REVIEW 1 major objections 1 minor 114 references
Testing Gravity with Binary Pulsars in the SKA Era
T0 review · 1 major / 1 minor · reviewed 2026-07-03 · grok-4.3
Pith's one-line read The Square Kilometre Array will enable deeper tests of general relativity by improving timing of known binary pulsars and discovering dozens of new relativistic systems.
desk verdict This is a science-case review projecting SKA pulsar timing improvements for gravity tests, without introducing new methods or results. read the letter →
The pith
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
The reading
What carries the argument
Timing precision of recycled pulsars in binary systems, which supplies the observable used to search for departures from general relativity.
What would settle it
SKA observations that fail to reach the required timing precision on recycled pulsars or that discover far fewer than dozens of new relativistic binaries.
Extended reading notes
Core claim
Binary and trinary radio pulsars act as natural laboratories for strong-field gravity. The SKA's high sensitivity in the Southern Hemisphere will improve timing precision of recycled pulsars, allowing deeper searches for deviations from general relativity in existing systems. A Galactic census will additionally discover dozens of new relativistic pulsar systems, including candidate pulsar-black hole binaries usable for tests of the cosmic censorship hypothesis and the no-hair theorem. The aspects of gravitation to be explored include the strong equivalence principle, gravitational dipole radiation, extra field components, gravitomagnetism, and spacetime symmetries.
Load-bearing premise
The Square Kilometre Array will reach the sensitivity needed in the Southern Hemisphere and the Galactic census will find the expected number of suitable new relativistic systems.
Editorial extensions
If this is right
- Deeper searches for deviations from general relativity become possible in already-known binary pulsar systems.
- Dozens of new relativistic pulsar systems will be found, including candidates for pulsar-black hole binaries.
- Tests of the cosmic censorship hypothesis and the no-hair theorem can be performed with any pulsar-black hole systems discovered.
- Measurements of the strong equivalence principle, gravitational dipole radiation, extra field components, gravitomagnetism, and spacetime symmetries will be sharpened.
- Radiative properties of gravity can be probed with higher precision than before.
Reading between the lines
- Success would give independent checks on strong-field gravity that complement gravitational-wave detections of black-hole mergers.
- The same timing data could be re-used to place limits on the population of compact objects and on the Galactic supernova rate.
- If no deviations appear, the results would tighten the parameter space available to alternative gravity theories that predict dipole radiation or violations of the equivalence principle.
- Non-detection of pulsar-black hole systems at the expected rate would require revision of current models of binary evolution.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The manuscript is a forward-looking science-case review for gravity tests with binary and trinary radio pulsars using the Square Kilometre Array (SKA). It claims that SKA's high sensitivity in the Southern Hemisphere will improve timing precision of recycled pulsars for deeper searches of deviations from general relativity in known systems, while a Galactic census will discover dozens of new relativistic systems (including potential pulsar-black hole binaries) usable for tests of the cosmic censorship hypothesis and no-hair theorem. The text outlines specific aspects of gravitation to be probed (strong equivalence principle, gravitational dipole radiation, extra field components, gravitomagnetism, spacetime symmetries) and the SKA capabilities required.
Significance. If the projected timing improvements and discovery yields are realized, the work usefully maps out a set of strong-field gravity tests that are complementary to other experiments and that exploit the unique properties of pulsar timing. It provides a clear roadmap of the observational requirements on SKA. The absence of quantitative error budgets or discovery-rate calculations, however, leaves the central 'dozens of systems' projection unsupported.
major comments (1)
- [Abstract] Abstract: the assertion that a Galactic census 'will yield the discovery of dozens of relativistic pulsar systems, including potentially pulsar-black hole binaries' for testing cosmic censorship and the no-hair theorem is presented without any supporting calculation, reference to expected yields, sensitivity thresholds, or error budget. This projection is load-bearing for the claim that SKA will open qualitatively new tests.
minor comments (1)
- [Abstract] Abstract: repeated 'will' in the sentence 'A Galactic census of pulsars will, in addition, will yield'.
Simulated Author's Rebuttal
We thank the referee for the positive assessment of the manuscript's significance and for the constructive comment on the abstract. We address the point below and have made revisions to strengthen the supporting references.
read point-by-point responses
-
Referee: [Abstract] Abstract: the assertion that a Galactic census 'will yield the discovery of dozens of relativistic pulsar systems, including potentially pulsar-black hole binaries' for testing cosmic censorship and the no-hair theorem is presented without any supporting calculation, reference to expected yields, sensitivity thresholds, or error budget. This projection is load-bearing for the claim that SKA will open qualitatively new tests.
