2024-11-15

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2024-10-28

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2024-08-28

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2024-07-24

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2024-04-05

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2024-04-01

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A team of astronomers collaborating with LVK scientists has used data from two major NASA missions to search systematically for other gamma-ray signals which could be associated with the GW events found in the LIGO-Virgo O3 observing run.

2023-08-31

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This is the latest and most sensitive search for continuous gravitational waves (CWs) from the low-mass X-ray binary Scorpius X-1, a neutron star in a binary orbit with a low-mass star. We did not detect gravitational waves from Scorpius X-1, but set limits which are beginning to constrain possible models.

2023-04-25

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We expect that as they travel cosmological distances, gravitational waves will inevitably encounter massive astrophysical objects that would act as lenses, bending their trajectories and even distorting the shapes of their signals. In this study, we have searched for the still undetected lensing signatures in the gravitational-wave signals detected in our latest LIGO-Virgo-KAGRA catalog, which includes events from the full third observing run (O3).

2023-04-18

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The LIGO–Virgo–KAGRA Collaboration (LVK) has committed to the principles of open science. This article provides a thorough description of the latest major data set publicly released on the Gravitational Wave Open Science Center (GWOSC), associated with the third observing run, O3, that took place from April 1 2019 to April 21 2020.

2023-03-27

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Advanced LIGO and Advanced Virgo have found a plethora of signals that are likely produced by the gravitational waves emitted during the coalescence of binaries of compact objects (black holes and neutron stars). Most of the black holes routinely observed in this way are usually between ten and one hundred times the mass of our Sun.

2022-12-06

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Neutron stars are dense, neutron-rich stars left behind by the aftermath of a supernova explosion. They usually weigh a little bit more than the sun, but are only about 10-20 kilometers across. A small percentage of these neutron stars have an exceptionally strong magnetic field — about a trillion times that of the sun — and we call these “magnetars”.

2022-11-17

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According to astronomical observations, the region near the centre of the Milky Way, our Galaxy, is a very active and densely populated place. In particular, space telescopes like Fermi-LAT have measured an excess of energy, in the form of high-energy electromagnetic radiation, coming from that particular region of the sky.

2022-04-12

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Fast Radio Bursts (FRBs) are bright, millisecond duration radio bursts that are so bright we can see them from billions of light years away. Since their discovery over a decade ago, the sources of FRBs are still unknown, and although there have been hints to the origin, remain one of the outstanding questions in astronomy.

2022-03-22

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KAGRA is a new gravitational-wave (GW) detector in Japan that has recently joined the international network of detectors, along with Advanced LIGO and Advanced Virgo as of October 2019. KAGRA planned to start joint observation with Advanced LIGO and Advanced Virgo in the last month (April) of the third Observing Run (O3) in 2020.

2022-03-03

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The gravitational wave signals detected thus far by the LVK collaboration detectors arise from mergers of heavy astronomical objects, such as black holes or neutron stars. However, this is not the only type of gravitational waves that can be observed.

2022-1-27

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Since 2015, we have had a new way of studying the Universe by means of the direct detection of gravitational waves (GWs). To date, 90 GW events have been registered by the Advanced LIGO and Advanced Virgo interferometers.

2022-01-05

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Neutron stars are remnants of supernovae, the explosions of massive stars, and they are the densest objects in the universe after black holes. They have a mass of 1.4 times the mass of our sun or more, but a radius of only about 10 km! They have magnetic fields that can be between one hundred million and one quadrillion (one million times one billion) times stronger than the Earth’s magnetic field.

2021-12-21

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Gravitational wave scientists have several favorite potential sources of continuous signals and often revisit them when probing new data sets. Those favorites include familiar pulsars like the Crab and Vela, objects for which the rotational frequencies and how those evolve are known well because they are monitored by electromagnetic astronomers.

2021-12-01

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Since the first detection of gravitational waves in 2015, we have observed a multitude of gravitational wave events. What all these events have in common is that they are transient signals from merging compact objects.

2021-12-01

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The mysterious dark matter exists all around us and yet is invisible to us. Such dark matter could be composed of extremely light particles known as bosons, each having a mass of approximately 10-47 kg (that’s a number with 46 zeros after the decimal point, followed by a single “one”).

2021-11-30

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GWTC-3 is the third Gravitational-Wave Transient Catalog from LIGO, Virgo, and KAGRA. GWTC-3 updates our previous catalogs with gravitational-wave observations from the second part of Observing Run 3 (imaginatively called O3b), which lasted from November 2019 to March 2020.

2021-11-07

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The Advanced LIGO, Advanced Virgo and KAGRA detectors are sensitive to gravitational waves (GW) from all directions. They have observed signals from various compact object mergers, combinations of black holes and neutron stars.

