From Feast to Famine: A Systematic Study of Accretion onto Oblique Pulsars with 3D GRMHD Simulations
Disk-fed accretion onto neutron stars can power a wide range of astrophysical sources ranging from X-ray binaries, to accretion-powered millisecond pulsars, ultraluminous X-ray sources, and gamma-ray bursts. A crucial parameter controlling the gas–magnetosphere interaction is the strength of the ste...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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IOP Publishing
2024-01-01
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| Series: | The Astrophysical Journal Letters |
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| Online Access: | https://doi.org/10.3847/2041-8213/ad16eb |
| _version_ | 1797353218780430336 |
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| author | Ariadna Murguia-Berthier Kyle Parfrey Alexander Tchekhovskoy Jonatan Jacquemin-Ide |
| author_facet | Ariadna Murguia-Berthier Kyle Parfrey Alexander Tchekhovskoy Jonatan Jacquemin-Ide |
| author_sort | Ariadna Murguia-Berthier |
| collection | DOAJ |
| description | Disk-fed accretion onto neutron stars can power a wide range of astrophysical sources ranging from X-ray binaries, to accretion-powered millisecond pulsars, ultraluminous X-ray sources, and gamma-ray bursts. A crucial parameter controlling the gas–magnetosphere interaction is the strength of the stellar dipole. In addition, coherent X-ray pulsations in many neutron star systems indicate that the star's dipole moment is oblique relative to its rotation axis. Therefore, it is critical to systematically explore the 2D parameter space of the star's magnetic field strength and obliquity, which is what this work does, for the first time, in the framework of 3D general-relativistic magnetohydrodynamics. If the accretion disk carries its own vertical magnetic field, this introduces an additional factor: the relative polarity of the disk and stellar magnetic fields. We find that depending on the strength of the stellar dipole and the star–disk relative polarity, the neutron star's jet power can either increase or decrease with increasing obliquity. For weak dipole strength (equivalently, high accretion rate), the parallel polarity results in a positive correlation between jet power and obliquity, whereas the antiparallel orientation displays the opposite trend. For stronger dipoles, the relative-polarity effect disappears, and jet power always decreases with increasing obliquity. The influence of the relative polarity gradually disappears as obliquity increases. Highly oblique pulsars tend to have an increased magnetospheric radius, a lower mass accretion rate, and enter the propeller regime at lower magnetic moments than aligned stars. |
| first_indexed | 2024-03-08T13:27:58Z |
| format | Article |
| id | doaj.art-de7baade770c4a7cab71a7099e555f67 |
| institution | Directory Open Access Journal |
| issn | 2041-8205 |
| language | English |
| last_indexed | 2024-03-08T13:27:58Z |
| publishDate | 2024-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal Letters |
| spelling | doaj.art-de7baade770c4a7cab71a7099e555f672024-01-17T14:16:53ZengIOP PublishingThe Astrophysical Journal Letters2041-82052024-01-019611L2010.3847/2041-8213/ad16ebFrom Feast to Famine: A Systematic Study of Accretion onto Oblique Pulsars with 3D GRMHD SimulationsAriadna Murguia-Berthier0https://orcid.org/0000-0003-2333-6116Kyle Parfrey1https://orcid.org/0000-0001-6173-0099Alexander Tchekhovskoy2https://orcid.org/0000-0002-9182-2047Jonatan Jacquemin-Ide3https://orcid.org/0000-0003-2982-0005Center for Interdisciplinary Exploration & Research in Astrophysics (CIERA), Physics & Astronomy, Northwestern University , Evanston, IL 60202, USAPrinceton Plasma Physics Laboratory , Princeton, NJ 08540, USACenter for Interdisciplinary Exploration & Research in Astrophysics (CIERA), Physics & Astronomy, Northwestern University , Evanston, IL 60202, USACenter for Interdisciplinary Exploration & Research in Astrophysics (CIERA), Physics & Astronomy, Northwestern University , Evanston, IL 60202, USADisk-fed accretion onto neutron stars can power a wide range of astrophysical sources ranging from X-ray binaries, to accretion-powered millisecond pulsars, ultraluminous X-ray sources, and gamma-ray bursts. A crucial parameter controlling the gas–magnetosphere interaction is the strength of the stellar dipole. In addition, coherent X-ray pulsations in many neutron star systems indicate that the star's dipole moment is oblique relative to its rotation axis. Therefore, it is critical to systematically explore the 2D parameter space of the star's magnetic field strength and obliquity, which is what this work does, for the first time, in the framework of 3D general-relativistic magnetohydrodynamics. If the accretion disk carries its own vertical magnetic field, this introduces an additional factor: the relative polarity of the disk and stellar magnetic fields. We find that depending on the strength of the stellar dipole and the star–disk relative polarity, the neutron star's jet power can either increase or decrease with increasing obliquity. For weak dipole strength (equivalently, high accretion rate), the parallel polarity results in a positive correlation between jet power and obliquity, whereas the antiparallel orientation displays the opposite trend. For stronger dipoles, the relative-polarity effect disappears, and jet power always decreases with increasing obliquity. The influence of the relative polarity gradually disappears as obliquity increases. Highly oblique pulsars tend to have an increased magnetospheric radius, a lower mass accretion rate, and enter the propeller regime at lower magnetic moments than aligned stars.https://doi.org/10.3847/2041-8213/ad16ebNeutron starsPulsarsGeneral relativityMagnetohydrodynamical simulations |
| spellingShingle | Ariadna Murguia-Berthier Kyle Parfrey Alexander Tchekhovskoy Jonatan Jacquemin-Ide From Feast to Famine: A Systematic Study of Accretion onto Oblique Pulsars with 3D GRMHD Simulations The Astrophysical Journal Letters Neutron stars Pulsars General relativity Magnetohydrodynamical simulations |
| title | From Feast to Famine: A Systematic Study of Accretion onto Oblique Pulsars with 3D GRMHD Simulations |
| title_full | From Feast to Famine: A Systematic Study of Accretion onto Oblique Pulsars with 3D GRMHD Simulations |
| title_fullStr | From Feast to Famine: A Systematic Study of Accretion onto Oblique Pulsars with 3D GRMHD Simulations |
| title_full_unstemmed | From Feast to Famine: A Systematic Study of Accretion onto Oblique Pulsars with 3D GRMHD Simulations |
| title_short | From Feast to Famine: A Systematic Study of Accretion onto Oblique Pulsars with 3D GRMHD Simulations |
| title_sort | from feast to famine a systematic study of accretion onto oblique pulsars with 3d grmhd simulations |
| topic | Neutron stars Pulsars General relativity Magnetohydrodynamical simulations |
| url | https://doi.org/10.3847/2041-8213/ad16eb |
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