Authors: We agree that the abstract would be strengthened by explicit references to the basis for the projected yields. The 'dozens of relativistic pulsar systems' figure is drawn from published population-synthesis and survey-sensitivity studies of SKA pulsar searches (including estimates for relativistic binaries and potential pulsar-black-hole systems). In the revised version we will insert a concise parenthetical reference to these works in the abstract and will add a short clarifying sentence in the main text that points the reader to the relevant discovery-rate calculations. This addresses the load-bearing nature of the claim without requiring new computations within the present review. revision: yes
Circularity Check
No significant circularity: forward-looking review without derivations or fitted predictions
full rationale
The paper is a science-case review outlining prospective gravity tests enabled by future SKA pulsar timing. It contains no equations, no fitted parameters, no predictions derived from internal data, and no self-citation chains that reduce the central claims to prior author work by construction. Claims rest on external assumptions about SKA sensitivity and discovery yields rather than any load-bearing derivation that collapses to its own inputs. This matches the default expectation for non-circular papers; the reader's assessment of score 1.0 is consistent with the absence of any of the enumerated circularity patterns.
Assumptions & free parameters
Cite this review
Pith. "Pith review of Testing Gravity with Binary Pulsars in the SKA Era." pith.science (2026). https://pith.science/paper/JEFIEZN7
@misc{pith2026260702064,
author = {Pith},
title = {Pith review of: Testing Gravity with Binary Pulsars in the SKA Era},
year = {2026},
howpublished = {\url{https://pith.science/paper/JEFIEZN7}},
note = {Machine review of arXiv:2607.02064}
}
read the original abstract
Binary (and trinary) radio pulsars are natural laboratories in space for understanding gravity in the strong field regime, with many unique and precise tests carried out so far, including the most precise tests of the strong equivalence principle and of the radiative properties of gravity. The Square Kilometre Array (SKA) telescope, with its high sensitivity in the Southern Hemisphere, will vastly improve the timing precision of recycled pulsars, allowing for a deeper search of potential deviations from general relativity (GR) in currently known systems. A Galactic census of pulsars will, in addition, will yield the discovery of dozens of relativistic pulsar systems, including potentially pulsar -- black hole binaries, which can be used to test the cosmic censorship hypothesis and the ``no-hair'' theorem. Aspects of gravitation to be explored include tests of strong equivalence principles, gravitational dipole radiation, extra field components of gravitation, gravitomagnetism, and spacetime symmetries. In this chapter, we describe the kinds of gravity tests possible with binary pulsar and outline the features and abilities that SKA must possess to best contribute to this science.
Figures
Figures from the paper (6 more)
Reference graph
Works this paper leans on
-
[1]
Abbate, F. et al.. 2026, in Advancing Astrophysics with the SKA – II (AASKAII), arXiv search: Report number AASKAII/Abbate01
work page 2026
- [2]
-
[3]
