaporation of GCs via two-body relaxation coupled with external tides…
Growing Black Holes through Successive Mergers in Galactic Nuclei: I. Methods and First Results
Dany Atallah, Alessandro A. Trani, Kyle Kremer +4
We present a novel, few-body computational framework designed to shed light on the likelihood of forming intermediate-mass (IM) and supermassive (SM) black holes (BHs) in nuclear s…
Implication of spin constraints by the Event Horizon Telescope on stellar orbits in the Galactic Center
Giacomo Fragione, Abraham Loeb
The center of the Milky Way hosts the closest supermassive black hole, SgrA. Decades of near-infrared observations of our Galactic Center have shown the presence of a small pop…
Gravitational Microlensing Rates in Milky Way Globular Clusters
Fulya Kıroğlu, Newlin C. Weatherford, Kyle Kremer +3
Many recent observational and theoretical studies suggest that globular clusters (GCs) host compact object populations large enough to play dominant roles in their overall dynamica…
Repeated mergers, mass-gap black holes, and formation of intermediate-mass black holes in nuclear star clusters
Giacomo Fragione, Bence Kocsis, Frederic A. Rasio +1
Current theoretical models predict a mass gap with a dearth of stellar black holes (BHs) between roughly and , while, above the range accessible through…
White Dwarf Subsystems in Core-Collapsed Globular Clusters
Kyle Kremer, Nicholas Z. Rui, Newlin C. Weatherford +5
Numerical and observational evidence suggests that massive white dwarfs dominate the innermost regions of core-collapsed globular clusters by both number and total mass. Using NGC…
No Black Holes in NGC 6397
Nicholas Z. Rui, Newlin Weatherford, Kyle Kremer +5
Recently, \citet{vitral2021does} detected a central concentration of dark objects in the core-collapsed globular cluster NGC 6397, which could be interpreted as a subcluster of ste…
Black Hole Mergers from Star Clusters with Top-Heavy Initial Mass Functions
Newlin C. Weatherford, Giacomo Fragione, Kyle Kremer +4
Recent observations of globular clusters (GCs) provide evidence that the stellar initial mass function (IMF) may not be universal, suggesting specifically that the IMF grows increa…
On the Origin of GW190521-like events from repeated black hole mergers in star clusters
Giacomo Fragione, Abraham Loeb, Frederic A. Rasio
LIGO and Virgo have reported the detection of GW190521, from the merger of a binary black hole (BBH) with a total mass around M. While current stellar models limit th…
Black Hole Mergers from Hierarchical Triples in Dense Star Clusters
Miguel A. S. Martinez, Giacomo Fragione, Kyle Kremer +8
Hierarchical triples are expected to be produced by the frequent binary-mediated interactions in the cores of globular clusters. In some of these triples, the tertiary companion ca…
An upper limit on the spin of SgrA based on stellar orbits in its vicinity
Giacomo Fragione, Abraham Loeb
The spin of the massive black hole (BH) at the center of the Milky Way, SgrA, has been poorly constrained so far. We place an upper limit on the spin of SgrA based on the s…
Demographics of triple systems in dense star clusters
Giacomo Fragione, Miguel A. S. Martinez, Kyle Kremer +6
Depending on the stellar type, more than \% and of stars in the field have at least one and two stellar companions, respectively. Hierarchical systems can be a…
Calibrating the binary black hole population in nuclear star clusters through tidal disruption events
Giacomo Fragione, Rosalba Perna, Abraham Loeb
As the sensitivity of gravitational wave (GW) instruments improves and new networks start operating, hundreds of merging stellar-mass black holes (SBHs) and intermediate-mass black…
Demographics of neutron stars in young massive and open clusters
Giacomo Fragione, Sambaran Banerjee
Star clusters appear to be the ideal environment for the assembly of neutron star-neutron star (NS-NS) and black hole-neutron star (BH-NS) binaries. These binaries are among the mo…
Repeated mergers and ejection of black holes within nuclear star clusters
Giacomo Fragione, Joseph Silk
Current stellar evolution models predict a dearth of black holes (BHs) with masses M and M, and intermediate-mass black holes (IMBHs; $\si…
On the eccentricity evolution of massive black hole binaries in stellar backgrounds
Matteo Bonetti, Alexander Rasskazov, Alberto Sesana +6
We study the dynamical evolution of eccentric massive black hole binaries (MBHBs) interacting with unbound stars by means of an extensive set of three body scattering experiments.…
Merging Black Holes in the Low-mass and High-mass Gaps from 2+2 Quadruple Systems
Giacomo Fragione, Abraham Loeb, Frederic A. Rasio
The origin of the black hole (BH) binary mergers observed by LIGO-Virgo is still uncertain, as are the boundaries of the stellar BH mass function. Stellar evolution models predict…