2025/02/24 by Yuhan Yao, Yao, Yuhan, Ryan Chornock +65 · 2 voices · 7 citations
#astro-ph.GA #astro-ph.HE
paper · pdf · doi:10.48550/arxiv.2502.17661
Tidal disruption events (TDEs) that are spatially offset from the nuclei of their host galaxies offer a new probe of massive black hole (MBH) wanderers, binaries, triples, and recoiling MBHs. Here we present AT2024tvd, the first off-nuclear TDE identified through optical sky surveys. High-resolution imaging with the Hubble Space Telescope shows that AT2024tvd is 0.914± 0.010′′ offset from the apparent center of its host galaxy, corresponding to a projected distance of 0.808± 0.009 kpc at z=0.045. Chandra and VLA observations support the same conclusion for the TDE's X-ray and radio emission. AT2024tvd exhibits typical properties of nuclear TDEs, including a persistent hot UV/optical component that peaks at L\rm bb∼ 6× 1043 \rm erg s-1, broad hydrogen lines in its optical spectra, and delayed brightening of luminous (L\rm X,peak∼ 3× 1043 \rm erg s-1), highly variable soft X-ray emission. The MBH mass of AT2024tvd is 106±1 M_\odot, at least 10 times lower than its host galaxy's central black hole mass (\gtrsim 108 M_\odot). The MBH in AT2024tvd has two possible origins: a wandering MBH from the lower-mass galaxy in a minor merger during the dynamical friction phase or a recoiling MBH ejected by triple interactions. Combining AT2024tvd with two previously known off-nuclear TDEs discovered in X-rays (3XMM J2150 and EP240222a), which likely involve intermediate-mass black holes in satellite galaxies, we find that the parent galaxies of all three events are very massive (∼ 1010.9 M_\odot). This result aligns with expectations from cosmological simulations that the number of offset MBHs scales linearly with the host halo mass.