Browsing by Author "Miller, Jon M."

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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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    Ultraluminous X-ray bursts in two ultracompact companions to nearby elliptical galaxies
    (Nature Portfolio, 2016-10-20) Irwin, Jimmy A.; Maksym, W. Peter; Sivakoff, Gregory R.; Romanowsky, Aaron J.; Lin, Dacheng; Speegle, Tyler; Prado, Ian; Mildebrath, David; Strader, Jay; Liu, Jifeng; Miller, Jon M.; University of Alabama Tuscaloosa; Harvard University; Smithsonian Astrophysical Observatory; Smithsonian Institution; University of Alberta; California State University System; San Jose State University; University of California System; University of California Santa Cruz; University System Of New Hampshire; University of New Hampshire; Michigan State University; Chinese Academy of Sciences; National Astronomical Observatory, CAS; University of Chinese Academy of Sciences, CAS; University of Michigan System; University of Michigan
    A flaring X-ray source was found near the galaxy NGC 4697 (ref. 1). Two brief flares were seen, separated by four years. During each flare, the flux increased by a factor of 90 on a timescale of about one minute. There is no associated optical source at the position of the flares(1), but if the source was at the distance of NGC 4697, then the luminosities of the flares were greater than 10(39) erg per second. Here we report the results of a search of archival X-ray data for 70 nearby galaxies looking for similar flares. We found two ultraluminous flaring sources in globular clusters or ultracompact dwarf companions of parent elliptical galaxies. One source flared once to a peak luminosity of 9 x 10(40) erg per second; the other flared five times to 10(40) erg per second. The rise times of all of the flares were less than one minute, and the flares then decayed over about an hour. When not flaring, the sources appear to be normal accreting neutron-star or black-hole X-ray binaries, but they are located in old stellar populations, unlike the magnetars, anomalous X-ray pulsars or soft gamma repeaters that have repetitive flares of similar luminosities.