MHD SIMULATIONS OF ACCRETION ONTO A MAGNETIZED NEUTRON STAR IN THE "PROPELLER" REGIME

2008 ◽  
Vol 17 (10) ◽  
pp. 1723-1729 ◽  
Author(s):  
O. D. TOROPINA ◽  
M. M. ROMANOVA ◽  
R. V. E. LOVELACE
Keyword(s):  
Neutron Star ◽  
Interstellar Medium ◽  
Soft Gamma Repeaters ◽  
Mhd Simulations ◽  
Magnetohydrodynamic Simulations

We use axisymmetric magnetohydrodynamic simulations to investigate the spinning-down of magnetars rotating in the propeller regime and moving supersonically through the interstellar medium. The simulations indicate that magnetars spin down rapidly due to this interaction, and faster than for the case of a non-moving star. We discuss this model with respect to soft gamma repeaters (SGRs) and the isolated neutron star candidates.

scholarly journals 3D magnetized jet break-out from neutron-star binary merger ejecta: afterglow emission from the jet and the ejecta

2021 ◽  
Vol 502 (2) ◽  
pp. 1843-1855
Author(s):  
Antonios Nathanail ◽  
Ramandeep Gill ◽  
Oliver Porth ◽  
Christian M Fromm ◽  
Luciano Rezzolla
Keyword(s):  
Neutron Star ◽  
Thermal Emission ◽  
Opening Angle ◽  
Hollow Core ◽  
Binary Neutron Star ◽  
Vlbi Observations ◽  
Superluminal Motion ◽  
General Relativistic ◽  
Star Binary ◽  
Magnetohydrodynamic Simulations

ABSTRACT We perform 3D general-relativistic magnetohydrodynamic simulations to model the jet break-out from the ejecta expected to be produced in a binary neutron-star merger. The structure of the relativistic outflow from the 3D simulation confirms our previous results from 2D simulations, namely, that a relativistic magnetized outflow breaking out from the merger ejecta exhibits a hollow core of θcore ≈ 4°, an opening angle of θjet ≳ 10°, and is accompanied by a wind of ejected matter that will contribute to the kilonova emission. We also compute the non-thermal afterglow emission of the relativistic outflow and fit it to the panchromatic afterglow from GRB170817A, together with the superluminal motion reported from VLBI observations. In this way, we deduce an observer angle of $\theta _{\rm obs}= 35.7^{\circ \, \, +1.8}_{\phantom{\circ \, \, }-2.2}$. We further compute the afterglow emission from the ejected matter and constrain the parameter space for a scenario in which the matter responsible for the thermal kilonova emission will also lead to a non-thermal emission yet to be observed.

scholarly journals Constraining the coherence scale of the interstellar magnetic field using TeV gamma-ray observations of supernova remnants

2020 ◽  
Vol 496 (2) ◽  
pp. 2448-2461 ◽  
Author(s):  
Matteo Pais ◽  
Christoph Pfrommer ◽  
Kristian Ehlert ◽  
Maria Werhahn ◽  
Georg Winner
Keyword(s):  
Magnetic Field ◽  
Interstellar Medium ◽  
Supernova Remnants ◽  
Gamma Ray ◽  
Galactic Cosmic Rays ◽  
Shock Acceleration ◽  
Interstellar Gas ◽  
Narrow Angle ◽  
Magnetohydrodynamic Simulations ◽  
Tev Gamma Rays

ABSTRACT Galactic cosmic rays (CRs) are believed to be accelerated at supernova remnant (SNR) shocks. In the hadronic scenario, the TeV gamma-ray emission from SNRs originates from decaying pions that are produced in collisions of the interstellar gas and CRs. Using CR-magnetohydrodynamic simulations, we show that magnetic obliquity-dependent shock acceleration is able to reproduce the observed TeV gamma-ray morphology of SNRs such as Vela Jr and SN1006 solely by varying the magnetic morphology. This implies that gamma-ray bright regions result from quasi-parallel shocks (i.e. when the shock propagates at a narrow angle to the upstream magnetic field), which are known to efficiently accelerate CR protons, and that gamma-ray dark regions point to quasi-perpendicular shock configurations. Comparison of the simulated gamma-ray morphology to observations allows us to constrain the magnetic coherence scale λB around Vela Jr and SN1006 to $\lambda _B \simeq 13_{-4.3}^{+13}$ pc and $\lambda _B \gt 200_{-40}^{+50}$ pc, respectively, where the ambient magnetic field of SN1006 is consistent with being largely homogeneous. We find consistent pure hadronic and mixed hadronic-leptonic models that both reproduce the multifrequency spectra from the radio to TeV gamma-rays and match the observed gamma-ray morphology. Finally, to capture the propagation of an SNR shock in a clumpy interstellar medium, we study the interaction of a shock with a dense cloud with numerical simulations and analytics. We construct an analytical gamma-ray model for a core collapse SNR propagating through a structured interstellar medium, and show that the gamma-ray luminosity is only biased by 30 per cent for realistic parameters.

scholarly journals Supernovae and the Interstellar Medium

1970 ◽  
Vol 39 ◽  
pp. 229-235
Author(s):  
L. Woltjer
Keyword(s):  
Neutron Star ◽  
Interstellar Medium ◽  
Visible Light ◽  
Supernova Remnants ◽  
Optical Radiation ◽  
Crab Nebula ◽  
Bolometric Correction

The nature of the supernova event is still poorly understood. A variety of models has been proposed and the interpretation of the observations remains ambiguous. About all that is certain is that in the supernova event much of the matter is ejected at speeds of typically 10 000 km sec−1 and that about 1049 erg of visible light is emitted. The amount of matter ejected and the bolometric correction to be applied to the optical radiation are very uncertain. The discovery of a pulsar in two supernova remnants (Crab Nebula and Vela X) suggests that frequently a neutron star or other condensed object results following the outburst.

