Toward an empirical theory of pulsar emission. IV - Geometry of the core emission region

Rankin, Joanna M.

doi:10.1086/168530

Cited by 339 publications

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“…The widths follow an inverse dependency with the pulsar period, consistent with previous analyses at higher frequencies (e.g. Rankin 1990;Maciesiak et al 2011; but also Gil et al 1993;Arzoumanian et al 2002) and at these frequencies (Kuzmin & Losovsky 1999). In general, broadening by external effects may also be expected, even though not dominant: while we were careful to avoid evidently scattered profiles in our sample, DM smearing can also contaminate it.…”

Section: Pulse Widthssupporting

confidence: 89%

Wide-band, low-frequency pulse profiles of 100 radio pulsars with LOFAR

Pilia

Hessels

Stappers

et al. 2016

A&A

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Context. LOFAR offers the unique capability of observing pulsars across the 10−240 MHz frequency range with a fractional bandwidth of roughly 50%. This spectral range is well suited for studying the frequency evolution of pulse profile morphology caused by both intrinsic and extrinsic effects such as changing emission altitude in the pulsar magnetosphere or scatter broadening by the interstellar medium, respectively. Aims. The magnitude of most of these effects increases rapidly towards low frequencies. LOFAR can thus address a number of open questions about the nature of radio pulsar emission and its propagation through the interstellar medium. Methods. We present the average pulse profiles of 100 pulsars observed in the two LOFAR frequency bands: high band (120-167 MHz, 100 profiles) and low band (15-62 MHz, 26 profiles). We compare them with Westerbork Synthesis Radio Telescope (WSRT) and Lovell Telescope observations at higher frequencies (350 and 1400 MHz) to study the profile evolution. The profiles were aligned in absolute phase by folding with a new set of timing solutions from the Lovell Telescope, which we present along with precise dispersion measures obtained with LOFAR. Results. We find that the profile evolution with decreasing radio frequency does not follow a specific trend; depending on the geometry of the pulsar, new components can enter into or be hidden from view. Nonetheless, in general our observations confirm the widening of pulsar profiles at low frequencies, as expected from radius-to-frequency mapping or birefringence theories.

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Section: Pulse Widthssupporting

confidence: 89%

Wide-band, low-frequency pulse profiles of 100 radio pulsars with LOFAR

Pilia

Hessels

Stappers

et al. 2016

A&A

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“…However, it is pointed out by Karastergiou & Johnston (2004) that the change in handedness of the circular polarization in the MP suggests that the entire MP is a core component. This in contrast to the classification made by Rankin (1990), who classified the MP as a core component with conal outriders making it a triple profile, while the IP is classified as a core single component. …”

Section: The Polarization Profilecontrasting

confidence: 75%

The main-interpulse interaction of PSR B1702–19

Weltevrede¹,

Wright²,

Stappers³

2007

A&A

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Aims. This paper reports on single-pulse radio observations of PSR B1702-19 and their implications for pulsar emission theories. Methods. These observations were made with the Westerbork Synthesis Radio Telescope at 1380 and 328 MHz. The PA-swing is used to constrain possible geometries of the pulsar and the single-pulse data is analysed for subpulse modulation correlations between the main pulse and interpulse. Results. We confirm earlier conclusions that the dipole axis of this pulsar is almost perpendicular to its rotation axis, and report that both its main pulse and interpulse are modulated with a periodicity around 10.4 times the pulsar's rotation. Allowing for the half-period delay between main pulse and interpulse the modulation is found to be precisely in phase. Despite small secular variations in the periodicity, the phase-locking continues over all timescales ranging up to several years. Conclusions. The precision of the phase locking is difficult for current emission theories to explain if the main pulse and interpulse originate from opposing magnetic poles. We therefore also explore the possibility of a bidirectional model, in which all the modulated emission comes from one pole, but is seen from two sides and slightly displaced by aberration and time-delay. In this model the unmodulated emission is directed to us from the opposite pole, requiring the emission of the main pulse to originate from two different poles. This is difficult to reconcile with the observed smooth PA-swing. Whichever model turns out to be correct, the answer will have important implications for emission theories.Key words. stars: pulsars: individual: PSR B1702-19 -stars: pulsars: general -radiation mechanisms: non-thermal IntroductionThe radio pulsar B1702-19 was discovered by Manchester et al. (1978) in the second Molonglo Survey. With a period of 0.3 s, a characteristic age of 1.1 Myr and inferred surface magnetic field 1.1 × 10 12 Gauss, the pulsar was in no way unusual. However, some ten years later it was found to have an interpulse located some 180 • from the main pulse (Biggs et al. 1988), an unusual feature among pulsars, and one which has the potential for testing magnetosphere and emission models.Radio pulsars have narrow emission beams, so that an interpulse (henceforth IP) located close to 180 • from the main pulse (henceforth MP) might naturally be interpreted as a view of a second magnetic pole. Previous studies of PSR B1702-19 have tended to support this view. For example, according to Biggs et al. (1988), there is little evidence for the MP-IP separation (given as 181 • ± 1 • ) to evolve with frequency. Further support is given by the analyses of the shape of the polarisation position angle swing in and Kuzmin (1989), which is more recently confirmed by van Ommen et al. (1997). However, geometric models exist (e.g. Gil 1985;Dyks et al. 2005b) in which even a separation of this magnitude can arise from a single pole.The structure of the MP is essentially double-peaked at all frequencies, the leading pe...

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“…However, Rankin (1990) and Kramer et al (1998) have presented strong evidence in favor of a low altitude (r ≈ R * ) dipole geometry for the site of the core component of pulsar radio emission. Arons (1993) gave evidence that spun up millisecond pulsars must have substantially dipolar fields at low altitute.…”

Section: Introductionmentioning

confidence: 99%

Pulsar Death at an Advanced Age

Arons

1996

International Astronomical Union Colloquium

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Abstract. I summarize the theory of acceleration of non-neutral particle beams by starvation electric fields along the polar magnetic field lines of rotation powered pulsars, including the effect of dragging of inertial frames which dominates the acceleration of a space charge limited beam. I apply these results to a new calculation of the radio pulsar death line, under the hypotheses that pulsar "death" corresponds to cessation of pair creation over the magnetic poles and that the magnetic field has a locally dipolar topology. The frame dragging effect in star centered dipole geometry does improve comparison of the theory with observation, but an unacceptably large conflict between observation and theory still persists. Offsetting the dipole improves the comparison, but a fully satisfactory theory requires incorporating magnetic conversion of inverse Compton gamma rays, created by scattering thermal photons from the surface of old neutron stars (t > 10 8 years) kept warm (T ≥ 10 5 K) by friction between the rotating core and the crust. The result is a "death valley" for pulsars; offsets of the dipole center from the stellar center in the oldest stars ∼ (0.7 − 0.8)R * suffice. The resulting theory predicted the existence of rotation powered pulsars with these advanced ages, a prediction confirmed by the recent discovery that PSR J2144-3933 actually has a rotation period of 8.5 seconds.

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Toward an empirical theory of pulsar emission. IV - Geometry of the core emission region

Cited by 339 publications

References 0 publications

Wide-band, low-frequency pulse profiles of 100 radio pulsars with LOFAR

Wide-band, low-frequency pulse profiles of 100 radio pulsars with LOFAR

The main-interpulse interaction of PSR B1702–19

Pulsar Death at an Advanced Age

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