1,646 research outputs found
The Clusters AgeS Experiment (CASE). I. V209 omega Cen - An Eclipsing Post-Common Envelope Binary in the Globular Cluster omega Cen
We use photometric and spectroscopic observations of the detached eclipsing
binary V209 omega Cen to derive the masses, radii, and luminosities of the
component stars. The system exhibits total eclipses and, based on the measured
systemic velocity and the derived distance, is a member of the globular cluster
omega Cen. We obtain 0.945 +/- 0.043 Msun, 0.983 +/- 0.015 Rsun and 6.68 +/-
0.88 Lsun for the cooler, but larger and more luminous primary component. The
secondary component has 0.144 +/- 0.008 Msun, 0.425 +/- 0.008 Rsun and 2.26 +/-
0.28 Lsun. The effective temperatures are estimated at 9370 K for the primary
and at 10866 K for the secondary. On the color-magnitude diagram of the
cluster, the primary component occupies a position between the tip of the blue
straggler region and the extended horizontal branch while the secondary
component is located close to the red border of the area occupied by hot
subdwarfs. However, its radius is too large and its effective temperature is
too low for it to be an sdB star. We propose a scenario leading to the
formation of a system with such unusual properties with the primary component
``re-born'' from a former white dwarf which accreted a new envelope through
mass transfer from its companion. The secondary star has lost most of its
envelope while starting its ascent onto the sub-giant branch. It failed to
ignite helium in its core and is currently powered by a hydrogen burning shell.Comment: 24 pages, 9 figures, AJ, in pres
Hot Subdwarfs in Resolved Binaries
In the last decade or so, there have been numerous searches for hot subdwarfs
in close binaries. There has been little to no attention paid to wide binaries
however. The advantages of understanding these systems can be many. The stars
can be assumed to be coeval, which means they have common properties. The
distance and metallicity, for example, are both unknown for the subdwarf
component, but may be determinable for the secondary, allowing other properties
of the subdwarf to be estimated. With this in mind, we have started a search
for common proper motion pairs containing a hot subdwarf component. We have
uncovered several promising candidate systems, which are presented here.Comment: 6 pages, 4 figures. Proceedings of The Fourth Meeting on Hot Subdwarf
Stars and Related Objects held in China, 20-24 July 2009. Accepted for
publication in Astrophysics and Space Scienc
Intrusion of warm surface water along the Angolan Namibian Coast in February–March 1995: the 1995 Benguela niño
The upper ocean temperatures in the Angolan-Namibian coastal waters were anomalously high during March 1995, with positive temperature anomalies of up to 8°C. Maximum temperature differences were30–50 m deep, reflecting a deepening of the thermocline from normal depths of 10–30 m. The unusually warm water mass covered the Angolan coast from Cabinda (5°S), the northern limit of the survey area, to atleast 24°S off central Namibia. Higher than normal temperatures were observed as far south as Lüderitz (27°S). Satellite-derived SST and direct observations indicated that the seaward distribution of warm waterextended more than 300 km from the coast. Surface drogues released inshore along the central Namibian shelf suggested a maximum southward extension by 3 March 1995. The warm event was associated withobserved mortalities in sardine Sardinops sagax, horse mackerel Trachurus trachurus capensis and kob Argyrosomus inodorus off the coast. It also caused a southward displacement of sardine stocks from Angola,resulting in an increased availability of pelagic fish in Namibian waters. Conditions have occasionally been anomalously warm in Angolan and Namibian waters in the past, with the last major event in 1984. Theseevents are known as Benguela Niños, because of their resemblance to the well known Pacific El Niño. The 1995 Benguela Niño appeared to be associated with a positive subsurface salinity anomaly of 0.5 × 10–3 inNamibian waters and a negative (-4.0 × 10–3) surface salinity anomaly in Angolan waters, thought to be derived from the freshwater input of the Congo River
First Attempt at Spectroscopic Detection of Gravity Modes in a Long-Period Pulsating Subdwarf B Star -- PG 1627+017
In the first spectroscopic campaign for a PG 1716 variable (or long-period
pulsating subdwarf B star), we succeeded in detecting velocity variations due
to g-mode pulsations at a level of 1.0-1.5 km/s.The observations were obtained
during 40 nights on 2-m class telescopes in Arizona, South Africa,and
Australia. The target,PG1627+017, is one of the brightest and largest amplitude
stars in its class.It is also the visible component of a post-common envelope
binary.Our final radial velocity data set includes 84 hours of time-series
spectroscopy over a time baseline of 53 days. Our derived radial velocity
amplitude spectrum, after subtracting the orbital motion, shows three potential
pulsational modes 3-4 sigma above the mean noise level, at 7201.0s,7014.6s and
7037.3s.Only one of the features is statistically likely to be real,but all
three are tantalizingly close to, or a one day alias of, the three strongest
periodicities found in the concurrent photometric campaign. We further
attempted to detect pulsational variations in the Balmer line amplitudes. The
single detected periodicity of 7209 s, although weak, is consistent with
theoretical expectations as a function of wavelength.Furthermore, it allows us
