P. C. C. Freire
A5089004860- Pulsars and Gravitational Waves Research
- Geophysics and Gravity Measurements
- Gamma-ray bursts and supernovae
- Stellar, planetary, and galactic studies
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- High-pressure geophysics and materials
- Cosmology and Gravitation Theories
- Astronomy and Astrophysical Research
- Geophysics and Sensor Technology
- Astronomical Observations and Instrumentation
- Particle Accelerators and Free-Electron Lasers
- Advanced Frequency and Time Standards
- Superconducting Materials and Applications
- Inertial Sensor and Navigation
- Astrophysics and Star Formation Studies
- Magnetic confinement fusion research
- GNSS positioning and interference
- Particle accelerators and beam dynamics
- Solar and Space Plasma Dynamics
- Statistical and numerical algorithms
- Astro and Planetary Science
- Atomic and Subatomic Physics Research
- Particle physics theoretical and experimental studies
Max Planck Institute for Radio Astronomy
2016-2025
Biocant
2021
John Wiley & Sons (United States)
2019
John Wiley & Sons (United Kingdom)
2019
Oxfam
2019
Hudson Institute
2019
Osservatorio Astronomico di Cagliari
2004-2018
Netherlands Institute for Radio Astronomy
2018
Swinburne University of Technology
2018
University of Milano-Bicocca
2018
Many physically motivated extensions to general relativity (GR) predict substantial deviations in the properties of spacetime surrounding massive neutron stars. We report measurement a 2.01 ± 0.04 solar mass (M⊙) pulsar 2.46-hour orbit with 0.172 0.003 M⊙ white dwarf. The high and compact make this system sensitive laboratory previously untested strong-field gravity regime. Thus far, observed orbital decay agrees GR, supporting its validity even for extreme conditions present system....
One century after its formulation, Einstein's general relativity (GR) has made remarkable predictions and turned out to be compatible with all experimental tests. Most of these tests probe the theory in weak-field regime, there are theoretical reasons believe that GR should modified when gravitational fields strong spacetime curvature is large. The best astrophysical laboratories strong-field gravity black holes neutron stars, whether isolated or binary systems. We review motivations...
We summarize our current knowledge of neutron-star masses and radii. Recent instrumentation computational advances have resulted in a rapid increase the discovery rate precise timing radio pulsars binaries past few years, leading to large number mass measurements. These discoveries show that distribution is much wider than previously thought, with three known now firmly 1.9–2.0-M ⊙ range. For radii, large, high-quality data sets from X-ray satellites as well significant progress theoretical...
The double pulsar system PSR J0737-3039A/B is unique in that both neutron stars are detectable as radio pulsars. They also known to have much higher mean orbital velocities and accelerations than those of other binary therefore a good candidate for testing Einstein's theory general relativity alternative theories gravity the strong-field regime. We report on precision timing observations taken over 2.5 years since its discovery present four independent tests relativity. These use...
The clocklike properties of pulsars moving in the gravitational fields their unseen neutron-star companions have allowed unique tests general relativity and provided evidence for radiation. We report here detection 2.8-second pulsar J0737-3039B as companion to 23-millisecond J0737-3039A a highly relativistic double neutron star system, allowing unprecedented fundamental physics. observed short eclipse by orbital modulation flux density pulse shape J0737-3039B, probably because influence...
We have discovered a 716-hertz eclipsing binary radio pulsar in the globular cluster Terzan 5 using Green Bank Telescope. It is fastest spinning neutron star found to date, breaking 24-year record held by 642-hertz B1937+21. The difficulty detecting this pulsar, because of its very low flux density and high eclipse fraction (approximately 40% orbit), suggests that even faster stars exist. If has mass less than twice Sun, then radius must be constrained spin rate <16 kilometers. short period...
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...
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.
Abstract Double neutron star (DNS) systems represent extreme physical objects and the endpoint of an exotic journey stellar evolution binary interactions. Large numbers DNS their mergers are anticipated to be discovered using Square Kilometre Array searching for radio pulsars, high-frequency gravitational wave detectors (LIGO/VIRGO), respectively. Here we discuss all key properties systems, as well selection effects, combine latest observational data with new theoretical progress on various...
(abridged) We report the results of a 10-year timing campaign on PSR J1738+0333, 5.85-ms pulsar in low-eccentricity 8.5-hour orbit with low-mass white dwarf companion (...) The measurements proper motion and parallax allow for precise subtraction kinematic contribution to observed orbital decay; this significant measurement intrinsic decay: (-25.9 +/- 3.2) \times 10^{-15} s/s. This is consistent decay from emission gravitational waves predicted by general relativity, (-27.7 +1.5/-1.9) s/s...