2021-10-27

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LIGO and Virgo have now detected many pairs of large black holes (BHs) from the gravitational waves generated as they spiral together and merge, but can we also see very small black holes this way?

2021-09-28

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Spinning neutron stars are prime targets in the hunt for continuous gravitational waves (GWs). Unlike the GWs that have been observed so far, continuous GWs are long-lasting signals that should appear in our detector data all the time; the challenge is to find them.

2021-09-20

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We present an updated catalog of gravitational wave (GW) candidates from data gathered by the LIGO and Virgo detectors during the first half of the third observing run (O3a). This update, called GWTC-2.1 (Gravitational Wave Transient Catalog 2.1), corresponds to the same observing period as GWTC-2, starting from 1 April 2019 and ending 1 October 2019, but includes candidate events with a lower statistical significance to aid with multi-messenger searches, and takes advantage of improvements in the data processing and analysis methods.

2021-08-02

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While our knowledge of the population of compact binary mergers continues to grow with already 50 objects released in the GWTC-2 catalog, there remain many other possible sources of yet-to-be-detected gravitational waves (GWs).

2021-07-30

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The third observing run (O3) of the Advanced LIGO and Advanced Virgo detectors ended in March 2020. During O3 several tens of Gravitational Waves (GWs) have been confirmed, originating from the compact binary coalescence (CBC) of Black Holes and/or Neutron Stars.

2021-07-09

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LIGO and Virgo scientists have been waging a decades-long campaign to find unsightly bulges on neutron stars. Neutron stars are highly compact stars that are created in the collapse of a star heavier than our Sun as the electrons in its atoms combine with the protons to form a ball of mostly neutrons of radius not much greater than 10 km.

2021-07-01

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On January 5th 2020 the Advanced LIGO detector in Livingston, Louisiana in the US and the Advanced Virgo detector in Italy observed gravitational waves consistent with an entirely new type of astronomical system. The gravitational waves were produced by the death spiral of two of the most extreme objects in the Universe: one, a neutron star, and the other a black hole.

2021-06-29

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The search for intermediate-mass black holes (IMBHs) has been a focus of astronomers’ attention for many years. The Advanced LIGO and Advanced Virgo detectors completed their first two observing runs (O1 and O2) between 2015 and 2017, and no significant detections of IMBH mergers were made. The first half of our third observing run (O3) marked the first confirmed detection of an IMBH remnant in a binary system: GW190521, a discovery which we announced in 2020.

2021-05-31

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Dark matter makes up 85% of the total matter in the Universe, but it is completely invisible to us. And yet, we can measure its effects on a variety of celestial objects: it roams around each galaxy and prevents stars from flying out of their orbits, it changes the directions of light rays from far-away galaxies, it guides the formation of the large-scale structures of the Universe, and it has even left imprints in the cosmic microwave background, the farthest and oldest photograph of the Universe, taken when it was only a few hundred thousand years old.

2021-03-27

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Core-collapse supernovae are the violent, explosive deaths of massive stars. The remnant of the explosion is an ultra-dense neutron star surrounded by debris from the explosion (Fig. 1).

2021-05-26

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Imagine a magnifying glass as big as a galaxy and what it will do to light or gravitational waves traveling through the cosmos. Through the phenomenon of “gravitational lensing”, massive astrophysical objects can act as such giant lenses.

2021-05-13

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PSR J0537-6910, also known as “The Big Glitcher”, is a very special pulsar, which draws lots of attention from astronomers. Pulsars are rapidly-rotating neutron stars, which are the collapsed cores of massive stars. These objects are extreme in many ways.

2021-04-30

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The universe we live in is expanding. This makes distant galaxies and other objects recede from us. The Hubble constant is one of the fundamental numbers describing the universe as we see it today.

2021-03-19

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Since the first gravitational wave detection, of the binary black-hole merger GW150914, the LIGO-Virgo detector network has observed gravitational waves from many binary black hole mergers and a couple of binary neutron star mergers. However, these events represent only a small fraction of the total number of binary black hole and binary neutron star mergers happening in the universe.

2021-03-16

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The Universe is expanding and steadily cooling down. This process may lead to the creation of cosmic strings: these are one-dimensional topological defects, the energy of which is concentrated along a line.

2021-02-01

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The Cosmic Microwave Background (CMB) has provided us with information on the origin of the Universe since it is the oldest electromagnetic radiation we can measure. Similarly, there exists a Gravitational Wave Background (GWB) which is a superposition of gravitational waves generated by different astrophysical and cosmological sources, and can go even further back in time than the CMB, due to the weak coupling of gravitational waves (GWs) and matter.