to rule out a degree index of l= 3 or l= 5 for that mode. Given the extreme
weakness of g-mode pulsations in these stars,we conclude that anything beyond
simply detecting their presence will require larger telescopes,higher
efficiency spectral monitoring over longer time baselines,improved longitude
coverage, and increased radial velocity precision.Comment: 39 pages, 9 figures, 4 tables, ApJ accepted. See postscript for full
abtrac
Elementary Forms of the Metaphorical Life : Tropes at Work in Durkheim’s Theory of the Religious
Peer reviewedPostprin
Oscillation frequencies and mode lifetimes in alpha Centauri A
We analyse our recently-published velocity measurements of alpha Cen A
(Butler et al. 2004). After adjusting the weights on a night-by-night basis in
order to optimize the window function to minimize sidelobes, we extract 42
oscillation frequencies with l=0 to 3 and measure the large and small frequency
separations. We give fitted relations to these frequencies that can be compared
with theoretical models and conclude that the observed scatter about these fits
is due to the finite lifetimes of the oscillation modes. We estimate the mode
lifetimes to be 1-2 d, substantially shorter than in the Sun.Comment: Accepted by Ap
Particulate matter concentrations in residences: an intervention study evaluating stand‐alone filters and air conditioners
This study, a randomized controlled trial, evaluated the effectiveness of free‐standing air filters and window air conditioners (ACs) in 126 low‐income households of children with asthma. Households were randomized into a control group, a group receiving a free‐standing HEPA filter placed in the child’s sleeping area, and a group receiving the filter and a window‐mounted AC. Indoor air quality (IAQ) was monitored for week‐long periods over three to four seasons. High concentrations of particulate matter (PM) and carbon dioxide were frequently seen. When IAQ was monitored, filters reduced PM levels in the child’s bedroom by an average of 50%. Filter use varied greatly among households and declined over time, for example, during weeks when pollutants were monitored, filter use was initially high, averaging 84 ± 27%, but dropped to 63 ± 33% in subsequent seasons. In months when households were not visited, use averaged only 34 ± 30%. Filter effectiveness did not vary in homes with central or room ACs. The study shows that measurements over multiple seasons are needed to characterize air quality and filter performance. The effectiveness of interventions using free‐standing air filters depends on occupant behavior, and strategies to ensure filter use should be an integral part of interventions. Practical Implications Environmental tobacco smoke (ETS) increased particulate matter (PM) levels by about 14 μg/m 3 and was often detected using ETS‐specific tracers despite restrictions on smoking in the house as reported on questionnaires administered to caregivers. PM concentrations depended on season, filter usage, relative humidity, air exchange ratios, number of children, outdoor PM levels, sweeping/dusting, and presence of a central air conditioner (AC). Free‐standing air filters can be an effective intervention that provides substantial reductions in PM concentrations if the filters are used. However, filter use was variable across the study population and declined over the study duration, and thus strategies are needed to encourage and maintain use of filters. The variability in filter use suggests that exposure misclassification is a potential problem in intervention studies using filters. The installation of a room AC in the bedroom, intended to limit air exchange ratios, along with an air filter, did not lower PM levels more than the filter alone.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91183/1/j.1600-0668.2011.00761.x.pd
Substellar companions and the formation of hot subdwarf stars
"Copyright 2011 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics."We give a brief review over the observational evidence for close substellar companions to hot subdwarf stars. The formation of these core helium-burning objects requires huge mass loss of their red giant progenitors. It has been suggested that besides stellar companions substellar objects in close orbits may be able to trigger this mass loss. Such objects can be easily detected around hot subdwarf stars by medium or high resolution spectroscopy with an RV accuracy at the km s(-1)-level. Eclipsing systems of Vir type stick out of transit surveys because of their characteristic light curves. The best evidence that substellar objects in close orbits around sdBs exist and that they are able to trigger the required mass loss is provided by the eclipsing system SDSS J0820+0008, which was found in the course of the MUCHFUSS project. Furthermore, several candidate systems have been discovered.Final Accepted Versio
Analysis and Evaluation of the Dynamic Performance of SMA Actuators for Prosthetic Hand Design
The analysis of facial beauty: an emerging area of research in pattern analysis
Much research presented recently supports the idea that the human perception of attractiveness is data-driven and largely irrespective of the perceiver. This suggests using pattern analysis techniques for beauty analysis. Several scientific papers on this subject are appearing in image processing, computer vision and pattern analysis contexts, or use techniques of these areas. In this paper, we will survey the recent studies on automatic analysis of facial beauty, and discuss research lines and practical application
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