Gamma-ray flares from black hole coronae

We present results of a study of non-thermal, time-dependent particle injection in a corona around an accreting black hole. We model the spectral energy distribution of high-energy flares in this scenario. We consider particle interactions with magnetic, photon and matter fields in the black hole magnetosphere. Transport equations are solved for all species of particles and the electromagnetic output is predicted. Photon annihilation is taken into account for the case of systems with early-type donor stars.Comment: 7 pages, 7 figures. Accepted for publication in the Proceedings of the 25th Texas Symposium on Relativistic Astrophysics, held in Heidelberg, December 06-10, 201

Gravitational Lensing of Neutrino from Collapsars

We study neutrino emission from long gamma-ray bursts. The collapse of very massive stars to black holes, and the consequent jet formation, are expected to produce high-energy neutrinos through photomeson production. Such neutrinos can escape from the source and travel up to the Earth. We focus on the case of Population III progenitors for gamma-ray bursts. Neutrinos can be the only source of information of the first stars formed in the universe. The expected signal is rather weak, but we propose that gravitational lensing by nearby supermassive black holes might enhance the neutrino emission in some cases. We implement a Monte Carlo analysis to ponder the statistical significance of this scenario. We suggest that an observational strategy based on gravitational lensing could lead to the detection of neutrinos from the re-ionization era of the universe with current instrumentation.Comment: 5 pages, 3 figures. Accepted for publication in the Proceedings of the First Argentine-Brazilian Meeting on Gravitation, Astrophysics and Cosmology, held in Foz do Igua\c{c}u, October, 201

A model for the polarization of the high-energy radiation from accreting black holes: the case of XTE J1118+480

The high-energy emission ($400$ keV $- 2$ MeV) of Cygnus X-1 --the most well-studied Galactic black hole-- was recently found to be strongly polarized. The origin of this radiation is still unknown. In this work, we suggest that it is the result of non-thermal processes in the hot corona around the accreting compact object, and study the polarization of high-energy radiation expected for black hole binaries. Two contributions to the total magnetic field are 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 is estimated, as well as the angle of the polarization vector. We obtain that the corona+disk configuration studied in this work can account for the high degree of polarization of gamma-rays detected in galactic black holes without the need of a relativistic jet; specific predictions are made for sources in a low-hard state. In particular, the model is applied to the transient source \xtee; we show that if a new outburst of \xte is observed, then its gamma-ray polarization should be measurable by future instruments, such as ASTRO-H or the proposed ASTROGAM.Comment: 8 pages, 6 figures, accepted for publication in A&

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 scale factor and the entropy.Comment: 8 pages, 7 figures. Modified to match the published versio

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 Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Vieyro, Florencia Laura. Universidad de Barcelona; España. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Romero, Gustavo Esteban. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; Argentin

A mechanism for fast radio bursts

Fast radio bursts are mysterious transient sources likely located at cosmological distances. The derived brightness temperatures exceed by many orders of magnitude the self-absorption limit of incoherent synchrotron radiation, implying the operation of a coherent emission process. We propose a radiation mechanism for fast radio bursts where the emission arises from collisionless Bremsstrahlung in strong plasma turbulence excited by relativistic electron beams. We discuss possible astrophysical scenarios in which this process might operate. The emitting region is a turbulent plasma hit by a relativistic jet, where Langmuir plasma waves produce a concentration of intense electrostatic soliton-like regions (cavitons). The resulting radiation is coherent and, under some physical conditions, can be polarised and have a power-law distribution in energy. We obtain radio luminosities in agreement with the inferred values for fast radio bursts. The timescale of the radio flare in some cases can be extremely fast, of the order of $10^{-3}$ s. The mechanism we present here can explain the main features of fast radio bursts and is plausible in different astrophysical sources, such as gamma-ray bursts and some Active Galactic Nuclei.Comment: 6 pages, 1 figure. Accepted for publication in Phys. Rev.

Non-thermal radiation from Cygnus X-1 corona

Cygnus X-1 was the first X-ray source widely accepted to be a black hole candidate and remains among the most studied astronomical objects in its class. The detection of non-thermal radio, hard X-rays and gamma rays reveals the fact that this kind of objects are capable of accelerating particles up to very high energies. In order to explain the electromagnetic emission from Cygnus X-1 in the low-hard state we present a model of a black hole corona with both relativistic lepton and hadron content. We characterize the corona as a two-temperature hot plasma plus a mixed non-thermal population in which energetic particles interact with magnetic, photon and matter fields. Our calculations include the radiation emitted by secondary particles (pions, muons and electron/positron pairs). Finally, we take into account the effects of photon absorption. We compare the results obtained from our model with data of Cygnus X-1 obtained by the COMPTEL instrument.Comment: 6 pages, 10 figures, presented as a poster in HEPRO II, Buenos Aires, Argentina, October 26-30 2009 / accepted for publication in Int. Jour. Mod. Phys.

Episodic gamma-ray and neutrino emission from the low mass X-ray binary GRO J0422+32

GRO J0422+32 is a member of the class of low-mass X-ray binary (LMXB) sources, discovered during an outburst in 1992. Along the entire episode ($\sim 230$ days) a persistent power-law spectral component extending up to $\sim 1$ MeV was observed. These results suggest that non-thermal processes must be at work in the system. We apply a corona model to describe the spectrum of GRO J0422+32 during the flaring phase. We study relativistic particle interactions solving the transport equations for all type of particles self-consistently. We fit the electromagnetic emission during the plateau phase of the event and estimate the emission during an energetic episode, as well as the neutrino production. Our work leads to predictions that can be tested by the new generation of very high energy gamma-ray instruments.Comment: HIGH ENERGY GAMMA-RAY ASTRONOMY: 5th International Meeting on High Energy Gamma-Ray Astronomy. AIP Conference Proceedings, Volume 1505, pp. 410-413 (2012

La preparación física en deportes de situación : El caso de Bolivia respecto de Argentina

La siguiente ponencia tiene como objetivo mostrar algunas diferencias entre la preparación física dentro del deporte boliviano (La Paz, más específicamente) en comparación con la preparación física en Argentina, principalmente en el tenis y el fútbol. La exposición demostrará datos estadísticos que demuestren estas diferencias (testeos, evaluaciones), hablaremos sobre las condiciones socioeconómicas de cada país, la idiosincrasia respecto del deporte de cada uno, además de videos explicativos y de ejercicios que pondrán en evidencias dichas diferencias. El tipo de preparación física del que se hablará es sobre los de deportes acíclicos, deportes de situación. Una explicación general al respecto, conceptos generales y específicos sobre los contenidos que consideramos importantes aplicar en este tipo de deportes, por el poco tiempo y disponibilidad que tenemos los preparadores físico

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 Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Vieyro, Florencia Laura. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaThirteenth Marcel Grossmann MeetingEstocolmoSueciaStockholm Universit