scholarly journals Three-Dimensional MHD Simulations of a Subcluster Plasma Moving in Turbulent ICM

2006 ◽  
Vol 2 (S235) ◽  
pp. 189-189
Author(s):  
N. Asai ◽  
N. Fukuda ◽  
R. Matsumoto
Keyword(s):  
Heat Conduction ◽  
Magnetic Fields ◽  
Three Dimensional ◽  
Cold Fronts ◽  
Mhd Simulations ◽  
Anisotropic Heat Conduction ◽  
Magnetohydrodynamic Simulations

AbstractWe carried out 3D magnetohydrodynamic simulations of a subcluster moving in turbulent ICM by including anisotropic heat conduction. Since magnetic fields stretched along the subcluster surface suppress the heat conduction across the front, cold fronts are formed and sustained.

scholarly journals EARLY PHASES OF DIFFERENT TYPES OF ISOLATED NEUTRON STAR

2005 ◽  
Vol 14 (06) ◽  
pp. 1075-1082 ◽  
Author(s):  
AŞKIN ANKAY ◽  
SERKAN ŞAHIN ◽  
GÖKÇE KARANFIL ◽  
EFE YAZGAN
Keyword(s):  
Neutron Star ◽  
Thermal Neutron ◽  
Early Phase ◽  
Radio Pulsar ◽  
Radio Pulsars ◽  
X Ray ◽  
Soft Gamma Repeaters ◽  
Different Types ◽  
Early Phases

Two Galactic isolated strong X-ray pulsars seem to be in the densest environments compared to other types of Galactic pulsar. X-ray pulsar J1846-0258 can be in an early phase of anomalous X-ray pulsars and soft gamma repeaters if its average braking index is ~1.8–2.0. X-ray pulsar J1811-1925 must have a very large average braking index (~11) if this pulsar was formed by SN 386AD. This X-ray pulsar can be in an early phase of the evolution of the radio pulsars located in the region P ~ 50–150 ms and Ṗ ~ 10-14–10-16 ss -1 of the P–Ṗ diagram. X-ray/radio pulsar J0540-69 seems to be evolving in the direction to the dim isolated thermal neutron star region on the P–Ṗ diagram. Possible progenitors of different types of neutron star are also discussed.

scholarly journals Global 3D radiation magnetohydrodynamic simulations for FU Ori’s accretion disc and observational signatures of magnetic fields

2020 ◽  
Vol 495 (3) ◽  
pp. 3494-3514 ◽  
Author(s):  
Zhaohuan Zhu ◽  
Yan-Fei Jiang ◽  
James M Stone
Keyword(s):  
Magnetic Fields ◽  
Accretion Rate ◽  
Mass Loss Rate ◽  
Global Radiation ◽  
Surface Region ◽  
Accretion Disc ◽  
Near Ir ◽  
Mhd Simulations ◽  
Fu Ori ◽  
Magnetohydrodynamic Simulations

ABSTRACT FU Ori is the prototype of FU Orionis systems that are outbursting protoplanetary discs. Magnetic fields in FU Ori’s accretion discs have previously been detected using spectropolarimetry observations for Zeeman effects. We carry out global radiation ideal MHD simulations to study FU Ori’s inner accretion disc. We find that (1) when the disc is threaded by vertical magnetic fields, most accretion occurs in the magnetically dominated atmosphere at z ∼ R, similar to the ‘surface accretion’ mechanism in previous locally isothermal MHD simulations. (2) A moderate disc wind is launched in the vertical field simulations with a terminal speed of ∼300–500 km s−1 and a mass-loss rate of 1–10 per cent the disc accretion rate, which is consistent with observations. Disc wind fails to be launched in simulations with net toroidal magnetic fields. (3) The disc photosphere at the unit optical depth can be either in the wind launching region or the accreting surface region. Magnetic fields have drastically different directions and magnitudes between these two regions. Our fiducial model agrees with previous optical Zeeman observations regarding both the field directions and magnitudes. On the other hand, simulations indicate that future Zeeman observations at near-IR wavelengths or towards other FU Orionis systems may reveal very different magnetic field structures. (4) Due to energy loss by the disc wind, the disc photosphere temperature is lower than that predicted by the thin disc theory, and the previously inferred disc accretion rate may be lower than the real accretion rate by a factor of ∼2–3.

scholarly journals The O stars: optical review

1979 ◽  
Vol 83 ◽  
pp. 1-22
Author(s):  
J. B. Hutchings
Keyword(s):  
Neutron Star ◽  
Interstellar Medium ◽  
Mass Loss ◽  
Large Fraction ◽  
Significant Fraction ◽  
High Mass ◽  
X Ray ◽  
The Galaxy ◽  
High Mass Loss ◽  
Rough Outline

I would like to start with a quick overview of the O stars - their significance and role in the galaxy and in astrophysics - just to remind ourselves of why we are here and what we hope to talk about. In Table 1 I show a rough outline of the contribution of O stars to what happens in the galaxy as a whole. Because of their extreme luminosity, they contribute a large fraction of the radiation of the galaxy, while forming a very tiny group of objects and mass. Because of their short lifetime they are a population that has gone through 104 generations in the life of the galaxy. Their high mass loss rates may account for a large fraction of the new matter injected into the interstellar medium, and they probably power some significant fraction of the hard X-ray sources in the galaxy, by virtue of the fact that a companion can become a neutron star a) without disrupting the binary and b) while the companion is still a mass losing O star.

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