Explanipedia

The double neutron star PSR J1946+2052 Open

Lingqi Meng, P. C. C. Freire, K. Stovall, Norbert Wex, Xueli Miao , et al. · 2025

Aims. Double neutron star (DNS) systems are superb laboratories for testing theories of gravity and constraining the equation of state of ultra-dense matter. PSR J1946+2052 is a particularly intriguing DNS system due to its orbital period …

The double neutron star PSR J1946+2052 I. Masses and tests of general relativity Open

Lingqi Meng, P. C. C. Freire, K. Stovall, Norbert Wex, Xueli Miao , et al. · 2025

We conducted high-precision timing of PSR J1946+2052 to determine the masses of the two neutron stars in the system, test general relativity (GR) and assessed the system's potential for future measurement of the moment of inertia of the pu…

NGC 1851A: Revealing an ongoing three-body encounter in a dense globular cluster Open

Arunima Dutta, P. C. C. Freire, T. Gautam, Norbert Wex, A. Ridolfi , et al. · 2025

PSR J0514−4002A is a binary millisecond pulsar located in the globular cluster NGC 1851. The pulsar has a spin period of 4.99 ms, an orbital period of 18.8 days, and is in a very eccentric ( e = 0.89) orbit around a massive companion. In t…

Demographics of black holes at $<$100 R$_{\rm g}$ scales: accretion flows, jets, and shadows Open

Dhanya G. Nair, Neil M. Nagar, Venkatessh Ramakrishnan, Maciek Wielgus, Vicente Arratia , et al. · 2024

Using the Event Horizon Telescope (EHT), the gravitationally lensed rings around the supermassive black holes (SMBHs) in Messier 87 (M87) and Sagittarius A* (Sgr A*) have now been successfully imaged at a resolution under 10 gravitational …

Explanation of the exceptionally strong timing noise of PSR J0337+1715 by a circum-ternary planet and consequences for gravity tests Open

Guillaume Voisin, I. Cognard, Melaine Saillenfest, Thomas M. Tauris, Norbert Wex , et al. · 2024

Context. Timing of pulsar PSR J0337+1715 provides a unique opportunity to test the strong equivalence principle (SEP) with a strongly self-gravitating object. This is due to its unique situation in a triple stellar system with two white dw…

Explanation of the exceptionally strong timing noise of PSR J0337+1715 by a circum-ternary planet and consequences for gravity tests Open

Guillaume Voisin, I. Cognard, Melaine Saillenfest, Thomas M. Tauris, Norbert Wex , et al. · 2024

Context: Timing of pulsar PSR J0337+1715 provides a unique opportunity to test the strong equivalence principle (SEP) with a strongly self-gravitating object. This is due to its unique situation in a triple stellar system with two white dw…

MeerKAT observations of pair-plasma induced birefringence in the double pulsar eclipses Open

M. E. Lower, M. Krämer, S. Johnston, R. P. Breton, Norbert Wex , et al. · 2024

PSR J0737−3039A/B is unique among double neutron star systems. Its near-perfect edge-on orbit causes the fast spinning pulsar A to be eclipsed by the magnetic field of the slow spinning pulsar B. Using high-sensitivity MeerKAT radio observ…

Gravity experiments with radio pulsars Open

P. C. C. Freire, Norbert Wex · 2024

The discovery of the first pulsar in a binary star system, the Hulse–Taylor pulsar, 50 years ago opened up an entirely new field of experimental gravity. For the first time it was possible to investigate strong-field and radiative aspects …

A pulsar in a binary with a compact object in the mass gap between neutron stars and black holes Open

E D Barr, Arunima Dutta, P. C. C. Freire, Mario Cadelano, T. Gautam , et al. · 2024

Some compact objects observed in gravitational wave events have masses in the gap between known neutron stars (NSs) and black holes (BHs). The nature of these mass gap objects is unknown, as is the formation of their host binary systems. W…

A MeerKAT view of the double pulsar eclipses Open

M. E. Lower, M. Krämer, R. M. Shannon, R. P. Breton, Norbert Wex , et al. · 2023

The double pulsar system, PSR J0737−3039A/B, consists of two neutron stars bound together in a highly relativistic orbit that is viewed nearly edge-on from the Earth. This alignment results in brief radio eclipses of the fast-rotating puls…