Antoniadis, J. et al.. 2013, Science, 340, 448
work page 2013
-
[4]
Archibald, A. M. et al.. 2018, Nature, 559, 73
work page 2018
-
[5]
Baade, W. & Zwicky, F. 1934, Proceedings of the National Academy of Science, 20, 259
work page 1934
-
[6]
Babichev, E. & Deffayet, C. 2013, Classical and Quantum Gravity, 30, 184001
work page 2013
-
[7]
Bagchi, M. et al.. 2026, in Advancing Astrophysics with the SKA – II (AASKAII), arXiv search: Report number AASKAII/Bagchi01
work page 2026
- [8]
Show all 114 references
-
[9]
Barr, E. D. et al.. 2024, Science, 383, 275
2024
-
[10]
Basu, A. et al. . 2026, in Advancing Astrophysics with the SKA – II (AASKAII), arXiv search: Report number AASKAII/AvishekBasu01
2026
-
[11]
Batrakov, A. et al.. 2024, A&A, 686, A101
2024
-
[12]
& Hackmann, E
Ben-Salem, B. & Hackmann, E. 2022, MNRAS, 516, 1768 31 Testing Gravity with Binary Pulsars Venkatraman Krishnan, Shao et al
2022
-
[13]
Berti, E. et al.. 2015, Classical and Quantum Gravity, 32, 243001
2015
-
[14]
Bertotti, B. et al.. 2003, Nature, 425, 374
2003
-
[15]
& Teukolsky, S
Blandford, R. & Teukolsky, S. A. 1976, ApJ, 205, 580
1976
-
[16]
P .et al
Breton, R. P .et al.. 2008, Science, 321, 104
2008
-
[17]
Burgay, M. et al.. 2003, Nature, 426, 531
2003
-
[18]
Chatterjee, S. et al.. 2009, ApJ, 698, 250
2009
-
[19]
Cordes, J. M. et al.. 2004, New Astron. Rev., 48, 1413
2004
-
[20]
& East, W
Corman, M. & East, W. E. 2024, Phys. Rev. D, 110, 084065
2024
-
[21]
& Deruelle, N
Damour, T. & Deruelle, N. 1986, Annales de L ’Institut Henri Poincare Section (A) Physique The- orique, 44, 263
1986
-
[22]
& Esposito-Farese, G
Damour, T. & Esposito-Farese, G. 1992, Phys. Rev. D, 46, 4128
1992
-
[23]
& Esposito-Farèse, G
Damour, T. & Esposito-Farèse, G. 1992, Phys. Rev. D, 46, 4128
1992
-
[24]
& Esposito-Farese, G
Damour, T. & Esposito-Farese, G. 1993, Phys. Rev. Let., 70, 2220
1993
-
[25]
& Schäfer, G
Damour, T. & Schäfer, G. 1991, Journal of Mathematical Physics, 32, 127
1991
-
[26]
& Taylor, J
Damour, T. & Taylor, J. H. 1991, ApJ, 366, 501 —. 1992, Phys. Rev. D, 45, 1840 de Rham, C. et al.. 2017, Reviews of Modern Physics, 89, 025004 —. 2013, Phys. Rev. D, 87, 044025 de Rham, C. et al.. 2013, Physical Review D, 87, 044025
1991
-
[27]
Deller, A. T. et al.. 2019, ApJ, 875, 100
2019
-
[28]
Desvignes, G. et al.. 2019, Science, 365, 1013
2019
-
[29]
Ding, H. et al.. 2023, MNRAS, 519, 4982
2023
-
[30]
Doneva, D. D. & Y azadjiev, S. S. 2016, JCAP , 11, 019
2016
-
[31]
Doroshenko, O. V . & Kopeikin, S. M. 1995, MNRAS, 274, 1029
1995
-
[32]
Eardley, D. M. 1975, ApJL, 196, L59
1975
-
[33]
Edwards, R. T. et al.. 2006, MNRAS, 372, 1549
2006
-
[34]
1915, Sitzungsberichte der Königlich Preussischen Akademie der Wis- senschaften, 844 Event Horizon Telescope Collaboration
Einstein, A. 1915, Sitzungsberichte der Königlich Preussischen Akademie der Wis- senschaften, 844 Event Horizon Telescope Collaboration. 2019, The Astrophysical Journal Letters, 875, L1 —. 2022, The Astrophysical Journal Letters, 930, L12 32 Testing Gravity with Binary Pu...
1915
-
[35]
Everitt, C. W. F. et al.. 2011, Phys. Rev. Lett., 106, 221101 Faucher-Giguère, C.-A. & Loeb, A. 2011, MNRAS, 415, 3951
2011
-
[36]
Ferdman, R. D. et al.. 2020, Nature, 583, 211
2020
-
[37]
Finn, L. S. & Sutton, P . J. 2002, Phys. Rev. D, 65, 044022
2002
-
[38]
Fonseca, E. et al.. 2014, ApJ, 787, 82
2014
-
[39]
