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  • richardmitnick 9:38 am on October 18, 2021 Permalink | Reply
    Tags: "Exploring the mysterious origins of the most extreme light flashes in the universe", ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU), , , , , GRB CDF-S XT1, ,   

    From ARC Centres of Excellence for Gravitational Wave Discovery – OzGrav (AU) via phys.org : “Exploring the mysterious origins of the most extreme light flashes in the universe” 

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    From ARC Centres of Excellence for Gravitational Wave Discovery – OzGrav (AU)

    via

    phys.org

    October 18, 2021

    1
    Artist’s illustration of a gamma ray burst. Credit: Carl Knox, OzGrav-The Swinburne University of Technology (AU).

    Our universe shines bright with light across the electromagnetic spectrum. While most of this light comes from stars like our sun in galaxies like our own, we are often treated with brief and bright flashes that outshine entire galaxies themselves. Some of these brightest flashes are believed to be produced in cataclysmic events, such as the death of massive stars or the collision of two stellar corpses known as neutron stars. Researchers have long studied these bright flashes or “transients” to gain insight into the deaths and afterlives of stars and the evolution of our universe.

    Astronomers are sometimes greeted with transients that defy expectations and puzzle theorists who have long predicted how various transients should look. In October 2014, a long-term monitoring program of the southern sky with the Chandra telescope—NASA’s flagship X-Ray telescope—detected one such enigmatic transient called CDF-S XT1: a bright transient lasting a few thousandths of a second.

    The amount of energy CDF-S XT1 released in X-rays was comparable to the amount of energy the sun emits over a billion years. Ever since the original discovery, astrophysicists have come up with many hypotheses to explain this transient; however, none have been conclusive.

    In a recent study, a team of astrophysicists led by OzGrav postdoctoral fellow Dr. Nikhil Sarin (Monash University (AU)) found that the observations of CDF-S XT1 match predictions of radiation expected from a a high-speed jet traveling close to the speed of light. Such “outflows” can only be produced in extreme astrophysical conditions, such as the disruption of a star as it gets torn apart by a massive black hole, the collapse of a massive star or the collision of two neutron stars.

    Sarin et al’s study found that the outflow from CDF-S XT1 was likely produced by two neutron stars merging together.

    This insight makes CDF-S XT1 similar to the momentous 2017 discovery called GW170817—the first observation of gravitational-waves, cosmic ripples in the fabric of space and time—although CDF-S XT1 is 450 times further away from Earth. This huge distance means that this merger happened very early in the history of the universe; it may also be one of the furthest neutron star mergers ever observed.

    Neutron star collisions are the main places in the universe where heavy elements such as gold, silver and plutonium are created. Since CDF-S XT1 occurred early on in the history of the universe, this discovery advances our understanding of Earth’s chemical abundance and elements.

    Recent observations of another transient AT2020blt in January 2020—primarily with the Zwicky Transient Facility—have puzzled astronomers.

    This transient’s light is like the radiation from high-speed outflows launched during the collapse of a massive star. Such outflows typically produce higher energy gamma-rays; however, they were missing from the data—they were not observed. These gamma rays can only be missing due to one of three reasons: 1) The gamma-rays were not produced, 2) The gamma rays were directed away from Earth, 3) The gamma-rays were too weak to be seen.

    In a separate study [The Astrophysical Journal Letters], led again by OzGrav researcher Dr. Sarin, the Monash University astrophysicists teamed up with researchers in Alabama, Louisiana, Portsmouth and Leicester to show that AT2020blt probably did produce gamma-rays pointed toward Earth, they were just really weak and missed by our current instruments.

    Dr. Sarin says: “Together with other similar transient observations, this interpretation means that we are now starting to understand the enigmatic problem of how gamma-rays are produced in cataclysmic explosions throughout the Universe.”

    The class of bright transients collectively known as gamma-ray bursts, including CDF-S XT1, AT2020blt, and AT2021any, produce enough energy to outshine entire galaxies in just one second.

    “Despite this, the precise mechanism that produces the high-energy radiation we detect from the other side of the universe is not known,” explains Dr. Sarin. “These two studies have explored some of the most extreme gamma-ray bursts ever detected. With further research, we’ll finally be able to answer the question we’ve pondered for decades: How do gamma ray bursts work?”

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    OzGrav (AU)


    ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)
    A new window of discovery.
    A new age of gravitational wave astronomy.
    One hundred years ago, Albert Einstein produced one of the greatest intellectual achievements in physics, the theory of general relativity. In general relativity, spacetime is dynamic. It can be warped into a black hole. Accelerating masses create ripples in spacetime known as gravitational waves (GWs) that carry energy away from the source. Recent advances in detector sensitivity led to the first direct detection of gravitational waves in 2015. This was a landmark achievement in human discovery and heralded the birth of the new field of gravitational wave astronomy. This was followed in 2017 by the first observations of the collision of two neutron-stars. The accompanying explosion was subsequently seen in follow-up observations by telescopes across the globe, and ushered in a new era of multi-messenger astronomy.

    The mission of the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) is to capitalise on the historic first detections of gravitational waves to understand the extreme physics of black holes and warped spacetime, and to inspire the next generation of Australian scientists and engineers through this new window on the Universe.

    OzGrav is funded by the Australian Government through the Australian Research Council Centres of Excellence funding scheme, and is a partnership between Swinburne University of Technology (AU) (host of OzGrav headquarters), the Australian National University (AU), Monash University (AU), University of Adelaide (AU), University of Melbourne (AU), and University of Western Australia (AU), along with other collaborating organisations in Australia and overseas.
    ________________________________________________________

    The objectives for the ARC Centres of Excellence are to:

    undertake highly innovative and potentially transformational research that aims to achieve international standing in the fields of research envisaged and leads to a significant advancement of capabilities and knowledge

    link existing Australian research strengths and build critical mass with new capacity for interdisciplinary, collaborative approaches to address the most challenging and significant research problems

    develope relationships and build new networks with major national and international centres and research programs to help strengthen research, achieve global competitiveness and gain recognition for Australian research

    build Australia’s human capacity in a range of research areas by attracting and retaining, from within Australia and abroad, researchers of high international standing as well as the most promising research students

    provide high-quality postgraduate and postdoctoral training environments for the next generation of researchers

    offer Australian researchers opportunities to work on large-scale problems over long periods of time

    establish Centres that have an impact on the wider community through interaction with higher education institutes, governments, industry and the private and non-profit sector.

     
  • richardmitnick 10:55 am on September 13, 2021 Permalink | Reply
    Tags: "New research takes us closer to figuring out supermassive black holes", ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU), , , ,   

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU) : “New research takes us closer to figuring out supermassive black holes” 

    arc-centers-of-excellence-bloc

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)

    13/9/2021

    Galaxies host supermassive black holes, which weigh millions to billions times more than our Sun.

    When galaxies collide, pairs of supermassive black holes at their centres also lie on the collision course. It may take millions of years before two black holes slam into each other. When the distance between them is small enough, the black hole binary starts to produce ripples in space-time, which are called gravitational waves.

    Gravitational waves were first observed in 2015, but they were detected from much smaller black holes, which weigh like tens times our Sun. Gravitational waves from supermassive black holes are still a mystery to scientists. Their discovery would be invaluable to figuring out how galaxies and stars form and evolve, and finding the origin of dark matter.