A MeerKAT view of the double pulsar eclipses -- Geodetic precession of pulsar B and system geometry Open

M. E. Lower, M. Krämer, R. M. Shannon, R. P. Breton, Norbert Wex , et al. · 2023

The double pulsar system, PSR J0737$-$3039A/B, consists of two neutron stars bound together in a highly relativistic orbit that is viewed nearly edge-on from the Earth. This alignment results in brief radio eclipses of the fast-rotating pu…

New constraints on the kinematic, relativistic, and evolutionary properties of the PSR J1757−1854 double neutron star system Open

A D Cameron, M. Bailes, D. J. Champion, P. C. C. Freire, M. Krämer , et al. · 2023

PSR J1757−1854 is one of the most relativistic double neutron star binary systems known in our Galaxy, with an orbital period of $P_\text{b}=4.4\, \text{h}$ and an orbital eccentricity of e = 0.61. As such, it has promised to be an outstan…

New constraints on the kinematic, relativistic and evolutionary properties of the PSR J1757$-$1854 double neutron star system Open

A. D. Cameron, M. Bailes, D. J. Champion, P. C. C. Freire, M. Krämer , et al. · 2023

PSR J1757$-$1854 is one of the most relativistic double neutron star binary systems known in our Galaxy, with an orbital period of $P_\text{b}=4.4\,\text{hr}$ and an orbital eccentricity of $e=0.61$. As such, it has promised to be an outst…

A new pulsar timing model for scalar-tensor gravity with applications to PSR J2222-0137 and pulsar-black hole binaries Open

A. Batrakov, H. Hu, Norbert Wex, P. C. C. Freire, V. Venkatraman Krishnan , et al. · 2023

Context . Scalar-tensor gravity (STG) theories are well-motivated alternatives to general relativity (GR). One class of STG theories, Damour–Esposito–Farèse (DEF) gravity, has a massless scalar field with two arbitrary coupling parameters.…

A new pulsar timing model for scalar-tensor gravity with applications to PSR J2222-0137 and pulsar-black hole binaries Open

A. V. Batrakov, H. Hu, Norbert Wex, P. C. C. Freire, V. Venkatraman Krishnan , et al. · 2023

Context. Scalar-tensor gravity (STG) theories are well-motivated alternatives to general relativity (GR). One class of STG theories, the Damour-Esposito-Farese (DEF) gravity, has a massless scalar field with two arbitrary coupling paramete…

News and views regarding PSR J1757–1854, a highly-relativistic binary pulsar Open

A D Cameron, M. Bailes, V. Balakrishnan, D. J. Champion, P. C. C. Freire , et al. · 2023

Gravitational signal propagation in the double pulsar studied with the MeerKAT telescope Open

H. Hu, M. Krämer, D. J. Champion, Norbert Wex, A. Parthasarathy , et al. · 2022

The double pulsar PSR J0737−3039A/B has offered a wealth of gravitational experiments in the strong-field regime, all of which general relativity has passed with flying colours. In particular, among current gravity experiments that test ph…

Closing a spontaneous-scalarization window with binary pulsars Open

Junjie Zhao, P. C. C. Freire, M. Kramer, Lijing Shao, Norbert Wex · 2022

Benefitting from the unequaled precision of the pulsar timing technique, binary pulsars are important testbeds of gravity theories, providing some of the tightest bounds on alternative theories of gravity. One class of well-motivated alter…

Strong-Field Gravity Tests with the Double Pulsar Open

M. Krämer, I. H. Stairs, R. N. Manchester, Norbert Wex, Adam T. Deller , et al. · 2021

Continued observations of the Double Pulsar, PSR J0737-3039A/B, consisting of\ntwo radio pulsars (A and B) that orbit each other with a period of 2.45hr in a\nmildly eccentric (e=0.088) binary system, have led to large improvements in the\…

The Variability of the Black-Hole Image in M87 at the Dynamical Time Scale Open

Kaushik Satapathy, Norbert Wex, Feryal Özel, Lia Medeiros, Sean Taylor Dougall , et al. · 2021

