Radio emission from AXP and XDINS

Malofeev, V. M.; Malov, O. I.; Teplykh, D. A.

doi:10.1007/s10509-007-9341-y

Cited by 33 publications

(24 citation statements)

References 23 publications

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“…We found that as soon as magnetar oscillations are taken into account, their death lines in the P − B diagram shift downward and the conditions necessary for the generation of radio emission in the magnetosphere are met. Present observations (Malofeev et al (2007), Malofeev et al (2010)) showing a close connection between the burst activity of magnetars and sporadic detection of the radio emission from some magnetars are naturally accounted for within our interpretation.…”

supporting

confidence: 81%

Influence of stellar oscillations on pulsar and magnetar magnetospheres

2011

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Abstract. We investigated influence of stellar oscillations on the electrodynamics of pulsars as well as magnetars magnetosphere. Besides finding noticeable modification of electromagnetic field and charge density in the polar cap vicinity of oscillating neutron stars we proposed qualitative hypotheses explaining phenomena of part time pulsars as well as sporadic radio emission from generally radio-quiet magnetars with the help of stellar oscillations.Keywords. Stars: neutron, stars: oscillations, (stars:) pulsars: general.Investigations of oscillating neutron stars are motivated by the detection of quasiperiodic oscillations (QPOs) in the spectra of soft gamma-ray repeaters (SGRs), which are thought to be neutron stars with very strong magnetic fields (Duncan & Thompson (1992)). The idea that stellar oscillations may induce high energy emission in neutron star magnetospheres was developed in a series of papers by Timokhin and collaborators (see Timokhin et al. (2000), Timokhin et al. (2008)), after the first pioneering investigations in McDermott et al. (1984), Muslimov & Tsygan (1986) and Rezzolla & Ahmedov (2004), where the case of an oscillating neutron star in a vacuum was considered. Starting from Abdikamalov et al. (2009), where the theoretical basis of our approach was developed, in a series of papers (Morozova et al. (2010), Morozova et al. (2012), Zanotti et al. (2012)) we have explored the influence of neutron star oscillations on such characteristics of pulsar and magnetar magnetosphere as charge density and electromagnetic field in the polar cap region of the magnetosphere, electromagnetic energy losses as well as conditions for the charged particles acceleration in the magnetosphere. In our research we used toroidal model of stellar oscillations described in Unno et al. (1989).In Morozova et al. (2010) we explored the magnetosphere of a slowly rotating magnetized neutron star subject to toroidal oscillations in the relativistic regime. Under the assumption of a zero inclination angle between the magnetic moment and the angular momentum of the star, we analysed the Goldreich-Julian charge density and derived a second-order differential equation for the electrostatic potential. The analytical solution of this equation in the polar cap region of the magnetosphere revealed noticeable modification induced by oscillations on the accelerating electric field and on the charge density. We found that, after decomposing the oscillation velocity in terms of spherical harmonics, the first few modes with m = 0, 1 are responsible for energy losses that are almost linearly dependent on the amplitude of the oscillations and that, for the mode (l, m) = (2, 1), can be a factor ∼ 8 larger than the rotational energy losses, even for a velocity oscillation amplitude small in comparison with the linear velocity of stellar rotation. Based on these results we proposed a qualitative model for the explanation of the phenomenology of intermittent pulsars (Lyne (2009)

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confidence: 81%

Influence of stellar oscillations on pulsar and magnetar magnetospheres

2011

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“…Also, the non-detection of radio emission from X-ray dim isolated neutron stars (XDINSs) thus far (Kondratiev et al 2009), could be due to the beams of these long-period sources being quite narrow at high frequencies and there may be a better chance to detect them in radio at LOFAR frequencies. In fact, weak radio emission from two XDINSs, RX J1308.6+2127 and RX J2143.0+0654, was reported by Malofeev et al (2005Malofeev et al ( , 2007 at 111 MHz, hence it would be important to confirm this detection with LOFAR. This is also the case for the pulsars discovered in blind searches of Fermi gamma-ray photons, many of which do not exhibit detectable radio emission (Abdo et al 2009(Abdo et al , 2010b, as well as the remaining unidentified gamma-ray sources, which have characteristics of radio pulsars but which have not yet been detected in the radio (Abdo et al 2010a).…”