    A recent study [The Astrophysical Journal Letters], led by Dr Boris Goncharov and Prof Ryan Shannon—both researchers from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav)—has tried to solve this puzzle. Using the most recent data from the Australian experiment known as the Parkes Pulsar Timing Array, the team of scientists searched for these mystery gravitational waves from supermassive black holes.

    The experiment observed radio pulsars: extremely dense collapsed cores of massive supergiant stars (called neutron stars) that pulse out radio waves, like a lighthouse beam.

    The timing of these pulses is extremely precise, whereas the background of gravitational waves advances and delays pulse arrival times in a predicted pattern across the sky, by around the same amount in all pulsars. The researchers now found that arrival times of these radio waves do show deviations with similar properties as we expect from gravitational waves However, more data is needed to conclude whether radio wave arrival times are correlated in all pulsars across the sky, which is considered the “smoking gun”. Similar results have also been obtained by collaborations based in North America and Europe.

    Caltech/MIT Advanced aLigo at Hanford, WA(US), Livingston, LA(US) and VIRGO Gravitational Wave interferometer, near Pisa(IT).

    These collaborations, along with groups based in India, China, and South Africa, are actively combining datasets under the International Pulsar Timing Array, to improve the sky coverage.

    IPTA-International Pulsar Timing Array

    2
    Constraints on inter-pulsar correlations obtained by Goncharov et al. (2021), as red probability contours, and the expected spatial correlation that would have been produced by the gravitational-wave signal from an ensemble of supermassive black hole binaries.

    This discovery is considered a precursor to the detection of gravitational waves from supermassive blackholes. However, Dr Goncharov and colleagues pointed out that the observed variations in the radio wave arrival times might also be due to ipulsar-intrinsic noise. Dr Goncharov said: “To find out if the observed “common” drift has a gravitational wave origin, or if the gravitational-wave signal is deeper in the noise, we must continue working with new data from a growing number of pulsar timing arrays across the world”.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    OzGrav (AU)


    ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)
    A new window of discovery.
    A new age of gravitational wave astronomy.
    One hundred years ago, Albert Einstein produced one of the greatest intellectual achievements in physics, the theory of general relativity. In general relativity, spacetime is dynamic. It can be warped into a black hole. Accelerating masses create ripples in spacetime known as gravitational waves (GWs) that carry energy away from the source. Recent advances in detector sensitivity led to the first direct detection of gravitational waves in 2015. This was a landmark achievement in human discovery and heralded the birth of the new field of gravitational wave astronomy. This was followed in 2017 by the first observations of the collision of two neutron-stars. The accompanying explosion was subsequently seen in follow-up observations by telescopes across the globe, and ushered in a new era of multi-messenger astronomy.

    The mission of the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) is to capitalise on the historic first detections of gravitational waves to understand the extreme physics of black holes and warped spacetime, and to inspire the next generation of Australian scientists and engineers through this new window on the Universe.

    OzGrav is funded by the Australian Government through the Australian Research Council Centres of Excellence funding scheme, and is a partnership between Swinburne University of Technology (AU) (host of OzGrav headquarters), the ustralian National University (AU), Monash University (AU), University of Adelaide (AU), University of Melbourne (AU), and University of Western Australia (AU), along with other collaborating organisations in Australia and overseas.
    ________________________________________________________

    The objectives for the ARC Centres of Excellence are to to:

    undertake highly innovative and potentially transformational research that aims to achieve international standing in the fields of research envisaged and leads to a significant advancement of capabilities and knowledge

    link existing Australian research strengths and build critical mass with new capacity for interdisciplinary, collaborative approaches to address the most challenging and significant research problems

    develope relationships and build new networks with major national and international centres and research programs to help strengthen research, achieve global competitiveness and gain recognition for Australian research

    build Australia’s human capacity in a range of research areas by attracting and retaining, from within Australia and abroad, researchers of high international standing as well as the most promising research students

    provide high-quality postgraduate and postdoctoral training environments for the next generation of researchers

    offer Australian researchers opportunities to work on large-scale problems over long periods of time

    establish Centres that have an impact on the wider community through interaction with higher education institutes, governments, industry and the private and non-profit sector.

     
  • richardmitnick 11:00 pm on June 8, 2021 Permalink | Reply
    Tags: "Research highlight- bright cosmic explosions could reveal strange interstellar 'knot'", ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU), , , , Gamma-ray bursts are enormous cosmic explosions and are one of the brightest and most energetic events in the Universe., , , The recently observed gamma-ray burst event called GRB 160203A.,   

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU) : “Research highlight- bright cosmic explosions could reveal strange interstellar ‘knot'” 

    arc-centers-of-excellence-bloc

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)

    8/6/2021
    Hayden Crisp, University of Western Australia (AU)

    1
    Shells of material surround the stars of Eta Carinae. A Gamma-ray burst coming from those stars should release large amounts of light as it collides with the denser medium. Image credit: X-ray: National Aeronautics Space Agency (US)/Chandra X-ray Center (US); Ultraviolet/Optical: NASA/Space Telescope Science Institute (US); Combined Image: NASA/European Space Agency [Agence spatiale européenne][Europäische Weltraumorganisation](EU)/N. Smith (University of Arizona (US)), J. Morse (BoldlyGo Institute) and A. Pagan.

    Gamma-ray bursts are enormous cosmic explosions and are one of the brightest and most energetic events in the Universe. Their brightness changes over time, illuminating deep space like a flashlight shining into a dark room. Intense radiation emitted from most observed gamma-ray bursts is predicted to be released during a supernova as a star implodes to form a neutron star or a black hole.

    In the recently observed gamma-ray burst event called GRB 160203A, remains of the explosion started glowing much brighter than expected, according to standard scientific models, even several hours after the initial flash. We now believe that this “rebrightening” was caused by the main body of the burst crashing through shells of material ejected by the source star, or interstellar “knots”. Both theories suggest that the standard gamma-ray burst model needs to be re-examined, and perhaps the surrounding space isn’t as smooth and uniform as originally predicted.

    In our study [MNRAS], we began collecting reports from all over the world that observed the gamma-ray burst event, including the archives of the Zadko research telescope.

    By carefully calibrating the data from different sources and comparing the different brightness over time, we unpacked the surrounding galaxy and defined key characteristics of the burst: the temporal index (how quickly it fades over time), the spectral index (the overall colour of the burst), and the extinction (how much light is absorbed by the matter between here, on Earth, and the burst). One surprising finding was that the density of the burst’s host galaxy is unusually dense – about the same as our own galaxy, the Milky Way.

    The next step was to see how and when the data moved away from the model. With further calculations, we identified three interesting time periods that indicated significant brightness differences compared to the model’s prediction. Although the third period was probably a coincidence, the first and second periods were too large to ignore. Normally, rebrightening is caused by something happening to the host galaxy(?), such as suddenly collapsing into a black hole; however, these kinds of events normally happen within the first few minutes of a gamma-ray burst – in this event, the first rebrightening didn’t start until three hours after the initial explosion.

