2,711 research outputs found
Wide-field multi-color photometry of the Galactic globular cluster NGC 1261
(Abriged)This work studies in more detail the stellar population, including
its photometric properties and characteristics, in the rarely studied southern
Galactic globular cluster NGC 1261. We focus on the brighter sequences of the
cluster's color-magnitude diagram (CMD). Like in our previous works, we rely
upon photometry in several passbands to achieve more reliable results and
conclusions. We carried out and analyzed new multi-color photometry of NGC 1261
in UBVI reaching below the turnoff point in all passbands in a fairly extended
cluster field, about 14'x14'. We found several signs of the inhomogeneity
("multiplicity") in the stellar population. The most prominent of them are: (1)
the dependence of the radial distribution of sub-giant branch (SGB) stars in
the cluster on their U magnitude, with brighter stars less centrally
concentrated at the 99.9 \% level than their fainter counterparts; (2) the
dependence of the location of red giant branch (RGB) stars in the U-(U-B) CMD
on their radial distance from the cluster center, with the portion of stars
bluer in the (U-B) color increasing towards the cluster outskirts.
Additionally, the radial variation of the RGB luminosity function in the bump
region is suspected. We assume that both the SGB stars brighter in the U and
the RGB stars bluer in the (U-B) color are probably associated with blue
horizontal branch stars, because of a similarity in their radial distribution
in the cluster. We estimated the metalicity of NGC 1261 from the slope of the
RGB in U-based CMDs and the location of the RGB bump on the branch. These
metallicity indicators give [Fe/H]zw = -1.34 +/- 0.16 dex and [Fe/H]zw = -1.41
+/- 0.10 dex, respectively. We isolated 18 probable blue straggler candidates.
They are more centrally concentrated than the lower red giants of comparable
brightness at the 97.9 \% level.Comment: 8 pages, 9 figures, accepted for publication in A&
The Failure of Peace: Transitional Justice’s Inefficacy in Upholding Victims’ Rights in the Colombian Peace Process
In the interest of ending the 50 year-old internal armed conflict, the Colombian government and FARC-EP advance efforts to reach a peace agreement. The agenda of the Havana talks consists of five issues, one of which is at the heart of achieving peace: the protection of the rights of the conflict’s victims. Nevertheless, what is the cost the victims have to pay to enter the new era of peace? On December 15, 2015, President Juan Manuel Santos and Rodrigo Londoño, leader of the guerrilla force, signed the “Agreement on Victims of the Conflict.” With the implementation of transitional justice, the agreement outlines a set of special conditions that grant amnesty to the perpetrators of crimes considered “less severe.” The agreement’s use of transitional justice interferes with the full satisfaction of the victims’ rights. This paper exposes this failure with an exploration of the conflict’s history emphasizing human rights violations. In addition, it will develop into an analysis of transitional justice, its processes and limitations. Finally, this paper will examine the extent to which the agreement upholds the rights of the victims. In a case as complex as Colombia’s, a peace process and an agreement on victims must acknowledge the harm delivered to the population to create reparations that guarantee justice
Evidence of the inhomogeneity of the stellar population in the differentially reddened globular cluster NGC 3201
We report on evidence of the inhomogeneity (multiplicity) of the stellar
population in the Galactic globular cluster (GC) NGC 3201, which is irregularly
reddened across its face. We carried out a more detailed and careful analysis
of our recently published new multi-color photometry in a wide field of the
cluster with particular emphasis on the U band. Using the photometric data
corrected for differential reddening, we found for the first time two key signs
of the inhomogeneity in the cluster's stellar population and of its radial
variation in the GC. These are (1) an obvious trend in the color-position
diagram, based on the (U-B) color-index, of red giant branch (RGB) stars, which
shows that the farther from the cluster's center, the bluer on average the
(U-B) color of the stars is; and (2) the dependence of the radial distribution
of sub-giant branch (SGB) stars in the cluster on their U magnitude, where
brighter stars are less centrally concentrated than their fainter counterparts
at a confidence level varying between 99.2% and 99.9% depending on the
