scholarly journals WR 120bb and WR 120bc: a pair of WN9h stars with possibly interacting circumstellar shells

2013 ◽  
Vol 429 (4) ◽  
pp. 3305-3315 ◽  
Author(s):  
S. Burgemeister ◽  
V. V. Gvaramadze ◽  
G. S. Stringfellow ◽  
A. Y. Kniazev ◽  
H. Todt ◽  
...  
Keyword(s):  
Circumstellar Shells

The circumstellar shells of carbon miras

1995 ◽  
Vol 224 (1-2) ◽  
pp. 321-324 ◽  
Author(s):  
Martin Groenewegen
Keyword(s):  
Circumstellar Shells

Nonequilibrium Chemistry in Circumstellar Shells

1988 ◽  
pp. 231-248 ◽  
Author(s):  
A. Goeres ◽  
R. Henkel ◽  
E. Sedlmayr ◽  
H.-P. Gail
Keyword(s):  
Circumstellar Shells ◽  
Nonequilibrium Chemistry

Masers in Circumstellar Shells

1987 ◽  
pp. 369-377
Author(s):  
C. M. Walmsley
Keyword(s):  
Circumstellar Shells

scholarly journals Mainline and water maser observations of OH/IR stars in the Arecibo sky

1997 ◽  
Vol 180 ◽  
pp. 356-356
Author(s):  
B. M. Lewis
Keyword(s):  
Detection Rate ◽  
Planetary Nebulae ◽  
Complete Sample ◽  
Detection Rates ◽  
Ir Stars ◽  
Circumstellar Shells ◽  
Water Masers ◽  
The Many ◽  
Water Maser

A complete sample of color selected IRAS sources with S(25) ≥ 2 Jy in the Arecibo sky and(0° ≤ δ ≤ 37°) was examined previously for 1612 MHz masers. The resulting set of OH/IR stars has now been searched for mainline OH masers at Arecibo (Lewis 1997) and for 22 GHz water masers at Effelsberg (Engels & Lewis 1996). The high overall detection rate of 61.6% for the mainlines and 54.8% for water is partly a result of deployed sensitivity, and partly due to the many blue objects in the sample. But the detectability of both masers improves when S(25)> 20 Jy, as the accompanying tables show. Still the bluest objects exhibit higher (usually ≥80%) detection rates, while there is a clear decrease in detections from redder shells: this decrease begins circa (25–12) μm=–0.55 for mainline masers, and abruptly circa (25–12) μm = −0.35 for water. These trends adhere to the descriptive sequence of the chronological scenario for masers in circumstellar shells, though a few proto planetary nebulae and very red OH/IR stars have water masers and a few mainline masers are detected in shells with (25-12) μm ≥ −0.2.

scholarly journals Dust formation in oxygen-rich circumstellar shells around long–period variables

1999 ◽  
Vol 191 ◽  
pp. 233-238 ◽  
Author(s):  
Kyung Sook Jeong ◽  
Jan Martin Winters ◽  
Erwin Sedlmayr
Keyword(s):  
Variable Star ◽  
Chemical Species ◽  
Circumstellar Dust ◽  
Agb Stars ◽  
Fluid Element ◽  
Dust Grains ◽  
Promising Candidate ◽  
Long Period ◽  
Period Variable ◽  
Circumstellar Shells

We present the first steps of our work aimed at a consistent time-dependent modeling of oxygen–rich circumstellar dust shells (CDS) around pulsating AGB stars. The nature of the most likely nucleation seeds is investigated for this situation and we find that TiO2 is a most promising candidate to serve as the primary condensate, forming already at temperatures well above 1 000 K. These nuclei evolve to macroscopic dust grains by heterogeneous growth processes involving several chemical species. We investigate the varying chemical composition of the resulting dust grains as they evolve as a function of time in a fluid element moving through the CDS of an oxygen–rich long-period variable star (LPV).

scholarly journals Opening PANDORA’s box: APEX observations of CO in PNe

2018 ◽  
Vol 618 ◽  
pp. A91 ◽  
Author(s):  
L. Guzman-Ramirez ◽  
A. I. Gómez-Ruíz ◽  
H. M. J. Boffin ◽  
D. Jones ◽  
R. Wesson ◽  
...  
Keyword(s):  
Column Density ◽  
Planetary Nebulae ◽  
Close Binaries ◽  
Physical Parameters ◽  
Molecular Gas ◽  
Intermediate Mass Stars ◽  
Circumstellar Shells ◽  
Large Survey ◽  
Late Stages ◽  
The Universe

Context. Observations of molecular gas have played a key role in developing the current understanding of the late stages of stellar evolution. Aims. The survey Planetary nebulae AND their cO Reservoir with APEX (PANDORA) was designed to study the circumstellar shells of evolved stars with the aim to estimate their physical parameters. Methods. Millimetre carbon monoxide (CO) emission is the most useful probe of the warm molecular component ejected by low- to intermediate-mass stars. CO is the second-most abundant molecule in the Universe, and the millimetre transitions are easily excited, thus making it particularly useful to study the mass, structure, and kinematics of the molecular gas. We present a large survey of the CO (J = 3−2) line using the Atacama Pathfinder EXperiment (APEX) telescope in a sample of 93 proto-planetary nebulae and planetary nebulae. Results. CO (J = 3−2) was detected in 21 of the 93 objects. Only two objects (IRC+10216 and PN M2-9) had previous CO (J = 3−2) detections, therefore we present the first detection of CO (J = 3−2) in the following 19 objects: Frosty Leo, HD 101584, IRAS 19475+3119, PN M1-11, V* V852 Cen, IC 4406, Hen 2-113, Hen 2-133, PN Fg 3, PN Cn 3-1, PN M2-43, PN M1-63, PN M1-65, BD+30 3639, Hen 2-447, Hen 2-459, PN M3-35, NGC 3132, and NGC 6326. Conclusions. CO (J = 3−2) was detected in all 4 observed pPNe (100%), 15 of the 75 PNe (20%), one of the 4 wide binaries (25%), and in 1 of the 10 close binaries (10%). Using the CO (J = 3−2) line, we estimated the column density and mass of each source. The H2 column density ranges from 1.7 × 1018 to 4.2 × 1021 cm−2 and the molecular mass ranges from 2.7 × 10−4 to 1.7 × 10−1 M⊙.

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