Radio observations of X-ray pulsators     

M. J. Coe  G. J. Gavin 《Astrophysics and Space Science》1983,89(1):169-172

A detailed search has been performed at 10.7 GHz for any pulsed radio emission from four X-ray pulsators (A0535+26, X Persei, AE Aquarii and H2252-035). The results obtained indicate no radio emission-pulsed or otherwise is present at a level of ≥ 50 mJy (two standard deviations upper limit). This value is considerably more sensitive than the previous studies carried out on these sources and presents problems in the understanding of compact, magnetised stellar objects.  相似文献   

Optical studies of two Large Magellanic Cloud X-ray transients: RX J0544.1–7100 and RX J0520.5–6932     

M.J. Coe  I. Negueruela  D.A.H. Buckley  N.J. Haigh  S.G.T. Laycock 《Monthly notices of the Royal Astronomical Society》2001,324(3):623-627

We report observations that confirm the identities of the optical counterparts to the transient sources RX J0544.1–7100 and RX J0520.5–6932 . The counterparts are suggested to be B-type stars. Optical data from the observations carried out at ESO and SAAO, together with results from the OGLE data base, are presented. In addition, X-ray data from the RXTE All-Sky Monitor are investigated for long-term periodicities. A strong suggestion for a binary period of 24.4 d is seen in RX J0520.5–6932 from the OGLE data.  相似文献   

An estimate of the supernova kick velocities for high-mass X-ray binaries in the Small Magellanic Cloud     

M. J. Coe 《Monthly notices of the Royal Astronomical Society》2005,358(4):1379-1382

This work investigates the possible supernova kick velocities imposed on high-mass X-ray binary (HMXB) systems in the Small Magellanic Cloud. Comparisons are made between the location of such systems and the locations of young stellar clusters on the premise that these may represent the birthplace of many of these systems. Measurements of the separation of clusters and HMXBs, and an estimate of the typical lifetimes of these systems, lead to a minimum average space velocity of 30 km s⁻¹. This value is compared to theoretical estimates.  相似文献   

Regional landslide-hazard assessment for Seattle, Washington, USA   总被引：13，自引：6，他引：13  

Rex L. Baum  Jeffery A. Coe  Jonathan W. Godt  Edwin L. Harp  Mark E. Reid  William Z. Savage  William H. Schulz  Dianne L. Brien  Alan F. Chleborad  Jonathan P. McKenna  John A. Michael 《Landslides》2005,2(4):266-279

Landslides are a widespread, frequent, and costly hazard in Seattle and the Puget Sound area of Washington State, USA. Shallow earth slides triggered by heavy rainfall are the most common type of landslide in the area; many transform into debris flows and cause significant property damage or disrupt transportation. Large rotational and translational slides, though less common, also cause serious property damage. The hundreds of landslides that occurred during the winters of 1995–96 and 1996–97 stimulated renewed interest by Puget Sound communities in identifying landslide-prone areas and taking actions to reduce future landslide losses. Informal partnerships between the U.S. Geological Survey (USGS), the City of Seattle, and private consultants are focusing on the problem of identifying and mapping areas of landslide hazard as well as characterizing temporal aspects of the hazard. We have developed GIS-based methods to map the probability of landslide occurrence as well as empirical rainfall thresholds and physically based methods to forecast times of landslide occurrence. Our methods for mapping landslide hazard zones began with field studies and physically based models to assess relative slope stability, including the effects of material properties, seasonal groundwater levels, and rainfall infiltration. We have analyzed the correlation between historic landslide occurrence and relative slope stability to map the degree of landslide hazard. The City of Seattle is using results of the USGS studies in storm preparedness planning for emergency access and response, planning for development or redevelopment of hillsides, and municipal facility planning and prioritization. Methods we have developed could be applied elsewhere to suit local needs and available data.  相似文献   

Comparison of the climate simulated by the CCM3 coupled to two different land-surface models   总被引：5，自引：0，他引：5  

C. Delire  S. Levis  G. Bonan  J. Foley  M. Coe  S. Vavrus 《Climate Dynamics》2002,19(8):657-669

We present results from a coupled atmosphere-biosphere model CCM3/IBIS (the Community Climate Model coupled to the Integrated BIosphere Simulator), which is designed to study the dynamic interactions between climate and vegetation and the global carbon cycle. We analyze the climate simulated by CCM3/IBIS with fixed vegetation conditions and we compare it to the climate simulated by the standard CCM3, which includes the LSM (land surface model) land-surface package. Important differences between the two models include simple parametrizations of lakes, wetlands and crops in CCM3/LSM not taken into account in CCM3/IBIS. CCM3/IBIS and CCM3/LSM share common biases (compared to observations) in the temperature field in boreal winter and in the precipitation field annually, making the atmospheric model the most probable cause of those biases. The models differ in the temperature field and surface energy balance in the Sahara annually and in the mid-to high latitudes from spring through fall. CCM3/IBIS simulates global annual air temperatures that are on average 1.7 °C higher than CCM3/LSM and 0.5 °C higher than the observed climatology. Differences in albedo and/or snow parametrization explain most of the Sahara and high-latitude temperature disagreement. Our sensitivity study with CCM3/LSM shows that the presence of lakes and wetlands in CCM3/LSM can account for about half of the difference in temperature in summer over the lake and wetland regions of the mid-latitudes. A second sensitivity study shows that higher surface roughness length in CCM3/IBIS can also explain part of the difference in summer surface temperature in the mid-latitudes. Surface roughness length affects the surface temperature through a feedback mechanism linking surface wind speed, planetary boundary layer height, low level cloudiness and radiation  相似文献   

