32 research outputs found
Extended Stromgren Photoelectric Photometry in NGC 752
Photoelectric photometry on the extended Stromgren system (uvbyCa) is
presented for 7 giants and 21 main sequence stars in the old open cluster, NGC
752. Analysis of the hk data for the turnoff stars yields a new determination
of the cluster mean metallicity. From 10 single-star members, [Fe/H] = -0.06
+/- 0.03, where the error quoted is the standard error of the mean and the
Hyades abundance is set at [Fe/H] = +0.12. This result is unchanged if all 20
stars within the limits of the hk metallicity calibration are included. The
derived [Fe/H] is in excellent agreement with past estimates using
properly-zeroed m1 data, transformed moderate-dispersion spectroscopy, and
recent high dispersion spectroscopy.Comment: 14 tex'd pages including 2 tables; 2 separate files with eps figures
Accepted for PASP March 200
A UBVI and uvbyCaHbeta Analysis of the Intermediate-Age Open Cluster, NGC 5822
NGC 5822 is a richly populated, moderately nearby, intermediate-age open
cluster covering an area larger than the full moon on the sky. A CCD survey of
the cluster on the UBVI and uvbyCaHbeta systems shows that the cluster is
superposed upon a heavily reddened field of background stars with E(B-V) > 0.35
mag, while the cluster has small and uniform reddening at E(b-y) = 0.075 +/-
0.008 mag or E(B-V) = 0.103 +/- 0.011 mag, based upon 48 and 61 probable A and
F dwarf single-star members, respectively. The errors quoted include both
internal photometric precision and external photometric uncertainties. The
metallicity derived from 61 probable single F-star members is [Fe/H] = -0.058
+/- 0.027 (sem) from m_1 and 0.010 +/- 0.020 (sem) from hk, for a weighted
average of [Fe/H] = -0.019 +/- 0.023, where the errors refer to the internal
errors from the photometry alone. With reddening and metallicity fixed, the
cluster age and apparent distance modulus are obtained through a comparison to
appropriate isochrones in both VI and BV, producing 0.9 +/- 0.1 Gyr and 9.85
+/- 0.15, respectively. The giant branch remains dominated by two distinct
clumps of stars, though the brighter clump seems a better match to the
core-He-burning phase while the fainter clump straddles the first-ascent red
giant branch. Four potential new clump members have been identified, equally
split between the two groups. Reanalysis of the UBV two-color data extending
well down the main sequence shows it to be optimally matched by reddening near
E(B-V) = 0.10 rather than the older value of 0.15, leading to [Fe/H] between
-0.16 and 0.00 from the ultraviolet excess of the unevolved dwarfs. The impact
of the lower reddening and younger age of the cluster on previous analyses of
the cluster is discussed.Comment: 20 figures and 5 tables (portions of data tables 3 and 5 only
vbyCaHbeta CCD Photometry of Clusters. VIII. The Super-Metal Rich, Old Open Cluster NGC 6791
CCD photometry on the intermediate-band vbyCaHbeta system is presented for
the metal-rich, old open cluster, NGC 6791. Preliminary analysis led to [Fe/H]
above +0.4 with an anomalously high reddening and an age below 5 Gyr. A revised
calibration between (b-y)_0 and [Fe/H] at a given temperature shows that the
traditional color-metallicity relations underestimate the color of the turnoff
stars at high metallicity. With the revised relation, the metallicity from hk
and the reddening for NGC 6791 become [Fe/H] = +0.45 +/- 0.04 and E(b-y) =
0.113 +/- 0.012 or E(B-V) = 0.155 +/- 0.016. Using the same technique,
reanalysis of the photometry for NGC 6253 produces [Fe/H] = +0.58 +/-0.04 and
E(b-y) = 0.120 +/- 0.018 or E(B-V) = 0.160 +/- 0.025. The errors quoted include
both the internal and external errors. For NGC 6791, the metallicity from m_1
is a factor of two below that from hk, a result that may be coupled to the
consistently low metal abundance from DDO photometry of the cluster and the
C-deficiency found from high dispersion spectroscopy. E(B-V) is the same value
predicted from Galactic reddening maps. With E(B-V) = 0.15 and [Fe/H] = +0.45,
the available isochrones predict an age of 7.0 +/- 1.0 Gyr and an apparent
modulus of (m-M) = 13.60 +/- 0.15, with the dominant source of the uncertainty
arising from inconsistencies among the isochrones. The reanalysis of NGC 6253
with the revised lower reddening confirms that on both the hk and m_1
metallicity scales, NGC 6253, while less than half the age of NGC 6791, remains
at least as metal-rich as NGC 6791, if not richer.Comment: Accepted for Astronomical Journal. 42 p. latex file includes 11
figures and 3 tables, one of which is a short version of a data table to
appear in online AJ in its entiret
vbyCaHbeta CCD Photometry of Clusters. VI. The Metal-Deficient Open Cluster NGC 2420
