A radio continuum study of the ‘Engraved Hourglass’ nebula, MyCn 18

Bains, Indra; Bryce, M.; Calabretta, M. R.; Stirling, A. M.

doi:10.1046/j.1365-8711.2002.05796.x

Cited by 3 publications

(6 citation statements)

References 21 publications

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“…They also A&A 569, A50 (2014) inferred that the etched arcs on the hourglass walls might indicate temporal variations in the mass-loss rate of the progenitor star. Bains et al (2002) found a similar geometric offset between the nebula and the central star when observing at radio wavelengths. Their spectral index maps show that the nebular core appears to be more optically thick than the lobe regions at lower frequencies (1384 and 4800 MHz).…”

Section: Introductionsupporting

confidence: 54%

“…The infrared spectroscopy shows clear ionisation stratification in that the He, H, and H 2 lines are found progressively further from the central star into the putative surrounding molecular torus. The nebula is likely to be ionisation bounded in the equatorial direction but since the high-speed knots are ionised the nebula is more likely to be density bounded in the polar direction (Dayal et al 2000;Bains et al 2002). Figure 7 shows the energy diagram of H 2 lines in the outflow.…”

Section: Spectroscopic Analysismentioning

confidence: 99%

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VLT observations of the asymmetric Etched Hourglass Nebula, MyCn 18

Clyne

Redman

Lloyd

et al. 2014

A&A

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Context. The mechanisms that form extreme bipolar planetary nebulae remain unclear. Aims. The physical properties, structure, and dynamics of the bipolar planetary nebula, MyCn 18, are investigated in detail with the aim of understanding the shaping mechanism and evolutionary history of this object. Methods. VLT infrared images, VLT ISAAC infrared spectra, and long-slit optical Echelle spectra are used to investigate MyCn 18. Morpho-kinematic modelling was used to firmly constrain the structure and kinematics of the source. A timescale analysis was used to determine the kinematical age of the nebula and its main components. Results. A spectroscopic study of MyCn 18's central and offset region reveals the detailed make-up of its nebular composition. Molecular hydrogen, atomic helium, and Bracket gamma emission are detected from the central regions of MyCn 18. ISAAC spectra from a slit position along the narrow waist of the nebula demonstrate that the ionised gas resides closer to the centre of the nebula than the molecular emission. A final reconstructed 3D model of MyCn 18 was generated, which provides kinematical information on the expansion velocity of its nebular components by means of position-velocity (P-V) arrays. A kinematical age of the nebula and its components were obtained by the P-V arrays and timescale analysis. Conclusions. The structure and kinematics of MyCn 18 are better understood using an interactive 3D modelling tool called SHAPE. A dimensional and timescale analysis of MyCn 18's major components provides a possible mechanism for the nebula's asymmetry. The putative central star is somewhat offset from the geometric centre of the nebula, which is thought to be the result of a binary system. We speculate that the engulfing and destruction of an exoplanet during the asymptotic giant branch phase may have been a key event in shaping MyCn 18 and generating of its hypersonic knotty outflow.

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Section: Introductionsupporting

confidence: 54%

Section: Spectroscopic Analysismentioning

confidence: 99%

VLT observations of the asymmetric Etched Hourglass Nebula, MyCn 18

Clyne

Redman

Lloyd

et al. 2014

A&A

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“…They are all candidates for symbiotic systems and have high‐velocity outflows. Their similarity at radio wavelengths is revealed in high‐resolution observations where they are all found to exhibit bright emission from compact core structures (Kwok et al 1985; Bains et al 2002).…”

Section: Discussionmentioning

confidence: 88%

“…Kwok et al 1985; Livio & Soker 2001) and MyCn 18 (e.g. Bryce et al 1997b; Sahai et al 1999; Bains et al 2002). All three of these objects belong to the class of extreme bipolar nebulae with narrow waists and dense collimating tori; they have been termed ‘butterflies’ by Balick & Frank (2002) and Kwok (2002).…”

