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Testing the nature of compact objects in the lower mass gap using gravitational wave observations

N. V. Krishnendu1,2,*, Frank Ohme3,†, and K. G. Arun4,‡

  • *Contact author: k.naderivarium@bham.ac.uk
  • †Contact author: frank.ohme@aei.mpg.de
  • ‡Contact author: kgarun@cmi.ac.in
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Phys. Rev. D 112, 123038 – Published 22 December, 2025

DOI: https://doi.org/10.1103/rxdd-hq82

Abstract

As the compact binary catalog continues to grow rapidly, developing and refining tests to probe the nature of compact objects is essential for a comprehensive understanding of both the observed data and the underlying astrophysics of the binary population. We investigate the effectiveness of spin-induced multipole moments (SIQM) and tidal deformability measurements in distinguishing lower mass-gap black hole (BH) binaries from non-BH binaries with different mass and spin configurations. We perform model-agnostic tests on binary BH (BBH) simulations using full Bayesian inference, evaluating the independent and joint measurability of SIQM and tidal parameters across the parameter space. We extend the analysis to simulations of self-interacting spinning boson stars, using synthetic signals that exhibit (a) both SIQM and tidal effects and (b) each effect individually. For case (a), recovery is performed using (i) a BBH model, (ii) a model incorporating both SIQM and tidal effects, and (iii) models including either SIQM or tidal effects. For case (b), we employ (i) a BBH model and (ii) models incorporating either SIQM or tidal effects, consistent with the injection. Simulations assume binaries of total mass of 8M⊙, varying mass ratios and spin magnitudes, using the inspiral-only taylorf2 waveform model. A three-detector network consists of Advanced LIGO and Virgo at design sensitivity is assumed, with results scalable to future detector sensitivities. We find that employing an incorrect model to analyze the signal can lead to severe biases in parameter inference. Notably, when analyzing a simulated binary boson starlike signal with component masses (4,4)M⊙ using a BBH model, the system is incorrectly identified as having masses (8,2)M⊙. In contrast, using the correct recovery model that includes both SIQM and tidal deformability effects, successfully recovers the true masses, highlighting the significance of waveform model accuracy in performing reliable distinguishability tests for compact objects in the low-mass gap.

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References (108)

