Frequency Dependence of Pulse Width for 150 Radio Normal Pulsars

Chen, J. L.; Wang, Hong Guang

doi:10.1088/0067-0049/215/1/11

Cited by 42 publications

(54 citation statements)

References 62 publications

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“…Mitra & Rankin 2002). Assuming a power law dependence of the frequency on widths, W ν ∝ ν a , we find, a ∼-0.19 ± 0.1, which agrees with previous results (Mitra & Deshpande 1999;Mitra & Rankin 2002;Chen & Wang 2014). There was one notable exception to the above results, PSR J1034-3224, where the ratio of widths was significantly larger than unity.…”

Section: Pulse Widthssupporting

confidence: 92%

Meterwavelength Single-Pulse Polarimetric Emission Survey

Mitra

Basu

Maciesiak

et al. 2016

ApJ

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We have conducted the Meterwavelength Single-pulse Polarimetric Emission Survey to study the radio emission properties of normal pulsars. A total of 123 pulsars with periods between 0.1 seconds and 8.5 seconds were observed in the survey at two different frequencies, 105 profiles at 333 MHz, 118 profiles at 618 MHz and 100 pulsars at both. In this work we concentrate primarily on the time-averaged properties of the pulsar emission. The measured widths of the pulsar profiles in our sample usually exhibit the radius to frequency mapping. We validate the existence of lower bounds for the distribution of profile widths with pulsar period (P ), which is seen for multiple definitions of the width, viz. a lower boundary line (LBL) at 2.7 • P −0.5 with width measured at 50% level of profile peak, a LBL at 5.7 • P −0.5 for 10% level of peak and LBL at 6.3 • P −0.5 for width defined as 5σ above the baseline level. In addition we have measured the degree of linear polarization in the average profile of pulsars and confirmed their dependence on pulsar spindown energy loss (Ė). The single pulse polarization data show interesting trends with the polarization position angle (PPA) distribution exhibiting the simple rotating vector model for highĖ pulsars while the PPA becomes more complex for medium and lowĖ pulsars. The single pulse total intensity data is useful for studying a number of emission properties from pulsars like subpulse drifting, nulling and mode changing which is being explored in separate works.

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Section: Pulse Widthssupporting

confidence: 92%

Meterwavelength Single-Pulse Polarimetric Emission Survey

Mitra

Basu

Maciesiak

et al. 2016

ApJ

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“…Thus, despite the low frequencies involved the interplay between GR and plasma effects in pulsars may potentially be within observable ranges (Popov et al 2006;Malov & Malofeev 2010;Stappers et al 2011). It is also significant to note the existence of a subset of radio pulsars with pulse widths that broaden with increasing frequency (Chen & Wang 2014), also seen in Figs. 4 and 5 for the toy light curves generated here.…”

Section: Discussionmentioning

confidence: 73%

“…Normal radio pulsars show a rich variety of frequencydependent behaviours (Chen & Wang 2014). A proportionality constant 10 3 < κ < 10 5 is needed to describe the dense environment surrounding these objects (Istomin 2001).…”

Section: Discussionmentioning

confidence: 99%

Frequency-dependent effects of gravitational lensing within plasma

Rogers

2015

Monthly Notices of the Royal Astronomical Society

132

120

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The interaction between refraction from a distribution of inhomogeneous plasma and gravitational lensing introduces novel effects to the paths of light rays passing by a massive object. The plasma contributes additional terms to the equations of motion, and the resulting ray trajectories are frequency-dependent. Lensing phenomena and circular orbits are investigated for plasma density distributions N ∝ 1/r h with h ≥ 0 in the Schwarzschild space-time. For rays passing by the mass near the plasma frequency refractive effects can dominate, effectively turning the gravitational lens into a mirror. We obtain the turning points, circular orbit radii, and angular momentum for general h. Previous results have shown that light rays behave like massive particles with an effective mass given by the plasma frequency for a constant density h = 0. We study the behaviour for general h and show that when h = 2 the plasma term acts like an additional contribution to the angular momentum of the passing ray. When h = 3 the potential and radii of circular orbits are analogous to those found in studies of massless scalar fields on the Schwarzschild background. As a physically motivated example we study the pulse profiles of a compact object with antipodal hotspots sheathed in a dense plasma, which shows dramatic frequency-dependent shifts from the behaviour in vacuum. Finally, we consider the potential observability and applications of such frequency-dependent plasma effects in general relativity for several types of neutron star.

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“…4.1). Chen & Wang (2014), who recently analysed the pulse width evolution with frequency of 150 pulsars from the EPN database, reached a similar conclusion: the emission must be broad-band, and the observed behaviour of width at different frequencies is caused by spectral changes along the flux tube. They found that if the spectral index variation along pulse phase is symmetric, there can be either canonical RFM or anti-RFM, while in cases where there are substantial deviations from the symmetric case, then there can be the non-monotonic trends of w 10 with ν, which we also observed.…”

Section: Some Examples Of Unexpected Profile Evolutionmentioning

confidence: 75%

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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Frequency Dependence of Pulse Width for 150 Radio Normal Pulsars

Cited by 42 publications

References 62 publications

Meterwavelength Single-Pulse Polarimetric Emission Survey

Meterwavelength Single-Pulse Polarimetric Emission Survey

Frequency-dependent effects of gravitational lensing within plasma

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

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