CCD photometry on the intermediate-band vbyCaHbeta system is presented for
the metal-deficient open cluster, NGC 2420. Restricting the data to probable
single members of the cluster using the CMD and the photometric indices alone
generates a sample of 106 stars at the cluster turnoff. The average E(b-y) =
0.03 +/- 0.003 (s.e.m.) or E(B-V) = 0.050 +/- 0.004 (s.e.m.), where the errors
refer to internal errors alone. With this reddening, [Fe/H] is derived from
both m1 and hk, using b-y and Hbeta as the temperature index. The agreement
among the four approaches is reasonable, leading to a final weighted average of
[Fe/H] = -0.37 +/- 0.05 (s.e.m.) for the cluster, on a scale where the Hyades
has [Fe/H] = +0.12. When combined with the abundances from DDO photometry and
from recalibrated low-resolution spectroscopy, the mean metallicity becomes
[Fe/H] = -0.32 +/- 0.03. It is also demonstrated that the average cluster
abundances based upon either DDO data or low-resolution spectroscopy are
consistently reliable to 0.05 dex or better, contrary to published attempts to
establish an open cluster metallicity scale using simplistic offset corrections
among different surveys.Comment: scheduled for Jan. 2006 AJ; 33 pages, latex, includes 7 figures and 2
table
Lithium in the Intermediate-Age Open Cluster, NGC 3680
High-dispersion spectra centered on the Li 6708 A line have been obtained for
70 potential members of the open cluster NGC 3680, with an emphasis on stars in
the turnoff region. A measurable Li abundance has been derived for 53 stars, 39
of which have radial velocities and proper motions consistent with cluster
membership. After being transferred to common temperature and abundance scales,
previous Li estimates have been combined to generate a sample of 49 members, 40
of which bracket the cluster Li-dip. Spectroscopic elemental analysis of 8
giants and 5 turnoff stars produces [Fe/H] = -0.17 +/- 0.07 (sd) and -0.07 +/-
0.02 (sd), respectively. We also report measurements of Ca, Si and Ni which are
consistent with scaled-solar ratios within the errors. Adopting [Fe/H] = -0.08
(Sect. 3.6), Y^2 isochrone comparisons lead to an age of 1.75 +/- 0.10 Gyr and
an apparent modulus of (m-M) = 10.30 +/- 0.15 for the cluster, placing the
center of the Li-dip at 1.35 +/- 0.03 solar masses. Among the giants, 5 of 9
cluster members are now known to have measurable Li with A(Li) near 1.0. A
combined sample of dwarfs in the Hyades and Praesepe is used to delineate the
Li-dip profile at 0.7 Gyr and [Fe/H] = +0.15, establishing its center at 1.42
+/- 0.02 solar masses and noting the possible existence of secondary dip on its
red boundary. When evolved to the typical age of the clusters NGC 752, IC 4651
and NGC 3680, the Hyades/Praesepe Li-dip profile reproduces the observed
morphology of the combined Li-dip within the CMD's of the intermediate-age
clusters while implying a metallicity dependence for the central mass of the
Li-dip given by Mass = (1.38 +/-0.04) + (0.4 +/- 0.2)[Fe/H]. The implications
of the similarity of the Li-dichotomy among giants in NGC 752 and IC 4651 and
the disagreement with the pattern among NGC 3680 giants are discussed.Comment: Latex ms. is 56 pages, including 10 figures and 4 tables. Accepted
for the Astronomical Journa
uvbyCaHbeta CCD Photometry of Clusters. V. The Metal-Deficient Open Cluster NGC 2243
CCD photometry on the intermediate-band uvbyCaHbeta system is presented for
the metal-deficient open cluster, NGC 2243. Restricting the data to probable
single members of the cluster using the CMD and the photometric indices alone
generates a sample of 100 stars at the cluster turnoff. The average E(b-y) =
0.039 (0.003 s.e.m.) or E(B-V) = 0.055 (0.004 s.e.m.), where the errors refer
to internal errors alone. With this reddening, [Fe/H] is derived from both m_1
and hk, using b-y and Hbeta as the temperature index. The agreement among the
four approaches is excellent, leading to a final weighted average of [Fe/H] =
-0.57 (0.03 s.e.m.) for the cluster, on a scale where the Hyades has [Fe/H] =
+0.12. Using a combination of photometric and spectroscopic data, 27 probable
cluster members are identified and used to delineate the red giant branch and a
well-defined clump at V = 13.70, while eliminating the so-called second clump
at V = 14.1. Interpolation between isochrones of appropriate [Fe/H] leads to an
apparent modulus of (m-M) = 13.15 +/- 0.1 and an age of 3.8 +/- 0.2 Gyr. A
differential CMD comparison with Berkeley 29, a cluster with a galactocentric
distance almost twice that of NGC 2243, constrains Berkeley 29 to be at least
as young and as metal-rich as NGC 2243.Comment: 21 pg postscript, latex to preprint format, 15 eps figures, 2 tables.
