Possible power source of Seyfert galaxies and QSOs

Hills, J. G.

doi:10.1038/254295a0

Cited by 694 publications

(552 citation statements)

References 8 publications

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“…In such a case the star will be swallowed whole by the black hole, without a tidal disruption event (Hills 1975). After a star is tidally disrupted, there are two distinct stages in the dynamical evolution of the debris, each with its own time development and luminosity:…”

Section: Tidal Disruption Of a Star By A Supermassive Black Holementioning

confidence: 99%

“…Early seminal investigations by Hills (1975), Lacy, Townes, & Hollenbach (1982), Rees (1988), Evans & Kochanek (1989), and Cannizzo, Lee, & Goodman (1990) were followed up with detailed analytical studies (Kochanek 1994;Khokhlov & Melia 1996;Loeb & Ulmer 1997;Ulmer, Paczyń ski, & Goodman 1998;Ulmer 1999) and numerical simulations (Khokhlov, Novikov, & Pethick 1993;Frolov et al 1994;Marck, Lioure, & Bonazzola 1996;Diener et al 1997;Kim, Park, & Lee 1999;Ayal, Livio, & Piran 2000;Ivanov & Novikov 2001).…”

Section: Introductionmentioning

confidence: 99%

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The Giant X‐Ray Flare of NGC 5905: Tidal Disruption of a Star, a Brown Dwarf, or a Planet?

Li¹,

Narayan²,

Menou³

2002

ApJ

124

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We model the 1990 giant X-ray flare of the quiescent galaxy NGC 5905 as the tidal disruption of a star by a supermassive black hole. From the observed rapid decline of the luminosity, over a timescale of a few years, we argue that the flare was powered by the fallback of debris rather than subsequent accretion via a thin disk. The fallback model allows constraints to be set on the black hole mass and the mass of debris. The latter must be very much less than a solar mass to explain the very low luminosity of the flare. The observations can be explained either as the partial stripping of the outer layers of a low-mass main-sequence star or as the disruption of a brown dwarf or a giant planet. We find that the X-ray emission in the flare must have originated within a small patch rather than over the entire torus of circularized material surrounding the black hole. We suggest that the patch corresponds to the '' bright spot '' where the stream of returning debris impacts the torus. Interestingly, although the peak luminosity of the flare was highly sub-Eddington, the peak flux from the bright spot was close to the Eddington limit. We speculate on the implications of this result for observations of other flare events.

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Section: Tidal Disruption Of a Star By A Supermassive Black Holementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Giant X‐Ray Flare of NGC 5905: Tidal Disruption of a Star, a Brown Dwarf, or a Planet?

Li¹,

Narayan²,

Menou³

2002

ApJ

124

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show abstract

“…The physics of accretion has been developed mainly for stellar binary X-ray sources, and even there cannot be considered solved. In AGN there are further complications, such as the disputed origin of the accreting matter (compare the suggestions of Hills 1975;Shields and Wheeler 1978;Gunn 1979;Bailey 1982;Dahari 1984). Even so the candidate parameters of the theoretical space are already clear: 3K h , the mass of the black hole, m, the current accretion rate (not necessarily the same as the average rate of fuel supply), stage in evolutionary history, viewing angle, environment (e.g., host galaxy type), angular momentum (of the hole or the fuel), and degree of obscuration.…”

Section: Orthodox Classification Of Active Galactic Nucleimentioning

confidence: 99%

Classification of active galaxies and the prospect of a unified phenomenology

Lawrence

1987

PASP

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The observational classification of active galaxies is reviewed and its likely meaning discussed. A large number of facts and ideas are examined, but a particular set of ideas is stressed as our best hope for a unified phenomenology, as follows. There is only one kind of Active Galactic Nucleus (AGN). The observed variety arises from three degrees of freedom: (1) Dust opacity, which produces the distinction between Type 1 and Type 2 AGN. (2) Viewing angle of a relativistic jet, which produces the distinction between blazars and Type 1 AGN. (3) Duty cycle of activity (i.e., fraction of time spent "on") which produces the distinction between radio-loud and radio-quiet AGN. The duty cycle may be related to the mass of the spheroidal component of the parent galaxy. A fourth degree of freedom is, of course, the overall luminosity. Also, it has recently become clear that there is considerable latitude in the physical condition of gas surrounding the nucleus.For theories of AGN to be presented with a real challenge, we need two things. First, a clear qualitative phenomenology, such as the possibility outlined above, must be decided upon. Second, we need to formulate a quantitative phenomenology.

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“…Once these exceed the self-gravity of the star, the star is disrupted (Hills 1975). The distance at which this happens, the tidal radius, is given by r t 7 10 12 M BH 10 6 M 1 3…”

Section: Introductionmentioning

confidence: 99%

Tidal disruption of stars by supermassive black holes: The X-ray view

Komossa

2012

EPJ Web of Conferences

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Abstract. The tidal disruption of stars by supermassive black holes produces luminous soft X-ray accretion flares in otherwise inactive galaxies. First events have been discovered in X-rays with the ROSAT observatory, and have more recently been detected with XMM-Newton, Chandra and Swift, and at other wavelengths. In X-rays, they typically appear as very soft, exceptionally luminous outbursts of radiation, which decline consistent with L ∝ t −5/3 on the timescale of months to years. They reach total amplitudes of decline up to factors 1000-6000 more than a decade after their initial high-states, and in low-state, their host galaxies are essentially X-ray inactive, optically inactive, and radio inactive. X-ray luminous tidal disruption events (TDEs) represent a powerful new probe of accretion physics near the event horizon, and of relativistic effects. TDEs offer a new way of estimating black hole spin, and they are signposts of supermassive binary black holes and recoiling black holes. Once discovered in the thousands in upcoming sky surveys, their rates will probe stellar dynamics in distant galaxies, and they will uncover theso far elusive -population of intermediate mass black holes in the universe, if they do exist. Further, the reprocessing of the flare into IR, optical and UV emission lines provides us with multiple new diagnostics of the properties of any gaseous material in the vicinity of the black hole (including the disrupted star itself) and in the host galaxy. First candidate events of this kind have been reported recently.

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Possible power source of Seyfert galaxies and QSOs

Cited by 694 publications

References 8 publications

The Giant X‐Ray Flare of NGC 5905: Tidal Disruption of a Star, a Brown Dwarf, or a Planet?

The Giant X‐Ray Flare of NGC 5905: Tidal Disruption of a Star, a Brown Dwarf, or a Planet?

Classification of active galaxies and the prospect of a unified phenomenology

Tidal disruption of stars by supermassive black holes: The X-ray view

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