2021-02-01

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Neutron stars (NSs) are the outcome of a supernova explosion, the remnant of a former star with a mass between 10 and 25 times the mass of the Sun. These compact objects have a typical radius of 10km and a mass similar to that of our Sun, making NSs one of the most extreme environments in which matter has ever been observed.

2020-12-25

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Pulsars are rapidly-rotating neutron stars, which are the collapsed cores of massive stars. They are extreme objects, more massive than the Sun yet no larger than a large city.

2020-12-25

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We present an updated catalog (GWTC-2 or the “Gravitational-Wave Transient Catalog 2”) of gravitational-wave detections by LIGO and Virgo from the very first observation in 2015 to the end of O3a, the first half of the third observing period.

2020-10-28

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On May 21, 2019, the Advanced LIGO and Advanced Virgo detectors observed a gravitational-wave signal from the merger of an extraordinary pair of black holes. The signal, named GW190521, was shorter in duration, and peaked at lower frequency, than any other binary black hole merger observed to date.

2020-09-02

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Gravitational waves (GWs) from binary black hole and binary neutron star systems have been responsible for the new discoveries made with gravitational-wave detectors. But inspiraling binaries are not the only way to make GWs: other promising sources include rotating neutron stars.

2020-07-29

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On August 14, 2019, exactly two years to the day since the first ever three-detector observation of a gravitational wave signal (GW170814), the two Advanced LIGO detectors in the US, at Hanford, Washington and Livingston, Louisiana, and the Advanced Virgo detector in Cascina, Italy, observed another gravitational wave signal from what is perhaps an even more intriguing source.

2020-06-23

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Supplement:

• Measuring Cosmic Expansion with Dark Standard Siren GW190814
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A previous paper published by the LIGO and Virgo collaborations described a search for continuous gravitational waves from a neutron star called Scorpius X-1. This paper improves on that work in two ways: firstly, by analyzing data from the Laser Interferometer Gravitational-wave Observatory’s (LIGO’s) second observing run, O2 (which ran for a longer period and was slightly more sensitive), and secondly, by using a refined search filter (the J-statistic), capable of more precisely picking out signals from sources like Scorpius X-1 from noisy detector data.

2020-05-27

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On April 12, 2019, the LIGO Scientific Collaboration and Virgo Collaboration observed gravitational waves produced by the inspiral and merger of two black holes.

2020-04-20

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Since 2015, Advanced LIGO and Virgo detectors have demonstrated their capacity to detect gravitational waves from the inspiral and merger of two compact objects, which include neutron stars and black holes. These discoveries have been recently summarized in a first catalog, GWTC-1.

2020-03-04

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Once a gravitational wave has been detected by the LIGO and Virgo interferometers, one of the questions that can be asked is: did the same source also emit other signals, such as a flash of light (electromagnetic radiation) or a burst of neutrinos? The observation and study of an astrophysical event via multiple kinds of signals is called multimessenger astronomy and is a major research effort.

2020-03-02

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Gravitational waves are extraordinarily small ripples in the fabric of spacetime that stretch and squeeze space by a minuscule amount as they pass. The two Advanced LIGO detectors in the U.S. and the Advanced Virgo detector in Italy measure this strain, or relative change in length, by observing the interference of laser light that travels several kilometers down perpendicular interferometer arms and back.

2020-01-08

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The LIGO Scientific Collaboration and Virgo Collaboration can report that, on 25th April, 2019, gravitational waves were detected from the merger of two compact objects. Our collaborations designated this signal as GW190425.

2020-01-06

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Core-Collapse Supernovae (CCSNe) are spectacular deaths of massive stars with masses larger than 8 times the mass of our Sun (or, 8 solar masses). These stars burn hydrogen in their cores over millions or billions of years, in the process creating heavier elements up to iron.

2019-12-20

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During the first and the second observing run of the Advanced LIGO and Advanced Virgo detectors, ten binary black hole (BBH) mergers were detected (these mergers are reported in the catalog of compact binary mergers GWTC-1). These detectors are sensitive only to the final stages of the BBH coalescence (up to the last few hundred orbits, depending upon the mass of the binary components), where the signal’s frequency falls in the detectors’ sensitive band.

2019-11-29

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With the first detection of gravitational waves from the merger of two neutron stars by LIGO and Virgo (GW170817) and the detection of the merger’s electromagnetic counterpart, we have entered a very exciting era in gravitational wave astronomy and neutron star astrophysics.