    As a result, we decided to expand the conventional model of gamma-ray bursts to explain this unusual event. One of the properties of such events is the relationship between the density of the medium and the intensity of radiation emitted from the explosion. What’s particularly convincing about this explanation is its applicability to many contexts. As stars prepare to explode into supernovas and gamma-ray bursts, they eject their outer shells into the surrounding space. For bursts that don’t come from supernovas, these changes in brightness could be the result of turbulence in the interstellar medium. In either case, the change in brightness gives us a new tool to probe the structure of distant space, and we are now eagerly anticipating another burst with similar features to put our new model to the test.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    OzGrav (AU)


    ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)
    A new window of discovery.
    A new age of gravitational wave astronomy.
    One hundred years ago, Albert Einstein produced one of the greatest intellectual achievements in physics, the theory of general relativity. In general relativity, spacetime is dynamic. It can be warped into a black hole. Accelerating masses create ripples in spacetime known as gravitational waves (GWs) that carry energy away from the source. Recent advances in detector sensitivity led to the first direct detection of gravitational waves in 2015. This was a landmark achievement in human discovery and heralded the birth of the new field of gravitational wave astronomy. This was followed in 2017 by the first observations of the collision of two neutron-stars. The accompanying explosion was subsequently seen in follow-up observations by telescopes across the globe, and ushered in a new era of multi-messenger astronomy.

    The mission of the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) is to capitalise on the historic first detections of gravitational waves to understand the extreme physics of black holes and warped spacetime, and to inspire the next generation of Australian scientists and engineers through this new window on the Universe.

    OzGrav is funded by the Australian Government through the Australian Research Council Centres of Excellence funding scheme, and is a partnership between Swinburne University of Technology (AU) (host of OzGrav headquarters), the ustralian National University (AU), Monash University (AU), University of Adelaide (AU), University of Melbourne (AU), and University of Western Australia (AU), along with other collaborating organisations in Australia and overseas.
    ________________________________________________________

    The objectives for the ARC Centres of Excellence are to to:

    undertake highly innovative and potentially transformational research that aims to achieve international standing in the fields of research envisaged and leads to a significant advancement of capabilities and knowledge

    link existing Australian research strengths and build critical mass with new capacity for interdisciplinary, collaborative approaches to address the most challenging and significant research problems

    develope relationships and build new networks with major national and international centres and research programs to help strengthen research, achieve global competitiveness and gain recognition for Australian research

    build Australia’s human capacity in a range of research areas by attracting and retaining, from within Australia and abroad, researchers of high international standing as well as the most promising research students

    provide high-quality postgraduate and postdoctoral training environments for the next generation of researchers

    offer Australian researchers opportunities to work on large-scale problems over long periods of time

    establish Centres that have an impact on the wider community through interaction with higher education institutes, governments, industry and the private and non-profit sector.

     
  • richardmitnick 10:07 am on June 7, 2021 Permalink | Reply
    Tags: "Blistering stars in the Universe- Rare insights into the evolution of stars", ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU), , , , , Most of these massive stars are found in binary systems where two stars closely orbit each other., Supernova explosions are the dramatic deaths of massive stars that are about 8 times heavier than our Sun., What happens if a supernova explosion goes off right beside another star?   

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU) : “Blistering stars in the Universe- Rare insights into the evolution of stars” 

    arc-centers-of-excellence-bloc

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)

    7/6/2021

    1
    Artist’s impression of a supernova. Credit: James Josephides/Swinburne University of Technology (AU).

    What happens if a supernova explosion goes off right beside another star? The star swells up which scientists predict as a frequent occurrence in the Universe. Supernova explosions are the dramatic deaths of massive stars that are about 8 times heavier than our Sun.

    Most of these massive stars are found in binary systems where two stars closely orbit each other, so many supernovae occur in binaries. The presence of a companion star can also greatly influence how stars evolve and explode. For this reason, astronomers have long been searching for companion stars after supernovae– a handful have been discovered over the past few decades and some were found to have unusually low temperatures.

    When a star explodes in a binary system, the debris from the explosion violently strikes the companion star. Usually there’s not enough energy to damage the whole star, but it heats up the star’s surface instead. The heat then causes the star to swell up, like having a huge burn blister on your skin. This star blister can be 10 to 100 times larger than the star itself.

    The swollen star appears very bright and cool, which might explain why some discovered companion stars had low temperatures. Its inflated state only lasts for an ‘astronomically’ short while–after a few years or decades, the blister can “heal” and the star shrinks back to its original form.

    In their recently published study [MNRAS] by a team of scientists led by OzGrav postdoctoral researcher Dr Ryosuke Hirai (Monash University (AU)), the team carried out hundreds of computer simulations to investigate how companion stars inflate, or swell up, depending on its interaction with a nearby supernova. It was found that the luminosity of inflated stars is only correlated to its mass and doesn’t depend on the strength of the interaction with supernova. The duration of the swelling is also longer when the two stars are closer in distance.

    “We applied our results to a supernova called SN2006jc, which has a companion star with a low-temperature. If this is in fact an inflated star as we believe, we expect it should rapidly shrink in the next few years,” explains Hirai.

    The number of companion stars detected after supernovae are steadily growing over the years. If scientists can observe an inflated companion star and its contraction, these data correlations can measure the properties of the binary system before the explosion—these insights are extremely rare and important for understanding how massive stars evolve.

    “We think it’s important to not only find companion stars after supernovae, but to monitor them for a few years to decades to see if it shrinks back,” says Hirai.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    OzGrav (AU)


    ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)
    A new window of discovery.
    A new age of gravitational wave astronomy.
    One hundred years ago, Albert Einstein produced one of the greatest intellectual achievements in physics, the theory of general relativity. In general relativity, spacetime is dynamic. It can be warped into a black hole. Accelerating masses create ripples in spacetime known as gravitational waves (GWs) that carry energy away from the source. Recent advances in detector sensitivity led to the first direct detection of gravitational waves in 2015. This was a landmark achievement in human discovery and heralded the birth of the new field of gravitational wave astronomy. This was followed in 2017 by the first observations of the collision of two neutron-stars. The accompanying explosion was subsequently seen in follow-up observations by telescopes across the globe, and ushered in a new era of multi-messenger astronomy.

    The mission of the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) is to capitalise on the historic first detections of gravitational waves to understand the extreme physics of black holes and warped spacetime, and to inspire the next generation of Australian scientists and engineers through this new window on the Universe.

    OzGrav is funded by the Australian Government through the Australian Research Council Centres of Excellence funding scheme, and is a partnership between Swinburne University of Technology (AU) (host of OzGrav headquarters), the ustralian National University (AU), Monash University (AU), University of Adelaide (AU), University of Melbourne (AU), and University of Western Australia (AU), along with other collaborating organisations in Australia and overseas.
    ________________________________________________________

    The objectives for the ARC Centres of Excellence are to to:

    undertake highly innovative and potentially transformational research that aims to achieve international standing in the fields of research envisaged and leads to a significant advancement of capabilities and knowledge

    link existing Australian research strengths and build critical mass with new capacity for interdisciplinary, collaborative approaches to address the most challenging and significant research problems

    develope relationships and build new networks with major national and international centres and research programs to help strengthen research, achieve global competitiveness and gain recognition for Australian research

    build Australia’s human capacity in a range of research areas by attracting and retaining, from within Australia and abroad, researchers of high international standing as well as the most promising research students

    provide high-quality postgraduate and postdoctoral training environments for the next generation of researchers

    offer Australian researchers opportunities to work on large-scale problems over long periods of time

    establish Centres that have an impact on the wider community through interaction with higher education institutes, governments, industry and the private and non-profit sector.

