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M Kramer - One of the best experts on this subject based on the ideXlab platform.
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first detection of frequency dependent time variable Dispersion Measures
Astronomy and Astrophysics, 2019Co-Authors: J Y Donner, M Kramer, S Oslowski, J P W Verbiest, C Tiburzi, D Michilli, M Serylak, J Anderson, A Horneffer, J M GriesmeierAbstract:Context. High-precision pulsar-timing experiments are affected by temporal variations of the Dispersion Measure (DM), which are related to spatial variations in the interstellar electron content and the varying line of sight to the source. Correcting for DM variations relies on the cold-plasma Dispersion law which states that the dispersive delay varies with the squared inverse of the observing frequency. This may, however, give incorrect Measurements if the probed electron content (and therefore the DM) varies with observing frequency, as is predicted theoretically due to the different refraction angles at different frequencies. Context. High-precision pulsar-timing experiments are affected by temporal variations of the Dispersion Measure (DM), which are related to spatial variations in the interstellar electron content and the varying line of sight to the source. Correcting for DM variations relies on the cold-plasma Dispersion law which states that the dispersive delay varies with the squared inverse of the observing frequency. This may, however, give incorrect Measurements if the probed electron content (and therefore the DM) varies with observing frequency, as is predicted theoretically due to the different refraction angles at different frequencies. Methods. We used high-cadence, low-frequency observations with three stations from the German LOng-Wavelength (GLOW) consortium, which are part of the LOw-Frequency ARray (LOFAR). Specifically, 3.5 yr of weekly observations of PSR J2219+4754 are presented. Results. We present the first detection of frequency-dependent DMs towards any interstellar object and a precise multi-year time-series of the time- and frequency-dependence of the Measured DMs. The observed DM variability is significant and may be caused by extreme scattering events. Potential causes for frequency-dependent DMs are quantified and evaluated. Conclusions. We conclude that frequency dependence of DMs has been reliably detected and is indeed caused by small-scale (up to tens of AUs) but steep density variations in the interstellar electron content. We find that long-term trends in DM variability equally affect DMs Measured at both ends of our frequency band and hence the negative impact on long-term high-precision timing projects is expected to be limited.
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model based asymptotically optimal Dispersion Measure correction for pulsar timing
Monthly Notices of the Royal Astronomical Society, 2014Co-Authors: C G Bassa, G H Janssen, R Karuppusamy, M Kramer, D Perrodin, R Smits, B W Stappers, R Van Haasteren, L LentatiAbstract:In order to reach the sensitivity required to detect gravitational waves, pulsar timing array experiments need to mitigate as much noise as possible in timing data. A dominant amount of noise is likely due to variations in the Dispersion Measure. To correct for such variations, we develop a statistical method inspired by the maximum likelihood estimator and optimal filtering. Our method consists of two major steps. First, the spectral index and amplitude of Dispersion Measure variations are Measured via a time-domain spectral analysis. Second, the linear optimal filter is constructed based on the model parameters found in the first step, and is used to extract the Dispersion Measure variation waveforms. Compared to current existing methods, this method has better time resolution for the study of short timescale Dispersion variations, and generally produces smaller errors in waveform estimations. This method can process irregularly sampled data without any interpolation because of its time-domain nature. Furthermore, it offers the possibility to interpolate or extrapolate the waveform estimation to regions where no data is available. Examples using simulated data sets are included for demonstration.
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timing the main sequence star binary pulsar j1740 3052
Monthly Notices of the Royal Astronomical Society, 2012Co-Authors: E C Madsen, G H Janssen, M Kramer, A G Lyne, G Hobbs, R N Manchester, I H Stairs, F Camilo, A PossentiAbstract:PSR J1740-3052 is a young pulsar in orbit around a companion that is most likely a B-type main-sequence star. Since its discovery more than a decade ago, data have been taken at several frequencies with instruments at the Green Bank, Parkes, Lovell and Westerbork telescopes. We Measure scattering time-scales in the pulse profiles and Dispersion Measure changes as a function of binary orbital phase and present evidence that both of these vary as would be expected due to a wind from the companion star. Using pulse arrival times that have been corrected for the observed periodic Dispersion Measure changes, we find a timing solution spanning from 1997 November to 2011 March. This includes Measurements of the advance of periastron, $\omega$??, and the change in the projected semimajor axis of the orbit, x??, and sets constraints on the orbital geometry. From these constraints, we estimate that the pulsar received a kick of at least ??50 km s-1 at birth. A quasi-periodic signal is present in the timing residuals with a period of 2.2 times the binary orbital period. The origin of this signal is unclear.
