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| Auteurs principaux: | , , , |
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| Format: | Preprint |
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2025
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| Accès en ligne: | https://arxiv.org/abs/2507.13893 |
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| _version_ | 1866910069542617088 |
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| author | Lorange, Alexandra Pétri, Jérôme Sautron, Mattéo Vigon, Vincent |
| author_facet | Lorange, Alexandra Pétri, Jérôme Sautron, Mattéo Vigon, Vincent |
| contents | Millisecond pulsars (MSPs) are spun up during their accretion phase in a binary system. The exchange of angular momentum between the accretion disk and the star tends to align the spin and orbital angular momenta on a very short time scale compared to the accretion stage. In this work, we study a subset of $γ$-ray MSPs in binaries for which the orbital inclination angle $i$ has been accurately constrained thanks to the Shapiro delay measurements. Our goal is to constrain the observer viewing angle $ζ$ and to check whether it agrees with the orbital inclination angle $i$, in other words if $ζ\approx i$. We use a Bayesian inference technique to fit the MSP $γ$-ray light curves based on the third $γ$-ray pulsar catalogue (3PC). The emission model relies on the striped wind model deduced from force-free neutron star magnetosphere simulations. We found good agreement between the two angles $i$ and $ζ$ for a significant fraction of our sample, about four fifth, confirming the spin-orbit alignment scenario during the accretion stage. However about one fifth of our sample deviates significantly from this alignment. The reasons are manifold: either the $γ$-ray fit is not reliable or some precession and external torque avoid an almost perfect alignment. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_13893 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | The spin-orbit alignment hypothesis in millisecond pulsars Lorange, Alexandra Pétri, Jérôme Sautron, Mattéo Vigon, Vincent High Energy Astrophysical Phenomena Millisecond pulsars (MSPs) are spun up during their accretion phase in a binary system. The exchange of angular momentum between the accretion disk and the star tends to align the spin and orbital angular momenta on a very short time scale compared to the accretion stage. In this work, we study a subset of $γ$-ray MSPs in binaries for which the orbital inclination angle $i$ has been accurately constrained thanks to the Shapiro delay measurements. Our goal is to constrain the observer viewing angle $ζ$ and to check whether it agrees with the orbital inclination angle $i$, in other words if $ζ\approx i$. We use a Bayesian inference technique to fit the MSP $γ$-ray light curves based on the third $γ$-ray pulsar catalogue (3PC). The emission model relies on the striped wind model deduced from force-free neutron star magnetosphere simulations. We found good agreement between the two angles $i$ and $ζ$ for a significant fraction of our sample, about four fifth, confirming the spin-orbit alignment scenario during the accretion stage. However about one fifth of our sample deviates significantly from this alignment. The reasons are manifold: either the $γ$-ray fit is not reliable or some precession and external torque avoid an almost perfect alignment. |
| title | The spin-orbit alignment hypothesis in millisecond pulsars |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2507.13893 |