scholarly journals Observations of Long Period Variable Stars

1989 ◽  
Vol 106 ◽  
pp. 241-257
Author(s):  
T. Lloyd Evans
Keyword(s):  
Chemical Composition ◽  
Stellar Population ◽  
Variable Stars ◽  
Circumstellar Dust ◽  
Stellar Systems ◽  
Intrinsic Properties ◽  
Long Period ◽  
Large Samples ◽  
Period Variable ◽  
Infrared Wavelengths

The study of long period variable stars has been transformed in recent years by two observational developments. Large samples of stars have been observed at infrared wavelengths, providing knowledge of the intrinsic properties of the star as well as of circumstellar dust shells, and these observations have been extended to the variables in well defined stellar systems to allow their properties to be studied in relation to the stellar population to which they belong. Spectroscopic determinations of chemical composition have also provided several crucial insights.

scholarly journals A Search for Variable Stars at the Galactic Center

1989 ◽  
Vol 136 ◽  
pp. 487-492 ◽  
Author(s):  
Joseph W. Haller ◽  
Marcia J. Rieke
Keyword(s):  
Stellar Population ◽  
Galactic Center ◽  
Ccd Camera ◽  
Variable Stars ◽  
Detector Array ◽  
High Luminosity ◽  
Bolometric Luminosity ◽  
Long Period ◽  
Long Period Variables ◽  
K 13

A study of the Galactic Center stellar population is continuing with a sensitive 2μm CCD camera. Using a 64 × 64 detector array, background limited images are recorded with modest amounts of observing time (tobs ≈ 20 sec to reach K=13). Magnitudes have been extracted using DAOPHOT from repeated imaging of the central 5′ × 5′ to search among approximately 1500 stars for long period variables (LPV's, P > 200d), particularily Miras. Miras have a well defined period-luminosity relationship as well as one in period-mass. This program investigates the nature of highly luminous stars at the Galactic Center. Presently 12 variables have been found and have several characteristics consistent with Miras. They have a maximum bolometric luminosity of −4.4 mag, which supports the case that high luminosity stars in the central 6 pc are young supergiants.

scholarly journals The Evolving Radio Photospheres of Long-period Variable Stars

2018 ◽  
Vol 156 (1) ◽  
pp. 15 ◽  
Author(s):  
L. D. Matthews ◽  
M. J. Reid ◽  
K. M. Menten ◽  
K. Akiyama
Keyword(s):  
Variable Stars ◽  
Long Period ◽  
Period Variable

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).

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