G. Desvignes
A5052243752- Pulsars and Gravitational Waves Research
- Astrophysical Phenomena and Observations
- Geophysics and Gravity Measurements
- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Gamma-ray bursts and supernovae
- Advanced Frequency and Time Standards
- Cosmology and Gravitation Theories
- High-pressure geophysics and materials
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- GNSS positioning and interference
- Astronomical Observations and Instrumentation
- Superconducting Materials and Applications
- Superconducting and THz Device Technology
- Galaxies: Formation, Evolution, Phenomena
- Particle Accelerators and Free-Electron Lasers
- Astro and Planetary Science
- Seismic Waves and Analysis
- Planetary Science and Exploration
- Geophysics and Sensor Technology
- Particle accelerators and beam dynamics
- Dark Matter and Cosmic Phenomena
- Solar and Space Plasma Dynamics
- Advanced X-ray Imaging Techniques
Max Planck Institute for Radio Astronomy
2016-2025
Laboratoire d’études spatiales et d’instrumentation en astrophysique
2019-2025
Centre National de la Recherche Scientifique
2010-2024
Sorbonne Université
2019-2024
Université Paris Cité
2019-2024
Observatoire de Paris
2008-2024
Université Paris Sciences et Lettres
2019-2024
Université de Versailles Saint-Quentin-en-Yvelines
2020-2024
Délégation Paris 7
2019-2022
Sorbonne Paris Cité
2019-2022
When surrounded by a transparent emission region, black holes are expected to reveal dark shadow caused gravitational light bending and photon capture at the event horizon. To image study this phenomenon, we have assembled Event Horizon Telescope, global very long baseline interferometry array observing wavelength of 1.3 mm. This allows us reconstruct event-horizon-scale images supermassive hole candidate in center giant elliptical galaxy M87. We resolved central compact radio source as an...
We present measurements of the properties central radio source in M87 using Event Horizon Telescope data obtained during 2017 campaign. develop and fit geometric crescent models (asymmetric rings with interior brightness depressions) two independent sampling algorithms that consider distinct representations visibility data. show family is statistically preferred over other comparably complex we explore. calibrate model parameters general relativistic magnetohydrodynamic (GRMHD) emission...
We present the first Event Horizon Telescope (EHT) images of M87, using observations from April 2017 at 1.3 mm wavelength. These show a prominent ring with diameter ~40 micro-as, consistent size and shape lensed photon orbit encircling "shadow" supermassive black hole. The is persistent across four observing nights shows enhanced brightness in south. To assess reliability these results, we implemented two-stage imaging procedure. In stage, teams, each blind to others' work, produced M87 both...
The Event Horizon Telescope (EHT) has mapped the central compact radio source of elliptical galaxy M87 at 1.3 mm with unprecedented angular resolution. Here we consider physical implications asymmetric ring seen in 2017 EHT data. To this end, construct a large library models based on general relativistic magnetohydrodynamic (GRMHD) simulations and synthetic images produced by ray tracing. We compare observed visibilities confirm that is consistent earlier predictions strong gravitational...
We present the first Event Horizon Telescope (EHT) observations of Sagittarius A* (Sgr A$^*$), Galactic center source associated with a supermassive black hole. These were conducted in 2017 using global interferometric array eight telescopes operating at wavelength $\lambda=1.3\,{\rm mm}$. The EHT data resolve compact emission region intrahour variability. A variety imaging and modeling analyses all support an image that is dominated by bright, thick ring diameter $51.8 \pm 2.3$\,\uas (68\%...
The Event Horizon Telescope (EHT) is a very long baseline interferometry (VLBI) array that comprises millimeter- and submillimeter-wavelength telescopes separated by distances comparable to the diameter of Earth. At nominal operating wavelength ~1.3 mm, EHT angular resolution (lambda/D) ~25 micro-as, which sufficient resolve nearby supermassive black hole candidates on spatial temporal scales correspond their event horizons. With this capability, scientific goals are probe general...
This catalog summarizes 117 high-confidence ⩾0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on Fermi satellite. Half are neutron stars discovered LAT through periodicity searches in and radio around unassociated source positions. The pulsars evenly divided into groups: millisecond pulsars, young radio-loud radio-quiet pulsars. We characterize pulse profiles energy spectra derive luminosities when distance information exists. Spectral...
We present the calibration and reduction of Event Horizon Telescope (EHT) 1.3mm radio wavelength observations supermassive black hole candidate at center galaxy M87 quasar 3C 279, taken during 2017 April 5-11 observing campaign. These global very long baseline interferometric include for first time highly sensitive Atacama Large Millimeter/submillimeter Array (ALMA); reaching an angular resolution 25 micro-as, with characteristic sensitivity limits ~1 mJy on baselines to ALMA ~10 other...
The International Pulsar Timing Array project combines observations of pulsars from both northern and southern hemisphere observatories with the main aim detecting ultra-low frequency (∼ 10−9–10−8 Hz) gravitational waves. Here we introduce project, review methods used to search for waves emitted coalescing supermassive binary black-hole systems in centres merging galaxies discuss status project.
We present the results of search for an isotropic stochastic gravitational wave background (GWB) at nanohertz frequencies using second data release European Pulsar Timing Array (EPTA) 25 millisecond pulsars and a combination with first Indian (InPTA). analysed (i) full 24.7-year EPTA set, (ii) its 10.3-year subset based on modern observing systems, (iii) set InPTA ten commonly timed pulsars, (iv) data. These combinations allowed us to probe contributions instrumental noise interstellar...
