Deflection of Pulsar Signal Reveals Compact Structures in the Galaxy

Hill, Alex S.; Stinebring, Daniel R.; Asplund, Curtis T.; Berwick, Daniel E.; Everett, W.; Hinkel, Natalie R.

doi:10.1086/428347

Cited by 91 publications

(116 citation statements)

References 20 publications

(45 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, the clumps are small enough that they produce effectively no additional broadening. This scenario is also broadly consistent with the notion of clumps of material producing extreme scattering events (Fiedler et al 1987) and parabolic arcs in pulsar dynamic spectra ( Hill et al 2005).…”

Section: Discussionsupporting

confidence: 87%

Angular Broadening of Intraday Variable AGNs. II. Interstellar and Intergalactic Scattering

Lazio

Ojha

Fey

et al. 2008

ApJ

View full text Add to dashboard Cite

We analyze a sample of 58 multiwavelength, Very Long Baseline Array observations of active galactic nuclei (AGNs) to determine their scattering properties. Approximately 75% of the sample consists of AGNs that exhibit centimeter-wavelength intraday variability (interstellar scintillation), while the other 25% do not show intraday variability. We find that interstellar scattering is measurable for most of these AGNs, and the typical broadening diameter is 2 mas at 1 GHz. We find that the scintillating AGNs are typically at lower Galactic latitudes than the nonscintillating AGNs, consistent with the scenario that intraday variability is a propagation effect from the Galactic interstellar medium. The magnitude of the inferred interstellar broadening measured toward the scintillating AGNs, when scaled to higher frequencies, is comparable to the diameters inferred from analyses of the light curves for the more well-known intraday variable sources. However, we find no difference in the amount of scattering measured toward the scintillating versus nonscintillating AGNs. A consistent picture is one in which the scintillation results from localized regions (''clumps'') distributed throughout the Galactic disk, but that individually make little contribution to the angular broadening. Of the 58 AGNs observed, 37 (64%) have measured redshifts. At best, a marginal trend is found for scintillating (nonscintillating) AGNs to have smaller (larger) angular diameters at higher redshifts. We also use our observations to try to constrain the possibility of intergalactic scattering. While broadly consistent with the scenario of a highly turbulent intergalactic medium, our observations do not place significant constraints on its properties.

show abstract

Section: Discussionsupporting

confidence: 87%

Angular Broadening of Intraday Variable AGNs. II. Interstellar and Intergalactic Scattering

Lazio

Ojha

Fey

et al. 2008

ApJ

View full text Add to dashboard Cite

show abstract

“…First recognized by Stinebring et al (2001) in Arecibo data, detailed studies of these arcs have revealed a variety and richness in their observational manifestations; e.g., forward and reverse arcs, and a chain of arclets (Hill et al 2005;Putney & Stinebring 2006;Brisken et al 2010), which also stimulated a great deal of theoretical and modeling work (Walker et al 2004;Cordes et al 2006;Brisken et al 2010). In the context of PTAs Hemberger & Stinebring (2008) measured scattering delays from their observations of scintillation arcs in PSR B1737+13 (DM=48.9 pc cm 3 -); the delays varied from ∼0.2 to 2 μs at a frequency of 1.3 GHz.…”

Section: Introductionmentioning

confidence: 99%

Scintillation Arcs in Low-Frequency Observations of the Timing-Array Millisecond Pulsar PSR J0437–4715

Bhat

Ord

Tremblay

et al. 2016

ApJ

View full text Add to dashboard Cite

Low-frequency observations of pulsars provide a powerful means for probing the microstructure in the turbulent interstellar medium (ISM). Here we report on high-resolution dynamic spectral analysis of our observations of the timing-array millisecond pulsar PSR J0437-4715 with the Murchison Widefield Array (MWA), enabled by our recently commissioned tied-array beam processing pipeline for voltage data recorded from the high time resolution mode of the MWA. A secondary spectral analysis reveals faint parabolic arcs akin to those seen in high-frequency observations of pulsars with the Green Bank and Arecibo telescopes. Data from Parkes observations at a higher frequency of 732 MHz reveal a similar parabolic feature with a curvature that scales approximately as the square of the observing wavelength (λ 2 ) to the MWAʼs frequency of 192 MHz. Our analysis suggests that scattering toward PSR J0437-4715 predominantly arises from a compact region about 115 pc from the Earth, which matches well with the expected location of the edge of the Local Bubble that envelopes the local Solar neighborhood. As well as demonstrating new and improved pulsar science capabilities of the MWA, our analysis underscores the potential of low-frequency pulsar observations for gaining valuable insights into the local ISM and for characterizing the ISM toward timing-array pulsars.

show abstract

“…A representative secondary spectrum is shown in the top panel of Figure 1. The power in the secondary spectrum is distributed along a parabolic scintillation arc (Stinebring et al 2001;Hill et al 2003Hill et al , 2005Walker et al 2004;Cordes et al 2006). This is the transform domain representation of the crisscross pattern often seen in dynamic spectra, and it arises from interference between central and peripheral rays of the scattered image (Stinebring et al 2001;Cordes et al 2006).…”

Section: Observationsmentioning

confidence: 99%

Time Variability of Interstellar Scattering and Improvements to Pulsar Timing

Hemberger

Stinebring

2008

ApJ

Self Cite

View full text Add to dashboard Cite

Delay due to multipath scattering in the interstellar medium is a concern for high-precision pulsar timing, particularly if it is not constant over time. We report on 36 weekly observations of the pulsar PSR B1737ϩ13 with the Arecibo telescope that monitored the time variability of the scattering delay. At a frequency of 1380 MHz, the interstellar delay varied between 0.2 and 2.1 ‫1.0ע(‬ ) over 270 days of observation. The delay ms ms was consistent over four observing bands with center frequencies from 1175 to 1470 MHz and scaled as t ∝ , which differs from the scaling expected for Kolmogorov turbulence. We show that another estimation Ϫ3.6‫2.0ע‬ Ϫ4.4 n n technique is feasible for weaker pulsars or smaller telescopes, although it underestimates the delay during episodes of extra scattering detectable through a full secondary spectrum analysis. An array of pulsars distributed around the sky can be used as a sensitive detector of long-wavelength (∼ several light-years) gravitational radiation, and such pulsar timing array observations have been initiated by several groups worldwide. To reach interesting sensitivity levels it is necessary to reduce the sources of error to below 1 , and 100 ns is a target precision ms level. Correction for interstellar scattering delay will be an important step in achieving long-term, submicrosecond timing precision.

show abstract

Deflection of Pulsar Signal Reveals Compact Structures in the Galaxy

Cited by 91 publications

References 20 publications

Angular Broadening of Intraday Variable AGNs. II. Interstellar and Intergalactic Scattering

Angular Broadening of Intraday Variable AGNs. II. Interstellar and Intergalactic Scattering

Scintillation Arcs in Low-Frequency Observations of the Timing-Array Millisecond Pulsar PSR J0437–4715

Time Variability of Interstellar Scattering and Improvements to Pulsar Timing

Contact Info

Product

Resources

About