Browsing by Subject "milky way"

Now showing 1 - 3 of 3
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    A more general model for the intrinsic scatter in type Ia supernova distance moduli
    (2011) Marriner, John; Bernstein, J P; Kessler, Richard; Lampeitl, Hubert; Miquel, Ramon; Mosher, Jennifer; Nichol, Robert C; Sako, Masao; Schneider, Donald P; Smith, Mathew
    We describe a new formalism to fit the parameters {alpha} and {beta} that are used in the SALT2 model to determine the standard magnitudes of Type Ia supernovae (SNe Ia). The new formalism describes the intrinsic scatter in SNe Ia by a covariance matrix in place of the single parameter normally used. We have applied this formalism to the Sloan Digital Sky Survey Supernova Survey (SDSS-II) data and conclude that the data are best described by {alpha} = 0.135{sup +.033} - .017 and {beta} = 3.19{sup +0.14} - 0.24, where the error is dominated by the uncertainty in the form of the intrinsic scatter matrix. Our result depends on the introduction of a more general form for the intrinsic scatter of the distance moduli of SNe Ia than is conventional, resulting in a larger value of {beta} and a larger uncertainty than the conventional approach. Although this analysis results in a larger value of {beta} and a larger error, the SDSS data differ (at a 98% confidence level) from {beta} = 4.1, the value expected for extinction by the type of dust found in the Milky Way. We have modeled the distribution of SNe Ia in terms of their colormore » and conclude that there is strong evidence that variation in color is a significant contributor to the scatter of SNe Ia around their standard candle magnitude.« less
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    A study of the galactic star cluster NGC 2547
    (1955) Fernie, John Donald
    The following thesis has been undertaken primarily as an observational study. Accordingly, theoretical discussion and speculations have been kept to a minimum, formulas in most case being early quoted and references given for their derivations. Since the observational techniques used are nearly all in standard practice, they have not been fully described, while descriptions of their reductions have been relegated to appendices.
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    Galactic and extragalactic distance scales: Some South African contributions
    (2005) Feast, Michael
    The work of South African astronomers in establishing and refining methods of measuring the distances of stars and galaxies is reviewed.