2019-11-29

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Gamma-ray bursts (GRBs) are the brilliant flashes of high-energy light that arise from the universe’s most energetic stellar death events. These phenomena, which erupt in an initial bright flash and then glow for many months, occur at the end of life for certain exotic astronomical bodies.

2019-10-14

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Stars generate energy through nuclear fusion, and the energy released creates an outward pressure that counteracts the inward force due to gravity. When the star burns through all of its fuel, the pressure generated from nuclear fusion is no longer able to counterbalance the gravitational force, leading to gravitational collapse.

2019-10-14

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The discovery of the binary neutron star merger GW170817 has already made a substantial impact on our understanding of astrophysics, cosmology, and fundamental physics. This event has two notable features that make it stand out compared to previous gravitational-wave detections by LIGO and Virgo.

2019-10-14

PDFs: [en] [de]

Gravitational waves are extraordinarily small ripples in the fabric of spacetime that stretch and squeeze space by a minuscule amount as they pass. The two Advanced LIGO detectors in the U.S. and the Advanced Virgo detector in Italy measure this strain, or relative change in length, by observing the interference of laser light that travels several kilometers down perpendicular interferometer arms and back.

2019-08-30

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Binary mergers are not the only detectable sources of gravitational waves. Another important possibility is emission from asymmetric isolated neutron stars.

2019-08-19

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The gravitational waves which have been detected so far by LIGO-Virgo are caused by merging objects that are either black holes or neutron stars. Most detected events involved two black holes, but one detection, called GW170817, was likely caused by the coalescence of two neutron stars instead.

2019-08-12

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The first observation of a binary neutron star merger taught us a lot about the most extreme matter in the universe, but in the long run continuous gravitational waves from neutron stars (which need not be in binaries) can teach us more.

2019-08-07

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At the conclusion of the second Observing run (O2), Advanced LIGO and Advanced Virgo had detected gravitational waves from ten binary black hole mergers, and one binary neutron star merger. Black hole and neutron star mergers are not the only predicted sources of gravitational waves.

2019-07-12

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The advanced LIGO and Virgo detectors have completed two observing runs between 2015 and 2018. To date, ten binary black hole merger events have been observed.

2019-06-21

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The effort to observe gravitational waves was crowned with success in September 2015 when LIGO detected a signal emitted by the coalescence, and subsequent collision, of a pair of black holes. More gravitational wave events have since been observed by the Advanced LIGO and Advanced Virgo detectors.

2019-05-28

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LIGO’s first detection of a binary black hole merger, GW150914, opened a gravitational-wave window on the Universe. We are now able to resolve tiny ripples in space and time coming from far away galaxies and explore the frontiers of physics. Nine black hole merger detections have followed, and, so far, LIGO and its partner detector, Virgo, have made one detection of a binary neutron star merger in 2017.

2019-05-28

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There have now been a host of gravitational-wave signals detected from merging compact objects. However, the signals from these have all been transient and were only observable in the LIGO and Virgo detectors for short durations before they merged (tens of seconds for the binary neutron star merger, or seconds, or less, for the binary black hole systems.)

2019-05-28

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In addition to binary-black-hole mergers like GW150914 and GW170814, and binary-neutron-star mergers like GW170817, LIGO may detect other sources of GWs such as supernovae, pulsars, or even the stochastic gravitational-wave background from the Big Bang. In the next few years, a larger world-wide network of GW detectors will join LIGO and Virgo in their search for a wide-range of yet undetected astrophysical phenomena offering strong potential for new science.

2019-04-01

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Einstein’s theory of General Relativity has passed a large number of tests in the over 100 years since its conception. The observation of gravitational waves emitted by two coalescing black holes was one of the most anticipated discoveries in the history of General Relativity, and Einstein was proven right again.

2019-03-12

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We have now observed gravitational waves from some of the loudest events in the Universe. But what is happening with gravitational waves from the quieter events?

2019-03-08

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Magnetars are a type of neutron star characterized by extremely strong magnetic fields—up to a hundred billion Tesla (see Figure 1 for an artist’s impression). Astronomers have identified about 20 magnetars in the Milky Way galaxy.

2019-03-08

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We present a new catalog (known as GWTC-1 or “Gravitational-Wave Transient Catalog 1”) of gravitational-wave sources discovered during the first and second observing runs of the global network of Advanced gravitational-wave detectors.

2018-12-03

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A number of sources are expected to produce transient gravitational waves on a “long” timescale (i.e. a few seconds to several minutes), and we are looking for them! Some of the astrophysical phenomena expected to emit such gravitational waves include matter asymmetrically falling into a newborn neutron star, clumps of matter in the accretion disk of a spinning black hole, and slight deformations on magnetar surfaces.

