Archivi tag: neutron stars

Origin of Matter and Evolution of Galaxies

The 13th international symposium on Origin of Matter and Evolution of Galaxies (OMEG2015) will be held in Beijing, China on June 24-27, 2015. This symposium is the 13th of such series, started 1988, to exchange the progress of nuclear astrophysics and related fields. As demonstrated in previous ones, this symposium series provide good opportunity to attract researchers in fields of nuclear physics, astrophysics, and more. Continua a leggere Origin of Matter and Evolution of Galaxies

Neutron stars at the crossroads

We have witnessed in the last five years the convergence of two fields of astrophysics born half a century ago: the study of neutron stars powered by their rotational energy, and the study of accreting compact objects in X-ray binaries. Recent discoveries have confirmed the evolutionary link between millisecond radio pulsars (MRPs) and low-mass X-ray binaries (LMXBs), and have opened a new era where the “metamorphosis” of a neutron star from a rotation- to an accretion-powered state (and vice versa) can be directly observed. Continua a leggere Neutron stars at the crossroads

The 10° INTEGRAL Workshop “A Synergistic View of the High Energy Sky”

The goal of this workshop is to present and discuss (via invited and contributed talks and posters) the latest results obtained in the field of high-energy astrophysics using the International Gamma-Ray Astrophysics Laboratory INTEGRAL, and place these results in the context of other operational space-based missions, such as Swift, Fermi, AGILE, NuSTAR, and Maxi as well as ground-based VHE observatories. Correlative studies in lower energy bands, as well as neutrino- and gravitational wave observations are included as relevant for various source classes. Continua a leggere The 10° INTEGRAL Workshop “A Synergistic View of the High Energy Sky”

Physics of Neutron Stars

This will be the 10th gathering on neutron star physics in Saint Petersburg (after those in 1988, 1992, 1995, 1997, 1999, 2001, 2005, 2008, and 2011). In 2014 the conference will commemorate the 100th birthday of Yakov Borisovich Zel’dovich (1914—1987), the famous Soviet physicist and astrophysicist. The conference will cover all major topics of observations and theory of neutron stars, including rotation powered pulsars, pulsar emission mechanisms, pulsar wind nebulae, magnetars, isolated cooling neutron stars, central compact objects, accreting X-ray pulsars (particularly, millisecond pulsars), neutron stars in low-mass X-ray binaries, X-ray bursts, equation of state, structure and evolution of neutron stars, mechanisms of supernova explosions and neutron star mergers.

Extreme-Astrophysics in an Ever-Changing Universe

Since ancient times, astronomers’ attention has been drawn to changes in the sky. Today we know that most phenomena observed in “time-domain” astronomy are related to extreme astrophysical events or processes. Whether it is the explosion of stars in supernovae or the observations of flare stars, pulsars, gamma-ray bursts, blazars or active galactic nuclei, time-domain astronomy stretches across the whole electromagnetic spectrum and beyond. With increasing technical capabilities, the 21st century will see corresponding new instruments being developed or coming online, revolutionising our view of the ever-changing Universe. Continua a leggere Extreme-Astrophysics in an Ever-Changing Universe

The X-ray Universe

The XMM-Newton Science Operations Centre is organising a major astrophysical symposium from Monday 16th to Thursday 19th of June 2014 in Dublin, Ireland. The symposium is the fourth international meeting in the series “The X-ray Universe”. The intention is to gather a general collection of research in high energy astrophysics. The symposium will provide a showcase for results, discoveries and expectations from current and future X-ray missions. Continua a leggere The X-ray Universe

The Strong Gravity Regime of Black Holes and Neutron Stars

The 558th WE-Heraeus-Seminar on The Strong Gravity Regime of Black holes and Neutron stars is kindly funded by the Wilhelm und Else Heraeus Foundation. It will be held from March 31st to April 4th, 2014 at the Physikzentrum of the German Physical Society in Bad Honnef near Bonn and Cologne, Germany.

The main theme of this seminar is the observation and theoretical description of systems where gravity is strong and non-linear, in particular systems containing black holes and neutron stars which are ideal gravitational laboratories. To cover the complete complexity of this field of research, experts and graduate students from the observational and theoretical community are invited to bring together their expertise.

As a rough guideline, we have the following categories:

  • Strong-field gravity in GR and its alternatives
  • Black holes as strong field probes
  • Neutron stars as strong field probes
  • Gravitational wave observations and merger events

More info: The Strong Gravity Regime of Black Holes and Neutron Stars

The Structure and Signals of Neutron Stars, from Birth to Death

This conference aims at bringing together people working in astrophysics of neutron stars, both on the theoretical and observational aspects. The following topics will be discussed : – Equation of state of dense matter, including hyperon, kaon and quark degrees of freedom – Neutrino emission and cooling of compact stars – Superconductivity-superfluidity – Constraints from EM observations – Transients – Gravitational wave emission – Models for Supernovae and for Gamma Ray Bursts – Magnetars.

How to ‘listen to’ the birth of black holes?

La partecipazione dell’Australia alla potenziale scoperta delle onde gravitazionali, e quindi alla capacità di “ascoltare” la nascita di un buco nero, riceverà oggi una accelerata. Questo è il giorno in cui i fisici di tutto il continenti australiano si incontreranno all’Australian International Gravitational Research Centre presso Gingin, quasi 100 Km da Perth. L’obiettivo del meeting è quello di lanciare una missione a livello nazionale che abbia lo scopo di espandere la partecipazione dell’Australia ai progetti americani ed europei unendosi così alla ricerca delle elusive perturbazioni dello spaziotempo.

