41 research outputs found
High-energy astrophysics on compact objects accretion on all scales
La emisión gamma es la evidencia mas fuerte de que procesos no-térmicos tienen lugar en una fuente astrofÃsica. Estos procesos son el resultado de la presencia de partÃculas relativistas que interaccionan con los diferentes campos, como el campo magnético, de radiación y de materia frÃa. En este trabajo, se describirán los principales procesos radiactivos que las partÃculas sufren en ambientes extremos, que dan lugar a que gran parte de la emisión se produzca en altas energÃas. Se presentará la fenomenologÃa asociada a las diferentes clases de fuentes con objetos compactos, con particular interés en aquellas sustentadas por la acreción sobre agujeros negros. Finalmente se discutirán algunos de los problemas abiertos asociados a estas fuentes.Gamma-ray emission is the ultimate evidence that non-thermal processes are taking place in an astrophysical source. These processes are the result of the presence of relativistic particles interacting with different fields, such as magnetic, radiation or cold matter fields. In this article, I describe the main radiative processes that particles undergo in extreme environments, that result in a significant fraction of the total emitted power to be released in the gamma-domain. I present the phenomenology related to the different classes of highenergy sources involving compact objects, with particular interest in those powered by accretion into black holes. Finally, I discuss some of the open questions associated with these sources.Fil: Vieyro, Florencia Laura. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y GeofÃsicas; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones CientÃficas. Instituto Argentino de RadioastronomÃa. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Instituto Argentino de RadioastronomÃa; ArgentinaSegunda Reunión Binacional de Asociación Argentina de AstronomÃa y Sociedad Chilena de AstronomÃaLa SerenaChileAsociación Argentina de AstronomÃaUniversidad de La Seren
Neutrino emission from gamma-ray bursts
Gamma-ray bursts (GRBs) are the most violent and energetic events in theuniverse. Short GRBs seem to be the result of the final merger of two compactobjects, whereas long GRBs are probably associated with the gravitationalcollapse of very massive stars (collapsars).The central engine of a GRB can collimate relativistic jets, where shocksare produced and particles can be accelerated. Although the exact location ofthe region where the gamma rays are created is still under debate, it is widelyaccepted that the prompt emission has a different origin from the afterglow. Thelatter is emitted at a much greater distance from the central engine, when thefireball is decelerated by its interaction with the interstellar medium.It seems reasonable to assume that if the prompt gamma-ray radiation andthe afterglows are generated by relativistic electrons accelerated in shocks, thenthe same shocks should also accelerate baryons. These high-energy protons canproduce neutrinos through pp inelastic collisions and pγ interactions, makingGRBs candidates to be sources of high-energy neutrinos.In this review, I discuss different scenarios where high-energy neutrinos(GeV-EeV) can be generated.Fil: Vieyro, Florencia Laura. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones CientÃficas. Instituto Argentino de RadioastronomÃa. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Instituto Argentino de RadioastronomÃa; ArgentinaSecond Argentinian-Brazilian Meeting: Gravitation, Astrophysics, and Cosmology (GRACO)Buenos AiresArgentinaInstituto Argentino de RadioastronomÃ
Efectos de partÃculas relativistas en el entorno de agujeros negros
En la presente Tesis se realiza un estudio de los procesos fÃsicos que producen la emisión electromagnética y de neutrinos a altas energÃas en la vecindad de agujeros negros estelares que acretan materia.
Se estudia la inyección de partÃculas no térmicas en la corona de agujeros negros galácticos. Primero se caracteriza la región de interacción, detallando propiedades fÃsicas básicas de los sistemas en estudio. Inicialmente se inyecta una población de electrones y protones relativistas, considerándose también la generación de partÃculas secundarias (piones, muones y pares electrón/positrón). Luego, se estiman los tiempos de enfriamiento por las diversas interacciones entre las partÃculas y los campos en la fuente. Una vez identificados los procesos radiativos más relevantes, se resuelve de manera auto-consistente el transporte de partÃculas masivas y de fotones. Este estudio se hace tanto para el estado estacionario, como para casos transitorios, como ser fulguraciones.
Además de la emisión electromagnética y de neutrinos de la fuente, se estudia el impacto de los neutrones creados en las interacciones hadrónicas sobre el medio circundante de la corona. En particular, se investiga la inyección de neutrones como posible mecanismo para cargar de bariones un jet inicialmente dominado magnéticamente.
