A magnetic switch that determines the speed of astrophysical jets

Meier, David L.; Edgington, S.; Godon, Patrick; Payne, D. G.; Lind, K. R.

doi:10.1038/41034

Cited by 97 publications

(79 citation statements)

References 16 publications

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“…These processes tend to produce relatively cold jets, in the sense that the thermal energy of the jet is not initially large compared to either the rest mass or the jet kinetic energy. There may be a critical magnetic Ðeld above which these mechanisms are able to provide matter directly with high Lorentz factor (Meier et al 1997). Other processes like neutrino energy deposition (Woosley 1993 ;MW99 ;Janka et al 1999aJanka et al , 1999b or magnetic reconnection (Thompson 1994 ;Katz 1997) in the disk deposit their energy chieÑy as heat and make hot jets.…”

Section: Jet Initiationmentioning

confidence: 99%

Supernovae, Jets, and Collapsars

MacFadyen

Woosley

Heger

2001

ApJ

746

822

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We continue our study of the possible production of supernovae and a variety of high-energy transients by black hole formation in massive stars endowed with rotation : the "" collapsar model.ÏÏ The black hole may form either promptly, since a successful outgoing shock fails to be launched by the collapsed iron core (collapsar Type I), or, in a mild explosion, by fallback (collapsar Type II). In the latter case, the inner layers of the star initially move outward but lack adequate momentum to eject all the matter exterior to the young neutron star. Over a period of minutes to hours, D0.1È5 falls back onto the M _ collapsed remnant, turning it into a black hole and establishing an accretion disk. The accretion rate, D0.001È0.01 s~1, is inadequate to produce a jet mediated by neutrino annihilation but is similar to M _ what has been invoked in magnetohydrodynamic (MHD) models for gamma-ray bursts (GRBs). This fallback is modeled in detail for two 25 progenitors using two di †erent one-dimensional hydrody-M _ namics codes, one Lagrangian and one Eulerian. The production and consequences of jets are then explored in both sorts of collapsars. JustiÐcation is given for assuming that the jet power is a constant times the mass accretion rate, and the consequences of v \ 0.001 and 0.01 are explored. Adopting vM 0 c2, an initial collimation half-angle of 10¡, the opening of the jet as it propagates through the exploding star is strongly inÑuenced not only by the jetÏs kinetic energy but also by its initial pressure and the stellar structure. Cold jets tend to stay collimated and become even more so, sometimes having an angle of only a few degrees when they reach the surface. Jets having higher internal pressure than the stellar material through which they pass, or less initial collimation, spread out and tend to make energetic, asymmetric supernovae accompanied, in helium stars, by weak GRBs. SN 1998bw may have been such an event, and other events having energies between that of ordinary GRBs and GRB 980425 await discovery. In supergiant stars, shock breakout also produces bright X-ray transients that might be a diagnostic of the model, but even the most powerful jets (equivalent isotropic energy 1054 ergs) will not produce a GRB in a red supergiant. For such Type II supernovae the limiting Lorentz factor is ! B 2. Type II collapsars should be more frequent than Type I and may power the most common form of gamma-ray transient in the universe. However, the GRBs seen by BATSE are, for the most part, too brief to be Type II collapsars. Those are still attributed to prompt black hole formation. Even there though, the diverse energies and time structure reÑect chieÑy the viewing angle and the variable collimation of the jet inside the star, not a highly variable "" central engine.ÏÏ Indeed, collapsar-induced transients may all have a common total energy in the range 1051È1052 ergs.

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Section: Jet Initiationmentioning

confidence: 99%

Supernovae, Jets, and Collapsars

MacFadyen

Woosley

Heger

2001

ApJ

746

822

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“…Several authors claim that it is connected with transition of the intrinsically supersonic jet to transonic/subsonic flow that is being decelerated due to entrainment of thermal plasma in the innermost region of the host galaxy (e.g: Komissarov 1994; Bowman et al 1996;Bicknell 1995;Kaiser & Alexander 1997). A second hypothesis links aberration in morphology with a more profound issue of the central engine (Meier et al 1997;Zirbel & Baum 1995) or the jet itself (Reynolds et al 1996;Ghisellini & Celotti 2001). Last but not least, the scheme attributes FR I/FR II dichotomy to the intergalactic medium, which together with jet power shapes the object morphology (Gopal-Krishna 1991;Gopal-Krishna et al 1996).…”

