New physical insights about Tidal Disruption Events from a comprehensive observational inventory at X-ray wavelengths

TL;DR

This study provides new insights into X-ray Tidal Disruption Events (TDEs) by analyzing 70 cases over three decades, revealing their luminosity evolution, spectral properties, and the distinction between jetted and non-jetted events, suggesting different origins and reprocessing mechanisms.

Contribution

It offers a comprehensive observational analysis of X-ray TDEs, highlighting their luminosity decay, spectral characteristics, and the bimodal distribution of their luminosities, advancing understanding of their physical nature.

Findings

X-ray TDEs increase in brightness by 2-4 orders of magnitude during flares.

Decay rates are shallower than the canonical t^{-5/3} law, indicating viscous delays.

Jetted and non-jetted TDEs show distinct X-ray to optical ratios, implying different reprocessing processes.

Abstract

We perform a comprehensive study of the X-ray emission from 70 transient sources which have been classified as a tidal disruption event (TDE) in the literature. We explore the properties of these candidates using nearly three decades of X-ray observations to quantify the properties and characteristics of X-ray TDEs observationally. We find that the emission from X-ray TDEs increase by two to four orders of magnitude compared to pre-flare constraints, which evolves significantly with time and decays with powerlaw indices that are typically shallower than the canonical $t^{-5/3}$ decay law, implying that X-ray TDEs are viscously delayed. These events exhibit enhanced column densities relative to Galactic and are quite soft in nature, with no strong correlation between the amount of detected soft and hard emission. At peak, jetted events have an X-ray to optical ratio $\gg$1, while non-jetted events have a ratio $\sim$1, which suggests that these events undergo reprocessing at different rates. X-ray TDEs have long $T_{90}$ values consistent with that expected from a viscously-driven accretion disk formed by the disruption of a main-sequence star by a black hole with a mass $<$$10^{7}M_{\odot}$. The isotropic luminosities of X-ray TDEs is bimodal such that jetted and non-jetted events are separated by a "reprocessing valley" which we suggest is naturally populated by optical/UV TDEs that most likely produce X-rays, but due to reprocessing this emission is "veiled" from observations. Our results suggest that non-jetted X-ray TDEs likely originate from partial disruptions and/or disruptions of low mass stars.