Found 20 talks width keyword black holes

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Tuesday May 17, 2022
Prof. Gastón Giribet
Universidad de Buenos Aires

Abstract

In this talk, I will review the recently discovered infinite-dimensional symmetries that emerge in the near horizon region of black hole horizons. I will explain how the conserved charges associated with those symmetries carry information of the black hole, and, in particular, about its thermodynamic properties. I will focus on the case of magnetized black holes; namely, black holes that are embedded in strong magnetic fields.




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Thursday December 2, 2021
Prof. Roberto Maiolino
Kavli Cambridge

Abstract

In the local universe most of the stellar mass is in passive galaxies, where star formation is
absent or at very low levels. Understanding what are the mechanisms that have been
responsible for quenching star formation in galaxies, and transforming them into passive,
quiescent systems, is one of the main observational and theoretical challenges of extragalactic
astrophysics. I will give a brief overview of the several possible quenching causes and physical
processes that have been proposed so far, ranging from feedback from black hole accretion and
starburst activity, to effects associated with the large scale environment in which galaxies live.
Although most of these mechanisms and causes play a role in different classes of galaxies and
at different epochs, multi-band observations are providing growing evidences that just a few of
them play the key, dominant role.
I will conclude by providing prospects for further investigating these aspects and tackling open
questions with the next generation of observing facilities.


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Thursday June 3, 2021
Dr. Javier Redondo
Universidad de Zaragoza

Abstract

We introduce the strong CP problem and the existence of the Axion as a possible solution. 

We discuss the possibility that axions are the dark matter of the Universe and the possible ways to

detect it or disprove it using: direct laboratory experiments as well as astrophysical and cosmological

arguments. 

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Thursday May 27, 2021
Dr. Manuela Bischetti
INAF/Trieste

Abstract

This talk will be dedicated to luminous (LBol~1E47 erg/s),
high-redshift quasars, which are ideal targets to investigate (i) feedback
from SMBHs, and (ii) the early growth phases of giant galaxies. I will
present evidence of  SMBH-driven outflows  at all Cosmic epochs, back to
the early Universe. These outflows involve all gas phases (molecular,
neutral, ionised) and extend on nuclear to galactic and circum-galactic
scales. I will report on the first systematic study of the molecular gas
properties in the host-galaxies of the most luminous quasars, fundamental
to probe the impact of SMBH feedback on the host-galaxy evolution. I will
show that luminous quasars pinpoint high-density sites where giant galaxies
assemble, and I will discuss the major contribution of mergers to the final
galaxy mass. To this aim, I will present a wealth of multi-wavelength (UV
to sub-millimeter) observations from the WISE/SDSS hyper-luminous quasars
survey  at z~2-5 (WISSH), and recent results from the ESO large program
XQR-30, the Ultimate X-SHOOTER Legacy Survey of Quasars at the Reionization
epoch.

 


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Tuesday June 27, 2017
Dr. Alicia López Oramas
Instituto de Astrofisica de Canarias

Abstract

The improvement on the Imaging Air Cherenkov Technique led to the discovery of a new class of compact binaries: the gamma-ray binaries. This small class consist  of only five members, all of them composed by a massive star and a compact object. The nature of the compact object is unknown for all of them but PSR B1259-63, which contains a pulsar. It is crucial to study and monitor these systems not only to understand their behavior, the scenario accounting for the gamma-ray emission and their nature but also to comprehend why we have not detected more sources of this exclusive family. In this presentation, I will review the state-of-the-art of this field and I will present the observations performed with the MAGIC telescopes in order to unveil the nature of gamma-ray binaries.


