Proper‐Motion Measurements of the Cygnus Egg Nebula

Ueta, Toshiya; Murakawa, K.; Meixner, Margaret

doi:10.1086/500642

Cited by 31 publications

(45 citation statements)

References 37 publications

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“…Our results for these two sources probe the region beyond $100 00 from the central star, which corresponds to 1:0 ; 10 4 yr ago for AFGL 2688 and 2:8 ; 10 4 yr ago for OH 231.8, given a distance of 420 pc ( Ueta et al 2006) and 1.2 kpc (Jura & Morris 1985), respectively, and an expansion velocity of 20 km s À1 . We can set a limit on the dust mass-loss rate by inverting equation (1),…”

Section: Discussionmentioning

confidence: 54%

“…The equations above also show the temperature dependence in the form of a power law to approximate the blackbody function between 22 and 35 K. From these equations we see that the temperature dependence at 160 m is less steep than at 70 m, but the contamination by Galactic cirrus near the sources makes estimating upper limits problematic at 160 m. We can establish an upper limit to the mass-loss rates for AFGL 2688 and OH 231.8 at 70 m based on the surface brightness of the residual left from the PSF subtraction at 200 00 from the source, which is a compromise between a location far enough from the source that PSF subtraction errors are small and a location close enough to the source that there could plausibly be a circumstellar envelope. For AFGL 2688, 200 00 corresponds to a radial distance from the source of 0.4 pc, using a distance to the source of 420 pc (Ueta et al 2006). The surface brightness after PSF subtraction with the model PSF is about 14 MJy sr À1 at 70 m. Assuming an expansion velocity of 20 km s À1 as observed in CO by Skinner et al (1997), a dust temperature of 30 K, ¼ 104 cm 2 g À1 appropriate for carbon dust (Draine & Lee 1984), and that the possible envelope has a radius significantly greater than 0.4 pc, the dust mass-loss rate upper limit is 2:1 ; 10 À7 M yr…”

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confidence: 99%

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ASpitzerStudy of the Mass-Loss Histories of Three Bipolar Preplanetary Nebulae

Morris

Sahai

et al. 2007

Astron J

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We present the results of far-infrared imaging of extended regions around three bipolar preplanetary nebulae, AFGL 2688, OH 231.8+4.2, and IRAS 16342À3814, at 70 and 160 m with the MIPS instrument on the Spitzer Space Telescope. After a careful subtraction of the point-spread function of the central star from these images, we place constraints on the existence of extended shells and thus on the mass outflow rates as a function of radial distance from these stars. We find no apparent extended emission in AFGL 2688 and OH 231.8+4.2 beyond 100 00 from the central source. In the case of AFGL 2688, this result is inconsistent with a previous report of two extended dust shells made on the basis of ISO observations. We derive upper limits of 2:1 ; 10 À7 and 1:0 ; 10 À7 M yr À1 for the dust mass-loss rates of AFGL 2688 and OH 231.8, respectively, at 200 00 from each source. In contrast to these two sources, IRAS 16342À3814 does show extended emission at both wavelengths, which can be interpreted as a very large dust shell with a radius of $400 00 and a thickness of $100 00 , corresponding to 4 and 1 pc, respectively, at a distance of 2 kpc. However, this enhanced emission may also be Galactic cirrus; better azimuthal coverage is necessary for confirmation of a shell. If the extended emission is a shell, it can be modeled, with some assumptions about its dust properties, as enhanced mass outflow at a dust mass outflow rate of 1:5 ; 10 À6 M yr À1 superimposed on a steady outflow with a dust mass outflow rate of 1:5 ; 10 À7 M yr À1. Because of the size of the possible shell, it is likely that this shell has swept up a substantial mass of interstellar gas during its expansion, so these estimates are upper limits to the stellar mass-loss rate. We find a constant color temperature of 32 K throughout the circumstellar envelope of IRAS 16342À3814, which is consistent with heating by the interstellar radiation field.

