8,951 research outputs found
Panchromatic fits to the Globular Cluster NGC 6366
We present panchromatic isochrone fits to the color magnitude data of the
globular cluster NGC 6366, based on HST ACS/WFC and SOAR photometric data.
Before performing the isochrone fits, we corrected the photometric data for
differential reddening and calculated the mean ridge line of the color
magnitude diagrams. We compared the isochrones of Dartmouth Stellar Evolution
Database and PAdova and TRieste Stellar Evolution Code (with microscopic
diffusion starting on the main sequence). Based on previous determinations of
the metallicity of this cluster we test it from [Fe/H]=-1.00 to [Fe/H]= -0.50,
and the age from 9 to 13 Gyrs. The uncertainties do not decrease when we fit
simultaneous colors. We also find that the Dartmouth Stellar Evolution Database
isochrones have a better fit in the sub giant branch and low main sequence than
the PAdova and TRieste Stellar Evolution Code. Considering the most recent
spectroscopic determination of the metallicity ([Fe/H]= -0.67), we find
E(B-V)=0.69+/-0.02, (m-M)_V=15.02+/-0.07 and 11+/-2 Gyr for NGC 6366.Comment: 4 pages, 2 figures. Proceedings of the conference "Reading the book
of globular clusters with the lens of stellar evolution", to be published in
Memorie della Societ\'a Astronomica Italian
The age-metallicity dependence for white dwarfs
We present a theoretical study on the metallicity dependence of the
initialtofinal mass relation and its influence on white dwarf age
determinations. We compute a grid of evolutionary sequences from the main
sequence to K on the white dwarf cooling curve, passing through
all intermediate stages. During the thermally-pulsing asymptotic giant branch
no third dredge-up episodes are considered and thus the photospheric C/O ratio
is below unity for sequences with metallicities larger than . We
consider initial metallicities from to , accounting for
stellar populations in the galactic disk and halo, with initial masses below
. We found a clear dependence of the shape of the
initialtofinal mass relation with the progenitor metallicity, where metal
rich progenitors result in less massive white dwarf remnants, due to an
enhancement of the mass loss rates associated to high metallicity values. By
comparing our theoretical computations with semi empirical data from globular
and old open clusters, we found that the observed intrinsic mass spread can be
accounted for by a set of initialtofinal mass relations characterized by
different metallicity values. Also, we confirm that the lifetime spent before
the white dwarf stage increases with metallicity. Finally, we estimate the mean
mass at the top of the white dwarf cooling curve for three globular clusters
NGC 6397, M4 and 47 Tuc, around , characteristic of old stellar
populations. However, we found different values for the progenitor mass, lower
for the metal poor cluster, NGC 6397, and larger for the younger and metal rich
cluster 47 Tuc, as expected from the metallicity dependence of the
initialtofinal mass relation.Comment: Accepted for publication in MNRA
Multichromatic colour-magnitude diagrams of the globular cluster NGC 6366
We present multichromatic isochrone fits to the colour-magnitude data of the
globular cluster NGC 6366, based on Hubble Space Telescope Advanced Camera for
Surveys/Wide Field Channel and Southern Astrophysical Research photometric
data. We corrected the photometric data for differential reddening and
calculated the mean ridge line of the colour-magnitude diagrams. We compared
the isochrones of Dartmouth Stellar Evolution Database and PAdova and TRieste
Stellar Evolution Code both with microscopic diffusion starting on the main
sequence. Bracketing all previous determinations of this cluster, we tested
metallicities from [Fe/H]=-1.00 to [Fe/H]=-0.50, and ages from 9 to 13 Gyr.
After determining the total to selective extinction ratio only from stars
belonging to this cluster, R_V=3.06+/-0.14, we found the parameters for this
cluster to be E(B-V)=0.69+/-0.02(int)+/-0.04(ext),
(m-M)_V=15.02+/-0.07(int)+/-0.13(ext), Age=11+/-1.15 Gyr. Evolutionary models
fail to reproduce the low-Teff sequence in multiband colour-magnitude diagrams,
indicating that they still have an incomplete physics. We found that the
Dartmouth Stellar Evolution Database isochrones better fit the subgiant branch
and low main sequence than the PAdova and TRieste Stellar Evolution Code.Comment: 9 pages, 5 figure
Teenage Pregnancy in Mexico: Evolution and Consequences
We analyze the consequences of a teenage pregnancy event in the short- and long-run in Mexico. Using longitudinal and cross-section data, we match females who got pregnant and those that did not based on a propensity score. Several balancing tests and specifications indicate that the main assumptions to estimate the average treatment effect on the treated using a propensity score are satisfied. In the short-run, we find that a teenage pregnancy causes a decrease of 0.6-0.8 years of schooling, lower attendance to school, less hours of work and a higher marriage rate. At the household level, we do not find any effect in parental hours of work or income per capita. In the long-run, we find a loss in years of education of 1-1.2 and a higher probability of being married, but also higher probability of being separated or divorced. We also find that household income per capita is lower at least in the long-run.teenage, pregnancy, labor outcomes, propensity score, matching
Labor supply of married women in Mexico: 1990-2000
In the last couple of decades, and in particular during the last couple of administrations, the Mexican government has implemented various social programs targeted specifically to women, such as PROGRESA/Oportunidades, a child care program, and a gender equality program (PROIGUALDAD). The impact that those programs may have on the work behavior of women largely depends on the form that the female labor supply takes, and in particular, on the labor supply elasticities with respect to own wages, and the husband’s wages. Despite this fact, the literature on female labor supply in Mexico is very scarce. To our knowledge, there is no estimate of the female labor supply elasticities at the national level. This paper fills in this gap in the literature. Using data from the 1990 and 2000 Mexican Census of Population, we estimate a structural model of labor supply through an application of Wooldridge’s (2002) threestep procedure. We …nd that the female labor supply elasticities had a rather sharp decrease between 1990 and 2000, which suggests that women are getting increasingly attached to the labor market. We also find evidence of heterogenous effects for women with young children and women of different cohorts. Even though female are now less responsive to changes in wages, the elasticities that we …nd are still large enough so that social programs aimed at modifying females´ work behavior through incentives might still be very successful.wage inequality, Mexico, labor supply, employment, married women
- …