1,717 research outputs found
Discovery of > 200 RR Lyrae Variables in M62: An Oosterhoff I Globular Cluster with a Predominantly Blue HB
We report on the discovery of a large number of RR Lyrae variable stars in
the moderately metal-rich Galactic globular cluster M62 (NGC 6266), which
places it among the top three most RR Lyrae-rich globular clusters known.
Likely members of the cluster in our studied field, from our preliminary number
counts, include about 130 fundamental-mode (RRab) pulsators, with =
0.548 d, and about 75 first-overtone (RRc) pulsators, with = 0.300 d.
The average periods and the position of the RRab variables with well-defined
light curves in the Bailey diagram both suggest that the cluster is of
Oosterhoff type I. However, the morphology of the cluster's horizontal branch
(HB) is strikingly similar to that of the Oosterhoff type II globular cluster
M15 (NGC 7078), with a dominant blue HB component and a very extended blue
tail. Since M15 and M62 differ in metallicity by about one dex, we conclude
that metallicity, at a fixed HB type, is a key parameter determining the
Oosterhoff status of a globular cluster and the position of its variables in
the Bailey diagram.Comment: 5 pages, 4 figures. ApJ Letters, in pres
The Dwarf Spheroidal Companions to M31: Variable Stars in Andromeda VI
We have surveyed Andromeda VI, a dwarf spheroidal galaxy companion to M31,
for variable stars using F450W and F555W observations obtained with the Hubble
Space Telescope. A total of 118 variables were found, with 111 being RR Lyrae,
6 anomalous Cepheids, and 1 variable we were unable to classify. We find that
the Andromeda VI anomalous Cepheids have properties consistent with those of
anomalous Cepheids in other dwarf spheroidal galaxies. We revise the existing
period-luminosity relations for these variables. Further, using these and other
available data, we show that there is no clear difference between fundamental
and first-overtone anomalous Cepheids in a period-amplitude diagram at shorter
periods, unlike the RR Lyrae. For the Andromeda VI RR Lyrae, we find that they
lie close to the Oosterhoff type I Galactic globular clusters in the
period-amplitude diagram, although the mean period of the RRab stars, =
0.588 d, is slightly longer than the typical Oosterhoff type I cluster. The
mean V magnitude of the RR Lyrae in Andromeda VI is 25.29+/-0.03, resulting in
a distance 815+/-25 kpc on the Lee, Demarque, & Zinn distance scale. This is
consistent with the distance derived from the I magnitude of the tip of the red
giant branch. Similarly, the properties of the RR Lyrae indicate a mean
abundance for Andromeda VI which is consistent with that derived from the mean
red giant branch color.Comment: 23 pages, including 13 figures and 6 tables, emulateapj5/apjfonts
style. Accepted by the Astronomical Journal. We recommend the interested
reader to download the preprint with full-resolution figures, which can be
found at http://www.noao.edu/noao/staff/pritzl/M31dwarfs.htm
Ground state cooling, quantum state engineering and study of decoherence of ions in Paul traps
We investigate single ions of in Paul traps for quantum
information processing. Superpositions of the S electronic ground state
and the metastable D state are used to implement a qubit. Laser light
on the S D transition is used for the
manipulation of the ion's quantum state. We apply sideband cooling to the ion
and reach the ground state of vibration with up to 99.9% probability. Starting
from this Fock state , we demonstrate coherent quantum state
manipulation. A large number of Rabi oscillations and a ms-coherence time is
observed. Motional heating is measured to be as low as one vibrational quantum
in 190 ms. We also report on ground state cooling of two ions.Comment: 12 pages, 6 figures. submitted to Journal of Modern Optics, Special
Issue on Quantum Optics: Kuehtai 200
An assessment of validity and responsiveness of generic measures of health-related quality of life in hearing impairment
This article is made available through the Brunel Open Access Publishing Fund. This article is distributed under the terms of the
Creative Commons Attribution License which permits any use, distribution,
and reproduction in any medium, provided the original
author(s) and the source are credited.Purpose: This review examines psychometric performance of three widely used generic preference-based measures, that is, EuroQol 5 dimensions (EQ-5D), Health Utility Index 3 (HUI3) and Short-form 6 dimensions (SF-6D) in patients with hearing impairments.
