A Magnetic Explanation for the Rapid Burster

Kuijpers, J.; Kuperus, M.

doi:10.1007/978-94-011-1014-3_50

Cited by 3 publications

(6 citation statements)

References 2 publications

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“…To understand the dynamics of this ring of plasma, we Ðrst address the e †ect of the two main magnetic stresses (the radial and azimuthal stresses) on the inner edge of the disk. The discussion below closely follows those of Aly (1980), Aly & Kuijpers (1990), and Kuijpers & Kuperus (1994).…”

Section: Estimating Vmentioning

confidence: 54%

Jets from Accreting Magnetic Young Stellar Objects. II. Mechanism Physics

Goodson

Winglee

1999

ApJ

105

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This paper addresses the physical principles underpinning a new jet-launching mechanism described in a companion paper. In this new jet formation model, magnetic loops that connect the star to the disk become twisted and expand via helicity injection. This expansion drives an outÑow, with the axial symmetry of the disk leading to a concentration of outÑowing plasma along the rotation axis, forming the jet. In the companion paper, it is found that the radial location of the inner edge of the disk undergoes oscillations. In this paper, the physical causes of the disk oscillations are investigated. This investigation leads to the conclusion that there are three classes of Ñows that can arise, depending on the role of di †usive instabilities. The most di †usive Ñows allow the stellar magnetic Ðeld to slip through the accretion disk and yield steady accretion Ñows. Such conÐgurations are unlikely to produce outÑows. The Ñows with intermediate di †usivity have been described by Lovelace, Romanova, & Bisnovatyi-Kogan and represent conditions in which the Ðeld is e †ectively frozen into the accretion disk azimuthally but slips radially. In the absence of magnetic reconnection, such conÐgurations are predicted to produce steady Ñows with logarithmically collimated disk winds. The least di †usive Ñows, in which the bulk radial disk velocities are greater at times than the speeds with which magnetic Ðeld lines can di †use into the disks, lead to the formation of the collimated unsteady jets described in the companion paper and are the primary interest of this paper. The jet velocity is also addressed.

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Section: Estimating Vmentioning

confidence: 54%

Jets from Accreting Magnetic Young Stellar Objects. II. Mechanism Physics

Goodson

Winglee

1999

ApJ

105

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“…This also seems inconsistent at least with the short bursts, which show low persistent emission between bursts, although it could perhaps explain the inter-burst humps seen between mode 0 bursts. In order to match the observed bursting timescales, the original Kuijpers & Kuperus (1994) paper also posited a strong 10 12 G field for the RB, which is inconsistent with the observation of type I X-ray bursts at relatively high luminosities.…”

Section: Other Magnetospheric Instabilitiesmentioning

confidence: 90%

“…Since the discovery of type II bursts in the Rapid Burster, an assortment of instability mechanisms have been proposed for their origin. Bursts have been variously attributed to an instability in the accretion flow (either in viscosity or temperature), instabilities around the innermost stable circular orbit or as a result of the interaction between the accretion disc and a stellar magnetic field (e.g., Kuijpers & Kuperus 1994;Spruit & Taam 1993). In their review article, Lewin et al (1993) give an overview of the various strengths and weaknesses of the different models.…”

Section: Models For Type II Burstsmentioning

confidence: 99%

“…A weakness of many models proposed to explain type II bursts is the apparent uniqueness of the RB, since most proposed instabilities should be widely applicable. In this respect models based on magnetospheric instabilities are perhaps the most promising, since a strong magnetosphere introduces new characteristic lengthscales to the system, and the distinctiveness of the RB behaviour could then be attributed to an unusual magnetic field geometry (such as alignment with the rotation axis, e.g., Kuijpers & Kuperus 1994), or unusual relationship between the physical properties that determine the magnetic regulation of accretion and the properties of the accretion flow itself (in particular the accretion rate at which the state transition occurs). On the other hand, since X-ray pulsations have never been detected in the RB, it is not clear that there is a strong magnetic field in the system (although by the argument above this could be due to a near alignment between the rotation and the magnetic axes).…”

Section: Theory Of Disc-magnetosphere Interactionsmentioning

confidence: 99%

“…This can lead to either compression of the magnetic field by the disc moving inwards or unstable fingers of accretion onto the neutron star surface via interchange instabilities. Kuijpers & Kuperus (1994) proposed that the perfectly conducting disc can be completely shielded from the magnetic field of the star, so that the disc will spiral inwards and pinch the dipolar magnetic field along the equator into a distorted 'butterfly' shape. This compression lasts until the matter touches the surface of the star, whereupon the gas penetrates through the field and accretes on to the star.…”

