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The Stellar Merger Scenario for Black Holes in the Pair-instability Gap
Solar and Stellar Astrophysics · Submitted 1 Oct 2020
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim This is small enough that at core-collapse our models are retaining sufficient mass to form black holes in the pair-instability gap similar to the recent ones detected by LIGO/Virgo.
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The abstract, sentence by sentence
The recent detection of GW190521 stimulated ideas on how to populate the predicted black hole pair-instability mass gap. One proposed scenario is the dynamical merger of two stars below the pair instability regime forming a star with a small core and an over-sized envelope. We explore this scenario with detailed stellar evolution calculations, starting with ad-hoc initial conditions enforcing no core growth during the merger. We outline the main challenges this scenario has to overcome, in particular the requirement to retain enough of its mass at merger time, in the subsequent evolution, and at core-collapse. We found that these massive merger products are likely helium-rich, and spend most of their remaining lifetime within regions of the Herzsprung-Russell diagram where envelope instabilities akin to luminous blue variable (LBV) eruptions are expected. An energetic estimate of the amount of mass loss neglecting the back-reaction of the star suggests that the total amount of mass that can be removed at low metallicity is . 1 M . This is small enough that at core-collapse our models are retaining sufficient mass to form black holes in the pair-instability gap similar to the recent ones detected by LIGO/Virgo. However, mass loss at the time of merger and the neutrino-driven mass loss at core collapse still need to be quantified for these models in order to confirm the viability of this scenario.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | The recent detection of GW190521 stimulated ideas on how to populate the predicted black hole pair-instability mass gap. | background 1.00 | 0.04 | 0.02 | asserted 0.86 |
| s1 | One proposed scenario is the dynamical merger of two stars below the pair instability regime forming a star with a small core and an over-sized envelope. | background 0.99 | 0.05 | 0.04 | asserted 0.55 |
| s2 | We explore this scenario with detailed stellar evolution calculations, starting with ad-hoc initial conditions enforcing no core growth during the merger. | method 0.84 | 0.91 | 0.03 | asserted 0.96 |
| s3 | We outline the main challenges this scenario has to overcome, in particular the requirement to retain enough of its mass at merger time, in the subsequent evolution, and at core-collapse. | contribution 0.46 | 0.64 | 0.05 | asserted 0.96 |
| s4 | We found that these massive merger products are likely helium-rich, and spend most of their remaining lifetime within regions of the Herzsprung-Russell diagram where envelope instabilities akin to luminous blue variable (LBV) eruptions are expected. | result 0.98 | 0.91 | 0.12 | hedged possibility 0.90 |
| s5 | An energetic estimate of the amount of mass loss neglecting the back-reaction of the star suggests that the total amount of mass that can be removed at low metallicity is . 1 M . | result 0.83 | 0.82 | 0.07 | asserted 0.86 |
| s6 | This is small enough that at core-collapse our models are retaining sufficient mass to form black holes in the pair-instability gap similar to the recent ones detected by LIGO/Virgo. | interpretation 0.52 | 0.86 | 0.61 | asserted 0.94 |
| s7 | However, mass loss at the time of merger and the neutrino-driven mass loss at core collapse still need to be quantified for these models in order to confirm the viability of this scenario. | limitation 0.64 | 0.22 | 0.19 | asserted 0.58 |
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The paper
Original abstract
The recent detection of GW190521 stimulated ideas on how to populate the predicted black hole pair-instability mass gap. One proposed scenario is the dynamical merger of two stars below the pair instability regime forming a star with a small core and an over-sized envelope. We explore this scenario with detailed stellar evolution calculations, starting with ad-hoc initial conditions enforcing no core growth during the merger. We outline the main challenges this scenario has to overcome, in particular the requirement to retain enough of its mass at merger time, in the subsequent evolution, and at core-collapse. We found that these massive merger products are likely helium-rich, and spend most of their remaining lifetime within regions of the Herzsprung-Russell diagram where envelope instabilities akin to luminous blue variable (LBV) eruptions are expected. An energetic estimate of the amount of mass loss neglecting the back-reaction of the star suggests that the total amount of mass that can be removed at low metallicity is . 1 M . This is small enough that at core-collapse our models are retaining sufficient mass to form black holes in the pair-instability gap similar to the recent ones detected by LIGO/Virgo. However, mass loss at the time of merger and the neutrino-driven mass loss at core collapse still need to be quantified for these models in order to confirm the viability of this scenario.
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References
How the literature uses it
9 arXiv papers cite this in 11 sentences
Papers citing it · 7 sentences without a confident label
Uses its method or tool 1 paper
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However, we can do a common posterior estimation [ref] by assuming that all the luminosity that exceeds the Eddington limit can be used to remove mass that leaves the star with a velocity similar to the escape speed.
Maximum Black Hole mass across Cosmic Time · Potential extra Mass loss near the Eddington Limit · 0.92
Cites it as background 3 papers
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After its announcement, many studies explored the properties and origin of this unique event, including its statistical interpretation and implication [ref] , highly eccentric orbit [ref] , uncertainty of the mass gap [ref] , repeated BH mergers and stellar collisions in dense star clusters (e.g., [ref] ), mergers of ultra dwarf galaxies [ref] , accretion in dense molecular clouds [ref] , and primordial BHs [ref] .
The Population III origin of GW190521 · Introduction · 0.99
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Pre-explosion mechanisms include mass loss suppression in low-metallicity ($Z≲10^-3$) progenitors [ref] ; collisions between massive stars in dense clusters [ref] ;
Cosmologically coupled compact objects: a single parameter model for LIGO--Virgo mass and redshift distributions · Introduction · 0.87
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Such high-mass systems are essential probes of the role of hierarchical mergers [ref] and pair-instability physics [ref] in binary formation and evolution.
GW190521: tracing imprints of spin-precession on the most massive black hole binary · Introduction · 0.92
What it cites · 5 sentences without a confident label
Cites as background 12 papers
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These BHs might not be the direct remnants of stars, but rather the product of second-generation BH mergers in a (nuclear) cluster [ref] or AGN disk [ref] , of accretion from gas clouds [ref] , or possibly primordial BHs [ref] .
On the Origin of GW190521-like events from repeated black hole mergers in star clusters · Introduction · 0.91
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These BHs might not be the direct remnants of stars, but rather the product of second-generation BH mergers in a (nuclear) cluster [ref] or AGN disk [ref] , of accretion from gas clouds [ref] , or possibly primordial BHs [ref] .
Mass and rate of hierarchical black hole mergers in young, globular and nuclear star clusters · Introduction · 0.91
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These BHs might not be the direct remnants of stars, but rather the product of second-generation BH mergers in a (nuclear) cluster [ref] or AGN disk [ref] , of accretion from gas clouds [ref] , or possibly primordial BHs [ref] .
Populating the upper black hole mass gap through stellar collisions in young star clusters · Introduction · 0.91
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