Where are Gaia's small black holes?
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arXiv
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| Autori principali: | , , , |
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| Natura: | Preprint |
| Pubblicazione: |
2025
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| _version_ | 1866914456817106944 |
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| author | Fishbach, M. Breivik, K. Willcox, R. van Son, L. A. C |
| author_facet | Fishbach, M. Breivik, K. Willcox, R. van Son, L. A. C |
| contents | Gaia has recently revealed a population of over 20 compact objects in wide astrometric binaries, while LIGO-Virgo-KAGRA (LVK) have observed around 100 compact object binaries as gravitational-wave (GW) mergers. Despite belonging to different systems, the compact objects discovered by both Gaia and the LVK follow a multimodal mass distribution, with a global maximum at neutron star (NS) masses ($\sim 1$-$2\,M_\odot$) and a secondary local maximum at black hole (BH) masses $\sim10\,M_\odot$. However, the relative dearth of objects, or ``mass gap," between these modes is more pronounced among the wide binaries observed by Gaia compared to the GW population, with $9^{+10}_{-6}\%$ of GW component masses falling between $2.5$--$5\,M_\odot$ compared to $\lesssim5\%$ of Gaia compact objects. We explore whether this discrepancy can be explained by the natal kicks received by low-mass BHs. GW progenitor binaries may be more likely to survive natal kicks, because the newborn BH has a more massive companion and/or is in a tighter binary than Gaia progenitor binaries. We compare the survival probabilities of Gaia and GW progenitor binaries as a function of natal kick strength and pre-supernova binary parameters, and map out the parameter space and kick strength required to disrupt the progenitor binaries leading to low-mass BHs in Gaia systems more frequently than those in GW systems. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2508_08986 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Where are Gaia's small black holes? Fishbach, M. Breivik, K. Willcox, R. van Son, L. A. C High Energy Astrophysical Phenomena Astrophysics of Galaxies General Relativity and Quantum Cosmology Gaia has recently revealed a population of over 20 compact objects in wide astrometric binaries, while LIGO-Virgo-KAGRA (LVK) have observed around 100 compact object binaries as gravitational-wave (GW) mergers. Despite belonging to different systems, the compact objects discovered by both Gaia and the LVK follow a multimodal mass distribution, with a global maximum at neutron star (NS) masses ($\sim 1$-$2\,M_\odot$) and a secondary local maximum at black hole (BH) masses $\sim10\,M_\odot$. However, the relative dearth of objects, or ``mass gap," between these modes is more pronounced among the wide binaries observed by Gaia compared to the GW population, with $9^{+10}_{-6}\%$ of GW component masses falling between $2.5$--$5\,M_\odot$ compared to $\lesssim5\%$ of Gaia compact objects. We explore whether this discrepancy can be explained by the natal kicks received by low-mass BHs. GW progenitor binaries may be more likely to survive natal kicks, because the newborn BH has a more massive companion and/or is in a tighter binary than Gaia progenitor binaries. We compare the survival probabilities of Gaia and GW progenitor binaries as a function of natal kick strength and pre-supernova binary parameters, and map out the parameter space and kick strength required to disrupt the progenitor binaries leading to low-mass BHs in Gaia systems more frequently than those in GW systems. |
| title | Where are Gaia's small black holes? |
| topic | High Energy Astrophysical Phenomena Astrophysics of Galaxies General Relativity and Quantum Cosmology |
| url | https://arxiv.org/abs/2508.08986 |