Section: Discussionmentioning

confidence: 99%

The radio structure of Menzel 3

Bains

Redman

Bryce

et al. 2004

Monthly Notices of the Royal Astronomical Society

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We present the first radio continuum images of the evolved late-type stellar object, Menzel 3 (Mz 3), made with multifrequency observations using the Australia Telescope Compact Array. The maximum resolutions attained are 1, 2, 4 and 7 arcsec. At each frequency investigated, the large-scale radio structure is reminiscent of that seen at infrared and optical wavelengths. In the highest-frequency image of resolution 1 arcsec, the radio brightness distribution is dominated by a compact core emission feature, which we attribute to the ionization of either the last exhalation of the superwind (single progenitor scenario) or to the ongoing stellar wind from a companion (binary scenario). At the higher frequencies investigated, we find that this core ionized outflow is asymmetric, optically thick and has a spectral index consistent with that of thermal emission. The mass loss rate associated with the core emission feature is 7 × 10 −5 M yr −1 . We discuss this outflow and favour its origin as being due to a companion. Extending from either side of the compact core, at PA ∼ 120 • with respect to the bipolar axis, we find evidence for wings of emission that may be due to the ionized inner surface of an equatorial collimating disc; this surface has dimensions 7 × 1.5 arcsec 2 (8800 × 1900 au 2 at 1.3 kpc). We suggest that this feature may be part of the circumbinary accretion disc suggested recently by Kastner et al. We measure low brightness temperatures, which we attribute to there being unresolved condensations on sub-arcsecond scales within the beam size.

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“…18). Such a breach is not uncommon; MyCn 18 (Bryce et al 1997a; Bains et al 2002) shows open‐ended structure in its lobes. A breach in the near side of the shell would mean that what we observe is the inner, hotter region of the redshifted portion of the shell along the line of sight.…”

Section: Discussionmentioning

confidence: 99%

High-resolution radio structure and optical kinematics of NGC 7027

Bains¹,

Bryce²,

Mellema³

et al. 2003

Monthly Notices of the Royal Astronomical Society

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We present the results of the highest‐resolution 18‐cm (L‐band) radio continuum and optical kinematic studies to date of the young planetary nebula (PN), NGC 7027. We discuss the radio image of NGC 7027 made from combined data from the Multi‐Element Radio‐Linked Interferometer Network and the Very Large Array. This image is used to derive the distribution of the nebular brightness temperature at this frequency. By combining the 18‐cm image with the 6‐cm (C‐band) image of Bryce et al., two‐dimensional distributions of the spectral index between L‐ and C‐bands, C‐band optical depth and emission measure are constructed and analysed. In the optical regime, high dispersion, spatially resolved observations at high spectral resolution have been obtained of this PN. The resulting velocity ellipses confirm the inclination of the north of the PN towards the line of sight. A waist feature is seen in the equatorial plane and [S ii]6716/6731 Å ratios indicate that a density enhancement exists in this region. The PN equatorial expansion velocity is deprojected and measured as 13 ± 1 km s−1 from the [O iii]4959 Å emission line. This velocity is used to calculate a revised distance estimate of 650 ± 100 pc. Using the electron density derived from the [S ii] ratio, an ionized mass of 0.005 M⊙ is determined. The nature of the bright knot situated to the north‐west of the PN is investigated at optical and radio wavelengths. In optical emission lines it is found to be redshifted. It is located in the same region as the position of the peak flux density at 18 cm. It is shown that no evidence of a local density enhancement exists in its environs. It is suggested that the appearance of the knot is due to a temperature effect and its existence is interpreted in terms of a breach in the near side of the PN shell. The existence of a jet, at some stage in the evolution of the PN, is invoked to explain the mechanism by which such a breach may have been created.

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A radio continuum study of the ‘Engraved Hourglass’ nebula, MyCn 18

Cited by 3 publications

References 21 publications

VLT observations of the asymmetric Etched Hourglass Nebula, MyCn 18

VLT observations of the asymmetric Etched Hourglass Nebula, MyCn 18

The radio structure of Menzel 3

High-resolution radio structure and optical kinematics of NGC 7027

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