A CORAVEL radial-velocity monitoring of S stars: symbiotic activity vs. orbital separation

Orbital elements are presented for the Tc-poor S stars HR 363 (= HD 7351) and HD 191226. With an orbital period of 4592 d (=12.6 y), HR 363 has the longest period known among S stars, and yet it is a strong X-ray source. Its X-ray flux is similar to that of HD 35155, an S star with one of the shortest orbital periods (640 d). This surprising result is put in perspective with other diagnostics of binary interaction observed in binary S stars. They reveal that there is no correlation between the level of binary interaction and the orbital period. This situation may be accounted for if the wind mass-loss rate from the giant is the principal factor controlling the activity level in these (detached) systems, via a stream of matter funneled through the inner Lagragian point.Comment: Astronomy & Astrophysics Supplements, 6 pages, 2 figures, 4 tables (LaTeX A&A). Also available at: http://obswww.unige.ch/~udry/cine/barium/barium.htm

Binaries among Ap and Am stars

The results of long-term surveys of radial velocities of cool Ap and Am stars are presented. There are two samples, one of about 100 Ap stars and the other of 86 Am stars. Both have been observed with the CORAVEL scanner from Observatoire de Haute-Provence (CNRS), France. The conspicuous lack of short-period binaries among cool Ap stars seems confirmed, although this may be the result of an observational bias; one system has a period as short as 1.6 days. A dozen new orbits could be determined, including that of one SB2 system. Considering the mass functions of 68 binaries from the literature and from our work, we conclude that the distribution of the mass ratios is the same for the Bp-Ap stars than for normal G dwarfs. Among the Am stars, we found 52 binaries, i.e. 60%; an orbit could be computed for 29 of them. Among these 29, there are 7 SB2 systems, one triple and one quadruple system. The 21 stars with an apparently constant radial velocity may show up later as long-period binaries with a high eccentricity. The mass functions of the SB1 systems are compatible with cool main-sequence companions, also suggested by ongoing spectral observations.Comment: 5 pages, 2 figures, to appear in: Proc. of the 26th workshop of the European Working Group on CP stars, Contrib. Astr. Obs. Skalnate Pleso Vol. 27, No

Group Analysis of Self-organizing Maps based on Functional MRI using Restricted Frechet Means

Studies of functional MRI data are increasingly concerned with the estimation of differences in spatio-temporal networks across groups of subjects or experimental conditions. Unsupervised clustering and independent component analysis (ICA) have been used to identify such spatio-temporal networks. While these approaches have been useful for estimating these networks at the subject-level, comparisons over groups or experimental conditions require further methodological development. In this paper, we tackle this problem by showing how self-organizing maps (SOMs) can be compared within a Frechean inferential framework. Here, we summarize the mean SOM in each group as a Frechet mean with respect to a metric on the space of SOMs. We consider the use of different metrics, and introduce two extensions of the classical sum of minimum distance (SMD) between two SOMs, which take into account the spatio-temporal pattern of the fMRI data. The validity of these methods is illustrated on synthetic data. Through these simulations, we show that the three metrics of interest behave as expected, in the sense that the ones capturing temporal, spatial and spatio-temporal aspects of the SOMs are more likely to reach significance under simulated scenarios characterized by temporal, spatial and spatio-temporal differences, respectively. In addition, a re-analysis of a classical experiment on visually-triggered emotions demonstrates the usefulness of this methodology. In this study, the multivariate functional patterns typical of the subjects exposed to pleasant and unpleasant stimuli are found to be more similar than the ones of the subjects exposed to emotionally neutral stimuli. Taken together, these results indicate that our proposed methods can cast new light on existing data by adopting a global analytical perspective on functional MRI paradigms.Comment: 23 pages, 5 figures, 4 tables. Submitted to Neuroimag

Contribution to the search for binaries among Am stars — V. Orbital elements of eight short-period spectroscopic binaries

We present the results of a radial-velocity study of eight Am stars (HD 341, 55822, 61250, 67317, 93991, 162950, 224890 and 225137) observed at Observatoire de Haute-Provence with the CORAVEL instrument. We find that these systems are single-line spectroscopic binaries whose orbital elements are determined for the first tim

Air Filtration in HVAC Systems

The Guidebook presents the theory of air filtration with some basic principles of the physics of pollutants and their effects on indoor quality. The main focus is on practical design, installation and operation of filters in air handling systems. It is intended for the use of designers, manufacturers, installers, and building owners. With its theory, practical solutions and illustrations it is also an excellent textbook for the vocational training of various experts in building services engineering

Contribution to the search for binaries among Am stars - III. HD 7119: a double-lined spectroscopic binary and a triple system

Radial velocity observations of HD 7119 with the CORAVEL instrument at Observatoire de Haute-Provence are reported. Known as an Amδδ Del metallic-line star, HD 7119 was included in our spectroscopic survey of Am-type stars, the purpose of which was to determine the frequency of binaries in this stellar family. This object is found to be a double-lined spectroscopic binary with a variable value of V0, the systematic velocity of the centre of gravity of the pair. The variation of this parameter is interpreted in terms of the orbital motion of an unseen third body with a much longer period. The orbital elements were derived for both the short- and the long-period orbits. These orbits can be considered to be well determined since these observations were performed on a regular basis over the 1992-1998 period, covering more than 320 orbital cycles for the short-period (P= 6.76 d) and 1.3 cycle for the long-period orbit (P∼ 1700 d). As deduced from the ratio of the correlation dip areas, the magnitude difference of the components of the short-period system is 0.7 mag. Combined with the Hipparcos data, this value leads to visual absolute magnitudes of 0.5 and 1.2 for the primary and secondary components, respectively. Such magnitudes are consistent with evolved δ Del-type stars. The third body could be a cool dwarf star with a minimum mass of 0.5 M⊙, located at ∼ 0.016 arcsec of the main system. Consequently, it cannot be the visual companion detected by Couteau with a separation of 3.35 arcsec. If this latter visual component were a physical component (rather than an optical one), HD 7119 would be a quadruple syste