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timing the main sequence star binary pulsar j1740 3052
arXiv: High Energy Astrophysical Phenomena, 2012Co-Authors: E C Madsen, G H Janssen, M Kramer, A G Lyne, G Hobbs, R N Manchester, I H Stairs, F Camilo, A PossentiAbstract:PSR J1740-3052 is a young pulsar in orbit around a companion that is most likely a B-type main-sequence star. Since its discovery more than a decade ago, data have been taken at several frequencies with instruments at the Green Bank, Parkes, Lovell, and Westerbork telescopes. We Measure scattering timescales in the pulse profiles and Dispersion Measure changes as a function of binary orbital phase and present evidence that both of these vary as would be expected due to a wind from the companion star. Using pulse arrival times that have been corrected for the observed periodic Dispersion Measure changes, we find a timing solution spanning 1997 November to 2011 March. This includes Measurements of the advance of periastron and the change in the projected semimajor axis of the orbit and sets constraints on the orbital geometry. From these constraints, we estimate that the pulsar received a kick of at least ~50 km/s at birth. A quasi-periodic signal is present in the timing residuals with a period of 2.2 times the binary orbital period. The origin of this signal is unclear.
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wide band simultaneous observations of pulsars disentangling Dispersion Measure and profile variations disentangling Dispersion Measure and profile variations
Astronomy and Astrophysics, 2012Co-Authors: T E Hassall, M Kramer, B W Stappers, J W T Hessels, A Alexov, K Anderson, T Coenen, A KarastergiouAbstract:Dispersion in the interstellar medium is a well known phenomenon that follows a simple relationship, which has been used to predict the time delay of dispersed radio pulses since the late 1960s. We performed wide-band simultaneous observations of four pulsars with LOFAR (at 40-190 MHz), the 76-m Lovell Telescope (at 1400 MHz) and the Effelsberg 100-m Telescope (at 8000 MHz) to test the accuracy of the Dispersion law over a broad frequency range. In this paper we present the results of these observations which show that the Dispersion law is accurate to better than 1 part in 105 across our observing band. We use this fact to constrain some of the properties of the interstellar medium along the line-of-sight and use the lack of any aberration or retardation effects to determine upper limits on emission heights in the pulsar magnetosphere. We also discuss the effect of pulse profile evolution on our observations, and the implications that it could have for precision pulsar timing projects such as the detection of gravitational waves with pulsar timing arrays.
Bing Zhang - One of the best experts on this subject based on the ideXlab platform.
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Dispersion Measure variation of repeating fast radio burst sources
The Astrophysical Journal, 2017Co-Authors: Yuanpei Yang, Bing ZhangAbstract:The repeating fast radio burst (FRB) 121102 was recently localized in a dwarf galaxy at a cosmological distance. The Dispersion Measure (DM) derived for each burst from FRB 121102 so far has not shown significant evolution, even though an apparent increase was recently seen with newly detected VLA bursts. It is expected that more repeating FRB sources may be detected in the future. In this work, we investigate a list of possible astrophysical processes that might cause DM variation of a particular FRB source. The processes include (1) the cosmological scale effects such as Hubble expansion and large-scale structure fluctuations; (2) the FRB local effects such as gas density fluctuation, expansion of a supernova remnant, a pulsar wind nebula, and an HII region; and (3) the propagation effect due to plasma lensing. We find that the DM variations contributed by the large-scale structure are extremely small, and any observable DM variation is likely caused by the plasma local to the FRB source. Besides mechanisms that produce decreasing DM with time, we suggest that an FRB source in an expanding supernova remnant around a nearly neutral ambient medium during the deceleration (Sedov-Taylor and snowplow) phases or in a growing HII region can introduce DM increasing. Some effects (e.g. an FRB source moving in an HII region or plasma lensing) can give either positive or negative DM variations. Future observations of DM variations of FRB 121102 and other repeating FRB sources can bring important clues for the physical origin of these sources.