  1. A. G. Abac et al. (LIGO Scientific Collaboration, VIRGO Collaboration, and KAGRA Collaboration), arXiv:2508.18082.
  2. R. Abbott et al. (LIGO Scientific Collaboration, VIRGO Collaboration, and KAGRA Collaboration), Phys. Rev. X 13, 041039 (2023).
  3. R. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration), Phys. Rev. X 11, 021053 (2021).
  4. LIGO Scientific Collaboration and Virgo Collaboration, Gravitational wave candidate event database (gracedb), https://gracedb.ligo.org/ (2024).
  5. A. H. Nitz, C. D. Capano, S. Kumar, Y.-F. Wang, S. Kastha, M. Schäfer, R. Dhurkunde, and M. Cabero, Astrophys. J. 922, 76 (2021).
  6. D. Wadekar, T. Venumadhav, J. Roulet, A. K. Mehta, B. Zackay, J. Mushkin, and M. Zaldarriaga, Phys. Rev. D 110, 044063 (2024).
  7. http://www.ligo.caltech.edu
  8. J. Aasi et al. (LIGO Scientific Collaboration), Classical Quantum Gravity 32, 074001 (2015).
  9. F. Acernese et al. (VIRGO Collaboration), Classical Quantum Gravity 32, 024001 (2015).
  10. B. Iyer et al., LIGO-India Technical Report No. LIGO-M1100296 (2011), https://dcc.ligo.org/ligo-m1100296/public.
  11. M. Evans et al., arXiv:2306.13745.
  12. M. Branchesi et al., J. Cosmol. Astropart. Phys. 07 (2023) 068.
  13. http://lisa.jpl.nasa.gov
  14. R. Abbott, T. D. Abbott et al., Astrophys. J. Lett. 896, L44 (2020).
  15. A. G. Abac et al. (LIGO ScientificCollaboration, KAGRACollaboration, and VIRGO Collaboration), Astrophys. J. Lett. 970, L34 (2024).
  16. A. Gupta, D. Gerosa, K. G. Arun, E. Berti, W. M. Farr, and B. S. Sathyaprakash, Phys. Rev. D 101, 103036 (2020).
  17. P. Mahapatra, D. Chattopadhyay, A. Gupta, F. Antonini, M. Favata, B. S. Sathyaprakash, and K. G. Arun, Phys. Rev. D 111, 123030 (2025).
  18. T. B. Littenberg, B. Farr, S. Coughlin, V. Kalogera, and D. E. Holz, Astrophys. J. Lett. 807, L24 (2015).
  19. J. Cotturone, M. Zevin, and S. Biscoveanu, arXiv:2507.01189.
  20. N. K. Johnson-Mcdaniel, A. Mukherjee, R. Kashyap, P. Ajith, W. Del Pozzo, and S. Vitale, Phys. Rev. D 102, 123010 (2020).
  21. N. V. Krishnendu, K. G. Arun, and C. K. Mishra, Phys. Rev. Lett. 119, 091101 (2017).
  22. S. Datta, K. S. Phukon, and S. Bose, Phys. Rev. D 104, 084006 (2021).
  23. V. Cardoso, E. Franzin, and P. Pani, Phys. Rev. Lett. 116, 171101 (2016).
  24. V. Cardoso, E. Franzin, A. Maselli, P. Pani, and G. Raposo, arXiv:1701.01116.
  25. V. Cardoso, E. Franzin, A. Maselli, P. Pani, and G. Raposo, Phys. Rev. D 95, 084014 (2017); 95, 089901(A) (2017).
  26. E. Berti and V. Cardoso, Int. J. Mod. Phys. D 15, 2209 (2006).
  27. E. E. Flanagan and T. Hinderer, Phys. Rev. D 77, 021502 (2008).
  28. S. Ghosh and M. Hannam, Phys. Rev. D 112, 104017 (2025).
  29. E. Poisson, Phys. Rev. D 57, 5287 (1998).
  30. C. K. Mishra, A. Kela, K. G. Arun, and G. Faye, Phys. Rev. D 93, 084054 (2016).
  31. A. Bohé, G. Faye, S. Marsat, and E. K. Porter, Classical Quantum Gravity 32, 195010 (2015).
  32. S. Marsat, Classical Quantum Gravity 32, 085008 (2015).
  33. S. Marsat, Classical Quantum Gravity 32, 085008 (2015).
  34. N. V. Krishnendu, M. Saleem, A. Samajdar, K. G. Arun, W. Del Pozzo, and C. K. Mishra, Phys. Rev. D 100, 104019 (2019).
  35. R. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration), Phys. Rev. X 11, 021053 (2021).
  36. R. Abbott et al. (LIGO Scientifi Collaborationc, VIRGO Collaboration, and KAGRA Collaboration), Phys. Rev. X 13, 041039 (2023).
