scholarly journals Circumstellar dust shells around WN10-11 and WC8-10 stars: An evolutionary sequence?∗

1984 ◽  
Vol 105 ◽  
pp. 273-277
Author(s):  
K.A. van der Hucht ◽  
P.M. Williams ◽  
P.S. Thé
Keyword(s):  
Circumstellar Dust ◽  
Evolutionary Sequence ◽  
Late Type ◽  
Dust Shells ◽  
Density Distributions

In a recent IR photometric survey of late-type WC and WN stars, it was discovered that not only most WC8-10 stars have circumstellar dust shells, but that two extreme late-type WN stars also have strong IR excesses from circumstellar dust. The latter shells appear to have significantly different density distributions. In this paper the possibility of an evolutionary sequence is suggested.

scholarly journals Long Baseline Interferometric Observations of Circumstellar Dust Shells at 11 Microns

1994 ◽  
Vol 158 ◽  
pp. 383-386
Author(s):  
W.C. Danchi ◽  
L. Greenhill ◽  
M. Bester ◽  
C.G. Degiacomi ◽  
C.H. Townes ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Radiative Transfer ◽  
Circumstellar Dust ◽  
Dust Formation ◽  
Late Type ◽  
Dust Shells ◽  
Long Baseline ◽  
Higher Temperature ◽  
Single Baseline ◽  
Radiative Transfer Modeling

The spatial distribution of dust around a sample of well-known late-type stars has been studied with the Infrared Spatial Interferometer (ISI) located at Mt. Wilson. Currently operating with a single baseline as a heterodyne interferometer at 11.15 μm, the ISI has obtained visibility curves of these stars. Radiative transfer modeling of the visibility curves has yielded estimates of the inner radii of the dust shells, the optical depth at 11 μm, and the temperature of the dust at the inner radii. For stars in which the dust is resolved, estimates of the stellar diameter and temperature can also be made. Broadly speaking two classes of stars have been found. One class has inner radii of their dust shells very close to the photospheres of the stars themselves (3–5 stellar radii) and at a higher temperature (~ 1200 K) than previously measured. This class includes VY CMa, NML Tau, IRC +10216, and o Ceti. For the latter two the visibility curves change with the luminosity phase of the star and new dust appears to form at still smaller radii during minimum luminosity. The second class of stars has dust shells with substantially larger inner radii and very little dust close to the stars, and includes α Ori, α Sco, α Her, R Leo, and χ Cyg. This indicates sporadic production of dust and no dust formation within the last several decades.

scholarly journals Models for IRAS observations of circumstellar dust shells around late-type stars

1986 ◽  
Vol 222 (2) ◽  
pp. 273-286 ◽  
Author(s):  
M. Rowan-Robinson ◽  
T. D. Lock ◽  
D. W. Walker ◽  
S. Harris
Keyword(s):  
Circumstellar Dust ◽  
Late Type ◽  
Dust Shells

scholarly journals Mid-IR (8–13μm) Images of Proto-Planetary Nebulae

1993 ◽  
Vol 155 ◽  
pp. 343-343
Author(s):  
M. Meixner ◽  
J.F. Arens ◽  
J.G. Jernigan ◽  
C.J. Skinner ◽  
G. Hawkins
Keyword(s):  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Circumstellar Dust ◽  
Morphological Development ◽  
Evolutionary Sequence ◽  
Optical Studies ◽  
Ir Camera ◽  
Dust Shells ◽  
Near Ir ◽  
Pn Stage

We present mid-IR (8–13μm) images of dust in seven proto-planetary nebulae (PPN), GL2343, HD 161796, 89 Her, OH 0739–1435, CRL2688, IRAS 22272+5435, and CRL618. The images were taken at UKIRT and the IRTF with the Berkeley mid-IR camera which was developed at the Space Sci. Lab. in UC Berkeley and is supported by IGPP and LEA, LLNL. The results presented here are part of an on-going mid-IR imaging project to study the morphological development of a star as it evolves from the Asymptotic Giant Branch (AGB) to the planetary nebula (PN) stage. In particular, we aim to establish when non-spherical symmetry which is evident in so many PN arises. Four of the objects are oxygen rich. Of these, GL2343 (Fig. 1) and HD 161796 are found to have spherical dust shells in the mid-IR with diameters of 6.″ 7 and 3″, respectively. OH 0739 is marginally resolved, but has a hint of elongation that is aligned with the bipolar nebula evident in the near-IR. 89 Her is unresolved at 1.″ 1 resolution. 89 Her, HD 161796 and GL2343, all high latitude supergiants, appear to form an evolutionary sequence as evidenced by the size of their circumstellar dust shells. Three of the objects are carbon rich. CRL2688 and IRAS 22272 +5435 are found to have elongated structures which suggest a bipolar morphology. CRL 618 is unresolved at 1.″ 7, but is known to be bipolar from optical studies. Hence, with the exception of OH 0739, a known binary, the oxygen rich PPN have spherical dust shells while the carbon rich have bipolar dust shells. Our small number of observations do not provide solid statistics; however, this trend suggests that nebula bipolarity is linked to carbon-rich chemistry.

scholarly journals Gaia DR2 data and the evolutionary status of eight high-velocity hot post-AGB candidates

2020 ◽  
Vol 72 (6) ◽  
Author(s):  
Mudumba Parthasarathy ◽  
Tadafumi Matsuno ◽  
Wako Aoki
Keyword(s):  
Effective Temperature ◽  
High Velocity ◽  
Circumstellar Dust ◽  
Evolutionary Status ◽  
Agb Stars ◽  
Horizontal Branch ◽  
Dust Shells ◽  
The Past ◽  
Gaia Dr2 ◽  
Branch Star

Abstract From Gaia DR2 data of eight high-velocity hot post-AGB candidates, LS 3593, LSE 148, LS 5107, HD 172324, HD 214539, LS IV −12 111, LS III +52 24, and LS 3099, we found that six of them have accurate parallaxes which made it possible to derive their distances, absolute visual magnitudes (MV) and luminosity (log L/L⊙). All the stars except LS 5107 have an accurate effective temperature (Teff) in the literature. Some of these stars are metal poor, and some of them do not have circumstellar dust shells. In the past, the distances of some stars were estimated to be 6 kpc, which we find to be incorrect. The accurate Gaia DR2 parallaxes show that they are relatively nearby, post-AGB stars. When compared with post-AGB evolutionary tracks we find their initial masses to be in the range 1 M⊙ to 2 M⊙. We find the luminosity of LSE 148 to be significantly lower than that of post-AGB stars, suggesting that this is a post-horizontal-branch star or post-early-AGB star. LS 3593 and LS 5107 are new high-velocity hot post-AGB stars from Gaia DR2.

Characteristics of dust shells around 13 late-type stars

1994 ◽  
Vol 107 ◽  
pp. 1469 ◽  
Author(s):  
W. C. Danchi ◽  
M. Bester ◽  
C. G. Degiacomi ◽  
L. J. Greenhill ◽  
C. H. Townes
Keyword(s):  
Late Type ◽  
Dust Shells
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