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Abstract Intermediate-mass black holes (IMBHs) are the missing link between stellar-mass and supermassive black holes, widely believed to reside in at least some dense star clusters, but not yet observed directly. Tidal disruptions of white dwarfs (WDs) are luminous only for black holes less massive than ∼105M⊙, therefore providing a unique smoking gun that could finally prove the existence of IMBHs beyond any reasonable doubt. Here, we investigate the tidal captures of WDs by IMBHs in dense star clusters, and estimate upper limits to the capture rates of ∼1 Myr−1for galactic nuclei and ∼0.01 Myr−1for globular clusters. Following the capture, the WD inspirals onto the IMBH, producing gravitational waves detectable out to ∼100 Mpc by LISA for ∼104M⊙IMBHs. The subsequent tidal stripping/disruption of the WD can also release bright X-ray and gamma-ray emission with luminosities of at least ≳1040erg s−1, detectable by Chandra, Swift, and upcoming telescopes, such as the Einstein Probe.
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Inferring the Intermediate-mass Black Hole Number Density from Gravitational-wave Lensing Statistics
Abstract The population properties of intermediate-mass black holes remain largely unknown, and understanding their distribution could provide a missing link in the formation of supermassive black holes and galaxies. Gravitational-wave observations can help fill in the gap from stellar mass black holes to supermassive black holes with masses between ∼100–104M⊙. In our work, we propose a new method for examining lens populations through lensing statistics of gravitational waves, here focusing on inferring the number density of intermediate-mass black holes through hierarchical Bayesian inference. Simulating ∼200 lensed gravitational-wave signals, we find that existing gravitational-wave observatories at their design sensitivity could either constrain the number density of 106Mpc−3within a factor of 10, or place an upper bound of ≲104Mpc−3if the true number density is 103Mpc−3. More broadly, our method leaves room for incorporation of additional lens populations, providing a general framework for probing the population properties of lenses in the universe.
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- Award ID(s):
- 1836814
- PAR ID:
- 10484897
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal Letters
- Volume:
- 932
- Issue:
- 1
- ISSN:
- 2041-8205
- Format(s):
- Medium: X Size: Article No. L4
- Size(s):
- Article No. L4
- Sponsoring Org:
- National Science Foundation
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