Multiple circumstellar shells and radiation pressure on grains in the outflows from late-type giants

1984 ◽  
Vol 282 ◽  
pp. 200 ◽  
Author(s):  
M. Jura
Keyword(s):  
Radiation Pressure ◽  
Late Type ◽  
Circumstellar Shells

scholarly journals Atlas of Main-line OH Masers in the Galactic Longitude Range 3° to 60°

1983 ◽  
Vol 36 (3) ◽  
pp. 417 ◽  
Author(s):  
JL Caswell ◽  
RF Haynes
Keyword(s):  
Star Formation ◽  
Circular Polarization ◽  
Galactic Plane ◽  
Hii Regions ◽  
Main Line ◽  
Late Type ◽  
Circumstellar Shells ◽  
Many Sources ◽  
First Time ◽  
Galactic Longitude

We tabulate all 55 OH main-line masers discovered to date in the galactic plane between longitude 3� and 60�. For most of these we show current spectra, which have been taken with the Parkes 64 m radio telescope, in both senses of circular polarization on the 1665 MHz and/or 1667 MHz transitions; for some sources we give new position estimates, and several sources are reported for the first time. We discuss many sources individually and note that while most of the main-line OH masers probably pinpoint compact HII regions and sites of current star formation, a few appear to be unusual varieties occurring in circumstellar shells, possibly associated with late-type stars.

scholarly journals The Effects of Alfven Waves and Radiation Pressure in Dust Winds of Late‐Type Stars

2002 ◽  
Vol 576 (2) ◽  
pp. 976-981 ◽  
Author(s):  
D. Falceta‐Goncalves ◽  
V. Jatenco‐Pereira
Keyword(s):  
Radiation Pressure ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Late Type

scholarly journals Mass-Loss from Late-Type Stars: New Observational Evidence

1983 ◽  
Vol 103 ◽  
pp. 292-292
Author(s):  
P. G. Wannier ◽  
R. Sahai
Keyword(s):  
Mass Loss ◽  
Central Star ◽  
Ir Absorption ◽  
Late Type ◽  
Ir Radiation ◽  
Loss Mechanism ◽  
Continuum Source ◽  
Near Ir ◽  
Molecular Lines ◽  
Circumstellar Shells

Rapid mass-loss is observed in many late-type stars, yet the mass-loss mechanisms operating are not well understood. A survey of molecular emission from circumstellar shells has been carried out using millimeterwave molecular lines and suggests that radiation pressure alone may be inadequate to explain the observed mass-loss, especially in the case of carbon-rich objects which may display rates in excess of 10−5 M⊙/yr. Recent near-IR molecular line observations provide evidence for ejected material at several different velocities along the line-of-sight and may indicate the additional mass-loss mechanism at work. Resonantly scattered IR radiation spatially displaced from the central IR continuum source has now been observed for the first time and sheds new light on the IR absorption-line results, providing information about material within 1016 cm of the central star. These results are discussed along with recent high-resolution millimeterwave observations.

scholarly journals Infrared Observations of Circumstellar Molecules

1987 ◽  
Vol 120 ◽  
pp. 327-338 ◽  
Author(s):  
Albert Betz
Keyword(s):  
Infrared Spectroscopy ◽  
Mass Loss ◽  
Abundant Species ◽  
High Resolution Spectroscopy ◽  
Late Type ◽  
Infrared Observations ◽  
Negative Results ◽  
Circumstellar Gas ◽  
Circumstellar Shells ◽  
Vantage Points

This review presents an updated listing of infrared observations of circumstellar molecules. The compendium is restricted to the more abundant species with infrared spectra accessible to groundbased observations. No analysis is offered on the chemical importance of a particular species, and no attempt is made to correlate the infrared work with the much larger body of data available from radio frequency observations. Some discussions of these topics may be found in the more comprehensive reviews listed below. The observations described here include both the successful and the unrewarded efforts. Often the negative results from attempted observations are not widely disseminated, even though such results can sometimes be of significant theoretical value. Discussions of infrared stellar and circumstellar spectroscopy from other vantage points may be found in the following reviews. in 1979 Merrill and Ridgway surveyed the contributions of infrared spectroscopy to studies of stellar photospheres and the near circumstellar environment. The following year Zuckerman (1980) summarized the current state of knowledge on circumstellar molecular clouds with attention given to both infrared and microwave observations. Ridgway and Keady (1981) subsequently noted the importance of infrared spectroscopy for studies of circumstellar gas and dust in the star IRC + 10216. in 1983 Hinkle reviewed the high-resolution spectroscopy of late-type circumstellar shells in general but emphasized chemistry and kinematics. Finally, in the proceedings of the 1984 UCLA meeting on mass-loss, Omont (1985) reviewed the physical and chemical structure of circumstellar envelopes and IRC + 10216 in particular, and Wannier (1985) discussed the significance of infrared spectroscopy for studies of mass-loss in late-type stars.

