Past Pizza Lunches

Número de entradas: 154

15
Enero 2021

The observational properties of ultraluminous X-ray sources


Inicio: 12:00h
Ponente: Rajath Sathyaprakash (ICE, CSIC)
Lugar: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

Ultraluminous X-ray sources (ULXs) are extragalactic sources found in the off-nuclear regions of nearby galaxies with luminosities that appear to exceed the Eddington limit for a stellar mass black hole (BH). Historically, their extreme luminosities was interpreted as evidence that they host a population…
Inicio: 12:00h
Ponente: Rajath Sathyaprakash (ICE, CSIC)
Lugar: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

Ultraluminous X-ray sources (ULXs) are extragalactic sources found in the off-nuclear regions of nearby galaxies with luminosities that appear to exceed the Eddington limit for a stellar mass black hole (BH). Historically, their extreme luminosities was interpreted as evidence that they host a population of accreting intermediate mass black holes (IMBHs), which are crucial to understand the formation of supermassive black holes in the early universe. However, this picture has changed in the past decade with the availability of high quality X-ray observations from XMM-Newton, Chandra and NuSTAR, which instead suggest that a majority of the known ULXs contain regular stellar mass compact objects that appear to break the Eddington limit (although a few interesting IMBH candidates remain). This picture is also strengthened by the recent discoveries of a few pulsating ULXs suggesting such objects contain neutron stars (NSs), although it is currently unclear how they may overcome their Eddington limit and if they are predominant among ULXs in comparison to black holes. In this talk, I will provide an overview of the astrophysical properties of ULXs, discuss some key results that have emerged in the recent years, including my work on the recent discovery of an ultra luminous X-ray pulsar. 
18
Diciembre 2020

Euclid inside a Black Hole


Inicio: 12:00h
Ponente: Enrique Gaztañaga (ICE-CSIC,IEEC)
Lugar: Zoom: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

I will present a brief introduction (for non experts) to the metric of space-time and what role the metric plays in our understanding of Gravity (General Relativity). Euclid of Alexandria (300 BC), the Greek mathematician, was the founder of geometry. In the early 20th century, his only surviving book,…
Inicio: 12:00h
Ponente: Enrique Gaztañaga (ICE-CSIC,IEEC)
Lugar: Zoom: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691


I will present a brief introduction (for non experts) to the metric of space-time and what role the metric plays in our understanding of Gravity (General Relativity). Euclid of Alexandria (300 BC), the Greek mathematician, was the founder of geometry. In the early 20th century, his only surviving book, the Elements, was the second best selling book of all times. In the Elements, Euclid lay down the properties of the simplest possible metric, corresponding to that of flat space. This was generalised by Einstein's Special Relativity and Minkowski to that of flat space-time. Minkowski flat metric corresponds to empty space. The second simplest metric is the Schwarzschild metric, which represents empty space outside a static star or a Black Hole of mass M. I will them show how the metric of our expanding Universe can be interpreted as the inside of a Black Hole. For an external observer our Universe will look like a static Black Hole of mass M=5.8E22 solar masses. The accelerated expansion of the Universe today is then caused by the Black Hole event Horizon.
11
Diciembre 2020

Structured Jets and X-Ray Plateaus in Gamma-Ray Bursts


Inicio: 12:00h
Ponente: Stefano Ascenzi (ICE)
Lugar: Zoom https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

The X-ray emission of γ-ray burst (GRBs) is often characterized by an initial steep decay followed by a nearly constant emission phase (so-called "plateau") which can extend up to thousands of seconds. While the steep decay is usually interpreted as the tail of the prompt γ-ray flash, the long-lasting…
Inicio: 12:00h
Ponente: Stefano Ascenzi (ICE)
Lugar: Zoom https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

The X-ray emission of γ-ray burst (GRBs) is often characterized by an initial steep decay followed by a nearly constant emission phase (so-called "plateau") which can extend up to thousands of seconds. While the steep decay is usually interpreted as the tail of the prompt γ-ray flash, the long-lasting plateau is commonly associated to the emission from the external shock sustained by energy injection from a long-lasting central engine. In this talk I will present the result of a recent study, which propose an alternative interpretation, ascribing both the steep decay and the plateau to high-latitude emission (HLE) from a "structured jet" whose energy and bulk Lorentz factor depend on the angular distance from the jet symmetry axis. I will also show that even when the GRB is observed off-axis this model predicts a bright X-ray transient, which can constitute an interesting target for follow-up observational campaigns of gravitational wave events.
10
Diciembre 2020

Special Christmas seminar: A Topological Data Analysis perspective on coronavirus evolution


Inicio: 16:30h
Ponente: Raul Rabadan (Columbia University New York, US)
Lugar: https://us02web.zoom.us/j/87666609687?pwd=aVEybW1TZHdaZmo5UFpFdURmeU9IUT09 Meeting ID: 876 6660 9687 Passcode: 210027