2018-11-09

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During their lifetime, stars shine by generating energy through nuclear fusion. This release of energy creates an outwards pressure that counterbalances the inward force due to gravity.

2018-10-30

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Cosmic strings are hypothetical one-dimensional objects that may have formed in the early Universe, while it was cooling down and expanding. They are analogous to the cracks that form when water freezes; as the early Universe cooled, space-time could have ‘cracked’ (the technical term for these ‘cracks’ is topological [*] defect) causing cosmic strings to form.

2018-10-30

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A century ago, Einstein revolutionized our understanding of gravity with his general theory of relativity, which explains gravitational attraction as the curvature of spacetime around massive objects. It could be the case, however, that general relativity is only an approximation of a more complete theory of gravity, much like Newtonian gravity was an approximation of Einstein’s theory.

2018-06-04

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Einstein’s general relativity is our most successful theory of space, time, and gravity. According to this elegant framework, the force of gravity is a manifestation of the curvature of spacetime, which is itself produced by the presence of matter or energy. In the words of legendary physicist John Wheeler, “spacetime tells matter how to move; matter tells spacetime how to curve” (source).

2018-06-04

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During the first two observing runs of the Advanced LIGO and Advanced Virgo detectors, gravitational-wave signals from several binary black hole mergers and a binary neutron star merger have been detected (click here to learn more). This important achievement has given us the ability to study astrophysical objects in a completely new way, through gravitational-wave astronomy.

2018-06-04

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In 2016 the first direct detections of gravitational-wave signals were announced by the LIGO Scientific Collaboration and Virgo Collaboration. So far, the signals detected by the Advanced LIGO and Advanced Virgo detectors were all due to transient signals emitted by the collision and merger of compact binary systems comprising pairs of black holes or neutron stars.

2018-06-04

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In 2016 we set out our plans for observing the gravitational-wave sky with LIGO and Virgo. Things have gone pretty well! It has been a busy start to observing with our new detectors. We have announced our first gravitational-wave detections, won a Nobel Prize, and had our first gravitational-wave signal from a binary neutron star system.

2018-03-16

PDF: [en]

Gravitational waves (GWs) are ripples in the gravitational field, predicted to exist by Einstein’s General Theory of Relativity. A neutron star is the extremely dense remnant of the core of a massive star. Born in a supernova explosion, neutron stars are some of the most interesting objects in the universe.

2018-03-05

PDF: [en]

In 2016 the first direct detections of gravitational-wave signals were announced by the LIGO Scientific Collaboration and Virgo Collaboration. So far, the signals detected by the Advanced LIGO and Advanced Virgo detectors were all due to transient signals emitted by the collision and merger of compact binary systems comprising pairs of black holes or neutron stars.

2018-03-05

PDF: [en]

The detected signal which comprised the first direct detection of gravitational waves lasted around two-tenths of a second. However, these short, transient signals are far from the only type of gravitational waves that can be searched for. This publication is about a search for what are known as continuous gravitational waves.

2018-03-05

PDF: [en]

Gravitational waves (GWs) are ripples in the gravitational field, predicted to exist by Einstein’s General Theory of Relativity. A neutron star is the extremely dense remnant of the core of a massive star. Born in a supernova explosion, neutron stars are some of the most interesting objects in the universe.

2018-03-05

PDF: [en]

During the second observation run (O2) of the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO), gravitational waves were detected on June 8, 2017 at 02:01:16 UTC, in the evening of June 7, 2017 in North America. This signal, known as GW170608, comes from the spiraling together and collision of two black holes and was detected by both the LIGO detectors in Livingston, Louisiana and Hanford, Washington.

2017-11-15

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On 17 August 2017, at 12:41:04 UTC (8:41:04am EDT in North America, and 2:41:04pm CEST in Europe) the LIGO-Virgo gravitational wave detector network registered a gravitational wave signal from the inspiral of two compact stellar remnants known as “neutron stars.” This event came just three days after the first joint LIGO-Virgo detection of a binary black hole merger, GW170814 (see that science summary).

2017-10-16

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The GW170814 event is the fourth confirmed detection of gravitational waves reported by the LIGO Scientific Collaboration and Virgo Collaboration. The signal comes from a coalescing pair of stellar-mass black holes, and is the first to be observed by the Advanced Virgo detector.

2017-09-27

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We report the most sensitive search to date for continuous gravitational waves from Scorpius X-1, a neutron star in a binary orbit with a low-mass star.

2017-06-18

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In September 2015 the twin advanced detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) made the first ever direct detection of gravitational waves from the merger of two massive black holes more than a billion light years away.