     
  • richardmitnick 10:03 pm on May 26, 2021 Permalink | Reply
    Tags: "Deciphering the Lives of Double Neutron Stars Using the Ripples in the Fabric of Space and Time", ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU), , , , , , ,   

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU) via SciTechDaily : “Deciphering the Lives of Double Neutron Stars Using the Ripples in the Fabric of Space and Time” 

    arc-centers-of-excellence-bloc

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)

    via

    SciTechDaily

    “Deciphering the Lives of Double Neutron Stars Using the Ripples in the Fabric of Space and Time”

    May 26, 2021

    Scientists from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) have described a way to determine the birth population of double neutron stars — some of the densest objects in the Universe formed in collapsing massive stars. The recently published study observed different life stages of these neutron star systems.

    Scientists can observe the merging of double neutron star systems using gravitational waves — ripples in the fabric of space and time. By studying neutron star populations, scientists can learn more about how they formed and evolved. So far, there have been only two double neutron star systems detected by gravitational-wave detectors; however, many of them have been observed in radio astronomy.

    One of the double neutron stars observed in gravitational wave signals, called GW190425, is far more massive than the ones in typical Galactic populations observed in radio astronomy, with a combined mass of 3.4 times that of our Sun. This raises the question: why is there a lack of these massive double neutron stars in radio astronomy? To find an answer, OzGrav PhD student Shanika Galaudage, from Monash University (AU), investigated how to combine radio and gravitational-wave observations.

    The birth, mid-life and death of double neutron stars

    Radio and gravitational-wave astronomy enables scientists to study double neutron stars at different stages of their evolution. Radio observations probe the lives of double neutron stars, while gravitational waves study their final moments of life. To achieve a better understanding of these systems, from formation to merger, scientists need to study the connection between radio and gravitational wave populations: their birth populations.

    Shanika and her team determined the birth mass distribution of double neutron stars using radio and gravitational-wave observations. “Both populations evolve from the birth populations of these systems, so if we look back in time when considering the radio and gravitational-wave populations we see today, we should be able to extract the birth distribution,” says Shanika Galaudage.

    The key is to understand the delay-time distribution of double neutron stars: the time between the formation and merger of these systems. The researchers hypothesised that heavier double neutron star systems may be fast-merging systems, meaning that they’re merging too fast to be visible in radio observations and could only be seen in gravitational-waves.

    GW190425 and the fast-merging channel

    The study [The Astrophysical Journal Letters] found mild support for a fast-merging channel, indicating that heavy double neutron star systems may not need a fast-merging scenario to explain the lack of observations in radio populations. “We find that GW190425 is not an outlier when compared to the broader population of double neutron stars,” says study co-author Christian Adamcewicz, from Monash University. “So, these systems may be rare, but they‘re not necessarily indicative of a separate fast-merging population.”

    In future gravitational wave detections, researchers can expect to observe more double neutron star mergers. “If future detections reveal a stronger discrepancy between the radio and gravitational-wave populations, our model provides a natural explanation for why such massive double neutron stars are not common in radio populations,” adds co-author Dr Simon Stevenson, an OzGrav postdoctoral researcher at Swinburne University of Technology (AU).

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    OzGrav (AU)


    ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)
    A new window of discovery.
    A new age of gravitational wave astronomy.
    One hundred years ago, Albert Einstein produced one of the greatest intellectual achievements in physics, the theory of general relativity. In general relativity, spacetime is dynamic. It can be warped into a black hole. Accelerating masses create ripples in spacetime known as gravitational waves (GWs) that carry energy away from the source. Recent advances in detector sensitivity led to the first direct detection of gravitational waves in 2015. This was a landmark achievement in human discovery and heralded the birth of the new field of gravitational wave astronomy. This was followed in 2017 by the first observations of the collision of two neutron-stars. The accompanying explosion was subsequently seen in follow-up observations by telescopes across the globe, and ushered in a new era of multi-messenger astronomy.

    The mission of the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) is to capitalise on the historic first detections of gravitational waves to understand the extreme physics of black holes and warped spacetime, and to inspire the next generation of Australian scientists and engineers through this new window on the Universe.

    OzGrav is funded by the Australian Government through the Australian Research Council Centres of Excellence funding scheme, and is a partnership between Swinburne University of Technology (AU) (host of OzGrav headquarters), the ustralian National University (AU), Monash University (AU), University of Adelaide (AU), University of Melbourne (AU), and University of Western Australia (AU), along with other collaborating organisations in Australia and overseas.
    ________________________________________________________

    The objectives for the ARC Centres of Excellence are to to:

    undertake highly innovative and potentially transformational research that aims to achieve international standing in the fields of research envisaged and leads to a significant advancement of capabilities and knowledge

    link existing Australian research strengths and build critical mass with new capacity for interdisciplinary, collaborative approaches to address the most challenging and significant research problems

    develope relationships and build new networks with major national and international centres and research programs to help strengthen research, achieve global competitiveness and gain recognition for Australian research

    build Australia’s human capacity in a range of research areas by attracting and retaining, from within Australia and abroad, researchers of high international standing as well as the most promising research students

    provide high-quality postgraduate and postdoctoral training environments for the next generation of researchers

    offer Australian researchers opportunities to work on large-scale problems over long periods of time

    establish Centres that have an impact on the wider community through interaction with higher education institutes, governments, industry and the private and non-profit sector.

     
  • richardmitnick 4:28 pm on May 4, 2021 Permalink | Reply
    Tags: "Gravitational-wave scientists propose new method to refine the Hubble Constant—the expansion and age of the Universe", ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU), ,   

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU) : “Gravitational-wave scientists propose new method to refine the Hubble Constant—the expansion and age of the Universe” 

    arc-centers-of-excellence-bloc

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)

    4/5/2021

    1
    Artist’s illustration of a pair of merging neutron stars. Credit: Carl Knox, OzGrav-Swinburne University (AU)

    A team of international scientists, led by the Galician Institute of High Energy Physics (IGFAE) at University of Santiago de Compostela [Universidade de Santiago de Compostela] (ES) and the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), has proposed a simple and novel method to bring the accuracy of the Hubble constant measurements down to 2%, using a single observation of a pair of merging neutron stars.

    The Universe is in continuous expansion. Because of this, distant objects such as galaxies move away from us. In fact, the further away they are, the faster they move. Scientists describe this expansion through a famous number known as the Hubble constant, which tells us how fast objects in the Universe recede from us depending on their distance to us. By measuring the Hubble constant in a precise way, we can also determine some of the most fundamental properties of the Universe, including its age.

    For decades, scientists have measured Hubble’s constant with increasing accuracy, collecting electromagnetic signals emitted throughout the Universe but arriving at a challenging result: the two current best measurements give inconsistent results. Since 2015, scientists have tried to tackle this challenge with the science of gravitational waves: ripples in the fabric of space-time that travel at the speed of light. Gravitational waves are generated in the most violent cosmic events and provide a new channel of information about the Universe. They’re emitted during the collision of two neutron stars—the dense cores of collapsed stars–and can help scientists dig deeper into the Hubble constant mystery.