Section: New Populationsmentioning

confidence: 97%

Observing pulsars and fast transients with LOFAR

Stappers

Hessels

Alexov

et al. 2011

A&A

215

160

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Low frequency radio waves, while challenging to observe, are a rich source of information about pulsars. The LOw Frequency ARray (LOFAR) is a new radio interferometer operating in the lowest 4 octaves of the ionospheric "radio window": 10-240 MHz, that will greatly facilitate observing pulsars at low radio frequencies. Through the huge collecting area, long baselines, and flexible digital hardware, it is expected that LOFAR will revolutionize radio astronomy at the lowest frequencies visible from Earth. LOFAR is a next-generation radio telescope and a pathfinder to the Square Kilometre Array (SKA), in that it incorporates advanced multi-beaming techniques between thousands of individual elements. We discuss the motivation for low-frequency pulsar observations in general and the potential of LOFAR in addressing these science goals. We present LOFAR as it is designed to perform high-time-resolution observations of pulsars and other fast transients, and outline the various relevant observing modes and data reduction pipelines that are already or will soon be implemented to facilitate these observations. A number of results obtained from commissioning observations are presented to demonstrate the exciting potential of the telescope. This paper outlines the case for low frequency pulsar observations and is also intended to serve as a reference for upcoming pulsar/fast transient science papers with LOFAR.

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“…X-ray pulsations (P = 3-12 s) have Based on observations collected at ESO, Paranal, under Programmes 66.D-0128(A), 078.D-0162(A). 1 The claimed low-frequency pulsed emission from two of them (Malofeev et al 2007) has not been confirmed yet.…”

Section: Introductionmentioning

confidence: 97%

VLT optical observations of the isolated neutron star RX J0420.0-5022

Mignani¹,

Motch

Haberl

et al. 2009

A&A

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Context. X-ray observations performed with the Röntgen Satellite (ROSAT) led to the discovery of seven radio-silent isolated neutron stars (INSs) which are detected only through the relatively dim and purely thermal X-ray emission from the cooling star surface. A few of these INSs (X-ray Dim INSs, or XDINSs) have been also detected at optical wavelengths where they seem to feature thermal spectra. Optical studies of XDINSs thus play a crucial role in mapping the temperature distribution on the neutron star surface and in investigating the existence of an atmosphere around the neutron star. Aims. The aim of this work is to investigate the optical identification of the XDINS RX J0420.0−5022, tentatively proposed in the literature based on Very Large Telescope (VLT) observations. Methods. We re-analysed the original VLT observations of the proposed counterpart to assess its detection significance and we performed deeper VLT observations aiming at a higher confidence detection. Results. With a ∼2σ detection significance and a re-computed flux of B = 27.52 ± 0.61, we cannot rule out that the proposed counterpart was spurious and produced by the halo of a very bright nearby star. While we could not detect the proposed counterpart in our deeper VLT observations, we found evidence for a marginally significant (∼3.9σ) detection of a similarly faint object (B = 27.5 ± 0.3), ≈0. 5 north of it and coincident with the updated Chandra position of RX J0420.0−5022. Interestingly, the angular separation is consistent with the upper limit on the RX J0420.0−5022 proper motion, which suggests that we might have actually detected the originally proposed counterpart. From the flux of the putative RX J0420.0−5022 counterpart we can rule out a >7 optical excess with respect to the extrapolation of the XMM-Newton spectrum. Conclusions. High spatial resolution observations with the refurbished Hubble Space Telescope (HST) are the only way to confirm the detection of the putative candidate counterpart and to validate its identification with RX J0420.0−5022.

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Radio emission from AXP and XDINS

Cited by 33 publications

References 23 publications

Influence of stellar oscillations on pulsar and magnetar magnetospheres

Influence of stellar oscillations on pulsar and magnetar magnetospheres

Observing pulsars and fast transients with LOFAR

VLT optical observations of the isolated neutron star RX J0420.0-5022

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