Nonspherical Structures and Temporal Variations in the Dust Shell of o Ceti Observed with a Long Baseline Interferometer at 11 microns

López, B.; Danchi, W. C.; Bester, M.; Hale, David; Lipman, Everett A.; Monnier, John D.; Tuthill, P. G.; Townes, C. H.; Degiacomi, C. G.; Geballe, T. R.; Greenhill, L. J.; Cruzalèbes, P.; Lefèvre, J.; Mékarnia, D.; Mattei, J. A.; Nishimoto, D.; Kervin, P.

doi:10.1086/304719

Cited by 77 publications

(80 citation statements)

References 31 publications

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“…When nonspherical dust halos occur, it is rarely possible to discriminate between a number of viable outÑow models when only relatively limited Fourier data are available, even though reasonable models may be chosen (e.g., Lopez et al 1997). The simple isotropic outÑow model given here provides a reasonable Ðt to most of our mid-IR visibility data.…”

Section: Mid-infrared V Isibility Measurementsmentioning

confidence: 99%

Near‐ and Mid‐Infrared Subarcsecond Structure of the Dusty Symbiotic Star R Aquarii

Tuthill

Danchi

Hale

et al. 2000

ApJ

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The results of a high-resolution interferometric campaign targeting the symbiotic long-period variable (LPV) R Aqr are reported. With both near-infrared measurements on baselines out to 10 m and midinfrared data extending to 32 m, we have been able to measure the characteristic sizes of regions from the photosphere of the LPV and its extended molecular atmosphere out to the cooler circumstellar dust shell. The near-infrared data were taken using aperture-masking interferometry on the Keck I telescope and show R Aqr to be partially resolved for wavelengths out to 2.2 km but with a marked enlargement, possibly due to molecular opacity, at 3.1 km. Mid-infrared interferometric measurements were obtained with the Univeristy of California, Berkeley, infrared spatial interferometer (ISI) operating at 11.15 km from 1992 to 1999. Although this data set is somewhat heterogeneous with incomplete coverage of the Fourier plane and sampling of the pulsation cycle, clear changes in the mid-infrared brightness distribution were observed, both as a function of position angle on the sky and as a function of pulsation phase. Spherically symmetric radiative transfer calculations of uniform-outÑow dust shell models produce brightness distributions and spectra which partially explain the data ; however, limitations to this approximation are noted. Evidence for signiÐcant deviation from circular symmetry was found in the mid-infrared and more tentatively at 3.08 km in the near-infrared ; however, no clear detection of binarity or of non-LPV elements in the symbiotic system is reported.

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Section: Mid-infrared V Isibility Measurementsmentioning

confidence: 99%

Near‐ and Mid‐Infrared Subarcsecond Structure of the Dusty Symbiotic Star R Aquarii

Tuthill

Danchi

Hale

et al. 2000

ApJ

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“…Similarly, Lopez et al (1997) performed visibility observations at 11 µm towards o Ceti during a ∼7-year period, in the Mira-AB axis direction, which stress the non-spherical and evolving clumpy structure of the dust shell around o Ceti. They even suggested that the formation of a new clump of dust could be linked to the OH flaring events observed in the 1990s by increasing temporarily the far-infrared emission which is known to operate as a common pump of the OH ground-state main lines (i.e., 1665 & 1667 MHz).…”

Section: Role Of Binarity In the Flaring Events Towardsmentioning

confidence: 92%

Recurring OH Flares towards o Ceti: I. location and structure of the 1990s’ and 2010s’ events

Etoka

Gérard

Richards

et al. 2017

Monthly Notices of the Royal Astronomical Society

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We present the analysis of the onset of the new 2010s' OH flaring event detected in the OH ground-state main line at 1665 MHz towards o Ceti and compare its characteristics with those of the 1990s' flaring event. This is based on a series of complementary single-dish and interferometric observations both in OH and H 2 O obtained with the Nançay Radio telescope (NRT), the Medicina and Effelsberg Telescopes, the European VLBI Network (EVN), and (e)Multi-Element Radio Linked Interferometer Network ((e)MERLIN). We compare the overall characteristics of o Ceti's flaring events with those which have been observed towards other thin-shell Miras, and explore the implication of these events with respect to the standard OH circumstellar-envelope model. The role of binarity in the specific characteristics of o Ceti's flaring events is also investigated. The flaring regions are found to be less than ∼400±40 mas (i.e., ≤ 40 ± 4 AU) either side of o Ceti, with seemingly no preferential location with respect to the direction to the companion Mira B. Contrary to the usual expectation that the OH maser zone is located outside the H 2 O maser zone, the coincidence of the H 2 O and OH maser velocities suggests that both emissions arise at similar distances from the star. The OH flaring characteristics of Mira are similar to those observed in various Mira variables before, supporting the earlier results that the regions where the transient OH maser emission occurs are different from the standard OH maser zone.

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“…From the data obtained with this instrument at 11.15 µm, Danchi et al (1994) showed that the radius of dust formation depends on the spectral type of the stars. Lopez et al (1997) have found a strong dependence on the pulsation phase. Observations have been made of NML Cyg, α Sco, as well as of changes in the dust shell around Mira and IK Tau, (Hale et al 1997, Lopez et al 1997, mid-IR molecular absorption features of ammonia and silane of IRC+10216 and VY CMA .…”

Section: Fig 21mentioning

confidence: 96%

Modern optical astronomy: technology and impact of interferometry

Saha

2002

Rev. Mod. Phys.

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The present 'state of the art' and the path to future progress in high spatial resolution imaging interferometry is reviewed. The review begins with a treatment of the fundamentals of stellar optical interferometry, the origin, properties, optical effects of turbulence in the Earth's atmosphere, the passive methods that are applied on a single telescope to overcome atmospheric image degradation such as speckle interferometry, and various other techniques. These topics include differential speckle interferometry, speckle spectroscopy and polarimetry, phase diversity, wavefront shearing interferometry, phase-closure methods, dark speckle imaging, as well as the limitations imposed by the detectors on the performance of speckle imaging. A brief account is given of the technological innovation of adaptive-optics (AO) to compensate such atmospheric effects on the image in real time. A major advancement involves the transition from single-aperture to the dilute-aperture interferometry using multiple telescopes. Therefore, the review deals with recent developments involving ground-based, and space-based optical arrays. Emphasis is placed on the problems specific to delay-lines, beam recombination, polarization, dispersion, fringe-tracking, bootstrapping, coherencing and cophasing, and recovery of the visibility functions. The role of AO in enhancing visibilities is also discussed. The applications of interferometry, such as imaging, astrometry, and nulling are described. The mathematical intricacies of the various 'post-detection' image-processing techniques are examined critically. The review concludes with a discussion of the astrophysical importance and the perspectives of interferometry.

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Nonspherical Structures and Temporal Variations in the Dust Shell of o Ceti Observed with a Long Baseline Interferometer at 11 microns

Cited by 77 publications

References 31 publications

Near‐ and Mid‐Infrared Subarcsecond Structure of the Dusty Symbiotic Star R Aquarii

Near‐ and Mid‐Infrared Subarcsecond Structure of the Dusty Symbiotic Star R Aquarii

Recurring OH Flares towards o Ceti: I. location and structure of the 1990s’ and 2010s’ events

Modern optical astronomy: technology and impact of interferometry

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