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large host galaxy Dispersion Measure of fast radio bursts
The Astrophysical Journal, 2017Co-Authors: Yuanpei Yang, Zhuo Li, Bing ZhangAbstract:Fast radio bursts (FRBs) have excessive Dispersion Measures (DMs) and an all-sky distribution, which point toward an extragalactic or even a cosmological origin. We develop a method to extract the mean host galaxy DM ($\left\langle{\rm DM_{HG,loc}}\right\rangle$) and the characterized luminosity ($L$) of FRBs using the observed DM-Flux data, based on the assumption of a narrow luminosity distribution. Applying Bayesian inference to the data of 21 FRBs, we derive a relatively large mean host DM, i.e. $\left\langle{\rm DM_{HG,loc}}\right\rangle \sim 270~\rm{pc~cm^{-3}}$ with a large Dispersion. A relatively large ${\rm DM_{HG}}$ of FRBs is also supported by the millisecond scattering times of some FRBs and the relatively small redshift $z=0.19273$ of FRB 121102 (which gives ${\rm DM_{HG,loc}} \sim 210 ~\rm{pc~cm^{-3}}$). The large host galaxy DM may be contributed by the ISM or a near-source plasma in the host galaxy. If it is contributed by the ISM, the type of the FRB host galaxies would not be Milky Way (MW)-like, consistent with the detected host of FRB 121102. We also discuss the possibility of having a near-source supernova remnant (SNR), pulsar wind nebula (PWN) or HII region that gives a significant contribution to the observed ${\rm DM_{HG}}$.
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extracting host galaxy Dispersion Measure and constraining cosmological parameters using fast radio burst data
The Astrophysical Journal, 2016Co-Authors: Yuanpei Yang, Bing ZhangAbstract:The excessive Dispersion Measures (DMs) and high Galactic latitudes of fast radio bursts (FRBs) hint toward a cosmological origin of these mysterious transients. Methods of using Measured DM and redshift z to study cosmology have been proposed, but one needs to assume a certain amount of DM contribution from the host galaxy () in order to apply those methods. We introduce a slope parameter (where is the observed DM subtracting the Galactic contribution), which can be directly Measured when a sample of FRBs have z Measured. We show that can be roughly inferred from β and the mean values, and , of the sample. Through Monte Carlo simulations, we show that the mean value of local host galaxy DM, , along with other cosmological parameters (mass density in the ΛCDM model, and the IGM portion of the baryon energy density ), can be independently Measured through Markov Chain Monte Carlo fitting to the data.
Yun-wei Yu - One of the best experts on this subject based on the ideXlab platform.
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radio emission from pulsar wind nebulae without surrounding supernova ejecta application to frb 121102
The Astrophysical Journal, 2017Co-Authors: Jieshuang Wang, Yun-wei YuAbstract:In this paper, we propose a new scenario in which a rapidly-rotating strongly-magnetized pulsar without any surrounding supernova ejecta produces fast radio bursts (FRBs) repeatedly via some mechanisms, and meanwhile, an ultra-relativistic electron/positron pair wind from the pulsar sweeps up its ambient dense interstellar medium, giving rise to a non-relativistic pulsar wind nebula (PWN). We show that the synchrotron radio emission from such a PWN is bright enough to account for the recently-discovered persistent radio source associated with the repeating FRB 121102 in reasonable ranges of the model parameters. In addition, our PWN scenario is consistent with the non-evolution of the Dispersion Measure inferred from all the repeating bursts observed in four years.
