15 research outputs found

    The Peak of the Fallback Rate from Tidal Disruption Events: Dependence on Stellar Type

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    A star completely destroyed in a tidal disruption event (TDE) ignites a luminous flare that is powered by the fallback of tidally stripped debris to a supermassive black hole (SMBH) of mass M•. We analyze two estimates for the peak fallback rate in a TDE, one being the “frozen-in” model, which predicts a strong dependence of the time to peak fallback rate, tpeak, on both stellar mass and age, with 15 days ≲ tpeak ≲ 10 yr for main sequence stars with masses 0.2 ≤ M⋆/M⊙ ≤ 5 and M• = 106M⊙. The second estimate, which postulates that the star is completely destroyed when tides dominate the maximum stellar self-gravity, predicts that tpeak is very weakly dependent on stellar type, with t MM peak • = (23.2 +4.0 days) (M./10 6M⊙) 1/2 for 0.2 ≤ M⋆/M⊙ ≤ 5, while tpeak = (29.8 +3.6 days) (M./10 6M⊙) 1/2 for a Kroupa initial mass function truncated at 1.5M⊙. This second estimate also agrees closely with hydrodynamical simulations, while the frozen-in model is discrepant by orders of magnitude. We conclude that (1) the time to peak luminosity in complete TDEs is almost exclusively determined by SMBH mass, and (2) massive-star TDEs power the largest accretion luminosities. Consequently, (a) decades-long extra-galactic outbursts cannot be powered by complete TDEs, including massive-star disruptions, and (b) the most highly super-Eddington TDEs are powered by the complete disruption of massive stars, which—if responsible for producing jetted TDEs—would explain the rarity of jetted TDEs and their preference for young and star-forming host galaxies

    Neural Mechanisms for Representing Surface and Contour Features

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    Contours and surfaces are basic qualities which are processed by the visual system to aid the successful behavior of autonomous beings within the environment. There is increasing evidence that the two modalities of contours and surfaces are processed in separate, but interacting visual streams or sub-systems. Neurons at early stages in the visual system show strong responses only at locations of high contrast, such as edges, but only weak responses within homogeneous regions. Thus, for the processing and representation of surfaces, the visual system has to integrate sparse local measurements into a dense, coherent representation

    ATLAS: technical proposal for a general-purpose p p experiment at the large hadron collider at CERN

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