Evolution of quasi-periodic eruptions in the post-tidal disruption event accretion disk perturbed by an orbiting star
Аннотация
Context. Quasi-periodic eruptions (QPEs) are a recently discovered class of highly variable X-ray bursts originating in galactic nuclei. These high-amplitude bursts exhibit a periodicity ranging from tens of minutes to several days and they are also characterized by variable peak amplitudes that can vary by a factor of few. While multiple physical models have been proposed to explain QPE light curves, none of them can fully account for all the observed features. A possible connection between QPEs and tidal disruption events (TDEs) has been suggested, particularly due to past optical/UV outbursts that can be traced back for several sources, the long-term decay in the continuum luminosity, and the soft, thermal-dominated X-ray spectrum. Aims. Our primary goal is to verify whether the long-term decrease in eruption amplitudes detected for some QPE sources is consistent with a scenario where the accretion disk had been formed following a TDE. Methods. In this work, we adopted a simplified extreme mass ratio inspiral (EMRI) scenario, where a solar-type star orbits a supermassive black hole (SMBH) and collides with an accretion disk twice per orbit, generating eruptions. We assumed a post-TDE disk that follows a temporal power-law decline in mass accretion (∝ t − p , p > 0). As our aim is to develop a toy-model scenario, we used purely analytical methods, without considering all intervening processes in their full scope. Results. Our results indicate that (i) the observed long-term decline in QPE amplitudes can be reproduced if the first monitored epoch occurs years to a few decades after the tidal disruption; and (ii) stellar mass loss caused by ablation can play an important role in the evolution of QPE amplitudes in systems with heavy main sequence stars.