Raul Rabadan is theoretical physicist and computational biologist. After getting his PhD in Theoretical Physics, he did post-doctoral work at CERN in Geneva, Switzerland and the Institute for Advanced Study in Princeton, before joining Columbia University as a faculty member.  At Columbia University,…
Inicio: 16:30h
Ponente: Raul Rabadan (Columbia University New York, US)
Lugar: https://us02web.zoom.us/j/87666609687?pwd=aVEybW1TZHdaZmo5UFpFdURmeU9IUT09 Meeting ID: 876 6660 9687 Passcode: 210027

Raul Rabadan is theoretical physicist and computational biologist. After getting his PhD in Theoretical Physics, he did post-doctoral work at CERN in Geneva, Switzerland and the Institute for Advanced Study in Princeton, before joining Columbia University as a faculty member.  At Columbia University, Dr. Rabadan directs  the Program for Mathematical Genomics and the Center for Topology of Cancer Evolution and Heterogeneity. He applies quantitative approaches to model and understand the dynamics of biological systems through the lens of genomics. His research focuses on the evolution of two biological systems, namely cancer and infectious diseases. In the area of infectious diseases, he studies the evolution of emerging pathogens by the analysis of their genomes, in particular the genomes of RNA viruses such as influenza and coronaviruses. His recent book, “Understanding Coronavirus” provides a concise and accessible introduction to the coronavirus SARS-COV-2 which has caused the ongoing global pandemic. He is also the author of a textbook about the use of topological methods in genomic analysis (“Topological Data Analysis for Genomics and Evolution: Topology in Biology”). This seminar will present an overview of the origin and evolution of the pandemic virus and how topological techniques can help to elucidate the emergence of these viruses.
04
Diciembre 2020

Simultaneous Planet and Star Formation


Inicio: 12:00h
Ponente: Josep Miquel Girart Medina (ICE-CSIC)
Lugar: Zoom: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

The study of the formation and evolution of disks around young stars has been boosted since the Atacama Large Millimeter/submillimeter Array (ALMA) has been opened for science observations. While it is widely accepted that planets are formed in protoplanetary disks, there is still much debate on when…
Inicio: 12:00h
Ponente: Josep Miquel Girart Medina (ICE-CSIC)
Lugar: Zoom: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

The study of the formation and evolution of disks around young stars has been boosted since the Atacama Large Millimeter/submillimeter Array (ALMA) has been opened for science observations. While it is widely accepted that planets are formed in protoplanetary disks, there is still much debate on when this process happens. In a few cases protoplanets have been directly imaged, but for the vast majority of systems, disk gaps and cavities – seen especially by ALMA in dust continuum observations – have been the strongest evidence of recent or on-going planet formation. Here I will present two very different cases of star and planet formation that are occurring in a small nascent open cluster around/within the nearby molecular Barnard 59 molecular dense core. Interestingly, these two cases have been serendipitous discoveries with ALMA in a project where we were aimed to study the role of magnetic fields in the formation and evolution of accretion disks around young stars. 
27
Noviembre 2020

On the Rate of Crustal Failures in Young Magnetars


Inicio: 12:00h
Ponente: Clara Dehman (ICE)
Lugar: Zoom: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

The activity of magnetars is powered by their intense and dynamic magnetic fields and has been proposed as the trigger to extragalactic fast radio bursts. Here we estimate the frequency of crustal failures in young magnetars, by computing the magnetic stresses in detailed magnetothermal simulations…
Inicio: 12:00h
Ponente: Clara Dehman (ICE)
Lugar: Zoom: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

The activity of magnetars is powered by their intense and dynamic magnetic fields and has been proposed as the trigger to extragalactic fast radio bursts. Here we estimate the frequency of crustal failures in young magnetars, by computing the magnetic stresses in detailed magnetothermal simulations including Hall drift and ohmic dissipation. The initial internal topology at birth is poorly known but is likely to be much more complex than a dipole. Thus, we explore a wide range of initial configurations, finding that the expected rate of crustal failures varies by orders of magnitude depending on the initial magnetic configuration. Our results show that this rate scales with the crustal magnetic energy, rather than with the often used surface value of the dipolar component related to the spin-down torque. Our results are useful inputs in modeling the outburst rate of young Galactic magnetars, and their relation with the fast radio bursts in our and other galaxies.
20
Noviembre 2020

From a Bounce to the Dark Energy Era with F(R) Gravity


Inicio: 12:15h
Ponente: Prof. Tanmoy, P.
Lugar: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09

In this work we consider a cosmological scenario in which the Universe contracts initially having a bouncing-like behavior, and accordingly after it bounces off, it decelerates following a matter dominated like evolution and at very large positive times it undergoes through an accelerating stage. Our…
Inicio: 12:15h
Ponente: Prof. Tanmoy, P.
Lugar: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09