Recent work has exploited pulsar survey data to identify temporally isolated, millisecond-duration radio bursts with large dispersion measures (DMs). These have been interpreted as arising from a population of extragalactic sources, in which case they would provide unprecedented opportunities for probing the intergalactic medium; may also be linked new source classes. Until now, however, all so-called fast (FRBs) detected Parkes telescope and its 13-beam receiver, casting some concern about...
The dramatic increase in the number of known gamma-ray pulsars since launch Fermi Gamma-ray Space Telescope (formerly GLAST) offers first opportunity to study a sizable population these high-energy objects. This catalog summarizes 46 high-confidence pulsed detections using six months data taken by Large Area (LAT), Fermi's main instrument. Sixteen previously unknown were discovered searching for signals at positions bright sources seen with LAT, or objects suspected be neutron stars based on...
We present an analysis of high-precision pulsar timing data taken as part the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) project. have observed 17 pulsars a span roughly five years using Green Bank and Arecibo radio telescopes. analyze these standard models, with addition time-variable dispersion measure frequency-variable pulse shape terms. Sub-microsecond residuals are obtained in nearly all cases, best rms this set ∼30–50 ns. methods analyzing post-fit...
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...
Continued observations of the Double Pulsar, PSR J0737-3039A/B, consisting two radio pulsars (A and B) that orbit each other with a period 2.45hr in mildly eccentric (e=0.088) binary system, have led to large improvements measurement relativistic effects this system. With 16-yr data span, results enable precision tests theories gravity for strongly self-gravitating bodies also reveal new been expected but are now observed first time. These include light propagation strong gravitational...
Abstract We describe system verification tests and early science results from the pulsar processor (PTUSE) developed for newly commissioned 64-dish SARAO MeerKAT radio telescope in South Africa. is a high-gain ( ${\sim}2.8\,\mbox{K Jy}^{-1}$ ) low-system temperature ${\sim}18\,\mbox{K at }20\,\mbox{cm}$ array that currently operates 580–1 670 MHz can produce tied-array beams suitable observations. This paper presents MeerTime Large Survey Project commissioning with PTUSE. Highlights include...
Abstract We present 294 pulsars found in GeV data from the Large Area Telescope (LAT) on Fermi Gamma-ray Space Telescope. Another 33 millisecond (MSPs) discovered deep radio searches of LAT sources will likely reveal pulsations once phase-connected rotation ephemerides are achieved. A further dozen optical and/or X-ray binary systems colocated with also harbor gamma-ray MSPs. This catalog thus reports roughly 340 and candidates, 10% all known pulsars, compared to ≤11 before Fermi. Half...
Among the compact objects observed in gravitational wave merger events a few have masses gap between most massive neutron stars (NSs) and least black holes (BHs) known. Their nature formation of their merging binaries are not well understood. We report on pulsar timing observations using Karoo Array Telescope (MeerKAT) PSR J0514-4002E, an eccentric binary millisecond globular cluster NGC 1851 with total mass $3.887 \pm 0.004$ solar masses. The companion to is object its (between $2.09$...
We have identified 21 millisecond pulsars (MSPs) in globular cluster Terzan 5 by using the Green Bank Telescope, bringing total of known MSPs to 24. These discoveries confirm fundamental predictions and binary system evolution. Thirteen new are binaries, which two show eclipses highly eccentric orbits. The relativistic periastron advance for systems indicates that at least one these has a mass 1.68 times greater than Sun 95% confidence. Such large neutron star masses constrain equation state...
We report on gamma-ray observations of the Crab Pulsar and Nebula using 8 months survey data with Fermi Large Area Telescope (LAT). The high quality light curve obtained ephemeris provided by Nancay Jodrell Bank radio telescopes shows two main peaks stable in phase energy. first peak leads pulse (281 \pm 12 21) mus, giving new constraints production site non-thermal emission pulsar magnetospheres. improved sensitivity unprecedented statistics afforded LAT enable precise measurement spectral...
We report results from the initial stage of a long-term pulsar survey Galactic plane using Arecibo L-band Feed Array (ALFA), seven-beam receiver operating at 1.4 GHz with 0.3 bandwidth. The search targets latitudes |b| < 5 deg in longitude ranges 32 l 77 and 168 deg. Data discussed here were collected over 100 MHz passband centered on 1.42 spectrometer that recorded 256 channels every 64 microsec. In preliminary, standard period-DM analysis, we have detected 29 previously known pulsars...
We present precise phase-connected pulse timing solutions for 16 gamma-ray-selected pulsars recently discovered using the Large Area Telescope (LAT) on Fermi Gamma-ray Space plus one very faint radio pulsar (PSR J1124-5916) that is more effectively timed with LAT. describe analysis techniques including a maximum likelihood method determining times of arrival from unbinned photon data. A major result this work improved position determinations, which are crucial multi-wavelength follow up. For...