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revisiting the Dispersion Measure of fast radio bursts associated with gamma ray burst afterglows
The Astrophysical Journal, 2014Co-Authors: Yun-wei YuAbstract:Some fast radio bursts (FRBs) are expected to be associated with the afterglow emission of gamma-ray bursts (GRBs), while a short-lived, supermassive neutron star (NS) forms during the GRBs. I investigate the possible contributions to the Dispersion Measure (DM) of the FRBs from the GRB ejecta and the wind blown from the precollapsing NS. On the one hand, sometimes an internal X-ray plateau afterglow could be produced by the NS wind, which indicates that a great number of electron-positron pairs are carried by the wind. If the pair-generation radius satisfies a somewhat rigorous condition, the relativistic and dense wind would contribute a high DM to the associated FRB, which can be comparable to and even exceed the DM contributed by the intergalactic medium. On the other hand, if the wind only carries a Goldreich-Julian particle flux, its DM contribution would become negligible; meanwhile, the internal plateau afterglow would not appear. Alternatively, the FRB should be associated with a GRB afterglow produced by the GRB external shock, i.e., an energy-injection-caused shallow-decay afterglow or a normal single-power-law afterglow if the impulsive energy release of the GRB is high enough. In the latter case, the DM contributed by the high-mass GRB ejecta could be substantially important, in particular, for an environment of main-sequence stellar wind. In summary, a careful assessment on the various DM contributors could be required for the cosmological application of the expected FRB-GRB association. The future DM Measurements of GRB-associated FRBs could provide a constraint on the physics of NS winds.
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Dispersion Measure contributed by a relativistic neutron star wind and implication for fast radio bursts
arXiv: Solar and Stellar Astrophysics, 2014Co-Authors: Yun-wei YuAbstract:The possible contribution to Dispersion Measure (DM) by neutron star winds is investigated by introducing a relativistic definition of the DM. On one hand, I propose that the observed fast radio bursts (FRBs) could be produced by activities on some peculiar young Galactic neutron stars, where the large DMs of the FRBs can be ascribed to the neutron star winds rather than the intergalactic medium. On the other hand, in the sight of cosmological origin of FRBs, I also investigate the possible association of the FRBs with the collapses of millisecond magnetars harbored in gamma-ray bursts (GRBs). In particular, as required by the observed bright internal X-ray afterglows, a high intrinsic DM could be contributed by the emitting neutron star winds, which could even exceed the contribution from the intergalactic medium. In any case, such a result is strongly dependent on the uncertain dissipation mechanisms of the winds and more DM Measurements of FRBs could provide stringent constraints on the wind physics.
A Possenti - One of the best experts on this subject based on the ideXlab platform.
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timing the main sequence star binary pulsar j1740 3052
Monthly Notices of the Royal Astronomical Society, 2012Co-Authors: E C Madsen, G H Janssen, M Kramer, A G Lyne, G Hobbs, R N Manchester, I H Stairs, F Camilo, A PossentiAbstract:PSR J1740-3052 is a young pulsar in orbit around a companion that is most likely a B-type main-sequence star. Since its discovery more than a decade ago, data have been taken at several frequencies with instruments at the Green Bank, Parkes, Lovell and Westerbork telescopes. We Measure scattering time-scales in the pulse profiles and Dispersion Measure changes as a function of binary orbital phase and present evidence that both of these vary as would be expected due to a wind from the companion star. Using pulse arrival times that have been corrected for the observed periodic Dispersion Measure changes, we find a timing solution spanning from 1997 November to 2011 March. This includes Measurements of the advance of periastron, $\omega$??, and the change in the projected semimajor axis of the orbit, x??, and sets constraints on the orbital geometry. From these constraints, we estimate that the pulsar received a kick of at least ??50 km s-1 at birth. A quasi-periodic signal is present in the timing residuals with a period of 2.2 times the binary orbital period. The origin of this signal is unclear.
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timing the main sequence star binary pulsar j1740 3052
arXiv: High Energy Astrophysical Phenomena, 2012Co-Authors: E C Madsen, G H Janssen, M Kramer, A G Lyne, G Hobbs, R N Manchester, I H Stairs, F Camilo, A PossentiAbstract:PSR J1740-3052 is a young pulsar in orbit around a companion that is most likely a B-type main-sequence star. Since its discovery more than a decade ago, data have been taken at several frequencies with instruments at the Green Bank, Parkes, Lovell, and Westerbork telescopes. We Measure scattering timescales in the pulse profiles and Dispersion Measure changes as a function of binary orbital phase and present evidence that both of these vary as would be expected due to a wind from the companion star. Using pulse arrival times that have been corrected for the observed periodic Dispersion Measure changes, we find a timing solution spanning 1997 November to 2011 March. This includes Measurements of the advance of periastron and the change in the projected semimajor axis of the orbit and sets constraints on the orbital geometry. From these constraints, we estimate that the pulsar received a kick of at least ~50 km/s at birth. A quasi-periodic signal is present in the timing residuals with a period of 2.2 times the binary orbital period. The origin of this signal is unclear.
