Black Hole Formation in the Lower Mass Gap through Mergers and Accretion in AGN Disks

Yang, Yuan-Pei; Gayathri, V.; Bartos, I.; Haiman, Zoltán; Safarzadeh, Mohammadtaher; Tagawa, Hiromichi

doi:10.3847/2041-8213/abb940

Cited by 99 publications

(72 citation statements)

References 60 publications

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“…The 23 M component of GW190814 is also expected to have gained mass through accretion, which would have to be stochastic in angular momentum orientation so as not to spin-up the BH. In a recent study by Yang et al (2020), in their most optimistic case when allowing for up to 0.7 times the Bondi infall rate, they found a merger rate density of 3.1 Gpc −3 yr −1 for binaries that contain a member in the 'mass gap' (defined as 2.2-5 M by the authors). However, only about 10 per cent of these mergers have a mass ratio q ∼ 0.1 and secondary component mass m ∼ 2.6 M similar to GW190814.…”

Section: O B S E Rv E D R At E R At I Omentioning

confidence: 99%

“…One possibility is that the binary BH (bBH) system is embedded in the accretion disc of an active galactic nucleus (AGN), the gas accretion on to the bBH system may operate to shrink the orbit (e.g. Bartos et al 2017;Stone, Metzger & Haiman 2017;McKernan et al 2018;Yang et al 2019aYang et al , 2020, but a potential problem is that this scenario may lead to large BH spins aligned with the AGN disc. Secular perturbation by the supermassive BH's tidal field may subsequently excite large eccentricity in the remnant bBH system and lead to merger, but most likely at a very low rate (Fragione, Leigh & Perna 2019).…”

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confidence: 99%

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On the formation of GW190814

Beniamini

Bonnerot

2020

Monthly Notices of the Royal Astronomical Society

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The LIGO-Virgo collaboration recently reported a puzzling event, GW190814, with component masses of 23 and 2.6M⊙. Motivated by the relatively small rate of such a coalescence (1–$23\rm \, Gpc^{-3}\, yr^{-1}$) and the fact that the mass of the secondary is close to the total mass of known binary neutron star (bNS) systems, we propose that GW190814 was a second-generation merger from a hierarchical triple system, i.e. the remnant from the bNS coalescence was able to merge again with the 23M⊙ black hole (BH) tertiary. We show that this occurs at a sufficiently high probability provided that the semimajor axis of the outer orbit is less than a few AU at the time of bNS coalescence. It remains to be explored whether the conditions for the formation of such tight triple systems are commonly realized in the Universe, especially in low metallicity (≲ 0.1Z⊙) environments. Our model provides a number of predictions. (1) The spin of the secondary in GW190814-like systems is 0.6–0.7. (2) The component mass distribution from a large sample of LIGO sources should have a narrow peak between 2.5 and ∼3.5M⊙, whereas the range between ∼3.5 and ∼5M⊙ stays empty (provided that stellar evolution does not generate such BHs in the ‘mass gap’). (3) About 90 per cent (10 per cent) of GW190814-like events have an eccentricity of e ≳ 2 × 10−3 (≳ 0.1) near gravitational wave frequency of 10 mHz. (4) A significant fraction ($\gtrsim 10{{\ \rm per\ cent}}$) of bNS mergers should have signatures of a massive tertiary at a distance of a few AU in the gravitational waveform. (5) There are 105 undetected radio-quiet bNS systems with a massive BH tertiary in the Milky Way.