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Tuesday March 11, 2014
Dr. Martin López Corredoira
IAC

Abstract

1) López-Corredoira & Gutiérrez (2012, RAA, 12, 249): Extremely luminous QSOs exist at high redshift but they are absent at low redshift. Our analyses show that it is not due to any significant evolution of black hole masses or Eddington ratios for equal luminosity QSOs, so the problem can be translated into a "Why are not there QSOs with very high black hole masses at low redshift?". 2) López-Corredoira & Perucho (2012, A&A, 544, 56): The MOJAVE survey contains 101 quasars with a total of 354 observed radio components that are different from the radio cores, among which 95% move with apparent projected superluminal velocities with respect to the core, and 45% have projected velocities larger than 10c (with a maximum velocity 60c). Relativistic Doppler boosting explains these apparent anomalies, but it requires a huge average kinetic power to produce such powerful ejections: ~7×10^{47} erg/s, a significant portion of the Eddington luminosity and on the order of the bolometric luminosity. This amount is much higher than previous estimates of kinetic power on kpc-scales. 3) There are many other pending problems in QSOs in the literature (review at López-Corredoira 2011, IJAA, 1, 73): the different structure of the clouds along the QSO's line of sight and their tangential directions; the spatial correlation between QSOs and galaxies; inconsistencies in the AGN unification model; etc.


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Thursday November 28, 2013
Prof. Michiel van der Klis
Astronomical Institute, University Amsterdam, the Netherlands

Abstract

The matter within a few Schwarzschild radii of accreting neutron stars and black holes is moving under the influence of a strong gravitational field, and, in stellar mass compact objects, through strongly curved spacetime. The X-rays emitted in the accretion process can be used to diagnose this motion, using both spectroscopy and rapid time variability. Similarly, X-rays emitted from the surface of accreting neutron stars can be used to diagnose neutron star mass, radius and even internal structure. I discuss these ways to probe strong gravitational fields and ultradense matter from an empirical perspective and in the context of proposed future X-ray observatories, in particular, LOFT.


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Thursday July 4, 2013
Dr. Tom Maccarone
Texas Tech University

Abstract

In the past few years, a series of discoveries have been made of objects which appear to be accreting stellar mass black holes in globular clusters -- both in the Milky Way and in other nearby galaxies. I will discuss why the theoretical work which suggested that such objects would be unlikely to exist, the observations showing they do exist, some of the unusual aspects of some of the individual sources, and the new theoretical framework for producing them.


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Tuesday April 9, 2013
Dr. Teodoro Muñoz Darias
University of Southampton

Abstract

X-ray observations performed by several missions during the last few decades have provided a very large data base on black hole X-ray binaries. Many of these objects are transient systems that spend most part of their lives in quiescence, showing occasional outburst where their luminosity increases up to eight orders of magnitude. I will review the state-of-the-art in the field, focussing on the different accretion regimes observed in these sources. In the second part of the talk I will concentrate on the influence that the orbital inclination (i.e., viewing angle) has in the spectral properties of black hole binaries, with emphasis on the detection of relativistic effects in the inner accretion flow surrounding the black hole.


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Wednesday March 6, 2013
Dr. Jesús Corral Santana
IAC

Abstract

X-ray transients are binary systems composed by a 'normal' star which is transfering mass onto a compact object (either a black hole or a neutron star) through Roche lobe overflow. These systems show sporadic outburst episodes and long quiescence states, being ideal systems to search for stellar-mass black holes. Different studies predict a Galactic population of ~10^3-10^4 X-ray transients, however, there are only 18 stellar-mass black holes dynamically confirmed (and other ~32 candidates whichc share similar timing and spectral properties).

In this talk I'll present the case of Swift J1357.2-0933, a new X-ray transient discovered in 2011. Our analysis shows that Swift J1357.2-0933 is the first black hole transient seen at a large inclination (>75º). High time resolution lightcurves show dips or eclipses produced by a vertical structure present in the inner accretion rather than the companion star. Some dips display up to ~50% reduction of flux in ~2min (~30% reduction of flux in 7s). Moreover, the dips present a recurrence period of a few minutes which increases with time. This can only be explained by the expansion of the obscuring structure outward in the accretion. Swift J1357.2-0933 could be the prototype of an hytherto Galactic population of black hole transients with large inclinations.


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