Dust and gas in W49A     

H. Buckley  D. Ward-Thompson 《Astrophysics and Space Science》1995,224(1-2):431-432

We have mapped the high-mass star-forming region W49A at 450, 800, and 1100 microns with the JCMT. Spectral index measurements suggest an increase in temperature towards the emission peaks, consistent with previous data. We derive the gas masses associated with the central and extended emission from each of the three components, and find a deficit of gas around W49SW. The mass found for the core of W49N is in good agreement with the value previously derived from C³⁴S (5-4) maps (Serabynet al., 1993), and similar morphologies are found in the line and continuum maps.  相似文献   

The component masses of the cataclysmic variable V347 Puppis     

T. D. Thoroughgood  V. S. Dhillon  D. Steeghs  C. A. Watson  D. A. H. Buckley  S. P. Littlefair  D. A. Smith  M. Still †  K. J. van der Heyden  B. Warner 《Monthly notices of the Royal Astronomical Society》2005,357(3):881-894

We present time-resolved spectroscopy and photometry of the double-lined eclipsing cataclysmic variable V347 Pup (=LB 1800). There is evidence of irradiation on the inner hemisphere of the secondary star, which we correct for using a model to give a secondary-star radial velocity of   K _R= 198 ± 5 km s⁻¹  . The rotational velocity of the secondary star in V347 Pup is found to be   v sin  i = 131 ± 5 km s⁻¹  and the system inclination is   i = 840 ± 23  . From these parameters we obtain masses of   M ₁= 0.63 ± 0.04 M_⊙  for the white dwarf primary and   M ₂= 0.52 ± 0.06 M_⊙  for the M0.5V secondary star, giving a mass ratio of   q = 0.83 ± 0.05  . On the basis of the component masses, and the spectral type and radius of the secondary star in V347 Pup, we find tentative evidence for an evolved companion. V347 Pup shows many of the characteristics of the SW Sex stars, exhibiting single-peaked emission lines, high-velocity S-wave components and phase-offsets in the radial velocity curve. We find spiral arms in the accretion disc of V347 Pup and measure the disc radius to be close to the maximum allowed in a pressureless disc.  相似文献   

Stokes imaging, Doppler mapping and Roche tomography of the AM Herculis system V834 Cen   总被引：1，自引：0，他引：1  

Stephen B. Potter  E. Romero-Colmenero  C. A. Watson  D. A. H. Buckley  A. Phillips 《Monthly notices of the Royal Astronomical Society》2004,348(1):316-324

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X-ray bright sources in the Chandra Small Magellanic Cloud Wing Survey – detection of two new pulsars     

K. E. McGowan  M. J. Coe  M. Schurch  V. A. McBride  J. L. Galache  W. R. T. Edge  R. H. D. Corbet  S. Laycock  A. Udalski  D. A. H. Buckley 《Monthly notices of the Royal Astronomical Society》2007,376(2):759-770

We investigate the X-ray and optical properties of a sample of X-ray bright sources from the Small Magellanic Cloud (SMC) Wing Survey. We have detected two new pulsars with pulse periods of 65.8 s (CXOU J010712.6−723533) and 700 s (CXOU J010206.6−714115), and present observations of two previously known pulsars RX J0057.3−7325 (SXP101) and SAX J0103.2−7209 (SXP348). Our analysis has led to three new optical identifications for the detected pulsars. We find long-term optical periods for two of the pulsars, CXOU J010206.6−714115 and SXP101, of 267 and 21.9 d, respectively. Spectral analysis of a subset of the sample shows that the pulsars have harder spectra than the other sources detected. By employing a quantile-based colour–colour analysis we are able to separate the detected pulsars from the rest of the sample. Using archival catalogues we have been able to identify counterparts for the majority of the sources in our sample. Combining this with our results from the temporal analysis of the Chandra data and archival optical data, the X-ray spectral analysis, and by determining the X-ray to optical flux ratios we present preliminary classifications for the sources. In addition to the four detected pulsars, our sample includes two candidate foreground stars, 12 probable active galactic nuclei, and five unclassified sources.  相似文献   