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Section: O B S E Rv E D R At E R At I Omentioning

confidence: 99%

mentioning

confidence: 99%

On the formation of GW190814

Beniamini

Bonnerot

2020

Monthly Notices of the Royal Astronomical Society

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“…Assembly via dynamical channels, for instance in a nonsegregated cluster (Clausen et al 2014;Fragione & Banerjee 2020;Rastello et al 2020), hierarchical mergers in multiple systems (Liu & Lai 2021;Lu et al 2021), and binary mergers near galactic nuclei (McKernan et al 2020;Yang et al 2020) may provide a viable formation pathway. However, these generally struggle to produce such highly asymmetric binaries at sufficient rates (see Abbott et al 2020).…”

Section: Implications Of Gw190814-like Mergers For Binary Evolutionmentioning

confidence: 99%

Explodability fluctuations of massive stellar cores enable asymmetric compact object mergers such as GW190814

Antoniadis

Aguilera-Dena

Vigna-Gómez

et al. 2022

A&A

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The first three observing runs with Advanced LIGO and Virgo have resulted in the detection of binary black hole (BBH) mergers with highly unequal mass components, which are difficult to reconcile with standard formation paradigms. The most representative of these is GW190814, a highly asymmetric merger between a 23 M⊙ black hole (BH) and a 2.6 M⊙ compact object. Here, we explore recent results, suggesting that a sizable fraction of stars with pre-collapse carbon-oxygen core masses above 10 M⊙, and extending up to at least 30 M⊙, may produce objects inside the so-called lower mass gap that bridges the division between massive pulsars and BHs in Galactic X-ray binaries. We demonstrate that such an explosion landscape would naturally cause a fraction of massive binaries to produce GW190814-like systems instead of symmetric-mass BBHs. We present examples of specific evolutionary channels leading to the formation of GW190814 and GW200210, a 24 + 2.8 M⊙ merger discovered during the O3b observing run. We estimate the merger-rate density of these events in our scenario to be 𝒪(5%) of the total BBH merger rate. Finally, we discuss the broader implications of this formation channel for compact object populations, and its possible relevance to less asymmetric merger events such as GW200105 and GW200115.

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“…In this case, the resupply timescale increases by a factor of a few on average, which effectively reduces the average accretion rate by a similar factor. On the other hand, if sBH spins evolve due to mergers in migration traps (Bellovary et al 2016;Yang et al 2019Yang et al , 2020 or gas accretion (e.g. Safarzadeh & Haiman 2020) in the AGN disk, i is presumably close to zero, and the formulae for the depletion radius (Eq.…”

Section: C2 Inclined Casesmentioning

confidence: 99%

Can stellar-mass black hole growth disrupt disks of active galactic nuclei? The role of mechanical feedback

Tagawa,

Kimura,

Haiman

et al. 2021

Preprint

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Stellar-mass BHs (sBHs) are predicted to be embedded in active galactic nuclei (AGN) disks due to gravitational drag and in-situ star formation. However, we find that due to a high gas density in an AGN disk environment, compact objects may rapidly grow to intermediate-mass BHs and deplete matter from the AGN disk unless accretion is suppressed by some feedback process(es). These consequences are inconsistent with AGN observations and the dynamics of the Galactic center. Here we consider mechanical feedback mechanisms for the reduction of gas accretion. Rapidly accreting sBHs launch winds and/or jets via the Blandford-Znajek mechanism, which produce high-pressure shocks and cocoons. Such a shock and cocoon can spread laterally in the plane of the disk, eject the outer regions of a circum-sBH disk (CsBD) and puncture a hole in the AGN disk with horizontal size comparable to the disk scale-height. Since the depletion timescale of the bound CsBD is much shorter than the resupply timescale of gas to the sBH, the time-averaged accretion rate onto sBHs is reduced by this process by a factor of ∼ 10-100. This feedback mechanism can therefore help alleviate the sBH over-growth and AGN-disk depletion problems. On the other hand, we find that cocoons of jets can unbind a large fraction of the gas accreting in the disks of less massive SMBHs, which may help explain the dearth of high-Eddington ratio AGNs with SMBH mass 10 5 M ⊙ .

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Black Hole Formation in the Lower Mass Gap through Mergers and Accretion in AGN Disks

Cited by 99 publications

References 60 publications

On the formation of GW190814

On the formation of GW190814

Explodability fluctuations of massive stellar cores enable asymmetric compact object mergers such as GW190814

Can stellar-mass black hole growth disrupt disks of active galactic nuclei? The role of mechanical feedback

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