  37. F. Ryan, Phys. Rev. D 56, 1845 (1997).
  38. C. Pacilio, M. Vaglio, A. Maselli, and P. Pani, Phys. Rev. D 102, 083002 (2020).
  39. G. Pappas and T. A. Apostolatos, Phys. Rev. Lett. 108, 231104 (2012).
  40. N. Uchikata and S. Yoshida, Classical Quantum Gravity 33, 025005 (2016).
  41. T. Hinderer, Astrophys. J. 677, 1216 (2008); 697, 964(E) (2009).
  42. J. Vines, E. E. Flanagan, and T. Hinderer, Phys. Rev. D 83, 084051 (2011).
  43. E. E. Flanagan and T. Hinderer, Phys. Rev. D 77, 021502 (2008).
  44. N. Sennett, T. Hinderer, J. Steinhoff, A. Buonanno, and S. Ossokine, Phys. Rev. D 96, 024002 (2017).
  45. J. Vines, E. E. Flanagan, and T. Hinderer, Phys. Rev. D 83, 084051 (2011).
  46. T. Damour, A. Nagar, and L. Villain, Phys. Rev. D 85, 123007 (2012).
  47. B. P. Abbott et al. (Virgo Collaboration and LIGO Scientific Collaboration), Phys. Rev. Lett. 119, 161101 (2017).
  48. G. Castro, L. Gualtieri, A. Maselli, and P. Pani, Phys. Rev. D 106, 024011 (2022).
  49. T. Abdelsalhin, L. Gualtieri, and P. Pani, Phys. Rev. D 98, 104046 (2018).
  50. K. Alvi, Phys. Rev. D 64, 104020 (2001).
  51. T. Narikawa, N. Uchikata, and T. Tanaka, Phys. Rev. D 104, 084056 (2021).
  52. N. Uchikata and T. Narikawa, Phys. Rev. D 104, 024059 (2021).
  53. F. D. Ryan, Phys. Rev. D 55, 6081 (1997).
  54. M. Vaglio, C. Pacilio, A. Maselli, and P. Pani, Phys. Rev. D 105, 124020 (2022).
  55. M. Vaglio, C. Pacilio, A. Maselli, and P. Pani, Phys. Rev. D 108, 023021 (2023).
  56. R. Abbott et al. (LIGO Scientific Collaboration and VIRGO Collaboration), Phys. Rev. D 109, 022001 (2024).
  57. R. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration), Phys. Rev. D 102, 043015 (2020).
  58. B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration), Astrophys. J. Lett. 892, L3 (2020).
  59. R. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration), Phys. Rev. Lett. 125, 101102 (2020).
  60. M. Hannam et al., Nature (London) 610, 652 (2022).
  61. G. Morras, G. Pratten, and P. Schmidt, arXiv:2503.15393.
  62. A. G. Abac et al. (LIGO Scientific Collaboration, Virgo Collaboration, KAGRA Collaboration, and VIRGO Collaboration), Astrophys. J. Lett. 970, L34 (2024).
  63. K. Chandra, I. Gupta, R. Gamba, R. Kashyap, D. Chattopadhyay, A. Gonzalez, S. Bernuzzi, and B. S. Sathyaprakash, Astrophys. J. 977, 167 (2024).
  64. J. Janquart et al., arXiv:2409.07298.
  65. M. H. P. M. van Putten, M. Aghaei Abchouyeh, and M. Della Valle, Astrophys. J. Lett. 972, L23 (2024).
  66. C. S. Ye, K. Kremer, S. M. Ransom, and F. A. Rasio, Astrophys. J. 975, 77 (2024).
  67. R. Matur, I. Hawke, and N. Andersson, Mon. Not. R. Astron. Soc. 534, 2894 (2024).
  68. K. Chatziioannou, H. T. Cromartie, S. Gandolfi, I. Tews, D. Radice, A. W. Steiner, and A. L. Watts, arXiv:2407.11153.
  69. F.-L. Julié, L. Pompili, and A. Buonanno, Phys. Rev. D 111, 024016 (2025).
  70. B. Gao, S.-P. Tang, H.-T. Wang, J. Yan, and Y.-Z. Fan, Phys. Rev. D 110, 044022 (2024).
  71. S. Bhattacharya, S. Kapadia, and B. Dasgupta, arXiv:2507.15951.
  72. E. M. Sänger et al., arXiv:2406.03568.
  73. K. Jedamzik, Phys. Rev. Lett. 126, 051302 (2021).
  74. I. Tews, P. T. H. Pang, T. Dietrich, M. W. Coughlin, S. Antier, M. Bulla, J. Heinzel, and L. Issa, Astrophys. J. Lett. 908, L1 (2021).