Freire, P . C. C. & Wex, N. 2024, Living Reviews in Relativity, 27, 5
2024
-
[40]
J.et al
Guo, Y . J.et al.. 2021, A&A, 654, A16
2021
-
[41]
Gupta, T. et al.. 2021, Class. Quant. Grav., 38, 195003
2021
-
[42]
& Müller, J
Hofmann, F. & Müller, J. 2018, Classical and Quantum Gravity, 35, 035015
2018
-
[43]
Hu, H. et al.. 2022, A&A, 667, A149
2022
-
[44]
Hu, H. et al.. 2020, Mon. Not. Roy. Astron. Soc., 497, 3118
2020
-
[45]
Hulse, R. A. & Taylor, J. H. 1975, ApJL, 195, L51 Julié, F.-L. et al.. 2025, Phys. Rev. D, 111, 024016
1975
-
[46]
Kleihaus, B. et al.. 2016, Phys. Rev. D, 93, 064077
2016
-
[47]
Kopeikin, S. M. & Schäfer, G. 1999, Phys. Rev. D, 60, 124002
1999
-
[48]
Kramer, M. et al.. 2004, New Astron. Rev., 48, 993 —. 2006, Science, 314, 97 —. 2021, Physical Review X, 11, 041050
2004
-
[49]
& Wex, N
Kramer, M. & Wex, N. 2009, Classical and Quantum Gravity, 26, 073001
2009
-
[50]
Kulkarni, S. R. et al.. 1993, Nature, 364, 421
1993
-
[51]
Kyutoku, K. et al.. 2019, MNRAS, 483, 2615
2019
-
[52]
& Rafikov, R
Lai, D. & Rafikov, R. R. 2005, ApJL, 621, L41
2005
-
[53]
Lau, M. Y . M.et al.. 2020, MNRAS, 492, 3061
2020
-
[54]
2016, ApJ, 831, 150
Lazarus, P .et al.. 2016, ApJ, 831, 150
2016
-
[55]
& Thirring, H
Lense, J. & Thirring, H. 1918, Physikalische Zeitschrift, 19, 156
1918
-
[56]
Liu, K. et al.. 2014, MNRAS, 445, 3115
2014
-
[57]
Liu, K. et al.. 2014, Mon. Not. Roy. Astron. Soc., 445, 3115 33 Testing Gravity with Binary Pulsars Venkatraman Krishnan, Shao et al
2014
-
[58]
Liu, K. et al.. 2020, MNRAS, 499, 2276
2020
-
[59]
Lorimer, D. R. 2005, Living Reviews in Relativity, 8, 7
2005
-
[60]
Lorimer, D. R. & Kramer, M. 2005, Handbook of Pulsar Astronomy, Vol. 4
2005
-
[61]
Lower, M. E. et al.. 2024, A&A, 682, A26
2024
-
[62]
Lyne, A. G. et al.. 2004, Science, 303, 1153
2004
-
[63]
Meng, L. et al.. 2025, A&A, 704, A153
2025
-
[64]
Miao, X. et al.. 2019, Phys. Rev. D, 99, 123015 —. 2021, ApJ, 921, 114 —. 2020, ApJ, 898, 69
2019
-
[65]
Misner, C. W. et al.. 1973, Gravitation
1973
-
[66]
Nicolis, A. et al.. 2009, Phys. Rev. D, 79, 064036
2009
-
[67]
1968, Physical Review, 169, 1014 —
Nordtvedt, K. 1968, Physical Review, 169, 1014 —. 1987, ApJ, 320, 871
1968
-
[68]
Oppenheimer, J. R. & Volkoff, G. M. 1939, Physical Review, 55, 374
1939
-
[69]
Oswald, L. S. et al.. 2025, submitted
2025
-
[70]
2011, Phys
Pani, P .et al.. 2011, Phys. Rev. D, 84, 104035
2011
-
[71]
1979, in General Relativity: An Einstein centenary survey, ed
Penrose, R. 1979, in General Relativity: An Einstein centenary survey, ed. S. W. Hawking & W. Is- rael, Vol. 1 (Cambridge; New Y ork: Cambridge University Press), 581–638
1979
-
[72]
Peters, P . C. 1964, Physical Review, 136, 1224
1964
-
[73]
Pfahl, E. et al.. 2005, AJ, 628, 343
2005
-
[74]
Ransom, S. M. et al.. 2003, ApJ, 589, 911 —. 2014, Nature, 505, 520
2003
-
[75]
Ridolfi, A. et al.. 2022, A&A, 664, A27
2022
-
[76]
Saffer, A. et al.. 2025, ApJL, 983, L20 Sänger, E. M. et al.. 2026, Phys. Rev. D, 113, 084070
2025
-
[77]
2017, ApJL, 848, L15
Savchenko, V .et al.. 2017, ApJL, 848, L15
2017
-
[78]
Schiff, L. I. 1960, Phys. Rev. Lett., 4, 215
1960
-
[79]
1990, A&A, 232, 62 34 Testing Gravity with Binary Pulsars Venkatraman Krishnan, Shao et al
Schneider, J. 1990, A&A, 232, 62 34 Testing Gravity with Binary Pulsars Venkatraman Krishnan, Shao et al
1990
-
[80]
& Y agi, K
