Tidal Disruption Encores
The Astrophysical Journal Letters(2024)
摘要
Nuclear star clusters (NSCs), made up of a dense concentrations 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 (sBH) lead to tidal
disruption events (TDEs). We uncover an interesting new phenomenon: For a
subset of these, the unbound debris (to the sBH) remain bound to the SMBH,
accreting at a later time, and thus giving rise to a second flare. We compute
the rate of such events, and find them ranging within 10^-6
-10^-3 yr^-1gal^-1 for SMBH mass ≃ 10^6-10^9M_⊙.
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 standard t^-5/3 power-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 (EMRI)
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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关键词
Time domain astronomy,Stellar mass black holes,Supermassive black holes,Tidal disruption
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