    Unlike black holes, merging neutron stars produce both gravitational and electromagnetic waves, such as x-rays, radio waves and visible light. While gravitational waves can measure the distance between the neutron-star merger and Earth, electromagnetic waves can measure how fast its whole galaxy is moving away from Earth. This creates a new way to measure the Hubble constant. However, even with the help of gravitational waves, it’s still tricky to measure the distance to neutron-star mergers–that’s, in part, why current gravitational-wave based measurements of the Hubble constant have an uncertainty of ~16%, much larger than existing measurements using other traditional techniques.

    In a recently published article in the prestigious journal The Astrophysical Journal Letters, a team of scientists led by ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) and Monash University (AU) alumni Prof Juan Calderón Bustillo (now La Caixa Junior Leader and Marie Curie Fellow at the Galician institute of High Energy Physics of the University of Santiago de Compostela, Spain), has proposed a simple and novel method to bring the accuracy of these measurements down to 2% using a single observation of a pair of merging neutron stars.

    According to Prof Calderón Bustillo, it’s difficult to interpret how far away these mergers occur because ‘currently, we can’t say if the binary is very far away and facing Earth, or if it’s much closer, with the Earth in its orbital plane’. To decide between these two scenarios, the team proposed to study secondary, much weaker components of the gravitational-wave signals emitted by neutron-star mergers, known as higher modes. ‘Just like an orchestra plays different instruments, neutron-star mergers emit gravitational waves through different modes,’ explains Prof Calderón Bustillo. ‘When the merging neutron stars are facing you, you will only hear the loudest instrument. However, if you are close to the merger’s orbital plane, you should also hear the secondary ones. This allows us to determine the inclination of the neutron-star merger, and better measure the distance’.

    However, the method is not completely new: “We know this works well for the case of very massive black hole mergers because our current detectors can record the merger instant when the higher modes are most prominent. But in the case of neutron stars, the pitch of the merger signal is so high that our detectors can’t record it. We can only record the earlier orbits,” says Prof Calderón Bustillo.

    Future gravitational-wave detectors, like the proposed Australian project NEMO, will be able to access the actual merger stage of neutron stars. “When two neutron stars merge, the nuclear physics governing their matter can cause very rich signals that, if detected, could allow us to know exactly where the Earth sits with respect to the orbital plane of the merger,” says co-author and OzGrav Chief Investigator Dr Paul Lasky, from Monash University. Dr Lasky is also one of the leads on the NEMO project. ‘A detector like NEMO could detect these rich signals,’ he adds.

    In their study, the team performed computer simulations of neutron-star mergers that can reveal the effect of the nuclear physics of the stars on the gravitational waves. Studying these simulations, the team determined that a detector like NEMO could measure Hubble’s constant with a precision of 2%.

    Co-author of the study Prof Tim Dietrich, from the University of Potsdam [Universität Potsdam](DE), says: “We found that fine details describing the way neutrons behave inside the star produce subtle signatures in the gravitational waves that can greatly help to determine the expansion rate of the Universe. It is fascinating to see how effects at the tiniest nuclear scale can infer what happens at the largest possible cosmological one”.

    Samson Leong, undergraduate student at the Chinese University of Hong Kong [香港中文大学] (HK) and co-author of the study points out “one of the most exciting things about our result is that we obtained such a great improvement while considering a rather conservative scenario. While NEMO will indeed be sensitive to the emission of neutron-star mergers, more evolved detectors like Einstein Telescope or Cosmic Explorer will be even more sensitive, therefore allowing us to measure the expansion of the Universe with even better accuracy!”.

    One of the most outstanding implications of this study is that it could determine if the Universe is expanding uniformly in space as currently hypothesised. ‘Previous methods to achieve this level of accuracy rely on combining many observations, assuming that the Hubble constant is the same in all directions and throughout the history of the Universe,’ says Calderón Bustillo. ‘In our case, each individual event would yield a very accurate estimate of “its own Hubble constant”, allowing us to test if this is actually a constant or if it varies throughout space and time.’

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    OzGrav (AU)


    ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)
    A new window of discovery.
    A new age of gravitational wave astronomy.
    One hundred years ago, Albert Einstein produced one of the greatest intellectual achievements in physics, the theory of general relativity. In general relativity, spacetime is dynamic. It can be warped into a black hole. Accelerating masses create ripples in spacetime known as gravitational waves (GWs) that carry energy away from the source. Recent advances in detector sensitivity led to the first direct detection of gravitational waves in 2015. This was a landmark achievement in human discovery and heralded the birth of the new field of gravitational wave astronomy. This was followed in 2017 by the first observations of the collision of two neutron-stars. The accompanying explosion was subsequently seen in follow-up observations by telescopes across the globe, and ushered in a new era of multi-messenger astronomy.

    The mission of the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) is to capitalise on the historic first detections of gravitational waves to understand the extreme physics of black holes and warped spacetime, and to inspire the next generation of Australian scientists and engineers through this new window on the Universe.

    OzGrav is funded by the Australian Government through the Australian Research Council Centres of Excellence funding scheme, and is a partnership between Swinburne University of Technology (AU) (host of OzGrav headquarters), the Australian National University (AU), Monash University (AU), University of Adelaide (AU), University of Melbourne (AU), and University of Western Australia (AU), along with other collaborating organisations in Australia and overseas.
    ________________________________________________________

    The objectives for the ARC Centres of Excellence are to to:

    undertake highly innovative and potentially transformational research that aims to achieve international standing in the fields of research envisaged and leads to a significant advancement of capabilities and knowledge

    link existing Australian research strengths and build critical mass with new capacity for interdisciplinary, collaborative approaches to address the most challenging and significant research problems

    develope relationships and build new networks with major national and international centres and research programs to help strengthen research, achieve global competitiveness and gain recognition for Australian research

    build Australia’s human capacity in a range of research areas by attracting and retaining, from within Australia and abroad, researchers of high international standing as well as the most promising research students

    provide high-quality postgraduate and postdoctoral training environments for the next generation of researchers

    offer Australian researchers opportunities to work on large-scale problems over long periods of time

    establish Centres that have an impact on the wider community through interaction with higher education institutes, governments, industry and the private and non-profit sector.

     
  • richardmitnick 2:34 pm on May 3, 2021 Permalink | Reply
    Tags: "Deep space listening: 6000 hours of research to hear continuous gravitational waves", ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)   

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU) : “Deep space listening: 6000 hours of research to hear continuous gravitational waves” 

    arc-centers-of-excellence-bloc

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)

    3/5/2021 [JUst now in social media.]

    1
    Rapidly rotating neutron stars may be “humming” continuous gravitational waves. Credit: K. Wette.

    Remember the days before working from home? It’s Monday morning, you’re running late to beat the traffic, and you can’t find your car keys. What do you do? You might try moving from room to room, casting your eye over every flat surface, in the hope of spotting the missing keys. Of course, this assumes that they are somewhere in plain sight; if they’re hidden under a newspaper, or fallen behind the sofa, you’ll never spot them. Or you might be so convinced that you last saw the keys in the kitchen and search for them there: inside every cupboard, the microwave, dishwasher, back of the fridge, etc. Of course, if you left them on your bedside table, upending the kitchen is doomed to failure. So, which is the best strategy?