color-index used to select the stars. The same effects were recently found by
us in the GC NGC 1261. However, contrary to NGC 1261, we are not able to
unambiguously suggest which of the sub-populations of SGB/RGB stars can be the
progenitor of blue and red horizontal branch stars of the cluster. Apart from
M4, NGC 3201 is another GC very probably with an inhomogeneous stellar
population, which has essentially lower mass than the most massive Galactic GCs
where multiple stellar populations were unambiguously detected for the first
timeComment: 5 pages, 4 figure
Cool Stars and Space Weather
Stellar flares, winds and coronal mass ejections form the space weather. They
are signatures of the magnetic activity of cool stars and, since activity
varies with age, mass and rotation, the space weather that extra-solar planets
experience can be very different from the one encountered by the solar system
planets. How do stellar activity and magnetism influence the space weather of
exoplanets orbiting main-sequence stars? How do the environments surrounding
exoplanets differ from those around the planets in our own solar system? How
can the detailed knowledge acquired by the solar system community be applied in
exoplanetary systems? How does space weather affect habitability? These were
questions that were addressed in the splinter session "Cool stars and Space
Weather", that took place on 9 Jun 2014, during the Cool Stars 18 meeting. In
this paper, we present a summary of the contributions made to this session.Comment: Proceedings of the 18th Cambridge Workshop on Cool Stars, Stellar
Systems, and the Sun, Eds G. van Belle & H. Harris, 13 pages, 1 figur
Multi-Color Photometry of the Galactic Globular Cluster M75 = NGC 6864. A New Sensitive Metallicity Indicator and the Position of the Horizontal Branch in UV
We carry out and analyze new multi-color photometry of the Galactic globular
cluster (GC) M75 in UBVI and focus on the brighter sequences of the color-
magnitude diagram (CMD), with particular emphasis on their location in U-based
CMD. Specifically, we study the level both of the horizontal (HB) and red giant
branches (RGB) relative to the main-sequence turnoff (TO) in the U magnitude.
Along with the presented photometry of M75, we use our collection of
photometric data on GCs belonging to the metal-poor range, [Fe/H]zw<-1.1 dex,
obtained from observations with different equipment, but calibrated by standard
stars situated in the observed cluster fields. We confirm our earlier finding,
and extend it to a larger magnitude range.We demonstrate that DeltaU_{TO}^{BHB}
expressing the difference in U magnitude between the TO point and the level of
the blue HB, near its red boundary, of the metal-poor GCs observed with the
EMMI camera of the NTT/ESO telescope is about 0.4-0.5 mag smaller as compared
to GCs observed with the 100" telescope and 1.3 m Warsaw telescope of the Las
Campanas Observatory. At the same time, Delta U_{TO}^{RGB}, the difference in U
magnitude between the TO and RGB inflection (brightest) points, does not show
such an apparent dependence on the characteristics of U filters used, but it
depends on cluster metallicity. We have shown, for the first time, the
dependence of the parameter DeltaU_{TO}^{RGB} on [Fe/H] and have estimated its
analytical expression, by assuming a linear relation between the parameter and
metallicity. Its slope, Delta U_{TO}^{RGB}/Delta [Fe/H]~1.2 mag/dex, is approx.
a factor of two steeper than that of the dependence of the RGB bump position in
the V magnitude on metallicity. The asymptotic giant branch (AGB) clump and
features of the RGB luminosity function (LF) of M75 are also discussed.Comment: 9 pages, 7 figures, accepted for publication in A&
Spatial uncertainty in sap velocity measurements and tree water use upscaling in american beech
4 páginas.-- 3 figuras.-- 10 referencias.-- Póster presentado en el XI Simposio Hispano-Portugués de Relaciones Hídricas en las Plantas, Sevilla 17-20 Sep. (2012)We examined the variation insap velocity radially, azimuthally, at different heights and across different tree sizes for the species Fagus grandifolia. The results demonstrate that the main sources of variability are radial variability and tree size. The implications for scaling up routine point measurements of sap velocity to the whole-tree andstand levels are discussed.This work was funded by the University of New Hampshire. We thank the US Forest Service at BEF and Hubbard Brook for the facilitation of research activities and permission to access sites.N
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