Unconstrained Astrometric Orbits for Hipparcos Stars with Stochastic Solutions

A considerable number of astrometric binaries whose positions on the sky do not obey the standard model of mean position, parallax and linear proper motion, were observed by the Hipparcos satellite. Some of them remain non-discovered, and their observational data have not been properly processed with the more adequate astrometric model that includes nonlinear orbital motion. We develop an automated algorithm based on "genetic optimization", to solve the orbital fitting problem with no prior information about the orbital elements is available (from, e.g., spectroscopic data or radial velocity monitoring). We test this method on Hipparcos stars with known orbital solutions in the catalog, and further apply it to stars with stochastic solutions, which may be unresolved binaries. At a confidence level of 99%, orbital fits are obtained for 65 stars, most of which have not been known as binary. A few of the new probable binaries with A-type primaries with periods 444-2015 d are chemically peculiar stars, including Ap and \lambda Boo type. The anomalous spectra of these stars are explained as admixture of the light from the unresolved, sufficiently bright and massive companions. We estimate the apparent orbits of four stars which have been identified as members of the 300 Myr-old UMa kinematic group. Another four new nearby binaries may include low-mass M-type or brown dwarf companions. Similar astrometric models and algorithms can be used for binary stars and planet hosts observed by SIM PlanetQuest and Gaia

The case for reshoring and nearshoring as a sustainability enhancer - perspectives from the textile industry

Sustainability awareness has increased worldwide, but implementation is faltering. The objective of the study is to find out if nearshoring is being used by textile companies to improve their sustainability performance. Moreover, the study aims at understanding the willingness of customers to pay more for nearshored products. To gain better insights four expert interviews were conducted and a questionnaire was filled out by 203 people. Findings resulting from the research indicate that nearshoring has no clear influence on sustainability performance. Furthermore, even customers who are aware of sustainability are not willing to spend significantly more for a sustainably produced T-shirt

HIPPARCOS Astrometric Orbit and Evolutionary Status of HR 6046

The previously known, 6-yr spectroscopic binary HR 6046 has been speculated in the past to contain a compact object as the secondary. A recent study has re-determined the orbit with great accuracy, and shown that the companion is an evolved but otherwise normal star of nearly identical mass as the primary, which is also a giant. The binary motion was detected by the Hipparcos mission but was not properly accounted for in the published astrometric solution. Here we use the Hipparcos intermediate data in combination with the spectroscopic results to revise that solution and establish the orbital inclination angle for the first time, and with it the absolute masses M(A) = 1.38 [-0.03,+0.09] M(Sun) and M(B) = 1.36 [-0.02,+0.07] M(Sun). Aided by other constraints, we investigate the evolutionary status and confirm that the primary star is approaching the tip of the red-giant branch, while the secondary is beginning its first ascent.Comment: To appear in The Astronomical Journal. 8 pages including tables and figures, in emulateapj forma

Projet de mise en oeuvre d'un équipement d'étude et de surveillance sur le volcan Lombenben (île d'Aoba-République du Vanuatu) = Proposal for the installation of monitoring equipment on the volcano Lombenben (Ambae island, Republic of Vanuatu)

Ce rapport rassemble les principales informations qui ont justifiées la demande de mise sous surveillance de la zone sommitale du volcan Lombenben sur l'île d'Aoba (environ 10 000 habitants). Il fait état de quelques données récentes et décrit l'ensemble des travaux qui seront conduits dans les prochains mois. (Résumé d'auteur

Analysis of the eclipsing binaries in the LMC discovered by OGLE: Period distribution and frequency of the short-period binaries

We review the results of our analysis of the OGLE LMC eclipsing binaries (Mazeh, Tamuz & North 2006), using EBAS -- Eclipsing Binary Automated Solver, an automated algorithm to fit lightcurves of eclipsing binaries (Tamuz, Mazeh & North 2006). After being corrected for observational selection effects, the set of detected eclipsing binaries yielded the period distribution and the frequency of all LMC short-period binaries, and not just the eclipsing systems. Somewhat surprisingly, the period distribution is consistent with a flat distribution in log P between 2 and 10 days. The total number of binaries with periods shorter than 10 days in the LMC was estimated to be about 5000. This figure led us to suggest that (0.7 +- 0.4)% of the main-sequence A- and B-type stars are found in binaries with periods shorter than 10 days. This frequency is substantially smaller than the fraction of binaries found by small Galactic radial-velocity surveys of B stars.Comment: 6 pages, 2 figures, submitted to Conference Proceedings of IAU Symp. 24