Section: Introductionmentioning

confidence: 99%

Orientation of the cores of hybrid morphology radio sources

Ceglowski

Gawroński

Kunert-Bajraszewska

2013

A&A

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Aims. The FR I/FR II dichotomy is a much debated issue in the astrophysics of extragalactic radio sources. Study of the properties of HYbrid MOrphology Radio Sources (HYMORS) may bring crucial information and lead to a step forward in understanding the origin of FR I/FR II dichotomy. HYMORS are a rare class of double-lobed radio sources where each of the two lobes clearly exhibits a different FR morphology. This article describes follow-up high resolution VLBA observations of the five discovered by us HYMORS. The main aim of the observations was to answer the questions of whether the unusual radio morphology is connected to the orientation of objects towards the observer. Methods. The milliarcsecond-scale structures are good probes of the galactic medium, the possible asymmetries, and orientation of the central engines of the sources. We obtained the high resolution radio maps of five hybrid radio morphology objects with the VLBA at C-band and L-band. Results. The cores of all five sources have been detected at both radio bands. Two of them revealed milliarcsecond core-jet structures, the next two objects showed hints of parsec-scale jets, and the last one remained point-like at both frequencies. Conclusions. We compared properties of observed milliarcsecond structures of hybrid sources with the larger scale ones previously detected with the VLA. We find that on both scales the fluxes of their central components are similar, which may indicate the lack of additional emission in the proximity of the nucleus. This suggests that jets present on the ∼1−10 kpc scale in those objects are FR II-like. When possible, the detected core-jet structures were used for estimating the core's spatial orientation. The result is that neither the FR I-like nor the FR II-like side is preferred, which may suggest that no specific spatial orientation of HYMORS is required to explain their radio morphology. Their estimated viewing angles indicate they are unbeamed objects. The 178/151 MHz luminosity of observed HYMORS exceed the traditional FR I/FR II break luminosity, indicating they have radio powers similar to FR IIs.

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“…Major progress has been made recently in the hydromagnetic regime of jet formation, originally proposed by Blandford & Payne (1982). Dynamic MHD simulations of the near-jet region have been carried out by several groups (Bell 1994 ;Ustyugova et al 1995Ustyugova et al , 1999Koldoba et al 1995 ;Romanova et al 1997Romanova et al , 1998Meier et al 1997 ;Ouyed & Pudritz 1997 ;Krasnopolsky, Li, & Blandford 1999). The simulation study of Ustyugova et al (1999) in the hydromagnetic wind regime indicates that the outÑows are accel-erated to superfast magnetosonic, superescape speeds close to their region of origin (D80 times the inner radius of the disk), whereas the collimation occurs at much larger distances.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Helix Formation Driven by Keplerian Disk Rotation in an External Plasma Pressure: The Initial Expansion Stage

Lovelace

Finn

et al. 2001

ApJ

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We study the evolution of a magnetic arcade that is anchored to an accretion disk and is sheared by the di †erential rotation of a Keplerian disk. By including an extremely low external plasma pressure at large distances, we obtain a sequence of axisymmetric magnetostatic equilibria and show that there is a fundamental di †erence between Ðeld lines that are a †ected by the plasma pressure and those that are not (i.e., force free). Force-free Ðelds, while being twisted by the di †erential rotation of the disk, expand outward at an angle of D60¡ away from the rotation axis, consistent with the previous studies. These force-free Ðeld lines, however, are enclosed by the outer Ðeld lines, which originate from small disk radii and come back to the disk at large radii. These outer Ðelds experience most of the twist, and they are also a †ected most by the external plasma pressure. At large cylindrical radial distances, magnetic pressure and plasma pressure are comparable so that any further radial expansion of magnetic Ðelds is prevented or slowed down greatly by this pressure. This hindrance to cylindrical radial expansion causes most of the added twist to be distributed on the ascending portion of the Ðeld lines, close to the rotation axis. Since these Ðeld lines are twisted most, the increasing ratio of the toroidal component to the B Õ poloidal component eventually results in the collimation of magnetic energy and Ñux around the B R,z rotation axis. We discuss the difficulty with adding a large number of twists within the limitations of the magnetostatic approximation.

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A magnetic switch that determines the speed of astrophysical jets

Cited by 97 publications

References 16 publications

Supernovae, Jets, and Collapsars

Supernovae, Jets, and Collapsars

Orientation of the cores of hybrid morphology radio sources

Magnetic Helix Formation Driven by Keplerian Disk Rotation in an External Plasma Pressure: The Initial Expansion Stage

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