A population of neutron star candidates in wide orbits from Gaia astrometry
Article
El-Badry, Kareem, Rix, Hans-Walter, Latham, David W., Shahaf, Sahar, Mazeh, Tsevi, Bieryla, Allyson, Buchhave, Lars A., Andrae, René, Yamaguchi, Natsuko, Isaacson, Howard, Howard, Andrew W., Savino, Alessandro and Ilyin, Ilya V.. 2024. "A population of neutron star candidates in wide orbits from Gaia astrometry
." Open Journal of Astrophysics. 7. https://doi.org/10.33232/001c.121261
Article Title | A population of neutron star candidates in wide orbits from Gaia astrometry |
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Article Category | Article |
Authors | El-Badry, Kareem, Rix, Hans-Walter, Latham, David W., Shahaf, Sahar, Mazeh, Tsevi, Bieryla, Allyson, Buchhave, Lars A., Andrae, René, Yamaguchi, Natsuko, Isaacson, Howard, Howard, Andrew W., Savino, Alessandro and Ilyin, Ilya V. |
Journal Title | Open Journal of Astrophysics |
Journal Citation | 7 |
Number of Pages | 34 |
Year | 2024 |
Place of Publication | Ireland |
ISSN | 2565-6120 |
Digital Object Identifier (DOI) | https://doi.org/10.33232/001c.121261 |
Web Address (URL) | https://astro.theoj.org/article/121261-a-population-of-neutron-star-candidates-in-wide-orbits-from-gaia-astrometry |
Abstract | We report discovery and spectroscopic follow-up of 21 astrometric binaries containing solar-type stars and dark companions with masses near 1.4 M?. The simplest interpretation is that the companions are dormant neutron stars (NSs), though ultramassive white dwarfs (WDs) and tight WD+WD binaries cannot be fully excluded. We selected targets from Gaia DR3 astrometric binary solutions in which the luminous star is on the main sequence and the dynamically-implied mass of the unseen companion is (a) more than 1.25 M? and (b) too high to be any non-degenerate star or close binary. We obtained multi-epoch radial velocities (RVs) over a period of 700 days, spanning a majority of the orbits’ dynamic range in RV. The RVs broadly validate the astrometric solutions and significantly tighten constraints on companion masses. Several systems have companion masses that are unam-biguously above the Chandrasekhar limit, while the rest have masses between 1.25 and 1.4 M?. The orbits are significantly more eccentric at fixed period than those of typical WD + MS binaries, perhaps due to natal kicks. Metal-poor stars are overrepresented in the sample: three out of 21 objects (14%) have [Fe/H] ? ?1.5 and are on halo orbits, compared to ? 0.5% of the parent Gaia binary sample. The metal-poor stars are all strongly enhanced in lithium. The formation history of these objects is puzzling: it is unclear both how the binaries escaped a merger or dramatic orbital shrinkage when the NS progenitors were red supergiants, and how they remained bound when the NSs formed. Gaia has now discovered 3 black holes (BHs) in astrometric binaries with masses above 9 M?, and 21 NSs with masses near 1.4 M?. The lack of intermediate-mass objects in this sample is striking and significant, supporting the existence of a BH/NS mass bimodality over four orders of magnitude in orbital period. © 2024, National University of Ireland Maynooth. All rights reserved. |
Keywords | binaries: spectroscopic; stars: neutron; stars: evolut |
Contains Sensitive Content | Does not contain sensitive content |
ANZSRC Field of Research 2020 | 5101. Astronomical sciences |
Byline Affiliations | California Institute of Technology (Caltech), United States |
Max Planck Institute for Astronomy, Germany | |
Center for Astrophysics Harvard and Smithsonian, United States | |
Weizmann Institute of Science, Israel | |
Tel Aviv University, Israel | |
Technical University of Denmark, Denmark | |
University of California Berkeley, United States | |
Centre for Astrophysics | |
Leibniz Institute for Astrophysics Potsdam, Germany |
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