2017-06-01

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On September 14, 2015, LIGO made the first detection of gravitational waves, a signal known as GW150914. This signal was generated by two black holes, with masses 36 and 29 times the mass of the sun, which orbited each other and then merged into a single black hole with mass 62 times the mass of the sun.

2017-06-01

PDF: [en]

A Core-Collapse Supernova (CCSN) marks the violent death of a massive star. These explosions are some of the most spectacular events in our Universe. When a star explodes relatively close by, e.g., in our own Milky Way Galaxy, then its light can be visible even without a telescope, and a “new” star appears in the sky.

2017-05-22

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When exploring the unknown it makes sense to be guided by expectation, but simultaneously to keep one’s eyes wide open for the unexpected.

This open approach is taken in the PowerFlux all-sky search for continuous gravitational waves, the full details of which are described in a recent publication. Here we summarize the main findings of that publication.

2017-05-01

PDF: [en]

In 2015 the Advanced Laser Interferometer Gravitational Wave Observatory (LIGO) detected gravitational waves from merging black holes (GW150914 and GW151226) during its first observing run. Although these signals originated from distances of more than a billion light years, they were loud enough to be successfully detected despite being within LIGO’s frequency band for less than a second immediately before the black holes’ catastrophic collision.

2017-04-12

PDF: [en]

The recent detection of gravitational waves from merging binary black hole systems (GW150914 and GW151226) has now opened up the exciting new field of gravitational wave astronomy.

2017-02-03

PDF: [en]

During its first observing run, the Advanced Laser Interferometer Gravitational Wave Observatory (LIGO) detected gravitational waves from merging black holes on two separate occasions. The number of events observed during this run indicates that black holes merge more often than we anticipated.

2016-12-13

PDF: [en]

The era of gravitational wave physics has begun. In its first observing run, Advanced LIGO ‘heard’ the ringing of two pairs of black holes merging.

2016-12-13

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The story of gamma-ray bursts (GRBs) began in the 1960s aboard spacecrafts designed to monitor the former Soviet Union for compliance with the nuclear test ban treaty of 1963. The satellites of the Vela series, each armed with a number of cesium iodide scintillation counters, recorded many puzzling bursts of gamma-ray radiation that did not fit the expected signature of a nuclear weapon.

2016-11-29

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Several previous LIGO searches have used an approach called “multi-messenger astronomy” to improve our chance of detecting gravitational waves. By looking for gravitational waves and a different kind of signal coming from space at the same time and direction, we can gain a couple of advantages over just looking at one type of data.

2016-06-21

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A few months after the first detection of gravitational waves from the black hole merger event GW150914, the Laser Interferometer Gravitational-Wave Observatory (LIGO) has made another observation of gravitational waves from the collision and merger of a pair of black holes.

2016-07-15

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On September 14, 2015, the two detectors Laser Interferometer Gravitational-wave Observatory (LIGO) observed a gravitational wave signal generated by the merger of two black holes. The LIGO detectors were recently upgraded with new instrumentation and now operate as Advanced LIGO, able to measure changes in the local shape of space-time with a precision better than one-thousandth the diameter of a proton.

2016-04-20

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Albert Einstein’s general theory of relativity, first published a century ago, was described by physicist Max Born as ‘the greatest feat of human thinking about nature’. We report on two major scientific breakthroughs involving key predictions of Einstein’s theory: the first direct detection of gravitational waves and the first observation of the collision and merger of a pair of black holes.

2016-02-11

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LIGO and Virgo have thought about where we want to be in five (and more) years, and have written up an answer. This might not be much use for job interviews, but should let other astrophysicists know what to expect. A plan was first produced back in 2013, and now we are updating it with our progress.

2015-12-23

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A lot of work has been carried out by scientists searching for gravitational waves (GWs) with the LIGO and Virgo detectors. So far, the focus either has been on short GW signals, lasting a few tenths of a second or less, or on very long-lasting GW signals, which persist indefinitely. But what about “intermediate” GW signals which fall in between these two extremes?

2015-11-24

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Neutron stars are remnants of the collapse of stars with masses in the range between about 8 and 20 solar masses. They are extremely dense objects, with a typical mass of about 1.5 solar masses and a radius of about 10 kilometers, reaching in the interior a density greater than that of atomic nuclei.

2015-10-14

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In the hills above Los Angeles, Griffith Observatory looks over the city. From the observatory deck at night, one can see beautiful lines of light along city roads, tracing the paths of cars as people hurry home or go out to enjoy the nightlife.

2015-10-14

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Black holes may be getting all the press these days, but neutron stars are more complicated and involve more physics: These collapsed stars are almost as compact and therefore as relativistic as black holes, but unlike black holes the matter in them is still visible to the outside universe.

