scholarly journals The Circumstellar Envelope of the Semiregular Variable Star V CVn

2019 ◽  
Vol 45 (7) ◽  
pp. 453-461
Author(s):  
B. S. Safonov ◽  
A. V. Dodin ◽  
S. A. Lamzin ◽  
A. S. Rastorguev
Keyword(s):  
Variable Star ◽  
Circumstellar Envelope ◽  
Semiregular Variable

scholarly journals VLBI studies of SiO masers around VX Sagittarii

2007 ◽  
Vol 3 (S242) ◽  
pp. 312-313
Author(s):  
X. Chen ◽  
Z.-Q. Shen ◽  
D.-R. Jiang
Keyword(s):  
Variable Star ◽  
Circumstellar Envelope ◽  
Preliminary Results ◽  
Regular Variable

AbstractObservations of 43 GHz 28SiO (v = 1, J = 1-0) masers in the circumstellar envelope of the M-type semi-regular variable star VX Sgr were performed using the VLBA at 3 epochs during 1999 April-May. By tracing 42 matched maser features appearing in all the three epochs, we determined the contraction of an SiO maser shell toward VX Sgr at a velocity of about 4 km s−1 at a distance of 1.7 kpc to VX Sgr. We also report on some preliminary results from our first epoch of simultaneous VLBA observations of three 7 mm SiO masers toward VX Sgr.

scholarly journals Dust Formation and the Doubly-Periodic Variable Stars

1995 ◽  
Vol 155 ◽  
pp. 196-197
Author(s):  
T. Lloyd Evans
Keyword(s):  
Dust Cloud ◽  
Variable Stars ◽  
Emission Lines ◽  
Circumstellar Dust ◽  
Dust Formation ◽  
Circumstellar Envelope ◽  
Pulsation Period ◽  
Deep Minimum ◽  
Resonance Emission ◽  
Semiregular Variable

AbstractThe doubly-periodic semiregular variable V Hydrae became redder and developed resonance emission lines and bands during the 1992-94 deep minimum, which therefore resulted from the production of a circumstellar dust cloud. This removes the need to postulate a secondary pulsation period, ten times as long as the main pulsation period, in the stellar as opposed to circumstellar envelope.

On the Inhomogeneity of Chemical Composition over the Surface of 21 Per

1976 ◽  
Vol 32 ◽  
pp. 343-349
Author(s):  
Yu.V. Glagolevsky ◽  
K.I. Kozlova ◽  
V.S. Lebedev ◽  
N.S. Polosukhina
Keyword(s):  
Chemical Composition ◽  
Spectral Line ◽  
Variable Star ◽  
Radial Velocities ◽  
Crimean Astrophysical Observatory ◽  
Line Intensities ◽  
Magnetic Variable

SummaryThe magnetic variable star 21 Per has been studied from 4 and 8 Å/mm spectra obtained with the 2.6 - meter reflector of the Crimean Astrophysical Observatory. Spectral line intensities (Wλ) and radial velocities (Vr) have been measured.

Production of New and Revised A.A.V.S.O. Charts

1979 ◽  
Vol 46 ◽  
pp. 368
Author(s):  
Clinton B. Ford
Keyword(s):  
Variable Star ◽  
Standard Form ◽  
Original Data ◽  
University Of Pennsylvania ◽  
Standard Format ◽  
Additional Information ◽  
The Gift ◽  
The University

A “new charts program” for the Americal Association of Variable Star Observers was instigated in 1966 via the gift to the Association of the complete variable star observing records, charts, photographs, etc. of the late Prof. Charles P. Olivier of the University of Pennsylvania (USA). Adequate material covering about 60 variables, not previously charted by the AAVSO, was included in this original data, and was suitably charted in reproducible standard format.Since 1966, much additional information has been assembled from other sources, three Catalogs have been issued which list the new or revised charts produced, and which specify how copies of same may be obtained. The latest such Catalog is dated June 1978, and lists 670 different charts covering a total of 611 variables none of which was charted in reproducible standard form previous to 1966.

FIRST RESULTS FROM TIEN-SHAN SURVEY TO SEARCH FOR VARIABLE STARS: LIGHTCURVE ANALYSIS AND VARIABLE STAR CLASSIFICATION

2020 ◽  
Vol 3 (331) ◽  
pp. 81-91
Author(s):  
Serebryanskiy A., ◽  
◽  
Aimanova G. K., ◽  
Kondratyeva L.N., ◽  
Omarov Ch., ◽  
...  
Keyword(s):  
Variable Star ◽  
Variable Stars ◽  
Tien Shan ◽  
First Results ◽  
Star Classification

On Circumstellar Envelope Formation

1997 ◽  
Vol 489 (2) ◽  
pp. 946-950 ◽  
Author(s):  
G. Pascoli
Keyword(s):  
Circumstellar Envelope

scholarly journals Gas phase formation of c-SiC3molecules in the circumstellar envelope of carbon stars

2019 ◽  
Vol 116 (29) ◽  
pp. 14471-14478 ◽  
Author(s):  
Tao Yang ◽  
Luke Bertels ◽  
Beni B. Dangi ◽  
Xiaohu Li ◽  
Martin Head-Gordon ◽  
...  
Keyword(s):  
Carbon Star ◽  
Asymptotic Giant Branch ◽  
Formation Mechanisms ◽  
Circumstellar Envelope ◽  
Outer Envelope ◽  
Parent Molecule ◽  
Silicon Carbon ◽  
Electronically Excited ◽  
Circumstellar Environments ◽  
A Chain

Complex organosilicon molecules are ubiquitous in the circumstellar envelope of the asymptotic giant branch (AGB) star IRC+10216, but their formation mechanisms have remained largely elusive until now. These processes are of fundamental importance in initiating a chain of chemical reactions leading eventually to the formation of organosilicon molecules—among them key precursors to silicon carbide grains—in the circumstellar shell contributing critically to the galactic carbon and silicon budgets with up to 80% of the ejected materials infused into the interstellar medium. Here we demonstrate via a combined experimental, computational, and modeling study that distinct chemistries in the inner and outer envelope of a carbon star can lead to the synthesis of circumstellar silicon tricarbide (c-SiC3) as observed in the circumstellar envelope of IRC+10216. Bimolecular reactions of electronically excited silicon atoms (Si(1D)) with allene (H2CCCH2) and methylacetylene (CH3CCH) initiate the formation of SiC3H2molecules in the inner envelope. Driven by the stellar wind to the outer envelope, subsequent photodissociation of the SiC3H2parent operates the synthesis of the c-SiC3daughter species via dehydrogenation. The facile route to silicon tricarbide via a single neutral–neutral reaction to a hydrogenated parent molecule followed by photochemical processing of this transient to a bare silicon–carbon molecule presents evidence for a shift in currently accepted views of the circumstellar organosilicon chemistry, and provides an explanation for the previously elusive origin of circumstellar organosilicon molecules that can be synthesized in carbon-rich, circumstellar environments.

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