1,621 research outputs found
Comprehensive study of Leon-Queretaro area
There are no author-identified significant results in this report
CN Variations in High Metallicity Globular and Open Clusters
We present a comparison of CN bandstrength variations in the high-metallicity
globular clusters NGC 6356 and NGC 6528 with those measured in the old open
clusters NGC 188, NCG 2158 and NGC 7789. Star-to-star abundance variations, of
which CN differences are a readily observable sign, are commonplace in
moderate-metallicity halo globular clusters but are unseen in the field or in
open clusters. We find that the open clusters have narrow, unimodal
distributions of CN bandstrength, as expected from the literature, while the
globular clusters have broad, bimodal distributions of CN bandstrength, similar
to moderate-metallicity halo globular clusters. This result has interesting
implications for the various mechanisms proposed to explain the origin of
globular cluster abundance inhomogeneities, and suggests that the local
environment at the epoch of cluster formation plays a vital role in regulating
intracluster enrichment processes.Comment: 6 pages, emulateapj format, PASP in pres
Binary open clusters in the Milky Way: photometric and spectroscopic analysis of NGC 5617 and Trumpler 22
Using photometry and high resolution spectroscopy we investigate for the
first time the physical connection between the open clusters NGC 5617 and
Trumpler 22. Based on new CCD photometry we report their spatial proximity and
common age of ~70 Myr. Based on high resolution spectra collected using the
HERMES and UCLES spectrographs on the Anglo-Australian telescope, we present
radial velocities and abundances for Fe, Na, Mg, Al, Si, Ca and Ni. The
measured radial velocities are -38.63 +/-2.25 km/s for NGC 5617 and -38.46
+/-2.08 km/s for Trumpler 22. The mean metallicity of NGC 5617 was found to be
[Fe/H] =-0.18 +/-0.02 and for Trumpler 22 was found to be [Fe/H] = -0.17
+/-0.04. The two clusters share similar abundances across the other elements,
indicative of a common chemical enrichment history of these clusters. Together
with common motions and ages we confirm that NGC 5617 and Trumpler 22 are a
primordial binary cluster pair in the Milky Way.Comment: 7 pages, 3 figure, accepted by MNRA
Light-Element Abundance Variations at Low Metallicity: the Globular Cluster NGC 5466
We present low-resolution (R~850) spectra for 67 asymptotic giant branch
(AGB), horizontal branch and red giant branch (RGB) stars in the
low-metallicity globular cluster NGC 5466, taken with the VIRUS-P
integral-field spectrograph at the 2.7-m Harlan J. Smith telescope at McDonald
Observatory. Sixty-six stars are confirmed, and one rejected, as cluster
members based on radial velocity, which we measure to an accuracy of 16 km s-1
via template-matching techniques. CN and CH band strengths have been measured
for 29 RGB and AGB stars in NGC 5466, and the band strength indices measured
from VIRUS-P data show close agreement with those measured from Keck/LRIS
spectra previously taken of five of our target stars. We also determine carbon
abundances from comparisons with synthetic spectra. The RGB stars in our data
set cover a range in absolute V magnitude from +2 to -3, which permits us to
study the rate of carbon depletion on the giant branch as well as the point of
its onset. The data show a clear decline in carbon abundance with rising
luminosity above the luminosity function "bump" on the giant branch, and also a
subdued range in CN band strength, suggesting ongoing internal mixing in
individual stars but minor or no primordial star-to-star variation in
light-element abundances.Comment: 10 pages, emulateapj format, AJ accepte
CN Bimodality at Low Metallicity: The Globular Cluster M53
We present low resolution UV-blue spectroscopic observations of red giant
stars in the globular cluster M53 ([Fe/H]=-1.84), obtained to study primordial
abundance variations and deep mixing via the CN and CH absorption bands. The
metallicity of M53 makes it an attractive target: a bimodal distribution of
3883 angstrom CN bandstrength is common in moderate- and high-metallicity
globular clusters ([Fe/H] > -1.6) but unusual in those of lower metallicity
([Fe/H] < -2.0). We find that M53 is an intermediate case, and has a broad but
not strongly bimodal distribution of CN bandstrength, with CN and CH
bandstrengths anticorrelated in the less-evolved stars. Like many other
globular clusters, M53 also exhibits a general decline in CH bandstrength and
[C/Fe] abundance with rising luminosity on the red giant branch.Comment: 8 pages including 11 figures and 1 table, accepted by PAS
Comprehensive study of Leon-Queretaro area
There are no author-identified significant results in this report
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