On the Tidal Capture of White Dwarfs by Intermediate-mass Black Holes in Dense Stellar Environments

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 $\sim 10^5{M}_{\odot }$, 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 a typical rate of $\sim 1{\mathrm{Myr}}^{-1}$ for galactic nuclei and $\sim 0.01{\mathrm{Myr}}^{-1}$ for globular clusters. Following the capture, the WD inspirals onto the IMBH producing gravitational waves detectable out to $\sim 100$ Mpc by LISA for $\sim 10^4{M}_{\odot }$ IMBHs. The subsequent tidal stripping/disruption of the WD can also release bright X-ray and gamma-ray emission with luminosities of at least $\gtrsim 10^{40}\mathrm{erg}{\mathrm{s}}^{-1}$, detectable by \textit{Chandra}, \textit{Swift}, and upcoming telescopes, such as the \textit{Einstein Probe}.

13 pages, 8 figures. Published at ApJ

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Cited by in corpus (4)

• Science objectives of the Einstein Probe mission
• Observing white dwarf tidal stripping with TianQin gravitational wave observatory
• Can GRB 250702B be explained as the tidal disruption of a white dwarf by an intermediate mass black hole? Yes
• Asymmetrical thermonuclear supernovae triggered by the tidal disruption of white dwarfs