Multiplicity among peculiar A stars I. The Ap stars HD 8441 and HD 137909, and the Am stars HD 43478 and HD 96391

We present the first results of a radial-velocity survey of cool Ap and Am stars. HD 8441 is not only a double system with P = 106.357 days, but is a triple one, the third companion having an orbital period larger than 5000 days. Improved orbital elements are given for the classical Ap star HD 137909 = beta CrB by combining our radial velocities with published ones. We yield new orbital elements of the two Am, SB2 binaries HD 43478 and HD 96391. Good estimates of the individual masses of the components of HD 43478 can be given thanks to the eclipses of this system, for which an approximate photometric solution is also proposed.Comment: 10 pages, 10 figures, accepted for publication in A&A

A Strategy for Identifying the Grid Stars for the Space Interferometry Mission (SIM)

We present a strategy to identify several thousand stars that are astrometrically stable at the micro-arcsecond level for use in the SIM (Space Interferometry Mission) astrometric grid. The requirements on the grid stars make this a rather challenging task. Taking a variety of considerations into account we argue for K giants as the best type of stars for the grid, mainly because they can be located at much larger distances than any other type of star due to their intrinsic brightness. We show that it is possible to identify suitable candidate grid K giants from existing astrometric catalogs. However, double stars have to be eliminated from these candidate grid samples, since they generally produce much larger astrometric jitter than tolerable for the grid. The most efficient way to achieve this is probably by means of a radial velocity survey. To demonstrate the feasibility of this approach, we repeatedly measured the radial velocities for a pre-selected sample of 86 nearby Hipparcos K giants with precisions of 5-8 m/s. The distribution of the intrinsic radial velocity variations for the bona-fide single K giants shows a maximum around 20 m/s, which is small enough not to severely affect the identification of stellar companions around other K giants. We use the results of our observations as input parameters for Monte-Carlo simulations on the possible design of a radial velocity survey of all grid stars. Our favored scenario would result in a grid which consists to 68% of true single stars and to 32% of double or multiple stars with periods mostly larger than 200 years, but only 3.6% of all grid stars would display astrometric jitter larger than 1 microarcsecond. This contamination level is probably tolerable.Comment: LaTeX, 21 pages, 8 figures, accepted by PASP (February 2001 issue). Also available at http://beehive.ucsd.edu/ftp/pub/grid/kgiants.htm

An ant colony-based semi-supervised approach for learning classification rules

Semi-supervised learning methods create models from a few labeled instances and a great number of unlabeled instances. They appear as a good option in scenarios where there is a lot of unlabeled data and the process of labeling instances is expensive, such as those where most Web applications stand. This paper proposes a semi-supervised self-training algorithm called Ant-Labeler. Self-training algorithms take advantage of supervised learning algorithms to iteratively learn a model from the labeled instances and then use this model to classify unlabeled instances. The instances that receive labels with high confidence are moved from the unlabeled to the labeled set, and this process is repeated until a stopping criteria is met, such as labeling all unlabeled instances. Ant-Labeler uses an ACO algorithm as the supervised learning method in the self-training procedure to generate interpretable rule-based models—used as an ensemble to ensure accurate predictions. The pheromone matrix is reused across different executions of the ACO algorithm to avoid rebuilding the models from scratch every time the labeled set is updated. Results showed that the proposed algorithm obtains better predictive accuracy than three state-of-the-art algorithms in roughly half of the datasets on which it was tested, and the smaller the number of labeled instances, the better the Ant-Labeler performance

Multiplicity among chemically peculiar stars II. Cool magnetic Ap stars

We present new orbits for sixteen Ap spectroscopic binaries, four of which might in fact be Am stars, and give their orbital elements. Four of them are SB2 systems: HD 5550, HD 22128, HD 56495 and HD 98088. The twelve other stars are : HD 9996, HD 12288, HD 40711, HD 54908, HD 65339, HD 73709, HD 105680, HD 138426, HD 184471, HD 188854, HD 200405 and HD 216533. Rough estimates of the individual masses of the components of HD 65339 (53 Cam) are given, combining our radial velocities with the results of speckle interferometry and with Hipparcos parallaxes. Considering the mass functions of 74 spectroscopic binaries from this work and from the literature, we conclude that the distribution of the mass ratio is the same for cool Ap stars as for normal G dwarfs. Therefore, the only differences between binaries with normal stars and those hosting an Ap star lie in the period distribution: except for the case of HD 200405, all orbital periods are longer than (or equal to) 3 days. A consequence of this peculiar distribution is a deficit of null eccentricities. There is no indication that the secondary has a special nature, like e.g. a white dwarf.Comment: 31 pages, 15 figures, A&A accepte