In this work we consider a cosmological scenario in which the Universe contracts initially having a bouncing-like behavior, and accordingly after it bounces off, it decelerates following a matter dominated like evolution and at very large positive times it undergoes through an accelerating stage. Our aim is to study such evolution in the context of F(R) gravity theory, and confront quantitatively the model with the recent observations. Using several reconstruction techniques, we analytically obtain the form of F(R) gravity in two extreme stages of the universe, particularly near the bounce and at the late time era respectively. With such analytic results and in addition by employing appropriate boundary conditions, we numerically solve the F (R) gravitational equation to determine the form of the F (R) for a wide range of values of the cosmic time. The numerically solved F (R) gravity realizes an unification of certain cosmological epochs of the universe, in particular, from a non-singular bounce to a matter dominated epoch and from the matter dominated to a late time dark energy epoch. Correspondingly, we calculate the scalar and tensor perturbations power spectra near the bouncing point, and accordingly we determine the observable quantities like the spectral index of the scalar curvature perturbations, the tensor-to-scalar ratio, and as a result, we directly confront the present model with the latest Planck observations. Furthermore the F (R) gravity dark energy epoch is confronted with the Sne-Ia+BAO+H(z)+CMB data.
13
Noviembre 2020

Neutron Stars - Cosmic Superfluids and Superconductors


Inicio: 12:15h
Ponente: Vanessa Graber (ICE)
Lugar: Zoom: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

Neutron stars unite many extremes of physics which cannot be recreated on Earth, making them excellent cosmic laboratories to study dense matter. One exciting characteristic is the presence of superfluid and superconducting components in mature neutron stars; macroscopic quantum behaviour that exhibits…
Inicio: 12:15h
Ponente: Vanessa Graber (ICE)
Lugar: Zoom: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

Neutron stars unite many extremes of physics which cannot be recreated on Earth, making them excellent cosmic laboratories to study dense matter. One exciting characteristic is the presence of superfluid and superconducting components in mature neutron stars; macroscopic quantum behaviour that exhibits many similarities to terrestrial systems such as superfluid phases in ultra-cold atomic gases, heavy-ion collisions or superconducting transitions in metals. Although many theoretical models of superfluid and superconducting neutron stars have benefited from our understanding of laboratory condensates, several directions in connecting neutron star astrophysics and low-temperature physics remain little explored. In this talk, I will provide an overview of what we know about superfluid and superconducting neutron star components, and specifically focus on two aspects, pulsar spin-glitches and core superconductivity, where the link to laboratory quantum systems can help us improve our understanding of neutron stars.
06
Noviembre 2020

The Nüwa project - a Martian city that can sustain its own growth


Inicio: 12:15h
Ponente: Guillem Anglada Escude (ICE)
Lugar: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09

Is it possible to build a human settlement that can sustain its own growth? With the sight put into developing a long term and sustainable presence of human activities in space, a very fundamental question that needs to be addressed is whether a human settlement can be developed and self-sustain on another…
Inicio: 12:15h
Ponente: Guillem Anglada Escude (ICE)
Lugar: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09

Is it possible to build a human settlement that can sustain its own growth? With the sight put into developing a long term and sustainable presence of human activities in space, a very fundamental question that needs to be addressed is whether a human settlement can be developed and self-sustain on another planet. Despite there seems to be no physical barriers to achieve it, it is unclear if all the material cycles and be closed to the required level and if the amount of workload the average human should endure is manageable. To start a conversation on this topic, The Sustainable Offworld Netword (SONet) performed a design exercise to answer a call along this lines issed by the Mars Society. We proceeded in an engineering desing way listing functions, identifying requirements, and drafting solutions to cover both technical and socio-economic aspects in a multi-disciplinary collaboration. I will present you a summary of the findings, the 'costs' in terms of materials and resources, and discuss its feasibility with our current technological level.
30
Octubre 2020

The neutron star population in our Galaxy


Inicio: 12:15h
Ponente: Nanda Rea ((ICE-CSIC, IEEC))
Lugar: Zoom: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

I will review the group research activity of the past months, focusing on the recent detection of two interesting new highly magnetic neutron stars in our Galaxy. I will finish with some preliminary studies on the comparison of our neutron star population, with the Universe most extreme events such as…
Inicio: 12:15h
Ponente: Nanda Rea ((ICE-CSIC, IEEC))
Lugar: Zoom: https://us02web.zoom.us/j/85044910172?pwd=bXRmeWx3cTdDSzkrMFFJUXI5eE9hQT09 Meeting ID: 850 4491 0172 Passcode: 996691

I will review the group research activity of the past months, focusing on the recent detection of two interesting new highly magnetic neutron stars in our Galaxy. I will finish with some preliminary studies on the comparison of our neutron star population, with the Universe most extreme events such as Gamma Ray Bursts and Fast Radio Bursts.
Institute of Space Sciences (IEEC-CSIC)

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An institute of the Consejo Superior de Investigaciones Científicas

An institute of the Consejo Superior de Investigaciones Científicas
Affiliated with the Institut d'Estudis Espacials de Catalunya

Affiliated with the Institut d'Estudis Espacials de Catalunya