2014-12-22

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We present results of a search for continuously emitted gravitational waves from the neutron star in the brightest low-mass X-ray binary (LMXB), Scorpius X-1. The analysis covers 10 days of data from LIGO’s 5th science run (S5) in the frequency band ranging from 50 to 550 Hz.

2014-12-08

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Isolated spinning neutron stars are among the targets of interferometric gravitational wave detectors such as Virgo in Italy, LIGO in the US and GEO600 in Germany. If these stars are not perfectly symmetric about their axis of rotation, e.g. if they have a “mountain” on their surface, they are expected to emit continuous gravitational waves.

2014-10-31

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Gravitational waves are fluctuations of spacetime predicted by Einstein’s general theory of relativity, which describes how gravity works. These waves are expected to be produced by almost everything in the Universe, including us human beings.

2014-10-31

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Nearly a century ago, Einstein predicted gravitational waves, ripples in space and time that travel at the speed of light, as part of his general theory of relativity. The energy carried by these waves was shown by Hulse and Taylor to be responsible for the inspiral of binary neutron stars, such as PSR B1913+16.

2014-10-30

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Cosmic explosions are excellent natural laboratories with which to learn about how particles behave at extreme energies, as well as providing a window on the distant universe. In the center of these events are often black holes that swallow matter from their environment, resulting in outflows of highly energetic gas.

2014-07-07

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There has been a lot of chatter in the news about the exciting findings of the BICEP2 experiment. But what do they mean?

2014-06-25

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We have conducted the first ever search for the continuous gravitational waves emitted by spinning neutron stars in binary systems that have not yet been observed. Neutron stars are expected to be fairly smooth and symmetric, but perhaps not perfectly symmetric.

2014-06-04

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One of the great open questions in astrophysics is the origin of gamma-ray bursts (GRBs). GRBs are intense flashes of high-energy photons, which are observed approximately once per day, and last only a few seconds.

2014-05-15

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There are many instruments which can detect gamma-rays operating in space, and they sometimes observe bright flashes which we call gamma-ray bursts (GRBs). Although they only last for a very short period of time, GRBs are the brightest electromagnetic events in the universe.

2014-04-15

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Black holes are among the most intriguing and mysterious objects in our Universe and are generated when space and time are warped so strongly that nothing, not even light, can escape. As light itself is trapped, how can they be observed?

2014-04-09

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Every star in the universe vibrates or oscillates in some manner. Turbulence on the surface of the Sun causes well-known solar oscillations that are studied under the field of helioseismology.

2014-03-26

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Gravitational waves are ripples of space-time propagating with the speed of light in the space-time itself. These waves are predicted by the general theory of relativity; indirect evidence supports their existence.

2014-02-24

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Many of the stars in the nearby universe are not too different from our Sun: relatively small and long-lived, shining for billions of years. A small fraction, however, are much more massive, and burn their hydrogen “fuel” more rapidly.

2014-01-16

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Cosmic strings are objects that may have formed in the early Universe, but scientists are still searching for evidence that they exist. They were first introduced by theoretical physicist Tom W. B. Kibble in the late 70s as a possible result of some field theories [*], including the famous Higgs theory.

2013-11-14

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Spinning neutron stars are promising candidates for producing gravitational wave signals detectable by the LIGO and Virgo laser interferometer detectors. These objects may generate continuous gravitational waves if they are not perfectly symmetric around their rotation axis.

2013-11-14

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The joint observation of an astronomical event with both light and gravitational waves would certainly be one of the most exciting discoveries of modern astronomy. The two types of waves are quite different.

2013-10-16

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The LIGO and Virgo observatories seek to detect gravitational waves—minute ripples in the fabric of spacetime, which can be created by the violent deaths of some small subset of massive stars. Gravitational waves are comparable to sound waves.

2013-10-04

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Einstein’s General Theory of Relativity predicts that the motion of masses can lead to the emission of gravitational radiation, commonly called gravitational waves. These waves, which are distortions in the fabric of space-time, ripple out from their sources at the speed of light.

2013-09-26

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Einstein’s General Theory of Relativity predicts that rapidly rotating neutron stars with a small deviation from perfect axial symmetry emit continuous gravitational waves. Although a number of potential sources are known, no direct detection has been made yet.

2013-09-26

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Recent progress in generating quantum states of squeezed vacuum has made it possible to enhance the sensitivity of the 4 km gravitational wave detector at the LIGO Hanford Observatory to an unprecedented level. LIGO, the Laser Interferometer Gravitational-wave Observatory, operates large Michelson interferometers with the goal of detecting gravitational waves from black holes, neutron stars, supernovae, and remnants of the Big Bang.