Event Horizon Telescope (EHT) observations at 230 GHz have now imaged polarized emission around the supermassive black hole in M87 on event-horizon scales. This synchrotron radiation probes structure of magnetic fields and plasma properties near hole. Here we compare resolved polarization observed by EHT, along with simultaneous unresolved Atacama Large Millimeter/submillimeter Array, to expectations from theoretical models. The low fractional linear image suggests that is scrambled scales...
The highly stable spin of neutron stars can be exploited for a variety (astro)physical investigations. In particular, arrays pulsars with rotational periods the order milliseconds used to detect correlated signals such as those caused by gravitational waves. Three ‘pulsar timing arrays’ (PTAs) have been set up around world over past decades and collectively form ‘International’ PTA (IPTA). this paper, we describe first joint analysis data from three regional PTAs, i.e. IPTA set. We available...
We report on the high-precision timing of 42 radio millisecond pulsars (MSPs) observed by European Pulsar Timing Array (EPTA). This EPTA Data Release 1.0 extends up to mid-2014 and baselines range from 7-18 years. It forms basis for stochastic gravitational-wave background, anisotropic continuous-wave limits recently presented elsewhere. The Bayesian analysis performed with TempoNest yields detection several new parameters: seven parallaxes, nine proper motions and, in case six binary...
Astrophysical black holes are expected to be described by the Kerr metric. This is only stationary, vacuum, axisymmetric metric, without electromagnetic charge, that satisfies Einstein's equations and does not have pathologies outside of event horizon. We present new constraints on potential deviations from prediction based 2017 EHT observations Sagittarius A* (Sgr A*). calibrate relationship between geometrically defined hole shadow observed size ring-like images using a library includes...
Abstract In this paper we provide a first physical interpretation for the Event Horizon Telescope's (EHT) 2017 observations of Sgr A*. Our main approach is to compare resolved EHT data at 230 GHz and unresolved non-EHT from radio X-ray wavelengths predictions library models based on time-dependent general relativistic magnetohydrodynamics simulations, including aligned, tilted, stellar-wind-fed simulations; radiative transfer performed assuming both thermal nonthermal electron distribution...
Abstract In 2017 April, the Event Horizon Telescope (EHT) observed near-horizon region around supermassive black hole at core of M87 galaxy. These 1.3 mm wavelength observations revealed a compact asymmetric ring-like source morphology. This structure originates from synchrotron emission produced by relativistic plasma located in immediate vicinity hole. Here we present corresponding linear-polarimetric EHT images center M87. We find that only part ring is significantly polarized. The...
Abstract We present the first event-horizon-scale images and spatiotemporal analysis of Sgr A* taken with Event Horizon Telescope in 2017 April at a wavelength 1.3 mm. Imaging has been conducted through surveys over wide range imaging assumptions using classical CLEAN algorithm, regularized maximum likelihood methods, Bayesian posterior sampling method. Different prescriptions have used to account for scattering effects by interstellar medium toward Galactic center. Mitigation rapid intraday...
We present results from the search for a stochastic gravitational-wave background (GWB) as predicted by theory of General Relativity using six radio millisecond pulsars Data Release 2 (DR2) European Pulsar Timing Array (EPTA) covering timespan up to 24 years. A GWB manifests itself long-term low-frequency signal common all pulsars, red (CRS), with characteristic Hellings-Downs (HD) spatial correlation. Our analysis is performed two independent pipelines, \eprise{} and \tn{}+\ftwo{}, which...
We searched for an isotropic stochastic gravitational wave background in the second data release of International Pulsar Timing Array, a global collaboration synthesizing decadal-length pulsar-timing campaigns North America, Europe, and Australia. In our reference search power law strain spectrum form $h_c = A(f/1\,\mathrm{yr}^{-1})^{\alpha}$, we found strong evidence spectrally-similar low-frequency process amplitude $A 3.8^{+6.3}_{-2.5}\times10^{-15}$ spectral index $\alpha -0.5 \pm 0.5$,...
Direct detection of low-frequency gravitational waves (GWs, Hz) is the main goal pulsar timing array (PTA) projects. One targets for PTAs to measure stochastic background (GWB) whose characteristic strain expected approximately follow a power-law form , where f GW frequency. In this paper we use current data from European PTA determine an upper limit on GWB amplitude A as function unknown spectral slope α with Bayesian algorithm, by modelling random Gaussian process. For case α=−2/3, which...
The 2017 Event Horizon Telescope (EHT) observations of the central source in M87 have led to first measurement size a black-hole shadow. This observation offers new and clean gravitational test metric strong-field regime. We show analytically that spacetimes deviate from Kerr but satisfy weak-field tests can lead large deviations predicted shadows are inconsistent with even current EHT measurements. use numerical calculations regular, parametric, non-Kerr metrics identify common...
In this paper, we describe the International Pulsar Timing Array second data release, which includes recent pulsar timing obtained by three regional consortia: European Array, North American Nanohertz Observatory for Gravitational Waves, and Parkes Array. We analyse where possible combine high-precision 65 millisecond pulsars are regularly observed these groups. A basic noise analysis, including processes both correlated uncorrelated in time, provides models ephemerides pulsars. find that...
We present Event Horizon Telescope (EHT) 1.3 mm measurements of the radio source located at position supermassive black hole Sagittarius A* (Sgr A*), collected during 2017 April 5--11 campaign. The observations were carried out with eight facilities six locations across globe. Novel calibration methods are employed to account for Sgr A*'s flux variability. majority emission arises from horizon scales, where intrinsic structural variability is detected on timescales minutes hours. effects...