Evolution of proto-neutron stars to pulsars, magnetars and central compact objects
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arXiv
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| Autores principales: | , |
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| Formato: | Preprint |
| Publicado: |
2021
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| _version_ | 1866908808405581824 |
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| author | Bakır, İrem Ekşi, Kazım Yavuz |
| author_facet | Bakır, İrem Ekşi, Kazım Yavuz |
| contents | Some young neutron stars, the magnetars, have ultra-strong magnetic fields, yet their inferred birth rate is comparable to the core-collapse supernova rate, challenging scenarios that require rare, extreme conditions. We propose that this discrepancy can be reconciled if both pulsars and magnetars pass through a dynamo process during the proto-neutron star (PNS) phase. We employ a shear-driven $α$--$Ω$ dynamo model that includes PNS contraction. The dynamo generically produces toroidal-dominated fields set mainly by the $Ω$-effect. The evolution of the poloidal field is first dominated by flux conservation during collapse and then by the $α$-effect. The saturated toroidal field depends strongly on the initial value of the shear, with a threshold at $q_0 \simeq 0.23$; below this, the poloidal field remains near the value obtained by the flux-conservation ($\approx 2.5\times10^{10}\,{\rm G}$). For the shortest initial periods, the model leads to magnetar-like strengths ($B_{\rm p} \simeq 10^{15}\,{\rm G}$, $B_ϕ\simeq 10^{16}\,{\rm G}$), while for the slower rotators it yields ordinary pulsar fields ($B_{\rm p} \simeq 10^{12}\,{\rm G}$, $B_ϕ\simeq 10^{14}\,{\rm G}$). We also argue that the central compact objects can acquire toroidal fields amplified solely by the $Ω$-effect; lacking the $α$-effect, their poloidal fields are not shaped by the dynamo effect. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2108_01051 |
| institution | arXiv |
| publishDate | 2021 |
| record_format | arxiv |
| spellingShingle | Evolution of proto-neutron stars to pulsars, magnetars and central compact objects Bakır, İrem Ekşi, Kazım Yavuz High Energy Astrophysical Phenomena Some young neutron stars, the magnetars, have ultra-strong magnetic fields, yet their inferred birth rate is comparable to the core-collapse supernova rate, challenging scenarios that require rare, extreme conditions. We propose that this discrepancy can be reconciled if both pulsars and magnetars pass through a dynamo process during the proto-neutron star (PNS) phase. We employ a shear-driven $α$--$Ω$ dynamo model that includes PNS contraction. The dynamo generically produces toroidal-dominated fields set mainly by the $Ω$-effect. The evolution of the poloidal field is first dominated by flux conservation during collapse and then by the $α$-effect. The saturated toroidal field depends strongly on the initial value of the shear, with a threshold at $q_0 \simeq 0.23$; below this, the poloidal field remains near the value obtained by the flux-conservation ($\approx 2.5\times10^{10}\,{\rm G}$). For the shortest initial periods, the model leads to magnetar-like strengths ($B_{\rm p} \simeq 10^{15}\,{\rm G}$, $B_ϕ\simeq 10^{16}\,{\rm G}$), while for the slower rotators it yields ordinary pulsar fields ($B_{\rm p} \simeq 10^{12}\,{\rm G}$, $B_ϕ\simeq 10^{14}\,{\rm G}$). We also argue that the central compact objects can acquire toroidal fields amplified solely by the $Ω$-effect; lacking the $α$-effect, their poloidal fields are not shaped by the dynamo effect. |
| title | Evolution of proto-neutron stars to pulsars, magnetars and central compact objects |
| topic | High Energy Astrophysical Phenomena |
| url | https://arxiv.org/abs/2108.01051 |