Kayser, Susan Elizabeth (1966) Photometry of the nearby irregular galaxy, NGC 6822. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-09232002-112325
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NGC 6822 is a member of the Local Group, type Im, coordinates [...]. The main body has a diameter of 3.6 c kpc and a mass (from radio rotation curves) of [...]. Mass-to-light ratio is 6.1 x c[superscript -1]. The color-magnitude diagram is plotted from measures on photographic plates calibrated by a photoelectric sequence. Photometry is complete to 19.5 (M[subscript v] = -5). Major features are bright blue supergiants, the brightest star having M [subscript v] = -9, and a sequence of very red supergiants one magnitude fainter than the blue, many of which show variations of over 1000 days. A significant number of stars lie in the Hertzsprung gap. Two-color photometry shows there is intervening reddening of [...]. A luminosity function is calculated.
Thirty-two variable stars are discussed, of which thirteen are Cepheids, two are red semi-regulars, one may be eclipsing, and the others are irregular. The period-luminosity relations for the Cepheids are < V > = 23.35 - 2. 97 log P and < B > = 23.91 - 2.61 log P. These lead to a true distance modulus (m-M) = 23.75 [plus or minus] 0.10. Secular changes in period are less than 0.001% in 40 years. The eleven variables with 1.6 < (B-V)[...] < 2. 1 have cycles 200-2500 days.
Comparisons with evolutionary models indicate that the stars observed have masses of 9 to 63 [...].
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Subject Keywords:||irregular galaxy; Local Group; NGC 6822|
|Degree Grantor:||California Institute of Technology|
|Division:||Physics, Mathematics and Astronomy|
|Thesis Availability:||Public (worldwide access)|
|Defense Date:||13 December 1965|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Imported from ETD-db|
|Deposited On:||24 Sep 2002|
|Last Modified:||26 Dec 2012 03:02|
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