  75. M. Fasano, K. W. K. Wong, A. Maselli, E. Berti, V. Ferrari, and B. S. Sathyaprakash, Phys. Rev. D 102, 023025 (2020).
  76. N.-B. Zhang and B.-A. Li, Astrophys. J. 902, 38 (2020).
  77. A. Chen, N. K. Johnson-McDaniel, T. Dietrich, and R. Dudi, Phys. Rev. D 101, 103008 (2020).
  78. A. G. Abac et al. (LIGO Scientific Collaboration, Virgo Collaboration, KAGRA Collaboration, and VIRGO Collaboration), Astrophys. J. Lett. 970, L34 (2024).
  79. M. Colpi, S. L. Shapiro, and I. Wasserman, Phys. Rev. Lett. 57, 2485 (1986).
  80. N. Uchikata, S. Yoshida, and P. Pani, Phys. Rev. D 94, 064015 (2016).
  81. S. Marsat, Classical Quantum Gravity 32, 085008 (2015).
  82. A. Buonanno, G. Faye, and T. Hinderer, Phys. Rev. D 87, 044009 (2013).
  83. K. G. Arun, A. Buonanno, G. Faye, and E. Ochsner, Phys. Rev. D 79, 104023 (2009).
  84. L. Kidder, Phys. Rev. D 52, 821 (1995).
  85. S. Marsat, A. Bohe, G. Faye, and L. Blanchet, Classical Quantum Gravity 30, 055007 (2013).
  86. A. Bohe, S. Marsat, G. Faye, and L. Blanchet, Classical Quantum Gravity 30, 075017 (2013).
  87. A. Bohé, S. Marsat, and L. Blanchet, Classical Quantum Gravity 30, 135009 (2013).
  88. S. Marsat, A. Bohé, L. Blanchet, and A. Buonanno, Classical Quantum Gravity 31, 025023 (2014).
  89. C. K. Mishra, A. Kela, K. G. Arun, and G. Faye, Phys. Rev. D 93, 084054 (2016).
  90. A. Buonanno, B. R. Iyer, E. Ochsner, Y. Pan, and B. S. Sathyaprakash, Phys. Rev. D 80, 084043 (2009).
  91. N. V. Krishnendu, C. K. Mishra, and K. G. Arun, Phys. Rev. D 99, 064008 (2019).
  92. B. D. Lackey, K. Kyutoku, M. Shibata, P. R. Brady, and J. L. Friedman, Phys. Rev. D 89, 043009 (2014).
  93. F. Pannarale, E. Berti, K. Kyutoku, B. D. Lackey, and M. Shibata, Phys. Rev. D 92, 084050 (2015).
  94. M. Agathos, J. Meidam, W. Del Pozzo, T. G. F. Li, M. Tompitak, J. Veitch, S. Vitale, and C. Van Den Broeck, Phys. Rev. D 92, 023012 (2015).
  95. T. Damour, B. R. Iyer, and B. S. Sathyaprakash, Phys. Rev. D 62, 084036 (2000).
  96. T. Damour, B. R. Iyer, and B. S. Sathyaprakash, Phys. Rev. D 63, 044023 (2001); 72, 029902(E) (2005).
  97. T. Damour, B. R. Iyer, and B. S. Sathyaprakash, Phys. Rev. D 66, 027502 (2002); 66, 027502(E) (2002).
  98. B. Carter, Phys. Rev. Lett. 26, 331 (1971).
  99. R. O. Hansen, J. Math. Phys. (N.Y.) 15, 46 (1974).
  100. LIGO Scientific, Virgo, and KARGA Collaborations, LVK Algorithm Library - LALSuite, Free software (GPL) (2018), 10.7935/GT1W-FZ16.
  101. G. Ashton et al., Astrophys. J. Suppl. Ser. 241, 27 (2019).
  102. R. J. E. Smith, G. Ashton, A. Vajpeyi, and C. Talbot, Mon. Not. R. Astron. Soc. 498, 4492 (2020).
  103. J. S. Speagle, Mon. Not. R. Astron. Soc. 493, 3132 (2020).
  104. M. Favata, C. Kim, K. G. Arun, J. Kim, and H. W. Lee, Phys. Rev. D 105, 023003 (2022).
  105. S. Husa, S. Khan, M. Hannam, M. Pürrer, F. Ohme, X. Jiménez Forteza, and A. Bohé, Phys. Rev. D 93, 044006 (2016).
  106. A. Ori and K. S. Thorne, Phys. Rev. D 62, 124022 (2000).
  107. A. J. K. Chua and M. Vallisneri, Phys. Rev. Lett. 124, 041102 (2020).
  108. R. Abbott et al. (LIGO Scientific Collaboration, KAGRA Collaboration, and VIRGO Collaboration), Astrophys. J. Lett. 915, L5 (2021).

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Phys. Rev. D 112, 123038– Published 22 December, 2025
  • Received 18 September 2025
  • Accepted 24 November 2025
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