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51.
T. Pribulla S.M. Rucinski D.W. Latham S.N. Quinn M. Siwak J.M. Matthews R. Kuschnig J.F. Rowe D.B. Guenther A.F.J. Moffat D. Sasselov G.A.H. Walker W.W. Weiss 《Astronomische Nachrichten》2010,331(4):397-411
Sixteen new eclipsing binaries have been discovered by the MOST satellite among guide stars used to point its telescope in various fields. Several previously known eclipsing binaries were also observed by MOST with unprecedented quality. Among the objects we discuss in more detail are short‐period eclipsing binaries with eccentric orbits in young open clusters: V578 Mon in NGC 2244 and HD 47934 in NGC 2264. Long nearly‐continuous photometric runs made it possible to discover three long‐period eclipsing binaries with orbits seen almost edge‐on: HD 45972 with P = 28.1 days and two systems (GSC 154 1247 and GSC 2141 526) with P > 25 days. The high precision of the satellite data led to discoveries of binaries with very shallow eclipses (e.g., HD 46180 with A = 0.016 mag, and HD 47934 with A = 0.025 mag). Ground‐based spectroscopy to support the space‐based photometry was used to refine the models of several of the systems (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
52.
Ian Moffat Lynley A. Wallis Mark W. Hounslow Katrina Niland Kate Domett George Trevorrow 《Geoarchaeology》2010,25(5):645-665
Geophysical techniques have been widely employed for the noninvasive location of burial sites in archaeological and forensic investigations. This approach has met with varying degrees of success, depending on factors such as equipment choice, survey methodology, burial type, and geological setting. This paper reports the results of a multitechnique geophysical survey carried out immediately prior to the salvage excavation of two Indigenous burials from an eolian dune in coastal South Australia. Ground‐penetrating radar was not successful in defining the location of the burials owing to the disturbed nature of the local stratigraphy. Magnetic field intensity and apparent magnetic susceptibility surveys identified discrete anomalies that coincided with the location of skeletal material revealed during excavation, which we hypothesize to be due to burning or ochre use during funerary practices. Despite the spatial association of these features, subsequent laboratory analyses of the mineralogy and magnetic properties of sediments collected from the site failed to find a definite cause of the anomalies. Nevertheless, the association between them and the primary interment locations has implications for archaeological surveys carried out in the Australian coastal zone, as it highlights the potential of magnetic field intensity and apparent magnetic susceptibility geophysical techniques undertaken with a more refined survey methodology to afford a noninvasive, culturally appropriate means through which to detect Indigenous burials. This approach may prove particularly useful in areas with disturbed stratigraphy where ground‐penetrating radar is less effective. © 2010 Wiley Periodicals, Inc. 相似文献
53.
O. Schnurr † A. F. J. Moffat A. Villar-Sbaffi N. St-Louis N. I. Morrell 《Monthly notices of the Royal Astronomical Society》2009,395(2):823-836
We report the results of a spectroscopic and polarimetric study of the massive, hydrogen-rich WN6h stars R144 (HD 38282 = BAT99-118 = Brey 89) and R145 (HDE 269928 = BAT99-119 = Brey 90) in the Large Magellanic Cloud. Both stars have been suspected to be binaries by previous studies (R144: Schnurr et al.; R145: Moffat). We have combined radial-velocity (RV) data from these two studies with previously unpublished polarimetric data. For R145, we were able to establish, for the first time, an orbital period of 158.8 d, along with the full set of orbital parameters, including the inclination angle i , which was found to be i = 38°± 9° . By applying a modified version of the shift-and-add method developed by Demers et al., we were able to isolate the spectral signature of the very faint line companion star. With the RV amplitudes of both components in R145, we were thus able to estimate their absolute masses. We find minimum masses M WR sin3 i = 116 ± 33 M⊙ and M O sin3 i = 48 ± 20 M⊙ for the WR and the O component, respectively. Thus, if the low-inclination angle were correct, resulting absolute masses of the components would be at least 300 and 125 M⊙ , respectively. However, such high masses are not supported by brightness considerations when R145 is compared to systems with known very high masses such as NGC 3603-A1 or WR20a. An inclination angle close to 90° would remedy the situation, but is excluded by the currently available data. More and better data are thus required to firmly establish the nature of this puzzling, yet potentially very massive and important system. As to R144, however, the combined data sets are not sufficient to find any periodicity. 相似文献
54.
J. R. Brownstein J. W. Moffat 《Monthly notices of the Royal Astronomical Society》2006,367(2):527-540
We apply the modified acceleration law obtained from Einstein gravity coupled to a massive skew symmetric field, F μνλ , to the problem of explaining X-ray galaxy cluster masses without exotic dark matter. Utilizing X-ray observations to fit the gas mass profile and temperature profile of the hot intracluster medium (ICM) with King 'β-models', we show that the dynamical masses of the galaxy clusters resulting from our modified acceleration law fit the cluster gas masses for our sample of 106 clusters without the need of introducing a non-baryonic dark matter component. We are further able to show for our sample of 106 clusters that the distribution of gas in the ICM as a function of radial distance is well fitted by the dynamical mass distribution arising from our modified acceleration law without any additional dark matter component. In a previous work, we applied this theory to galaxy rotation curves and demonstrated good fits to our sample of 101 low surface brightness, high surface brightness and dwarf galaxies including 58 galaxies that were fitted photometrically with the single-parameter mass-to-light ratio ( M / L )stars . The results obtained there were qualitatively similar to those obtained using Milgrom's phenomenological Modified Newtonian Dynamics (MOND) model, although the determined galaxy masses were quantitatively different, and MOND does not show a return to Keplerian behaviour at extragalactic distances. The results obtained here are compared to those obtained using Milgrom's phenomenological MOND model which does not fit the X-ray galaxy cluster masses unless an auxiliary dark matter component is included. 相似文献
55.
BAT99-129 is a rare, short-period eclipsing Wolf-Rayet binary in the Large Magellanic Cloud. We present here medium-resolution NTT/EMMI spectra that allow us to disentangle the spectra of the two components and find the orbital parameters of the binary. We also present VLT/FORS1 spectra of this binary taken during the secondary eclipse, i.e. when the companion star passes in front of the Wolf-Rayet star. With these data we are able to extract, for the first time in absolute units for a WR + O binary, the sizes of the line emitting regions.Based on observations obtained at the La Silla and Paranal Observatories, European Southern Observatory (Chile). 相似文献
56.
Stanton numbers, mean temperature profiles, and turbulent heat flux profiles are presented for thermal boundary layers which develop over a uniformly rough surface downstream of steps in wall temperature. Artificially thickened hydrodynamic layers were employed in order to create large unheated starting lengths compared to boundary-layer thickness, where the unheated starting length is the distance between the temperature step and hydrodynamic boundary-layer origin. Kernel functions for Stanton number distributions with downstream distance are presented which agree with measurements even when the hydrodynamic layers are significantly thicker than thermal layers. Other effects of unheated starting lengths on rough-wall thermal boundary-layer behavior are described, including significant alterations in profiles of mean temperature and turbulent heat flux. Both change shape as the magnitude of the unheated starting length increases, even though logarithmic regions of temperature profiles in wall coordinates and turbulent Prandtl number distributions are largely unaffected by unheated starting-length effects. 相似文献