Hidden binaries in star-forming regions
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arXiv
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| Format: | Preprint |
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2025
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| _version_ | 1866909698384461824 |
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| author | Rawcliffe, Mary H. Griffiths-Janvier, Nathan Parker, Richard J. |
| author_facet | Rawcliffe, Mary H. Griffiths-Janvier, Nathan Parker, Richard J. |
| contents | A significant fraction of, and possibly all, stars form in binary or multiple systems. For Solar-mass stars in the Galactic field, the distribution of orbital separations is log-normal over seven orders of magnitude, from $10^{-2} - 10^5$ au. In contrast, the separation distributions of systems in nearby star-forming regions paints a much more confusing picture. There appears to be an excess of systems in the separation range 10 - 1000 au, and recent high-resolution spectroscopic observations of close (<10 au) systems suggest a field-like distribution in some star-forming regions, but a possible excess with respect to the field in other regions. Furthermore, the resolution limit of numerical simulations of binary star formation is $\sim$1\,au, and consequently comparisons with the binary distributions in star-forming regions and in the field are restricted. In this paper, we demonstrate that these observational uncertainties, and limitations in the simulations, are potentially a much bigger problem than previously realised. We show that the log-normal separation distribution in the field can be reproduced by combining constituent binary populations whose initial separation distributions have a very different form to a log-normal. We also argue that the observed excess of binaries in the range 10 - 62 au in the ONC compared to the Galactic field is not necessarily inconsistent with the field population, because the ONC is only one of many star-forming regions that populate the field. We propose that further observations of spectroscopic binaries in star-forming regions to probe and complete the <10 au parameter space are urgently needed. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2507_15924 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Hidden binaries in star-forming regions Rawcliffe, Mary H. Griffiths-Janvier, Nathan Parker, Richard J. Solar and Stellar Astrophysics Astrophysics of Galaxies A significant fraction of, and possibly all, stars form in binary or multiple systems. For Solar-mass stars in the Galactic field, the distribution of orbital separations is log-normal over seven orders of magnitude, from $10^{-2} - 10^5$ au. In contrast, the separation distributions of systems in nearby star-forming regions paints a much more confusing picture. There appears to be an excess of systems in the separation range 10 - 1000 au, and recent high-resolution spectroscopic observations of close (<10 au) systems suggest a field-like distribution in some star-forming regions, but a possible excess with respect to the field in other regions. Furthermore, the resolution limit of numerical simulations of binary star formation is $\sim$1\,au, and consequently comparisons with the binary distributions in star-forming regions and in the field are restricted. In this paper, we demonstrate that these observational uncertainties, and limitations in the simulations, are potentially a much bigger problem than previously realised. We show that the log-normal separation distribution in the field can be reproduced by combining constituent binary populations whose initial separation distributions have a very different form to a log-normal. We also argue that the observed excess of binaries in the range 10 - 62 au in the ONC compared to the Galactic field is not necessarily inconsistent with the field population, because the ONC is only one of many star-forming regions that populate the field. We propose that further observations of spectroscopic binaries in star-forming regions to probe and complete the <10 au parameter space are urgently needed. |
| title | Hidden binaries in star-forming regions |
| topic | Solar and Stellar Astrophysics Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2507.15924 |