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Abstract Nuclear star clusters (NSCs), made up of a dense concentration of stars and the compact objects they leave behind, are ubiquitous in the central regions of galaxies surrounding the central supermassive black hole (SMBH). Close interactions between stars and stellar-mass black holes (sBHs) lead to tidal disruption events (TDEs). We uncover an interesting new phenomenon: for a subset of these, the unbound debris (to the sBH) remains bound to the SMBH, accreting at a later time, thus giving rise to a second flare. We compute the rate of such events and find them ranging within 10−6–10−3yr−1gal−1for SMBH mass ≃106–109M⊙. Time delays between the two flares spread over a wide range, from less than a year to hundreds of years. The temporal evolution of the light curves of the second flare can vary between the standardt−5/3power law to much steeper decays, providing a natural explanation for observed light curves in tension with the classical TDE model. Our predictions have implications for learning about NSC properties and calibrating its sBH population. Some double flares may be electromagnetic counterparts to LISA extreme-mass-ratio inspiral sources. Another important implication is the possible existence of TDE-like events in very massive SMBHs, where TDEs are not expected. Such flares can affect spin measurements relying on TDEs in the upper SMBH range.
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Follow the Mass—A Concordance Picture of Tidal Disruption Events
Abstract Three recent global simulations of tidal disruption events (TDEs) have produced, using different numerical techniques and parameters, very similar pictures of their dynamics. In typical TDEs, after the star is disrupted by a supermassive black hole, the bound portion of the stellar debris follows highly eccentric trajectories, reaching apocenters of several thousand gravitational radii. Only a very small fraction is captured upon returning to the vicinity of the supermassive black hole. Nearly all of the debris returns to the apocenter, where shocks produce a thick irregular cloud on this radial scale and power the optical/UV flare. These simulation results imply that over a few years, the thick cloud settles into an accretion flow responsible for the long-term emission. Despite not being designed to match observations, and without any free parameters, the dynamical picture given by the three simulations aligns well with observations of typical events, correctly predicting the flares’ typical total radiated energy, luminosity, temperature, and emission-line width. On the basis of these predictions, we provide an updated method (TDEmass) to infer the stellar and black hole masses from a flare’s peak luminosity and temperature. This picture also correctly predicts that the luminosity observed years after the flare should be nearly constant. In addition, we show that in a magnitude-limited survey, if the intrinsic rate of TDEs is independent of black hole mass, the detected events will preferentially have black hole masses ∼106.3±0.3M⊙and stellar masses ∼1M⊙.
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- PAR ID:
- 10628794
- Publisher / Repository:
- Institute of Physics
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 988
- Issue:
- 2
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 220
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.3847/1538-4357/ade797