The Ebro Deep-Sea Fan system     

C. Hans Nelson  Andres Maldonado  Francis Coumes  Henri Got  Andre Manaco 《Geo-Marine Letters》1984,3(2-4):125-131

The Ebro Fan System consists of en echelon channel-levee complexes, 50×20 km in area and 200-m thick. A few strong reflectors in a generally transparent seismic facies identify the sand-rich channel floors and levee crests. Numerous continuous acoustic reflectors characterize overbank turbidites and hemipelagites that blanket abandoned channel-levee complexes. The interlobe areas between channel complexes fill with homogeneous mud and sand from mass flow and overbank deposition; these exhibit a transparent seismic character. The steep continental rise and sediment “drainage” of Valencia Trough at the end of the channel-levee complexes prevent the development of distributary channels and midfan lobe deposits. Margin setting represents fan and/or source area  相似文献   

On the experimental silicification of microorganisms. III. Implications of the preservation of the green prokaryotic alga prochloron and other coccoids for interpretation of the microbial fossil record     

Susan Francis  Elso S. Barghoorn  Lynn Margulis 《Precambrian Research》1978,7(4):377-383

Evidence for Precambrian fossil eukaryotic microorganisms has been based on: (1) the presence of internal ‘spots’ which have been variously interpreted to be remains of nuclei or pyrenoids of photosynthetic plastids or other organelles; (2) tetrahedral tetrad arrangement of cells; (3) trilete scars interpreted to be indicative of meiotic division: (4) large cell diameters; and (5) putative mitotic cell divisions. These features have been reported in fossils preserved in Precambrian cherts. We have studied modern microbial mats, thought to be analogues of Precambrian fossil communities, and found they may be silicified by laboratory procedures. In microbial mats from Baja California we have found many ‘spot cells’ that we could identify as remains of cyanophytes. We have silicified the newly discovered large prokaryotic coccoid green alga Prochloron and have found that it, like many cyanophytes previously silicified, preserves its structure and maintains its initial dimensions. In laboratory-silicified prokaryotic organisms we have found that all of the above criteria, supposedly characteristic of eukaryotes, can be observed. We conclude that there is no compelling morphological evidence for fossil eukaryotic microbes from Precambrian cherts.  相似文献   

Determination of volatile fatty acid turnover rates in organic-rich marine sediments     

Francis J. Sansone  Christopher S. Martens 《Marine Chemistry》1981,10(3):233-247

Volatile fatty acid (VFA) apparent turnover rates in organic-rich marine sediments were determined by measuring whole sediment VFA concentration and the corresponding first-order reaction rate constants. In order to measure VFA concentrations, bulk wet sediment samples were basified, freeze-dried, extracted with methanol, derivatized to form methyl esters of the VFAs, and analyzed by packed-column gas chromatography using hexanoic acid as an internal standard. The detection limits for acetate, propionate, iso-butyrate and butyrate were 1.0, 0.4, 0.2 and 0.2 μmol l^?1_s, respectively, for 600 ml samples. Rate constants for acetate and propionate were determined by anaerobically incubating samples at in-situ temperatures with tracer levels of ¹⁴C-labelled VFAs. Metabolized label was recovered as CO₂, CH₄, cellular material, water-soluble material, and VFA (ether-soluble) fractions. Apparent turnover rates measured during summer and winter in anoxic Cape Lookout Bight, North Carolina (U.S.A.) sediments were in the range of 19–330 μmol l^?1_s h^?1 for acetate and 0.7–7.0 μmol l^?1_s h^?1 for propionate.  相似文献   

Frozen stakes: B. Mitchell International Institute for Environment and Development,London, 1983,135 pp     

Francis Auburn 《Marine Policy》1984,8(3):285-286

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HD 115781 and HD 116204—two RS CVn binaries     

R. F. Griffin  Francis C. Fekel 《Journal of Astrophysics and Astronomy》1988,9(4):213-224

HD 115781 and HD 116204 (BL CVn and BM CVn) are shown to be RS CVn binaries with periods near 20 days. HD 115781 is double-lined; the primary type is about K1III, while the secondary is probably a late-type subgiant. The masses of the two components are equal within observational error. There is substantial photometric variability with a period half the orbital period; it is attributed to ellipsoidal variation. HD 116204 is also of type K1III. It shows exceptionally strong Ca II H and K emission, together with an emission-line spectrum typical of RS CVn stars in theIUE ultraviolet region, but Hα is an absorption line. The secondary star in the HD 116204 system has not been detected. The primary shows photometric variations, presumably due to starspots, with a period 5 per cent longer than the orbital period.  相似文献   

How Necessary are Large-Scale Seismic Refraction Experiments?     

T. J. G. Francis 《Geophysical Journal International》1969,18(2):223-226

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