632 research outputs found
Approximating RR Lyrae light curves using cubic polynomials
In this paper, we use cubic polynomials to approximate RR Lyrae light curves
and apply the method to HST data of RR Lyraes in the halo of M31. We compare
our method to the standard method of Fourier decomposition and find that the
method of cubic polynomials eliminates virtually all ringing effects and does
so with significantly fewer parameters than the Fourier technique. Further, for
RRc stars the parameters in the fit are all physical. Our study also reveals a
number of additional periodicites in this data not found previously: we find 23
RRc stars, 29 RRab stars and 3 multiperiodic stars.Comment: 6 pages, MNRAS accepte
Large Magellanic Cloud Distance from Cepheid Variables using Least Squares Solutions
Distance to the Large Magellanic Cloud (LMC) is determined using the Cepheid
variables in the LMC. We combine the individual LMC Cepheid distances obtained
from the infrared surface brightness method and a dataset with a large number
of LMC Cepheids. Using the standard least squares method, the LMC distance
modulus can be found from the ZP offsets of these two samples. We have adopted
both a linear P-L relation and a ``broken'' P-L relation in our calculations.
The resulting LMC distance moduli are 18.48+-0.03 mag and 18.49+-0.04 mag
(random error only), respectively, which are consistent to the adopted 18.50
mag in the literature.Comment: 2 pages and 1 figure, to appear in proceeding of "Galaxies in the
Local Volume" Sydney 8-13 July 200
The Detailed Forms of the LMC Cepheid PL and PLC Relations
Possible deviations from linearity of the LMC Cepheid PL and PLC relations
are investigated. Two datasets are studied, respectively from the OGLE and
MACHO projects. A nonparametric test, based on linear regression residuals,
suggests that neither PL relation is linear. If colour dependence is allowed
for then the MACHO PL relation is found to deviate more significantly from the
linear, while the OGLE PL relation is consistent with linearity. These finding
are confirmed by fitting "Generalised Additive Models" (nonparametric
regression functions) to the two datasets. Colour dependence is shown to be
nonlinear in both datasets, distinctly so in the case of the MACHO Cepheids. It
is also shown that there is interaction between the period and colour functions
in the MACHO data.Comment: 20 pages, 20 figures, MNRAS accepte
Testing the nonlinearity of the BVIcJHKs period-luminosity relations for the Large Magellanic Cloud Cepheids
A number of recent works have suggested that the period-luminosity (PL)
relation for the Large Magellanic Cloud (LMC) Cepheids exhibits a controversial
nonlinear feature with a break period at 10 days. Therefore, the aim of this
Research Note is to test the linearity/nonlinearity of the PL relations for the
LMC Cepheids in BVIcJHKs band, as well as in the Wesenheit functions. We show
that simply comparing the long and short period slopes, together with their
associate d standard deviations, leads to a strictly larger error rate than
applying rigorous statistical tests such as the F-test. We applied various
statistical tests to the current published LMC Cepheid data. These statistical
tests include the F-test, the testimator test, and the Schwarz information
criterion (SIC) method. The results from these statistical tests strongly
suggest that the LMC PL relation is nonlinear in BVIcJH band but linear in the
Ks band and in the Wesenheit functions. Using the properties of period-color
relations at maximum light and multi-phase relations, we believe that the
nonlinear PL relation is not caused by extinction errors.Comment: 6 pages, 5 figures and 2 tables, A&A accepte
Poverty Effects of the Minimum Wage: The Role of Household Employment Composition
sector employment, uncovered sector employment, and unemployment. The impact of these labor market adjustments on absolute poverty will depend on how the pattern of employment composition changes within households and on how income is shared within households. An earlier paper (Fields and Kanbur, 2007) focused on the income-sharing dimension of the problem. The present paper focuses on household employment composition. For a particular structure of the labor marketβ one with good jobs, bad jobs, unemployment, and adult and youth workersβ and with a particular model of how the sectoral patterns of employment are translated into household employment composition, we analyze the impact of minimum wages on a class of absolute poverty measures. The precise characterizations demonstrate the need for a nuanced appreciation of the impacts of a minimum wage increase, since they depend intricately on the values of key parameters (the poverty line, poverty aversion, labor demand elasticity, and the starting level of the minimum wage). Moreover, the relationship between poverty and the minimum wage is in general nonmonotonic, so that local effects can be quite different from the effects of large changes in the minimum wage.Minimum wage, poverty, labor market, Financial Economics, Food Security and Poverty, Labor and Human Capital,
Semi-Empirical Cepheid Period-Luminosity Relations in Sloan Magnitudes
In this paper we derive semi-empirical Cepheid period-luminosity (P-L)
relations in the Sloan ugriz magnitudes by combining the observed BVI mean
magnitudes from the Large Magellanic Cloud Cepheids (LMC) and theoretical
bolometric corrections. We also constructed empirical gr band P-L relations,
using the publicly available Johnson-Sloan photometric transformations, to be
compared with our semi-empirical P-L relations. These two sets of P-L relations
are consistent with each other.Comment: 4 pages, 2 tables and 2 figures, ApJ accepte
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