Por último se hace una aplicación del método desarrollado para tratar el transporte de partÃculas relativistas en plasmas magnetizados, a las erupciones de rayos gamma. En este caso, se investiga la producción de neutrinos en el modelo de colapsar, abriéndose una nueva lÃnea de trabajo.
Para todos los sistemas estudiados se hacen predicciones sobre la emisión a muy alta energÃa y la producción de neutrinos; estos resultados podrán ser contrastados en un futuro cercano con nuevos detectores de rayos gamma y de neutrinos (e.g., CTA, IceCube).Facultad de Ciencias Astronómicas y GeofÃsica
Primordial black hole evolution in two-fluid cosmology
Several processes in the early Universe might lead to the formation of primordial black holes with different masses. These black holes would interact with the cosmic plasma through accretion and emission processes. Such interactions might have affected the dynamics of the Universe and generated a considerable amount of entropy. In this paper, we investigate the effects of the presence of primordial black holes on the evolution of the early Universe. We adopt a two-fluid cosmological model with radiation and a primordial black hole gas. The latter is modelled with different initial mass functions taking into account the available constraints over the initial primordial black hole abundances.We find that certain populations with narrow initial mass functions are capable to produce significant changes in the scalefactor and the entropy.Fil: Gutiérrez, Eduardo Mario. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones CientÃficas. Instituto Argentino de RadioastronomÃa. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Instituto Argentino de RadioastronomÃa; ArgentinaFil: Vieyro, Florencia Laura. Universidad de Barcelona; España. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones CientÃficas. Instituto Argentino de RadioastronomÃa. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Instituto Argentino de RadioastronomÃa; ArgentinaFil: Romero, Gustavo Esteban. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones CientÃficas. Instituto Argentino de RadioastronomÃa. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Instituto Argentino de RadioastronomÃa; Argentin
Flares from galactic black holes
In this work we study the effects of a time-dependent injection of a non-thermal particle population in a corona around an accreting black hole. We present a specific model for high-energy flares in this scenario. We consider particle interactions with magnetic, photon, and matter fields in the corona around the black hole. Transport equations are solved for all species of particles and the electromagnetic output is computed for the case of Galactic black hole binaries.Fil: Vieyro, Florencia Laura. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones CientÃficas. Instituto Argentino de RadioastronomÃa. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Instituto Argentino de RadioastronomÃa; ArgentinaFil: Romero, Gustavo Esteban. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones CientÃficas. Instituto Argentino de RadioastronomÃa. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Instituto Argentino de RadioastronomÃa; ArgentinaXIII Reunión Regional Latinoamericana de la IAUMoreliaMéxicoUniversidad Nacional Autónoma de Méxic
Relativistic Particles in Magnetized Media around Black Holes
We study non-thermal processes produced by the injection of relativistic particles in a strongly magnetized corona around an accreting black hole. The spectral energy distribution produced in this component of X-ray binaries can be strongly affected by different interactions between locally injected relativistic particles and the different fields of the source. We compute in a self-consistent way the effects of relativistic Bremsstrahlung, inverse Compton scattering, synchrotron radiation, and pair-production/annihilation of leptons, as well as of hadronic interactions. Our goal is to determine the non-thermal broadband radiative output of the corona. The set of coupled kinetic equations for electrons, positrons, protons and photons are solved and the resulting particle distributions are computed self-consistently. We apply our model to Cygnus X-1 obtaining a good fit of the observational data.Fil: Romero, Gustavo Esteban. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones CientÃficas. Instituto Argentino de RadioastronomÃa. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Instituto Argentino de RadioastronomÃa; ArgentinaFil: Vieyro, Florencia Laura. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones CientÃficas. Instituto Argentino de RadioastronomÃa. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - La Plata. Instituto Argentino de RadioastronomÃa; ArgentinaThirteenth Marcel Grossmann MeetingEstocolmoSueciaStockholm Universit
Coronal origin of the polarization of the high-energy emission of Cygnus X-1
Context. Cygnus X-1 is the candidate with the highest probability of containing a black hole among the X-ray binary systems in the Galaxy. It is also by far the most often studied of these objects. Recently, the International Gamma-Ray Astrophysics Laboratory Imager on board the Integral satellite (INTEGRAL/IBIS) detected strong polarization in the high-energy radiation of this source, between 400 keV and 2 MeV. This radiation has been attributed to a jet launched by the black hole.
Aims. We consider whether the corona around the black hole might be the site of production of the polarized emission instead of the jet.
