The Nature of the IMBH Candidate CXO J133815.6+043255: High-frequency Radio Emission

Smith, Krista Lynne; Magno, Macon; Tripathi, Ashutosh

doi:10.3847/1538-4357/acf4f8

Cited by 4 publications

(1 citation statement)

References 59 publications

(105 reference statements)

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“…BHs with masses in between these two regimes are labeled intermediate-mass BHs (IMBHs); for a review see Greene et al (2020). While IMBHs could play a fundamental role in the evolution of galaxies and could be a source of tidal disruption events and gravitational waves (GWs), their existence has not been confirmed beyond a reasonable doubt (e.g., Jardel & Gebhardt 2012;Neumayer & Walcher 2012;Graham & Scott 2013;Mezcua 2017;Nguyen et al 2018;Perley et al 2019;Smith et al 2023).…”

Section: Introductionmentioning

confidence: 99%

Binary Black Hole Mergers and Intermediate-mass Black Holes in Dense Star Clusters with Collisional Runaways

Purohit,

Fragione,

Rasio

et al. 2024

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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 core collapse. One of the proposed mechanisms for their formation is a collisional runaway process in high-density young star clusters, where an unusually massive object forms through repeated stellar collisions and mergers, eventually collapsing to form an IMBH. This seed IMBH could then grow further through binary mergers with other stellar-mass BHs. Here we investigate the gravitational-wave (GW) signals produced during these later IMBH–BH mergers. We use a state-of-the-art semi-analytic approach to study the stellar dynamics and to characterize the rates and properties of IMBH–BH mergers. We also study the prospects for detection of these mergers by current and future GW observatories, both space-based (LISA) and ground-based (LIGO Voyager, Einstein Telescope, and Cosmic Explorer). We find that most of the merger signals could be detected, with some of them being multiband sources. Therefore, GWs represent a unique tool to test the collisional runaway scenario and to constrain the population of dynamically assembled IMBHs.

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Section: Introductionmentioning

confidence: 99%

Binary Black Hole Mergers and Intermediate-mass Black Holes in Dense Star Clusters with Collisional Runaways

Purohit,

Fragione,

Rasio

et al. 2024

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Exploring the nature of ultra-luminous X-ray sources across stellar population ages using detailed binary evolution calculations

Misra,

Kovlakas,

Fragos

et al. 2024

A&A

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Ultra-luminous X-ray sources (ULXs) are sources observed to have extreme X-ray luminosities exceeding the Eddington limit of a stellar-mass black hole (BH). A fraction of ULXs show X-ray pulsations, which are evidence for accreting neutron stars (NSs). Theoretical studies have suggested that NSs, rather than BHs, dominate the compact objects of intrinsic ULX populations, even though the majority of the observed sample is non-pulsating, implying that X-ray pulses from many NS ULXs are unobservable. We simulate populations of X-ray binaries covering a range of starburst ages spanning from 5 to 1000\,Myr with the aim of comparing the properties of observed ULXs at the different ages. Additionally, we compare two models describing different assumptions for the physical processes governing binary evolution. We used the new population synthesis code POSYDON to generate multiple populations of ULXs spanning multiple burst ages. We employed a model for geometrically beamed emission from a super-Eddington accretion disk in order to estimate the luminosities of ULXs. Following theoretical predictions for the alignment of the spin axis of an NS with the accretion disk due to mass transfer, we estimated the required mass to be accreted by the NSs in the ULX populations so that the alignment suppresses observable X-ray pulses. While we find that the properties of ULX populations are sensitive to model assumptions, there are certain trends that the populations follow. Generally, young and old stellar populations are dominated by BH and NS accretors, respectively. The donor stars go from being massive H-rich main-sequence stars in young populations ($<100\ Myr$) to low-mass post-main sequence H-rich stars in older populations ($>100\ Myr$), with stripped He-rich giant donors dominating the populations at around 100\,Myr. In addition, we find that NS ULXs exhibit stronger geometrical beaming than BH ULXs, leading to an underrepresentation of NS accretors in observed populations. Coupled with our finding that X-ray pulses are suppressed in at least 60<!PCT!> of the NS ULXs, we suggest that the observed fraction of ULXs with detectable X-ray pulses is very small, in agreement with observations. We show that geometrical beaming and the mass-accretion phase are critical aspects of understanding ULX observations. Our results suggest that even though most ULXs have accreting NSs, those with observable X-ray pulses would be very few.

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Ultraluminous X-ray sources with He star companions

Li,

Wang,

Liu

et al. 2024

Monthly Notices of the Royal Astronomical Society

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Ultraluminous X-ray sources (ULXs) are non-nuclear point-like objects observed with extremely high X-ray luminosity that exceeds the Eddington limit of a $\rm 10\, M_\odot$ black hole. A fraction of ULXs has been confirmed to contain neutron star (NS) accretors due to the discovery of their X-ray pulsations. The donors detected in NS ULXs are usually luminous massive stars because of the observational biases. Recently, the He donor star in NGC 247 ULX-1 has been identified, which is the first evidence of a He donor star in ULXs. In this paper, we employed the stellar evolution code MESA to investigate the formation of ULXs through the NS+He star channel, in which a He star transfers its He-rich material onto the surface of a NS via Roche-lobe overflow. We evolved a large number of NS+He star systems and provided the parameter space for the production of ULXs. We found that the initial NS+He star systems should have ∼0.7–2.6 M⊙ He star and ∼0.1–2500 d orbital period for producing ULXs, eventually evolving into intermediate-mass binary pulsars. According to binary population synthesis calculations, we estimated that the Galactic rate of NS ULXs with He donor stars is in the range of ∼1.6–4.0 × 10−4 yr−1, and that there exist ∼7 − 20 detectable NS ULXs with He donor stars in the Galaxy.

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The Nature of the IMBH Candidate CXO J133815.6+043255: High-frequency Radio Emission

Cited by 4 publications

References 59 publications

Binary Black Hole Mergers and Intermediate-mass Black Holes in Dense Star Clusters with Collisional Runaways

Binary Black Hole Mergers and Intermediate-mass Black Holes in Dense Star Clusters with Collisional Runaways

Exploring the nature of ultra-luminous X-ray sources across stellar population ages using detailed binary evolution calculations

Ultraluminous X-ray sources with He star companions

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