A likely decade-long sustained tidal disruption event

Dacheng Lin , James Guillochon , S. Komossa , Enrico Ramirez-Ruiz , Jimmy A. Irwin , W. Peter Maksym , Dirk Grupe , Olivier Godet (1) , Natalie A. Webb (1) , Didier Barret (1) , B. Ashley Zauderer , Pierre-Alain Duc (2) , Eleazar R. Carrasco , Stephen D. J. Gwyn

1 IRAP - Institut de recherche en astrophysique et planétologie
2 AIM (UMR7158 / UMR_E_9005 / UM_112) - Astrophysique Interprétation Modélisation

Multiwavelength flares from tidal disruption and accretion of stars can be used to find and study otherwise dormant massive black holes in galactic nuclei. Previous well-monitored candidate flares are short-lived, with most emission confined to within ~1 year. Here we report the discovery of a well observed super-long (>11 years) luminous soft 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 generally 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 holes. 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 of an unusually long super-Eddington accretion phase that has never been observed before.

Domaines: Astrophysique [astro-ph]

Dacheng Lin, James Guillochon, S. Komossa, Enrico Ramirez-Ruiz, Jimmy A. Irwin, et al.. A likely decade-long sustained tidal disruption event. Nature Astron., 2017, 1, pp.0033. ⟨10.1038/s41550-016-0033⟩. ⟨hal-01554452⟩