Accepted for publication in the Astronomical Journal Feb. 200
WIYN Open Cluster Study. XXXIX. Abundances in NGC 6253 from HYDRA Spectroscopy of the Li 6708 A Region
High-dispersion spectra of 89 potential members of the old, super-metal-rich
open cluster, NGC 6253, have been obtained with the HYDRA multi-object
spectrograph. Based upon radial-velocity measurements alone, 47 stars at the
turnoff of the cluster color-magnitude diagram (CMD) and 18 giants are
identified as potential members. Five turnoff stars exhibit evidence of
binarity while proper-motion data eliminates two of the dwarfs as members. The
mean cluster radial velocity from probable single-star members is -29.4 +/- 1.3
km/sec (sd). A discussion of the current estimates for the cluster reddening,
derived independently of potential issues with the BV cluster photometry, lead
to an adopted reddening of E(B-V) = 0.22 +/- 0.04. From equivalent width
analyses of 38 probable single-star members near the CMD turnoff, the weighted
average abundances are found to be [Fe/H] = +0.43 +/- 0.01, [Ni/H] = +0.53 +/-
0.02 and [Si/H] = +0.43 (+0.03,-0.04), where the errors refer to the standard
errors of the weighted mean. Weak evidence is found for a possible decline in
metallicity with increasing luminosity among stars at the turnoff. We discuss
the possibility that our turnoff stars have been affected by microscopic
diffusion. For 15 probable single-star members among the giants, spectrum
synthesis leads to abundances of +0.46 (+0.02,-0.03) for [Fe/H]. While less
than half the age of NGC 6791, NGC 6253 is at least as metal-rich and, within
the uncertainties, exhibits the same general abundance pattern as that typified
by super-metal-rich dwarfs of the galactic bulge.Comment: 5 Tables, 9 figures, 45 page
Assessment of variation in immunosuppressive pathway genes reveals TGFBR2 to be associated with risk of clear cell ovarian cancer.
BACKGROUND: Regulatory T (Treg) cells, a subset of CD4+ T lymphocytes, are mediators of immunosuppression in cancer, and, thus, variants in genes encoding Treg cell immune molecules could be associated with ovarian cancer. METHODS: In a population of 15,596 epithelial ovarian cancer (EOC) cases and 23,236 controls, we measured genetic associations of 1,351 SNPs in Treg cell pathway genes with odds of ovarian cancer and tested pathway and gene-level associations, overall and by histotype, for the 25 genes, using the admixture likelihood (AML) method. The most significant single SNP associations were tested for correlation with expression levels in 44 ovarian cancer patients. RESULTS: The most significant global associations for all genes in the pathway were seen in endometrioid ( p = 0.082) and clear cell ( p = 0.083), with the most significant gene level association seen with TGFBR2 ( p = 0.001) and clear cell EOC. Gene associations with histotypes at p < 0.05 included: IL12 ( p = 0.005 and p = 0.008, serous and high-grade serous, respectively), IL8RA ( p = 0.035, endometrioid and mucinous), LGALS1 ( p = 0.03, mucinous), STAT5B ( p = 0.022, clear cell), TGFBR1 ( p = 0.021 endometrioid) and TGFBR2 ( p = 0.017 and p = 0.025, endometrioid and mucinous, respectively). CONCLUSIONS: Common inherited gene variation in Treg cell pathways shows some evidence of germline genetic contribution to odds of EOC that varies by histologic subtype and may be associated with mRNA expression of immune-complex receptor in EOC patients
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Recreational physical inactivity and mortality in women with invasive epithelial ovarian cancer: evidence from the Ovarian Cancer Association Consortium
Background: Little is known about modifiable behaviours that may be associated with epithelial ovarian cancer (EOC) survival. We conducted a pooled analysis of 12 studies from the Ovarian Cancer Association Consortium to investigate the association between pre-diagnostic physical inactivity and mortality. Methods: Participants included 6806 women with a primary diagnosis of invasive EOC. In accordance with the Physical Activity Guidelines for Americans, women reporting no regular, weekly recreational physical activity were classified as inactive. We utilised Cox proportional hazard models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) representing the associations of inactivity with mortality censored at 5 years. Results: In multivariate analysis, inactive women had significantly higher mortality risks, with (HR=1.34, 95% CI: 1.18â1.52) and without (HR=1.22, 95% CI: 1.12â1.33) further adjustment for residual disease, respectively. Conclusion: In this large pooled analysis, lack of recreational physical activity was associated with increased mortality among women with invasive EOC