Interstellar scattering toward Cygnus X-3: Measurements of anisotropy and of the inner scale

Molnar, Lawrence A.; Mutel, R. L.; Reid, M. J.; Johnston, K. J.

doi:10.1086/175115

Cited by 39 publications

(41 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is consistent with other measurements of elliptical scattering disks toward Cygnus (Spangler & Cordes 1988 ;Molnar et al 1995 ;Wilkinson et al 1994 ;Spangler & Cordes 1998). The narrow range of observed axial ratios between di †erent sources, di †erent frequencies, and di †erent epochs makes a refractive interpretation unlikely.…”

Section: General Remarkssupporting

confidence: 93%

“…While this value is reminiscent of Kolmogorov turbulence in neutral Ñuids, turbulence in an ionized medium is an active area of theoretical research and values for b ranging from 3.5 to 4.0 have been proposed (Kraichnan 1965 ;Goldreich & Sridhar 1995 ;Terry, Fernandez, & Ware 1998). The inner scale 1/q i is not known, but proposed values range from 300 to 106 kilometers (Coles et al 1987 ;Spangler & Gwinn 1990 ;Mutel & Lestrade 1990 ;Gupta, Rickett, & Coles 1993 ;Wilkinson et al 1994 ;Molnar et al 1995). The outer scale is also not known, but proposed values range from a 1/q o few AU to tens of pc (Anantharamaiah & Narayan 1988 ;Desai, Gwinn, & Diamond 1994 ;Wilkinson et al 1994).…”

Section: Turbulence and Interstellar Scatteringmentioning

confidence: 99%

“…Because both the direction and degree of anisotropy can vary along the line of sight, the ellipticity of a scattering disk seen by an interferometer can place only a lower limit to the actual degree of anisotropy in the turbulence. There are many lines of sight through the interstellar medium for which anisotropic turbulence has been proposed, primarily based upon measurement of very elliptical scattering disks (Spangler & Cordes 1988 ;Wilkinson et al 1994 ;Frail et al 1994 ;YusefZadeh et al 1994 ;Desai et al 1994 ;Molnar et al 1995 ;Rickett, Lyne, & Gupta 1997 ;Trotter et al 1998 ;Spangler & Cordes 1998). There are also many lines of sight where nominally elliptical scattering disks have been seen but not attributed to anisotropic turbulence (Spangler, Fey, & Cordes 1987 ;Gwinn et al 1988 ;Fey et al 1989 ;Zhao et al 1992 ;Fey & Mutel 1993).…”

Section: Turbulence and Interstellar Scatteringmentioning

confidence: 99%

See 2 more Smart Citations

Anisotropic Interstellar Scattering toward the Cygnus Region

Desai¹,

Fey²

2001

ASTROPHYS J SUPPL S

View full text Add to dashboard Cite

We were unable to reliably determine scattering disk parameters for 2021]317 at frequencies from 8.5 GHz down to 1.67 GHz because of its complex intrinsic source structure. The scattering disks are elliptical with axial ratios of about 0.75 : 1 with little measurable variation between these sources. We interpret our measurements as due to the e †ects of anisotropic interstellar turbulence. The anisotropy parameters, axial ratio and position angle, for those sources for which we have data at multiple frequencies appear to be frequency-independent making refractive distortions of isotropic turbulence an unlikely explanation. Our estimates of b, the power-law index of the power spectrum of electron density Ñuctuations, based upon direct model Ðts to the data on a source-by-source and frequency-by-frequency basis, are consistent with b \ 4 for most of the data but are strongly a †ected by our estimate of the intrinsic structure of the sources. Two of these sources, 2005]403 and 2021]317, exhibit signiÐcant intrinsic source structure at frequencies as low as 1.67 GHz, while the other two, 2008]332 and 2048]312, lack discernible source structure at frequencies lower then 2.3 GHz. The frequency scalings of the scattered angular sizes are also consistent with b \ 4. We discuss the implications of our measurements for the inner and outer scales of the turbulence.

