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| Format: | Preprint |
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2025
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| Online-Zugang: | https://arxiv.org/abs/2507.10682 |
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| _version_ | 1866912482620080128 |
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| author | Cary, Savannah Lu, Wenbin Leung, Calvin Wong, Tin Long Sunny |
| author_facet | Cary, Savannah Lu, Wenbin Leung, Calvin Wong, Tin Long Sunny |
| contents | Recent observations have unveiled a population of pulsars with spin periods of a few minutes to hours that lie beyond the traditional ``death line.'' If they originate from neutron stars (NSs), the existence of such ultra-long period pulsars (ULPs) challenges our current understanding of NS evolution and emission. In this work, we propose a new channel for disk formation based on NSs born in close binaries with main-sequence companion stars. Using a hydrodynamic simulation of supernova-companion interactions, we show that a newborn NS may gravitationally capture gas as it moves through the complex density field shaped by the explosion. For a binary separation of $20\rm~R_\odot$ and a companion mass of $4\rm~M_\odot$, we find the occurrence fraction for disk formation around unbound NSs to be $\sim10\%$. By modeling the disk evolution and its interaction with the NS, we find a bimodal distribution in spin periods: canonical pulsars with $P\lesssim10\rm\,s$ are the ones who lack disks or whose magnetospheres never interacted with the disk, and ULPs with $10^3\lesssim P<10^5\rm\,s$ are produced when the system undergoes a short-lived ``propeller'' phase during which the NS undergoes rapid spin-down. Such ULPs are formed under strong initial dipolar magnetic field strengths $B_0\gtrsim10^{14}\rm\,G$, with a formation rate of $10^{-4}\rm\,yr^{-1}$ in the Milky Way. We also find that a small population of pulsars with moderate magnetic field strengths ($10^{13}\lesssim~B_0\lesssim10^{14}\rm\,G$) and relatively slow initial periods ($P_0\gtrsim0.1\rm\,s$) evolve to $P\sim10^2\rm\,s$, filling the gap between the bimodal distribution. Thus, our model provides a unified explanation for pulsars beyond the ``death line.'' |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_10682 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Accretion from a Shock-Inflated Companion: Spinning Down Neutron Stars to Hour-Long Periods Cary, Savannah Lu, Wenbin Leung, Calvin Wong, Tin Long Sunny High Energy Astrophysical Phenomena Solar and Stellar Astrophysics Recent observations have unveiled a population of pulsars with spin periods of a few minutes to hours that lie beyond the traditional ``death line.'' If they originate from neutron stars (NSs), the existence of such ultra-long period pulsars (ULPs) challenges our current understanding of NS evolution and emission. In this work, we propose a new channel for disk formation based on NSs born in close binaries with main-sequence companion stars. Using a hydrodynamic simulation of supernova-companion interactions, we show that a newborn NS may gravitationally capture gas as it moves through the complex density field shaped by the explosion. For a binary separation of $20\rm~R_\odot$ and a companion mass of $4\rm~M_\odot$, we find the occurrence fraction for disk formation around unbound NSs to be $\sim10\%$. By modeling the disk evolution and its interaction with the NS, we find a bimodal distribution in spin periods: canonical pulsars with $P\lesssim10\rm\,s$ are the ones who lack disks or whose magnetospheres never interacted with the disk, and ULPs with $10^3\lesssim P<10^5\rm\,s$ are produced when the system undergoes a short-lived ``propeller'' phase during which the NS undergoes rapid spin-down. Such ULPs are formed under strong initial dipolar magnetic field strengths $B_0\gtrsim10^{14}\rm\,G$, with a formation rate of $10^{-4}\rm\,yr^{-1}$ in the Milky Way. We also find that a small population of pulsars with moderate magnetic field strengths ($10^{13}\lesssim~B_0\lesssim10^{14}\rm\,G$) and relatively slow initial periods ($P_0\gtrsim0.1\rm\,s$) evolve to $P\sim10^2\rm\,s$, filling the gap between the bimodal distribution. Thus, our model provides a unified explanation for pulsars beyond the ``death line.'' |
| title | Accretion from a Shock-Inflated Companion: Spinning Down Neutron Stars to Hour-Long Periods |
| topic | High Energy Astrophysical Phenomena Solar and Stellar Astrophysics |
| url | https://arxiv.org/abs/2507.10682 |