Compact Accretion Disks in the Aftermath of Tidal Disruption Events: Parameter Inference from Joint X-ray Spectra and UV/Optical Photometry Fitting

TL;DR

The paper addresses constraining black hole masses in tidal disruption events by jointly modeling the late-time UV/optical plateau and soft X-ray spectra with a compact, fully relativistic accretion disk. Using up to three epochs per source and a Bayesian inference framework, the authors fit 14 TDEs, including an off-nuclear IMBH candidate, to recover $M_{\bullet}$ and disk properties in a physically consistent way. They show that the disk emission follows standard accretion-scaling relations, e.g., $L_{Bol}^{disk}/L_{Edd} \propto T_p^4 \propto M_{\bullet}^{-1}$, $L_{plat} \propto M_{\bullet}^{2/3}$, and $R_{out}/r_g \propto M_{\bullet}^{-2/3}$, and that $M_{\bullet}$–host correlations are recovered with substantially higher precision, extending into the IMBH regime. The results support a common disk origin for optical and X-ray emission in TDEs, quantify the gains in parameter precision from multi-wavelength joint fitting, and discuss implications for TDE physics and black hole demographics.

Abstract

We present a multi-wavelength analysis of 14 tidal disruption events (TDEs)-including an off-nuclear event associated with an ultra-compact dwarf galaxy-selected for having available thermal X-ray spectra during their late-time UV/optical plateau phase. We show that at these stages, the full spectral energy distribution - X-ray spectra and UV/optical photometry - is well described by a compact, yet standard accretion disk, the same disk which powers the X-rays at all times. By fitting up to three epochs per source with a fully relativistic disk model, we show that many system properties can be reliably recovered, including importantly the black hole mass ($M_{\bullet}$). These accretion-based $M_{\bullet}$ values, which in this sample span nearly three orders of magnitude, are consistent with galactic scaling relations but are significantly more precise (68\% credible interval $ < \pm 0.3$ dex) and physically motivated. Expected accretion scaling relations (e.g., $L_{Bol}^{ disk} / L_{Edd} \propto T_p^4 \propto M_{\bullet}^{-1}$), TDE-specific physics correlations ($L_{plat} \propto M_{\bullet}^{2/3}$ and $R_{out}/r_g \propto M_{\bullet}^{-2/3}$) and black hole-host galaxy correlations ($M_{\bullet}$-$M_{gal}$ and $M_{\bullet}$-$σ_{\star}$) naturally emerge from the data and, for the first time, are self-consistently extended into the intermediate-mass (IMBH, $M_{\bullet} < 10^{5}$) regime. We discuss the implications of these results for TDE physics and modeling. We also review and discuss different methods for $M_{\bullet}$ inference in TDEs, and find that approaches based on physical models of the early-time UV/optical emission are not able to recover (at a statistically significant level) black hole-host galaxy scalings.

Figures (1)

• Figure 1: Examples of host-subtracted light curves of well observed TDEs, ASASSN-14li (left) and AT2019azh (right). The two phase UV/optical light curves (early-time flare vs. Plateau) is ubiquitous to TDEs independently of whether X-ray are prompt or delayed. Fluxes shown are not corrected for for any absorption or extinction.