Revisit the rate of tidal disruption events: the role of the partial tidal disruption event

TL;DR

This study uses high-accuracy simulations to compare full and partial tidal disruption events in galactic centers, revealing significant differences in event rates, leftover star properties, and accretion rates, which improve understanding of SMBH environments.

Contribution

The paper introduces novel effects in simulations of PTDEs, showing their impact on event rates and properties, and provides refined estimates of TDE occurrence and accretion characteristics.

Findings

PTDE rate is about 75% higher than previous estimates.

Switching on new effects reduces FTDEs by 28%.

58% of PTDEs exceed the Eddington accretion rate.

Abstract

Tidal disruption of stars in dense nuclear star clusters containing supermassive central black holes (SMBH) is modeled by high-accuracy direct N-body simulation. Stars getting too close to the SMBH are tidally disrupted and a tidal disruption event (TDE) happens. TDEs probe properties of SMBH, their accretion disks, and the surrounding nuclear stellar cluster. In this paper we compare rates of full tidal disruption events (FTDE) with partial tidal disruption events (PTDE). Since a PTDE does not destroy the star, a leftover object emerges; we use the term 'leftover star' for it; two novel effects occur in the simulation: (1) variation of the leftover star's mass and radius, (2) variation of the leftover star's orbital energy. After switching on these two effects in our simulation, the number of FTDEs is reduced by roughly 28%, and the reduction is mostly due to the ejection of the leftover stars from PTDEs coming originally from relatively large distance. The number of PTDEs is about 75% higher than the simple estimation given by Stone et al. (2020), and the enhancement is mainly due to the multiple PTDEs produced by the leftover stars residing in the diffusive regime. We compute the peak mass fallback rate for the PTDEs and FTDEs recorded in the simulation, and find 58% of the PTDEs have peak mass fallback rate exceeding the Eddington limit, and the number of super-Eddington PTDEs is 2.3 times the number of super-Eddington FTDEs.