Long-term variability of the Be/X-ray binary A 0535+26 – I. Optical and UV spectroscopy     

Clark  Tarasov  Steele  Coe  Roche  Shrader  Buckley  Larionov  Larionova  Lyuty  Zaitseva  Grunsfeld  Fabregat  & Parise 《Monthly notices of the Royal Astronomical Society》1998,294(1):165-176

The results of a 7-yr optical and UV spectroscopic study of the high-mass X-ray binary A 0535+26 are presented. It was found that throughout the period of the observations the line profile of Hα showed considerable variability. A correlation between the equivalent width of Hα and both V -band magnitude and ( B − V ) colour excess was observed, albeit with considerable scatter present in the data set. A giant X-ray flare in early 1994 was accompanied by a fading in optical and infrared photometric bands, and a reduction in the equivalent width of Hα. When the star was observed in 1994 September, it was found to have developed a double-peaked Hα profile, and further observations saw the V/R peak ratio vary cyclically, with a period of ∼1 yr. If this is identified as a global one-armed oscillation, it becomes the shortest period ever observed in a Be star. The accompanying photometric and spectroscopic observations provide a test of any theory seeking to describe the onset and behaviour of such a density wave.  相似文献   

The identification of the optical/IR counterpart to the ROSAT SMC X-ray transient RX J0117.6−7330     

Coe  Buckley  Charles  Southwell  & Stevens 《Monthly notices of the Royal Astronomical Society》1998,293(1):43-48

We report observations which identify the optical/IR counterpart to the ROSAT X-ray transient RX J0117.6−7330. The counterpart is suggested to be a B1–B2 star (luminosity class III–V) showing an IR excess and strong Balmer emission lines. The distance derived from reddening and systemic velocity measurements is consistent with the distance derived from X-ray measurements and puts the source in the Small Magellanic Cloud (SMC).  相似文献   

Long-term variability of the Be/X-ray binary EXO 2030+375     

P. Reig  J. B. Stevens  M. J. Coe  & J. Fabregat 《Monthly notices of the Royal Astronomical Society》1998,301(1):42-48

We present a multi-wavelength study of the Be/X-ray binary system EXO 2030+375. We report that the Be companion is currently in a low-activity phase as indicated by the notable decrease of the infrared and optical emission. If this trend continues the source will lose its circumstellar envelope. Infrared spectroscopy in the IJHK bands is presented for the first time, along with optical and X-ray observations. These infrared spectra agree with the optical companion being an early-type (B0) main-sequence star. When active EXO 2030+375 shows an X-ray outburst at each periastron passage of the neutron star. In addition to the maximum X-ray luminosity displayed at orbital phase ∼0.0, we find a smaller maximum in the light curve at phase ∼0.5. This second intensity peak may be explained if the velocity of the wind is lower than or comparable to the orbital velocity of the neutron star at apastron. We also comment on the relation between the optical/infrared behaviour and the X-ray emission and argue that the X-ray inactive period observed between 1993 August and 1996 April is a result of centrifugal inhibition of accretion of matter rather than a low-activity circumstellar disc.  相似文献   

Contrasting styles of Archaean crustal evolution in parts of southern West Greenland     

Kenneth Coe  Steve Robertson 《Journal of Geodynamics》1984,1(3-5)

Aspects of the crustal evolution of three areas in the Archaean block of southern West Greenland are compared and new Rb and Sr isotope data are presented for one of them (inner Godthåbsfjord). It is concluded that major differences resulted from variations in crustal thickness with the early Archaean Amîtsoq gneisses controlling later events.  相似文献   

Principal stress directions from a natural occurrence of stress-induced clinoenstatite     

B. R. Frost  R. S. Coe  F. P. Okamura 《Contributions to Mineralogy and Petrology》1978,67(2):119-126

Lamellae of clinoenstatite are common in enstatite grains in the high-grade ultramafic hornfelses around the Mount Stuart Batholith in the Central Cascades of Washington. Laboratory deformation experiments on enstatite have shown that shear stress on (100) planes parallel to [001] drastically promotes the formation of clinoenstatite. Petrofabric studies of a sample of the hornfels reveal a strong preferred orientation of clinoenstatite-bearing enstatite grains that is unrelated to the fabric of the complete set of enstatite grains. This preferred orientation is well explained by supposing that the clinoenstatite was produced by shearing due to N-S compression. Local and regional geological features are also consistent with N-S compression. These results suggest that there is considerable potential for the application of stress-induced clinoenstatite as a geopiezometer in rocks.Now with: Department of Geology, University of Wyoming, Laramie, WY 80271, USA  相似文献