NON-DETECTION IN A
                    <i>FERMI</i>
                    /LAT OBSERVATION OF AXP 4U 0142+61: MAGNETARS?

Tong, H.; Song, Liming; Xu, R. X.

doi:10.1088/2041-8205/725/2/l196

Cited by 19 publications

(22 citation statements)

References 28 publications

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“…Thus, excludes the possibility to be a RPP, wherė E NS rot > L X . Recent observations of Fermi satellite [16][17][18] does not find evidences of γ radiation. Furthermore, were detected 4 SGRs/AXPs that emit in wavelength of radio, while for the others not.…”

Section: Difficulties With the Magnetar Modelmentioning

confidence: 99%

Magnetars and white dwarf pulsars

Lobato

Malheiro

Coelho

2016

Int. J. Mod. Phys. D

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The Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs) are a class of pulsars understood as neutron stars (NSs) with super strong surface magnetic fields, namely B 10 14 G, and for that reason are known as Magnetars. However, in the last years some SGRs/AXPs with low surface magnetic fields B ∼ (10 12 − 10 13 ) G have been detected, challenging the Magnetar description. Moreover, some fast and very magnetic white dwarfs (WDs) have also been observed, and at least one showed X-Ray energy emission as an ordinary pulsar. Following this fact, an alternative model based on white dwarfs pulsars has been proposed to explain this special class of pulsars. In this model, AXPs and SGRs as dense and magnetized white dwarfs can have surface magnetic field B ∼ 10 7 − 10 10 G and rotate very fast with frequencies Ω ∼ 1 rad/s, consistent with the observed rotation periods P ∼ (2 − 12) s.

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Section: Difficulties With the Magnetar Modelmentioning

confidence: 99%

Magnetars and white dwarf pulsars

Lobato

Malheiro

Coelho

2016

Int. J. Mod. Phys. D

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“…This point is clearly demonstrated by the discovery of the low magnetic field magnetar SGR 0418+5729 (with a characteristic magnetic field less than 7.5 × 10 12 G [67]). Furthermore, there are other observations arguing against a strong dipole field in magnetars [80]: the supernova energies associated with magnetars are of normal value [88]; the non-detection of magnetars by Fermi-LAT [76,77]; and the variable period derivative of magnetars (by a factor of several or more; on days or months time scale) etc. The variable spin down rate may be viewed as the direct evidence of magnetospheric torques [75,80].…”

Section: Wind Braking Of Magnetarsmentioning

confidence: 99%

Pulsar braking: magnetodipole vs. wind

Tong

2015

Sci. China Phys. Mech. Astron.

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Pulsars are good clocks in the universe. One fundamental question is that why they are good clocks? This is related to the braking mechanism of pulsars. Nowadays pulsar timing is done with unprecedented accuracy. More pulsars have braking indices measured. The period derivative of intermittent pulsars and magnetars can vary by a factor of several. However, during pulsar studies, the magnetic dipole braking in vacuum is still often assumed. It is shown that the fundamental assumption of magnetic dipole braking (vacuum condition) does not exist and it is not consistent with the observations. The physical torque must consider the presence of the pulsar magnetosphere. Among various efforts, the wind braking model can explain many observations of pulsars and magnetars in a unified way. It is also consistent with the up-to-date observations. It is time for a paradigm shift in pulsar studies: from magnetic dipole braking to wind braking. As one alternative to the magnetospheric model, the fallback disk model is also discussed. Tong H. Pulsar braking: magnetodipole vs. wind.

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“…In the presence of a particle wind, vacuum gaps may not be formed, e.g., outer gap etc. This may explain the conflicts between outer gap model in the case of magnetars and Fermi observations (Tong et al 2010a space charge limited flow type acceleration mechanism may still exist (Xu 2007). In a wind loaded magnetosphere, detailed calculations of space charge limited flows are needed in the future.…”

Section: The Maximum Acceleration Potential In Pulsar Open Field Linementioning

confidence: 99%

Wind Braking of Magnetars

Tong

Song

et al. 2013

ApJ

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Considering recent observations challenging the traditional magnetar model, we explore the wind braking of magnetars. There is evidence for strong multipole magnetic fields in active magnetars, but the dipole field inferred from spin down measurements may be strongly biased by a particle wind. Recent challenging observations of magnetars may be explained naturally in the wind braking scenario: (1) The supernova energies of magnetars are of normal value; (2) The non-detection in Fermi observations of magnetars; (3) The problem posed by the low-magnetic field soft gamma-ray repeaters; (4) The relation between magnetars and high magnetic field pulsars; (5) A decreasing period derivative during magnetar outbursts. Transient magnetars with L x < −Ė rot may still be magnetic dipole braking. This may explain why low luminosity magnetars are more likely to have radio emissions. A strong reduction of dipole magnetic field is possible only when the particle wind is very collimated at the star surface. A small reduction of dipole magnetic field may result from detailed considerations of magnetar wind luminosity. In the wind braking scenario, magnetars are neutron stars with strong multipole field. For some sources, a strong dipole field may be no longer needed. A magnetism-powered pulsar wind nebula will be one of the consequences of wind braking. For a magnetism-powered pulsar wind nebula, we should see a correlation between the nebula luminosity and the magnetar luminosity. Under the wind braking scenario, a braking index smaller than three is expected. Future braking index measurement of a magnetar may tell us whether magnetars are wind braking or magnetic dipole braking.

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NON-DETECTION IN A FERMI /LAT OBSERVATION OF AXP 4U 0142+61: MAGNETARS?

Cited by 19 publications

References 28 publications

Magnetars and white dwarf pulsars

Magnetars and white dwarf pulsars

Pulsar braking: magnetodipole vs. wind

Wind Braking of Magnetars

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