    Scientists face a similar conundrum in the hunt for gravitational waves—ripples in the fabric of space and time—from rapidly spinning neutron stars. These stars are the densest objects in the Universe and, provided they’re not perfectly spherical, emit a very faint “hum” of continuous gravitational waves. Hearing this “hum” would allow scientists to peer deep inside a neutron star and discover its secrets, yielding new insights into the most extreme states of matter. However, our very sensitive “ears”—4-kilometre-sized detectors using powerful lasers—haven’t heard anything yet.

    Part of the challenge is that, like the missing keys, scientists aren’t sure of the best search strategy. Most previous studies have taken the “room-to-room” approach, trying to find continuous gravitational waves in as many different places as possible. But this means you can only spend a limited amount of time listening for the tell-tale “hum” in any one location—in the same way that you can only spend so long staring at your coffee table, trying to discern a key-shaped object. And since the “hum” is very quiet, there’s a good chance you won’t even hear it.

    In a recently published study [Physical Review D], a team of scientists, led by postdoctoral researcher Karl Wette from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) at the Australian National University (AU), tried the “where else could they be but the kitchen?” approach.

    Wette explains: “We took an educated guess at a specific location where continuous gravitational waves might be, based in part on what we already know about pulsars—they’re like neutron stars but send out radio waves instead of continuous gravitational waves. We hypothesised that there would be continuous gravitational waves detected near pulsar radio waves.” Just like guessing that your missing keys will probably be close to your handbag or wallet.

    Using existing observational data, the team spent a lot of time searching in this location (nearly 6000 days of computer time!) listening carefully for that faint “hum”. They also used graphic processing units—specialist electronics normally used for computer games—making their algorithms run super-fast.

    “Our search was significantly more sensitive than any previous search for this location,” says Wette. “Unfortunately, we didn’t hear anything, so our guess was wrong this time. It’s back to the drawing board for now, but we’ll keep listening.”

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    OzGrav (AU)


    ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)
    A new window of discovery.
    A new age of gravitational wave astronomy.
    One hundred years ago, Albert Einstein produced one of the greatest intellectual achievements in physics, the theory of general relativity. In general relativity, spacetime is dynamic. It can be warped into a black hole. Accelerating masses create ripples in spacetime known as gravitational waves (GWs) that carry energy away from the source. Recent advances in detector sensitivity led to the first direct detection of gravitational waves in 2015. This was a landmark achievement in human discovery and heralded the birth of the new field of gravitational wave astronomy. This was followed in 2017 by the first observations of the collision of two neutron-stars. The accompanying explosion was subsequently seen in follow-up observations by telescopes across the globe, and ushered in a new era of multi-messenger astronomy.

    The mission of the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) is to capitalise on the historic first detections of gravitational waves to understand the extreme physics of black holes and warped spacetime, and to inspire the next generation of Australian scientists and engineers through this new window on the Universe.

    OzGrav is funded by the Australian Government through the Australian Research Council Centres of Excellence funding scheme, and is a partnership between Swinburne University of Technology (AU) (host of OzGrav headquarters), the Australian National University (AU), Monash University (AU), University of Adelaide (AU), University of Melbourne (AU), and University of Western Australia (AU), along with other collaborating organisations in Australia and overseas.
    ________________________________________________________

    The objectives for the ARC Centres of Excellence are to to:

    undertake highly innovative and potentially transformational research that aims to achieve international standing in the fields of research envisaged and leads to a significant advancement of capabilities and knowledge

    link existing Australian research strengths and build critical mass with new capacity for interdisciplinary, collaborative approaches to address the most challenging and significant research problems

    develope relationships and build new networks with major national and international centres and research programs to help strengthen research, achieve global competitiveness and gain recognition for Australian research

    build Australia’s human capacity in a range of research areas by attracting and retaining, from within Australia and abroad, researchers of high international standing as well as the most promising research students

    provide high-quality postgraduate and postdoctoral training environments for the next generation of researchers

    offer Australian researchers opportunities to work on large-scale problems over long periods of time

    establish Centres that have an impact on the wider community through interaction with higher education institutes, governments, industry and the private and non-profit sector.

     
  • richardmitnick 11:33 pm on April 26, 2021 Permalink | Reply
    Tags: "THE EXOTIC LIVES OF BOSON STARS", ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU), , , ,   

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU) : “THE EXOTIC LIVES OF BOSON STARS” 

    arc-centers-of-excellence-bloc

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)

    16/3/2021 [Just now in social media.]
    1
    A non-rotating black hole, a rotating black hole and a boson star as they’d appear to the Event Horizon Telescope. Unlike black holes, boson stars would be transparent as they lack an absorbing surface to stop photons, and do not have an event horizon. Credit: Olivares et al., MNRAS, 2020.

    There are some stars that just don’t look at all like stars. Rather than being composed nearly entirely of hydrogen and helium like other stars, they consist of matter that has no electromagnetic signature. These stars are hypothetical because we’re still refining the techniques to find them.

    Boson stars are just one in this family of objects, known as exotic stars, and they’re composed almost entirely of bosons. And what is a boson? It’s one of the two types of fundamental particles, the one that carries forces. The other, the fermion, is what makes up ‘normal’ stars, and all the other matter that we see.

    There are a variety of boson stars and sometimes they’re categorised to reflect the type of boson that they are made of. For example, Proca stars are vector boson stars, meaning that their constituent bosons have a spin of one. They’re also unique amongst boson stars because the stars themselves can spin without being disrupted.

    A boson star would most likely be shaped like an enormous donut because of the centrifugal forces acting on the bosonic matter, and, bizarrely, they’d be transparent; any matter absorbed by them would be visible at their centres. If boson stars do exist, they might provide the evidence we need for a long sought-after dark matter particle. That’s because the said particle, the axion, is a boson. And we’ve been searching (unsuccessfully) for axions in numerous experiments on Earth for decades.

    After the initial excitement of the first-ever observation of an intermediate-mass black hole—gravitational-wave event GW190521—it was quickly realised that the very existence of such an object was not consistent with any of our stellar models. Perhaps it was itself a product of previous, smaller, black hole collisions, or maybe there was something else at play.

    Thus, the challenge for scientists was to come up with a theory that could explain the presence of the intermediate-mass black hole progenitor of GW190521, while still being consistent with the original signal. And by assuming that it was caused by merging boson stars, rather than black holes, an international team of scientists, led by OzGrav alumnus Dr Juan Calderón Bustillo at the University of Santiago de Compostela – USC [Universidade de Santiago de Compostela](ES) and Dr Nicolás Sanchis-Gual at the University of Lisbon [Universidade de Lisboa] (PT), might have been able to do just that.

    Apart from the problems associated with the pair-instability mass gap, any potential hypothesis needed to explain something a bit unusual about the GW190521 signal. Normally gravitational waves that originate in merging binary systems oscillate at higher and higher frequencies as the two progenitors spiral in towards each other. But for GW190521, the inspiral signal before the merger was barely detectable. An extremely abbreviated inspiral could perhaps be explained if two black holes collided head-on rather than by circling into each other, and so that is the first thing that Dr Bustillo and Dr Sanchis-Gual’s team looked at. What they found didn’t help much.

    “We first tried to fit the data to head-on collisions of black holes, but these happen to produce a final black hole whose spin is too low to reproduce the GW190521 signal. The reason is that the lack of an inspiral diminishes a lot of the spin of the final black hole, and the individual spins of the black holes, which also contribute to the spin of the final one, are bounded by a limit called the Kerr limit,” says Dr Bustillo.