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Section: Discussionmentioning

confidence: 54%

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confidence: 99%

ASpitzerStudy of the Mass-Loss Histories of Three Bipolar Preplanetary Nebulae

Morris

Sahai

et al. 2007

Astron J

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“…However, it is very difficult to see whether these equatorial flows have similar kinetic ages (so as to compare them with those for the axial jets). For the axial flows, this Hubble-law velocity field has been recently confirmed by Ueta et al (2006), by means of proper motion measurements using HST NICMOS images. Another interesting case is CRL 618.…”

Section: The Origin Of the Ppn M 1-92mentioning

confidence: 58%

Minkowski's footprint revisited

Alcolea¹,

Neri

Bujarrabal

2007

A&A

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Context. M 1-92 can be considered an archetype of bipolar pre-planetary nebulae. It shows a clear axial symmetry, along with the kinematics and momentum excess characteristic of this class of envelopes around post-AGB stars. Aims. By taking advantage of the new extended configuration of the IRAM Plateau de Bure interferometer, we wanted to study the morphology and velocity field of the molecular gas better in this nebula, particularly in its central part.Methods. We performed sub-arcsecond resolution interferometric observations of the J = 2−1 rotational line of 13 CO in M 1-92. Results. We found that the equatorial component is a thin flat disk, which expands radially with a velocity proportional to the distance to the center. The kinetic age of this equatorial flow is very similar to that of the two lobes. The small widths and velocity dispersion in the gas forming the lobe walls confirm that the acceleration responsible for the nebular shape could not last more than 100-120 yr.Conclusions. The present kinematics of the molecular gas can be explained as the result of a single brief acceleration event, after which the nebula reached an expansion velocity field with axial symmetry. In view of the similarity to other objects, we speculate on the possibility that the whole nebula was formed as a result of a magneto-rotational explosion in a common-envelope system.

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“…According to the calibration of Friedman et al (), this corresponds to E ( B − V ) = 0.1, suggesting that the interstellar reddening is very low at the line of sight of this object. Although CRL 2688 is located at low Galactic latitude at ( l , b ) = (80.166, −6.502), where integrated reddening is E ( B − V ) = 0.28 according to Schlegel, Finkbeiner & Davis (), the low E ( B − V ) value may be reasonable since the distance to this object was estimated to be only 420 pc (Ueta, Murakawa & Meixner ). On the other hand, photometric observations of Ney et al () suggest that the extinction towards this object at visual wavelengths is at least 3 mag.…”

Section: Description Of the Spectrummentioning

confidence: 99%

The chemical composition of the post-asymptotic giant branch F supergiant CRL 2688

Ishigaki

Parthasarathy

Reddy

et al. 2012

Monthly Notices of the Royal Astronomical Society

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We present an analysis of a high‐resolution (R ∼ 50 000) optical spectrum of the central region of the protoplanetary nebula CRL 2688. This object is thought to have recently moved off the asymptotic giant branch (AGB) and displays abundance patterns of CNO and heavy elements that can provide us with important clues to help us understand the nucleosynthesis, dredge‐up and mixing experienced by the envelope of the central star during its AGB stage of evolution. Analysis of the molecular features, presumably originating from circumstellar matter, provides further constraints on the chemistry and velocity of the expanding shell, expelled as a consequence of the strong mass loss experienced by the central star. We confirm that the central star shows a spectrum typical of an F‐type supergiant with Teff = 7250 ± 400 K, log g = 0.5 and [Fe/H] = −0.3 ± 0.1 dex. We find that the abundance pattern of this object is characterized by enhancements of carbon ([C/Fe] = 0.6 ± 0.1), nitrogen ([N/Fe] = 1.0 ± 0.3) and Na ([Na/Fe] = 0.7 ± 0.1), similar to other previously known carbon‐rich post‐AGB stars. Yttrium is also enhanced, while the [Ba/Y] ratio is very low (−1.0), indicating that only the light s‐process elements are enhanced. The zinc abundance is found to be normal, [Zn/Fe] = 0.0 ± 0.3, suggesting that there is no depletion of refractory elements. The Hα, Na i and K i resonance lines show prominent emission components, the heliocentric radial velocities of which are offset by −41 ± 3 km s−1 relative to the photospheric metal‐absorption lines. The molecular features of C2 and CN also show emission components, the velocities of which are consistent with the emission components of the Hα, Na i and K i lines. On the other hand, their absorption components are more highly blueshifted than the corresponding emission components, which suggests that the regions where the emission and absorption components arise are expanding at different velocities.

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Proper‐Motion Measurements of the Cygnus Egg Nebula

Cited by 31 publications

References 37 publications

ASpitzerStudy of the Mass-Loss Histories of Three Bipolar Preplanetary Nebulae

ASpitzerStudy of the Mass-Loss Histories of Three Bipolar Preplanetary Nebulae

Minkowski's footprint revisited

The chemical composition of the post-asymptotic giant branch F supergiant CRL 2688

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