Seymour, B. & Y agi, K. 2018, Phys. Rev. D, 98, 124007
2018
-
[81]
Shao, L. et al.. 2013, Classical and Quantum Gravity, 30, 165019
2013
-
[82]
Shao, L. et al.. 2017, Phys. Rev. X, 7, 041025
2017
-
[83]
Shao, L. et al.. 2015, in Advancing Astrophysics with the Square Kilometre Array (AASKA14), 42
2015
-
[84]
& Wex, N
Shao, L. & Wex, N. 2012, Class. Quant. Grav., 29, 215018
2012
-
[85]
& Wex, N
Shao, L. & Wex, N. 2012, Classical and Quantum Gravity, 29, 21.5018 —. 2013, Classical and Quantum Gravity, 30, 165020
2012
-
[86]
Shao, L. et al.. 2015, in 13th Marcel Grossmann Meeting on Recent Developments in Theoretical and Experimental General Relativity, Astrophysics, and Relativistic Field Theories, 1704–1706
2015
-
[87]
Shao, L. et al.. 2018, Phys. Rev. Lett., 120, 241104
2018
-
[88]
Shao, L. et al.. 2020, Phys. Rev. D, 102, 024069
2020
-
[89]
Shapiro, I. I. 1964, Phys. Rev. Let., 13, 789
1964
-
[90]
Silva, H. O. et al.. 2021, Phys. Rev. Lett., 126, 181101
2021
-
[91]
Sipior, M. S. et al.. 2004, MNRAS, 354, L49
2004
-
[92]
2023, SKAO staged delivery, array assemblies and layouts, Report SKAO-TEL- 0002299, SKA Observatory (SKAO)
Sridhar, S. 2023, SKAO staged delivery, array assemblies and layouts, Report SKAO-TEL- 0002299, SKA Observatory (SKAO)
2023
-
[93]
Stairs, I. H. et al.. 2004, Phys. Rev. Lett., 93, 141101
2004
-
[94]
Stovall, K. et al.. 2018, ApJL, 854, L22
2018
-
[95]
Taylor, J. H. et al.. 1979, Nature, 277, 437
1979
-
[96]
Taylor, J. H. & Weisberg, J. M. 1982, ApJ, 253, 908 —. 1989, ApJ, 345, 434
1982
-
[97]
Thrane, E. et al.. 2020, MNRAS, 493, 5408
2020
-
[98]
Tolman, R. C. 1939, Physical Review, 55, 364 Venkatraman Krishnan, V .et al.. 2020, Science, 367, 577
1939
-
[99]
Voisin, G. et al.. 2020, A&A, 638, A24 —. 2024, arXiv e-prints, arXiv:2411.10066
2020
-
[100]
& Tauris, T
Voss, R. & Tauris, T. M. 2003, MNRAS, 342, 1169
2003
-
[101]
& Zhao, Z.-C
Wang, S. & Zhao, Z.-C. 2024, Phys. Rev. D, 109, L061502
2024
-
[102]
Watts, A. et al.. 2015, in Advancing Astrophysics with the Square Kilometre Array (AASKA14), 43 35 Testing Gravity with Binary Pulsars Venkatraman Krishnan, Shao et al
2015
-
[103]
Weisberg, J. M. & Huang, Y . 2016, ApJ, 829, 55
2016
-
[104]
& Kopeikin, S
Wex, N. & Kopeikin, S. 1999, ApJ, 513, 388
1999
-
[105]
& Kopeikin, S
Wex, N. & Kopeikin, S. M. 1999, ApJ, 514, 388
1999
-
[106]
& Kramer, M
Wex, N. & Kramer, M. 2007, MNRAS, 380, 455 —. 2020, Universe, 6, 156
2007
-
[107]
Will, C. M. 1993, Theory and Experiment in Gravitational Physics —. 2018, Theory and Experiment in Gravitational Physics
1993
-
[108]
Will, C. M. 2018, Theory and Experiment in Gravitational Physics (Cambridge University Press)
2018
-
[109]
Will, C. M. & Nordtvedt, Jr., K. 1972, ApJ, 177, 757
1972
-
[110]
Xu, R. et al.. 2020, Phys. Rev. D, 102, 064057 Y agi, K.et al.. 2014a, Phys. Rev. D, 89, 084067, [Erratum: Phys.Rev.D 90, 069902 (2014), Erratum: Phys.Rev.D 90, 069901 (2014)] —. 2014b, Phys. Rev. Lett., 112, 161101 —. 2016, Phys. Rev. D, 93, 024010 —. 2013, Phys. Rev. D, 87, ...
2020
-
[111]
& Spergel, D
Yunes, N. & Spergel, D. N. 2009, Phys. Rev. D, 80, 042004
2009
- [112]
-
[113]
Zhao, J. et al.. 2022, Classical and Quantum Gravity, 39, 11LT01
2022
-
[114]
Zhu, W. W. et al.. 2019, Mon. Not. Roy. Astron. Soc., 482, 3249 36
2019
Reviewed July 3, 2026 · model on record in the stance chip above.
Discussion (0). Sign in to comment.