Browsing by Author "Guillochon, James"

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    Flows of X-ray gas reveal the disruption of a star by a massive black hole
    (Nature Portfolio, 2018-04-02) Miller, Jon M.; Kaastra, Jelle S.; Miller, M. Coleman; Reynolds, Mark T.; Brown, Gregory; Cenko, S. Bradley; Drake, Jeremy J.; Gezari, Suvi; Guillochon, James; Gultekin, Kayhan; Irwin, Jimmy; Levan, Andrew; Maitra, Dipankar; Maksym, W. Peter; Mushotzky, Richard; O'Brien, Paul; Paerels, Frits; de Plaa, Jelle; Ramirez-Ruiz, Enrico; Strohmayer, Tod; Tanvir, Nial; University of Michigan System; University of Michigan; Utrecht University; Leiden University; Leiden University - Excl LUMC; University System of Maryland; University of Maryland College Park; University of Warwick; National Aeronautics & Space Administration (NASA); NASA Goddard Space Flight Center; Harvard University; Smithsonian Astrophysical Observatory; Smithsonian Institution; University of Alabama Tuscaloosa; University of Leicester; Columbia University; University of California System; University of California Santa Cruz
    Tidal forces close to massive black holes can violently disrupt stars that make a close approach. These extreme events are discovered via bright X-ray(1-4) and optical/ultraviolet(5,6) flares in galactic centres. Prior studies based on modelling decaying flux trends have been able to estimate broad properties, such as the mass accretion rate(6,7). Here we report the detection of flows of hot, ionized gas in high-resolution X-ray spectra of a nearby tidal disruption event, ASASSN-14li in the galaxy PGC043234. Variability within the absorption-dominated spectra indicates that the gas is relatively close to the black hole. Narrow linewidths indicate that the gas does not stretch over a large range of radii, giving a low volume filling factor. Modest outflow speeds of a few hundred kilometres per second are observed; these are below the escape speed from the radius set by variability. The gas flow is consistent with a rotating wind from the inner, super-Eddington region of a nascent accretion disk, or with a filament of disrupted stellar gas near to the apocentre of an elliptical orbit. Flows of this sort are predicted by fundamental analytical theory(8) and more recent numerical simulations(7,9-14).
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    A likely decade-long sustained tidal disruption event
    (Nature Portfolio, 2017-02-02) Lin, Dacheng; Guillochon, James; Komossa, S.; Ramirez-Ruiz, Enrico; Irwin, Jimmy A.; Maksym, W. Peter; Grupe, Dirk; Godet, Olivier; Webb, Natalie A.; Barret, Didier; Zauderer, B. Ashley; Duc, Pierre-Alain; Carrasco, Eleazar R.; Gwyn, Stephen D. J.; University System Of New Hampshire; University of New Hampshire; Harvard University; Smithsonian Astrophysical Observatory; Smithsonian Institution; University of California System; University of California Santa Cruz; University of Alabama Tuscaloosa; Seoul National University (SNU); Morehead State University; Centre National de la Recherche Scientifique (CNRS); Universite de Toulouse; Universite Toulouse III - Paul Sabatier; New York University; CEA; UDICE-French Research Universities; Universite Paris Cite; Universite Paris Saclay; National Research Council Canada
    Multiwavelength flares from tidal disruption and accretion of stars can be used to find and study otherwise dormant massive black holes in galactic nuclei(1). Previous well-monitored candidate flares were short-lived, with most emission confined to within similar to 1 year(2-5). 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 similar to 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 holes(6). 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 (similar to 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.