Methods: A systematic search was undertaken to identify studies of patients with hearing impairments where health state utility values were measured and reported. Data were extracted and analysed to assess the reliability, validity (known group differences and convergent validity) and responsiveness of the measures across hearing impairments.
Results: Fourteen studies (18 papers) were included in the review. HUI3 was the most commonly used utility measures in hearing impairment. In all six studies, the HUI3 detected difference between groups defined by the severity of impairment, and four out of five studies detected statistically significant changes as a result of intervention. The only study available suggested that EQ-5D only had weak ability to discriminate difference between severity groups, and in four out of five studies, EQ-5D failed to detected changes. Only one study involved the SF-6D; thus, the information is too limited to conclude on its performance. Also evidence for the reliability of these measures was not found.
Conclusion: Overall, the validity and responsiveness of the HUI3 in hearing impairment was good. The responsiveness of EQ-5D was relatively poor and weak validity was suggested by limited evidence. The evidence on SF-6D was too limited to make any judgment. More head-to-head comparisons of these and other preference measures of health are required.Medical Research Counci
Maternal Condition Does Not Influence Birth Sex Ratios in Anubis Baboons (Papio anubis)
Trivers and Willard predicted that when parental condition has differential effects on the fitness of male and female offspring, parents who are in good condition will bias investment toward the sex that benefits most from additional investment. Efforts to test predictions derived from Trivers and Willard's model have had mixed results, perhaps because most studies have relied on proxy measures of parental condition, such as dominance rank. Here, we examine the effects of female baboons condition on birth sex ratios and post-natal investment, based on visual assessments of maternal body condition. We find that local environmental conditions have significant effects on female condition, but maternal condition at conception has no consistent relationship with birth sex ratios. Mothers who are in poorer condition at the time of conception resume cycling significantly later than females who are in better condition, but the sex of their infants has no effect on the time to resumption of cycling. Thus, our findings provide strong evidence that maternal condition influences females' ability to reproduce, but females do not facultatively adjust the sex ratio of their offspring in relation to their dominance rank or current condition
Variable stars in the Fornax dSph Galaxy. I. The Globular Cluster Fornax 4
Variable stars have been identified for the first time in Fornax 4, the
globular cluster located near the center of the Fornax dwarf spheroidal galaxy.
By applying the image subtraction technique to B,V time series photometry
obtained with the MagIC camera of the 6.5-m Magellan/Clay telescope and with
the wide field imager of the 4-m Blanco/CTIO telescope, we detected 27 RR Lyrae
stars (22 fundamental mode, 3 first overtone, and 2 double-mode pulsators) in a
2.4'x2.4' area centered on Fornax 4. The average and minimum periods of the
ab-type RR Lyrae stars, = 0.594 d and P(ab,min)=0.5191 d, respectively, as
well as the revised position of the cluster in the horizontal branch
type--metallicity plane, all consistently point to an Oosterhoff-intermediate
status for the cluster, unlike what is seen for the vast majority of Galactic
globular clusters, but in agreement with previous indications for the other
globular clusters in Fornax.
