A Second Chromatic Timing Event of Interstellar Origin toward PSR J1713+0747

Lam, Michael T.; Ellis, Justin; Grillo, Gianfranco; Jones, Megan L.; Hazboun, Jeffrey S.; Brook, Paul R.; Turner, Jacob E.; Chatterjee, Shami; Cordes, J. M.; Lazio, T. Joseph W.; DeCesar, Megan E.; Arzoumanian, Zaven; Blumer, Harsha; Cromartie, H. T.; Demorest, Paul; Dolch, Timothy; Ferdman, R. D.; Ferrara, E. C.; Fonseca, Emmanuel; Garver-Daniels, Nathan; Gentile, Peter A.; Gupta, Vivek; Lorimer, D. R.; Lynch, R.; Madison, D. R.; McLaughlin, M. A.; Ng, Cherry; Nice, D. J.; Pennucci, T. T.; Ransom, S. M.; Spiewak, R.; Stairs, I. H.; Stinebring, D. R.; Stovall, K.; Swiggum, Joseph K.; Vigeland, Sarah J.; Zhu, Weiwei

doi:10.3847/1538-4357/aac770

Cited by 68 publications

(61 citation statements)

References 47 publications

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“…As has been described in the literature, there are multiple frequency-dependent delays that affect pulsar TOAs (Foster & Cordes 1990;Lam et al 2016bLam et al , 2018bShannon & Cordes 2017). Beyond the traditional dispersive delay due to the integrated electron density (∝ ν −2 ), there is a geometric delay (∝ ν −4 ) due to total path length changes and a barycentriccorrection delay (∝ ν −2 ) due to the angle of arrival of the pulsar shifting, i.e., the pulsar's image appearing from a different direction on the sky.…”

Section: Impact Of Non-dispersive Delaysmentioning

confidence: 89%

“…Refraction by discrete structures along the propagation path can also result in variations in DM timeseries via mis-estimation from non-dispersive delays (Foster & Cordes 1990;Cordes et al 2017). These delays can therefore be useful in characterizing such discrete structures (e.g., Lam et al 2018b). However, care needs to be taken in order to properly account for all effects in timing data.…”

Section: Testing the Ese Interpretationmentioning

confidence: 99%

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On Frequency-dependent Dispersion Measures and Extreme Scattering Events

Lam

Lazio

Dolch

et al. 2020

ApJ

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Context. Variations in pulsar dispersion measures have been observed since shortly after the discovery of pulsars. As early as 2006, frequency-dependent dispersion measures have been observed and attributed to several possible causes. Cordes et al. (2016) demonstrated that ray-path averaging over different effective light-cone volumes through the turbulent ionized interstellar medium must contribute to this effect. Aims. We present methods to assess the variations in frequency-dependent dispersion measures due to the turbulent interstellar medium versus compact lensing structures along the path of radio propagation. We describe an application of this method to observations presented in Donner et al. (2019) in the direction of PSR J2219+4754 to determine if the data are consistent with proposed extreme scattering events. Methods. We examine the observations of Donner et al. (2019) in the context of the recent literature on interstellar medium propagation effects and other observations. We analyze the data based on the framework of Cordes et al. (2016) regarding frequency-dependent dispersion measures to demonstrate consistency of the observations with a purely turbulent medium and investigate the magnitude of this effect due to the line of sight crossing the solar wind. We discuss the implications of multiple frequency-dependent delays based on work in the field of high-precision pulsar timing and consider the error budget on the timing of this canonical pulsar. We build upon previous work on the structure functions of dispersion measure timeseries and show that higher-order structure functions are more robust to estimates of the magnitude of the frequency-dependence of dispersion measure and can provide information about the line-of-sight medium.Results. We find that the frequency dependence of the dispersion measure timeseries for PSR J2219+4754 is consistent with being due solely to turbulence in the ionized interstellar medium and that there is no evidence for an extreme scattering event or small-scale lensing structure in the interstellar medium.