    That’s when the team started looking at boson stars, or Proca stars to be exact. They compared the GW190521 signal to computer simulations of Proca star mergers and found that statistically they were a considerably better fit to the data than when it was assumed that the progenitors were black holes.

    “First, we would not be talking about colliding black holes anymore, which eliminates the issue of dealing with a forbidden black hole, explains Dr Bustillo. Second, because boson star mergers are much weaker, we infer a much closer distance than the one estimated by LIGO and Virgo. This leads to a much larger mass for the final black hole, of about 250 solar masses, so the fact that we have witnessed the formation of an intermediate-mass black hole remains true.”

    This is an exciting result as the final black hole formed by the merger in this case would have to be about 62% larger than previously thought. And rather than the signal originating from a point that is now some 17-billion light-years from us, it would have been just over 1.8-billion light-years away.

    “Of course, there are potentially many ways in which this event may be explained, as this is an event for which we have very little information about what produced the final black hole we observe. The best we can say right now is that the data tells us that a collision of Proca stars is approximately 8 times more likely than the black hole collision scenario.”

    And what of the implications of discovering the first boson stars?

    “That would be dramatic, says Dr Bustillo. Boson stars and their building blocks—the ultralight bosons—are one of the most solid candidates for forming what we know as dark matter. If our result is further confirmed by future observations, it would represent the first actual measurement of the particle responsible for dark matter.”

    “Gravitational-wave astronomy is still very much in its infancy,” says Dr Rory Smith—an OzGrav researcher from Monash University (AU) and one of the collaborators in this research. “However, the fact that we’re already starting to draw connections between gravitational-wave observations and fundamental particle physics is a remarkable sign of how powerful this new field is. Even if future observations rule out boson stars as real astronomical objects, we should expect many new and exciting discoveries in the future.”

    Science papers:
    Physical Review Letters

    MNRAS

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    OzGrav (AU)


    ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)
    A new window of discovery.
    A new age of gravitational wave astronomy.
    One hundred years ago, Albert Einstein produced one of the greatest intellectual achievements in physics, the theory of general relativity. In general relativity, spacetime is dynamic. It can be warped into a black hole. Accelerating masses create ripples in spacetime known as gravitational waves (GWs) that carry energy away from the source. Recent advances in detector sensitivity led to the first direct detection of gravitational waves in 2015. This was a landmark achievement in human discovery and heralded the birth of the new field of gravitational wave astronomy. This was followed in 2017 by the first observations of the collision of two neutron-stars. The accompanying explosion was subsequently seen in follow-up observations by telescopes across the globe, and ushered in a new era of multi-messenger astronomy.

    The mission of the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) is to capitalise on the historic first detections of gravitational waves to understand the extreme physics of black holes and warped spacetime, and to inspire the next generation of Australian scientists and engineers through this new window on the Universe.

    OzGrav is funded by the Australian Government through the Australian Research Council Centres of Excellence funding scheme, and is a partnership between Swinburne University of Technology (AU) (host of OzGrav headquarters), the Australian National University (AU), Monash University (AU), University of Adelaide (AU), University of Melbourne (AU), and University of Western Australia (AU), along with other collaborating organisations in Australia and overseas.
    ________________________________________________________

    The objectives for the ARC Centres of Excellence are to to:

    undertake highly innovative and potentially transformational research that aims to achieve international standing in the fields of research envisaged and leads to a significant advancement of capabilities and knowledge

    link existing Australian research strengths and build critical mass with new capacity for interdisciplinary, collaborative approaches to address the most challenging and significant research problems

    develope relationships and build new networks with major national and international centres and research programs to help strengthen research, achieve global competitiveness and gain recognition for Australian research

    build Australia’s human capacity in a range of research areas by attracting and retaining, from within Australia and abroad, researchers of high international standing as well as the most promising research students

    provide high-quality postgraduate and postdoctoral training environments for the next generation of researchers

    offer Australian researchers opportunities to work on large-scale problems over long periods of time

    establish Centres that have an impact on the wider community through interaction with higher education institutes, governments, industry and the private and non-profit sector.

     
  • richardmitnick 10:58 pm on April 26, 2021 Permalink | Reply
    Tags: "Deciphering the lives of double neutron stars in radio and gravitational wave astronomy", ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU), , , Caltech MIT Advanced aLIGO(US), , GW190425,   

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU) : “Deciphering the lives of double neutron stars in radio and gravitational wave astronomy” 

    arc-centers-of-excellence-bloc

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)

    26/4/2021

    1
    Artist’s now iconic illustration of a double neutron star merger. Credit: A. Simonnet Caltech MIT Advanced aLIGO(US), Sonoma State University (US).

    Scientists from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) have described a way to determine the birth population of double neutron stars–some of the densest objects in the Universe formed in collapsing massive stars. The recently published study [The Astrophysical Journal Letters] observed different life stages of these neutron star systems.

    Scientists can observe the merging of double neutron star systems using gravitational waves–ripples in the fabric of space and time. By studying neutron star populations, scientists can learn more about how they formed and evolved. So far, there have been only two double neutron star systems detected by gravitational-wave detectors; however, many of them have been observed in radio astronomy.

    One of the double neutron stars observed in gravitational wave signals, called GW190425, is far more massive than the ones in typical Galactic populations observed in radio astronomy, with a combined mass of 3.4 times that of our Sun.

    This raises the question: why is there a lack of these massive double neutron stars in radio astronomy? To find an answer, OzGrav PhD student Shanika Galaudage, from Monash University (AU), investigated how to combine radio and gravitational-wave observations.

    The birth, mid-life and deaths of double neutron stars.

    Radio and gravitational-wave astronomy enables scientists to study double neutron stars at different stages of their evolution. Radio observations probe the lives of double neutron stars, while gravitational waves study their final moments of life. To achieve a better understanding of these systems, from formation to merger, scientists need to study the connection between radio and gravitational wave populations: their birth populations.

    Shanika and her team determined the birth mass distribution of double neutron stars using radio and gravitational-wave observations. “Both populations evolve from the birth populations of these systems, so if we look back in time when considering the radio and gravitational-wave populations we see today, we should be able to extract the birth distribution,” says Shanika Galaudage.

    The key is to understand the delay-time distribution of double neutron stars: the time between the formation and merger of these systems. The researchers hypothesised that heavier double neutron star systems may be fast-merging systems, meaning that they’re merging too fast to be visible in radio observations and could only be seen in gravitational-waves.

    GW190425 and the fast-merging channel.

    The study found mild support for a fast-merging channel, indicating that heavy double neutron star systems may not need a fast-merging scenario to explain the lack of observations in radio populations. “We find that GW190425 is not an outlier when compared to the broader population of double neutron stars,” says study co-author Christian Adamcewicz, from Monash University. “So, these systems may be rare, but they‘re not necessarily indicative of a separate fast-merging population.”

    In future gravitational wave detections, researchers can expect to observe more double neutron star mergers. “If future detections reveal a stronger discrepancy between the radio and gravitational-wave populations, our model provides a natural explanation for why such massive double neutron stars are not common in radio populations,” adds co-author Dr Simon Stevenson, an OzGrav postdoctoral researcher at Swinburne University of Technology (AU).

