Understanding the Radio Emission Geometry of PSR B0329+54

Gangadhara, R. T.; Gupta, Yashwant

doi:10.1086/321439

Cited by 138 publications

(164 citation statements)

References 16 publications

Supporting

Mentioning

155

Contrasting

Order By: Relevance

“…6. We are aware that this is only a crude approximation, as it has been shown that the profile consists of at least five (Kramer 1994) or even nine components (Gangadhara & Gupta 2001), but we believe that more complicated analysis will not alter the results significantly. We note that the windows chosen are adequate for the profiles at all frequencies.…”

Section: Correlations Between Frequenciesmentioning

confidence: 96%

Simultaneous single-pulse observations of radio pulsars

Krämer

Karastergiou

Gupta

et al. 2003

A&A

Self Cite

View full text Add to dashboard Cite

Abstract.In this paper we demonstrate that a large, unexplored reservoir of information about pulsar emission exists, that is directly linked to the radiating particles and their radiation process: We present a study of flux density measurements of individual pulses simultaneously observed at four different frequencies. Correcting for effects caused by the interstellar medium, we derive intrinsic flux density spectra of individual radio pulses observed at several frequencies for the first time. Pulsar B0329+54 was observed at 238, 626, 1412 and 4850 MHz, while observations of PSR B1133+16 were made at 341, 626, 1412 and 4850 MHz. We derive intrinsic pulse-to-pulse modulation indices which show a minimum around 1 GHz. Correlations between the flux densities of different frequency pairs worsen as the frequency separation widens and also tend to be worse for outer profile components. The single pulse spectra of PSR B0329+54 resemble the spectra of the integrated profile. However, the spectral index distributions for the single pulses of PSR B1133+16 show significant deviations from a Gaussian. This asymmetry is caused by very strong pulses with flux densities exceeding the mean value by more than a factor of ten. These strong pulses occur preferentially at the trailing edge of the leading component and appear to be broadband in most cases. Their properties are similar to those of so-called giant pulses, suggesting that these phenomena are related.

show abstract

Section: Correlations Between Frequenciesmentioning

confidence: 96%

Simultaneous single-pulse observations of radio pulsars

Krämer

Karastergiou

Gupta

et al. 2003

A&A

Self Cite

View full text Add to dashboard Cite

show abstract

“…ρ ≈ 86 • (r em /R LC ) 1/2 (see e.g. Gangadhara & Gupta 2001). We should note that this expression implicitly assumes a perfectly aligned rotator, where the maximum co-rotating radius along the last open field line is R LC .…”

Section: Psr B1133+16mentioning

confidence: 99%

Pulsar polarisation below 200 MHz: Average profiles and propagation effects

Noutsos

Sobey

Kondratiev

et al. 2015

A&A

110

View full text Add to dashboard Cite

Aims. We present the highest-quality polarisation profiles to date of 16 non-recycled pulsars and four millisecond pulsars, observed below 200 MHz with the LOFAR high-band antennas. Based on the observed profiles, we perform an initial investigation of expected observational effects resulting from the propagation of polarised emission in the pulsar magnetosphere and the interstellar medium. Methods. The polarisation data presented in this paper have been calibrated for the geometric-projection and beam-shape effects that distort the polarised information as detected with the LOFAR antennas. We have used RM Synthesis to determine the amount of Faraday rotation in the data at the time of the observations. The ionospheric contribution to the measured Faraday rotation was estimated using a model of the ionosphere. To study the propagation effects, we have compared our low-frequency polarisation observations with archival data at 240, 400, 600, and 1400 MHz. Results. The predictions of magnetospheric birefringence in pulsars have been tested using spectra of the pulse width and fractional polarisation from multifrequency data. The derived spectra offer only partial support for the expected effects of birefringence on the polarisation properties, with only about half of our sample being consistent with the model's predictions. It is noted that for some pulsars these measurements are contaminated by the effects of interstellar scattering. For a number of pulsars in our sample, we have observed significant variations in the amount of Faraday rotation as a function of pulse phase, which is possibly an artefact of scattering. These variations are typically two orders of magnitude smaller than that observed at 1400 MHz by Noutsos et al. (2009), for a different sample of southern pulsars. In this paper we present a possible explanation for the difference in magnitude of this effect between the two frequencies, based on scattering. Finally, we have estimated the magnetospheric emission heights of low-frequency radiation from four pulsars, based on the phase lags between the flux-density and the PA profiles, and the theoretical framework of Blaskiewicz et al. (1991, ApJ, 370, 643). These estimates yielded heights of a few hundred km; at least for PSR B1133+16, this is consistent with emission heights derived based on radius-to-frequency mapping, but is up to a few times larger than the recent upper limit based on pulsar timing. Conclusions. Our work has shown that models, like magnetospheric birefringence, cannot be the sole explanation for the complex polarisation behaviour of pulsars. On the other hand, we have reinforced the claim that interstellar scattering can introduce a rotation of the PA with frequency that is indistinguishable from Faraday rotation and also varies as a function of pulse phase. In one case, the derived emission heights appear to be consistent with the predictions of radius-to-frequency mapping at 150 MHz, although this interpretation is subject to a number of systematic uncertainties.

show abstract

“…The lower limit on θ 0 can be deduced from the absence of frequency-dependent arrival delays in the midpoint φ mid (ν). For this, we use the derivations of Gangadhara & Gupta (2001). If frequencies ν 1 and ν 2 are emitted at radii r 1 and r 2 from the centre of the star, then the light travel time delay (retardation) between those two frequencies will be:…”

Section: Where Does the Emission Originate?mentioning

confidence: 99%

LOFAR observations of PSR B0943+10: profile evolution and discovery of a systematically changing profile delay in bright mode

Bilous

Hessels

Kondratiev

et al. 2014

A&A

View full text Add to dashboard Cite

We present broadband, low-frequency (25−80 MHz and 110−190 MHz) LOFAR observations of PSR B0943+10, with the goal of better illuminating the nature of its enigmatic mode-switching behaviour. This pulsar shows two relatively stable states: a "bright" (B) and "quiet" (Q) mode, each with different characteristic brightness, profile morphology, and single-pulse properties. We model the average profile evolution both in frequency and time from the onset of each mode, and highlight the differences between the two modes. In both modes, the profile evolution can be explained well by radius-to-frequency mapping at altitudes within a few hundred kilometres of the stellar surface. If both B and Q-mode emissions originate at the same magnetic latitude, then we find that the change of emission height between the modes is less than 6%. We also find that, during B-mode, the average profile is gradually shifting towards later spin phase and then resets its position at the next Q-to-B transition. The observed B-mode profile delay is frequencyindependent (at least from 25−80 MHz) and asymptotically changes towards a stable value of about 4 × 10 −3 in spin phase by the end of mode instance, so much too high to be due to a changing spin-down rate. Such a delay can be interpreted as a gradual movement of the emission cone against the pulsar's direction of rotation, with different field lines being illuminated over time. Another interesting explanation is a possible variation in the accelerating potential inside the polar gap. This explanation connects the observed profile delay to the gradually evolving subpulse drift rate, which depends on the gradient of the potential across the field lines.

show abstract

Understanding the Radio Emission Geometry of PSR B0329+54

Cited by 138 publications

References 16 publications

Simultaneous single-pulse observations of radio pulsars

Simultaneous single-pulse observations of radio pulsars

Pulsar polarisation below 200 MHz: Average profiles and propagation effects

LOFAR observations of PSR B0943+10: profile evolution and discovery of a systematically changing profile delay in bright mode

Contact Info

Product

Resources

About