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Section: Impact Of Non-dispersive Delaysmentioning

confidence: 89%

Section: Testing the Ese Interpretationmentioning

confidence: 99%

On Frequency-dependent Dispersion Measures and Extreme Scattering Events

Lam

Lazio

Dolch

et al. 2020

ApJ

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“…These short pulses of high energy radio waves may be the result of magnification from plasma lensing due to compact structures in the dense environment of the FRBs host galaxy. Due to the time delay effects of refraction on pulsars, plasma lensing is also relevant to pulsar timing networks such as NANOGrav (Lam 2018;Gentile et al 2018).…”

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confidence: 99%

Dual-component plasma lens models

Rogers

2019

Monthly Notices of the Royal Astronomical Society

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In contrast to the converging, achromatic behaviour of axisymmetric gravitational lenses, diverging frequency-dependent lensing occurs from refraction due to a distribution of over-dense axisymmetric plasma along an observer's line of sight. Such plasma lenses are particularly interesting from the point of view of astronomical observations because they can both magnify and dim the appearance of background sources as a function of frequency. Plasma lensing is believed to be involved in a number of separate phenomena involving the scintillation of radio pulsars, extreme scattering events of background radio sources and may also play a role in the generation of fast radio bursts. These lensing phenomena are believed to occur in dense environments, in which there may be many density perturbations between an observer and background source. In this work we generalize individual plasma lens models to produce dual component lenses using families of plasma lens models previously studied in the literature, namely the exponential and softened power-law lenses. Similar to binary gravitational lens models, these dual component plasma lenses feature a rich and complex critical and caustic morphology, as well as generate more complicated light curves. We map the number of criticals formed for a given component separation and angular size, and highlight a relevant degeneracy between two particular models. This work provides an argument in favor of close monitoring of extreme scattering events in progress in order to break such model degeneracies.

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“…Both θ r and t geo,min are given in Table 3. Measurement of these geometric delays is critical; since the refraction delay is ∝ ν −4 , removal of the dispersive ν −2 delay will bias the "infinite-frequency" arrival times used in precision timing experiments (Lam et al 2016b(Lam et al , 2018b. We found t geo,min was roughly consistent with zero for all pulsars after propagation of all uncertainties except for PSR J1614−2230.…”

Section: Scintle Drift Ratesmentioning

confidence: 62%

Analysis of Multi-hour Continuous Observations of Seven Millisecond Pulsars

Shapiro-Albert

McLaughlin

Lam

et al. 2020

ApJ

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Precision pulsar timing can be used for a variety of astrophysical tests from the detection of gravitational waves to probing the properties of the interstellar medium (ISM). Here we present analyses of the noise contributions to pulsar timing residuals from continuous multi-hour observations of seven millisecond pulsars (MSPs). We present scintillation bandwidth measurements for all MSPs in the sample, some for the first time, and scintillation timescale measurements and lower limits for all MSPs for the first time. In addition, we present upper limits on the contribution of pulse phase jitter to the timing residual error for all MSPs. These long observations also allow us to constrain variations in dispersion measures (DMs) on hour-long timescales for several millisecond pulsars. We find that there are no apparent DM variations in any of the MSPs studied on these timescales as expected. In light of new radio telescopes such as the Canadian Hydrogen Intensity Mapping Experiment (CHIME), which will be able to time many pulsars for a short time each day, we search for differences in timing precisions from continuous TOAs and from equivalent length time-discontinuous TOAs. We find no differences in the precision for any MSP in our sample, as expected. We conclude that the TOA variations are consistent with the expected breakdown into template-fitting, jitter, and scintillation errors.

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A Second Chromatic Timing Event of Interstellar Origin toward PSR J1713+0747

Cited by 68 publications

References 47 publications

On Frequency-dependent Dispersion Measures and Extreme Scattering Events

On Frequency-dependent Dispersion Measures and Extreme Scattering Events

Dual-component plasma lens models

Analysis of Multi-hour Continuous Observations of Seven Millisecond Pulsars

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