The black-hole images obtained with the Event Horizon Telescope (EHT) are expected to be variable at the dynamical timescale near their horizons. For the black hole at the center of the M87 galaxy, this timescale (5-61 days) is comparable …

PSR J2222−0137 Open

Y. J. Guo, P. C. C. Freire, L. Guillemot, M. Krämer, Weiwei Zhu , et al. · 2021

Context. The PSR J2222−0137 binary system has a set of features that make it a unique laboratory for tests of gravity theories. Aims. To fully exploit the system’s potential for these tests, we aim to improve the measurements of its physic…

An 86 GHz Search for Pulsars in the Galactic Center with the Atacama Large Millimeter / submillimeter Array Open

Kuo Liu, G. Desvignes, Ralph P. Eatough, R. Karuppusamy, M. Krämer , et al. · 2021

We report on the first pulsar and transient survey of the Galactic Center (GC) with the Atacama Large Millimeter/submillimeter Array (ALMA). The observations were conducted during the Global Millimeter VLBI Array campaign in 2017 and 2018.…

The relativistic binary programme on MeerKAT: science objectives and first results Open

M. Krämer, I. H. Stairs, V. Venkatraman Krishnan, P. C. C. Freire, Federico Abbate , et al. · 2021

We describe the ongoing Relativistic Binary programme (RelBin), a part of the MeerTime large survey project with the MeerKAT radio telescope. RelBin is primarily focused on observations of relativistic effects in binary pulsars to enable m…

Parkes observations for project P1054 semester 2021APRS_04 Open

M. Burgay, Andrea Possenti, Michael Kramer, Paulo Freire, Patrick Weltevrede , et al. · 2021

With this proposal we ask time for a timing follow-up campaign of the first 5 mllisecond pulsars discovered in the TRAPUM (TRAnsients and PUlsars with Meerkat) survey. The sources have been detected in targeted observations of Fermi uniden…

Understanding and improving the timing of PSR J0737−3039B Open

A. Noutsos, G. Desvignes, M. Krämer, Norbert Wex, P. C. C. Freire , et al. · 2020

\nThe double pulsar (PSR J0737−3039A/B) provides some of the most stringent tests of general relativity (GR) and its alternatives. The success of this system in tests of GR is largely due to the high-precision, long-term timing of its recy…

A revisit of PSR J1909−3744 with 15-yr high-precision timing Open

Kuan Liu, L. Guillemot, Alina Istrate, Lijing Shao, Thomas M. Tauris , et al. · 2020

We report on a high-precision timing analysis and an astrophysical study of the binary millisecond pulsar, PSR J1909−3744, motivated by the accumulation of data with well improved quality over the past decade. Using 15 yr of observations w…

Gravity Tests with Radio Pulsars Open

Norbert Wex, M. Krämer · 2020

The discovery of the first binary pulsar in 1974 has opened up a completely new field of experimental gravity. In numerous important ways, pulsars have taken precision gravity tests quantitatively and qualitatively beyond the weak-field sl…

New graviton mass bound from binary pulsars Open

Lijing Shao, Norbert Wex, Shuang-Yong Zhou · 2020

In Einstein's general relativity, gravity is mediated by a massless metric field. The extension of general relativity to consistently include a mass for the graviton has profound implications for gravitation and cosmology. Salient features…

Constraining the dense matter equation-of-state with radio pulsars Open

H. Hu, M. Krämer, Norbert Wex, D. J. Champion, M. S. Kehl · 2020

Radio pulsars provide some of the most important constraints for our understanding of matter at supranuclear densities. So far, these constraints are mostly given by precision mass measurements of neutron stars (NS). By combining single me…

An improved test of the strong equivalence principle with the pulsar in a triple star system Open

Guillaume Voisin, I. Cognard, P. C. C. Freire, Norbert Wex, L. Guillemot , et al. · 2020

This repository contains the source code of the Nutimo software, the dataset and results of the article "An improved test of the strong equivalence principle with the pulsar in a triple star system", Voisin, Cognard, Freire, Wex, Guillemot…

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