The average apparent magnitude of the RR Lyrae stars located within 30 arcsec
from the cluster center is =21.43 +/- 0.03 mag (sigma=0.10 mag, average
on 12 stars), leading to a true distance modulus of (m-M)o=20.64 +/- 0.09 mag
or (m-M)o=20.53 +/- 0.09 mag, depending on whether a low ([Fe/H]=-2.0) or a
moderately high ([Fe/H]=-1.5) metallicity is adopted.Comment: Apj, in pres
HST Snaphot Study of Variable Stars in Globular Clusters: Inner Region of NGC 6441
[Abridged] We present the results of a Hubble Space Telescope snapshot
program to survey the inner region of the globular cluster NGC 6441 for its
variable stars. A total of 57 variable stars was found including 38 RR Lyrae
stars, 6 Population II Cepheids, and 12 long period variables. Of the RR Lyrae
stars observed in this survey, 26 are pulsating in the fundamental mode with a
mean period of 0.753d and 12 are first-overtone mode pulsators with a mean
period of 0.365d. These values match up very well with those found in
ground-based surveys. Combining all the available data for NGC 6441, we find
mean periods of 0.759d and 0.375d for the RRab and RRc stars, respectively. We
also find that the RR Lyrae in this survey are located in the same regions of a
period-amplitude diagram as those found in ground-based surveys. Although NGC
6441 is a metal-rich globular cluster, its RR Lyrae more closely resemble those
in Oosterhoff type II globular clusters. However, even compared to typical
Oosterhoff type II systems, the mean period of its RRab stars is unusually
long. We also derived I-band period-luminosity relations for the RR Lyrae
stars. Of the six Population II Cepheids, five are of W Virginis type and one
is a BL Herculis variable stars. This makes NGC 6441, along with NGC 6388, the
most metal-rich globular cluster known to contain these types of variable
stars. Another variable, V118, may also be a Population II Cepheid given its
long period and its separation in magnitude from the RR Lyrae stars. We argue
that there does not appear to be a change in the period-luminosity relation
slope between the BL Herculis and W Virginis stars, but that a change of slope
does occur when the RV Tauri stars are added to the period-luminosity relation.Comment: 28 pages, including 9 figures and 8 tables, emulateapj5/apjfonts
style. Accepted by the Astronomical Journal. Approximate publication date
September 2003. We recommend the interested reader to download the preprint
with full-resolution figures, which can be found at
http://www.astro.puc.cl/~mcatelan/Pritzl.zi
Spontaneous emission of an atom in front of a mirror
Motivated by a recent experiment [J. Eschner {\it et al.}, Nature {\bf 413},
495 (2001)], we now present a theoretical study on the fluorescence of an atom
in front of a mirror. On the assumption that the presence of the distant mirror
and a lens imposes boundary conditions on the electric field in a plane close
to the atom, we derive the intensities of the emitted light as a function of an
effective atom-mirror distance. The results obtained are in good agreement with
the experimental findings.Comment: 8 pages, 6 figures, revised version, references adde
On the newly discovered Canes Venatici II dSph galaxy
We report on the detection of variable stars in the Canes Venatici II (CVn
II) dwarf spheroidal galaxy, a new satellite of the Milky Way recently
discovered by the Sloan Digital Sky Survey. We also present a V, B-V
color-magnitude diagram that reaches V = 25.5 mag, showing the galaxy's main
sequence turn off at V = 24.5 mag and revealing several candidate blue
straggler stars. Two RR Lyrae stars have been identified within the half-light
radius of CVn II,a fundamental-mode variable (RRab) with period P_ab = 0.743
days, and a first-overtone (RRc) RR Lyrae star with P_c = 0.358 days. The
rather long periods of these variables along with their position on the
period-amplitude diagram support an Oosterhoff type II classification for CVn
II. The average apparent magnitude of the RR Lyrae stars, = 21.48 +/- 0.02
mag, is used to obtain a precision distance modulus of mu_0 = 21.02 +/- 0.06
mag and a corresponding distance of 160(+4,-5} kpc, for an adopted reddening
E(B-V) = 0.015 mag.Comment: Submitted to ApJ Letter
Sensitivity to Gravitational Waves from Compact Binary Coalescences Achieved during LIGO's Fifth and Virgo's First Science Run
We summarize the sensitivity achieved by the LIGO and Virgo gravitational
wave detectors for compact binary coalescence (CBC) searches during LIGO's
fifth science run and Virgo's first science run. We present noise spectral
density curves for each of the four detectors that operated during these
science runs which are representative of the typical performance achieved by
the detectors for CBC searches. These spectra are intended for release to the
public as a summary of detector performance for CBC searches during these
science runs.Comment: 12 pages, 5 figure
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