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TDE 2025abcr: A Tidal Disruption Event in the Outskirts of a Massive Galaxy

Stein, Robert et al., 2026, The Astrophysical Journal Letters, 1006, L57 | View on ADS (2026ApJ..1006L..57S)

Abstract

Tidal disruption events (TDEs) have traditionally been discovered in optical sky surveys through targeted searches of nuclear transients. However, it is expected that some TDEs will occur outside the galaxy nucleus, arising from wandering black holes (BHs) originating in galaxy mergers. Here, we present observations of TDE 2025abcr, the first optical TDE discovered in the outskirts of a host galaxy. The TDE was identified by a custom "off-nuclear" implementation of the machine learning classifier tdescore, which classifies new ZTF transients based on their lightcurves. Follow-up observations confirm that TDE 2025abcr is a TDE-H+He, occurring 9 .″ 5 (9.3 kpc projected distance) from the nucleus of a massive galaxy (M⋆ = 1011.18±0.03M⊙) with a central BH mass of 108.82±0.65M⊙. TDE 2025abcr itself was likely disrupted by a much lighter BH (106.09±0.53M⊙, as estimated with peak luminosity scaling relations). The BH was either dynamically ejected from the nucleus or lies at the center of a very faint tidally stripped dwarf galaxy undergoing a minor merger. Late-time observations of TDE 2025abcr could confirm the origin of this apparent "wandering" BH. The rate of highly offset (≳3 kpc) TDEs can be constrained to <10% of the nuclear TDE rate, but our discovery implies that many dozens of similar sources will be detected by the Vera C. Rubin Observatory each year with resolvable offsets.

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