Exploració per tema "Forats negres (Astronomia)"

Ara es mostren els items 1-20 de 28

    • A close look into the variable stars surrounding the first X-ray Transient 

      Gómez Fernández, Laura (Universitat Politècnica de Catalunya, 2023-07-05)
      Treball Final de Grau
      Accés obert
      With the purpose of unveiling the optical counterpart of the first Black Hole Transient (BHT) ever detected, a 12 sq. degree area of the sky was surveyed with the 570-megapixel DECam camera around the estimated position ...

    • A shared accretion instability for black holes and neutron stars 

      Vincentelli, Federico; Neilsen, Joey; Tetarenko, Alexandra; Cavecchi, Yuri; Castro Segura, Noel; del Palacio, Santiago; van den Eijnden, Jakob; Vasilopoulos, Georgios; Altamirano, Diego; Armas Padilla, Montserrat; Bailyn, Charles; Belloni, Tomaso M.; Cúneo, Virginia; Degenaar, Nathalie (Macmillan Publishers, 2023-03-01)
      Article
      Accés obert
      Accretion disks around compact objects are expected to enter an unstable phase at high luminosity1. One instability may occur when the radiation pressure generated by accretion modifies the disk viscosity, resulting in the ...

    • A spectrally stratified hot accretion flow in the hard state of MAXI J1820+070 

      Dzielak, Marta A.; Marco, Barbara de; Zdziarski, Andrzej A. (Oxford University Press, 2021-09-01)
      Article
      Accés obert
      We study the structure of the accretion flow in the hard state of the black-hole X-ray binary MAXI J1820+070 with NICER data. The power spectra show broadband variability which can be fit with four Lorentzian components ...

    • Accretion geometry in the hard state of the black hole X-ray binary MAXI J1820+070 

      Zdziarski, Andrzej A.; Dzielak, Marta A.; Marco, Barbara de (2021-03-01)
      Article
      Accés obert
      We study X-ray spectra from the outburst rise of the accreting black hole binary MAXI J1820+070. We find that models having the disk inclinations within those of either the binary or the jet imply significant changes of ...

    • An approach to evaporating stars and black holes 

      Fayos Vallés, Francisco; Torres Herrera, Ramon (2011-09-01)
      Article
      Accés obert
      Many models in which the object under study loses all its mass have appeared in the literature. No doubt, the most eminent examples are the models for evaporating black holes and for evaporating stars. Here we describe ...

    • Cena con las estrellas 

      Barceló Garcia, Miquel (2008-09)
      Article
      Accés obert

    • Discovery of soft and hard X-ray time lags in low-mass AGNs 

      Mallick, L.; Wilkins, Daniel Richard; Alston, William; Markowitz, Alex; Marco, Barbara de; Parker, Michael L.; Lohfink, Anne M.; Stalin, Chelliah Subramonian (Oxford University Press, 2021-03-05)
      Article
      Accés obert
      The scaling relations between the black hole (BH) mass and soft lag properties for both active galactic nuclei (AGNs) and BH X-ray binaries (BHXRBs) suggest the same underlying physical mechanism at work in accreting BH ...

    • Hawking radiation in NS5 and little string theory 

      Lorente Espín, Oscar (Universitat Politècnica de Catalunya, 2012-09-20)
      Tesi
      Accés obert
      In this thesis we have focused on semi-classical methods that enables us to obtain non-thermal spectra for the vast majority of black holes. This fact is due to taking into account the backreaction of the metric, when the ...

    • Interiors of singularity-free rotating black holes 

      Torres Herrera, Ramon (American Physical Society (APS), 2023-10-06)
      Article
      Accés obert
      General relativity provides us with some solutions for rotating black holes. However, there are some problems associated with them: the appearance of singularities, the possibility of violations of the cosmic censorship ...

    • Mechanism of quasistabilization of primordial black holes 

      Torres Herrera, Ramon (2013-06-17)
      Article
      Accés obert
      It is argued that primordial black holes with initial masses satisfying M<1015 g, instead of having explode, might currently be in a quasistable phase contributing to a tiny fraction of the measured dark matter. This ...

    • Multiple paths to the final black hole 

      Ricart Vilarrubias, Oriol (Universitat Politècnica de Catalunya, 2022-05)
      Treball Final de Grau
      Accés obert
      Realitzat a/amb:   University of Texas at Austin
      La fusió d'un parell de forats negres crea un altre forat negre. Diverses fórmules fenomenològiques ajusten els resultats de les simulacions numèriques per predir la massa i l'spin dels forats negres finals donats els ...

    • Non-singular quantum improved rotating black holes and their maximal extension 

      Torres Herrera, Ramon (2017-06-01)
      Article
      Accés obert
      We add a prescription to the Newman–Janis algorithm in order to use it as a means of finding new extended rotating black hole spacetimes from static spherically symmetric ones. Then, we apply the procedure to a quantum ...

    • Nonsingular black holes, the cosmological constant and asymptotic safety 

      Torres Herrera, Ramon (2017-06-05)
      Article
      Accés obert
      Quantum gravitational effects in black hole spacetimes with a cosmological constant ¿ are considered. The effective quantum spacetimes for the black holes are constructed by taking into account the renormalization group ...

    • Nonsingular black holes, the cosmological constant, and asymptotic safety 

      Torres Herrera, Ramon (2017-07-15)
      Article
      Accés obert
      Quantum gravitational effects in black hole spacetimes with a cosmological constant ¿ are considered. The effective quantum spacetimes for the black holes are constructed by taking into account the renormalization group ...

    • On how energy conservation might prevent black hole explosions and violations of the third law 

      Torres Herrera, Ramon; Fayos Vallés, Francisco (2013-11-12)
      Article
      Accés obert
      We claim that imposing energy conservation to the emission of Hawking radiation and to the modeling of black hole (BH) evaporation might prevent BH explosions as well as violations of the third law of BH thermodynamics. ...

    • On regular rotating black holes 

      Torres Herrera, Ramon; Fayos Vallés, Francisco (2017-01-01)
      Article
      Accés obert
      Different proposals for regular rotating black hole spacetimes have appeared recently in the literature. However, a rigorous analysis and proof of the regularity of this kind of spacetimes is still lacking. In this note ...

    • On the interior of (quantum) black holes 

      Torres Herrera, Ramon (2013-06-20)
      Article
      Accés obert
      Different approaches to quantum gravity conclude that black holes may possess an inner horizon, in addition to the (quantum corrected) outer ‘Schwarzschild’ horizon. In this paper we assume the existence of this inner ...

    • Partículas huérfanas 

      Barceló Garcia, Miquel (1997-11)
      Article
      Accés obert

    • Primordial black holes capture by stars and induced collapse to low-mass stellar black holes 

      Oncins Marco, Gerard; Miralda Escudé, Jordi; Gutiérrez Cabello, Jordi; Gil Pons, Pilar (Oxford University Press, 2022-10-04)
      Article
      Accés obert
      Primordial black holes in the asteroid-mass window, which might constitute all the dark matter, can be captured by stars when they traverse them at low enough velocity. After being placed on a bound orbit during star ...

    • Probing black-hole accretion through time variability 

      Marco, Barbara de; Motta, Sara Elisa; Belloni, Tomaso M. (Springer, 2023-11-01)
      Capítol de llibre
      Accés restringit per política de l'editorial
      Flux variability is a remarkable property of black hole (BH) accreting systems and a powerful tool to investigate the multi-scale structure of the accretion flow. The X-ray band is where some of the most rapid variations ...