Section: Other Magnetospheric Instabilitiesmentioning

confidence: 99%

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A population study of type II bursts in the Rapid Burster

Bagnoli

Zand

D’Angelo

2015

Monthly Notices of the Royal Astronomical Society

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Type II bursts are thought to arise from instabilities in the accretion flow onto a neutron star in an X-ray binary. Despite having been known for almost 40 years, no model can yet satisfactorily account for all their properties. To shed light on the nature of this phenomenon and provide a reference for future theoretical work, we study the entire sample of Rossi X-ray Timing Explorer data of type II bursts from the Rapid Burster (MXB 1730-335). We find that type II bursts are Eddington-limited in flux, that a larger amount of energy goes in the bursts than in the persistent emission, that type II bursts can be as short as 0.130 s, and that the distribution of recurrence times drops abruptly below 15-18 s. We highlight the complicated feedback between type II bursts and the NS surface thermonuclear explosions known as type I bursts, and between type II bursts and the persistent emission. We review a number of models for type II bursts. While no model can reproduce all the observed burst properties and explain the source uniqueness, models involving a gating role for the magnetic field come closest to matching the properties of our sample. The uniqueness of the source may be explained by a special combination of magnetic field strength, stellar spin period and alignment between the magnetic field and the spin axis.

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Magnetically gated accretion in an accreting ‘non-magnetic’ white dwarf

Scaringi

Maccarone

D’Angelo

et al. 2017

Nature

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White dwarfs are often found in binary systems with orbital periods ranging from tens of minutes to hours in which they can accrete gas from their companion stars. In about 15% of these binaries, the magnetic field of the white dwarf is strong enough (≥ 10 6 Gauss) to channel the accreted matter along field lines onto the magnetic poles 1,2 . The remaining systems are referred to as "non-magnetic", since to date there has been no evidence that they have a dynamically significant magnetic field. Here we report an analysis of archival optical observations of the "non-magnetic" accreting white dwarf in the binary system MV Lyrae (hereafter MV Lyr), whose lightcurve displayed quasi-periodic bursts of ≈ 30 minutes duration every ≈ 2 hours. The observations indicate the presence of an unstable magneticallyregulated accretion mode, revealing the existence of magnetically gated accretion 3−5 , where disk material builds up around the magnetospheric boundary (at the co-rotation radius) and then accretes onto the white dwarf, producing bursts powered by the release of gravitational potential energy. We infer a surface magnetic field strength for the white dwarf in MV Lyr between 2 × 10 4 ≤ B ≤ 10 5 Gauss, too low to be detectable by other current methods. Our discovery provides a new way of studying the strength and evolution of magnetic fields in accreting white dwarfs and extends the connections between accretion onto white dwarfs, young stellar objects and neutron stars, for which similar magnetically gated accretion cysles have been identified 6−9 .MV Lyr spends most of its time in an optically bright (m V ≈ 12) luminosity state. Occasionally and sporadically (typically about once every few years) it drops by more than a factor 250 in brightness for short durations (weeks to months), sometimes fading to m V ≈ 18 (Fig 1a). Other accreting white dwarfs show similar optical brightness variations, and fall under the class of so-called nova-like variables 10−13 . The physical mechanism for these sudden drops in brightness is not well established 14−16 . As the luminosity of these systems is dominated by the release of gravitational potential energy of the gas in the disk, it is clear that the brightness variations are a direct consequence of changes in the mass-transfer rate through the accretion disk in these systems: during the bright phases ("high states"), the mass-transfer rate can be as high as 10 −8 M /yr, whilst during the faint phases ("low states"), the mass transfer rate can drop as low as 10 −11 M /yr (refs 12, 13).MV Lyr was continuously monitored during the original Kepler mission in short cadence mode (58.8 seconds) for nearly 4 years, displaying both high and low states during this interval (Fig 1a). Although its orbital period has been determined to be 3.19 hours via phase-resolved spectroscopy 18 , the Kepler lightcurve does not display any coherent periodicity during the full observation, possibly due to the very low system inclination 18,19 (i = 10 o ± 3 o ). Instead the Kepler data displays all the ...

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A Magnetic Explanation for the Rapid Burster

Cited by 3 publications

References 2 publications

Jets from Accreting Magnetic Young Stellar Objects. II. Mechanism Physics

Jets from Accreting Magnetic Young Stellar Objects. II. Mechanism Physics

A population study of type II bursts in the Rapid Burster

Magnetically gated accretion in an accreting ‘non-magnetic’ white dwarf

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