The Wandering Supermassive Black Hole Powering the off-nuclear TDE AT2024tvd

Abstract

We present an analysis of the spectral energy distribution (SED) of the off-nuclear tidal disruption event (TDE) AT2024tvd during its late-time plateau phase, combining X-ray spectra and UV/optical photometry. Using a fully relativistic, compact accretion disk model with self-consistent inner-disk Comptonization, we reproduce the observed SED without significant residuals. The inferred black hole mass $\log 10(M\bullet /M_{\odot })\approx 6.0\pm 0.2$, and the inferred disk parameters place AT2024tvd within known TDE-disk scaling relations ($L_{\mathrm{bol}}^{\mathrm{disk}}/L_{\mathrm{Edd}}\propto T_{\mathrm{p}}^4\propto M_{\bullet }^{-1}$, $L_{\mathrm{plat}}\propto M_{\bullet }^{2/3}$, $R_{\mathrm{out}}/r_{\mathrm{g}}\propto M_{\bullet }^{-2/3}$). Our results show that: (i) there is no \textit{detected} star cluster or dwarf galaxy associated with the source, down to a mass limit of ${\log }_{10}(M_{\mathrm{gal}}/M_{\odot })\le 7.6$; (ii) the black hole is a wandering supermassive, rather than intermediate-mass, black hole; and (iii) the source represents an extreme case of black hole-to-host mass ratio, with $M_{\bullet }/M_{\mathrm{gal}}>3\%$, consistent with a heavily tidally stripped nucleus. The latter aligns with cosmological simulations predicting that surviving host remnants of most wandering black holes should not retain a detectable stellar overdensity when located at small halo-centric distances. We discuss differences with previous analyses of this source and highlight why our modeling approach provides a more physically consistent solution with more reliable parameter inference.

Submitted to ApJ Letters