GRMHD simulations of accreting neutron stars I: Non-rotating dipoles

Sercan Çlklntoǧlu*, K. Yavuz Ekşi, Luciano Rezzolla

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7 Atıf (Scopus)

Özet

We study the general-relativistic dynamics of matter being accreted on to and ejected by a magnetized and non-rotating neutron star. The dynamics is followed in the framework of fully general relativistic magnetohydrodynamics (GRMHD) within the ideal-MHD limit and in two spatial dimensions. More specifically, making use of the numerical code BHAC, we follow the evolution of a geometrically thick matter torus driven into accretion by the development of a magnetorotational instability. By making use of a number of simulations in which we vary the strength of the stellar dipolar magnetic field, we can determine self-consistently the location of the magnetospheric (or Alfvén) radius rmsph and study how it depends on the magnetic moment μ and on the accretion rate. Overall, we recover the analytic Newtonian scaling relation, i.e. rmsph ∝ B4/7, but also find that the dependence on the accretion rate is very weak. Furthermore, we find that the material torque correlates linearly with the mass-accretion rate, although both of them exhibit rapid fluctuations. Interestingly, the total torque fluctuates drastically in strong magnetic field simulations and these unsteady torques observed in the simulations could be associated with the spin fluctuations observed in X-ray pulsars.

Orijinal dilİngilizce
Sayfa (başlangıç-bitiş)3212-3226
Sayfa sayısı15
DergiMonthly Notices of the Royal Astronomical Society
Hacim517
Basın numarası3
DOI'lar
Yayın durumuYayınlandı - 1 Ara 2022
Harici olarak yayınlandıEvet

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Publisher Copyright:
© 2022 The Author(s).

Finansman

LR gratefully acknowledge funding by the State of Hesse within the Research Cluster ELEMENTS (Project ID 500/10.006) by the ERC Advanced Grant 'JETSET: Launching, propagation, and emission of relativistic jets from binary mergers and across mass scales' (Grant No. 884631). The numerical calculations reported in this paper were performed on Iboga Cluster in Frankfurt and at T¨UBİTAK ULAK- BIM, High Performance, and Grid Computing Center (TRUBA resources) in Ankara. KYE acknowledges support from the Scientific and Technological Research Council of Turkey (T¨UBİTAK) with project number 112T105. S C acknowledges support from T¨UBİTAK with grant number 1059B141801188.

FinansörlerFinansör numarası
Horizon 2020 Framework Programme884631
European Research Council
Türkiye Bilimsel ve Teknolojik Araştırma Kurumu112T105, 1059B141801188

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