G Hobbs - One of the best experts on this subject based on the ideXlab platform.
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timing the main sequence star binary pulsar j1740 3052
Monthly Notices of the Royal Astronomical Society, 2012Co-Authors: E C Madsen, G H Janssen, M Kramer, A G Lyne, G Hobbs, R N Manchester, I H Stairs, F Camilo, A PossentiAbstract:PSR J1740-3052 is a young pulsar in orbit around a companion that is most likely a B-type main-sequence star. Since its discovery more than a decade ago, data have been taken at several frequencies with instruments at the Green Bank, Parkes, Lovell and Westerbork telescopes. We Measure scattering time-scales in the pulse profiles and Dispersion Measure changes as a function of binary orbital phase and present evidence that both of these vary as would be expected due to a wind from the companion star. Using pulse arrival times that have been corrected for the observed periodic Dispersion Measure changes, we find a timing solution spanning from 1997 November to 2011 March. This includes Measurements of the advance of periastron, $\omega$??, and the change in the projected semimajor axis of the orbit, x??, and sets constraints on the orbital geometry. From these constraints, we estimate that the pulsar received a kick of at least ??50 km s-1 at birth. A quasi-periodic signal is present in the timing residuals with a period of 2.2 times the binary orbital period. The origin of this signal is unclear.
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timing the main sequence star binary pulsar j1740 3052
arXiv: High Energy Astrophysical Phenomena, 2012Co-Authors: E C Madsen, G H Janssen, M Kramer, A G Lyne, G Hobbs, R N Manchester, I H Stairs, F Camilo, A PossentiAbstract:PSR J1740-3052 is a young pulsar in orbit around a companion that is most likely a B-type main-sequence star. Since its discovery more than a decade ago, data have been taken at several frequencies with instruments at the Green Bank, Parkes, Lovell, and Westerbork telescopes. We Measure scattering timescales in the pulse profiles and Dispersion Measure changes as a function of binary orbital phase and present evidence that both of these vary as would be expected due to a wind from the companion star. Using pulse arrival times that have been corrected for the observed periodic Dispersion Measure changes, we find a timing solution spanning 1997 November to 2011 March. This includes Measurements of the advance of periastron and the change in the projected semimajor axis of the orbit and sets constraints on the orbital geometry. From these constraints, we estimate that the pulsar received a kick of at least ~50 km/s at birth. A quasi-periodic signal is present in the timing residuals with a period of 2.2 times the binary orbital period. The origin of this signal is unclear.
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Dispersion Measure variations and their effect on precision pulsar timing
Monthly Notices of the Royal Astronomical Society, 2007Co-Authors: G Hobbs, M Bailes, W A Coles, R N Manchester, R T Edwards, J Sarkissian, J P W Verbiest, W Van StratenAbstract:We present an analysis of the variations seen in the Dispersion Measures (DMs) of 20-ms pulsars observed as part of the Parkes Pulsar Timing Array project.We carry out a statistically rigorous structure function analysis for each pulsar and show that the variations seen for most pulsars are consistent with those expected for an interstellar medium characterized by a Kolmogorov turbulence spectrum. The structure functions for PSRs J1045−4509 and J1909−3744 provide the first clear evidence for a large inner scale, possibly due to ion–neutral damping. We also show the effect of the solar wind on the DMs and show that the simple models presently implemented into pulsar timing packages cannot reliably correct for this effect. For the first time we clearly show how DM variations affect pulsar timing residuals and how they can be corrected in order to obtain the highest possible timing precision. Even with our presently limited data span, the residuals (and all parameters derived from the timing) for six of our pulsars have been significantly improved by correcting for the DM variations.