show abstract

Section: General Remarkssupporting

confidence: 93%

Section: Turbulence and Interstellar Scatteringmentioning

confidence: 99%

Section: Turbulence and Interstellar Scatteringmentioning

confidence: 99%

See 1 more Smart Citation

Anisotropic Interstellar Scattering toward the Cygnus Region

Desai¹,

Fey²

2001

ASTROPHYS J SUPPL S

View full text Add to dashboard Cite

show abstract

“…Measured axial ratios are in the range 1.3-3.0 (Wilkinson et al 1994;Molnar et al 1995;Desai & Fey 2001;Frail et al 1994;Yusef-Zadeh et al 1994;Desai et al 1994). An axial ratio of at least 4 : 1 was inferred from scintillation analysis of the quasar B0405À385 by Rickett at al.…”

Section: Anisotropy Analysis For J0737à3039mentioning

confidence: 98%

Probing the Eclipse of J0737−3039A with Scintillation

Coles

McLaughlin

Rickett

et al. 2005

ApJ

View full text Add to dashboard Cite

We have examined the interstellar scintillations of the pulsars in the double-pulsar binary system. Near the time of the eclipse of pulsar A by the magnetosphere of B, the scintillations from both pulsars should be highly correlated because the radiation is passing through the same interstellar plasma. We report confirmation of this effect using 820 and 1400 MHz observations made with the Green Bank Telescope. The correlation allows us to constrain the projected relative position of the two pulsars at closest approach to be 4000 AE 2000 km, corresponding to an inclination that is only 0N29 AE 0N14 away from 90 . It also produces a two-dimensional map of the spatial correlation of the interstellar scintillation. This shows that the interstellar medium in the direction of the pulsars is significantly anisotropic. When this anisotropy is included in the orbital fitting, the transverse velocity of the center of mass is reduced from the previously published value of 141 AE 8:5 km s À1 to 66 AE 15 km s À1 .

show abstract

“…While large, a scattering angle of this magnitude is not unprecedented. Various low Galactic latitude sources have scattering diameters comparable to or larger than this value (e.g., NGC 6334B, Moran et al 1990; Cyg X-3, Molnar et al 1995). As the META candidates have low Galactic latitudes as well, we can place no constraints on .…”

Section: Interstellar Scintillationmentioning

confidence: 97%

Megachannel Extraterrestrial Assay Candidates: No Transmissions from Intrinsically Steady Sources

Lazio

Tarter

Backus

2002

The Astronomical Journal

View full text Add to dashboard Cite

We report new, more sensitive observations of nine of the 11 extrastatistical signals in the Megachannel Extraterrestrial Assay (META). These extrastatistical signals had all the expected characteristics of a transmission from an extraterrestrial transmitter, except that they did not repeat. Cordes, Lazio, & Sagan showed that this lack of repeatability could be explained by the high detection thresholds used in the reobservations of these candidates, combined with interstellar scintillation of intrinsically steady sources. We use the Cordes et al. methodology, correcting an error in the original presentation, and our new observations to rule out this scintillation hypothesis at a confidence level of at least 97.8% (for the case of an intrinsically weak source) and to a level in excess of 99% (if the source strengths are comparable to the value favored by Cordes et al.). We also demonstrate that gravitational microlensing cannot account for the initial detection of these candidate signals, nor is gravitational lensing likely to play a role in future SETI programs. We conclude that the META candidates do not reflect a large population of powerful, strong beacons.

show abstract

Interstellar scattering toward Cygnus X-3: Measurements of anisotropy and of the inner scale

Cited by 39 publications

References 0 publications

Anisotropic Interstellar Scattering toward the Cygnus Region

Anisotropic Interstellar Scattering toward the Cygnus Region

Probing the Eclipse of J0737−3039A with Scintillation

Megachannel Extraterrestrial Assay Candidates: No Transmissions from Intrinsically Steady Sources

Contact Info

Product

Resources

About