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    OzGrav (AU)


    ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)
    A new window of discovery.
    A new age of gravitational wave astronomy.
    One hundred years ago, Albert Einstein produced one of the greatest intellectual achievements in physics, the theory of general relativity. In general relativity, spacetime is dynamic. It can be warped into a black hole. Accelerating masses create ripples in spacetime known as gravitational waves (GWs) that carry energy away from the source. Recent advances in detector sensitivity led to the first direct detection of gravitational waves in 2015. This was a landmark achievement in human discovery and heralded the birth of the new field of gravitational wave astronomy. This was followed in 2017 by the first observations of the collision of two neutron-stars. The accompanying explosion was subsequently seen in follow-up observations by telescopes across the globe, and ushered in a new era of multi-messenger astronomy.

    The mission of the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) is to capitalise on the historic first detections of gravitational waves to understand the extreme physics of black holes and warped spacetime, and to inspire the next generation of Australian scientists and engineers through this new window on the Universe.

    OzGrav is funded by the Australian Government through the Australian Research Council Centres of Excellence funding scheme, and is a partnership between Swinburne University of Technology (AU) (host of OzGrav headquarters), the Australian National University (AU), Monash University (AU), University of Adelaide (AU), University of Melbourne (AU), and University of Western Australia (AU), along with other collaborating organisations in Australia and overseas.
    ________________________________________________________

    The objectives for the ARC Centres of Excellence are to to:

    undertake highly innovative and potentially transformational research that aims to achieve international standing in the fields of research envisaged and leads to a significant advancement of capabilities and knowledge

    link existing Australian research strengths and build critical mass with new capacity for interdisciplinary, collaborative approaches to address the most challenging and significant research problems

    develope relationships and build new networks with major national and international centres and research programs to help strengthen research, achieve global competitiveness and gain recognition for Australian research

    build Australia’s human capacity in a range of research areas by attracting and retaining, from within Australia and abroad, researchers of high international standing as well as the most promising research students

    provide high-quality postgraduate and postdoctoral training environments for the next generation of researchers

    offer Australian researchers opportunities to work on large-scale problems over long periods of time

    establish Centres that have an impact on the wider community through interaction with higher education institutes, governments, industry and the private and non-profit sector.

     
  • richardmitnick 8:45 pm on April 20, 2021 Permalink | Reply
    Tags: "Testing Einstein's theory of gravity from the shadows and collisions of black holes":, ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU), , , , , , , The Event Horizon Telescope (EHT) collaboration   

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU) via phys.org : “Testing Einstein’s theory of gravity from the shadows and collisions of black holes” 

    arc-centers-of-excellence-bloc

    From ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)

    via

    phys.org

    1
    Artist’s impression of binary black holes about to collide. Credit: Mark Myers, OzGrav-Swinburne University of Technology (AU).

    General relativity, Einstein’s theory of gravity, is best tested at its most extreme—close to the event horizon of a black hole. This regime is accessible through observations of shadows of supermassive black holes and gravitational waves—ripples in the fabric of our Universe from colliding stellar-mass black holes. For the first time, scientists from the ARC Center of Excellence for Gravitational Wave Discovery (OzGrav), the Event Horizon Telescope (EHT) and the Caltech MIT Advanced aLIGO(US), have outlined a consistent approach to exploring deviations from Einstein’s general theory of relativity in these two different observations. This research, published in Physical Review D, confirms that Einstein’s theory accurately describes current observations of black holes, from the smallest to the largest.

    One of the hallmark predictions from general relativity is the existence of black holes.The theory provides a specific description of a black hole’s effect on the fabric of space-time: a four-dimensional mesh which encodes how objects move through space and time. Known as the Kerr metric, this prediction can be related to the bending of light around a black hole, or the orbital motion of binary black holes. In this study, the deviations from the Kerr metric were linked to features in these black hole observations.

    In 2019, the Event Horizon Telescope generated silhouette images of the black hole at the center of the galaxy M87, with a mass several billion times that of our Sun.

    The first image of the event horizon of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration released on 10 April 2019 Messier 87*, via National Science Foundation(US)

    The angular size of the shadow is related to the mass of the black hole, its distance from Earth and possible deviations from general relativity’s prediction. These deviations can be calculated from the scientific data, including previous measurements of the black hole’s mass and distance.

    Meanwhile, since 2015 the LIGO and Virgo gravitational-wave observatories have been detecting gravitational waves from merging stellar mass black holes. By measuring the gravitational waves from the colliding black holes, scientists can explore the mysterious nature and metrics of the black holes. This study focussed on deviations from general relativity that appear as slight changes to the pitch and intensity of the gravitational waves, before the two black holes collide and merge.

    Combining the measurements of the shadow of the supermassive black hole in M87 and gravitational waves from a couple of binary black hole detections, called GW170608 and GW190924, the researchers found no evidence for deviations from general relativity. Co-author of the study and OzGrav research assistant Ethan Payne (Australian National University) explained that the two measurements provided similar, consistent constraints. “Different sizes of black holes may help break the complementary behavior seen here between EHT and LIGO/Virgo observations,” said Payne. “This study lays the groundwork for future measurements of deviations from the Kerr metric.”

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    OzGrav (AU)


    ARC Centres of Excellence for Gravitational Wave Discovery OzGrav (AU)
    A new window of discovery.
    A new age of gravitational wave astronomy.
    One hundred years ago, Albert Einstein produced one of the greatest intellectual achievements in physics, the theory of general relativity. In general relativity, spacetime is dynamic. It can be warped into a black hole. Accelerating masses create ripples in spacetime known as gravitational waves (GWs) that carry energy away from the source. Recent advances in detector sensitivity led to the first direct detection of gravitational waves in 2015. This was a landmark achievement in human discovery and heralded the birth of the new field of gravitational wave astronomy. This was followed in 2017 by the first observations of the collision of two neutron-stars. The accompanying explosion was subsequently seen in follow-up observations by telescopes across the globe, and ushered in a new era of multi-messenger astronomy.

    The mission of the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) is to capitalise on the historic first detections of gravitational waves to understand the extreme physics of black holes and warped spacetime, and to inspire the next generation of Australian scientists and engineers through this new window on the Universe.

    OzGrav is funded by the Australian Government through the Australian Research Council Centres of Excellence funding scheme, and is a partnership between Swinburne University of Technology (AU) (host of OzGrav headquarters), the Australian National University (AU), Monash University (AU), University of Adelaide (AU), University of Melbourne (AU), and University of Western Australia (AU), along with other collaborating organisations in Australia and overseas.

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    The objectives for the ARC Centres of Excellence are to to:

    undertake highly innovative and potentially transformational research that aims to achieve international standing in the fields of research envisaged and leads to a significant advancement of capabilities and knowledge

    link existing Australian research strengths and build critical mass with new capacity for interdisciplinary, collaborative approaches to address the most challenging and significant research problems

    develope relationships and build new networks with major national and international centres and research programs to help strengthen research, achieve global competitiveness and gain recognition for Australian research

    build Australia’s human capacity in a range of research areas by attracting and retaining, from within Australia and abroad, researchers of high international standing as well as the most promising research students

    provide high-quality postgraduate and postdoctoral training environments for the next generation of researchers

    offer Australian researchers opportunities to work on large-scale problems over long periods of time

    establish Centres that have an impact on the wider community through interaction with higher education institutes, governments, industry and the private and non-profit sector.

     
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