http://arxiv.org/abs/2303.16231
Roughly half of the quasi-periodic eruption (QPE) sources in galactic nuclei exhibit a remarkably regular alternating “long-short” pattern of recurrence times between consecutive flares. In support of previous suggestions, we show that a main-sequence star (brought into the nucleus as an extreme mass-ratio inspiral; EMRI) which passes twice per orbit through the accretion disk of the supermassive black hole (SMBH) on a mildly eccentric inclined orbit, each time shocking and ejecting optically-thick gas clouds above and below the midplane (akin to dual “supernovae”), naturally reproduces the luminosities, durations, and spectral temperatures of observed QPE flares. Similar to supernova shock break-out from a compact star, inefficient photon production in the collision debris renders the QPE emission much harder than the blackbody temperature, enabling the Comptonized spectrum to stick out from the softer quiescent disk spectrum. Destruction of the star via mass ablation typically limits the lifetime of QPE emission to decades, precluding a long-lived AGN as the source of the gaseous disk. By contrast, a tidal disruption event (TDE) naturally provides a transient gaseous disk on the requisite radial scale, with a rate sufficiently high relative to the EMRI inward migration rate, that a significant fraction of TDEs should host a QPE. This picture is consistent with the X-ray TDE observed several years prior to the QPE emission from GSN 069. Remarkably, a second TDE-like flare was observed from this event, starting immediately after detectable QPE activity ceased; this accretion event could plausibly result from the (partial or complete) destruction of the QPE-generating star triggered by runaway mass-loss. Our model can also be applied to black hole-disk collisions, such as those proposed to generate quasi-periodic flares in the candidate SMBH binary OJ 287.
I. Linial and B. Metzger
Thu, 30 Mar 23
57/66
Comments: 21 pages, 4 figures, 2 tables
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