2013-08-02

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The LIGO and Virgo gravitational-wave detectors have been hunting for signals from the collisions of neutron stars and black holes, which are dense objects formed from the remains of stars many times more massive than our Sun. When two of these objects orbit each other in a binary system, the emission of gravitational waves will gradually carry away some of their orbital energy, forcing them to get closer and closer together.

2013-04-05

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Many of the stars in the nearby universe are not too different from our Sun: relatively small and long-lived, shining for billions of years. But a small fraction are much more massive, and burn their hydrogen “fuel” more rapidly.

2012-10-01

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Gravitational waves (GWs) are small ripples in the geometry of space-time, predicted to exist by Einstein’s General Theory of Relativity, and propagating at the speed of light. We hope to detect GWs emitted by sources at astrophysical distances by using large laser interferometers.

2012-08-03

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Many of the violent phenomena observed in our Universe are potential emitters of gravitational waves and high energy neutrinos. Both these cosmic messengers, not yet directly observed by conventional astronomy, can travel unimpeded over great distances, carrying information from unseen regions of our Universe.

2012-05-15

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According to Einstein’s theory of General Relativity, gravitational waves are ripples in the fabric of space – a stretching and squeezing of space itself. They are caused by some of the most violent phenomena in the universe, such as the supernova explosions that blast apart dying stars, and the collisions of neutron stars and black holes.

2012-05-11

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Seeing and hearing something at the same time can teach you more than you could learn with just one sense. In the same way, combining gravitational waves with conventional astronomy done with electromagnetic waves (light, X-rays, radio waves etc.) promises to teach us much more about the universe than either could alone.

2012-05-08

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A world-wide network of gravitational-wave detectors (LIGO, Virgo, GEO) is searching for gravitational waves (GW) emitted by astrophysical sources. To observe the tiny ripples in space-time produced by gravitational waves, these detectors use laser interferometers able to accurately measure the distance between mirrors hung in a vacuum and isolated as much as possible from their environment.

2012-04-02

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Scientists expect that neutron stars and black holes — the superdense remnants of dead stars — bound together in close orbits will not stay that way forever. Over time, they will lose energy by the emission of gravitational waves and “inspiral” towards each other until they merge together.

2012-03-14

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Gravitational waves are a fascinating prediction of Albert Einstein’s theory of relativity. Unlike sound waves, which are air pressure variations, or light waves, which are electromagnetic oscillations, gravitational waves are “ripples” of the space-time itself propagating at the speed of light.

2012-02-15

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Observing astronomical events with both light and gravitational waves will tell us more about the cause of the events than either observation would alone. In order to take advantage of this potential, LIGO and Virgo have established partnerships with scientists who operate telescopes around the world and developed the systems needed to quickly analyze gravitational wave data and send alerts to the telescopes.

2012-02-06

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Einstein’s theory of general relativity predicts that two closely-orbiting massive objects will lose energy and fall towards each other, emitting a distinct gravitational-wave signature. Black holes, the ultra-compact remnants of very massive stars, are prime candidates for emitting detectable gravitational waves in this way.

2012-01-31

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A recent analysis of observations made by the LIGO detectors has decisively ruled out the collision of two neutron stars or a neutron star and a black hole as being responsible for a gamma-ray burst (GRB) in a nearby galaxy. This result lends credence to the hypothesis that this GRB, observed in late 2005, was really a giant flare from a magnetar, potentially the most distant event of its kind ever observed.

2012-01-23

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The inspirals of neutron stars with either another neutron star or a black hole are among the most energetic astronomical events in the universe. As such, they are the most promising candidates for producing both gravitational wave signals visible to the LIGO and Virgo detectors as well as a variety of electromagnetic signals ranging from gamma rays to optical signals to radio waves, visible with gamma ray, optical and radio telescopes, respectively.

2012-01-11

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The Laser Interferometer Gravitational-wave Observatory (LIGO) Scientific Collaboration and the Virgo Collaboration have produced a sky map limiting the strength of persistent gravitational-wave sources.

2012-01-03

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Using data taken between November 2005 and September 2007, the Laser Interferometer Gravitational-wave Observatory (LIGO) Scientific Collaboration and the Virgo Collaboration have placed upper limits on the amplitude of the stochastic gravitational wave background.

2011-12-21

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Using data taken between July 2009 and October 2010, researchers from the Laser Interferometer Gravitational-wave Observatory (LIGO) Scientific Collaboration and the Virgo Collaboration have completed a joint search for merging binary star systems consisting of neutron stars and black holes.

2011-12-01

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2011-09-11

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