Methods. We studied self-consistently the injection of nonthermal particles in the hot, magnetized plasma around the black hole.
Results. We show that both the high-energy spectrum and polarization of Cygnus X-1 in the low-hard state can originate in the corona, without needing to invoke a jet. We estimate the degree of polarization in the intermediate state, where there is no jet, to provide a tool to test our model.
Conclusions. Contrary to the commonly accepted view, the jet might not be the source of the MeV polarized tail in the spectrum of Cygnus X-1.Facultad de Ciencias Astronómicas y GeofÃsicasInstituto Argentino de RadioastronomÃ
Modeling the polarization of high-energy radiation from accreting black holes : A case study of XTE J1118+480
Context. The high-energy emission (400 keV-2 MeV) of Cygnus X-1, which is the best-studied Galactic black hole, was recently found to be strongly polarized. The origin of this radiation is still unknown.
Aims. We suggest that the emission is the result of non-thermal processes in the hot corona around the accreting compact object and study the polarization of high-energy radiation that is expected for black hole binaries.
Methods. Two contributions to the total magnetic field were taken into account in our study: a small-scale random component related to the corona, and an ordered magnetic field associated with the accretion disk. The degree of polarization of gamma-ray emission for this particular geometry was estimated together with the angle of the polarization vector.
Results. We obtain that the configuration of corona plus disk can account for the high degree of polarization of gamma-rays that are detected in galactic black holes and does not need to invoke a relativistic jet. We make specific predictions for sources in a low-hard state. In particular, the model is applied to the transient source XTE J1118+480. We show that if a new outburst of XTE J1118+480 is observed, then its gamma-ray polarization should be measurable by future instruments, such as ASTRO-H or the proposed ASTROGAM.Facultad de Ciencias Astronómicas y GeofÃsicasInstituto Argentino de RadioastronomÃ
Non-thermal processes around accreting galactic black holes
Context. Accreting black holes in galactic X-ray sources are surrounded by hot plasma. The innermost part of these systems is likely a corona with different temperatures for ions and electrons. In the so-called low-hard state, hot electrons Comptonize soft X-ray photons from the disk that partially penetrates the corona, producing emission up to ∼150 keV, well beyond the expectations for an optically
thick disk of maximum temperature ∼107 K. However, sources such as Cygnus X-1 produce steady emission up to a few MeV, which is indicative of a non-thermal contribution to the spectral energy distribution.
Aims. We study the radiative output produced by the injection of non-thermal (both electron and proton) particles in a magnetized corona around a black hole.
Methods. Energy losses and maximum energies are estimated for all types of particles in a variety of models, characterized by different kinds of advection and relativistic proton content. Transport equations are solved for primary and secondary particles, and spectral energy distributions are determined and corrected by internal absorption.
Results. We show that a local injection of non-thermal particles can account for the high energy excess observed in some sources, and we predict the existence of a high-energy bump at energies above 1 TeV, and typical luminosities of ∼1033 erg s−1.
Conclusions. High-energy instruments such as the future Cherenkov Telescope Array (CTA) can be used to probe the relativistic particle content of the coronae around galactic black holes.Fil: Romero, Gustavo Esteban. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico La Plata. Instituto Argentino de Radioastronomia (i); Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y GeofÃsicas; ArgentinaFil: Vieyro, Florencia Laura. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico La Plata. Instituto Argentino de Radioastronomia (i); ArgentinaFil: Vila, Gabriela Soledad. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico La Plata. Instituto Argentino de Radioastronomia (i); Argentin
Neutron production in black hole coronae and proton loading of jets
We study the production of neutrons in the corona of an accreting black hole through the interaction of locally accelerated protons with matter and radiation. A fraction of these neutrons may escape and penetrate into the base of the jet, later decaying into protons. This is a possible mechanism for loading Poynting-dominated outflows with baryons. We characterize the spatial and energy distribution of neutrons in the corona and that of the protons injected in the jet by neutron decay. We assess the contribution of these protons to the radiative spectrum of the jet. We also investigate the fate of the neutrons that escape the corona into the external medium.Fil: Vila, Gabriela Soledad. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico la Plata. Instituto Argentino de Radioastronomia (i); ArgentinaFil: Vieyro, Florencia Laura. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico la Plata. Instituto Argentino de Radioastronomia (i); ArgentinaFil: Romero, Gustavo Esteban. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico la Plata. Instituto Argentino de Radioastronomia (i); Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Astronómicas y GeofÃsicas; Argentin