Speckle interferometry in the near-infrared

Selby, Mark; Wade, Richard A.; Magro, C. Sánchez

doi:10.1093/mnras/187.3.553

Cited by 21 publications

(8 citation statements)

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“…IRC +10216 is bright and extended in the infrared (Toombs et al 1972;Sutton et al 1979;Selby, Wade, and Sanchez Magro 1979;McCarthy, Howell, and Low 1980;Mariotti et al 1983;Dyck et al 1984) and is an ideal candidate for studies of the spatial brightness distribu-tion. The investigation by Zuckerman et al (1986) indicated that, although its observable properties appear extreme, it may be a star of quite ordinary AGB luminosity (about 10 4 Lo) and modest mass (a few 3J£ 0 ).…”

Section: Introductionmentioning

confidence: 99%

Measurements of the circumstellar shell geometry in IRC + 10216

Dyck¹,

Zuckerman²,

Howell³

et al. 1987

PASP

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Using speckle interferometric techniques, we have measured the spatial distribution of light in two infrared colors around the carbon star IRC +10216. At 2.2 fxm the visibility data indicate that the brightness distribution is elongated at approximately P.A. = 20°, which is similar to the orientation seen in early photographs at shorter wavelengths. At 10.3 jxm the distribution is more nearly circular. A possible slight elongation occurs in the visibility data at approximately P.A. = 90°.We have also measured phases in the image using the Knox-Thompson algorithm. The 10.3 jxm one-dimensional images reconstructed from these phases and the visibilities show that the source is extended at all orientations. No reflection asymmetry is apparent with respect to the center. There is less clear evidence in these reconstructed images than in the visibility data for any departure from circular symmetry at 10.3 fxm. The 2.2 jxm one-dimensional images, however, do exhibit the same departure from circular symmetry shown by the visibility data. The reconstructed images show that there is a general enhancement in the brightness distribution concentrated toward the north-northeast with the star offset to the south-southwest in the envelope.We discuss our speckle interferometry in light of an old suggestion by Serkowski that IRC +10216 is surrounded by a bipolar nebula.

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Section: Introductionmentioning

confidence: 99%

Measurements of the circumstellar shell geometry in IRC + 10216

Dyck¹,

Zuckerman²,

Howell³

et al. 1987

PASP

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“…Extensive theoretical work about seeing has been published that is not much concerned with the practical problems of this paper, but work on the wavelength dependence of seeing by Fried (1966), Boyd (1978) and Selby et al (1979) is relevant, and is capable of experimental checking, given by Boyd and Selby et al It appears that dilation of an image owing to seeing varies as λ −1/5 , the seeing errors being less at longer wavelengths. This is a very low rate of change compared with the linear variation of DLAR (the seeing decreases by about 15 per cent for a doubling of λ), but it becomes significant for large changes of λ.…”

Section: The Seeingmentioning

confidence: 99%

Optical imaging in very large telescopes

Wynne

1999

Monthly Notices of the Royal Astronomical Society

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“…For different sites, telescopes, and methods, correlation times increase from perhaps 5 ms in the visual (Dainty et al 1990) to ^ 100 ms in the far-infrared (Selby et al 1979;Mariotti 1983).…”

Section: Differences In Time Scalementioning

confidence: 99%

Atmospheric Intensity Scintillation of Stars. II. Dependence on Optical Wavelength

Dravins¹,

Lindegren²,

Mezey³

et al. 1997

PASP

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ABSTRACT. Atmospheric intensity scintillation of stars on milli-and microsecond time scales was extensively measured at the astronomical observatory on La Palma (Canary Islands). Scintillation statistics and temporal changes were discussed in Paper I, while this paper shows how scintillation depends on optical wavelength. Such effects originate from the changing refractive index of air, and from wavelength-dependent diffraction in atmospheric inhomogeneities. The intensity variance aj increases for shorter wavelengths, at small zenith distances approximately consistent with a theoretical X -7/6 slope, but with a tendency for a somewhat weaker dependence. Scintillation in the blue is more rapid than in the red. The increase with wavelength of autocorrelation time scales (roughly proportional to >/\) is most pronounced in very small apertures, but was measured up to 0 20 cm. Scintillation at different wavelengths is not simultaneous: atmospheric chromatic dispersion stretches the atmospherically induced "flying shadows" into "flying spectra" on the ground. As the "shadows" fly past the telescope aperture, a time delay appears between fluctuations at different wavelengths whenever the turbulence-carrying winds have components parallel to the direction of dispersion. These effects increase with zenith distance (reaching -100 ms cross-correlation delay between blue and red at Z = 60° ), and also with increased wavelength difference. This time delay between scintillation in different colors is a property of the atmospheric flying shadows, and thus a property that remains unchanged even in very large telescopes. However, the wavelength dependence of scintillation amplitude and time scale is "fully" developed only in small telescope apertures ( ^ 5 cm), the scales where the "flying shadows" on the Earth's surface become resolved. Although these dependences rapidly vanish after averaging in larger apertures, an understanding of chromatic effects may still be needed for the most accurate photometric measurements. These will probably require a sampling of the (stellar) signal with full spatial, temporal, and chromatic resolution to segregate the scintillation signatures from those of astrophysical variability.

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Speckle interferometry in the near-infrared

Cited by 21 publications

References 0 publications

Measurements of the circumstellar shell geometry in IRC + 10216

Measurements of the circumstellar shell geometry in IRC + 10216

Optical imaging in very large telescopes

Atmospheric Intensity Scintillation of Stars. II. Dependence on Optical Wavelength

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