A likely decade-long sustained tidal disruption event


Multiwavelength flares from tidal disruption and accretion of stars can be used to find and study otherwise dormant massive black holes in galactic nuclei1. Previous well-monitored candidate flares were short-lived, with most emission confined to within 1 year25. Here we report the discovery of a well-observed super-long (>11 years) luminous X-ray flare from the nuclear region of a dwarf starburst galaxy. After an apparently fast rise within 4 months a decade ago, the X-ray luminosity, though showing a weak trend of decay, has been persistently high at around the Eddington limit (when the radiation pressure balances the gravitational force). The X-ray spectra are soft — steeply declining towards higher energies — and can be described with Comptonized emission from an optically thick low-temperature corona, a super-Eddington accretion signature often observed in accreting stellar-mass black holes6. Dramatic spectral softening was also caught in one recent observation, implying either a temporary transition from the super-Eddington accretion state to the standard thermal state, or the presence of a transient highly blueshifted (0.36c) warm absorber. All these properties in concert suggest a tidal disruption event with an unusually long super-Eddington accretion phase that has never before been observed.

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Figure 1: The CFHT/MegaPrime r′-band image around the field of XJ1500+0154 indicates its galactic nuclear origin.
Figure 2: The long-term evolution of the X-ray luminosity and spectrum of XJ1500+0154.


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D.L. is supported by the National Aeronautics and Space Administration through Chandra Award Number GO5-16087X issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of the National Aeronautics Space Administration under contract NAS8-03060. We thank the Swift principal investigator N. Gehrels for approving our ToO request to make several observations of XJ1500+0154.

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D.L. wrote the main manuscript and led the data analysis. J.G. helped with the modelling of the long-term X-ray light curve and wrote the text on the modelling in the Supplementary Information. S.G. stacked the CFHT images. All authors discussed the results and commented on the manuscript.

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Correspondence to Dacheng Lin.

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Supplementary information

Supplementary Information

Supplementary Notes 1–13, Supplementary Tables 1–2, Supplementary Figures 1–8, Supplementary References. (PDF 646 kb)

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Lin, D., Guillochon, J., Komossa, S. et al. A likely decade-long sustained tidal disruption event. Nat Astron 1, 0033 (2017). https://doi.org/10.1038/s41550-016-0033

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