Gravitational waves are ripples in the curvature of spacetime. They are thought to mark the beginning of time at the Big Bang and the end of time as black holes are born. They are generated by extreme cosmic events such as colliding stars and supernova explosions. Theory predicts that they carry vast amounts of energy at the speed of light. While their power can exceed the power of all the stars in the Universe, their effects are miniscule and difficult to detect. Centre Director, The University of Western Australia’s Winthrop Professor David Blair, said 1000 physicists around the world are currently involved in the search which is focused on the commissioning of three enormous supersensitive detectors that will start operating within the next few years in the USA and Europe, with another under construction in Japan. “The expected step in sensitivity will extend their reach tenfold and increase the number of expected signals 1000-fold“, he said. Professor Peter Veitch, Chair of the Australian Consortium for Gravitational Astronomy, said: “The new advanced detectors change the whole game. For the first time we have firm predictions: both the strength and the number of signals. No longer are we hoping for rare and unknown events. We will be monitoring a significant volume of the Universe and for the first time we can be confident that we will ‘listen’ to the coalescence of binary neutron star systems and the formation of black holes. Once these detectors reach full sensitivity we should hear signals almost once a week“. Data from the detectors will be used in conjunction with optical telescopes that will search the sky for visible signs of the catastrophic events signaled by the gravitational waves. Australia is contributing two telescopes to the search: the Zadko telescope at Gingin and the Skymapper telescope at Coonabarrabran in New South Wales. The data from the detectors will be distributed to data analysis teams in many countries. The Australian data analysis team has developed special techniques for digging signals out of the unavoidable noise in the detectors, plus special techniques that use graphics processing units for detecting signals the instant they occur (instead of traditional techniques which can take minutes or hours to identify signals). This fast detection method is especially important if optical telescopes are going to be able to locate distant explosions the moment they occur.

One of the most exciting sources is expected to be the coalescence of pairs of neutron stars to form a black hole, giving out a burst of gamma rays and a flash of light that astronomers call a kilonova.

In this project the Pawsey Centre supercomputers will be equipped with ‘search pipelines’ developed at ANU, Melbourne and UWA. These are massive computer codes designed to separate signals from the noise. Each pipeline is optimised for a specific type of signal, such as the chirps expected as neutron stars spiral together and black holes form. Using these codes, Australian students will be able to play a major role in the first discovery of gravitational waves. The project will be launched at the Gravity Discovery Centre (GDC) by the Chair of GDC Fred Deshon, the Chair of the Gravitational Wave Observatory Development Committee Jens Balkau and the Chair of the Australian Consortium for Gravitational Astronomy Peter Veitch. The GDC which also includes the Gingin Observatory shares the Gingin site with the Australian International Gravitational Research Centre and provides public education on the big questions of the Universe.

UWA: Australian scientists to ‘listen’ to the formation of black holes

Ultra strong magnetic fields in neutron stars

Una serie di simulazioni numeriche mostra per la prima volta che la presenza di instabilità nel nucleo delle stelle di neutroni può determinare la formazione di campi magnetici giganteschi che possono a loro volta causare violente e drammatiche esplosioni stellari mai osservate nell’Universo.

An ultra-dense (“hypermassive”) neutron star is formed when two neutron stars in a binary system finally merge. Its short life ends with the catastrophic collapse to a black hole, possibly powering a short gamma-ray burst, one of the brightest explosions observed in the Universe. Short gamma-ray bursts as observed with satellites like XMM Newton, Fermi or Swift release within a second the same amount of energy as our Galaxy in one year. It has been speculated for a long time that enormous magnetic field strengths, possibly higher than what has been observed in any known astrophysical system, are a key ingredient in explaining such emission.

Scientists at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) have now succeeded in simulating a mechanism which could produce such strong magnetic fields prior to the collapse to a black hole.

How can such ultra-high magnetic fields, stronger than ten or hundred million billion times the Earth’s magnetic field, be generated from the much lower initial neutron star magnetic fields? This could be explained by a phenomenon that can be triggered in a differentially rotating plasma in the presence of magnetic fields: neighbouring plasma layers, which rotate at different speeds, “rub against each other”, eventually setting the plasma into turbulent motion. In this process called magnetorotational instability magnetic fields can be strongly amplified. This mechanism is known to play an important role in many astrophysical systems such as accretion disks and core-collapse supernovae. It had been speculated for a long time that magnetohydrodynamic instabilities in the interior of hypermassive neutron stars could bring about the necessary magnetic field amplification. The actual demonstration that this is possible has only now been achieved with the present numerical simulations. The scientists of the Gravitational Wave Modelling Group at the AEI simulated a hypermassive neutron star with an initially ordered (“poloidal”) magnetic field, whose structure is subsequently made more complex by the star’s rotation. Since the star is dynamically unstable, it eventually collapses to a black hole surrounded by a cloud of matter, until the latter is swallowed by the black hole.

These simulations have unambiguously shown the presence of an exponentially rapid amplification mechanism in the stellar interior, the magnetorotational instability. This mechanism has so far remained essentially unexplored under the extreme conditions of ultra-strong gravity as found in the interior of hypermassive neutron stars.

This is because the physical conditions in the interior of these stars are extremely challenging. The discovery is interesting for at least two reasons. First, it shows for the first time unambiguously the development of the magnetorotational instability in the framework of Einstein’s theory of general relativity, in which there exist no analytical criteria to date to predict the instability. Second, this discovery can have a profound astrophysical impact, supporting the idea that ultra strong magnetic fields can be the key ingredient in explaining the huge amount of energy released by short gamma-ray bursts.

MPI: The largest magnetic fields in the universe

arXiv: Magnetorotational instability in relativistic hypermassive neutron stars