scholarly journals Ice Mantle Formation in the Envelopes of OH/IR Stars

1993 ◽  
Vol 155 ◽  
pp. 329-329
Author(s):  
S.B. Charnley ◽  
R.G. Smith
Keyword(s):  
Mass Loss ◽  
Simple Theory ◽  
Late Type ◽  
Water Ice ◽  
Physical Conditions ◽  
Grain Interaction ◽  
Inner Radius ◽  
Ir Stars ◽  
Circumstellar Shells ◽  
Loss Rates

We have computed ice column densities for a sample of O-rich late-type stars.Water ice is observed in the outflows from several late-type stars (e.g. Smith et al. 1988) and it is of some observational and theoretical importance to understand how common ice mantles may be and how their formation depends upon the physical conditions in the envelope, such as the radial distributions of density and temperature. We have developed a simple theory of the gas-grain interaction in circumstellar shells (Jura & Morris 1985; Charnley et al. 1992) and used it to compute ice column densities (Nice) and mantle thicknesses (d) for a sample of well-studied OH/IR stars (Herman & Habing 1985). The models are most sensitive to the dust and gas mass loss rates, as well as to the inner radius of the envelope, Ri, which is poorly determined. Representative results are presented in the Table below where Ri was estimated according to the prescription of Herman et al. (1986).

scholarly journals Cool Star Winds – Recent Observations and Theoretical Implications

1983 ◽  
Vol 6 ◽  
pp. 549-563 ◽  
Author(s):  
L. Hartmann
Keyword(s):  
Mass Loss ◽  
Absorption Lines ◽  
Late Type ◽  
Cool Star ◽  
Circumstellar Shells ◽  
Loss Rates ◽  
Loss Mechanisms

Much of our knowledge of winds from late-type stars comes from the detection of ejected material, called circumstellar shells, as observed in absorption lines of low-excitation species such as Mg II, Ca II, Na I, and K I (cf. Reimers 1977). Observations of CS shells are difficult to translate into quantitative mass loss rates, a limitation which has not helped to test various mass loss mechanisms. The data clearly demonstrate one very important fact: shell velocities are very low. In fact, they are so much lower than surface escape velocitiesthat it was not clear that material is actually being lost until Deutsch (1956) detected the existence of the CS absorption shells ejected from α Her and α Sco in the spectra of distant companion stars. Today it is possible to demonstrate the expansion of shells out to several thousand stellar radii in K I scattering (Honeycutt et al. 1980).

scholarly journals Report on a Survey of H2O Masers Towards the Galactic Center

1996 ◽  
Vol 169 ◽  
pp. 343-344
Author(s):  
Deborah A. Levine ◽  
Mark Morris
Keyword(s):  
Galactic Center ◽  
Point Sources ◽  
Late Type ◽  
Star Forming ◽  
Star Forming Regions ◽  
Circumstellar Shells

Galactic H2O masers are associated either with the circumstellar shells of late-type stars or with star-forming regions (SFRs). Previous surveys for H2O masers had revealed relatively few near the Galactic Center (GC). We report on the continuation of a survey using the VLA to make 22.2 GHz observations of IRAS point sources which lie within 2° of the GC and which have either 12 μm or 25 μm flux > 8 Jy. Taylor, Morris and Schulman (TMS, 1992, AJ, 106, 1978) previously observed 97 of 342 candidate sources. We have observed 160 more and plan to complete the survey in early 1995.

scholarly journals 3.20. OH/IR stars as signposts for ancient starburst activity in the Galactic center

1998 ◽  
Vol 184 ◽  
pp. 129-130 ◽  
Author(s):  
L.O. Sjouwerman ◽  
H.J. Habing ◽  
H.J. van Langevelde ◽  
M. Lindqvist ◽  
A. Winnberg
Keyword(s):  
Mass Loss ◽  
Galactic Center ◽  
Expansion Velocity ◽  
Late Type ◽  
Considerable Fraction ◽  
Ir Stars ◽  
Circumstellar Shells

We have surveyed the Galactic center (GC) for OH/IR stars, evolved late-type stars of different masses - and thus ages - in a short-lived stage of heavy mass-loss. By observing the 1612 MHz OH masers generated in their circumstellar shells, it is found that a considerable fraction of these OH/IR stars has the same high-valued shell expansion velocity of 19 km s−1.

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