Present teaching stories as re-membering the humanities

he ways in which Humanities scholars talk about teaching tell something about how we interact with the past of our own discipline as well as anticipate our students’ futures. In this we express collective memories as truths of learning and teaching. As cultural artifacts of our present, such stories are worthy of excavation for what they imply about ourselves as well as messages they pass onto our successors. This paper outlines “collective re-membering” as one way to understand these stories, particularly as they present in qualitative interviews commonly being used to research higher education practice in the Humanities. It defines such collective re-membering through an interweaving of Halbwachs, Ricoeur, Wertsch and Bakhtin. It proposes that a dialogic reading between this understanding of collective re-membering and qualitative data-sets enables us to both access our discursive tendencies within the Humanities and understand the impact they might have on student engagement with our disciplines, noting that when discussing learning and teaching, we engage in collectively influenced myth-making and hagiography. The paper finishes by positing that the Humanities need to change their orientation from generating myths and pious teaching sagas towards the complex and ultimately more intellectually satisfying, articulation of learning and teaching parables

On the derivation of radial velocities of SB2 components: a "CCF vs TODCOR" comparison

The radial velocity (RV) of a single star is easily obtained from cross-correlation of the spectrum with a template, but the treatment of double-lined spectroscopic binaries (SB2s) is more difficult. Two different approaches were applied to a set of SB2s: the fit of the cross-correlation function with two normal distributions, and the cross-correlation with two templates, derived with the TODCOR code. It appears that the minimum masses obtained through the two methods are sometimes rather different, although their estimated uncertainties are roughly equal. Moreover, both methods induce a shift in the zero point of the secondary RVs, but it is less pronounced for TODCOR. All-in-all the comparison between the two methods is in favour of TODCOR.Comment: 5 pages, 4 figures, SF2A Conference 201

The Galactic disk mass-budget : II. Brown dwarf mass-function and density

In this paper, we extend the calculations conducted previously in the stellar regime to determine the brown dwarf IMF in the Galactic disk. We perform Monte Carlo calculations taking into account the brown dwarf formation rate, spatial distribution and binary fraction. Comparison with existing surveys seems to exclude a power-law MF as steep as the one determined in the stellar regime below 1 \msol and tends to favor a more flatish behaviour. Comparison with methane-dwarf detections tends to favor an eventually decreasing form like the lognormal or the more general exponential distributions determined in the previous paper. We calculate predicting brown dwarf counts in near-infrared color diagrams and brown dwarf discovery functions. These calculations yield the presently most accurate determination of the brown dwarf census in the Galactic disk. The brown dwarf number density is comparable to the stellar one, $n_{BD}\simeq n_\star\simeq 0.1$ pc$^{-3}$. The corresponding brown dwarf mass density, however, represents only about 10% of the stellar contribution, i.e. \rho_{BD}\simle 5.0\times 10^{-3} \mvol. Adding up the local stellar density determined previously yields the density of star-like objects, stars and brown dwarfs, in the solar neighborhood \rho_\odot \approx 5.0\times 10^{-2} \mvol.Comment: 39 pages, Latex file, uses aasms4.sty, to be published in ApJ, corrected version with correct figure

A possible dividing line between massive planets and brown-dwarf companions

Brown dwarfs are intermediate objects between planets and stars. The lower end of the brown-dwarf mass range overlaps with the one of massive planets and therefore the distinction between planets and brown-dwarf companions may require to trace the individual formation process. We present results on new potential brown-dwarf companions of Sun-like stars, which were discovered using CORALIE radial-velocity measurements. By combining the spectroscopic orbits and Hipparcos astrometric measurements, we have determined the orbit inclinations and therefore the companion masses for many of these systems. This has revealed a mass range between 25 and 45 Jupiter masses almost void of objects, suggesting a possible dividing line between massive planets and sub-stellar companions.Comment: 4 pages, 3 figures, submitted to IAUS 276 conference proceeding